Relay-assisted Multiple Access with Full-duplex Multi-Packet Reception

The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the source nodes is considered saturated and the cooperative relay, which does not have packets of its own, stores a source packet that it receives successfully in its queue when the transmission to the destination has failed. We obtain analytical expressions for key performance metrics at the relay, such as arrival and service rates, stability conditions, and average queue length, as functions of the transmission probabilities, the self interference coefficient, and the links' outage probabilities. Furthermore, we study the impact of the relay node and the self-interference coefficient on the per-user and aggregate throughput, and the average delay per packet. We show that perfect self-interference cancelation plays a crucial role when the SINR threshold is small, since it may result to worse performance in throughput and delay comparing with the half-duplex case. This is because perfect self-interference cancelation can cause an unstable queue at the relay under some conditions.Comment: Accepted for publication in the IEEE Transactions on Wireless Communication

On Buffer-Aided Multiple-Access Relay Channel

The paper treats uplink scenario where M user equipments (UEs) send to a Base Station (BS), possibly via a common Relay Station (RS) that is equipped with a buffer. This is a multiple-access relay channel (MARC) aided by a buffer. We devise a protocol in which the transmission mode is selected adaptively, using the buffer at the RS in order to maximize the average system throughput. We consider the general case in which the RS and the BS can have limits on the maximal number of transmitters that can be received over the multiple access channel. In each slot there are three type possible actions: (A1) multiple UEs transmit at rates that enable BS to decode them (A2) multiple UEs transmit, the BS can only decode the messages partially, while the RS completely; (A3) RS forwards the side information to BS about the partially decoded messages, which are going to be combined and decoded entirely at the BS, while simultaneously a number of UEs sends new messages to the BS. The results show that the adaptive selection of direct and buffer-aided relay transmissions leads to significant average throughput gains.Comment: 13 pages, 3 figures, accepted to IEEE Communications letter

Wireless Network-Level Partial Relay Cooperation: A Stable Throughput Analysis

In this work, we study the benefit of partial relay cooperation. We consider a two-node system consisting of one source and one relay node transmitting information to a common destination. The source and the relay have external traffic and in addition, the relay is equipped with a flow controller to regulate the incoming traffic from the source node. The cooperation is performed at the network level. A collision channel with erasures is considered. We provide an exact characterization of the stability region of the system and we also prove that the system with partial cooperation is always better or at least equal to the system without the flow controller.Comment: Submitted for journal publication. arXiv admin note: text overlap with arXiv:1502.0113

Secure Communications for the Two-user Broadcast Channel with Random Traffic

In this work, we study the stability region of the two-user broadcast channel (BC) with bursty data arrivals and security constraints. We consider the scenario, where one of the receivers has a secrecy constraint and its packets need to be kept secret from the other receiver. This is achieved by employing full-duplexing at the receiver with the secrecy constraint, so that it transmits a jamming signal to impede the reception of the other receiver. In this context, the stability region of the two-user BC is characterized for the general decoding case. Then, assuming two different decoding schemes the respective stability regions are derived. The effect of self-interference due to the full-duplex operation on the stability region is also investigated. The stability region of the BC with a secrecy constraint, where the receivers do not have full duplex capability can be obtained as a special case of the results derived in this paper. In addition, the paper considers the problem of maximizing the saturated throughput of the queue, whose packets does not require to be kept secret under minimum service guarantees for the other queue. The results provide new insights on the effect of the secrecy constraint on the stability region of the BC. In particular, it is shown that the stability region with secrecy constraint is sensitive to the coefficient of self-interference cancelation under certain cases.Comment: Submitted for journal publicatio