The Key Technologies In IDMA Communication Systems And Applications Of IDMA In Cooperative Wireless Communication

Recently, Interleave-Division Multiple-Access(IDMA)is a popular research topic in wireless communications. In addition, the research on cooperative communications is focused by scholars in the world now. This thesis dedicates to research the key technologies in IDMA systems and applications of IDMA in cooperative communications. There are the following four aspects that this thesis focuses on: IDMA interleaver design; applications of IDMA in the multiple source-destination pairs and multiple common relays cooperative network; Relay-assisted partial packet recovery with IDMA method in wireless network; Applications of chaos in IDMA secure communication.The main contributions of this thesis are as follow:1. A new IDMA interleaver design based on linear congruences is proposed for multiuser IDMA systems.The concept of interleaver sets based on complete residue system is proposed at first, and then apply this interleaver design concept into IDMA interleaver design based on linear congruences. Our design has the low complexity and fits the scenario of IDMA systems. The proposed interleaver inherits the advantages of pseudo random interleaver and nested interleaver. It requires less memory than pseudo random interleaver, and it is able to generate each user's interleaver independently and simultaneously compared to nested interleaver. The complexity of the design algorithm is low because the basic component is linear congruences, and the amount of information required for interleaver synchronizations between transmitter and receiver. The simulation results show that the performance of proposed IDMA interleaver is better than pseudo random interleaver's when the number of user is large.2. A cooperative communication scheme based on IDMA is proposed for the network model, which consist of multiple source-destination pairs and multiple common relays. The proposed scheme adopts decode-and-forward (DF) and amplify-and-forward (AF) protocols. IDMA iterative multiuser detection is utilized to cancel the interference and achieve diversity gain. In the proposed scheme,multiple sources can share a group of relays to perform the cooperative communication when the number of relays is limited in the network. Relay nodes can transmit the signals at the same time. Compared to TDMA and FDMA, it saves the number of time slots and orthogonal frequencies. Meanwhile, destinations can cancel the interference from the undesired sources and regain the diversity from multiple relaying signals with a low complexity receiver. The simulation results show that the proposed scheme can provide desireable diversity gain. Different locations of the common relays have different performance of cooperative transmission. In addition, this thesis provides simulation results on the effect of sources and relays'transmit power allocations on the performance. It can be utilized to design an adaptive protocol selection scheme for the case of constrained the power allocation and relays'locations. The proposed scheme is flexible to select the cooperative protocols, the destination receiver doesn't need extra design when the transfer between DF and AF protocol.3. Relay-assisted partial packet recovery with IDMA method scheme is proposed. In the proposed scheme, relays in different locations assist to retransmit the multiple sources'partial packets with IDMA so that diversity gain is achieved in retransmission. IDMA iterative multiuser detection is applied to receive multiple sources'partial packets with different sizes. To minimize the cost of feedback request, a recursive algorithm of cost-based evaluation is provided for feedback request stratedgy. The simulation results show that the proposed scheme outperforms the traditional ARQ.4. A cross-layer asymmetric interleaver design for secure IDMA communication scheme is proposed by combining Diffie-Hellman key exchange protocol and discrete chaotic map. In the proposed scheme, IDMA system can perform the secure communication by an asymmetric interleaver design, which integrates the pseudo random interleaving function and encryption. The random-like property and the sensitivity of intial value of discrete chaotic map are utilized in this scheme. In addition, Diffie-Hellman key exchange protocol is combined into the proposed scheme so that the interleaver at the physical layer can be configured. The simulation results show that the proposed interleaver design not only has the same performance with the pseudo random interleaver, but also is capable of secure communication.5. To make chaotic secure communication practicable, a real-time chaotic secure communication system scheme is proposed and implemented by software. In the proposed scheme, to address the small key space problem of chaotic encryption, the DES which has sophisticated key space design is adopted. And RSA is used to encrypt the private key of chaotic encryption and DES so that assure the security of the synchronization key for chaotic secure communication. The experiment results of the software show that the proposed real-time chaotic secure communication system scheme is practicable and useful.