Research On Higher-order Modulation And Interference Coordination In LTE-Hi System

With the rapid development and the wide application of mobile communication systems, the type and the number of intelligent terminals are gradually diversifying, and the trafficload is also increasing in an unprecedented trend.The 3rd Generation Patenership Project (3GPP) leads and advances the fourth Generation mobile communication system,LTE-A, which improves the system data rate, frequency efficiency and capacity through a series of techniques such as Multiple Input Multiple Output(MIMO), Orthogonal Frequency Division Multiplexing(OFDM), Carrier Aggregation(CA). However, there are still a few problems for the application of the mobile communication system. According to cisco s estimation,80% of the traffic load will happen in indoor scenarios and hotspots in the future. Unfortunately, traditional macro cellular coverage can’t meet the traffic requirement in indoor and hotspot scenarios. To solve the problem,3GPP has proposed small cell enhancement in Release 12, namely LTE-Hi.LTE-Hi is a kind of small cell networking technologies based on LTE-A, which deploys base station (BS) with lower transmit power in indoor and hotspot scenarios to meet the demand for different kinds of user equipment (UE) services and to realize the increase of the system capacity. Due to the particularity of LTE-Hi deployment scenarios, this paper considers introducing different technologies from the evolution of LTE-A, such as 256 QAM for the indoor scenario and interference coordination for the hotspot scenario. The main contents in this paper are as follows:Based on the built link and system simulation platform, the UE SINR in indoor scenarios is compared with that in Macro scenarios. It is proved that the SINR in indoor scenarios is better due to the good channel condition. Then, a soft demodulation algorithm based on border distance decision. is deduced and applied in the link simulation platform. The relationship between SINR and BLER using 256QAM with different code rates is simulated and the spectrum efficiency is calculated when BLER equals 0.1. Moreover, the 256QAM gain margin is obtained, which confirms the feasibility of 256QAM applied in indoor scenarios. Finally, the throughput of 256QAM with different EVM index is evaluated and is compared with the 64QAM. System throughput in different indoor scenarios is also evaluated using different TBS and modulation methods. The result shows that 256QAM can bring the better throughput gain to UE in indoor scenarios.On the other hand, the interference of UE in hotspot scenarios is investigated, which presents that the interference is severe in the case of the larger number of small cell in a cluster. This paper analyzes three interference coordination schemes in hotspot scenarios from time domain, power domain and small cell on/off aspects.Different principles of the three interference coordination schemes and corresponding detailed implementation process are introduced Besides, the UE SINR, throughput, system outrage probability, network energy efficiency are all evaluated in the system simulation platform. The results show that interference coordination schemes based on small cell on/off can bring more gains for small cell clusters in hotspot scenarios.