Cooperative communication for relay and multiple access channels: Design, optimization and performance analysis

In modern and future cellular networks such as Long-Term Evolution-Advanced (LTE-A)and 5G systems, cooperative communication can be deployed as an efficient method to improvesystem performance and meet the high-speed data transmission needs of multimediaservices. This thesis studies cooperation in the multiple access channel (MAC) setting,which includes the relay channel (RC) setting as a special case. These cooperative settingsapply to uplink transmission in cellular networks and form the basis to improve the widenetwork performance.The thesis proposes a time-division half-duplex scheme for the MAC with transmittercooperation (MAC-TC). The proposed scheme divides each transmission frame into threephases with variable durations. The two user equipments (UEs) partially exchange theirinformation in the first two phases, then cooperatively and coherently transmit to the basestation (BS) in the third phase, i.e., each UE performs a partial decode-forward (pDF) ofthe other UE information. The BS then performs joint decoding using the signals receivedin all three phases. After designing the scheme for the discrete memoryless channel (DMC),the thesis applies it to the Gaussian channel, derives its optimal resource allocations formaximum throughput and studies the outage performance over fading links. Comparedwith existing schemes, the proposed scheme improves throughput and outage performance,which makes it appealing for deployment in future cellular networks by utilizing the device-to-device (D2D) and infrastructure modes in the uplink transmission.The proposed scheme is near capacity-achieving when the cooperative links are strongerthan the direct links. Compared to existing schemes, this scheme achieves the same orbetter spectral efficiency with simpler signals and shorter decoding delay. By analyzingthe KKT optimality conditions for the maximum transmission rate, the thesis shows thatas the inter-user link qualities increase, the optimal scheme moves from no cooperation topartial then to full cooperation, in which the users fully exchange their information. Theoptimal power allocation to achieve the maximum throughput is analytically derived.The thesis further formulates the outage probability of the cooperative scheme overRayleigh fading channels assuming full channel state information (CSI) at receivers andlimited CSI at transmitters. Results show that cooperation can significantly reduce outageprobabilities and achieve the full diversity order despite additional outages at the UEs. Thethesis considers the RC setting in detail and analytically derives the outage performance for the coherent pDF relaying. Results show that the proposed scheme outperforms the existingschemes since it employs coherent transmission and joint decoding at the destination.Last, the thesis proposes a MAC with a joint source-destination cooperation (MAC-SDC)scheme that also engages the BS in cooperation by employing quantize-forward relaying.In this scheme, the users exchange their information not only through the cooperativelinks as in the MAC-TC, but also via the feedback links from the BS. Results showachievability improvement especially when the cooperative links are marginally strongerthan direct links. Moreover, for the RC setting, the thesis proves that the proposed schemeasymptotically achieves capacity by reaching the cutset bound as BS power increases.

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