| Cooperative relay can benefit from diversity gain through sharing antennas betweenmultiple users. This technology can reduce the outage probability of a wireless systemand the system capacity can be improved. All these advantages make it attractive. In adistributed network, wireless devices are generally battery operated, and linearmodulations have a lot of power consumption because of the high peak to averagepower ratio (PAPR), thus reduce the battery life. Continuous phase modulation (CPM)is a constant envelope modulation scheme, and can be amplified by the nonlinear poweramplifier. As a result, CPM can solve the energy consumption problem in the distributednetworks. In this thesis, we mainly study cooperative relay and the design of space-timecoding for CPM, and apply the pace-time codes for CPM to the cooperative relaysystem.In chapter two, we combine opportunistic relaying with incremental relay and twopath successive relay, and analyzed their achievable performance. Opportunistic relayscheme choose the best relay in M potential relay nodes, it can achieve high diversitygain without sacrifice system band efficiency. Firstly, the outage probability, symbolerror rate and channel capacity of the system combining opportunistic relaying withincremental relay are given. And simulation results are also provided. Theory analysisand simulation results both prove that the system can achieve diversity gain of M+1when the signal to noise ratio (SNR) is low. In the high SNR region, the system can notget diversity gain, but some power gain is achieved. Secondly, the outage probabilityand bit error rate (BER) of the system combining opportunistic relaying with two pathsuccessive relay are given under the assumption that the distance between the relaynodes are much small than the distance between the source and the relays. Simulationresults prove that the system can achieve diversity gain of M-1in the SNR region0to25dB when the distance between the relay nodes are1/5the distance between the sourceand the relays. The outage probability will increase as the distance between the relaysincrease. In the high SNR region, the inter relay interference constrained the systemperformance. In chapter three, the space-time coding for CPM is studied. Firstly, the signal modelfor CPM and the Laurent decomposition of binary CPM signal are given. Then thespace-time coding criterion for CPM over flat fading channel is provided and somespace-time codes which have low detecting complexity are introduced. At last, aspace-time code for GMSK over frequency selective channel is proposed. The schemeis based on differential prcoding and the frequency domain equalization of CPM signal.At the transmitter, the inherent memory of CPM signal is eliminated by differentialprcoding; at the receiver, the received signal is Laurent decomposed and a frequencydomain Alamouti code is formed. The proposed scheme need no Viterbi decoder at thereceiver and only linear operation is needed. As a result, the new scheme has muchlower detecting complexity.In chapter four, two space-time codes for CPM are applied to cooperative relaysystem. The first one is CPM waveform based, a CPM waveform is treated as a symbolof linear modulation, and Alamouti like code for CPM is formed at the source and therelay node. The second scheme is symbol based, the prcoding scheme in chapter three isused, also Alamouti code is formed at the source and the relay node. The second schemeis only adaptable for GMSK signal and suffer performance loss compared with the firstone, but it has lower detecting complexity.In chapter five, the contents of this thesis are summarized. Then the exsitingproblems is introduced in brief. Some advices for the further study are proposed. |
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