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IEEE 802.15.4 Medium Access Control (MAC) layer does not include the Request-To-Send/Clear-To-Send (RTS/CTS) handshake mechanism, in order to overcome the hidden node problem that affects Wireless Sensor Networks (WSNs). In this paper we propose and analyse the use of RTS/CTS in IEEE 802.15.4 for the nonbeacon-enable mode. The proposed solution shows that by considering the RTS/CTS mechanism combined...
Since the seminal work of Gupta and Kumar, extensive research has been done on studying the capacity of large wireless networks under various scenarios. Most of the existing work focuses on studying the capacity of networks with uniformly or Poissonly distributed nodes. While uniform and Poisson distribution form an important class of spatial distributions, their capability in capturing the spatial...
The conventional hierarchical cooperation (HC) scheme proposed by Ozgur et al. [1] is a novel communication scheme that can achieve linear capacity scaling, O(N) in wireless ad-hoc network from the viewpoint of information theory without considering control and data overhead. In this paper, we investigate the effects of practical parameters such as packet arrival rate, control overhead and data overhead...
In this paper, we propose an analytical model to evaluate the maximum stable throughput of a cognitive IEEE 802.11-based WLAN sharing the downlink band of a cellular network. Our model has been found on an open queueing network which includes both asymmetric and non-saturated aspects of secondary nodes as well as the time-varying nature of the channel due to intermittent primary nodes. By mapping...
With the popularization of Internet and formation of wireless technologies provide significant impact on Internet and Communication Technologies. These technologies have support of one of famous technique known as Adhoc Network. Adhoc Networks are assortment of mobile nodes connected by wireless links and also receiving attention in the scientific community. In adhoc networks, routes may be disconnected...
This paper addresses the problem of MAC performance evaluation of a contemporary IEEE 802.11 WLAN. The network is observed under saturation conditions and the packet transmission probability analysis is conducted with the novel regenerative approach. The proposed model accounts for collision resolution protocol parameters, packet retry limit, coexistence of unicast and broadcast traffic, and heterogeneous...
In this paper, we investigate a new power allocation scheme for a multi-user orthogonal frequency division multiplex (OFDM) system, in which two cooperative power sources (CPS) coordinately transmit their power to multiple orthogonal subchannels. In order to maximize the sum rate, a closed form solution is obtained by analytical derivation. Based on the derived solution, we present a novel joint optimal...
A novel dynamic contention window control scheme is presented in this paper to improve the performance and energy efficiency of IEEE 802.11-based CSMA/CA DCF wireless networks operating in ad-hoc mode. The number of competing nodes in physical carrier sense systems is one of the major impact on DCF performance and on the energy consumed. A new approach in presented in this paper is using a cross layer...
Since the IEEE 802.11 standard supports multiple data rates at the physical layer, many rate adaptation mechanisms have been proposed to utilize this multi-rate capability by dynamically switching rates in response to different channel conditions. In IEEE 802.11b networks, the guarantee of an equal transmission opportunity for all participating nodes results in performance anomaly. Traditional solutions...
Estimating the throughput of an WiFi connection can be quite complex, even when considering simplified scenarios. Indeed, the varying number of parameters specified in the standards makes it hard to understand their impact in terms of delay and throughput. The main contribution of this work is to present a simple scheme to compute the exact maximum throughput for an IEEE 802.11g network. The proposed...
Congestion in mobile ad hoc networks not only results in transmission delay and packet loss, but also degrades throughput. For effective congestion detection and control, accurate estimation of MAC overhead, packet retransmission, backoff interval and queuing delay is necessary. This paper proposes a congestion aware nodes (CAN) based scheme to control congestion in mobile ad hoc networks. In this...
In wireless ad hoc network, hidden and exposed node problem can cause the throughput performance degradations. Hidden Node (HN) allows to transmit but interferes with the receiver causes collision and Exposed Node (EN) does not allows to transmit although they would not interfere. In this paper, an Enhanced QoS model is designed to combat hidden and exposed node problem in an ad hoc network by applying...
In Vehicular Ad Hoc Network (VANET), the route between a source node and a destination node is intermittently broken. It is difficult to provide the reliable data transfer based on TCP because TCP is not adaptable to such networks such as VANET. Therefore, this paper proposes an end-to-end transfer rate adjustment mechanism in the application layer for VANET. The proposed mechanism consists of three...
The main concerns of network performance are throughput, end-to-end packet delay and packet loss. A high-performance network is characterized by high throughput, small delay, and low packet loss. A larger transmission radius increases the probability of finding a receiver with large progress, but simultaneously increases the probability of collision with other transmissions. Transmission range and...
Routing protocols for sparse mobile ad hoc networks are becoming important due to applications such as vehicular networks and emergency services. Simulation based performance evaluation of a given protocol is computationally demanding, requiring a significant amount of time and resources. For this reason, analytical approaches to performance evaluation are desirable; however, such approaches are challenging...
In this paper we introduce a new MAC protocol called Continuous Contention-Assisted Transmission (CAT) for wireless Ad-hoc network. This proposed protocol is based on Carrier sense multiple access with collision avoidance (CSMA/CA) but we have modified the ACK packet and re-designed mobile stations behavior so that they could continuously transmit data without contention. Our proposed algorithm tries...
It is well-known that the values of IEEE 802.11 MAC parameters directly affect the utilization of the channel capacity and link layer throughput as well as higher layers performance. This paper first studies the throughput of ad hoc network under various 802.11 MAC parameters by developing a 3-dimensional Markov chain. Based on this model, it is mathematically proved that the current values of 802...
This paper analyzes the performance of enhanced relay-enabled distributed coordination function (ErDCF) for wireless ad hoc networks under transmission errors. The idea of ErDCF is to use high data rate nodes to work as relays for the low data rate nodes. ErDCF achieves higher throughput and reduces energy consumption compared to IEEE 802.11 distributed coordination function (DCF) in an ideal channel...
In this paper, we focus on an equation based single rate TCP-Friendly Multicast Congestion Control (TFMCC) protocol, primarily proposed for wired networks. In TFMCC, the rate is determined as a function of packet loss ratio (PLR), round trip time (RTT) and packet size, where each receiver estimates its throughput at each RTT, using an equation that estimates the steady-state throughput of a TCP source...
Inefficient resource management may cause problems of reliability of service in shared medium wireless networks. Resources include bandwidth, processor cycles and buffers. Excessive competition for these resources can cause severe packet collision rates, compound network congestion, or even result in starvation of some nodes. In such a situation, data transmission is subject to very long delays and...
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