Bandwidth allocation in cooperative wireless networks: Buffer load analysis and fairness evaluation.

In modern cooperative wireless networks, the resource allocation is an issue of major significance. The cooperation of source and relay nodes in wireless networks towards improved performance and robustness requires the application of an efficient bandwidth sharing policy. Moreover, user requirements for multimedia content over wireless links necessitate the support of advanced Quality of Service (QoS) features. In this paper, a novel bandwidth allocation technique for cooperative wireless networks is proposed, which is able to satisfy the increased QoS requirements of network users taking into account both traffic priority and packet buffer load. The performance of the proposed scheme is examined by analyzing the impact of buffer load on bandwidth allocation. Moreover, fairness performance in resource sharing is also studied. The results obtained for the cooperative network scenario employed, are validated by simulations. Evidently, the improved performance achieved by the proposed technique indicates that it can be employed for efficient traffic differentiation. The flexible design architecture of the proposed technique indicates its capability to be integrated into Medium Access Control (MAC) protocols for cooperative wireless networks

Cooperative handoff in wireless networks

In 802.11-based wireless networks the stations (STAs) are associated with the available access points (APs) and communicate through them. In traditional handoff schemes the STAs get information about the active APs in their neighborhood by scanning the available channels and listen to transmitted beacons. This paper proposes a 802.11k compliant framework for cooperative handoff where the STAs are informed about the active APs by exchanging information with neighboring STAs. In this way we minimize the delay of the scanning procedure. We evaluate the performance of our mechanisms through simulations and we show that when our cooperative framework is applied the network performance is significantly improved. Consequently, our system is more capable in meeting the needs of QoS-sensitive applications. © 2008 IEEE

CDR-MAC: A protocol for full exploitation of directional antennas in ad hoc wireless networks

In this paper, we propose a new Medium Access Control (MAC) protocol for full exploitation of directional antennas in wireless networks. The protocol introduces a circular directional transmission of the Request To Send (RTS) control packet, spreading around a station information about the intended communication. The stations that receive the directional RTS, using a simple scheme of tracking the neighbors' directions, defer their transmission toward the beams that could harm the ongoing communication. In this way, the proposed protocol takes advantage of the benefits of directional transmissions as the increase of spatial reuse and of coverage range. Additionally, it reduces the hidden-terminal problem, as well as the deafness problem, two main factors for the decrease of the efficiency of directional transmissions in ad hoc networks. The performance evaluation of the protocol shows that it offers a significant improvement in static, as well as mobile, scenarios, as compared to the performance of the proposed protocols that use omnidirectional or directional transmissions

A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks

Directional antennas in ad hoc networks offer many benefits compared with classical omnidirectional antennas. The most important include significant increase of spatial reuse, coverage range and subsequently network capacity as a whole. On the other hand, the use of directional antennas requires new approach in the design of a MAC protocol to fully exploit these benefits. Unfortunately, directional transmissions increase the hidden terminal problem, the problem of deafness and the problem of determination of neighbors' location. In this paper we propose a new MAC protocol that deals effectively with these problems while it exploits in an efficient way the advantages of the directional antennas. We evaluate our work through simulation study. Numerical results show that our protocol offers significant improvement compared to the performance of omni transmissions

An 802.11k Compliant Framework for Cooperative Handoff in Wireless Networks

In IEEE 802.11-based wireless networks, the stations (STAs) are associated with the available access points (APs) and communicate through them. In traditional hando. schemes, the STAs get information about the active APs in their neighborhood by scanning the available channels and listening to transmitted beacons. This paper proposes an 802.11k compliant framework for cooperative hando. where the STAs are informed about the active APs by exchanging information with neighboring STAs. Besides, the APs share useful information that can be used by the STAs in a hando. process. In this way, we minimize the delay of the scanning procedure. We evaluate the performance of our mechanisms through OPNET simulations. We demonstrate that our scheme reduces the scanning delay up to 92%. Consequently, our system is more capable in meeting the needs of QoS-sensitive applications. Copyright (C) 2009 George Athanasiou et al

Routing-aware channel selection in multi-radio mesh networks

Efficient channel selection is essential in 802.11 mesh deployments, for minimizing contention and interference among co-channel devices and thereby supporting a plurality of QoS-sensitive applications. In this paper, we propose ARACHNE, a routing-aware channel selection protocol for wireless mesh networks. ARACHNE is distributed in nature, and motivated by our measurements on a wireless testbed. The main novelty of our protocol comes from adopting a metric that captures the end-to-end link loads across different routes in the network. ARACHNE prioritizes the assignment of low-interference channels to links that (a) need to serve high-load aggregate traffic and/or (b) already suffer significant levels of contention and interference. Our protocol takes into account the number of potential interfaces (radios) per device, and allocates these interfaces in a manner that efficiently utilizes the available channel capacity. We evaluate ARACHNE through extensive, trace-driven simulations. We observe that our protocol improves the total network throughput, as compared to three other channel allocation strategies. ©2009 IEEE

Enabling sensing and mobility on wireless testbeds

The inherent inability of simulation models to adequately express factors such as wireless signal propagation etc., can lead to incomplete evaluation of wireless protocols and applications. Thus, testing of proposed schemes under real-life settings has become the de facto validation process. More specifically, in the context of testing scenarios that include mobility, evaluation in real environments becomes a prerequisite. Networking testbeds have recently extended their capabilities by providing the researchers with the ability to include mobile nodes in their experiments as well. Towards this direction, we have developed a prototype mobile node in NITOS, which features a mounted camera and wireless interfaces that enable remote access and control. The proposed mobility framework is also accompanied by a graphical user interface that allows the experimenter to observe the node's behavior remotely. © 2012 ICST Institute for Computer Science, Social Informatics and Telecommunications Engineering

LAC: Load-aware channel selection in 802.11 WLANs

Dense deployments of hybrid WLANs result in high levels of interference and low end-user throughput. Many frequency allocation mechanisms for WLANs have been proposed by a large body of previous studies. However, none of these mechanisms considers the load that is carried by APs in terms of channel conditions, number of affiliated users as well as traffic-load, in conjunction. In this paper, we propose LAC, a load-aware channel allocation scheme for WLANs, which considers all the above performance determinant factors. LAC incorporates an airtime cost metric into its channel scanning process, in order to capture the effects of these factors and select the channel with the maximum long-term throughput. We evaluate LAC through extensive OPNET simulations, for many different traffic scenarios. Our simulations demonstrate that LAC outperforms other frequency allocation policies for WLANs in terms of total network throughput by up to 135%. © 2008 IEEE