Half-Duplex or Full-Duplex Relaying: A Capacity Analysis under Self-Interference

In this paper multi-antenna half-duplex and full-duplex relaying are compared from the perspective of achievable rates. Full-duplexing operation requires additional resources at the relay such as antennas and RF chains for self-interference cancellation. Using a practical model for the residual self-interference, full-duplex achievable rates and degrees of freedom are computed for the cases for which the relay has the same number of antennas or the same number of RF chains as in the half-duplex case, and compared with their half-duplex counterparts. It is shown that power scaling at the relay is necessary to maximize the the degrees of freedom in the full-duplex mode.Comment: New references added and some typos have been corrected. 6 Pages, 5 Figures. Accepted for publication in the CISS-201

Throughput Analysis of Primary and Secondary Networks in a Shared IEEE 802.11 System

In this paper, we analyze the coexistence of a primary and a secondary (cognitive) network when both networks use the IEEE 802.11 based distributed coordination function for medium access control. Specifically, we consider the problem of channel capture by a secondary network that uses spectrum sensing to determine the availability of the channel, and its impact on the primary throughput. We integrate the notion of transmission slots in Bianchi's Markov model with the physical time slots, to derive the transmission probability of the secondary network as a function of its scan duration. This is used to obtain analytical expressions for the throughput achievable by the primary and secondary networks. Our analysis considers both saturated and unsaturated networks. By performing a numerical search, the secondary network parameters are selected to maximize its throughput for a given level of protection of the primary network throughput. The theoretical expressions are validated using extensive simulations carried out in the Network Simulator 2. Our results provide critical insights into the performance and robustness of different schemes for medium access by the secondary network. In particular, we find that the channel captures by the secondary network does not significantly impact the primary throughput, and that simply increasing the secondary contention window size is only marginally inferior to silent-period based methods in terms of its throughput performance.Comment: To appear in IEEE Transactions on Wireless Communication

The Stochastic-Calculus Approach to Selected Topics in Information Theory

170 pagesWe study the following three information-theoretic problems using tools derived from stochastic calculus: the multi-receiver Poisson channel, lossy compression of point-processes, and the second-order coding rate in discrete memoryless channels (DMCs) with feedback. We obtain a general formula for the mutual information involving the point processes that allows for conditioning and the use of auxiliary random variables. We then use this formula to compute necessary and sufficient conditions under which one Poisson channel is less noisy and/or more capable than another, which turn out to be distinct from the conditions under which this ordering holds for the discretized versions of the channels. We also use the general formula to determine the capacity region of various multi-receiver Poisson channel. We introduce a new distortion measure for point processes called functional covering distortion. We obtain the distortion-rate function with feedforward under this distortion measure for a large class of point processes. For Poisson processes, stronger results are obtained by constraining the reconstruction. We derive the rate-distortion function for this constrained functional-covering and show that feedforward does not improve it. Moreover, we characterize the rate-distortion region for a two-encoder CEO problem for Poisson process and show that feedforward does not improve this region. As a corollary, we obtain the rate-distortion region of remote Poisson source. A strong data processing inequality for Poisson processes under superposition is derived to prove the converse of the CEO problem. For DMCs, we show that feedback does not improve the second-order coding rate for a class of DMCs which complements the class of channels for which feedback is known to improve the second-order coding rate. We derive an upper bound on the achievable rate with feedback utilizing a novel proof technique for general DMCs

Half-duplex or full-duplex communications: degrees of freedom analysis under self-interference

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop, and two way two hop communication are compared in terms of degrees of freedom (DoF) under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario for HD, antenna conserved (AC), and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, the achievable AC FD with imperfect SI cancellation performs strictly below HD, and RC FD DoF tradeoff is superior when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has a large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, the achievable DoF pairs for FD do not outperform HD. FD still can achieve better DoF pairs than HD, provided the relay has sufficient number of antennas and SI suppression

Half-Duplex or Full-Duplex Communications: Degrees of Freedom Analysis Under Self-Interference

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop, and two way two hop communication are compared in terms of degrees of freedom (DoF) under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario for HD, antenna conserved (AC), and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, the achievable AC FD with imperfect SI cancellation performs strictly below HD, and RC FD DoF tradeoff is superior when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has a large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, the achievable DoF pairs for FD do not outperform HD. FD still can achieve better DoF pairs than HD, provided the relay has sufficient number of antennas and SI suppression