Research On Subcarrier Optimization And Detection Algorithm For Space-Frequency Joint Index Modulation System

As a typical application of 5G communication technology in intelligent transportation system,Internet of vehicle communication technology has become an important support for autonomous vehicle.However,there are two major challenges that vehicle-to-vehicle communication needs to face.One is the complex and the open communication environment,and the other is the demanding real-time transmission requirements.Therefore,how to make full use of space-time-frequency resources is a hot research topic in current Internet of vehicle communication.This paper mainly studies index modulation in spatial and frequency domain.This paper mainly introduces spatial domain index modulation(spatial modulation)and frequency domain index modulation(OFDM-IM),both of which use index bits to compensate for the loss of spectrum efficiency caused by idle antennas and subcarriers.Index modulation can also avoid inter-antenna interference and inter-subcarrier interference.It has flexible parameter configuration,and is expected to become one of the advance mobile communication development technologies in the future.The main work is as follows:1.In order to make full use of the existing communication resources,a two-dimensional space-frequency joint index modulation system,SM-OFDM-IM,is proposed by combining spatial modulation with frequency index modulation.The advantages of SM-OFDM-IM system are as follow: the sparsity of the transmitted symbols reduces the sensitivity to frequency offset,inter-carrier interference and inter-antenna interference.Similar to OFDM-IM,parameter configuration of SM-OFDM-IM system is very flexible,and the bit error performance has been significantly improved,too.2.Aiming at the redundancy of subcarrier combination in SM-OFDM-IM system,the mapping relationship between index bit and subcarrier is modified.The optimal subcarrier combination is selected in terms of maximum Hamming distance and least inferior combination.Then the optimal combination is mapped to the corresponding index bits according to the optimal mapping criterion,which can further improve the bit error rate of system.3.To reduce the detection complexity in SM-OFDM-IM system,this paper proposes a partial maximum likelihood detection algorithm based on sorting symbol energy.The main idea of this algorithm is to sort the energy values of equalized symbols on each subcarrier according to their size.And then set the number of candidate subcarriers for partial maximum likelihood detection.The algorithm can narrow the traversal range of the traditional maximum likelihood detection algorithm,and can achieve the trade-off between complexity and performance by adjusting the number of candidate subcarriers.The proposed algorithm has the value of practical application certain application significance.