System-Level Simulation In LTE

Compare to the last generation of wireless communication system, LTE adopts newtechnologies such as OFDM, MIMO, HARQ, and link adaption. Introduction of newtechnologies would certainly improve the two key performance metrics of wirelesscommunication, i.e. frequency efficiency and power efficiency. However, quantitativeanalysis and expression remain to be established in order to understand to what extend can thenew technologies improve system performance. Generally, there are two ways of quantitativeanalysis. One way is to seek for a closed form solution of performance improvement from atheoretic perspective, which is often used in evaluation of local improvement of a certainalgorithm. The other way is to perform system-level simulation, and assess the overall systemperformance. In the performance evaluation of LTE system, due to the introduction of manynew technologies, it is difficult to acquire a closed form solution of system-level performanceimprovement. Hence, system-level simulation plays an important role in analysis of complexsystems such as LTE, and it has been widely used in the enterprise community.In this thesis, we start with an introduction of LTE system architecture. We use C/C++tobuild the simulation platform, which has the mechanism of message-driven. We simulatedmany kinds of events in real system, and we perform these tasks in real time. By doing so weavoid the shortage of MATLAB, which is a descriptive language and very slow when dealingwith system-level simulation, and we avoid the low efficiency of polling. We abstract thephysical layer in the simulation, including modeling of MIMO wireless channel, abstractingof MIMO transmission modes, and modeling of LTE physical channel and HARQ gain. Wealso modeled and implemented wireless data-link layer, including PDCP, RLC, and MAC. Asto HARQ retransmission of cell-edge cooperative user, we compare cooperativeretransmission scheme and non-cooperative retransmission scheme, and get an insightfulconclusion, which also lays foundation of future research of LTE. By building this LTE system-level platform, the proposals submitted by our groupconcerning HARQ retransmission and codebook designing are supported with strongsystem-level evaluation, and the proposals are accepted by the LTE standardization subgroup,which gives us stronger motivation for future research. This simulation platform not onlygives us a thorough understanding of LTE performance analysis, but also offers a testplatform when introducing new module-level technologies. The platform makes performanceevaluation evolves from module-level to system level, which has much significance.