Research On Code Modulation And Constellation Correlative Techniques

With the rapidly increasing of mobile multimedia services, how to insure the data rate and improve the performance of the wireless links has become the key problem in the future mobile communications. High order phase modulation technique can improve the spectral efficiency. But deteriorated bit error rate limits the modulation order to be higher, which caused by decreasing Euclidean distance between symbols of large constellation, the constellation mapping technique can improve the performance of system with increasing the Euclidean distance between symbols proposed in this paper; In order to improve the reliability of system, we rearch the code modulation and constellation combine with cooperative techinique for achieving the diversity gain and code gain. In order to improve the reliability deeply, we rearch the code modulation and constellation combine with the network coding and cooperative technique for reducing the system outage probability remarkably and obtain a higher diversity gain without occupying more bandwidth. This dissertation deeply does some research on code modulation?constellation mappings cooperative diversity and network coding techniques.This dissertation does some work for the code modulation and constellation correlative techniques, the main contributions of the dissertation are as follows:(1) In order to obtain the optimized multi-dimensional constellation mapping scheme and decrease the complexity of multi-dimensional constellation mapping, a new QPSK scheme for multi-dimensional constellation is proposed. Based on analyzing the relationship between Hamming distance and Euclidean distance of QPSK symbols for bit interleaved coded modulation with iteratively decoding (BICM-ID) systems, we find that the Euclidean distance between that pair of signals whose labels differ only in one bit is obtained from Hamming distance and give the value of optimized hamming distance. The proposed method takes the optimized Hamming distance as rule of designing and optimizing multi-dimensional mapping of QPSK constellation, it gives the search steps and result of multi-dimensional mapping. The proposed method achieves the better performance than the conventional two-dimensional and multi-dimensional mapping of QPSK constellation at high SNR in BICM-ID system; Due to the Extrininsic Information Transfer Chart (EXIT) only shows the extrininsic information performance of the irregular modulation mapping schemes under fixed signal to noise ratio (SNR) in BICM-ID system, a new method based on EIXT is proposed. The difference with EXIT chart analysis method is the proposed method shows the relationship between the extrinsic mutual information and the whole signal to noise ratio region (EMI-SNR). The proposed method can effectively choose the different irregular modulation mapping schemes in the different signal to noise ratio region and can roughly evaluate the scope of system bit error rate curve in BICM-ID system.(2) In order to deeply improve the performance of system, we rearch the code modulation and constellation mapping technique combine with cooperative diversity technique, coded cooperation can acheieve not only the diversity gain but also code gain. A new coded cooperation scheme with 8PSK modulation using LDPC codes is proposed for high spectral efficiency. Two users in the cooperative process transmit the data using 8PSK modulation over two frames.The transmitted information is stored if it is not be decoded correctly by the cooperative partner over the first frame based on HARQ, then the stored information and the next transmitted information are together decoded by cooperative partner until the transmitted information over the first frame is decoded successfully, it improves the accuracy of decode due to adding parity information. Then it transmits the parity information of his cooperation partner over the second frame for diversity. The ayalysis shows that the proposed method obtains more diversity gain and code gain than conventional code coopeation; A high modulation coded cooperative method is proposed for increasing the information in second frame of coded coopeation and high spectral efficiency. The new proposed method process takes place over two frame and two users when it has full diversity. Each user transmits the information using BPSK in the first frame and using 8PSK or 16QAM modulation in the scond frame. In order to compensate the loss of high-order modulation, in the second frame each user recodes the information received from the cooperative partner in the first frame. The proposed method improves the diversity gain with the more information trasmmitted in the second frame.(3) A network coding scheme based on coded cooperation is proposed to raise the diversity gain and high throughput. Take an example that there are two users in the cooperative process combined with BICM, each user transmits the data to its partner and destination using channel coding, modulation and constellation mapping over two frames. If the user can decode its partner's information correctly in the first frame, it will transmit the combination of its own and the partner's additional parity bits through network coding in the second frame. Analysis and simulation show that the proposed method can reduce the system outage probability remarkably and obtain a higher diversity gain.