Adaptive topology-transparent distributed scheduling in wireless networks

Proceedings of the IEEE International Conference on Communications, 2010, p. 1-5Transmission scheduling is a key design problem in wireless multi-hop networks. Many transmission scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time division multiple access (TDMA) frame length. Most of the scheduling algorithms are topology-dependent. They are generally graph-based and depend on the exact network topology information. Thus, they cannot adapt well to the dynamic wireless environment. In contrast, topology-transparent TDMA scheduling algorithms do not need detailed topology information. However, these algorithms offer very low minimum throughput. The objective of this work is to propose an adaptive topology-transparent scheduling algorithm to offer better throughput performance. With our algorithm, each node finds a transmission schedule so as to reduce the transmission conflicts and adapt better to the changing network environment. The simulation results show that the performance of our algorithm is better than the existing topology-transparent algorithms. ©2010 IEEE.published_or_final_versio

Performance Improvement of Topology-Transparent Broadcast Scheduling in Mobile Ad Hoc Networks

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Analysis of a Probabilistic Topology-Unaware TDMA MAC Policy for Ad-Hoc Networks

The design of an efficient Medium Access Control (MAC) for ad-hoc networks is challenging. Topology-unaware TDMAbased schemes, suitable for ad-hoc networks, that guarantee a minimum throughput, have already been proposed. These schemes consider a deterministic policy for the utilization of the assigned scheduling time slots that never utilizes non-assigned slots although in such slots collision-free transmissions are possible even under heavy traffic conditions. A simple probabilistic policy, capable of utilizing the non-assigned slots according to an access probability, fixed for all users in the network, is introduced and analyzed here. The conditions under which the system throughput under the probabilistic policy is higher than that under the deterministic policy are derived analytically. Further analysis of the system throughput is shown to be difficult or impossible for the general case and certain approximations have been considered whose accuracy is also investigated. The approximate analysis determines the value for the access probability that maximizes the system throughput as well as simplified lower and upper bounds that depend only on a topology density metric. Simulation results demonstrate the comparative advantage of the probabilistic policy over the deterministic policy and show that the approximate analysis successfully determines the range of values for the access probability for which the system throughput under the probabilistic policy is not only higher than that under the deterministic policy, but it is also close to the maximum

Analysis of a probabilistic topology-unaware TDMA MAC policy for ad hoc networks

The design of an efficient medium access control (MAC) for ad hoc networks is challenging. Topology-unaware time-division multiple-access-based schemes, suitable for ad hoc networks, that guarantee a minimum throughput, have already been proposed. These schemes consider a deterministic policy for the utilization of the assigned scheduling time slots that never utilizes nonassigned slots although in such slots collision-free transmissions are possible even under heavy traffic conditions. A simple probabilistic policy, capable of utilizing the nonassigned slots according to an access probability, fixed for all users in the network, is introduced and analyzed here. The conditions under which the system throughput under the probabilistic policy is higher than that under the deterministic policy are derived analytically. Further analysis of the system throughput is shown to be difficult or impossible for the general case and certain approximations have been considered whose accuracy is also investigated. The approximate analysis determines the value for the access probability that maximizes the system throughput, as well as simplified lower and upper bounds that depend only on a topology density metric. Simulation results demonstrate the comparative advantage of the probabilistic policy over the deterministic policy and show that the approximate analysis successfully determines the range of values for the access probability for which the system throughput under the probabilistic policy is not only higher than that under the deterministic policy, but it is also close to the maximum

Throughput Analysis of a Probabilistic Topology-Unaware TDMA MAC Policy for Ad-Hoc Networks

The design of an e#cient Medium Access Control (MAC) is challenging in ad-hoc networks where users can enter, leave or move inside the network without any need for prior configuration. The existing topology-unaware TDMA-based schemes are capable of providing a minimum guaranteed throughput by considering a deterministic policy for the utilization of the assigned scheduling time slots. In an earlier work, a probabilistic policy that utilizes the non-assigned slots according to an access probability, common for all nodes in the network, was proposed. The achievable throughput for a specific transmission under this policy was analyzed. In this work, the system throughput is studied and the conditions under which the system throughput under the probabilistic policy is higher than that under the deterministic policy are established. In addition, the value for the access probability that maximizes the system throughput is determined analytically, as well as simplified lower and upper bounds that depend only on a topology density metric. Since the analysis of the system throughput is shown to be di#cult or impossible in the general case an approximation is introduced whose accuracy is investigated. Simulation results show that the approximate analysis successfully determines the range of values for the access probability for which the system throughput under the probabilistic policy is not only higher than that under the deterministic, but it is also close to the maximum

Throughput analysis of a probabilistic topology-unaware TDMA MAC policy for ad-hoc networks

The existing topology-unaware TDMA-based schemes are suitable for ad-hoc networks and capable of providing a minimum guaranteed throughput by considering a deterministic policy for the utilization of the assigned scheduling time slots. In an earlier work, a probabilistic policy that utilizes the non-assigned slots according to an access probability, common for all nodes in the network, was proposed. The achievable throughput for a specific transmission under this policy was analyzed. In this work, the system throughput is studied and the conditions under which the system throughput under the probabilistic policy is higher than that under the deterministic policy and close to the maximum are established. © Springer-Verlag Berlin Heidelberg 2003

Throughput Analysis of a Probabilistic Topology-Unaware TDMA MAC Policy for Ad-Hoc Networks Konstantinos Oikonom ou

The design of an e#cient Medium Access Control (MAC) is challenging in ad-hoc networks where users can enter, leave or move inside the network without any need for prior configuration. The existing topology-unaware TDMA-based schemes are capable of providing a minimum guaranteed throughput by considering a deterministic policy for the utilization of the assigned scheduling time slots. In an earlier work, a probabilistic policy that utilizes the non-assigned slots according to an access probability, common for all nodes in the network, was proposed. The achievable throughput for a specific transmission under this policy was analyzed. In this work, the system throughput is studied and the conditions under which the system throughput under the probabilistic policy is higher than that under the deterministic policy are established. In addition, the value for the access probability that maximizes the system throughput is determined analytically, as well as simplified lower and upper bounds that depend only on a topology density metric. Since the analysis of the system throughput is shown to be di#cult or impossible in the general case an approximation is introduced whose accuracy is investigated. Simulation results show that the approximate analysis successfully determines the range of values for the access probability for which the system throughput under the probabilistic policy is not only higher than that under the deterministic, but it is also close to the maximum

Integrated Scheduling and Beam Steering for Spatial Reuse

This document describes an approach to integrating antenna selection and control into a time-division MAC scheduling process. I argue that through such integration it is possible to achieve greater spatial reuse and interference mitigation than by solving the two problems separately. Without coupling between the MAC scheduling and physical antenna configuration processes, a \u22chicken-and-egg\u22 problem exists: If antenna decisions are made before scheduling, they cannot be optimized for the communication that will actually occur. If, on the other hand, the scheduling decisions are made first, the scheduler cannot know what the actual interference and communications properties of the network will be. This dissertation presents algorithms for optimal spatial reuse TDMA scheduling with reconfigurable antennas. I present and solve the joint beam steering and scheduling problem for spatial reuse TDMA and describe an implemented system based on the algorithms developed. The algorithms described achieve up to a 600% speedup over TDMA in the experiments performed. This is based on using an optimization decomposition approach to arrive at a working distributed protocol which is equivalent to the original problem statement while also producing optimal solutions in an amount of time that is at worst linear in the size of the input. This is, to the best of my knowledge, the first actually implemented STDMA scheduling system based on dual decomposition. This dissertation identifies and briefly address some of the challenges that arise in taking such a system from theory to reality