A call admission and rate control scheme for multimedia support over IEEE 802.11 wireless LANs

Abstract

Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time, achieve a high channel utilization.

A Rate based Congestion Control Mechanism Using Fuzzy Controller in MANETs

“…If specified congestion level is low then it performs multiplicative increase phase according to (2) inorder the improvement of network throughput. [6] new − rate = old − rate * (…”

Packet aggregation in multi-rate wireless LANs

“…The metric we use to compare the aggregation mechanisms is the total transmission time, T T x , as it directly maps to performance [20], [21]. Given a certain amount of data to be transmitted at particular data rates, the mechanism that has a lower value of T T x will give higher network capacity.…”

Improving Voice and Data Services in Cellular/WLAN Integrated Networks by Admission Control

“…When the packet service rate is larger than the arrival rate (unsaturated case) and the collision probability is small enough (e.g., less than 0.1), the service queue of a flow is almost empty and the packet delay (say, less than 30 ms) is sufficiently small to meet the requirement of the real-time voice service [7]. Hence, we consider unsaturated downlink data traffic, which is regulated by applying rate control at the access point [8]. The voice traffic is also considered unsaturated depending on the codec.…”

“…First, we derive the equilibrium distribution of an equivalent birth-death process with two customer classes of finite populations K 1 and K 2 served in a PS discipline. The equilibrium distribution π can be obtained from the following linear equation system [14] π F = 0 (8) where F is defined as follows. Let n = (n 1 , n 2 ).…”

“…However, it is found in [7] that, when the number of contention nodes is large enough, the WLAN channel utilization is maximized in the unsaturated case instead of the saturated case. Hence, in this study, we consider applying rate control to regulate downlink data traffic at the access point [8]. The traffic regulation can take good advantage of the elasticity of data traffic to improve the voice support of the WLAN; at the same time, it allows more data calls admitted to the WLAN and more effectively complements the data service provisioning of the cellular network.…”