Interleaver Design and Throughput Enhancement Technique
In constrained interleaving (CI), the flexibility of the frame size is limited and the interleaving gain is lowered as the number of rows increases because of the row/column structure of traditional CI. We propose a single row constrained interleaving technique and apply it to turbo product codes (TPCs) to construct the single row constrained interleaving TPCs (SRCI-TPCs). SRCI-TPCs have higher interleaver gain and much more flexible frame size. Constrained interleaved coded modulation (CICM) maps coded bits on to a higher order constellation using reverse Gray coding (RGC) and a constrained interleaver to significantly improve performance. In this dissertation, CICM is applied to outer convolutional codes (OCCs) to construct CICM-OCCs. A CICM-OCCs interleaver is designed to achieve the highest possible minimum squared Euclidean distance (MSED) and virtual codeword is introduced to reduce the design complexity. Non-orthogonal multiple access (NOMA) allow different users of a muti-user system to share the same bandwidth while differentiating signals of different users in transmitted power. In this dissertation, similarly, a building blocks sparse constellation based orthogonal multiple access (BOMA) is proposed and applied to the downlink of the long term evolution (LTE). BOMA is constructed by use of the building block approach used in the design of multilevel code. Both NOMA and BOMA can enhance the overall throughput by additionally transmitting bits of a strong user when transmitting bits of a weaker user. However, they all have an issue that the performance of the weaker user suffers. To overcome this drawback, improved BOMA (IBOMA) is proposed by applying CICM-OCCs technique. It is shown IBOMA significantly lower the performance loss for the weaker user. Besides BOMA and IBOMA, another two throughput enhancing methods, throughput enhancing concatenated codes (TECCs) with block component code and simultaneous packet transmission (SPT), are proposed. TECCs are constructed by transmitting the explicit sequence with one inverted coded bit which is based on the implicit sequence. It is demonstrated that at high SNR, TECCs can increase the throughput of C by 37.5% without sacrificing the performance of both explicit and implicit sequence. SPT technique is proposed to transmit multiple streams to increase the throughput of a communication system. A SPT scheme employs multiple levels and employs multiple streams at each level above the first level. With proper constellation partitioning, higher rate code can be employed to the level-2 without sacrificing the overall performance; thereby the throughput can be enhanced. SPT technique can be used in high order constellation with 2 or more levels.