Research On The Key Technologies And Systemarchitecture Of TD-LTE System

LTE is a standard defined by 3GPP for broadband mobile communication networks. It is a technology between 3G and 4G, which has been included in the 3GPP R8 official standard. As a part of the R8 standard, LTE TDD, which is called TD-LTE in domestic, is a follow-up to the evolution of TD-SCDMA standard. With the rapid growth of mobile Internet services, it is essential to discuss the key technologies and the structure of TD-LTE system.The architecture of LTE is a revolutionary change from 3GPP. Comparing to 3GPP UTRAN, a single-layer structure consisting of eNodeBs is used in LTE network, so the network structure is flat. There are many new technologies are introduced to the physical layer of LTE air interface, including OFDM, multi-antenna technology and TDD/FDD frame structure. OFDM is an orthogonal multi-carrier technology, and its carrier interval is 15KHz in LTE system, symbol rate being 15KS/s as mentioned in the previous literatures. However there is no detail about the relationship between the two in those literatures. The relationship for them is discussed in this article. Furthermore, the performances of LTE TDD/FDD physical layers based on the frame structures are discussed in this article.As the carrying capacity of the physical layer determined by the above mentioned technologies, the utilization of this capacity is to a large extent determined by the MAC layer packet scheduling algorithm. Several traditional and modified PF algorithms based on the single-service scenario are introduced in this article, and a new LSM-PF algorithm is proposed to achieve higher system throughput. Moreover a number of QoS-aware algorithms are discussed in this article. The performances of these algorithms are not satisfactory in LTE multi-service scenario. Therefore, two new algorithms, Ag1 and Ag2 are proposed. Ag1 and Ag2 algorithms are based on M-LWDF algorithm and meet the minimum bit rate requirement of different user's service by restricting and compensating the number of RBs to different user respectively. A method of logically updating the first packet delay of a service queue is added in the Ag2 algorithm. It helps to keep the balance of the length of the waiting queues, which is necessary for a better meet of the packet delay requirements. So the Ag2 algorithm achieves a higher system throughput. At last all the algorithms discussed in this article are analyzed in a MATLAB simulation platform.