QoS Requirements Of Real-time Applications Research Articles

Energy efficient QoS routing and adaptive status update in WMSNs

Multimedia sensors have shifted the focus from traditional scalar sensors to sensors equipped with multimedia devices. The characteristics of multimedia services impose more resource constraints on wireless multimedia sensor networks (WMSNs) including energy consumption, memory, bandwidth, and processing capabilities. Meeting a good quality of multimedia services within aforementioned constraints is a real challenge. On the other hand, existing routing solutions used in WMSNs suffer from limitations in term of QoS and energy efficiency. These routing protocols must take into consideration the QoS requirements and resource constraints nature of WMSN. In this paper, we propose an adaptive status update method that eliminates the drawbacks of periodic beaconing, and a QoS routing solution that considers the QoS requirements of real-time applications by prioritising the different traffic types. The performance evaluations of the solutions prove a significant reduction in the energy consumption and a fair distribution of the traffic and the energy consumption among the different sensor nodes while guaranteeing a good QoS during the routing of multimedia traffic.

IEEE 802.11에서 DCF 성능 향상을 위한 백오프 알고리즘

IEEE 802.11 MAC은 노드들간에 매체 접근을 제어하기 위해 DCF를 사용한다. 하지만 DCF 자체로는 실시간 데이터 전송에 필요한 QoS 요구사항을 만족시킬 수 없다. 이를 보완하기 위해 802.11 MAC에서 제공되는 DCF 기능을 수정하여 QoS를 제공하는 다양한 기법들이 나왔다. 본 논문에서는 DCF 기능을 향상시키기 위해 (m,k)-firm 기법을 이용하면서 IEEE 802.11에 근거한 (m,k)-collision 기법을 제시했다. 제시된 기법은 노드에서 발생되는 충돌 횟수에 따라 서로 다른 CW 값을 할당한다. 시뮬레이션 결과 제시된 기법이 DCF의 처리율 향상에 도움을 주고 있다는 것을 보여준다. The IEEE 802.11 MAC uses DCF for media access among the participating network nodes. But DCF alone is neither capable nor suitable for fulfilling the QoS requirements of realtime applications. There are many ways in which QoS is provided by modifying DCF based MAC. This paper proposes (m,k)-collision scheme which is based on IEEE 802.11 and (m,k)-firm scheme tries to improve DCF functionality. The proposed scheme uses different Contention Window according to the number of collision in the node. The simulation result shows that the proposed scheme helps improve the throughput of the DCF.

Quality Estimation of Bandwidth in a Network

The available bandwidth (avail-bw) in a network path is of major importance in congestion control, streaming applications, quality-of-service verification, server selection, and overlay networks. In a packet network, the terms bandwidth and throughput often characterize the amount of data that the network can transfer per unit of time. Bandwidth estimation are also important for traffic engineering and capacity planning support. We propose a QoS-aware routing protocol that incorporates an admission control scheme and a feedback scheme to meet the QoS requirements of real-time applications. Results of our experiments show that the packet delivery ratio increases, and packet delay and energy dissipation decrease significantly, while the overall end-to-end throughput is not impacted, compared with routing protocols that do no provide QoS support. Nevertheless, the load is better balanced in the network, therefore the network capacity is not overloaded. The result in more stable routes and less control traffic as almost no reconstructions are needed.

An adaptive QoS guaranteeing MAC protocol for real-time traffic in TDMA-based wireless ATM networks

This paper presents a new media access control (MAC) protocol based on forward error control (FEC), which is appropriate for supporting real-time traffic with strict QoS requirements in wireless ATM networks. As the channel BER in wireless environments is very high and varying 10 −5–10 −2, previous schemes that use powerful FEC have combated to overcome this noisy channel condition at the cost of valuable bandwidth. As most previous works have been dedicated to maximize the channel efficiency, they were not able to meet QoS requirements of real-time applications in wireless networks. A new MAC protocol proposed in this paper is designed to guarantee the throughput requested by a real-time traffic user while keeping the bandwidth consumption at a minimum. The proposed scheme is for a TDMA system and uses adaptive FEC. We analyze the wireless channel and model it as a two-state error control system to design an efficient MAC protocol. We use simulation experiments to show how the proposed scheme provides QoS guarantees, and compare it with the CDMA system in terms of capacity, i.e. the number of users that can be supported.