Research On Interleave Division Multiple Access In The Future Wireless Communications

Along with the worldwide implementation of3G network, as well as the emerging of LTE based4G network, the wireless mobile communication system is now moving towards B3G era. Nevertheless, the desire for better wireless service never stopped growing. On the one hand, the subscribers expect even higher data rate and more reli-able transmission, in order to support the demanded wireless services which are much more diverse than ever before. On the other hand, there are more and more subscribers would like to join the networks, with the number of terminal equipments kept on in-creasing explosively. Unfortunately, the wireless resources, i.e.. power and spectrum have been already extremely explored and left limited space for the improvement of wireless service. As a result, The design of high-spectral and power efficient multiple access scheme is of great importance to support more users sharing the limited wireless resources and enjoy the enhanced quality of services.Interleave Division Multiple Access (IDMA) is one recently proposed multiple access scheme which has drawn a lot of research interests. In IDMA system, the different inter leavers are employed as the only identities to distinguish different users. At the receiver end, an iterative multi-user detector is proposed, which can achieve the single-user performance with very low complexity involved. Hence, IDMA owns the ability to support a large number of users while at the same time, maintains the high spectral efficiency and low detect complexity. Furthermore, the concept of IDMA can also be applied to form the so-termed Superposition coded modulation (SCM), which is a helpful coded modulation scheme for the individual users to improve their transmission performance.In this thesis, we focus on the research of IDMA related multiple access scheme, as well as the transmission techniques for the future wireless communications. Started from this purpose, we first focus on one special case of IDMA, i.e., Grouped OFDM-IDMA (G-OFDM-IDMA)system. In order to maximize the system spectral efficiency, we proposed the bipartite matching based user grouping algorithm for such a system. Then, we pay our attention to SCM, the extension of IDMA, and design a novel MIMO transmission scheme which combines the advantages of SCM and Spatial Modulation (SM). After that, we perform the research on the adaptation of IDMA in different future communication scenarios, and give two IDMA based reference models for Feintocell and cooperative communication networks, respectively. Specifically, the main research contents and contributions of this thesis are as follows:· A bipartite matching based user grouping for grouped OFDM-IDMA. By divided the subcarriers and users into several groups, G-OFDM-IDMA can fur-ther reduce the complexity of detection process. However, the grouping operation also introduce the problem of resource allocation. How to properly allocate the sub-carriers into different groups and assign different users to these groups to achieve the optimum performance is a challenging issue.Aiming at maximizing the system capacity, we adaptivcly distribute users among the pro-allocated subcarrier groups according to their respective channel conditions. Using the notion of SNR evolu-tion function, we first analyze the achievable capacity of the system and formulate the optimization problem as a weighted bipartite matching problem. Due to the analytically intractability of the SNR evolution function, we opt to use either the worst-case or best-case bound of the achievable capacity to approximate the origi-nal problem. Then Kulm-Munkres method is employed to solve the approximated problems. The performance of the proposes scheme with different approximations is evaluated by both theoretical analyses and simulations. Results show that with our proposed algorithm, the system capacity is markedly improved and is very close to the optimum upper bound.· Superposition coded modulation aided spatial modulation scheme for MIMO system. By assigning multiple interleavers to one inelivielual user, the SCM signal can be generated by weighted sum of parallels of independent data streams of such a user. On the other hand, Spatial modulation (SM) is a spa-tial multiplexing scheme which utilizes both the signal constellation and antenna index to convey information. In our research, we propose a newel scheme where superposition coded modulation (SCM) is eniployeel to modulate the information onto the constellation points. We also develop a low complexity two-level iterative detector for our proposed SCM-SM system. Analysis and simulations demonstrate that SCM-SM significantly outperforms the original SM system with the same data rate, while maintaining the comparable complexity to the latter.· Research on the applications of IDMA in the future wireless communi-cation networks. The future wireless systems would be a heterogeneous network where different scenarios would co-exist within the same location. As a result, it is of great importance to design the multiple access schemes according to the features of these different, scenarios. In this part of work, we focus on the application of ID-MA in two different scenarios, namely, Femtocell and cooperative communications. For femtocell, we propose a novel G-OFDM-IDMA based downlink transmission scheme. To avoid the cross-tier interference, we assign the femto users and marco users into different subcarrier groups for transmission. IDMA is used to mitigate the co-tier interference within the same group of users. we investigate the per-formance of the proposed scheme in terms of spectral efficiency and BER. Both theoretical analysis and simulations indicate that with the assistance of femtocell and grouping, the proposed scheme achieves better performance compared with the traditional OFDM-IDMA systems, while at the same time maintains an even lower complexity at the user terminal than the latter. For cooperative communica-tion scenario, we propose a novel superposition modulated cooperative scheme for the scenario with multiple source nodes. To achieve the cooperation, the transmis-sion of each node is a superimposed signal consists of its own information and the estimated data of nodes in the previous time slot. The subset partition is also an-alyzed and the ways to get a tradeoff between performance and system complexity is shown. Simulation results are finally provided to show the performance of the proposed scheme.