The end-to-end throughput of multi-hop communication in wireless ad hoc networks is affected by the conflict between forwarding nodes. It has been shown that sending more packets than maximum achievable end-to-end throughput not only fails to increase throughput but also decreases throughput owing to high contention and collision. Accordingly, it is of crucial importance for a source node to know the maximum end-to-end throughput. The end-to-end throughput depends on multiple factors, such as physical layer limitations, medium access control (MAC) protocol properties, routing policy, and nodes’ distribution. There have been many studies on analytical modeling of end-to-end throughput but none of them has taken routing policy and nodes’ distribution as well as MAC layer altogether into account. In this paper, the end-to-end throughput with perfect MAC layer is obtained based on routing policy and nodes’ distribution in 1-D and 2-D networks. Then, imperfections of IEEE 802.11 protocol are added to the model to obtain precise value. An exhaustive simulation is also made to validate the proposed models using ns-2 simulator. Results show that if the distribution to the next hop for a particular routing policy is known, our methodology can obtain the maximum end-to-end throughput precisely.
In @cite_32 , throughput and stability results of single-hop CMSA CA network were obtained, but it is restricted due to the assumption that nodes freeze their arrival process during a back-off period @cite_24 . Furthermore, their analysis is only applicable for single-hop communication. In @cite_7 , a two-level modeling approach was used to model multi-hop wireless communication in which the first level is a slightly modified version of @cite_2 and the higher level model consists of M M 1 K queues representing each node in the network. The predication modeling framework also covers scenarios where two flows in opposite directions exist. Despite the claim that their model can handle any number of nodes, the scenarios they covered is limited to only four nodes. Additionally, routing is not considered in their study.
@cite_24 @cite_32 @cite_7 @cite_2
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CSMA CA is a popular random-access algorithm for wireless networks, but its stability properties are poorly understood. We consider a linear multi-hop network of three nodes where the neighbouring nodes interfere with each other and medium access is governed by the CSMA CA algorithm. We assume that the source node is saturated and packets are forwarded through the network, each node transmitting towards its neighbour on the right. We demonstrate that the queue of the second node is saturated (unstable) and the queue of the third node is stable; this confirms heuristic arguments and simulation results found in the research literature. Providing a rigorous proof for the (in)stability of these nodes is complicated by the fact that neither queue is Markovian when considered in isolation, and the two queues are dependent. We then compute the limiting behavior of node 3, and use this to determine the end-to-end throughput of the network. Finally, we vary the access probabilities of the nodes, and evaluate how this affects the stability and throughput of the system. Due to a poor understanding of the interactions among transmitters, wireless networks using carrier sense multiple access with collision avoidance (CSMA CA) have been commonly stigmatized as unpredictable in nature. Even elementary questions regarding the throughput limitations of these networks cannot be answered in general. In this paper, we investigate the behavior of wireless CSMA CA networks to understand how the transmissions of a particular node affect the medium access, and ultimately the throughput, of other nodes in the network. We introduce a theory which accurately models the behavior of these networks and show that, contrary to popular belief, their performance is predictable and can be described by a system of equations. Using the proposed theory, we provide the analytical expressions necessary to fully characterize the capacity region of any wireless CSMA CA network. We show that this region is nonconvex in general and agnostic to the probability distributions of all network parameters, depending only on their expected values. Our theory is also shown to extend naturally to time division multiple access (TDMA) networks and to predict how the network responds to infeasible input rates. Multi-hop wireless networks are often regarded as a promising means to extend the limited coverage area offered by WLANs. However, they are usually associated with poor and uncertain performance in terms of available bandwidth and packet losses, which clearly stands as a limitation to their use. In this paper, we consider the performance evaluation of a multi-hop path (also called chain), based on the IEEE 802.11 DCF. The proposed modeling framework is constructive and versatile, so that it can handle various types of multi-hop wireless paths, including scenarios with two flows in opposite directions, and topologies where nodes are exposed to the well-known hidden node problem. The models derived from our framework are conceptually simple, easy to implement and produce generally accurate results for the attained goodput of flows, as well as the datagram loss probability. Typical relative errors for these two quantities are below a few percent. Also, fundamental phenomena occurring in multi-hop wireless networks, such as performance collapse and starvation, are well captured by the models. The IEEE has standardized the 802.11 protocol for wireless local area networks. The primary medium access control (MAC) technique of 802.11 is called the distributed coordination function (DCF). The DCF is a carrier sense multiple access with collision avoidance (CSMA CA) scheme with binary slotted exponential backoff. This paper provides a simple, but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions. The proposed analysis applies to both the packet transmission schemes employed by DCF, namely, the basic access and the RTS CTS access mechanisms. In addition, it also applies to a combination of the two schemes, in which packets longer than a given threshold are transmitted according to the RTS CTS mechanism. By means of the proposed model, we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.