Distributed multi-hop scheduling and medium access with delay and throughput constraints

Abstract

Providing quality of service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypothetical) centralized and ideal dynamic priority scheduler. In this paper, we develop two mechanisms for QoS communication in multi-hop wireless networks. First, we devise distributed priority scheduling, a technique that piggybacks the priority tag of a node's head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. By monitoring transmitted packets, each node maintains a scheduling table which is used to assess the node's priority level relative to other nodes. We then incorporate this scheduling table into existing IEEE 802.11 priority back-off schemes to approximate the idealized schedule. Second, we observe that congestion, link errors, and the random nature of medium access prohibit an exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termed multi-hop coordination so that downstream nodes can increase a packet's relative priority to make up for excessive delays incurred upstream. We next develop a simple analytical model to quantitatively explore these two mechanisms. In the former case, we study the impact of the probability of overhearing another packet's priority index on the scheme's ability to achieve the ideal schedule. In the latter case, we explore the role of multi-hop coordination in increasing the probability that a packet satisfies its end-to-end QoS target. Finally, we perform a set of ns-2 simulations to study the scheme's performance under more realistic conditions.

A spatiotemporal communication protocol for wireless sensor networks

“…11 also demonstrates that when node density is sufficiently high (M = 5 & corresponding node density > 12.78), statistically the pseudoproblem rarely happens (< 0.2 percent) when the localization error below half radio range. This theoretical analysis is consistent with our simulation result in [11].…”

“…RAP [16] uses velocity monotonic scheduling to prioritize real-time traffic and enforces such prioritization through a differentiated MAC Layer. Kanodia et al [11] proposed a service differentiation for delaysensitive traffic by prioritizing 802.11. Woo and Culler [21] proposed an adaptive MAC layer rate control to achieve fairness among nodes with different distances to the base station.…”

“…Note, while SPEED does not use routing tables, SPEED does utilize location information to carry out routing. Because of this, we assume that each node is location-aware [11].…”

Topology Control with Radio Interference Detection in Wireless Sensor Network

“…Medium access and packet scheduling algorithm must select and transmit packets in accordance with QOS requirements Distributed Dynamic Priority scheduling provide packet transmission in multihop wireless network with high fraction of Quality of Service [10].…”

Improving the Performance of TCP in the Presence of Interacting UDP Flows in Ad Hoc Networks

“…Their results show that in certain scenarios significant improvements in fairness can be achieved without sacrificing throughput. Protocols other than the IEEE 802.11 MAC scheme have also been proposed [10,11]. In [5] it is shown that intelligently tuning the parameters used in TCP and the IEEE 802.11 protocols improves performance.…”