Differentiation, QoS Guarantee, and optimization for real-time traffic over one-hop ad hoc networks

Comput. Sci. Div., Memphis Univ., TN, USA
IEEE Transactions on Parallel and Distributed Systems (Impact Factor: 2.17). 07/2005; 16(6):538- 549. DOI: 10.1109/TPDS.2005.70
Source: IEEE Xplore


Nodes having a self-centrically broadcasting nature of communication form a wireless ad hoc network. Many issues are involved to provide quality of service (QoS) for ad hoc networks, including routing, medium access, resource reservation, mobility management, etc. Previous work mostly focuses on QoS routing with an assumption that the medium access control (MAC) layer can support QoS very well. However, contention-based MAC protocols are adopted in most ad hoc networks since there is no centralized control. QoS support in contention-based MAC layer is a very challenging issue. Carefully designed distributed medium access techniques must be used as foundations for most ad hoc networks. In this paper, we study and enhance distributed medium access techniques for real-time transmissions in the IEEE 802.11 single-hop ad hoc wireless networks. In the IEEE 802.11 MAC, error control adopts positive acknowledgement and retransmission to improve transmission reliability in the wireless medium (WM). However, for real-time multimedia traffic with sensitive delay requirements, retransmitted frames may be too late to be useful due to the fact that the delay of competing the WM is unpredictable. In this paper, we address several MAC issues and QoS issues for delay-sensitive real-time traffic. First, a priority scheme is proposed to differentiate the delay sensitive real-time traffic from the best-effort traffic. In the proposed priority scheme, retransmission is not used for the real-time traffic, and a smaller backoff window size is adopted. Second, we propose several schemes to guarantee QoS requirements. The first scheme is to guarantee frame-dropping probability for the real-time traffic. The second scheme is to guarantee throughput and delay. The last scheme is to guarantee throughput, delay, and frame-dropping probability simultaneously. Finally, we propose adaptive window backoff schemes to optimize throughput with and without QoS constraints.

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    • "For wireless TDMA systems that need to support multiple stream transmissions in a given frequency band, the transmissions for the different ongoing video streams need to be separated in time. Real-time transmissions schemes, e.g., [19]–[22], can achieve this transmission time separation and ensure that the video packets are delivered with minimal delay. Such real-time schemes can be combined with the single-stream energy-saving transmission schemes that were developed in this section: evaluating the combinations of the energy-saving transmission schemes with real-time transmission schemes are beyond the scope of this paper and are an interesting direction for future work. "
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    ABSTRACT: Quality of service (QoS) is an important consideration in networking, but it is also a significant challenge. Providing QoS guarantees becomes even more challenging when you add the complexities of wireless and mobile networks. This paper discusses the challenges and solutions involved in providing QoS in wireless data networks. Multiple techniques for providing service guarantees are presented, including data link layer QoS schemes, network layer schemes, integrated (multiple layer) approaches, QoS routing, dynamic class adaptation, and techniques for reservation and admission control.
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