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Spatial diversity for wireless transmission requires more than one antenna at the transmitter. However, mobile devices are usually limited by size, so installation of multiple antennas increases the hardware complexity significantly. Due to the omnidirectional nature of wireless signal, a data transmission between a source node and a destination node can be overheard by many other neighbor nodes....
The inconvenience of transportation frequently causes delay in health care for home-dwelling patients with chronic diseases, resulting in inequality of medical care. This paper proposes a Telemonitoring System (WiMAX Telemonitoring Service) framework for monitoring and delivering health care service to home-dwelling chronic hypertension patients, with the idea of improving the accessibility of medical...
Various application services including multimedia applications need efficient multicast technologies, but the IEEE 802.11 protocol, which is currently the most widely used, does not specify the standard on multicast, which is, instead, substituted by broadcast or a combination of unicast. Using broadcast is, however, difficult to judge on the transmission success or fail, because it does not receive...
Network coding has been studied as a solution to mitigate traffic concentration at a bottleneck node in wireless multihop networks. When network coding is applied to a unicast flow, the decoding nodes overhear packet transmissions, receive all packets which are headed for not only themselves but also the other nodes, and store them. The reception of undesired packets is, however, unreliable, and this...
In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop...
There are real challenges in both the IEEE 802.11 wireless local area network (WLAN) protocol and the medium access control (MAC)-functions providing the required quality-of-service, high throughput and minimum latencies. The IEEE 802.11 layer supports both the distributed coordination function (DCF) and the enhanced DCF (EDCF). The different access categories (AC) within the EDCF can enhance the...
We propose a device discovery approach and connection establishment scheme for opportunistic networks using Ad-Hoc Wi-Fi as the underlying communication technology. We employ beacon stuffing method for a device to announce its existence in its neighborhood by broadcasting beacons stuffed with useful information in the field of SSID to remote devices. This method can allow a device to discover multiple...
In the last years, there has been an increasing interest in developing and testing Medium Access Control (MAC) protocols for ad hoc networks based on optimal methods. Several solutions do not take into account the throughput-fairness tradeoff, presenting high throughput performance but under-performing in terms of medium access fairness. This work presents a novel MAC scheme, which is designed to...
In the last years, there has been an increasing interest in developing and testing Medium Access Control (MAC) protocols for ad hoc networks based on optimal methods. The solutions already proposed in several works are generally hard to implement because they require extensive message passing among the nodes. Moreover, a relaxation for the optimal solution is generally needed to achieve an implementable...
WLAN systems based on the IEEE 802.11 could contain hundreds even up to thousands of wireless access points nowadays. However, IEEE 802.11 MAC protocols, including DCF, PCF and EDCA mechanisms, are unable to meet the challenges to provide collision freedom, especially in distributed large scale WLAN systems. We propose a channel access scheduling protocol based on Latin squares, called DCLASS (Distributed...
In this paper, we discuss the challenges associated with integrating multiuser OFDMA in a single cell IEEE 802.11 based wireless ad hoc network and propose a new, dynamic and robust approach to improve it. Our new MAC, using OFDMA in the physical layer, can incorporate multiple concurrent transmissions or receptions in a dynamic manner and can adjust the collision probability based on the traffic...
Many modern wireless data networks employ Carrier Sense Multiple Access (CSMA) for efficient medium access. The p-persistent CSMA protocol is an analytically tractable version of CSMA that has been used successfully to model practical medium access protocols such as the IEEE 802.11 Distributed Coordination Function (DCF). We present a closed-form expression to characterize the access probabilities...
The MAC protocol is important, especially for wireless LAN because of limited bandwidth. A great deal of research has been carried out and some of proposed schemes are effective. Specifically, considerable effort has been devoted to improving the IEEE 802.11 standard which is utilized widely. Previous theoretical analysis gave the upper bound of IEEE 802.11 DCF throughput which is far below the channel...
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...
Electronic services (mail, web, etc.) can operate, at present over wireless networks. 802.11 networks are an example, where wireless devices use its resources to access to networks and services and in particular to Internet. The security mechanisms in the MAC layer are added to existing security mechanisms in other layers of the TCP/IP model, and therefore it generates multiple encryption of information...
One of the main challenges in wireless industrial networks is the delay caused by shared, error-prone and non-deterministic behavior of wireless communication medium. In this paper, delay statistics of IEEE 802.11e prioritized MAC layer and the improvement caused by using a Spatial Multiplexing (SM) scheme for the IEEE 802.11e-based Soft-Real-Time Wireless Industrial Networks has been analyzed. Using...
We analyze TCP-controlled bulk file transfers in a single station WLAN with nonzero propagation delay between the file server and the WLAN. Our approach is to model the flow of packets as a closed queueing network (BCMP network) with 3 service centres, one each for the Access Point and the STA, and the third for the propagation delay. The service rates of the first two are obtained by analyzing the...
Analytical studies of Medium Access Control (MAC) layer protocols can be used to improve the performance of multi-hop Wireless Sensor Networks (WSNs) in the presence of hidden stations. The selected MAC layer protocol should conform to the distributed nature of the WSNs. The IEEE 802.11 MAC layer with Distributed Coordination Function (DCF) is well suited to WSNs. Analytical studies of IEEE 802.11...
The paper studies bandwidth distribution among a set of rational multihomed wireless terminals (WTs). Based on network feedback information (NFI), each WT selects an available wireless network so as to self-optimize a utility derived from received bandwidth. Using game-theoretic tools we show how to disincentivize “aggressive” MAC configuration and quantify the role of the speed of NFI generation...
This paper presents a new MAC (Medium Access Control) spoofing detection algorithm in IEEE 802.11 networks. The proposed algorithm utilizes PLCP (Physical Layer Convergence Protocol) header of IEEE 802.11 frames to differentiate an attacker station from a genuine station. PLCP header of IEEE 802.11 frames maybe change for each frame. It depends on transmission rate adaptation algorithm which is designed...
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