Research On Cooperative Diversity Of CDMA Wireless Network

Under the multi-user environment, cooperative diversity makes a number of single-antenna terminals share each other's virtual antenna array antenna by relaying their information, by which it achieves spatial diversity. Cooperative diversity is a promising collection of space technology which uses distributed method to achieve MIMO technology and helps MIMO find a new way in the application of small mobile terminals. Cooperative diversity can be as effective as MIMO in the use of space resources to improve the performance of communications systems which include increasing the capacity of communication system, higher the data rate, combating fading effectively, lower the outage probability of service, increasing the Quality of Service and reliability, and so on.CDMA is the most competitive and promising wireless multiple access technology in the new generation of mobile communications and personal communications. However, the near-far effect affects the communications between nodes seriously in the CDMA wireless network. Applying cooperative diversity to the CDMA wireless network can achieve transmitting diversity gain in distributed method which can help the mobile terminals under deep decline to work normally. Thereby cooperative diversity can overcome the influence of the distance effectively. Therefore the study of cooperative diversity in CDMA wireless network has its'important theoretical significance and application value. In this paper, we carry out an in-depth research on the protocol of the CDMA wireless network to establish and performance analysis which is based on the characteristics of cooperative diversity.Main contents of the thesis:Charter 1 introduces the concept, separation and advantages of cooperative diversity, gives the research status on cooperative diversity, and analyzes the significance of the application in the CDMA wireless network. Finally introduces the researching purpose and main contents of this thesis.Charter 2, firstly, introduces the basic knowledge about the wireless channel environment, several traditional diversity technologies and the combining method of diversity. Then it expounds the system model of cooperative diversity and the time division channel allocation scenario, and it mainly focuses on: Fixed Amplify-and-Forward and Decoded-and-Forward, Selective Decoded-and-Forward and Incremental Amplify-and-Forward. The four protocols are based on TDMA system. It analysis the various approximately protocol expression and diversity order of the outage probability when the SNR value is high. It compares the performance of these protocols. The simulation results and theoretical analysis of the outage probability indicate that protocols can provide the full diversity gain except the Fixed Decoded-and-Forward protocol. The simulation results, which are about the diversity order, show that there is a tradeoff between the order of diversity and the efficiency of the normalization of the frequency spectral.Charter 3 proposes a Decoded-and-Forward protocol which is on cooperative diversity of the CDMA wireless network. Supposing the protocol works under the condition of single relay nodes, then we establish the system model of the protocol. We analysis the outage probability of the protocol which is in frequency non-selective fading environment, and the average error rate, diversity order which is in frequency non-selective fading and frequency selective fading environment. We suppose that the protocol meets the total power network limit and doesn't use redundant resources and the spreading code doesn't affect other nodes communication conditions. The simulation results and theoretical analysis which are about the outage probability show that the diversity order is 2. At the same time, it shows that cooperative diversity decreases the possibility of interrupting the source node and the average probability of bit error rate, especially when the signal noise ratios are the same. The theoretical analysis of the diversity order shows that when the SIR is higher, the protocol can have a full diversity gain.Charter 4 proposes that two-node mutually cooperate, and space-time coding which is on cooperative diversity of CDMA wireless network protocol. Then we establish the system model of the protocol. We research and analysis the outage probability of the protocol which is in frequency non-selective fading environment, the average error rate, and diversity order which is in frequency non-selective fading and frequency selective fading environment. We suppose that the protocol meets the total power network limit and doesn't use redundant resources and the spreading code doesn't affect other nodes communication conditions. The simulation results which are about the outage probability and the average BER show the theoretical analysis is correct. Finally it shows that space-time coding cooperative diversity is more excellent in decreasing the outage possibility of the source node and the average probability of bit error rate than the non-cooperation. The theoretical analysis of the diversity order shows that when the SIR is higher, it can have a full diversity gain.Charter 5 proposes that two-relay take part in cooperative the source node, we propose the two-relay Decode-and-Forward cooperative diversity protocol. Then we establish the system model of the protocol. We analyze the average error rate both in frequency non-selective fading and frequency selective fading environment. We propose that the protocol meets the total power network limit and doesn't use redundant resources and the spreading code doesn't affect other nodes communication conditions. The simulation results show that the two-relay Decode-and-Forward cooperative diversity protocol is more excellent in decreasing the average probability of bit error rate than the non-cooperation. In charter 6, the paper summarizes contents of this thesis.The innovative work of this paper is as following:1. Propose a single-relay node which involves cooperation in a CDMA wireless network Decode-and-Forward cooperative diversity protocol. We establish a system model of the protocol, and derive expressions of the outage probability under the frequency non-selective fading environment, and the average bit error rate and diversity order under the frequency non-selective fading and frequency selective fading environment.2. Propose a space-time coding of the CDMA wireless network cooperative diversity protocol which is based on two-node mutually cooperating. We use space-time block codes to establish the system model of the protocol, and derive expressions of the outage probability under the frequency non-selective fading environment, and the average bit error rate and diversity order under the frequency non-selective fading and frequency selective fading environment.3. Propose the two-relay Decode-and-Forward cooperative diversity protocol in which two relay nodes take part in cooperation the source node. We establish the system model of the protocol, and derive expressions of the average bit error rate under the frequency non-selective fading and frequency selective fading environment.