Bilal R. Qazi

Analysis and Design of a MAC Protocol and Vehicular Traffic Simulator for Multimedia Communication on Motorways

This paper aims to guarantee the quality of service (QoS) to motorway drivers with regard to multimedia (triple play-video, voice, and data) communications, which requires substantial analysis of the characteristics of vehicular traffic profiles on motorways. We therefore perform an analysis of real vehicular traffic data taken from inductive loops on a motorway and then develop our own simulator to study real-time vehicular traffic scenarios on the medium access control (MAC) layer, where a wireless local area network (WLAN) base station (BS) is responsible for multimedia communication between vehicles and the backbone network. Access to this BS is managed by a modified version of the packet-reservation multiple access (M-PRMA) protocol, which we have integrated into the simulator. Finally, we use our developed simulator, which is built upon extensive analysis of vehicular traffic data, to evaluate the multimedia services offered to motorway drivers.

An energy efficient double cluster head routing scheme for motorway vehicular networks

We propose a novel double cluster-head routing scheme for motorway vehicular networks which is generically modelled (can be applied o single or multiple cluster-head routing schemes) to save a significant amount of energy through adaptive sleep cycles while maintaining he required quality of service (QoS). Real vehicular and data traffic measurements are utilised o evaluate the performance of he double cluster-head (DCH) scheme and compare with he existing (a single cluster-head (SCH)) scheme. The results, also verified with he simulations, reveal that the DCH scheme is able to achieve 2× lower packet blocking probability compared o he SCH scheme. Furthermore, on an average energy saving of 94% with service-tolerant delay during the whole day is achieved. In addition, we found ha with a lower market penetration ratio (MPR), which represents he near future vehicular communication rend, more than 4× energy is saved during peak hours in a motorway vehicular environment.

A Vacation-Based Performance Analysis of an Energy-Efficient Motorway Vehicular Communication System

Due to the unprecedented growth in bandwidth requirement, the increasing number of access points (APs) deployed within a macrocell for services such as video conferencing, video gaming, and data off-loading leads to significantly higher energy consumption. This advancement in mobile networks has forced researchers to explore various methods of energy saving, although with little emphasis on motorway vehicular networks where mobility is also an important aspect. Energy saving in these networks is extremely challenging due to the dynamic nature of the environment in which they operate. To analyze such a network, we first develop a performance model for a medium access control (MAC) protocol, namely, the modified version of packet reservation multiple access (M-PRMA) with wireless channel impairments in a motorway vehicular environment. The M-PRMA protocol provides communication links (time slots) between an AP and the vehicles in range. The time slots of the M-PRMA protocol are modeled as servers where each outage of the channel is represented as a server on queue-length-independent vacation. Then, each AP, in a hierarchical micro-macro topology, is modeled as a single-server queue where the AP takes queue-length-dependent vacations (switches to sleep mode) to save energy during its inactivity period, although at the expense of degraded quality of service (QoS). To address this, a number of sleep strategies for the AP are studied. Finally, both of these proposed models (M-PRMA with channel impairments and AP with sleep cycles) are analyzed and verified through simulations. The performance results reveal that the introduction of sleep strategies at an AP can save up to 80% transmission energy during off-peak hours and 66% on average during the day in a motorway vehicular environment while supporting end-to-end QoS for video and audio conferencing applications.

Data Dissemination with Drop Boxes

For data dissemination using vehicular ad hoc networks (VANETs), it is essential to determine the end-to-end (e2e) delay, the packet dropping probability (PDP), the number of vehicles required, and the size of the vehicles’ buffers needed to hold packets. In this paper, we study the impact of the above mentioned parameters and report original simulation results in a typical city scenario based on a 3x3 Manhattan grid. In addition, we also study the efficiency of our approach under varying degrees of market penetration of instrumented vehicles, hence establishing useful thresholds in realistic scenarios. Finally, by introducing different configurations of drop boxes, we show significant reduction in e2e delay and PDP.

Greening vehicular networks with standalone wind powered RSUs: A performance case study

The need for reducing the carbon footprint and reducing the operation expenditure (OPEX) in communication networks poses several challenges in the study, design and deployment of energy efficient networks in different environments. Recently there has been a considerable effort to green vehicular networks which is very challenging due to the very dynamic environment in which these networks operate. In this paper, we investigate the performance of the roadside units (RSUs) in a vehicular motorway network, and propose that these units are wind-powered and act as standalone entities. Real vehicular traffic profiles, reported data traffic measurements and reported wind measurements have been utilised to perform this study. We analyse the performance in several test cases and suggest an operational scenario. Both analytical and simulation results reveal that with the introduction of sleep cycles and a very small battery capacity (124 mAh), these RSUs are able to support quality of service (QoS) for video-related applications at each hour of the day in a motorway vehicular environment while increasing the energy efficiency by up to 32%.

Energy and QoS Evaluation for a V2R Network

In this paper we study the quality of service (QoS) and energy performance of the carrier sense multiple access with collision avoidance (CSMA/CA) based 802.11p scheme, and our previously proposed modified version of packet reservation multiple access (M- PRMA) scheme for a vehicle-to-roadside (V2R) network in a motorway environment. The simulation results illustrate the deficiency of the 802.11p protocol in providing adequate QoS to support real-time communication for varying vehicular traffic loads expected on the motorway. The significant amount of energy required for carrier sensing in the 802.11p is realised when compared to the low listening energy expenditure levels of the M-PRMA protocol. We compare both protocols under realistic (experimental) vehicular flow in a motorway and show that power saving up to 12 x can be achieved if a time division multiple access (TDMA) approach such as M-PRMA is used or if the CSMA/CA listening power is reduced.

Position Based Routing Protocol for a City Environment

Recently, Vehicular ad hoc networks (VANETs) have started receiving significant attention from both academia and industry. In order to support safety related applications in delay tolerant networks, the design of an efficient routing protocol for VANETs is extremely crucial. The main requirement for all routing protocols is to achieve minimum delay with minimum consumption of network resources. In this paper we propose a position-based routing algorithm namely position-based routing with Most Forward within Radius (PRMFR) which clearly enhances the performance of the system compared to flooding based routing protocols such as epidemic routing in terms of packet dropping probability and the total number of transmissions. Position based routing protocols are known to use the node’s geographical locations in order to initiate a route between the source and the destination. Moreover, we introduce a percentage of greedy nodes to both protocols, and study their impact on the performance. Furthermore, a 3x3 km Manhattan mobility model is presented to examine the performance of our scheme.

M-PRMA protocol for vehicular multimedia communication

Medium access control (MAC) protocols, responsible for sharing the channel among users, are receiving more attention especially in vehicular networks due to the highly dynamic nature of the environment in which they operate. Typically MAC protocols were designed for one traffic class such as voice, video or data as all of them have different characteristics. In this paper, we introduce a modified version of packet reservation multiple access namely M-PRMA MAC protocol for vehicular networks responsible for multimedia communication while maintaining quality of service (QoS) for each traffic class. We evaluate the performance of the MAC protocol in terms of packet dropping probability, average delay and throughput under a 3 × 3 km Manhattan grid representing a typical modern city.

Base stations locations optimisation in an airport environment using genetic algorithms

Traditionally the locations of the base stations (BSs) in an indoor environment are optimised based on either traffic demand, signal to noise ratio (SNR), energy consumption or coverage area. However, considering only one of these parameters does not yield an optimum design, which is needed for efficient cost-effective planning with the required quality of service (QoS). Moreover, this problem becomes extremely challenging in highly dynamic environments such as airports, shopping malls and train stations where both spatial and temporal traffic variations are considerably high. Due to the continuous growth in international air traffic and the dynamic behaviour of passengers in an airport environment, providing reliable and cost-effective communication facilities to passengers and staff becomes even more difficult at different times and locations. Using data from Heathrow Terminal 4 (T4), we, in this paper, develop T4 passenger flow models which take both the spatial and temporal variations into account and help us accurately determine the traffic demand (TD), coverage area and path loss and thus outage and energy consumption. Moreover, we propose a multi-objective genetic algorithm (GA) which serves traffic demand and minimises both outage and energy consumption of the whole network. This eventually minimises the number of BSs while optimising their locations. The results reveal that only a few (i.e. 1-4) more base stations are required when we consider all three parameters together compared to the TD only. However our proposed GA, considering TD, outage and energy consumption, achieves lower outage and consumes almost 90% less transmission energy compared to the case of TD only while serving the same amount of traffic in such a dynamic environment.

Load Adaptive Caching Points for a Content Distribution Network

The unprecedented growth in content demand on smartphones has significantly increased the energy consumption of current cellular and backbone networks. Apart from achieving stringent carbon footprint targets, provisioning high data rates to city vehicular users while maintaining quality of service (QoS) remains a serious challenge. In previous work, to support content delivery at high data rates, the number and locations of caching points (CPs) within a content distribution network (CDN) were optimized while reducing the operational energy consumption compared to typical cellular networks. Further reduction in energy consumption may be possible through sleep cycles, which reduces transmission energy consumption. However, sleep cycles degrade the quality of service. Therefore, in this paper, we propose a novel load adaptation technique for a CP which not only enhances content download rate but also reduces transmission energy consumption through random sleep cycles. Unlike a non-load adaptive (deterministic) CP, the performance results reveal that the load adaptive CP achieves considerably lower average piece delay (approximately 60% on average during the day), leveraging the introduction of random sleep cycles to save transmission energy. The proposed CP saves up to 84% transmission energy during off-peak hours and 33% during the whole day while fulfilling content demand in a city vehicular environment.