Hung-Quoc Duc Lai (University of Maryland, College Park), “Wireless network cocast: Cooperative communications with space-time network coding” (2011)

Hung-Quoc Duc Lai (University of Maryland, College Park), “Wireless network cocast: Cooperative communications with space-time network coding”, Advisor: Prof. K. J. Ray Liu (2011)

Abstract: Traditional cooperative communications can greatly improve communication performance. However, transmissions from multiple relay nodes are challenging in practice. Single transmissions using time-division multiple access cause large transmission delay, but simultaneous transmissions from two or more nodes using frequency-division multiple access (FDMA), code-division multiple access (CDMA), or distributed space-time codes are associated with the issues of imperfect frequency and timing synchronization due to the asynchronous nature of cooperation.

In this dissertation, the author proposed a novel concept of wireless network cocast (WNC) and developed its associated space-time network codes (STNCs) to overcome the foretold issues. In WNC networks, each node is allocated a time slot for its transmission and thus the issues of imperfect synchronization are eliminated. To reduce the large transmission delay, each relay node forms a unique signal, a combination of the overheard information, and transmits it to the intended destination. The combining functions at relay nodes form a STNC that ensures full spatial diversity as in traditional cooperative communications. The author applied the STNCs to multiuser cooperative networks. Furthermore, the author proposed a location-aware WNC scheme to reduce the aggregate transmit power and achieve even power distribution among the user nodes in the network.

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