LTE - A

LTE - A is LTE - on the abbreviation, follow-up evolution is LTE technology. LTE commonly known as 3.9 G, this explains the technical indexes have been with LTE 4G very close. Compared with LTE 4G, except largest bandwidth, uplink peak rate by two indexes is slightly lower than the other technical requirements 4G index has reached 4G standard requirements. But will the LTE 4G formal LTE into A technology integral design is more than the minimum requirements. 4G In June 2008, the 3GPP LTE - A completed the technical requirement of report, and puts forward the minimum requirements - A LTE downlink peak rate, 1Gbps: peak rate, 500Mbps uplink downlink peak spectrum utilization 15Mbps/Hz and achieved respectively 30Mbps/Hz. These parameters have far above the minimum ITU technology needs index, has many obvious advantages.

A major technical characteristics of LTE

In order to satisfy IMT - on the various requirements of 4G) (3GPP LTE - for index, on the (LTE - A) put forward several key techniques, including carrier polymerization, collaboration multi-point sending and receiving, relay transmission and multi-antenna enhancement, etc. LTE - A system of key technologies, including:

Carrier polymerization

LTE - A support continuous carrier polymerization and frequency band and bandwidth between non-continuous carrier polymerization, the biggest can aggregate bandwidth can reach 100MHz. In order to LTE - A contractor related technical principle diagram (3 copies) with initial efficient use of carrier, namely guarantee LTE terminal can access LTE - A system, each carrier should be able to configured with LTE, backward compatibility of the carrier, but also don't expel design only is LTE - A system using the carrier.

At present the 3GPP according to operator's demand identify 12 kinds of carrier polymerization application scenarios, including four as the key respectively involves FDD and TDD continuous and discontinuous carrier polymerization scene. In A study of LTE stage, carrier polymerization of related research highlights include the continuous carrier polymerization spectrum utilization ascension, downlink unsymmetrical carrier polymerization scene control channel design etc.

Multi-point collaboration

Multi-point collaboration is divided into more coordination scheduling and multi-point combined processing two categories, respectively applicable to different application scenarios, mutual between cannot completely replace. Multi-point coordination scheduling research is mainly focused on and multiple antenna beam fu gala should combine the solutions.

In 3GPP recently according to the preliminary evaluation, itu-t multipoint collaboration technology is the only can base statoin four antenna configuration conditions satisfy all the requirements of the technical index scene and improved obviously by ascending and descending system performance, and therefore more coordination of standardized schedule become 3GPP submitted 4G candidate scheme and facing the ITU evaluation center.

Relay transmission

Future mobile communication system in traditional honeycomb nets on the basis of urban hotspots capacity needed to optimize and in need to expand blind area, the subway and rural coverage.

Currently in 3GPP standardization work concentrates in low power can be deployed in pole or external wall of the relay transmission with inner return on its small volume, light weight, easy to location. Generally speaking, with inner return relay transmission, compared with the traditional microwave return relay transmission performance to low, but with inner return need not return frequency spectrum LTE outside and further to save costs, so both have their respective market demand and application scenarios.

Multi-antenna enhance

In view of the increasing frequency resource, more precious because antenna technology by extending space transmission dimensions and multiplied by multiple standards and channel capacity widely adopted.

Restricted by antenna height of channel, the influence of LTE - A system ascending and descending multi-antenna enhance the key difference. In A variety of LTE system based on more than downlink antenna mode, LTE - A downward requirements to support multiple antennas configurations specifications for the highest 8x8, meanwhile multi-user air multiplexing enhancement is considered standardized key. LTE - A relative uplink enhancement of LTE system focused on how to use the terminal multiple power amplifier, using the uplink launch diversity to enhance cover, ascending space multiplex to improve uplink peak rate, etc.

OFDM

OFDM by multiple carrier modulation (MCM), evolved OFDM technology is the realization of how sub-carrier scheme one way, its modulation and demodulation are respectively based on fast Fourier inverse transform (IFFT) and fast Fourier transform (FFT) to realize, is to realize the complexity, the most widely minimum a kind of many sub-carrier scheme. In the traditional frequency division multiplexing systems, the carrier of signal spectrum is no duplication, so that the receiver using conventional filters separation and extraction of different carrier signal. OFDM systems are data symbols modulation in transmission rate relatively low, with orthogonality between multiple and muck carrier on transmission. It allows sub-carrier spectrum overlap, the receiver using the subcarrier between the orthogonality recover the data sent. Therefore, OFDM systems have higher spectrum utilization. Meanwhile, in OFDM symbol between insert cycle prefixes, can eliminate due to multipath effect caused by the symbol, can avoid the interference between the multipath channel environment for protection and the influence of insert spacing between the orthogonality sub-carrier. This makes the OFDM systems are applicable to multipath wireless channel environment.

OFDM features anti-multipath decline of ability, spectrum efficiency high, OFDM channel will be divided into several son channel, and each child channel internal would is flat fading, can use based on IFFT/FFT OFDM fast realization method in frequency selective channel, OFDM receiver complexity than with equalizer's single carrier systems simple. With other broadband access technology can run in different, OFDM discontinuous bands, which will benefit multi-user distributed and diversity effect application etc. But OFDM technology of doppler frequency shift and phase noise is more sensitive, and peak average power than (PAPR).

Wireless relay

LTE system capacity is demanding, such capacity require a higher frequency. In order to satisfy the next generation mobile communication system of the high rate of transmission requirements, LTE - A technology introduced wireless relay technology. User terminals can through intermediate ap relay access networks to obtain bandwidth service. Reduce radio link space loss, increase signal-to-noise ratio, and improve the edge user channel capacity. Radio Relay technology including Repeaters and Relay.

On receipt of female Repeaters are of the base, rf signal directly on the rf forwarding, in the terminal and base station is not visible, but does not care whether in its purpose terminal coverage, therefore its role just amplifier just. Its role is limited to increase cover and can't improve capacity.

In Relay technology is based on the original site, through add some new Relay station (or called Relay node, Relay station), increase sites and the antenna distribution density. These new Relay nodes and original base station (mother base station) through wireless connections, and the transmission network without cable connection between, descending data base station arrive first mother, then to Relay node, Relay node again transmission to the end user, ascending contrast. This method is pulled close antenna and end users of distance, can improve the terminal link quality, thus improving the system of spectrum efficiency and user data rates.

Self-organization network

In order to pass the effective operation and maintenance costs (OPEX) and LTE network parameters and structure of the complicated pressure, the 3GPP borrow self-organizing network concept, in the R8 presents a new operation and maintenance strategy. This strategy will eNodeB as the self-organization network node, in which add self-organization function modules, complete cellular wireless network from configurations (get), since configuration optimization (top) and get all the operations (get). As the characteristics of LTE, companies have introduced in the R8 R9 finish demand, self-healing, from optimization ability of discussion.

LTE self-organization network with traditional IP Internet self-organization difference is, LTE requirements self-organization node may be interconnected besides, can of network by the optimization and the operation.

LTE - A evolution

LTE - on the mutual coordination with 4G process. March 2008 itu-t R, circulars issued to all members of the technical proposal, solicitation 4G candidate formally started 4G standardization. In July last year at the end of the RWP5D itu-t of dubai's meeting, ITU determines the 4G minimum requirements, including community spectrum efficiency, peak spectrum efficiency, spectrum bandwidth etc. Eight technical indexes, this will be the measure a candidate technology or become the key indicators of 4G technology.

But the 3GPP will with independent member's identity to the ITU submit oriented technology LTE - 4G on (LTE - A). Start from March 2008, the 3GPP began facing 4G research work, and formulate a detailed schedule, and the ITU time process close conjunction. In the RWP5D itu-t schedule has two key point: in October 2009 WP5D sixth conference over the collection of the candidate technology solutions 4G, by 2010 WP5D October ninth meeting determine 4G technology frame and main technical characteristics, to determine the 4G technical solutions. Around the two time points of its work, the 3GPP the deployment, have been in September 2008 RWP5D itu-t was submitted to the original version - A LTE and plans to 2009 respectively may and 2009 September submit complete version and the final version.

October 2009 14 and 21, international telecommunication union held in Germany dresden itu-t R WP5D workgroup sixth conference, LTE - on the finalists, including TDD and FDD both formats.

2010 October 20, the international telecommunications union (ITU wireless communications departments - R) 5 international mobile communications group (group) WP5D ninth meeting in chongqing determine LTE - on and 802.16 m in the new generation mobile communication (4G) international standard. The international telecommunications union in 2011 will finish before the end of 4G international standard proposal drafting works, early 2012 approval issued 4G international standard proposal