| With rapid advances in computational algorithms and silicon technology, there has been a dramatic rise in research endeavors in all areas of wireless communications—physical layer, medium access methods, networks and systems. Information theory provides governing laws for communications systems by establishing fundamental limitations to reliable communications, and aids in leveraging this understanding into engineering solutions for wireless networks. Recently, with increasing emphasis on efficient utilization of radio-frequency spectrum and growing interest in providing wireless services with higher data rates, cooperative-communications has been proposed as a key enabling technology for next generation wireless networks. Although user-cooperation has proven benefits, the broadcast nature of the wireless medium exposes problems related to information security, by facilitating malicious or unauthorized access to confidential data, denial of service attacks, corruption of sensitive data, etc. In this work, we analyze the impact of cooperation and information security on the fundamental performance limits of four multiuser networks: (i) interference networks; (ii) relay networks; (iii) broadcast networks; and (iv) Z-networks.;First, we consider a three-user interference channel to obtain novel insights into the role of cooperation and interference management on its performance limits. We consider three cooperation schemes—(i) cumulative message-sharing; (ii) primary-only message-sharing; and ( iii) cognitive-only message-sharing, and employ different rate-splitting policies for interference management. As a case study, we consider the Gaussian channels, present several corollaries to enlarge the rate regions and derive outer bounds to obtain more insights.;Next, we explore the performance limits of the joint problem of cooperation and information security over a four node discrete memoryless relay network comprising a sender-destination pair, a relay node and an unauthorized eavesdropper. We consider two communication scenarios: In the first scenario, the relay aids transmissions from the source to the destination. In the second scenario, the relay is considered to be malicious, constraining the source to keep its message confidential from the relay node. In both scenarios, the relay is (i) opportunistic in the sense that, it utilizes the communication opportunity to transmit its own message to the destination and (ii ) constrained to secure its communication from the external eavesdropper.;Then, we derive the fundamental limits of three classes of two-user state-dependent discrete memoryless broadcast channels, with noncausal side-information at the encoder. The first class of channels comprises a sender broadcasting two independent messages to two non-cooperating receivers; for channels of the second class, each receiver is given the message it need not decode; and the third class comprises channels where the sender is constrained to keep each message confidential from the unintended receiver.;Lastly, we derive inner and outer bounds on the capacity region of the cognitive Z-channel, comprising two sender-receiver pairs with no cross-talk channel gain between one of the sender-receiver pairs. The non-cognitive sender has two messages, each message transmitted to the intended destination. The cognitive transmitter has one message intended to its pairing receiver; in addition, it has noncausal knowledge of the messages and the corresponding codewords of the non-cognitive sender. |
