Research On Random Access In LTE

With enhancements such as HSDPA and Enhanced Uplink, the 3GPP radio access technology will be highly competitive for several years. However, to ensure competitiveness for the next 10 years and beyond, a long-term evolution of the 3GPP radio-access technology needs to be considered. Hence, 3G LTE project is initiated, which introduce new air interface and some new techniques, in order to gain faster transmission speed, reduce access latency and improve system capacity.This dissertation mainly focuses on the design of Random Access Channel (RACH) in 3G LTE. The RACH is a contention-based channel used in uplink access, i.e. from UE (User Equipment) to Node B (base station). This channel can be used for several purposes. In different wireless system, the function of RACH differs. The RACH can be used to access the network, to request resources, to carry control information, to adjust the time offset of the uplink, to adjust the transmitted power, etc. It can even be used to transmit small amounts of data. Contention is the key feature of the random access channel. Many UE can attend to access a base station simultaneously, leading to collisions.In this paper, we mainly discuss current consideration about RACH in 3G LTE. From 1^st to 4^th chapter, summary of multiple access technology, RACH in WCDMA system and backoff schemes are given to achieve a better understanding about RACH in LTE. In the 5^th chapter, random access procedure is studied and a new procedure is presented, which can achieve better performance in terms of access delay. In the 6^th chapter, the resource allocation scheme is research and related conclusion is made. In the last chapter, a newly designed backoff algorithm, namely NRS algorithm is proposed. NRS algorithm is suitable for multi-channel system using GCL/CAZAC signatures as their preamble. Simulation results demonstrate that NRS can achieve very good performance in terms of throughput and delay.