Research On Technology Of Joint Coding And Modulation Diversity In IMT-Advanced MIMO System

As the standard for future mobile communication, LTE, WiMAX and 802.11 series standards for WLAN all have very high performance requirements. For example, the bandwidth should be bigger than 20MHz, the peak data rate should be higher than 50Mbit/s, also the frequency utilization should be greater than 2.5bit/s/Hz. For future communication systems, in link layer, how to explore new and more effective technologies to improve overall performance on the basis of the existing key technologies as channel coding, MIMO, OFDM has been a hot spot in recent years.If the transmit path is in a deep fading, no communications technology can guarantee zero error rate. One method to improve performance is to ensure that there are a number of signal paths for the symbols, and each path is independent in decline. So if there is a strong path signal, reliable communication could be realized. This technique is named diversity. Time diversity can be achieved through channel coding and interleaving. Encode the information symbols and then separate them into different coherent cycle, so that different parts for one code word could experience independent fading. Similarly, if the channel is frequency selective and frequency diversity can also be used. If there are multi-antennas far enough with each other for transmitting or receiving, space diversity can be achieved.Besides time diversity, frequency diversity and space diversity there is another diversity technology——modulation diversity, which could be applied with the above diversity together and combine the technology advantage to create a novel method, that is joint coding and modulation diversity. This method will not sacrifice the frequency efficiency or add the extra power load to realize the high performance in defeating fading and interference. Therefore the overall achievement could be better than bit-interleaving coding modulation techniques, which is especially necessary for future mobile communication systems.For its application in communication system, we study the technology in MIMO system, MIMO-OFDM system for LTE downlink transmitting and wireless local network with 802.11AC standards. From the simulation result, we could draw the conclusion that this technology could obtain over 10dB gain compared to traditional BICM in higher coding rate. So it is believed this technology is very promising in different kinds of communication system.