TD-LTE key technologies and the introduction of strategic research

[Abstract] article as the starting point, to consider the introduction of TD-LTE strategy in the case of the coexistence of current TD-SCDMA network and 2G network, on the basis of the key technologies introduced TD-LTE, TD-LTE business background reduce the cost of network construction, and to enhance the efficiency of network utilization, and provide a reference for the LTE network construction.

[Keywords] TD-LTE business needs to introduce strategies, an overview of development in the mobile communications voice services remain, support for IP and high-speed data services has become a mobile communications system evolution in the direction of mobile data services is to promote the mobile communication technology the main driving force of development, TD-LTE as a quasi-4G technology to increase the data rate and spectrum utilization as the center of the target as the core technology, OFDM, flat network structure, so that the peak downlink rate of up to 100Mbps in 20MHz channel width. How The introduction of LTE networks has become the key issues of concern to operators.

2 TD-LTE business background of large-scale applications of the 3G network to promote the growth spurt of mobile data services, mobile data services revenue has become the focus of the business development of the carrier at the same time, the rise of mobile data services has brought a lot of new applications and new markets, these high-bandwidth mobile video, high-capacity file transfer, mobile Internet business led to greatly increased 3G network capacity and service bearing pressure.

User demand for new mobile services the following areas:

(A mobile Internet business development needs of existing 2G and 3G networks is still mainly based voice communication, support for high-speed mobile network with intensified the integration of the mobile network and the Internet, the Internet business is ported to the mobile Internet, The convenience of anytime, anywhere access to mobile Internet, so that people are increasingly expected to be obtained through the wireless network with the same rate and fixed Internet experience, increase demand for mobile data transfer rate is more urgent.

(2 video class business demand for mobile video services is one of the features of the 3G network business. Predicted future data services, video services will account for 28% of the total flow of the network, to become the second-largest flow business. Due to video class business for higher bandwidth requirements, the current 3G network support for video services have certain limitations, the need to further enhance the data transfer in order to better support the video as a form of expression of various services (such as multi-channel video business simultaneous interpretation rate, and network bandwidth.

(3 interactive business needs in various mobile value-added services, the business of interactive multi-Leisure business led slower transfer rates makes mobile office and business promotion. Along with the business and development of network technology further enhance the network rate, in order to better support large-capacity file transfer, mobile office, mobile video conferencing as well as in the life of the mobile payment, navigation, medical and other interactive business conduct.

(4 of Things development properties networking to achieve human and material things and things of communication and support of information technology, economic development and social improvement of the elements, the third change of the information society. It to the Internet based on the use of RFID technology, wireless data communications technology, a lot of communication between persons and things, things and things and information liaison to network more higher demand, and promote the development of next-generation broadband wireless access technology and popularity.

Due to a variety of new business for the growing bandwidth demand, and promote the continuous evolution and development of the wireless network. Rapid development of wireless broadband access technology has also brought the fierce competition in the market to meet these challenges, 3GPP R8 introduced to OFDM pick into the core technology, supports 20MHz system bandwidth, flat, efficient network architecture of LTE technology.

LTE technology needs of the target system including: higher data transfer rate and spectrum utilization efficiency, improve cell-edge data transfer rate, the wireless access network delay is less than 10ms, support variable bandwidth to support disparate systems to work together and enhance MBMS, reducing CAPEX and OPEX costs, reduce the cost of from R6 UTRA air interface and network architecture evolution, reasonable complexity, cost and power consumption, support systems and terminal enhanced IMS core network, as much as possible to ensure backward compatibility, When the contradiction with the improvement of system performance or capacity can be considered an appropriate compromise to support a variety of business types, the packet domain business (such as VoIP, the system should be able to provide the best services for low mobile speed terminal, should also support high mobile speed terminal, the system can work in symmetric and asymmetric band, the adjacent channel coexistence should support multiple carriers.

3 TD-LTE key technologies of LTE systems defined frequency division duplex (FDD and time division duplex (TDD two ways LTE TDD technology unified two frame structure originally proposed, based on TD-SCDMA frame structure for TD-SCDMA successful evolution to LTE and 4G standards laid the foundation for so called after the reunification of TD-LTE has been extensive attention, the industrialization process in the strong support of the operators has also been a significant development.

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(1 physical layer technology TD-LTE downlink uses OFDM technology, when the signal bandwidth is less than the channel bandwidth of each frequency component of the signal through the channel changes experience flat fading, the OFDM in a frequency domain of a given channel is divided into a plurality of narrow orthogonal subchannels, in each subchannel to use a sub-carrier modulation, and each subcarrier parallel transmission. OFDM can also be in a different subchannel transmission load on adaptively allocated against frequency selective fading or narrowband interference. because each subchannel peak right in the other sub-carrier spectrum at the zero from the other sub-channel interference is zero, and the carrier are orthogonal to each other, so they spectrum overlap, it will not only reduce the mutual interference between subcarriers, dynamic channel allocation, but also increase the spectrum utilization TD-LTE uplink consider the power consumption of the handheld terminal, SC-FDMA technology, using multiple different orthogonal sub-carriers, these sub-carriers in the transmission in a serial manner, to reduce the large fluctuations in the amplitude of a signal waveform during transmission, to avoid the band radiation, reducing the PAPR (peak-to-average ratio.

(MIMO MIMO technology using a plurality of transmitting antennas and receiving antennas, respectively, at the transmitting end and the receiving end, the signal passes through the transmission and reception of a plurality of antennas of the transmitting end and the receiving end, there is provided a different transmission capacity and spatial multiplexing gain. The same time, multi-antenna beamforming on the behavior of the spatial domain to suppress crosstalk, and enhance the signal within a particular range, this technique can improve the signal quality and can increase the transmission capacity. LTE basic MIMO technology acts under 2 × 2, 1 × 2 antenna array.

(3 flat network structure in order to simplify the network and reduce the delay, low delay, low complexity and low cost requirements, according to the network structure "flattened" decentralized "trends, changing the traditional 3GPP access network UTRAN in Node B and RNC two-layer structure, the upper layer of an ARQ, the radio resource control and the cell radio resource management functions in the Node B to complete the formation of the E-UTRAN of the "flat" structure, the access network by an evolved Node B (eNB and access gateway (aGW constitute the LTE eNB In addition to the functionality of the original Node B, also bear most of the functionality of the original RNC, including the physical layer (including of HARQ, MAC layer (including ARQ, RRC, scheduling, wireless access license , radio bearer control, access mobility management and inter-cell RRM.

E-UTRAN structure shown in Figure 1:
(4 wireless resource management downlink abandon macrodiversity technology, cell interference suppression technology to improve the edge data rates and system capacity, considering the system to switch between the switch and different frequencies, different systems.

4 TD-LTE introduced strategies With the industrialization of TD-LTE development and deployment of TD-LTE network is getting closer, and how to protect existing investments for existing 2G and TD-SCDMA, China Mobile, the market demand a planned, systematic introduction of LTE networks need to consider the key issues.

The second half of 2010, according to the timetable of the LTE industry process, planning scale experiment in 2012 to achieve large-scale commercial, China Mobile has been four TD network construction, TD network the LTE scale commercial has reached a certain scale, so LTE network must be staged in the TD-SCDMA network and then to look at the evolution path from the standard, the following two ways:

Ways: TD-SCDMA network is a direct evolution of LTE network

Ways: the TD network evolution to HSPA + upgrade to LTE.
In the actual standard path view, one of the standard ways to develop relatively smoothly, the manufacturers of the degree of support, but due to LTE in the physical layer and the network structure changes, evolution is not smooth enough for the original 3G network Investment protection is poor, Route 2 actually HSPA + standard-setting and the degree of industrialization behind LTE, HSPA + whether to introduce uncertainty, this pathway is essentially impossible to achieve a result, although the introduction of LTE for the original TD networks less use, but only consider the introduction of LTE directly from TD network evolution to LTE network.

In state of 2G/3G coexist for a long time, the LTE network positioning is the complement of the high-speed data services: 2G/3G network support for voice services and low-speed data services, the TD-LTE network to ensure that the vast amounts of data transfer as data services important supplementary means of this network positioning LTE network construction phase of the introduction of the following strategies:
(1 network construction early in the the data hotspot area construction LTE network there are two construction methods: the way a direct replacement of the original TD network equipment, 2G and LTE network coverage, the way to re superimposed on an LTE network LTE as this in two ways 2G or 2G/3G business supplement coverage, play a role in the triage area for indoor high-speed data requirements for LTE, focus on coverage, address the needs of high-speed data services.

(2 network construction interim gradually push forward the construction of LTE networks, demand urban LTE construction in the hotspots and part of the data, for the urban area LTE network to solve the needs of high-speed data services, or LTE and 2G coexistence, or for LTE and 2G / 3G coexist, coexistence of regional hybrid network for a variety of business needs, overlapping coverage.

(3 network construction late according to the development of data services, focused systematically and gradually expand the coverage of the LTE network hot spot areas in the data, LTE separate network, in other regions, 3G networks for voice services and low-speed data services to support LTE network to carry high-speed data services.

5 Conclusion As a quasi-4G technology, TD-LTE high-speed large-capacity data transmission for the important purpose of the key technologies and network structure has changed in the case of 2G/3G will coexist for a long time in a certain period of time, hybrid network for different positioning and business needs is a more reasonable strategy conducive to supplement the lack of 2G/3G networks in high-speed data services using LTE with the standard-setting process and the development of industry maturity, and TD-SCDMA network further mature the LTE network actual introduction of the strategy can be further refined.


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