Control Channel (CCH)

introduction

GSM system channel classification:

Cellular communication systems to transmission of different types of information, including business information and various control information, so you need to in physical channel arrangement of logical channel. These logical channel some used to call in stages, some are used for communication underway, also some for system operation of all time.

Logical channel is divided into business channel (TCH) and control channel (CCH) two kinds big.

Control channel (CCH) was used to transmit signaling information and short packet data channel.

classification

Control channel is divided into three categories:

Broadcast information

1) broadcast information (BCH) is a kind of "point-to-multipoint" single direction control channel, used for mobile station radio stations to all public information. Transmission is the content of the mobile station net and call set-up needed all kinds of information. Among them were divided into:

A, frequency correction channel (FCCH) : transmission for mobile station correction its working frequency information;

B, synchronous channels (SYCH) : transmission for mobile station synchronously and to base station identification of information;

C, radio control channel (BCCH) : transmission general information, used in mobile station to measure the signal strength and identify district mark etc.

Public control channel

2) public control channel (CCCH) is a kind of "point-to-multipoint" two-way control channel, its usage is the call succeeded stage, transmission link connection needed to control signaling and information. Among them were divided into:

A, paging channel (PACH) : transmission stations paging mobile platform of information;

B, random access channel (RACH) : mobile station application into the net, send request information to base station,

C, allow access channel (AGCH) : base station at the call succeeded begins, send to the mobile station distribution channel of special control signaling.

D, community radio channel (CBCH) : used for base station to village inside the mobile station broadcast news channels.

Special control channel

3) special control channel (DCCH) is a kind of "peer-to-peer" two-way control channel, its usage is the call in stages and in communication underway in the mobile station and base station transmitted between the necessary control information. Among them were divided into:

A, independent special control channel (SDCCH) : transmission mobile station and base station connection and channel allocation of signalling, Also carry call forwarding and short message information.

B, accompany channel (ACCH), can accompany SDCCH, also can accompany business channel (TCH), in other words, it is SDCCH coupled with a TCH or.

(1) slow accompany channel (SACCH) : in the mobile platform and base station transmission, cycle between certain information, such as power adjustment, frame adjustment and measurement data information; etc. SACCH is arranged in business channel and the relevant control channel to complex connecting mode transmit information. Arranged in business channel when, with SACCH/T says, arranged in control channel when, with SACCH/C, said SACCH often used in combination with SDCCH.

2 quickly with channel (FACCH) : for blitting executing user jian right and the handoff information. When used to halt the business information (4), FACCH insert the frame, but only in did not assign SDCCH will only use this control channels. This control channel transmission rate faster, occupy 4 each frame time, about 18.5 ms.

Community radio channel

(4) community radio channel (CBCH)

Community radio channel used to broadcast village short message bit/s it only downward direction, carrying village broadcast short message service (SMSCB) information, use the same SDCCH the same physical channel.  

Multicast

Multicast transfer: the sender and receiver between each realize point-to-multipoint network connections. If a sender while giving multiple recipients of transmission the same data, also need a copy of the same packets. It raises the data transmission efficiency. Reduce the backbone network appear congestion of possibilities.

A, IP network data transmission

Multicast technology is IP network data transmission in one of three ways, introduce IP multicast technology, before to IP network data transmission unicast and multicast and broadcast way to do a simple introduction:

Unicast transfer: the sender and receiver realizing each point-to-point network connections. If a sender while giving multiple recipients of the same data transmission, must also corresponding copying multiple copies of the same packets. If there is a lot of the same host hopes to get a packet, copy will lead to the sender burden is heavy, delay long, network congestion, To guarantee the quality of service should be increased to hardware and bandwidth.

Multicast transfer: the sender and receiver between each realize point-to-multipoint network connections. If a sender while giving multiple recipients of transmission the same data, also need a copy of the same packets. It raises the data transmission efficiency. Reduce the backbone network appear congestion of possibilities.

Broadcasting transmission: refers to the IP subnetting within packets, all in radio subnet internal host will receive these packets. Radio means network to subnet every hosts are delivered a packet, no matter whether the host to receive this packet. So broadcast use scope is very small, only in local subnet valid, by routers and network equipment control radio transmission.

Second, multicast related technologies

1, IP multicast technology system structure

Multicast protocols are divided into host - router between members relationship agreement and router - router between the multicast routing protocol. Group relationship agreement includes IGMP (Internet group management protocol). Multicast routing protocol is divided into domain of multicast routing protocols and domain between multicast routing protocol. Domain Multicast Routing protocols including PIM - SM (Protocol Independent Multicast - Sparse Mode), PIM - DM (Protocol Independent Multicast - Dense Mode), DVMRP (Distance Vector Protocol) such as Multicast ccna agreement, domain of Multicast Routing protocols including between MBGP (Multiprotocol BGP), MSDP (" Discovery Protocol) returned Multicast protocols. At the same time in order to effectively restrain multicast data on link layer diffusion, introduced IGMP Snooping, CGMP etc layer multicast protocols.

IGMP to establish and maintain the router straight segment of the group relation network information. Domain multicast routing protocol IGMP maintenance according to these multicast group relations information, the use of certain multicast routing algorithm tectonic multicast distribution of multicast tree on the packet. Domain of multicast routing protocols in between the autonomous domain has issued a multicast ability between the routing information and multicast source information for multicast data in domain between the forwarding.

2, the multicast IP address

Multicast IP address used to identify an IP multicast group. IANA (assigned by the authority) Internet address space allocated to the class D IP multicast, ranging from 224.0.0.0 to 239.255.255.255. Shown below (binary representation), IP multicast address top four are for 1110.

Octet in (1) eight group (2) eight group (3) eight group (4)

1110XXXX XXXXXXXX XXXXXXXX XXXXXXXX

Multicast group can be permanent can also be temporary. Multicast group address some of the distribution by the official, called the permanent multicast group. Permanent multicast group to remain the same is its IP address, group members of the composition can change. Permanent multicast group members of the quantity can be arbitrarily, can even to zero. Those not retained for permanent multicast group to use IP multicast address, can be temporary multicast group to use.

224.0.0.0 ~ 224.0.0.255 to reserve the multicast address (permanent group address), address 224.0.0.0 reserves don't do distribution, other address for routing protocol used; 224.0.1.0 ~ 238.255.255.255 for the multicast address users can (temporary group address), network-wide security effective; 239.0.0.0 ~ 239.255.255.255 for local management multicast addresses, only in the specific local scope effective. Common reserve the multicast address listed below:

224.0.0.0 benchmark address (reserves)

224.0.0.1 all host address

224.0.0.2 all multicast router's address

224.0.0.3 not allocation

224.0.0.4 Distance Vector DVMRP (Multicast ccna Protocol, Distance Vector of Multicast Routing Protocol) router

Shortest Path 224.0.0.5 ospf (Open First, Open Shortest Path is preferred) router

Dr Designated Router (224.0.0.6 ospf Designated Router),

224.0.0.7 st (Shared Tree, sharing Tree) router

224.0.0.8 st host

224.0.0.9 rip - 2 router

224.0.0.10 Eigrp (Gateway Protocol, Interior ccna to enhance Gateway Interior Routing lines Protocol) router 224.0.0.11 activities agent

224.0.0.12 DHCP server/relay agent

224.0.0.13 all pim (Protocol Independent Multicast, agreement irrelevant Multicast) router

224.0.0.14 RSVP (Protocol, Resource Reservation Resource reserve agreement) encapsulation

224.0.0.15 all CBT router

224.0.0.16 specified Bandwidth Management, Subnetwork SBM (subnet Bandwidth Management)

224.0.0.17 all SBMS

224.0.0.18 VRRP insgroupsto Router Protocol Redundancy, Virtual Router Redundancy Protocol)

3, group relationship protocol (IGMP)

IGMP protocol running on host and with mainframe directly connected multicast router, through this agreement between hosts told local router hope to join and accept a particular multicast group information, and at the same time router through this agreement periodically inquires the wlan a known group members are in active state (namely the network segment if there's still belong to a multicast group members), to achieve even network group relationship of collecting and maintenance.

There are three IGMPv1 IGMP version, by definition, RFC1112 gm now is, by definition IGMPv2 RFC2236. IGMPv3 is still a draft. IGMPv1 defined the basic group query and reporting process, IGMPv2 based on this added group quickly leave mechanism, IGMPv3 add's main function is to members can be specified to accept or designated don't accept certain multicast source message. Here introduced emphatically IGMPv2 agreement function.

IGMPv2 through inquires the device for election mechanism linking section election only inquires the device. Inquires cyclical send universal device group members relationship inquires query message, Machine to send report news to reply query. When wanting to join a multicast group, the host needn't wait inquires, active send a report news news. When leaving a multicast group, the machine to send leave group messaging, Received left group news, inquires the editor sent specific groups to determine whether all query news groups have left.

Through the above IGMP mechanism, the multicast router inside establish a list, including routers in the port of each port and corresponding subnet what are the group members. When a router to receive a group G data message, only to those who have G members of the port forwarding data message. As for data message on a router between how forwarding criterion by routing protocol decision, IGMP protocol is not responsible for.

4, network layer multicast relevant agreement

The network layer multicast relevant agreement includes IGMP Snooping, IGMP existent and CGMP agreement.

The realization of the IGMP Snooping mechanism is: switches through to the router protected reliably against detective host hair IGMP members report news way, forming group and the switch interface corresponding relationships, Switches according to the corresponding relationship will receive multicast packet only to have group interface.

IGMP existent IGMP Snooping function with the same but mechanism are motiva ted: IGMP Snooping just by the news of protected reliably against detective IGMP to obtain relevant information, and is the IGMP existent intercept the end-user IGMP request and relative processing, it can be transmitted to the upper router.

CGMP (Group Management Protocol) is Cisco Cisco based on client/server model development of private agreement, the CGMP, under the support of multicast router according to receiving notice IGMP packet switch which hosts when join a multicast Group and out by these information, switches use this turn published to determine what will multicast packet forwarding to interface. GMRP is host to Ethernet switches the standard protocol, it makes the multicast users can layer 2 switches on multicast members to register.

5 and multicast routing protocol (PIM SM) -

Numerous multicast routing protocol, and currently applied the most protocol is PIM - SM sparse model agreement irrelevant multicast. In SM domain and operation - PIM PIM - SM agreement router periodically send Hello message, to find the adjacency of PIM router, and in charge of multi-channel access network in a designated router (DR) election. Here, DR responsible for its direct link group towards multicast distribution root node direction send "add/pruning" the message, or will be connected directly multicast source data sent to multicast distribution tree.

Plait addresses

A kind of 0.0.0.0-127.255.255.255

Class B 128.0.0.0-191.255.255.255

Class C 192.0.0.0-223.255.255.255

D class 224.0.0.0-239.255.255.255

A, B, C IP packet forwarding based on destination IP address. D class (multicast addresses) packet forwarding based on source address.  

Eight popular sports fashionable personage preferred

Rational wisdom - the snooker

Suit a crowd: physical quality is not suitable for outdoor sports, the brain is physical more developed women.

Movement comment on

Wins in mind: the situation think too complex, will be hard-pressed snowed under opponent, YiGongWeiShou calmly, can jump out trap, attackers for attacking. The snooker cultivate your eyesight and balance.

Cool strength - - fencing

Suit a crowd: should be increased flexibility of both.in women.

Movement comment on

Aristocratic temperament is known as the "combat: classical ballet", in order to win, and with light mind, chocolate, and spirit beat opponent, is a wise movement. Fencing cultured salute to cultivate and reflect the female modesty generous demeanor. End, in-situ motionless, and with a sword to referee smartly. Referees announced after the game, you must use the hold sword hand to remove the protective interbedded in tress, hold sword arm armpit, use the hold sword hand shake hands with opponent greetings and salute to the audience.

Fighting fortitude - football

Suit a crowd: needs to foster team spirit, careful, everything would not actively women.

Movement comment on

Spiritual beauty: like in nature, running speed, cheetahs rhythm, dynamics, power and stretch the lines are give a person with beautiful enjoyment. In women with both strength and beauty, speed, beauty is spiritual beauty.

Vitality to spurt - tennis

Suit a crowd: always let own temperament and obstinate self-will of women.

Movement comment on

Brain: whether it serve or play ball, trying to intercept the ball the other party of the sky, is necessarily constant principle. This can earlier, make the other side open to the objection. Blindly, but in offense will not smooth, not loath also disadvantages offense. See what time should defense is not easy, and maintain a balanced is very important. Stadium so, and so does the workplace.

Ofs material bearing - riding

Suit a crowd: not good at communication, lack of flexibility of women.

Movement comment on

Teamwork: centaur between is a non utilitarian partnership. Horses naturally sensitive, at the first meeting, if you "took apple-polishing", but no one has to protect you! It was difficult to ensure that handsome riding clothes, riding boots, not female up the horse power. See riding clothes let a woman in handsome in coruscate gives romantic enchanting temperament, your fantasy world began from...

Free free and easy - swimming

Suit a crowd: xiuwaihuizhong, insight into the world of women.

Movement comment on

Relieve pressure: the more you make to the utmost the all power line, the greater the resistance, According to water power hard, speed can reach the maximum. Similar maternal living environment, let you have enough sense of security and release the pressure of calm.

Brave enterprising - to climb the mountain

Suit a crowd: the character cowardice, complacent and conservative, eager for women.

Movement comment on

Self-conquest: not to conquer mountain, but to conquer self. Climbing up more than your body, but you strong legs, a keen eye and strong arms and strong will. Enjoy every step of the upward, enjoy this optimism to self hints and guidelines.

Gentle and balanced -- yoga

Suit a crowd: slightly greed, fickleness, not too will listen to the voice within the women.

Movement comment on

Naturally: let the heart becomes "empty", let consciousness become simple, always need not importune and every movement only strengths, remaining is extension of consciousness. 

Small Tiptoe profit is great

Double foot Tiptoe method is combined touchdown, forcibly raise heels up, then relax, repeat 20 ~ 30 times. Although the method is simple, but fitness effect is good. On tiptoe, bilateral crus muscle contractions every time hind extruded blood volume, roughly equivalent to heart pulse discharge blood. So, when you chess, card-playing, and playing computer or long standstill, it is better to 1 hour to do 1 times Tiptoe movement, can make the lower limb blood backflow smoothly. Moreover, Tiptoe sports can also activities limbs and mind, eliminate long time brain concentration and suddenly stand and blacked out, mind feel dizzy problem.

In addition, void although be bagatelle, also cannot treat STH lightly. Men stood on tiptoe to urinate, then can have strong renal function, and can therefore joint achieve strong fine effect. Women sit squatted at the same time, the first toes and second toe forcibly touchdown, stand a stand, shaking out, also can have the kidney diuresis effect. If can do within a day on five or six times such Tiptoe pointed movement, continuous 1 ~ 6 months, can achieve very good strong pure and fitness function. At the same time. Can alleviate because of long standing and cause heel pain. If chronic prostatitis and prostatic hypertrophy, urinate Tiptoe also have urine chang feeling.

Want to say is Tiptoe to walk, is sufficient with mention completely with sufficient to walk, walk a hundred paces. Can exercise the flexor muscles. From the meridian perspective, but also benefits the unobstructed with three Yin meridians. Sufficient with walk is put up with sufficient become warped, walk, so is sufficient with practice crus the anterior extensor muscles, and do a hundred paces, can dredge with three Yang meridians. Both alternating can illnesses to the body. Of course, for old people should be pay attention to safety, lest stand instability and fall. Suffering from severe osteoporosis had better not do.

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PLD(programmable logic device)

PLD(programmable logic device) ：as a general PLD is integrated circuit production, his logic functions according to user to device programming to fix. General PLD integration high enough to satisfy the design general digital system needs. So you can from the designer by a digital system programming and "integrated" in a PLD, without having to go please chip manufacturer to design and manufacture special integrated circuit chips.

classification

Currently used PLD products mainly are: 1, field programmable logical array FPLA; 2, programmable logical array PAL, GAL 3, general array logic, 4, can erase programmable logic devices EPLD, 5 and the field reprogrammable array FPGA. One EPLD and FPGA integration is quite high. Sometimes make both device called high-density PLD.

Development course

Early programmable logic devices only programmable read-only CunZhuQi (PROM), ultraviolet ray can press except read-only CunZhuQi (an EPROM) and electricity can erase read-only CunZhuQi (EEPROM) 3 kinds. Due to the structure limits, they can only implement simple digital logic function.

Thereafter, the emergence of a class of structure slightly complex programmable chip, can programming logical device, it can finish all kinds of digital logic function. The typical PLD by an "and" door and a "or" gate arrays composed of any combinational logic can use "and a" expressions to describe or, so, with product and PLD can do a great deal of the form of combinational logic function. This one phase of products mainly include GAL PAL and. PAL by a programmable "and" plane and a fixed "or" planar formation, or through the gate outputs can be set to trigger selective hosting state. PAL devices are field programmable, its realization process has anti melt silk technology, an EPROM technology and EEPROM technology. And those structure is more flexible logic devices is programmable logical array (PLA), it can also by an "and" plane and a "or" plane composition, but the two plane connections is programmable. The plaaf device both field programmable, also have mask programmable. On the basis of PAL, and developed a GAL, such as general array logic GAL16V8, GAL22V10 etc. It adopted EEPROM process, realized the electricity can press except, electricity can rewrite, its output structure is programmable logic macro unit, so it has a strong design flexibility, so far, there are still many people use. These early PLD device of a common characteristic is can realize speed characteristics better logic functions, but its too simple structure also make they can only achieve smaller circuits. In order to make up for the defect, in 1980s and Altera Xilinx respectively introduced a similar to PAL structure of expandable CPLD and with standard gate array FPGA, they are similar with the system structure and logical unit that flexible, and integration is high and wide application scope, etc. These two kinds of devices compatible PLD and general gate arrays, can realize the advantages of large-scale circuit, programming is also very flexible. And the gate arrays, compared to other ASIC design and have them short development cycle, design and manufacture of low cost, development tools is advanced, the standard products without testing, stable quality and real-time on-line inspection etc, and therefore have been widely applied in product prototype design and product production (usually in 10,000 units under) among. Nearly all applications gate arrays, PLD and middle and small general digital integrated circuit occasions are applied FPGA and CPLD device.

composition

· a two-dimensional array logic brick, constitutes the core of the device consisting PLD logic.

· input/output block: connect logical pieces of interconnect resources.

· attachment resources: by all sorts of length of attachment, including hidden-lines composition have also some programmable connecting switch, they are used in logic brick, between the logic brick and input/output block the connection between the.

Virtual terminal (VT)

Virtual terminal (VT) is a kind of offer is similar to Internet Telnet agreement remote terminal simulation of the international organization for standardization (ISO) agreement. In a remote terminal users, can be in remote to run on a computer applications, as though they were sitting in front of the computer is same.

Virtual terminal is in a personal computer virtual a terminal and for this purpose writing software. Virtual terminal purpose is to achieve personal computers and users can with large computer connections. Generally required to connect large computer is IBM mainframe computer or so-called small-sized computer (past is often di taanach VAX).

Virtual terminal make personal computer users can directly use his personal computers with large computer contact, without the use of special terminal.

Through the virtual terminal software virtual terminal can also expand large computer standard terminal function, through the virtual terminal can not only will the data transfer on personal computers to large computers, and can also bring large computer data transfer to the personal computer, and the PC continue processing.

General large computer terminal is letters type of input and output interface, so a virtual terminal should have at least one can simulate such letters type (such as ASCII) input and output interface ability. The most common platform is the user surface. Image type To make the new, image type program can use the old letters type or no image type input and output capacity of program also need virtual terminal.

Modern large computer also internal use virtual terminal, so they can ask old and require terminal program pretend a terminal, but in fact it is a program's display turned to display adapters. For instance Linux and most other pc-based similar Unix operating system pretend to have six to ten such "virtual" of the terminal.

Letters program < - > virtual terminal < - > image display

Shells < - > xterm < - > X11

structure

Virtual terminal makes a letter type programs can be a graphical user interface and the user communication. Them so that the user can use cannot directly using image interface program (for example, because they haven't image when programming interface, or because the letters type interface is simpler). Virtual terminal to letters type program "pretended" give a letter terminals while to image interface "pretended" give a image type of program.

Working way

Virtual terminal to complete a terminal program task. But a virtual terminal is a common, in an operating system, the computer CPU run on ordinary procedure, rather than a stored in terminal read-only memory of, in the terminal CPU operation of the procedure. Virtual terminal analysis of a letter to type the program's output, convert it to image interface (such as X11) output.

The terminal window inside the keyboard input transfer to large computer with terminal connections trip, general this trip is a command-line interpreter. This journey think oneself is connected with a terminal, but in fact it is connected with a virtual terminal.

Three minutes fast motion exercise good relaxed

Talking about the fitness, maybe a lot of people are meet Lou difficult color, and doesn't like to exercise, but don't have the time. It seems to have is that most people don't exercise unified reason. So, we'll because work favour or not enough time, he really give up fitness, given up exercise? Can you have the more simple fitness method, let us a few minutes to take exercise? Answer is yes. A doctor recommended to us four 3 minutes by a white-collar men sport, application, feel the effect good insist, specially recommend to you.

Rub hand 3 minutes

First hands palm, rub each other until palm feel micro hot, then back rub each other, and finally fingers crossed, mutual rub. Hand the meridian intensive, often knead these meridians, can to its corresponding viscera have health care function.

The cold bath 3 minutes

Use cold water scrubbing body, can promote the whole body blood circulation, just wipe will feel very cold, but 5 minutes later will fever, I feel very comfortable, can prevent disease of heart head blood-vessel.

Bend over 3 minutes

Two feet and shoulder are the same as wide, and then gradually bow bend, hands touchdown, two seconds once, 1 minute 30 times. Beginning may little bend several times, increasing. The sport can increase of stress tolerance, cerebrovascular for troubled many people's migraine headaches, also have certain soothing effects.

Supine breathing 3 minutes

Relax supine on the bed, suck full breath, make the belly up, then slowly exhale, thus repeatedly. This movement is ok exercise body internal organs to vessels and nerves relieved and rhythmic movement. Helpful for xiaoshi phlegm, also be helpful for safe sleep.

Handstand: give viscera decompression

Handstand to human body it is a rebellious posture. On whole body all joints, organ under pressure to eliminate or decrease muscle relaxation, some part of the body, and blood accelerate flocked to the head. But because of the pain caused by various stand protect, and improve blood circulation, strengthen the viscera function, have flabby body fitness effect.

Remind:

1. Start can please help.

2. Really hard to finish do not force.

3. Note the hand don't hurt.

4. Cardiovascular disease patients is unfavorable, appear in case accident.

5. Because handstand will cause intraocular pressure, so, glaucoma, myopic, diabetes or retinal vascular disease patient careful travel. 

Zigbee(IEEE 802.15.4)

Zigbee is IEEE 802.15.4 agreement pronoun. According to this agreement and the technology is a kind of short, low power dissipation of wireless communication technology. The name comes from the character of dance, due to the bee bee bee) by (flying and "hum" (zig) shaking wings "dancing" to and companion transfer pollen location position information, i.e. bees rely on such form a group of communication networks. Its characteristic is close, low complexity, self-organization, low power consumption, low data rate and low cost. Mainly suitable for automatic control and remote control field, may be inline with all sorts of equipment. In short, ZigBee is a cheap, low power close distance, wireless network communication technologies.

Zigbee origins

Zigbee, it is similar with bluetooth. Is a kind of burgeoning short-range wireless technology

This idea was put forward in 802.15 workgroup IEEE, so TG4 working group was established, and to establish a standard IEEE 802.15.4.

In 2002, was established. Zigbee Alliance

In 2004, zigbee V1.0 born. It is zigbee first norms. But due to launch hasty, there exist some mistake.

In 2006, launched in 2006. Zigbee, comparatively perfect

The end of 2007, zigbee PRO launched

Zigbee rock-bottom technology based on 802.15.4. IEEE

The physical and MAC layer directly cited IEEE 802.15.4

In the use process bluetooth technology, people found bluetooth technology although there are many advantages, but there are still many defects. For industrial, family automation control and industrial telemetry remote sector, bluetooth technology appear too complex, power, closer, networking too small, etc., and the industrial automation of wireless data communication needs is more and more intense, and, for industrial field, this kind of wireless data transmission must have been highly reliable, and can resist industrial field of various electromagnetic interference. Therefore, after people long-term endeavors, Zigbee agreement formally published in 2003. In addition, Zigbee used in it before the studied facing family network communication protocol Home RF Lite.

Long-term since, low price and low bit rate, short, low power wireless communication market have existed. Since the Bluetooth after appearing, ever let industrial control, household automatic control, toy manufacturers such as providers caper unceasingly,

But the price of Bluetooth stubbornly high severely affected these manufacturers use intention. Today, these industry attended IEEE802.15.4 group, be responsible for making ZigBee physical and media media access layer. IEEE802.15.4 norms is an economic and efficient, low-data-rate (< 250kbps), work in 2.4 GHz and 868/928MHz wireless technology used for personal area network and peer-to-peer network. It is ZigBee application layer and network layer protocols foundation. ZigBee is a kind of burgeoning close, low complexity, low power consumption, low data rate, low cost of wireless network technology, it is a cross between a bluetooth wireless markup technology and the technical proposal between. Mainly used for close wireless connections. Its basis 802.15.4 standard, in thousands of tiny sensor between mutual coordination realize communication. These sensors only need little energy to relay way through radio waves will data from a network node to another node, so their communication efficiency is very high.

Xbee/xbee - pro zigbee module

Based on the XBee/Ember chip XBeePRO module is a section of the built-in protocol stack ZigBee module, it through serial use AT command set and the API command set two ways to set module parameters, and through a serial port to realize the data transmission. In order to shorten the development cycle, users provides X - CTU (AT Zigbee Operator command) and two configuration software, can in a short time XBee/XBeePRO module familiar development.

Xbee - pro Zigbee Operator development kit

Aiming at the XBee/Ember chip XBeePRO development kit is a section based on XBee and XBeePRO module on the Zigbee development suite, through development kit can understand the use XBee/XBeePRO module development method, and simple use Zigbee technology, the system provides a set of sole XBee series module development application software Zigbee Operator, through Zigbee Operator, can will XBee/XBeePRO module of the function of perfection. Summary:

1. Working frequency for GHz ISM 2.4

2. XBee power output for 1 HaoWa (0 dBm) (up to 100 meters range)

3. XBeePRO power output for 60 HaoWa (18 dBm), 100 HaoWa EIRP (up to 1 mile range)

4. U.F l. RF connectors, SMA antenna, telescopic antenna can be chosen

5. Industry-specific temperature range (40-85 ° C)

6. In the us, Canada, Australia and Europe used extensively, and has been approved.

7. Support advanced network and low power consumption mode (support ZNET2.5 and Zigbee)

8. Support no.5 12bit AD (development board used 2 road)

9 and development kit matching manuals

10. Digi original X - CTU software, easy to use software to module configuration.

11. Zigbee Operator software, can use through this software to realize various complex function. 

Traffic engineering

Traffic engineering is actually a series of tools and methods, whether in network equipment and transmission lines normal or failure of cases, it can from the given infrastructure to extract the best services. That is to say it to install resources is optimized. In fact, it is to the network engineering or network planning a supplement and perfect measures. Traffic engineering trying to make actual network turnover in the most optimal way exists in the physical network among. The IP network, traffic engineering problems discussed are: solve due to traffic congestion, avoid the invalid mapping and resources caused some network resources utilization, and other resources transition is using insufficient contradiction, According to the network topology, rapid, accurate, effectively dynamic redistribution, especially in network traffic occurs when a fault lines or equipment must be more so.

Traffic engineering problems to solve

Intelligent connection

In order to realize the optimization of network resources, reduce the burden of management personnel, MPLS node will adopt signaling protocol establish end-to-end label switching path (LSR). Intelligent connection can be decided by the user (explicit routing), also can realize by pathways computing algorithm. The currently used link-state database can be OSPF - TE (OSPF traffic engineering) or IS - IS - TE (IS - IS traffic engineering) library, but computing algorithm IS the same. Here must be explicitly note, no additional restrictions will undoubtedly in access computing algorithm minimum cost path. If no additional constraints, path algorithm can obviously improve the management personnel allocation, but clearly routing workload to improve turnover distribution network does not pose a substantial contribution.

Bandwidth estimate

In order to improve the path calculation algorithm distribution, but also need the effectiveness of portfolio other parameters. Estimate bandwidth is one of them. In fact, every LSP needs a estimated bandwidth, and each of the link will have a link congestion coefficient, and the coefficient is according to the link capacity and have taken up LSP capacity and valuations calculated results. When adding a new path, each of the relative path to have to calculate its path congestion coefficient. The new link will choose to have the lowest link congestion coefficient of composition.

Bandwidth measurement

Although estimates bandwidth to improve the network resources utilization has greatly improved, but it is still an estimate. Obviously, to the actual portfolio, the more accurate estimate of the route choice the availability is higher. Due to the foregoing path calculation algorithm USES is a kind of static way without considering the actual time-varying link utilities, so the likely outcome of a link volume estimated too high or too low. Low flow estimates that could cause actual link volume, causing we wish to avoid overload of congestion and packet loss; While very high flow estimates that may cause actual link caused by insufficient, other parts unnecessary potential network congestion.

So, let estimation function better bandwidth algorithm is adopted to measure bandwidth. Regular measurement link utilization rate, utilization rate fluctuation, buffer occupy and buffer occupancy rate fluctuation will be vital. These new parameters by routing protocol regularly publish or above a certain threshold in triggered when the release. Use this to dynamically calculating polymerization portfolio, the effective bandwidth. This method than the ordinary bandwidth estimate more precise and thus enhance the network resources utilization.

Network elastic

Current Internet service for enterprise is critical to the success of, so the user need different service usability. MPLS control mechanism should be able to offer lines or equipment failure restore function. The traditional approach is to adopt an overtime detection, namely a passive way, the new method should be adopted active way, the fault early detection and prediction. Low-level failure information with routing and signaling layer should have direct connection, so that more early to trigger restore countermeasures.

Connection priority

Make certain connection than other link has higher priority is obviously one universal demand, so in the LSR must have this MPLS ability, including the connection setup priority and releasing attachment priority. It is worth noting in fault condition of priority to shorten processing high priority connection of recovery time is very important. In a circuitous route of place, because the network breakdown of dynamic, best circuitous route often only at the last minute, therefore connected to determine the priority must dynamic configuration.

Network reorganization rules

In modern communications network, network lines or equipment, a failure will affect hundreds, even thousands of LSP. Disordered release, restructuring routing and second signaling will lead to switch control system overload, causing network reorganization time is too long. Therefore, in a MPLS must have a refined reorganization mechanism, then must specify different priority LSP group restructuring strategies. The advantage of this also is able to quickly will reshuffled network resources occupation information spread to MPLS node, ensure related restructuring is still optimize network resource considerations.

Marker stack

MPLS mark stacks ability can be significantly improved network core recovery time. Such as a portfolio in the core network polymerization, by adding another layer tags can reduce the number of core network LSP. Once the network core fault happens, just click on the small number of LSP routed reorganization, simplified the restructuring task.

Recovery recovery/path optimization

When the fault MPLS network, network equipment recovery after they still should be restored to the original optimal allocation of resources condition. In connectionless networks, portfolio will automatically restored to the shortest path surface, but in connection-oriented nets, must adopt a kind of similar mechanisms, restore the recovery/path optimization is a connectionless networks that often USES in method. MPLS network in LSR can regularly check whether exist than existing LSP better path, if there are, the old LSP should switching to new LSP. A typical example is in network fault recovery after, temporary LSP and return to the original LSP, another kind of circumstance to restore to the specified path.

Signaling performance

Although MPLS is a kind of topological driven network, most LSP existence time is long, for signaling of performance requirements are relatively low. But because the MPLS purpose is as a backbone technology, must quickly effectively to fault recovery, so actually, signaling the performance of MPLS traffic engineering level of automation have very important influence.

Network service quality

MPLS traffic engineering need to provide the service quality, specifically in the light of different service, especially ahead of the multimedia services offer optional/controllable network service quality. This requires each MPLS can LSR of selected LSP distribution specific buffer and scheduling priority, and obligate relevant network resources. Obviously, a dynamic more service network service quality optimizing system for MPLS successfully is very important. 

Weekend exercise good whereabouts

A week's hard work will soon pass away, weekend white-collars finally gets free. Weekend where have a good time! ? Play what and happy and fitness! ?

Below, give you a few white-collar weekend getaways choice, let you play while, exercising, enhanced physique! Let the more the merrier white-collars play, the more play more healthily.

1, ride horses

Appropriate crowd: work very great pressure, and there is some risk, such as to run his own company person or company management, etc.

Reason: neural day's tight, really tired. Think about the weekend make a person, in the blue sky freely roam the next, not more than playing golf can fulfill your heart who want to fly heart? Heaven and earth, after all our everyone's life circle just corner of the world, we want to escape from the coterie, eager to open more broad world, perhaps be in when riding, in a flash, our hearts dream has realized the half.

Fitness results: riding a horse may exercise your agility and coordination, and can make your muscles are exercise, especially the leg muscles. Ride an hour consumption quantity of heat amounts to 27 calories, and play golf exercise the same day.

2, mountaineering

Appropriate crowd: in the deep computer room work IT clan.

Reason: IT people in close windtight room all day long, computer all day computer out the opacity gases and radiation troubled, mind giddy, if weekends bubble in the gym, you that long not to breathe the fresh air to your skin and body would have issued a strong protests. Weekend mountaineering, let herself in nature, breathe and have sweating, the week bored or tired all lost.

Effect: mountain is excellent aerobic exercise, can promote metabolism, accelerate the blood circulation, still can increase stamina and leg strength, enhance heart lungs function.

3, long

Appropriate crowd: work never in sedentary spent in fall, a lot of such as backache, cervical spondylosis, such as the editing, a freelance, etc.

Reason: run for this kind of man is arguably comparative applicable, but * weekend concentrated run two days, not only little effect, and long-distance running is more, unfavorable acuteness activity in the weekend and free water jogging have become such a foreign latest a physical fitness movement, and is an ideal movement. Because in water jogging, can equally body load and run than land has obvious advantages, and in deep water, runners lower limbs not suffer concussion, thus not injured, after motion will have full-bodied relaxed feeling.

Effect: water resistance is 12 times, air resistance in water ran 45 minutes equivalent to run two hours, water land of obese people especially for jogging. Because of the density of water and heat transfer sex than air, water jogging energy consumption than terrestrial much, can gradually removed body fat.

4, shopping

Appropriate crowd: from dawn to stay in the office of women.

Reason: this is the most popular pastimes female popular, also be a kind of very good aerobic exercise, and gym boring instrument training not only make women compared to go shopping in imperceptible in exercising the body, still cheerful the mood, it is kill two birds with one stone of fitness methods, if stopped by to cleans out good thing is the forehead badger neon stack weight will?

Effect: female shopping little criterion two to three hours a day, too much is constantly exercise can increase your legs, consumption in a lot of heat, reach fitness effect.

5, skating

Appropriate crowd: the usual activities, even if less weekend also lazy exercised.

Reason: skating is set to exercise, entertainment at a suit of fitness project, the lazy man, it is the most relaxing, laughing can achieve fitness results movement, skating main exercise leg ministry muscle, and can carry high body flexibility and coordination.

Effect: skating every half hour consumption heat 175 calories, can strengthen body flexibility and body parts power.

6, diving

Appropriate crowd: everyday nine-to-five job, step by step, no change of groups, such as government officials, secretary, etc.

Reason: the living unalterable, you have vexed, perhaps in the heart bottom have long been changes and exciting, but were afraid to try. Diving will satisfy you to stimulate and free life expectation, in the bottom of the stay away from the crowd, as you came to a and reality completely different world, here, you can leave behind, like a free of fish, the feeling is really happy like immortals. From the bottom to realistic world, you will have shadowfax feeling, in the heart of those who originally fetters crux, worry also become so unimportant.

Effect: diving is systemic motion, their sports effect and swimming par. Another person who can't swim can also oh.

Warm prompt:

Autumn weather is dry and temperature is lower, the outdoors fitness movement, beginning to wear more clothes, wearing clothes should be light soft, cannot too tight, warming up after they take off some thick clothes. After exercise, if the sweat sweating much shall timely dry, change to a sweat sportswear, socks, and dress, prevent colds. 

Housework fitness energy consumption rankings

Drag mop the floor, wipe a window, and planting flowers and trees, etc, can let the body activities at home with appropriate activity, and can consume calories and not too tired. In addition the stairs instead of an elevator, Journey, with relatively short walk instead of hitchhiking, can be in life implement "movement". 

For ferial don't exercise, the activity is little people, will now be nurturance regular exercise habits, may be difficult, and think of movement, the sweat after wet glue sense and sweat stink, is not let a person feel at ease, may be more reputations. So have thought recommended weight, might as well start from daily life "move".

Drag mop the floor, wipe a window, and planting flowers and trees, etc, can let the body activities at home with appropriate activity, and can consume calories and not too tired. In addition the stairs instead of an elevator, Journey, with relatively short walk instead of hitchhiking, can be in life implement "movement".

Easily consume 100 calories

With 60 kg of people:

Meals: don't complain family did not help meals, wash, cut, boil, fry, steamed, just 39 minutes, he again little 100 calories.

Sweep the floor: mopping the floor as long as 20 minutes of time, can consume 100 calories.

Sweep the floor: use time also need not long, just 25 minutes, he can consume 100 calories oh!

Shopping: whether bought things, stroll a 33 minutes, they can reach a consumption of 100 calories goal.

The stairs: 7 minutes, he can consume 100 calories, still can exercise cardiorespiratory function!

Down the stairs: as long as 14 minutes, he can consume 100 calories.

The flowers and trees planted: in the home the balcony, plant some flowers and plants, used to beautify the environment, pleasing. And 20 minutes of gardening, and can burn 100 calories, kill two birds with one stone of good service.

In everyday life, there are many is both lighthearted and the interesting method, can in no sweat circumstances, waste heat, let "activity" become "life" a portion, as nurturance regular exercise warm up before.

When you have habit in life increase many activity, can again from weeks after Saturdays off day off began to choose your favorite, can be competent the exercise types, such as swimming, cycling or dance etc, each exercise 15-30 minutes and reference regular exercise to execute, believe you would then is more beautiful, more healthy, more confident. 

encapsulation technology

The so-called "encapsulation technology" is a kind of integrated circuit with insulating will of plastic or ceramic materials packaging technology. With the CPU, for example, the actual see size and appearance isn't real CPU kernel size and appearance, but the CPU core components after packaging products. Packaging technology is a must for chip encapsulation, also is crucial. Because chips must with the outside world, to prevent the air isolation of the circuit chip impurity to corrosion in electric performance decline. On the other hand, encapsulation and easier to the chip after installation and transport. Due to the stand or fall of encapsulation technology also directly affect the chip itself performance play and the connection of printed circuit board (PCB) design and manufacturing, so it is of vital importance.
Packaging technology
Encapsulation also say, is refers to install semiconductor integrated circuit chips with shell, it not only plays placed, fixed, sealing, protect chips and enhance the role of thermal conductivity, and still communicate with an external circuit chip the inner world of bridge - chip contacts with wires connected to encapsulate shell pins, these pins and through printed circuit boards wire connection is established with other devices. Therefore, for many integrated circuit product, encapsulation technology is very crucial one annulus.
Using CPU encapsulation are use insulation plastic or ceramic material packing up, can play the sealing and improve performance function. Chip electrothermal Now the processor chips in frequency more and more high, function is more and more strong, pin number is more and more, encapsulation appearance also constantly changing.

How to create their own exercise environment

Family fitness, always is many people in advocating a concept, therefore, to think in the home fitness people speaking, according to their budget, select the most appropriate fitness equipment, is one of the main power exercise.

Family: obese family

(right) treadmill equipment:

Running is most people accept an aerobic exercise, and indoor treadmill is many fitness person in the family fitness list. If you belong to whole body fat, then the treadmill family really can bring a lot of help. Running function shows fitness person when running speed, time, heart rate, quantity of heat, rhythm, distance etc indicator fitness person can at any time according to own physical condition adjusting the training intensity.

Nowadays, the treadmill prices have already started to decline, and some functional comparison complete treadmill current price is cheap, so long as own economic conditions permit, can choose for the family of a function of complete the treadmill.

Family: office personnel is more family

(right) row implement equipment:

We all know, boating, need arms strength, some still need legs and abdominal combination of forces. And that for many office crowd, it is precisely where need to exercise, especially some long-term in front of a computer work of the staff, arm and shoulder always feel acid aches, and because of sitting relationship, abdominal fat is growing. So, a lot of people at home is sit-ups and pull elastic rope, but due to the action does not reach the designated position, effect often not obvious. So choose of nowadays popularity row implement, will be very good choice.

Rowing action of spinal joints, exercise activities has obvious effect in the back muscles. Practice "boating" when, want to notice the continuity, every action after the stirrup stretch as far as possible action doesn't appear pause. In row process, action must reach the designated position. Moving range after meeting make to participate in sports muscle cannot fully extend or contraction, make training the wasted effort. Row implement the price is in commonly 5000 yuan, for some workplace observers alike, affordable.

Family: need to enhance their physique family

(suitable equipment: spacewalk machine, a)

For many families, exercise goal is to enhance their physique, then what sports can be enhanced physique? Many people will naturally associate to aerobic exercise. In fact in aerobic exercise, footfall, cycling in athletic intensity on request is not big, but also is the most suitable for family last-borns participate together fitness methods. So, looking for a indoors can also satisfy the two sports fitness equipment became many goals.

First, the reporter to recommend is spacewalk machine, this set stroll, canter, stationary bicycle sport in one of the machines of wonderful lies in its own design: activity type pedal installation make spacewalk machine fitness movement coincide with the body's natural stride coincide, when motion through the thumbs and coordination, reach fitness goals.

Secondly, we should choose to be a lot of young people like a, this kind of fitness equipment with ordinary bicycles have incomparable advantages: can be free to play his bike riding speed, control of time. Through the exercise on the configuration of the electronic watch, you can always observe their yould speed, time, heart rate values, etc. But some people feel indoor sport compare depressive, so in the fitness car can solve such helpless, because some exercise on the color screen that device can show different scenery pictures, let you during exercise as if you're in the field outside, feeling mellow. 

Running in the morning you can protect your feet

Running posture to scientific and reasonable. Should avoid sufficient with ground first, we should use the forepaws before touchdown, give full play to the foot arch of elastic, favors completes the buffer action, reduce the resistance of the landing.

(1) JianShenPao try to choose relatively loose exercises in the gym area, best road running, don't run in a very hard floor running.

(2) when running don't wear hard bottom shoe, to wear thick soles softer shoes, sports shoes, boots, children's best to wear rubber overshoes when also can wear no BuDeXie, but not a hard bottom shoes, plastic shoes.

(3) running posture to scientific and reasonable. Should avoid sufficient with ground first, we should use the forepaws before touchdown, give full play to the foot arch of elastic, favors completes the buffer action, reduce the resistance of the landing. Leg after pedal to stretch. Feet when landing should be used well buffer strength, not too strong, so run up to make the person feels feet legerity and rich flexibility, still can reduce the burden of the foot, already but the lasting, can avoid again pain.

(4) when I was running, LACES shoulds not be too tight, otherwise department would hamper foot blood circulation. Often use hot bubble foot, at least in each exercise every night after a seven-hour run and mother.she with hot water wash feet, can lower limb foot muscle viscosity, enhance the ligaments elasticity and stretching, also can prevent pain, which is conducive to the next morning exercises.

(5) to early morning run around, doing good sufficient warm-up activity and finishing activities, especially lower limbs hip, knee, ankle, muscles, tendons and ligaments are fully open, can take part in the activities JianShenPao exercises. These to protect good foot is also very important.  

Air Interface

In the mobile device transmission, the air interface is a through wireless communication, to link with mobile phone end user base stations. In GSM/UMTS, various forms of UTRA standard is air interface, also is a kind of access mode "access modes." on mobile phones, "air interface" said mobile phone base stations and wireless transmission between standard. It defines each wireless channels use frequency and bandwidth, or defined by coding method.

In the OSI model under, air interface belongs to the first layer and layer 2 implementation. 

Traceroute

definition

Internet, i.e. international Internet, is the world's largest computer network, to be more exact, network of networks. It consists of all over the world have tens of thousands and millions of computer LAN composition, and heterogeneous networks is used in the TCP/IP protocol communications between networks. Internet, information transmitting through net many segment of the transmission medium and equipment (routers, switches, the server, the gateway, etc.) from one end on the other side. Every connection in the Internet of the equipment, such as hosts, routers, access server generally will have a separate IP address. Through Traceroute we can know that the information from your computer to the Internet at the other end of the host is go what path. Of course each packet by a given the same starting point (returned) reach a certain the same destination (take) walk path may be different, but basically most of the time have walked routing is identical. UNIX system, we call Traceroute, MS Windows for Tracert. Traceroute by sending a small packet to purpose equipment until its return to measure its need how long. A path of each equipment to measure Traceroute 3 times. Output included each test time (ms) and equipment's name (if any) and IP address.

principle

1. Almost every online people (especially Webmaster) for their computer (or other equipment) and Internet connection, routing (size), connected time, speed, etc. Are all very concerned. Use ChianNetMap organized by the Webmaster provide various areas Traceroute gateway service, will give you a satisfactory answer. From your computer to any other place, ChinaNetMap (Traceroute) can provide the intervening each equipment (IP address) and its connected time. It allows you to draw the path through the network. 2. Many companies and institutions have or are set up their own server - especially Web server. Once have their own Web server, with the number of Internet users increasingly (including potential and couldn't statistics of netizens), you must be very wants to know whether they can relate to connect you. Your ISP how with one or more NAP connection, and their connection efficiency will directly affect the quality of your connection.

3. In choosing the ISP, backbone connections, your Site host, most knowledgeable netizens like check the Site of connection performance and other is how accurate and who even, even where. Traceroute will give you a perfect answer. 

Spring exercise many benefits

Spring is coming, sunny, niaoyuhuaxiang, be people vti optimal opportunity. In the spring of the temperature gradually raised, accelerate human blood circulation, make every cell, each part to produce new changes. Strengthen spring exercise, must make body and mind keep flourishing, energetic, health illnesses. Let us into nature, the physical and mental depression and burden to the life are discharged, sorrow and trouble elimination, to experience workout-related wonderful!

Spring fitness precautions

Attention: due to the preparation activities to warm spring weather by cold when the temperature changes, lower temperature regulating center and internal organs functioning of the varying degree is reduced, muscle and joint organs such as strong viscosity, therefore, before taking exercise must make full preparations activities, lest produce muscle or ligaments and joint sprains wait for an accident.

Cold-resistant windbreak and prevent mist: spring season, climate change changeable, take exercise in the morning, clothes don't wear too little, do not sweat reduced too much. After exercise should be timely dry sweat.

Meet sandstorm weather choose as far as possible when the wind environment exercise, fog to try to choose air flow big environment exercise.

To master a exercise: spring after exercise can increase gradually, but not impatient, more do not blindly bimatoprost, lest cause excessive fatigue.

Strengthen the fitness to be spiritually

Spring, full of vitality, it is people long height, strengthens the muscle the opportunity. For spring training, can inhale more oxygen and anion, improve the body metabolism, the ultraviolet ray in spring scenery extremely antiseptic function, can promote human body form vitamin D, beneficial to the development and growth of teenagers bone.

Spring is apt to make "chunkun", then if strengthen positive fitness activities, will overcome "chunkun phenomenon, refreshing.

Spring training methods

Young children can be based on site, time, hobbies, such as choice exercise program TiJian, skip, TiaoPiJin, kite flying kite, spring is good season, kite when I first hand and move the whole body, a hand brain coordination, a strong body and mind.

Many young friend fitness methods, such as walking, running, play, mountaineering sports activities, such as conditions can also travel. Elderly people and dieters applicable low intensity, low energy consumption movement patterns, specific include: go quickly, good-bye, calisthenics, tourism, riding a bicycle, entertainment, garden labor etc. 

Soybean -- fat isolation superior

Human body excessive food, especially high fat food intake, in addition to the digestive function brings unbearable pressure outside, return the body left many harmful metabolites, and direct or indirect damages the health of the body. Nutritionists tells us that a balanced diet is the guarantee of health.

If phatic unavoidably, choose some help digestive health food also is necessary. Lecithin is a naturally occurring in food YuDaDou compound organic, and its main nutrients is phosphatidyl choline, lecithin is human body cell membranes, is a major component of the daily intake of nutrients necessary. You know, the composition of our brain substances have 1/3 above is lecithin, it is enough to prove its importance.

Therefore, many nutritionists the lecithin as with protein, vitamin equally important "third nutrient". Nutrition experts point out, the daily intake of six to eight grams of soy lecithin, besides can promote the growth and development of maintaining brain function of normal brain, can also improve fat metabolism and help reduce cholesterol in mind vascular walls and liver deposition and is thus preention of cardioascular disease, reduce fatty liver and gall stones happen effect.

Along with the science and technology progress, soy lecithin processing extraction process from the traditional chemical solvent method development to the current physical ultrafiltration extraction, bioactivitiy higher. 

D/A converter

Digital-to-analog converters, say again D/A converter, abbreviation DAC, it is the digital quantity change into analog devices. D/A converter basically composed by four parts, namely power resistance network, operational amplifiers, benchmark power and analog switches. ADC generally with digital-to-analog converters, ADC namely A/D converter, abbreviation ADC, it is the continuous analog signals into discrete digital signal devices.

Digital-to-analog converters analytic principle

A binary digital quantity forms of discrete signal converting to standard amount (or A reference amount of benchmark analog quantities of converter, abbreviation DAC or D/A converter.

The most common way digital-to-analog converters

The most common digital-to-analog converters is parallel to the digital quantity converts binary dc voltage or dc current, it is usually used as process control computer system output channel, and actuators are linked together, the realization of the production process of automatic control. Digital-to-analog converters circuit are used for using a feedback technology adc design.

Digital-to-analog converters conversion ways

Parallel digital-to-analog

Analog-to-digital conversion has two transformation way: parallel analog-to-digital conversion and the serial analog-to-digital conversion. Figure 1 is typical of parallel digital-to-analog converters structure. Dotted line box of digital operation switch and resistor network is the basic components. Figure device through an analogue reference voltage and a resistor trapezoid network produces on the reference quantity as the benchmark scores of right or right value current voltage, Using digital input variables control by a group of switch to decide which some current or voltage sum up form output. The so-called "rights", is the binary number of each represents the value. For example the three binary number "111", right 1 bit "rights" is 20/23 = 1/8; Second place is 21/23 = 1/4, The third is 22/23 = 1/2. Figures more ordinal analogy. Figure 2 for the three digital-to-analog converters the basic circuit, a reference voltage VREF in R1, R2, R3 produced in binary right currents, current through the switch. When the bit values is "0", and to connect, When the bit values is "1", and output summarizations busbar is connected. A few road current generated by the feedback resistance sum Rf output voltage. Voltage polarity and reference quantity instead. Input terminal of the digital quantity every change 1, only cause output relative amounts change 1/23 = 1/8, this value is called digital-to-analog converters resolution. Figures more resolution is taller, conversion of precision is higher also. Industrial automatic control system adopts the digital-to-analog converters are mostly 10, 12, convert the precision of 0.5 ~ 0.1%.

Serial digital-to-analog

Serial analog-to-digital conversion is the digital quantity convert pulse sequence number, a pulse equivalent to the digital quantity of a unit, then each pulse into unit analog quantities, and will all the units analogue addition, get with the digital quantity proportional to the analog output, so as to realize the digital quantity and analogue conversion.

Along with the digital technology, particularly the rapid development of computer technology and popularization, in modern control, communication and testing etc, in order to improve the performance of the system indexes, the signal processing is widely adopted digital computer technology. Due to the system of the actual object tend to be some analog quantities (such as temperature, pressure, displacement, images, etc), to make the computer or digital instrument can identify, handling these signals, must first will these analog signals converts digital signal, And through computer analysis, after processing output the digital quantity also often need to convert to the corresponding simulation signal can be accepted for actuators. So, you need a can in analog signals and digital signal serve as a bridge between the circuit -- modulus and digital-to-analog converters.

Convert an Analog signal into A Digital signal circuit, called ADC (hereinafter referred to as the A/D Converter or ADC, Digital Converter); to Analog to produce stats Converting Digital signals for Analog signal circuit called digital-to-analog converters (hereinafter referred to as D/A Converter or DAC, Digital Converter); to Analog to produce stats A/D converter and D/A converter computer system has become an indispensable interface circuit.

To ensure system for handling the accuracy of the results, A/D converter and D/A converter must have enough of conversion precision, If we are to achieve rapid variation signal of real-time control and testing, A/D and D/A converter also requires high converting speed. Convert precision and converting speed is measured A/D converter with D/A is an important technical indicators. With integrated technology development, has been developed and produced many single chip and mixed set molding of A/D converter and D/A, they have more and more advanced technology index. This chapter introduces several common A/D and D/A converter circuit structure, working principle and its application.  

Link Popularity

In the search engine marketing, commonly used to measure the link popularity by other links to web site called "the number of inbound links quantity", or colloquially known as "from external web link", "by other web links of quantity".

Deep understanding

For this reason, the search engine optimization work are paying attention to the website links quantity, appear even many websites manufacturing various meaningless web links to obtain your search engine ranking advantage, actually this is wrong, search engine not only attention website links quantity, but also the quality (attention link to web sites and web PR value has relationship), by massive low quality web links and cannot obtain the ranking advantage, will even be considered a "link tried" by search engine rankings even punish - lower cancelled included qualification.

By the end of 2004, after the value of about link popularity has some new trends. A few suggested, such as Google search engine ranking algorithm for the website links number of weight has no longer as attention, but exactly obtain the importance of links have many tall, in addition to Google's relevant technical staff outside, I'm afraid nobody can say clear.

status

Because the present site link exchange, multilateral circulation links, "link farms", and other forms of existence, this kind "recommended" meaning also gradually lowered, so change related links to web search engine ranking algorithm is also naturally things. Just as the early search engine from the META tags content dependence to finally give up this ranking strong rules, on the one hand, because many sites using this rules affect the impartiality of the rankings effect, and even cause unnecessary law dispute, on the other hand is due to the search ranking algorithm has updated understanding and more accurate method. 

What suits you outdoor sports

The temperature rise gradually, girls clothes gradually thin, whether you are ready for spring this wonderful season? Whether you want to let oneself both positive and flank, sit down, bend, cannot see a dewlap, figure curve flawless? Now for you personally create 360-degree perfect thin body to plan, comprehensive various slimming information for your spring sufficient preparation!

run

Characteristics, main training with oxygen function, make the cardiovascular tissues more health. Improvement of leg ministry line, can make joints, muscles and ligaments more flexible, make muscle more strong, have very good body effect. Compared with the treadmill and sprint, the number of calories less. Due to a fixed long-distance runner, more than sprint target training stamina and will.

Suitable for objects:

1, want to improve with oxygen function and size.

2, want to quit smoking.

Calorie consumption per hour () : 531.

Precautions should be your best.

Nutritional supplement, Another selenium, vitamins A, C and E are antioxidant function, prevent free radicals formed.

Equipped with a T-shirt and sneakers.

skiing

Characteristic, meanwhile stressing legs muscle strength and elastic joints.

Suitable for objects.

Calorie consumption per hour () :) (ground), 354 (lower slope).

Note, should pay attention to the temperature adaptation, and prevent bask in measures, for the snow reflected effect, can have more than the usual sun injury. Only when skiing holiday, in the afternoon and the first two days vacation is injured high-risk period.

Nutritional supplement, muscle in glucose consumes completely, and pay more attention to starch qualitative added.

Equipment, sports shoes, the sun glasses and ski equipment.

swimming

Characteristics that can also activities muscles. Due to swim in the water, you can in zero gravity during exercise systemic muscle and joint.

Suitable for object, relevant section trouble or a stiff joints competent than the average person.

Calorie consumption per hour () : 59 (freestyle); 59 (breaststroke); 694 (butterfly); 472 (backstroke).

Note:

1, if in outdoor swimming word, should pay attention to prevent bask in.

2, before launching. Don't eat too full, and must do warm-up exercise, lest the cramp.

Nutritional supplement C and E can resist oxidation, and prevent free radicals in the sunshine makes the skin aging.

Equipment, waterproof mirror, swim cap and prevent bask in things.  

Tai chi slow reactive adjustable body and mind

Tai chi slow, but slower sense. Studies have pointed out that tai chi and slowly ran the same for heart good, but the former consumes less energy, suitable for everyone - including patient - practice. Tai chi practiced to concentrate, the process of practice must adjust, drop pressure.

The key is, when willing to take the first step.

Many local and foreign medical research proves, mild taijiquan, can improve balance and their arthritic symptoms, slow down bone loss, strengthen heart-lung functions, but also for urbanite minus the pressure of the spell. Tai chi consumption physical less, not suitable for violent sports like running of chronic patients, can practice, which is also one of its advantages.

Gentle driving blood circulation

Emigrant Australia years of Yang's sixth generation successor tai chi FuQing springs, said to running the same, tai chi can promote blood circulation. Just, running to the knee joint damage is walking four times, aggravating knee strain of opportunities. Tai chi movement and speed, and stretch generous evenly and sofe advantages, at least on joints burden much less.

Furthermore, the tai chi through  joint activities drive and then improve muscle whole body blood circulation, compared to other exercise mainly by stimulation of the heart to drive the circulation, to the heart of the load less, cardiac patients may also be practiced. Foreign had the research points out, except for swimming outside, tai chi is another kind of doesn't increase cardiac load movement. According to the Shanghai tongji university 1977 to 1978 research, no ill practice taijiquan also benefit from. Participants practice YangShi taijiquan 1 year, average blood pressure by 84.5 134.1 / mmHg, descend to 124.9/79.8 mmHg.

Unionizing footwork alternative actions

Tai chi moves have cloudy and Yang, have empty solid, refers to the legs of actions. In a "real steps" or "Yang steps), the focus in the former, "Virtual steps" or "Yin steps), the focus in the rear. TCM view, said people have 3 "heart", besides natural 1 outside, one of which is thigh muscle. Practice taijiquan in the process, virtual reality step kept swapping step, and the barycenter alternating, virtually since the heart pumps blood  like the function helps the whole body blood circulation. And the movement must slow, just have this effect.

The slower to what extent? FuQing springs says, is about social dance "ManSi" speed, almost equal to men breathing rhythms.

Relax shoulder cubits down pressure

Tai chi and slow, and also to mental health. Taijiquan is one of the main points, "fascinating shoulder fall cubits", meaning shoulder and elbow to relax and not clamping shoulders, also do not cock elbow. Want to attain "sink shoulder fall cubits," psychological cannot too nervous and open-minded to broad. "This easier said than done." He said, wants the tai chi liande good, still must first change of mind, Somebody also conversely, by tai chi slow speed to influence the mentality, make oneself concentrating, and learn to let go pressure.

Tai chi pattern, stress is the balance of Yin and Yang. Rapid pace, just need tai chi slow with soft to harmonize. 

Wireless controller

Wireless controller is a kind of network devices that can automatically optimize basic wireless network, and to support the network above senior mobile service.

Cisco Mobility step.adopting the solution will 526 wireless access points controller and 521 (AP) combine into a flexible and economic and efficient wireless solution to satisfy the small and medium enterprises (SMB) special needs.

As part of the small and medium-sized enterprises complete strategy, Mobility step.adopting the solutions and for small and medium enterprise development of unified communications solutions - cisco intelligent commercial telecommunication system, not only can offer distinctively voice, data and video, safety and wireless capabilities, also with calendar, E-mail and CRM etc original desktop application integration together. With the rapidly changing needs of the customer, cisco step.adopting Mobility solutions will continue to expand, from advises wireless characteristics of solid mobile base expanded to can support leading mobile services and applications of economic efficient advanced wireless networks. 

Video-telephony

Video-telephony is to use telephone line the speech of the real-time transmission and images (user of bust, photos and articles, etc.) of a kind of communication mode. If the ordinary telephone is "ears", then the videophone will both "ears", and "forward".

equipment

Video-telephony is by telephone, camera equipment, TV receiving display equipment and controller to compose. The videophone phone and ordinary as a telephone is used for conversation, Camera equipment function, is to get his user image transmitted to the other, TV receiving display device, its effect is receiving each other's image signal and on the screen shows each other's image.

Section classification

The image shows the videophone according to different, divided into static images videophone and dynamic image videophone. Static images videophone on fluorescent screen displayed image is static, image signal and voice signal utilization of existing analog telephone system, namely transfer image transmit alternately can call, Transmit a frame of users bust still images need 5-10 seconds.

application

A videophone equipment can be like an ordinary as a telephone access PSTN use. Dynamic image videophone displayed image is active, users can see each other's smile or talk image. Dynamic image videophone image signal for contains large amount of information, accounts for the wide frequency band, not directly in users online transmission, needing the original image signals into digital, digital image signal, and then must still using band compression techniques of digital image signal, "compression", make the accounts for the band, so that it can narrow in users online transmission. Dynamic image videophone signal for digital signals, so be on both digital transmission. The videophone can also add video recording equipment, like recording telephone same, the image recording down in order to preserve. Static images videophone already in public phone use online, and the dynamic image videophone because of high cost of application has not yet. But can be expected, as microelectronics technology development, the large-scale, vlsi, as well as the extensive use of the rapid development of integrated services digital network, dynamic image videophone inevitably in the future communication plays an important role.

The videophone business

The videophone business is a point-to-point of video communication business, it can use telephone network two-way real-time transmission call both images and the speech signal. Because the videophone can get face-to-face communication effect, realizing people communication both hear its voice, and see its person dreams, so since the idea after suffer the widespread acclaim for her, and people were expected to do that. However, after a long wait for the videophone has not been widely used, always from ordinary users far away. Video-telephony is just a hype? If not, then the videophone development condition? Market foreground how?

Bumpy decades

The videophone from concept put forward, technical development to market startup, after many bumps and tortuous. Especially in China, videophone market in the long run, thunder, roast situation, market delayed startup. Few customers have terminal after decades of research and development remain basically stay on books, fail to win, and large scale application videophone just at this unfortunate ranks.

As early as in a 1950s had been suggested videophone concept, that should use telephone line transmit speech simultaneously transmit images. In 1964, the United States bell LABS officially proposed videophone related solutions. But, as the traditional network and communication technology, the constraint of videophone hasn't been substantial progress. Until the late 1980s, with the chip technology, transmission technology, digital communications, video decoding technology and integrated circuit technology unceasing development and matures, suitable for commercial and residential videophone was able to come to the surface to people's perspective.

Decoding chip technology is the key to the development of video-telephony, without a core decoding chips, videophone is only like, non-existent. Voice and image in transmission, must pass a compression - decoding process, and the chip is undertaking the task of coding and decoding, only chip on the output side will voice and image compression and compiled into the suitable for transmission lines of communication in a special code, but in the receiver will be special code into people can understand the voice and image, can form a complete transmission process, make conversation with both realize sings in the exchange.

Transmission line influence videophone communications quality. The traditional telephone lines were ordinary twisted-pair cable, used primarily to transmission of voice, audio simultaneous transmission, the transmission rate can only reached 3.36 K, so in ordinary telephone lines, under the support of cannot transmit clear coherent image.

Protocol standards are inconsistent, affect the market promotion. Long-term since, although there are makers offer videophone, but because they fragmented, and does not have uniform standard, and various videophone not share, affecting the videophone market development. In the protocol standards not unified case, only the users buy the same type of videophone to achieve "visible" effect, if a user bought a manufacturer of visible calls, and b users buy is b home, then they call can't "visible". 

2 groups of simple pilates thin leg has no company quantity

Pilates is now with yoga eponymous model body movement way of a kind, introduces below your is about thin leg the simple action, hope to be useful to you!

Practice group 1: rearmounted support

Action effect: ham lose weight. Meanwhile frap coxal, abdomen and lower back.

Action 1: posture, the bosom, accept stomach, heavy shoulders. Put your hands on your legs straight out, behind, pointing finger ahead, inhale.

Action 2: exhale, will coxal pulled upwards, leave the ground, foot stretchs tight straight.

Movement 3: inhale. Continue improving hip, until the body stretched into a straight diagonal lines. Hold for 10 seconds. Exhale return to action 1.

Repeated 2 ~ 4 back.

Tips

Second-ranking keeps the body stable.

Second-ranking don't shrug.

Second-ranking stretch it out the arms and legs.

Second-ranking if wrist injury stop practice.

Practice group 2: single leg kicks

Action effect: from hip - thigh calf - ankle, comprehensive guide-explore-design-grasp "plastic".

Action 1: prone, palm down, forearm tiejin ground, the elbow strut in shoulder under thescapulae, raise the upper part of the body. Legs together unbend, feel hip tightening.

Action 2: expiratory. Crus carried from the ground 15 degrees, knees do not bend.

Movement 3: keep up 15 degrees posture. Inspiratory, right foot kick to the right hip, Exhale, left foot kick left hip once.

Left, right foot repeatedly kicked 6 ~ 8 times. Exhale relax back to action 1

Tips

Second-ranking head and neck, back to keep a straight line, don't fadeaway.

Second-ranking don't shrug, outlining the.

Second-ranking remember accept stomach.

Second-ranking kicks, another leg always to keep from the ground up to 15 degrees.

Determined to use ham and coxal forces will crus carried from the ground, rather than rely on your knees 

Climbing stairs

The leisure fitness the new law - many climbing stairs is good for health

At the moment, the growing public trying a new new fitness way -- ascends the stairs.

Originally on 10 minutes of stair burns calories 200 CARDS, down the stairs for the quantity of heat that use up stairs 1/3, is the best workout. This is an aerobic exercise, can consume metabolic body fat, enhance heart lungs function.

At the same time the stairs, heat consumed four times more than walking, running more than 29 percent, in the prevention of fat patient is good. People had middle-aged, because activities, such as the decrease relatively often fluctuation building, can strengthen the coronary artery blood flow, prevent the occurrence of coronary heart disease.

However, ascend the stairs ascended in slow boarding advisable. A second step speed uniformly, pace to composed and rhythmical, can strengthen waist muscle power and limb muscles ligament activity ability, and can keep the joint flexibility, day long legs can become forceful.

Each terengganu stair athletic time shoulds not be too long, with 10, 20 minutes advisable. Terengganu stair speed and athletic intensity should maintain moderate, with feeling obvious tension and exhausting for degrees. Terengganu stair steps should as far as possible, steadfast, lest step empty fall, causing sports injury.

Stair corridor to relatively capacious, bright, the air is fresh, not in placing objects of stair and turning exercise. Before taking exercise should first activity waist, knee and ankle, exercise should wear soft bottom shoe, don't force yourself to do heay-duty action, want to hold.

Climbing stairs exercise how large it is

Reporter in the international health and nutrition congress "same healthy nutrition exhibition held found, many citizens to free physical evaluation online itch to try. A 30-something male white-collar complain a way: "I am engaged in IT industry, working overtime every day to more than 10 PM every year, even if have a fitness in card, but all the year round and not using a few times."

However, on site working staff posing for another truth, proof of daily life physical activity can also achieve athletic effect. Staff will a man weighing 150 jins of male data index, using every day after input computer terengganu stair fitness methods, everyday stairs each 20 minutes, computer immediately calculate the energy consumption is 202.25 kilocalorie. 

Cellular Network

The mobile phone service difference is divided into one of hexagon branch area, every village set a base station. Formed shape looks like honeycomb structure, thus the mobile communication mode is called cellular mobile communication mode. Cellular network and may be classified as analog cellular networks and digital cellular network, the main difference in the transmission of information way.

Practical reasons

Cellular networks to be used extensively reason is originates from a mathematic hypothesis, hexagon considered use at least a nodes may cover the largest area of graphics, for saving equipment construction cost consideration, hexagon is best choice. This forms of network covering together, shape is very much like a honeycomb, so called cellular networks.

part

Cellular network composition has three main parts: mobile station, base station subsystems, network subsystem. Mobile station is our network terminal equipment, such as cell phones or some cellular industrial equipment. Stations including our daily see subsystem mobile base station (tower), wireless transceiver large equipment, special network (typically fibers), countless digital equipment etc. We can put the base station subsystem is seen as the wireless network with wired network between converters.

Common cellular network type toinclude: GSM network (some countries called PCS -- 1900), CDMA network, 3G network, FDMA, TDMA, PDC, TACS, AMPS, etc

Cellular and frequency reuse

Honeycomb: a large area is divided into several small honeycomb, using multiple small power transmitters instead of a high-power cellular networks

The transmitter. Commonly used to describe the hexagon honeycomb shape.

Frequency multiplexing: each honeycomb use a set of channel. If two honeycomb apart, can use far enough in the same group channel. Clusters (cluster) : of N cellular composition of cellular group, use all frequency resource frequency multiplexing factor (reusefactor) : 1 / N for of hexagon honeycomb, N = i2 + I * j + j2 = 1, I > > = 1, j, therefore, N = 3,4,7,9,12...

Cellular geometric said

Cellular usually use hexagon prond. Why is hexagonal rather than round? The vertices to geometric center isometric polygon, can complete (without overlap) in land cover an area of geometric shapes are: may square, equilateral triangle and hexagonal three kinds of shapes. In the square, equilateral triangle and hexagonal, area of hexagon is the largest.

Cellular coordinate system

Use (I, j) says a honeycomb coordinates. For example: cellular A coordinate for (2, 1)

Honeycomb channel allocation

FDMA system: by signal attenuation principle. Key: treat spectrum is divided into several channel (user channel carrier), far enough in distance can multiplexing channel = > channel planning affect system performance.

Static and dynamic channel allocation: - static channel allocation: each honeycomb preassigned a fixed set of channel, implementation is simple.

Dynamic channel allocation: stations from MSC in dynamic allocation a channel (percall), honeycomb can use all of the channel and reduce the blocking probability, realize complex, requiring a real-time flow testing and base station coordination between processing.

Network type

Common cellular network type toinclude: GSM network (some countries called PCS -- 1900), CDMA network, 3G network, FDMA, TDMA, PDC, TACS, AMPS, etc.

Type classification

Distributed cellular networks

A distributed cellular network (100) provides with multiple mobile station (102) of the wireless communication. Multiple base transceiver letter machine network components (104) is configured to in a wireless medium with multiple mobile communication platform (102), each of them receiving letters Taiwan includes base for coupled to a network (110) network interface. At least one mobile station controller network components (108) includes a suitable for coupled to the network (100) network interface. On the system (100), so to efficiency and configuration for base transceiver letter (sets), base station controller (104 106) and mobile switching center (108) the communication between the portfolio for load balancing. The invention of the advantages including low cost transceiver letter machine (104) combined with flexible deployment, thus with low cost for large area realized the telecommunication covers.

A distributed cellular communication systems, including a network; A coupled to the network public switched telephone network (PSTN), Multiple coupled to the network, receive letter machine, multiple transceiver letter machine geographically separated, and each one is configured in a wireless medium and related district of mobile communication stations, At least one coupled to the network data processing system, this at least a data processing system is configured to execute a computer program, this computer programs include suitable for enables multiple transceiver letter function in the mobile station and between a mobile platform and PSTN to transfer data between the software function block, these software function blocks including: an implementation MM function of mobility management (MM) function blocks, An implementation VLR function of visitor location registration (VLR) function blocks, An implementation CM function of communication management (CM) function blocks, Multiple implementation RR function radio resources (RR) function blocks, wherein RR features included in the mobile station from one village to another village move when switching multiple transceiver letter machine, so as to keep the communication between the moving platform and network communication between.

Cellular mobile phone

So-called cellular mobile phone "shall refer to a mobile phone services region can be divided into several each other adjacent area, every village set a base station network structure. Since each district positively hexagon, another adjacency, look from whole, shape resembling a honeycomb, so people call it "honeycomb" nets. With several honeycomb district covers the whole service of large, medium capacity mobile phone system is called cellular mobile phone system, the abbreviation cellular mobile phone.

Cellular mobile phone biggest advantage is frequency can be reused. Perhaps everyone know, in our that mobile phones mobile communication, everyone takes a channel, i.e., the system will take out a channel for you. Meanwhile call it, limited channel may not use, so they will appear communication obstruction of the phenomenon. Using honeycomb structure can use the same group of frequency in several distance apart of village repeated use, so as to achieve the purpose of saving frequency resource. For example, we will be a city divided into 72 village, every 12 village form a community group. Let them use jointly 300 channel. So, we can put 300 channel is divided into 12 group channel, each group 25 channel, the first community group use group 1 channel, the second district of use in group 2 channel, and so on. After appropriate arrangement, different area of the same Numbers of residential district is group channel can be reused. Although these cells sites by use of radio frequency and same, but because they are far apart to each other, and waves scope is limited, each other can't cause interference. So, a group of frequency reusable 6 times, originally 300 channel can only for 300 users at the same time, but now I can also calls for 1,800 users to talk to each other.

Cellular mobile phone system mainly consists of the mobile station (auto telephone, mobile phone, etc.), wireless stations and mobile telephone exchange center. Every village stations are connected with mobile phone exchange center, forming a cellular mobile networks. Mobile-phone networks with city PSTN and domestic and international long-distance telephone network is linked together, make the mobile phone users can not only with net of mobile phone users on the phone, still can with larger range of mobile users and fixed users on the telephone.