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

Fuzzy based Channel Selection for Location Oriented Services in Multichannel VCPS Environments

Location-oriented services in Vehicular Cyber-Physical System (VCPS) have witnessed significant attention due to their potentiality to address traffic safety and efficiency related issues. The multichannel communication aids these services by tuning their overall performance in vehicular environments. Related literature on multichannel communication is focuses on interference as channel quality measure. However, uncertain mobility and density of vehicles significantly affect channel quality apart from interference. The static quantification of channel quality is not suitable due to the dynamic characteristics of the channel quality parameters. In this context, this paper proposes Fuzzy-based Channel Selection framework for location-oriented services in Multichannel VCPS environments (F-CSMV). A system model is presented for deriving channel access delay using Markov chain model. The channel quality is estimated using channel access delay (CAD) and signal-to-interference ratio (SIR). The fuzzy logic based channel selection framework is developed considering fuzzification and defuzzification of CAD and SIR. The comparative performance evaluation attests the benefit of the framework as compared to the state-of-the-art techniques in VCPS

Link-Layer Cooperative Communication in Vehicular Networks

Vehicular ad hoc networks (VANETs) are a special kind of communication networks and possess unique characteristics as compared with general mobile ad hoc networks (MANETs), where vehicles communicate with each other or with stationary road side units. Hence, directly applying the existing communication protocols designed for MANETs may not be reliable and efficient in VANETs. Thus, this thesis presents link-layer cooperative frameworks to improve transmission reliability and network throughput over distributed TDMA MAC protocols for VANETs. We present a link-layer node cooperation scheme for VANETs, referred to as Cooperative ADHOC MAC (CAH-MAC). In CAH-MAC, neighboring nodes cooperate to utilize unused time slots to retransmit failed packets. Throughput improvement is achieved by using idle time slots that are wasted in the absence of node cooperation. In addition, as a packet is retransmitted earlier by a relay node, transmission delay and packet dropping rate are reduced. We study the effects of a dynamic networking environment on the performance of CAH-MAC. It is observed that, system performance degrades due to cooperation collisions. To tackle this challenge, we present an enhanced CAH-MAC (eCAH-MAC) scheme. In eCAH-MAC, using different types of packet and by delaying or suspending some relay transmissions, cooperation collisions can be avoided and cooperation opportunities can be efficiently utilize without disrupting the normal operations of the distributed TDMA MAC. We propose a node cooperation based makeup strategy for vehicular networks, referred to as cooperative relay broadcasting (CRB), such that neighboring nodes proactively rebroadcast the packet from a source node. An optimization framework is developed to provide an upper bound on the CRB performance with accurate channel information. Further, we propose a channel prediction scheme based on a two-state first-order Markov chain, to select the best relaying node for CRB. As packets are repeatedly broadcasted by the neighboring nodes before they expire, the proposed CRB framework provides a more reliable broadcast service as compared with existing approaches. The proposed node cooperation frameworks enhance the performance of distributed TDMA MAC and make it more robust to tackle VANET's dynamic networking conditions