Performance Evaluation of a Helper Initiated Distributed Cooperative Medium Access Control Protocol for Wireless Networks

Cross layer cooperative protocol which exploits the benefits of physical layer cooperative communication, is one of the widely recognized MAC layer protocol design strategies for future wireless networks. This paper presents performance analysis of a cooperative mac and these performance parameters are compared those of the legacy IEEE 802.11 DCF MAC. Appropriate relay station selection is the main hurdle in designing efficient cooperative MAC protocol for wireless networks.  This cooperative mac demonstrated that intermediate relay nodes themselves can initiate cooperation for relaying data frame to the receiver on behalf of the sender. This procedure makes the selection process of a “helper node” more distributed in nature as well as it contributes to increase throughput of a wireless network by reducing the overheads that are usually incurred in the helper selection process. It has been shown by thorough analytical analysis that the proposed cooperative MAC protocol offers higher throughput and lower frame transmission delay in both ideal and error prone wireless environment. These performance metrics are also evaluated while the wireless nodes are mobile as well

Performance Evaluation of a Helper Initiated Distributed Cooperative Medium Access Control Protocol for Wireless Networks

Cross layer cooperative protocol which exploits the benefits of physical layer cooperative communication, is one of the widely recognized MAC layer protocol design strategies for future wireless networks. This paper presents performance analysis of a cooperative mac and these performance parameters are compared those of the legacy IEEE 802.11 DCF MAC. Appropriate relay station selection is the main hurdle in designing efficient cooperative MAC protocol for wireless networks.  This cooperative mac demonstrated that intermediate relay nodes themselves can initiate cooperation for relaying data frame to the receiver on behalf of the sender. This procedure makes the selection process of a “helper node” more distributed in nature as well as it contributes to increase throughput of a wireless network by reducing the overheads that are usually incurred in the helper selection process. It has been shown by thorough analytical analysis that the proposed cooperative MAC protocol offers higher throughput and lower frame transmission delay in both ideal and error prone wireless environment. These performance metrics are also evaluated while the wireless nodes are mobile as well

Cooperative diversity architecture for wireless networks

The burgeoning demand for wireless networks necessitates reliable and energy-efficient communication architectures that are robust to the impairments of the wireless medium. Cooperative communication emerges as an appropriate technique that mitigates the severe effects of channel impairments through the use of cooperative diversity. Notwithstanding the fact that cooperative diversity is a very suitable technique to provide robust and reliable communication, the realization of cooperation idea precipitates many technical challenges that are associated with the overhaul of the wireless network design. This dissertation proposes a cooperative diversity architecture for wireless networks, that spans the physical, medium access and routing layers with parameters (jointly) optimized for overall system performance, taking into account the cost of cooperation in each layer. First, we present a new cooperative MAC protocol, COMAC, that enables cooperation of multiple relays in a distributed fashion. Through the proposed protocol, we investigate and demonstrate at what rate and for which scenarios cooperation brings benefits in terms of throughput and energy-efficiency. Our results demonstrate that cooperation initiation has a significant cost on both the throughput and energy-efficiency, which have been often disregarded in the literature. We next study the energy minimal joint cooperator selection and power assignment problem under transmit power constraints such that the cooperative transmissions satisfy an average bit error rate (BER) target. We derive the average BER of the cooperative system and we propose a simple yet close approximation to facilitate cooperator selection methods with closed form power assignment solutions. We formulate the joint cooperator selection and power assignment problem, we present the optimal solution (O-CSPA) and we also propose a distributed implementation (D-CSPA). Our results demonstrate that smart cooperator selection is essential, as it provides efficient resource allocation with reduced overhead leading to improved system performance. Our implementation and simulations of D-CSPA algorithm in COMAC protocol demonstrate that our distributed algorithm causes minimal overhead, yields improved throughput and reduced delay, while reducing the energy consumption. Finally, we propose a cooperative routing framework and a cross-layer architecture, RECOMAC, for wireless ad hoc networks. The RECOMAC architecture facilitates formation of cooperative sets on the fly in a decentralized and distributed fashion, requiring no overhead for relay selection and actuation, and resulting in opportunistically formed cooperative links that provide robust and reliable end-to-end communication, without the need for establishing a prior non-cooperative route, unlike existing schemes. The results demonstrate that under wireless channel impairments, such as fading and path loss, our cooperative forwarding framework and cross-layer architecture, RECOMAC significantly improve the system performance, in terms of throughput and delay, as compared to non-cooperative conventional layered network architecture with AODV routing over IEEE 802.11 MAC

Cross-layer optimizations in multi-hop ad hoc networks

Unlike traditional wireless networks, characterized by the presence of last-mile, static and reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by collections of mobile and static terminals that exchange data by enabling each other's communication. Supporting multi-hop communication in a MANET is a challenging research area because it requires cooperation between different protocol layers (MAC, routing, transport). In particular, MAC and routing protocols could be considered mutually cooperative protocol layers. When a route is established, the exposed and hidden terminal problems at MAC layer may decrease the end-to-end performance proportionally with the length of each route. Conversely, the contention at MAC layer may cause a routing protocol to respond by initiating new routes queries and routing table updates. Multi-hop communication may also benefit the presence of pseudo-centralized virtual infrastructures obtained by grouping nodes into clusters. Clustering structures may facilitate the spatial reuse of resources by increasing the system capacity: at the same time, the clustering hierarchy may be used to coordinate transmissions events inside the network and to support intra-cluster routing schemes. Again, MAC and clustering protocols could be considered mutually cooperative protocol layers: the clustering scheme could support MAC layer coordination among nodes, by shifting the distributed MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the system benefits of the clustering scheme could be emphasized by the pseudo-centralized MAC layer with the support for differentiated access priorities and controlled contention. In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering and routing protocols in MANETs. As main contribution, we study and analyze the integration of MAC and clustering schemes to support multi-hop communication in large-scale ad hoc networks. A novel clustering protocol, named Availability Clustering (AC), is defined under general nodes' heterogeneity assumptions in terms of connectivity, available energy and relative mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol, named Differentiated Distributed Coordination Function (DDCF), whose focus is to implement adaptive access differentiation based on the node roles, which have been assigned by the upper-layer's clustering scheme. We extensively simulate the proposed clustering scheme by showing its effectiveness in dominating the network dynamics, under some stressing mobility models and different mobility rates. Based on these results, we propose a possible application of the cross-layer MAC+Clustering scheme to support the fast propagation of alert messages in a vehicular environment. At the same time, we investigate the integration of MAC and routing protocols in large scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by extending the AOMDV protocol with a novel load-balancing approach to concurrently distribute the traffic among the multiple paths. We also study the composition effect of a IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF), used to reduce the effects of self-contention among frames at the MAC layer. The protocol framework is modelled and extensively simulated for a large set of metrics and scenarios. For both the schemes, the simulation results reveal the benefits of the cross-layer MAC+routing and MAC+clustering approaches over single-layer solutions

RECOMAC: a cross-layer cooperative network protocol for wireless ad hoc networks

A novel decentralized cross-layer multi-hop cooperative protocol, namely, Routing Enabled Cooperative Medium Access Control (RECOMAC) is proposed for wireless ad hoc networks. The protocol architecture makes use of cooperative forwarding methods, in which coded packets are forwarded via opportunistically formed cooperative sets within a region, as RECOMAC spans the physical, medium access control (MAC) and routing layers. Randomized coding is exploited at the physical layer to realize cooperative transmissions, and cooperative forwarding is implemented for routing functionality, which is submerged into the MAC layer, while the overhead for MAC and route set up is minimized. RECOMAC is shown to provide dramatic performance improvements of eight times higher throughput and one tenth of end-to-end delay than that of the conventional architecture in practical wireless mesh networks

A cross layer multi hop network architecture for wireless Ad Hoc networks

In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is presented. Our architecture involves the design of a simple yet efficient cooperative flooding scheme,two decentralized opportunistic cooperative forwarding mechanisms as well as the design of Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that spans and incorporates the physical, medium access control (MAC) and routing layers for improving the performance of multihop communication. The proposed architecture exploits randomized coding at the physical layer to realize cooperative diversity. Randomized coding alleviates relay selection and actuation mechanisms,and therefore reduces the coordination among the relays. The coded packets are forwarded via opportunistically formed cooperative sets within a region, without communication among the relays and without establishing a prior route. In our architecture, routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication while the messaging overhead to set up routes, select and actuate relays is minimized. RECOMAC is shown to provide dramatic performance improvements, such as eight times higher throughput and ten times lower end-to-end delay as well as reduced overhead, as compared to networks based on well-known IEEE 802.11 and Ad hoc On Demand Distance Vector (AODV) protocols

Green Cellular Networks: A Survey, Some Research Issues and Challenges

Energy efficiency in cellular networks is a growing concern for cellular operators to not only maintain profitability, but also to reduce the overall environment effects. This emerging trend of achieving energy efficiency in cellular networks is motivating the standardization authorities and network operators to continuously explore future technologies in order to bring improvements in the entire network infrastructure. In this article, we present a brief survey of methods to improve the power efficiency of cellular networks, explore some research issues and challenges and suggest some techniques to enable an energy efficient or "green" cellular network. Since base stations consume a maximum portion of the total energy used in a cellular system, we will first provide a comprehensive survey on techniques to obtain energy savings in base stations. Next, we discuss how heterogeneous network deployment based on micro, pico and femto-cells can be used to achieve this goal. Since cognitive radio and cooperative relaying are undisputed future technologies in this regard, we propose a research vision to make these technologies more energy efficient. Lastly, we explore some broader perspectives in realizing a "green" cellular network technologyComment: 16 pages, 5 figures, 2 table

A Cross-Layer Design Based on Geographic Information for Cooperative Wireless Networks

Most of geographic routing approaches in wireless ad hoc and sensor networks do not take into consideration the medium access control (MAC) and physical layers when designing a routing protocol. In this paper, we focus on a cross-layer framework design that exploits the synergies between network, MAC, and physical layers. In the proposed CoopGeo, we use a beaconless forwarding scheme where the next hop is selected through a contention process based on the geographic position of nodes. We optimize this Network-MAC layer interaction using a cooperative relaying technique with a relay selection scheme also based on geographic information in order to improve the system performance in terms of reliability.Comment: in 2010 IEEE 71st Vehicular Technology Conference, 201