Time Division Multiple Access (TDMA) is the Time Division into periodic frame each frame again divided into several Time buttress sends a signal to the base station in meeting regularly and synchronization condition, the base station in every Time buttress respectively in receiving each mobile terminal signals and not mixed faze. Meanwhile, base station hair to multiple mobile terminal signals are arranged in order to set the transmission of time, each mobile terminal as long as in the designated time buttress inside receive, will be able to close the signal in the road to its signal distinguish and receive down.
characteristics
TDMA system has the following features:
(1) every software-processable multiplexing channel. As mentioned previously, TDMA system formation frequency time matrix, in each frequency into multiple time buttress, this matrix each point in a channel, base statoin control allocation, can provide a move for any telephone or the words business.
(2) using sudden pulse sequence transmission. The mobile station signal power launch is discontinuous, just within the prescribed time buttress within firing pulse sequence.
(3) transmission rate is high, adaptive equalization. Each time, the more software-processable contains wide frequency interval, transmission rate is high, but digital transmission brought time dispersion, make delay spread increase, so must using adaptive equalization techniques.
(4) transmission costs. Due to the TDMA into, make of received signal transmission time buttress machine in every sudden pulse sequences have to regain synchronization. In order to put a time buttress and another time buttress separate, protect time is a must. Therefore, TDMA system usually requires more than FDMA system overhead.
(5) for new technology is open. For example when voice coding algorithm is improved and reduce bit rate, TDMA system channel easily reconfigured to accommodate their new technology.
(6) sharing equipment of low cost. Since each software-processable for multiple clients, so TDMA system sharing equipment every customer's average cost compared with FDMA system is greatly reduced.
(7) mobile station design is more complicated. It FDMA system than the mobile station to complete more function, the need for a complex digital signal processing.
structure
TDMA frame definition
In GSM TDMA, frame is defined for each software-processable contain eight consecutive time buttress (TS0-7), the equivalent of FDMA system of a channel. In each time buttress, signal to sudden pulse series form sent.
Frame structure
TDMA frame of integrated structure is essentially in the wireless link repeat on physical frames.
(1) TDMA frame - each TDMA frame containing eight time buttress, whole frame duration approximately 4.615 ms, each time buttress containing 156.25 a code yuan, for 0.577 ms. Long time buttress
(2) TDMA complex frames (Multiframe) - multiple TDMA frame constitute complex frame, its structure has two kinds:
Continuous 26 TDMA frame constitute the complex frame, called 26 complex frame, cycle for use in a business channel and 120ms, with road control channel (with SACCH/TCH FACCH). Continuous 51 TDMA frame constitute the complex frame, called 51 after frame, for the control of channel (CCH), cycle for 3060/13 the hundredth 235.385 ms.
(3) TDMA super frames (Superframe) - more contiguous TDMA complex frame super frame, it is a continuous 51 x 26TDMA frames, a super frame lasts for 6.12 s.
(4) TDMA ultra-high frames (Hyperframe) it includes 2048 super-long-time frame, each cycle includes 2715648 a TDMA frame, the time period for 3 hours, 28 minutes 53 seconds 7.6 milliseconds. TDMA frame number is high frames (TDMA 2715648 a TDMA frame) for cycle Numbers. Why should use TDMA frame number? This is because the GSM system on customer's confidentiality is through to send information to the former encrypt messages to realize. The algorithm is calculated encryption sequence TDMA frame number is an input parameter, so each frame must have one frame number. A TDMA frame number, mobile station can judge control TS0 delivery on channel what type of logical channel.
application
TDMA (TDMA) is used in digital cellular phone system communication, it will each honeycomb channel is classified into three time, which can increase the amount of data channel load.
TDMA application in North America digital advanced mobile phone system (D - AMPS), global system for mobile communications (GSM) and personal digital cellular systems (PDC). However, the above all systems in realizing TDMA when was based on mutual in different ways. Another kind of different from FDMA and TDMA the reuse of the way for CDMA (CDMA). CDMA occupy the whole to designated service frequency range, while multiplexing all users occupies the information on the frequency range. TDMA originated on the Po - 54 statement as the standard. IS - 136 (IS - 54 version) IS the evolution of the cellular (TDMA 850MHz) and personal communication services (1.9 GHz) frequency American standards. TDMA also used in advanced digital wireless communication system (DECT).
characteristics
TDMA system has the following features:
(1) every software-processable multiplexing channel. As mentioned previously, TDMA system formation frequency time matrix, in each frequency into multiple time buttress, this matrix each point in a channel, base statoin control allocation, can provide a move for any telephone or the words business.
(2) using sudden pulse sequence transmission. The mobile station signal power launch is discontinuous, just within the prescribed time buttress within firing pulse sequence.
(3) transmission rate is high, adaptive equalization. Each time, the more software-processable contains wide frequency interval, transmission rate is high, but digital transmission brought time dispersion, make delay spread increase, so must using adaptive equalization techniques.
(4) transmission costs. Due to the TDMA into, make of received signal transmission time buttress machine in every sudden pulse sequences have to regain synchronization. In order to put a time buttress and another time buttress separate, protect time is a must. Therefore, TDMA system usually requires more than FDMA system overhead.
(5) for new technology is open. For example when voice coding algorithm is improved and reduce bit rate, TDMA system channel easily reconfigured to accommodate their new technology.
(6) sharing equipment of low cost. Since each software-processable for multiple clients, so TDMA system sharing equipment every customer's average cost compared with FDMA system is greatly reduced.
(7) mobile station design is more complicated. It FDMA system than the mobile station to complete more function, the need for a complex digital signal processing.
structure
TDMA frame definition
In GSM TDMA, frame is defined for each software-processable contain eight consecutive time buttress (TS0-7), the equivalent of FDMA system of a channel. In each time buttress, signal to sudden pulse series form sent.
Frame structure
TDMA frame of integrated structure is essentially in the wireless link repeat on physical frames.
(1) TDMA frame - each TDMA frame containing eight time buttress, whole frame duration approximately 4.615 ms, each time buttress containing 156.25 a code yuan, for 0.577 ms. Long time buttress
(2) TDMA complex frames (Multiframe) - multiple TDMA frame constitute complex frame, its structure has two kinds:
Continuous 26 TDMA frame constitute the complex frame, called 26 complex frame, cycle for use in a business channel and 120ms, with road control channel (with SACCH/TCH FACCH). Continuous 51 TDMA frame constitute the complex frame, called 51 after frame, for the control of channel (CCH), cycle for 3060/13 the hundredth 235.385 ms.
(3) TDMA super frames (Superframe) - more contiguous TDMA complex frame super frame, it is a continuous 51 x 26TDMA frames, a super frame lasts for 6.12 s.
(4) TDMA ultra-high frames (Hyperframe) it includes 2048 super-long-time frame, each cycle includes 2715648 a TDMA frame, the time period for 3 hours, 28 minutes 53 seconds 7.6 milliseconds. TDMA frame number is high frames (TDMA 2715648 a TDMA frame) for cycle Numbers. Why should use TDMA frame number? This is because the GSM system on customer's confidentiality is through to send information to the former encrypt messages to realize. The algorithm is calculated encryption sequence TDMA frame number is an input parameter, so each frame must have one frame number. A TDMA frame number, mobile station can judge control TS0 delivery on channel what type of logical channel.
application
TDMA (TDMA) is used in digital cellular phone system communication, it will each honeycomb channel is classified into three time, which can increase the amount of data channel load.
TDMA application in North America digital advanced mobile phone system (D - AMPS), global system for mobile communications (GSM) and personal digital cellular systems (PDC). However, the above all systems in realizing TDMA when was based on mutual in different ways. Another kind of different from FDMA and TDMA the reuse of the way for CDMA (CDMA). CDMA occupy the whole to designated service frequency range, while multiplexing all users occupies the information on the frequency range. TDMA originated on the Po - 54 statement as the standard. IS - 136 (IS - 54 version) IS the evolution of the cellular (TDMA 850MHz) and personal communication services (1.9 GHz) frequency American standards. TDMA also used in advanced digital wireless communication system (DECT).
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