Research On PDCCH Blind Detection Technology For Cellular And D2D Heterogeneous Systems

Cellular and D2D heterogeneous systems have been a hotspot of molobile communication research in recent years for the advantages of combining LTE and D2D communications, as to effectively reduce the workload of base stations, improve utilization of spectrum efficiency and enhance network performance. This paper focuses on PDCCH blind detection technology. By analyzing characteristics of the systems and deficiencies of existing algorithms, it proposes optimizaton algorithms to effectively reduce the computational complexity and improve the system performance.First, this paper introduces the downlink of LTE and D2D sytems,reviews LTE system frame structure, downlink physical channel and downlink time slot structure. The process of PDCCH transmitting and receiving is summarized. Traditional CCE resource allocation method and blind detection algorithm are described. The similarities and differences of LTE and D2D systems are compared, and the characteristics of D2D blind detection are pointed out.Next, the process of PDCCH blind detection in LTE system is thoroughly studied. Based on traditional blind detection method, two opitimization algorithms are proposed. Alogrithm 1 first detects the aggregaton level of the last result, then carries on the next step detection according to the increase or decrease of SNR. Algorithm 2 analyzes the SNR first and then use the last detection result to carry on the examination.This paper also analyzes multiple DCI cases. The performances of three algorithms at different SNR are compared by simulations, and the results show the proposed algorithms have significant improvement.Then,the PDCCH blind detection technology of LTE and D2D heterogeneous system is thoroughly studied. Based on the similarities and differences of PDCCH blind detection between LTE and D2D systems introduced in Chapter 2, the steps and methods of total-blind detection of D2D users are described in detail. By analyzing the shortcomings of existing algorithms, this paper proposes a CQI-based CCE resource allocation total-blind detection algorithm. This algorithm defines the rule that the sender allocates CCE resources such that the receiver can directly judge the position and aggregation level of the DCI, and the number of Viterbi decoding times is the least. The performance of the algorithm is analyzed in detail and verified by comparing the effect of whole-block and residual-block, the number of users and CCEs, the influence of public space and user-specific space and the distribution of user SNR.