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Abstract
This paper considers the problem of providing relative service differentiation in IEEE 802.11 Wireless LAN by using different Medium Access Control (MAC) parameters for different service classes. We present an analytical model which predicts the saturation throughput of IEEE 802.11 Distributed Coordination Function with multiple classes of service. This model allows us to show that relative service differentiation can be achieved by varying the initial contention window alone. In this case, the saturation throughput of a station can be shown to be approximately inversely proportional to the initial contention window size being used by that station. The simulation results validate our analytical model.
... DCF has been extensively studied for saturation conditions [4] [5]. With respect to performance analysis, IEEE 802.11e can achieve relative service differentiation such as throughput or delay in saturated conditions [6] [7][8] [9]. Because the unsaturated case is more typical, analysis of IEEE802.11 ...
... The analytical model is also suitable for performance analysis of 802.11e in unsaturated conditions. Since the relative service differentiation can be achieved by varying the initial contention window alone [6], we consider the service differentiation schemes only by using W. We assumed that there is only one queue in each station, which can be looked at as a special case of IEEE 802.11e. We assume that all the stations are divided into N service classes and the number of stations in the ith service class is n i , the initial contention window of stations in service class i is W ...
... The analytical and simulation results including throughput and mean MAC service time are shown in Fig. 9 and Fig. 10, which indicate the accuracy of the model. As the total load tends to saturated status, the analytical results tend to the same as that in [6]. However, for the specific MAC settings, the service differentiation scheme could hardly achieve performance differentiation such as throughput or MAC service delay when the load is less than the optimal value. ...
IEEE 802.11 standard has achieved huge success in the past decade and is still under development to provide higher physical data rate and better quality of service (QoS). An important problem for the development and optimization of IEEE 802.11 networks is the modeling of the MAC layer channel access protocol. Although there are already many theoretic analysis for the 802.11 MAC protocol in the literature, most of the models focus on the saturated traffic and assume infinite buffer at the MAC layer. In this paper we develop a unified analytical model for IEEE 802.11 MAC protocol in ad hoc networks. The impacts of channel access parameters, traffic rate and buffer size at the MAC layer are modeled with the assistance of a generalized Markov chain and an M/G/1/K queue model. The performance of throughput, packet delivery delay and dropping probability can be achieved. Extensive simulations show the analytical model is highly accurate. From the analytical model it is shown that for practical buffer configuration (e.g. buffer size larger than one), we can maximize the total throughput and reduce the packet blocking probability (due to limited buffer size) and the average queuing delay to zero by effectively controlling the offered load. The average MAC layer service delay as well as its standard deviation, is also much lower than that in saturated conditions and has an upper bound. It is also observed that the optimal load is very close to the maximum achievable throughput regardless of the number of stations or buffer size. Moreover, the model is scalable for performance analysis of 802.11e in unsaturated conditions and 802.11 ad hoc networks with heterogenous traffic flows. © 2012 KSI.
... There are many literatures which have analyzed the CSMA-CA by using a discrete-time Markov chain model in IEEE 802.11 distributed coordination function [2][3][4][5][6] and in IEEE 802.15.4 ...
... Equation (5) is the probability of empty queue which was empty in the previous state. Equation (6) shows the probability of going back to the first backoff stage from the idle stage. Equation (7) represents the reducing of backoff counter. ...
Priority MAC is an important issue in every communication system when we consider differentiated service applications. In this paper, we propose a mechanism to support priority MAC based on multi-parameters for IEEE 802.15.7 visible light communication (VLC). By using three parameters such as number of backoff times (NB), backoff exponent (BE) and contention window (CW), we provide priority for multi-level differentiated service applications. We consider beacon-enabled VLC personal area network (VPAN) mode with slotted version for random access algorithm in this paper. Based on a discrete-time Markov chain, we analyze the performance of proposed mechanism under non-saturation environments. By building a Markov chain model for multi-parameters, this paper presents the throughput and transmission delay time for VLC system. Numerical results show that we can apply three parameters to control the priority for VLC MAC protocol.
... In some circumstances, the DCF may use the RTS (Request To Send) and CTS (Clear To Send) technique to further prevent collisions. The saturation throughput performance of the DCF on the condition that all hosts in the network use the same transmission rate was analyzed in [1] [2] [3] [4]. The 802.11 protocols also define an optional Point Coordination Function (PCF) to enable the transmissions of timesensitive information. ...
... Therefore, the wireless channel is considered as a slowly changing medium in this paper. Our model is based on the ones proposed in [2] [3] and extended with the ARF protocol. A general architecture of this model is shown in Fig. 1, in which s/f is the current number of successes/losses and S/F is the maximum number of consecutive successes/losses before changing rates. ...
Abstract The IEEE 802.11 family of speciflcations is by far the most promi- nent and successful technique for accessing WLANs. Because the channel used by wireless devices is a time-varying broadcast medium, these devices need to have multi-rate and rate-adaptive capability to adapt to the changing channel so that better performance can be achieved. In this paper, we propose an analytical model, which we call Rate-Adaptive Markov Chains, to study the saturation through- put and delay performance of an 802.11 WLAN in which the mobile hosts have multi-rate support, will use the ARF protocol to adapt rates for difierent channel qualities, and follow the DCF protocol to contend for data transmissions in a slowly-varying channel. Simula- tion results are also provided to verify the correctness of the model.
... It also represents a significant modification to the original standard if it is to be adopted. In a number of cases a combination of two or more schemes is used [89][90][91][92] to come up with efficient service differentiation. In [89], a comparison of service differentiation based on these four approaches is presented. ...
Since IEEE802.11 ad hoc networks can not provide any priority scheme, a new scheme based on the 802.11 MAC (medium access control) protocol is proposed in this paper. The main idea is that, by introducing new types of control frames, receiving nodes may refuse to accept data of low-priority nodes. As a result, the QoS (quality of service) of high-priority data flow is effectively improved. On the other hand, a Markov chain model is used to analyze and evaluate the diffserv scheme mathematically, including saturation throughput, frame dropping probability and saturation delay. Our mathematical analyses demonstrate that the new mechanism can make the high-priority data flow obtain more bandwidth, and also reduce end-to-end delay and frame dropping probability.
A new service differentiation scheme based on packet arrival rate diversity is proposed for IEEE 802.11 WLAN. An analytical model is developed for performance evaluation. It's shown that the new scheme can achieve effective service differentiation and statistical throughput guarantee by controlling the total offered load. The scheme requires no modifications at 802.11 MAC layer. Simulation results validate the analytical model.
This paper presents a fair MAC protocol based on the CSMA/CA algorithm in visible light communication (VLC) networks. The problem of bandwidth sharing among differentiated priority in VLC networks can be solved by using number of backoff time and backoff exponent parameters with AIFS. The proposed algorithm can achieve fair allocation of the bandwidth resource among differentiated priority. The two dimension Markov chain is assisted for analyzing the proposed mechanism about throughput and delay metrics. Numerical results show that our proposed algorithm improves the fairness among different traffic flows.
Due to energy limit of sensors, lifetime maximization of wireless sensor network is one of the key problems protocol design. Low Energy Adaptive Clustering Hierarchy (LEACH) is a well known routing protocol in WSN, but its performance decreases sharply with increase of the network scale. To solve this problem, we introduce an improved LEACH routing protocol to balance energy consumption among the whole network. LEA CH-MF adopts the methods of multi-layer clustering and eliminates redundant information. Simulation results on NS2 show that the proposed protocol extends the survival time of the network and performs much better than LEACH protocol.
In order to support quality of service (QoS) in 802.11 wireless LAN, current research work as well as the enhanced DCF (EDCF) defined in 802.11e standard, tends to provide differentiated services by varying the parameters of MAC protocol. In this paper, we present an analytical model for performance evaluation of these service differentiation schemes in non-saturated traffic conditions. The analytical results show that neither significant throughput nor packet delay differentiation can be achieved by these schemes when the total load is less than the optimal value, which is quite different from that in saturated conditions. The simulation results validate the analytical model.
This paper proposes a simple but effective scheme for supporting quality of service (QoS) in IEEE 802.11 WLAN. A station will initiate a virtual contention process before every data packet from network layer being delivered to the 802.11 MAC layer. Service differentiation can be achieved by using different virtual contention windows. An analytical model is then presented for performance evaluation. Simulation results validate the analytical model. Our scheme requires no modifications at 802.11 MAC layer
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