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Recently, multiple concurrent transmission techniques have been proposed for smartly exploiting interference to improve network throughput. This paper considers zero-forcing (ZF) precoding that allows two interfering links to concurrently transmit under certain situations. This paper focuses on identifying appropriate schedule schemes that efficiently utilize the ZF precoding opportunities to improve network throughput. With this motivation, we define novel link models to formulate our concerned problem. We also develop a distributed scheduling algorithm by using belief propagation. Finally, we conduct extensive simulation experiments to evaluate the efficiency of ZF in improving network throughput in multihop wireless networks. Our simulations confirm that intelligently utilizing ZF in multihop networks is very effective in improving throughput. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel buffer-aided link selection scheme based on network coding in the multiple-hop relay network. The proposed scheme significantly increases transmission throughput by applying data buffers at the relays to decrease the outage probability and using network coding to increase the data rate. The closed-form expressions of both average throughput and packet delay are successfully derived. The proposed scheme not only has significantly higher throughput than both the traditional and existing buffer-aided max-link schemes but smaller average packet delay than the max-link scheme as well, making it an attractive scheme in practice. [ABSTRACT FROM PUBLISHER]

To improve the efficiency of wireless data communications, new physical-layer transmission methods based on known-interference cancelation (KIC) have been developed. These methods share the common idea that interference can be canceled when its content is known. Existing work on KIC mainly focuses on single-hop or two-hop networks, with physical-layer network coding and full-duplex communications as typical examples. This paper extends the idea of KIC to general multihop networks and proposes an end-to-end KIC (E2E-KIC) transmission method, together with its medium access control (MAC) design. With E2E-KIC, multiple nodes in a flow passing through a few nodes in an arbitrary topology can simultaneously transmit and receive on the same channel. We first present a theoretical analysis on the effectiveness of E2E-KIC in an idealized case. Then, to support E2E-KIC in multihop networks with an arbitrary topology, we propose an E2E-KIC-supported MAC protocol (E2E-KIC MAC), which is based on an extension of the Request-to-Send/Clear-to-Send mechanism in the IEEE 802.11 MAC. We also analytically analyze the performance of the proposed E2E-KIC MAC in the presence of hidden terminals. Simulation results illustrate that the proposed E2E-KIC MAC can improve network throughput and reduce end-to-end delay. [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]

Although the system throughput of a wireless communication system considering multiple users' geographical distribution on a 2-D plane and various traffic characteristics is an important performance metric, its mathematical analysis is very difficult due to the nonindependent identically distributed distribution of the received signal-to-noise ratio (SNR) of each mobile terminal and the complex dynamics of the traffic patterns. Therefore, complicated system-level simulations have been the only approach to evaluate the system throughput of downlink packet-access systems. In this paper, we propose an efficient analytical approach to estimate the system throughput of downlink packet-access systems by using point mass approximation, which is widely used in physics and mechanics. The proposed analysis framework enables the mathematical analysis of the system throughput performance by considering various positions of mobile terminals and traffic patterns without the complicated and heavy system-level simulations. Although the proposed approach has a tradeoff relation between computation complexity and accuracy, we show that it is possible to obtain an effective accuracy with moderate complexity using the proposed analytical approach. [ABSTRACT FROM PUBLISHER]

In this paper, we propose two cross-layer algorithms, namely, the Power-optimal Scheduling Algorithm (PSA) and the Throughput-optimal Scheduling Algorithm (TSA), to minimize energy consumption and to maximize throughput, respectively, in multihop wireless networks. Our algorithms guarantee a flow-based minimum data rate and jointly integrate congestion control, power allocation, routing, and link rate scheduling. Different from traditional algorithms that assume infinite buffers, the proposed algorithms deterministically upper bound the flow-based packet queue length and thus can be employed in multihop networks with finite buffers. In addition, the algorithms achieve a power expenditure/throughput “\epsilon-close” to the optimal value, with a tradeoff of order O(\1/\epsilon) in buffer size. The average end-to-end delay upper bound can also be derived from the finite buffer property. Finally, numerical results are presented to show the performance of the two algorithms with different system parameters. [ABSTRACT FROM PUBLISHER]

Interference alignment (IA) is widely regarded as a promising interference management technique for wireless networks and its potential is most profound in interference-intensive environments. This motivates us to study IA for multicast communications in multihop MIMO networks, which are rich in interference by nature. We develop a set of linear constraints that can characterize a feasible design space of IA for multicast communications. The set of linear constraints constitutes a simple mathematical model of IA that allows us to conduct cross-layer multicast throughput optimization in multihop MIMO networks, but without getting involved into the onerous signal design at the physical layer. Based on the mathematical model of IA, we formulate a multicast throughput maximization problem and develop an approximation solution that can achieve $(1-\varepsilon)$ -optimality. Simulation results show that the use of IA can significantly increase the multicast throughput in multihop MIMO networks and the throughput gain increases with the volume of multicast traffic and the number of antennas. [ABSTRACT FROM AUTHOR]

Network coding aware routing (NCAR) has been emerging as an effective approach to create coding opportunities actively in multihop networks. To the best of our knowledge, most of the existing methods focus on a “static” design that considers coding opportunities based on fixed routes and invariable packet flows. This “static” way results in the optimality of routes suffering from a high sensitive behavior on both network topology and flow dynamic and, hence, reduces the throughput of routes in time-varying networks. To solve this problem, we propose a high-throughput NCAR scheme that supports dynamic multihop network connectivity and achieves throughput optimization, even with multiple variable flows. In the proposed scheme, a back-pressure-based NCAR algorithm is designed to push the flows dynamically into the nodes that have better network coding opportunities with no knowledge of network topology and flow dynamic. As a byproduct, the proposed method also exhibits a significantly improved delay performance relative to the traditional back-pressure algorithm. Simulation results reveal that the proposed scheme improves network capacity and alleviates end-to-end delay in heavy load networks. [ABSTRACT FROM PUBLISHER]