On the Delay-Throughput Tradeoff in Multi-User Wireless Networks

Computing Research Repository, 2007

In this paper, we introduce novel coding schemes for wireless networks with random transmission delays. These coding schemes obviate the need for synchronicity, reduce the number of transmissions and achieve the optimal rate region in the corresponding wired model for both multiple unicast and multicast cases with up to three users under the equal rate constraint. The coding schemes are presented in two phases; first, coding schemes for line, star and line-star topologies with random transmission delays are provided. Second, any general topology with multiple bidirectional unicast and multicast sessions is shown to be decomposable into these canonical topologies to reduce the number of transmissions without rate redundancy. As a result, the coding schemes developed for the line, star and line-star topologies serve as building blocks for the construction of more general coding schemes for all networks. The proposed schemes are proved to be Real Time (RT) for wireless networks in the ...

This work focuses on the throughput scaling laws of fading networks in the limit of large number of nodes. In particular, we are interested in the practical assumption of channel state information (CSI) is perfectly known at the receivers, but the transmitters have only partial CSI via receivers' feedback.

Ad Hoc Networks, 2012

Energy efficiency and transmission delay are very important parameters for wireless multihop networks. Numerous works that study energy efficiency and delay are based on the assumption of reliable links. However, the unreliability of channels is inevitable in wireless multihop networks. In addition, most of works focus on self-organization protocol design while keeping non-protocol system parameters fixed. While, very few works reveal the relationship between the network performance and these physical parameters, in other words, the best networks performance could be obtained by the physical parameters. This paper investigates the tradeoff between the energy consumption and the latency of communications in a wireless multihop network using a realistic unreliable link model. It provides a closed-form expression of the lower bound of the energy-delay tradeoff and of energy efficiency for different channel models (additive white Gaussian noise, Rayleigh fast fading and Rayleigh block-fading) in a linear network. These analytical results are also verified in 2-dimensional Poisson networks using simulations. The closed-form expression provides a framework to evaluate the energy-delay performance and to optimize the parameters in physical layer, MAC layer and routing layer from the viewpoint of cross-layer design during the planning phase of a network.

IEEE Transactions on Wireless Communications, 2020

Link scheduling plays a key role in the network capacity and the transmission delay. In this paper, we study the problem of maximum link scheduling (MLS), aiming to characterize the maximum number of links that can be successfully scheduled simultaneously under Rayleigh-fading and multiuser interference. After analyzing the minimum distance between successful links in the existing GHW scheduling algorithm, we propose a DLS (Distance-based Link Scheduling) algorithm. Then, the global interference is characterized and bounded by introducing a separation distance between selected links, building on which we propose a distributed version of DLS (denoted by DDLS) that converges to a constant factor of the non-fading optimum within time complexity O(n ln n), where n is the number of links. Furthermore, we study the Shortest Link Scheduling (SLS) problem, which minimizes the number of time slots to successfully schedule each link for at least once. An algorithm for SLS with approximation factor of O(ln n) is obtained by executing DDLS. Extensive simulations show that DDLS greatly outperforms GHW and the other two popular algorithms.

IEEE Transactions on Mobile Computing, 2000

In this paper, the problem of throughput optimization in decentralized wireless networks with spatial randomness under queue stability and packet loss constraints is investigated. Two key performance measures are analyzed, namely the effective link throughput and the network spatial throughput. Specifically, the combination of medium access probability, coding rate, and maximum number of retransmissions that maximize each throughput metric is analytically derived for a class of Poisson networks, in which packets arrive at the transmitters following a geometrical distribution. Necessary conditions so that the effective link throughput and the network spatial throughput are stably achievable under bounded packet loss are determined, as well as upper bounds for both cases by solving the unconstrained optimization problem. Our results show in which system configuration stable achievable throughputs can be obtained as a function of the network density and the arrival rate. They also evince conditions for which the per-link throughput-maximizing operating points coincide or not with the aggregate network throughput-maximizing operating regime.

2021

Many shortest link scheduling algorithms adopt non-fading SINR interference model, which assumes that the received signal power will always remain determinate as long as the transmission power of the corresponding sender is fixed. In fact, because environment always influences the propagation of radio signals, the received signal power is by no means a certain value. Rayleigh fading is a statistical model for radio signals propagation. It assumes that the strength of a signal on a receiver is a random variable, varying with the Rayleigh distribution. This paper proposes a shortest link scheduling algorithm under the Rayleigh fading model (SLSRF). The SLSRF partitions the wireless network area into hexagons and colors the hexagons with 3 different colors such that two neighboring hexagons have different colors. The senders of the links scheduled simultaneously are arranged in hexagons with the same color. The correctness of the SLSRF is proved through theoretical analysis, and the ef...

2015

The capacity scaling law of wireless networks hasbeen considered as one of the most fundamental issues. In this survey, we aim at providing a comprehensive overview of the development in the area of scaling laws for throughput capacity and delay in wireless networks. We begin with back-ground information on the notion of throughput capacity of random networks. Based on the benchmark random network model, we then elaborate the advanced strategies adopted to improve the throughput capacity, and other factors that affect the scaling laws. We also present the fundamental tradeoffs between throughput capacity and delay under a variety of mobility models. In addition, the capacity and delay for hybrid wireless networks are surveyed, in which there are at least two types of nodes functioning differently, e.g., normal nodes and infrastructure nodes. Finally, recent studies on scaling law for throughput capacity and delay in emerging vehicular networks are introduced.

Lecture Notes in Computer Science, 2009

This paper is motivated by exploring the impact of the number of channels on the achievable communication latency for a specific communication task. We focus on how to utilize the multiple channels to speed up four group communications including broadcast, aggregation, gathering, and gossiping in wireless networks under protocol interference model. Four scheduling algorithms are developed for these four group communications. We derive explicit tight bounds on the latencies of the four communication schedules produced by these algorithms. These latency bounds in general decrease with the number of channels and are also within constant factors of the respective minimum. 1 Introduction With the rapid technology advances, many off-the-shelf wireless transceivers (i.e., radios) are capable of operating on multiple channels. For example, the IEEE 802.11 b/g standard and IEEE 802.11a standard provide 3 and 12 channels respectively, and MICA2 sensor motes support more than 50 channels. This paper aims to conduct comprehensive algorithmic studies of minimizing the communication latency by utilizing multiple channels under the following network model. All network nodes V lies in plane. Every node has a communication radius normalized to one, and an interference radius ρ for some parameter ρ ≥ 1. The communication (respectively, interference) range of a node v ∈ V is the disk centered at v of one (respectively, ρ). A node v can receive the message successfully from a transmitting node u if v is within the transmission range of u but is outside the interference range of any other node transmitting simultaneously at the same channel. Let λ be the number of available channels. Then, each network is associated with a pair of parameters (λ, ρ). We further assume that all communications proceeds in synchronous time-slots and each node can either transmit or receive at most one packet of a fixed size in each time-slot.

IEEE/ACM Transactions on Networking, 2011

We analyze the delay performance of a multihop wireless network with a fixed route between each source-destination pair. We develop a new queue grouping technique to handle the complex correlations of the service process resulting from the multihop nature of the flows. A general set-based interference model is assumed that imposes constraints on links that can be served simultaneously at any given time. These interference constraints are used to obtain a fundamental lower bound on the delay performance of any scheduling policy for the system. We present a systematic methodology to derive such lower bounds. For a special wireless system, namely the clique, we design a policy that is sample-path delay-optimal. For the tandem queue network, where the delay-optimal policy is known, the expected delay of the optimal policy numerically coincides with the lower bound. We conduct extensive numerical studies to suggest that the average delay of the back-pressure scheduling policy can be made close to the lower bound by using appropriate functions of queue length.