A token-based scheduling scheme for WLANs supporting voice/data traffic and its performance analysis

Abstract

Abstract-Most of the existing medium access control (MAC) protocols for wireless local area networks (WLANs) provide prioritized access by adjusting the contention window sizes or interframe spaces for different traffic classes. Those MAC protocols can only provide statistical priority access and limited service differentiation. In this paper, a novel token-based scheduling scheme is proposed for a fully-connected WLAN that supports both voice and data traffic. The proposed scheme can provide guaranteed priority access to voice traffic and, at the same time, provide more precise and quantitative service differentiation for data traffic, which provides great flexibility and facility to the network service provider for service class management. Simulation results demonstrate that the proposed scheme can guarantee a small delay for voice traffic. For data traffic, it can effectively achieve proportional differentiation among different classes, while achieving fair resource sharing within the same class. In addition, compared with a contention based scheme and a centralized polling scheme, the proposed scheme significantly improves the channel utilization by avoiding collisions (in the contention based scheme) and the polling overhead (in the polling scheme). The performance analysis of the proposed scheme is also presented. The accuracy of the analytical results is verified by computer simulations.

DFMAC: DTN-Friendly Medium Access Control for Wireless Local Area Networks Supporting Voice/Data Services

“…Performance comparisons with the modified HCF scheme [11] and probabilistic token-based scheme [12] are also provided to show the efficiency of our proposed scheme. Note that a comparison between the DFMAC and the IEEE 802.11e MAC is not provided since the advantage of the modified HCF scheme over IEEE 802.11e MAC is already demonstrated in [11].…”

“…The framework of probabilistic token passing proposed in [12] is adopted for the local data phase, due to its good performance and its capability of supporting service differentiation. For a group G of nodes (or queues) contending for wireless channel access, the token passing scheme can be characterized by two parameters: p p p = { p i , 1 ≤ i ≤ |G|} and P P P = {P i, j , 1 ≤ i, j ≤ |G|}, where p i denotes the token holding probability of node i, P i, j represents the token passing probability from node i to node j, and |G| is the size of G. Without service differentiation among local data nodes, the values of p i and P i, j are given by…”

“…where the first and second summations correspond to the fractions of channel time occupied by uplink and downlink voice services, respectively; T O is the duration for transmitting the overhead of a voice packet, including τ I , PHY preamble, and RTP/UDP/IP headers [12]; T PL,V is the duration for the payload transmission of a voice packet; k is the index of a hot spot. Then, the fraction of channel time for local voice services can be calculated as…”

“…By utilizing voice multiplexing, deterministic access prioritization, and voice packet aggregation, the voice/data capacity of IEEE 802.11e HCF can be further improved [11]. In addition, a probabilistic token-based scheme is proposed, which not only achieves high channel utilization but also provides service differentiation for delay sensitive voice service and best-effort data service [12]. However, the existing work focuses on nodes in hot spots only.…”

A multi-channel token ring protocol for QoS provisioning in inter-vehicle communications

“…In [11], a token based control scheme is presented to emulate the window-based flow and congestion control in wireless/wired Networks. In [12], a token based scheme is presented to ensure guaranteed priority for voice traffic in single-hop networks. In [13], an overlay token ring protocol (OTRP) is proposed for IVC, and it operates in two modes.…”