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The medium access probability (MAP) of a random access protocol can severely impact network throughput especially for delay-sensitive applications, since it determines whether a node should transmit packets in a given slot or not. This paper focuses on network throughput maximization through optimizing the MAPs of all users under delay quality-of-service constraints in wireless interference-limited networks. Specifically, first, the total delay for transmitting one packet for a user is analyzed and derived based on an M/G/1 model. Then, the stochastic property of the aggregated interference is analyzed and its distribution is modeled as a log-normal distribution. Based on the delay and interference models, an optimization problem is formulated to derive the optimal MAPs so that the network throughput is maximized under the delay constraints. Two network traffic scenarios, homogeneous and heterogeneous user traffic, are discussed, respectively. For the case of homogeneous traffic, a closed-form expression of the optimal MAP is derived; for the case of heterogeneous traffic, a global $\epsilon $ -optimal algorithm based on the branch-and-bound framework and convex relaxation technology is proposed with relatively low complexity. Simulations results show that the proposed algorithms can achieve superior network throughput performance over existing schemes. [ABSTRACT FROM PUBLISHER]

In this paper, we study the throughput and delay in wireless cognitive social networks. Specifically, we consider a common scenario for cognitive radio networks (CRNs) where the primary and secondary networks operate at the same time and space and share the spectrum. On this basis, we integrate a social relationship into the CRN where each source node selects its destination upon a rank-based model, which captures the social characteristic well. By applying a cellular time-division multiple-access scheduling scheme, we first characterize the distinct traffic pattern caused by the social relationships between nodes. Then, we derive the achievable throughput and delay for both primary and secondary networks under the new network setting. In addition, we also study the cognitive social networks with infrastructure where $l=o$ $(n)$ base stations are regularly deployed within the primary network. Given a probabilistic routing strategy, throughput of the proposed network is recalculated. Particularly, due to the social relationships between nodes, we reveal that a larger $l$ is required if we expect a significant capacity gain within the primary network compared with previous works. [ABSTRACT FROM PUBLISHER]

Synchronization among primary users (PUs) and secondary users (SUs) is either explicitly or implicitly assumed in the literature to allow reliable dynamic spectrum access (DSA) and cognitive radio (CR) networking. However, in realistic DSA that supports ad-hoc transmissions, perfect synchronization is not attainable in the absence of a centralized control mechanism, particularly among SUs. Current efforts either ideally assume perfect synchronization among PUs and SUs or consider medium access that does not require network synchronization based on a single SU. In this paper, we propose an implementable asynchronous DSA scheme by practically considering the timing misalignment with multiple SUs competing for the spectrum opportunity. We further employ a game theoretical framework in asynchronous DSA to thoroughly predict the competition among SUs. Based on the equilibrium concept, we identify the feasible operating region, achieving optimal equilibrium that is not only reaching a win–win situation in the sense of PU throughput and spectrum utilization maximization but is robust to potential selfish behavior of SUs as well. Both low-complexity one-shot and sequential-decision access schemes are analyzed. We demonstrate that, when operating in the proposed feasible region, contrary to intuitive conjecture, the asynchronous DSA achieves surprising improvement in spectrum utilization. [ABSTRACT FROM PUBLISHER]

In multihop ad hoc networks over 802.11, the real bandwidth-delay product (BDP) cannot reach a value as large as in wired networks due to contention through wireless shared channels. As a result, conventional congestion-control algorithms cause an overshooting window problem and result in poor throughput in ad hoc networks. In this paper, we split the real round-trip time (RTT) into two parts: 1) congestion RTT and 2) contention RTT. We reveal that the contention RTT has nothing to do with the BDP and that the BDP is determined by only the congestion RTT if a link with the worst contention status does not lead to link breakage. An inadequate use of contention RTT causes a Transmission Control Protocol (TCP) congestion window overshooting problem. We propose a novel mechanism called congestion window adaptation through contention detection, which provides a more accurate method of estimating the contention status. Based on this mechanism, we present a congestion window adaptation method to limit the window size from overshooting. Simulation results show that our proposed mechanism outperforms the conventional TCP and the enhanced mechanisms called TCP with contention control and TCP with a maximum window. [ABSTRACT FROM PUBLISHER]