The Research And Analysis On Link Technologies Of 3GPP LTE

To encounter the challenge of the WiMAX, The 3rd Generation Partnership Project start off the plan of the long term evolution, what can be called Quasi-4G Technology, on the basis of 3G technologies. On May 25 in 2010, Ericsson and TeliaSonera launched the 1st commercial LTE site of the world in Stockholm, which marked the LTE has become a reality. At the same time, China begun the creation of pilot network, Japan began issuing licenses LTE, Europe and the United States began the Process of network deployment. In 2010, the TD-LTE, which was pushed by China government, present at the Shanghai Expo and it can get 100m/s downlink,50m/s uplink peak rate in theoretical. It mean that Communication speed of mobile communication system has unprecedented. LTE make OFDM and MIMO as the wireless transmission technology and use the whole IP system architecture and the flat network structure.To research the link Technology of the LTE system, we consider the frame structure and Pilot structure at first, then we get research on MIMO and OFDM, which are the key technology of LTE, and made a principle of analysis of them. At last we made a principle of analysis on the feasibility of MIMO-OFDM which are combination of MIMO and OFDM and put the advantages together.To be continued, we study multiple access technology, which use SC-FDMA in the Uplink and OFDMA in the Downlink. By Establishing the physical model, the simulation show that OFDMA is batter at the link performance and wicker at PAPR. On the contrary SC-FDMA does batter in PAPR but short of link performance. The Uplink needs batter performance on PAPR to save the energy for UE and the Downlink should not save the eNB's energy but do much batter on link performance, so 3GPP LTE choose the SC-FDMA as the Uplink Multiple Access and OFDMA as the Downlink Multiple Access.LTE requires that the Uplink and Downlink transmission rate should achieve 50Mbit/s and 100 Mbit/s respectively and UE should get good communication in high-speed environment, which has greater improving than the previous access technology and take a great challenge to this mobility management of the system. The paper studied and analyzed the process of the UE access to the core network through eNB nodes and focus on the synchronization and cell search process, especially on the Switch process. In this reseach, we would discuss the Switch process among different sectors in an eNB and among different access technology of 3GPP and non-3GPP.Finally, the network congestion control is also a difficult problem as the LTE system architecture is all-IP flat network structure. In the traditional network congestion control algorithm, TCP congestion control is represent for the source congestion control technologies and IP congestion control for link congestion control technologies. There are a lot of sophisticated control algorithms. At the same time, it should be noted there are also lots of templates combining with the advanced control theory. On the basis of the characteristics of the wireless TCP networks, this reseach would draw mature TCP/IP control algorithms, which is suitable for the wireless TCP congestion control algorithm in LTE, so that network performance should get greater improving.