Research On Incremental HDAF Protocol In Cooperative Communication System

MIMO (multiple-input multiple-output) can obtain space diversity by employing multiple antennas on the transmitter and the receiver, which will generate independently faded versions of the signal at the receiver and combat multipath fading effectively. MIMO system makes the best use of multipath fading, which has a negative impact on traditional communication system. Without at the expense of spectrum, MIMO can improve performance of the system greatly and become one of the most important technologies in modern wireless communication. However, due to size of terminal, cost or power consumption limitations, it is impractical for terminals to employ multiple antennas in some scenarios. The concept of cooperative communication has recently emerged to overcome the limitations of MIMO system, which uses single-antenna relay nodes cooperatively in some way as a virtual MIMO system and obtains special diversity gain to mitigate fading further. Cooperative communication can improve the reliability of communication system, extend system coverage and reduce system power consumption. Cooperation communication can also combine with OFDM, UWB, CR and so on. The study of cooperative diversity scheme is an important issue to be addressed in cooperative communication, i.e., when and how to cooperate. Amplify-and-forward (AF) and decoded-and-forward (DF) are typical protocols in cooperative communication. The relay in AF scheme amplifies the signal and noise at the same time, works as a signal amplifier, while the relay in DF scheme detects and then retransmits the detected signal, which makes the hardware design of DF system more complex.,In this thesis, we concentrate our efforts on the research of cooperative diversity scheme for wireless communication networks. Firstly, we introduce the three basic protocols in cooperative communication:AF, DF and CC. More complex protocols such as selective protocol, incremental protocol, hybrid decode-amplify forward (HDAF) protocol and incremental-selective DF (ISDF) protocol are introduced in the later. A new scheme termed IHDAF protocol is proposed and makes compare with other scheme. The main work in this thesis can be summarized as follows:1) Based on the advantage and disadvantage of all the above protocols, a new cooperative diversity scheme in combining with incremental relaying and HDAF relaying strategies, termed incremental HDAF relaying scheme, is proposed and analyzed.2) By utilizing information theory and probability statistics as mathematical tools, closed-form expressions of outage and bit error rate (BER) for three nodes incremental HDAF cooperative system are derived, which will provide theoretical evidence for theoretical research and engineering design. Based on distance information of S-R link, an improved scheme is proposed to reduce the complexity of cooperative system, without losing of performance.3) The optimum relation of the two SNR thresholds in IHDAF cooperative system was achieved by expression of BER, in addition, the impact of the SNR thresholds on the performance of IHDAF relaying system is discussed.4) Considered the relay location and power allocation factor, IHDAF relaying scheme, ISDF relaying scheme and IDF relaying scheme are discussed and compared in different scenarios. Simulation results indicate that the performance of IHDAF relaying scheme is better than the other schemes, especially when the relay is near the destination.In the end, the problems to be solved in cooperative communication and future research topics are summarized.