Tauseef Jamal

Relay selection approaches for wireless cooperative networks

Wireless networks are characterized by having limited resources accessed by a large number of mobile stations with distinct capabilities. In such challenged environment the dynamic control of resources is of major importance to mitigate the limitations of wireless networks, such as the impact of low data rate stations and wireless channel oscillations. Such augmented usage of wireless resources can be implemented based upon cooperative relaying schemes, which have the potential to support the desired system performance and network lifetime. However, the introduction of cooperative relay raises several problems such as the issue for relay selection and resource allocation. Due to the significant number of different cooperative relaying approaches, this article aims to provide a systematic analysis and classification of major relay selection procedures, and to identify open research directions as well as the most suitable evaluation methods for an efficient analysis of different approaches.

Interference-aware opportunistic relay selection

Recently, cooperative relaying techniques have been investigated to increase the performance of wireless systems by using diversity created by different single antenna devices. With the introduction of cooperative relaying, relay selection requires special attention, since it has a strong impact on transmission performance. Moreover, cooperation procedures may be very unstable when relay selection relies on current channel conditions and is agnostic of interference induced by simultaneous transmissions. As a result, the performance of cooperative relaying in realistic scenarios may be very different from interference-free scenarios that have been the focus of most of the existing proposals so far.

Opportunistic Relay Selection for Wireless Cooperative Network

Advances in wireless technologies, including more powerful devices and low cost radio technologies, have potential to drive a ubiquitous utilization of Internet services. Nevertheless, wireless technologies face performance limitations due to unstable wireless conditions and mobility of devices. In face of multi-path propagation and low data rate stations, cooperative relaying promises gains in performance and reliability for low-cost single antenna devices. However, cooperation procedures may be very unstable when relay selection relies on current Channel State Information (CSI) and is agnostic of interference induced by concurrent transmissions and local CPU load. As a result, the performance of cooperative relaying in realistic scenarios may be very different from interference-free scenarios that have been the focus of most of the existing proposals so far. In a clear contrast to prior art we propose an opportunistic relay selection mechanism that is aware of interference and agnostic of channel status.

Analysis of hybrid relaying in cooperative WLAN

An ever-growing demand for higher data-rates has facilitated the growth of wireless networks in the past decades. Nevertheless, wireless technologies face performance limitations due to unstable wireless conditions and mobility of devices. In face of multi-path propagation and low data-rate stations, cooperative relaying promises gains in performance and reliability. However, cooperation procedures are unstable and introduce overhead that can endanger performance. In this paper we analyze the performance of a hybrid relaying protocol build based on the combination of opportunistic and broadcast-based relaying approaches. Hybrid relaying aims to increase the transmission capacity of wireless networks (proactive operation) when compared to proactive opportunistic and broadcast-based approaches due to rectifying the setbacks involved in those approaches, while adding a reactive approach to recover from failed transmissions.

Cooperative relaying in user-centric networking under interference conditions

An ever-growing demand for pervasive Internet access has boosted the deployment of wireless local networks in recent decades. Nevertheless, wireless technologies face performance limitations due to unstable propagation conditions and mobility of devices. In face of multi-path propagation and low-data-rate stations, cooperative relaying promises gains in performance and reliability. However, cooperation procedures are unstable, due to their dependence on current channel conditions, and introduce overhead that can endanger performance, especially when nodes are mobile. This article presents an introduction to cooperative relaying, and describes a novel link layer protocol, called RelaySpot, able to implement cooperative relaying in dynamic networks, based on opportunistic relay selection, cooperative relay scheduling, and switching.

Cooperative Networking in User-Centric Wireless Networks

Mobile social networking is becoming a new trend allowing users to have instant and real-time access from their devices to any Internet based networking platform. This requirement is not fulfilled by current wireless networks, which provide a limited number of wireless access points with instant Internet access. However, the flexibility of wireless technologies is giving rise to new types of wireless access networks, allowing the Internet to expand in a user-centric way. This new user-centric wireless networking trend aims to mitigate such problems, by allowing sharing of wireless resources for a faster and ubiquitous Internet access. The European project ULOOP—User-centric Wireless Local Loop is investigating new ways of deploying wireless local loops by means of low-cost technologies, where resource sharing is backed up by specific cooperation incentives and mechanisms. This paper aims to introduce the new concept of user-centric networks, an analysis of the most relevant incentive models, and a cooperative networking model to sustain the deployment of low-cost user-centric wireless networks based on cooperation incentives and mechanisms.

Cooperative Relaying in User-Centric Wireless Networks

An ever-growing demand for pervasive Internet access has boosted the deployment of wireless local networks in the past decades. Nevertheless, wireless technologies face performance limitations due to unstable propagation conditions and mobility of devices. In face of multi-path propagation and low data rate stations, cooperative relaying promises gains in performance and reliability. However, cooperation procedures are unstable (dependency upon current channel conditions) and introduce overhead that can endanger performance, especially when nodes are mobile. In this paper we describe a novel protocol, called RelaySpot, able to implement cooperative relaying in dynamic networks, based upon opportunistic relay selection, and cooperative relay scheduling and switching. RelaySpot removes the need for estimation and broadcast of channel conditions, and is expected to improve the utilization of spatial diversity, minimizing outage and increasing the transmission capacity of wireless local networks.

Cooperative Relaying for Wireless Local Area Networks

The concept of cooperation in wireless communication networks has drawn significant attention recently from both academia and industry as it can be effective in addressing the performance limitations of wireless networks due to user mobility and the scarcity of network resources. Future wireless systems are provisioned to be highly heterogeneous and interconnected, motivating cooperative relaying to be applied to future mobile networks. This chapter describes the state of the art in this area classified in different families. The main focus is the Medium Access Control (MAC) layer design, analysis, challenges and how cooperative networks can be designed for highly dynamic networks comprising large number of moving nodes.