CMD: A Multi-Channel Coordination Scheme for Emergency Message Dissemination in IEEE 1609.4

In the IEEE 1609.4 legacy standard for multi-channel communications in vehicular ad hoc networks(VANETs), the control channel (CCH) is dedicated to broadcast safety messages while the service channels (SCH's) are dedicated to transmit infotainment service content. However, the SCH can be used as an alternative to transmit high priority safety messages in the event that they are invoked during the service channel interval (SCHI). This implies that there is a need to transmit safety messages across multiple available utilized channels to ensure that all vehicles receive the safety message. Transmission across multiple SCH's using the legacy IEEE 1609.4 requires multiple channel switching and therefore introduces further end-to-end delays. Given that safety messaging is a life critical application, it is important that optimal end-to-end delay performance is derived in multi-channel VANET scenarios to ensure reliable safety message dissemination. To tackle this challenge, three primary contributions are in this article: first, a channel coordinator selection approach based on the least average separation distance (LAD) to the vehicles that expect to tune to other SCH's and operates during the control channel interval (CCHI) is proposed. Second, a model to determine the optimal time intervals in which CMD operates during the CCHI is proposed. Third, a contention back-off mechanism for safety message transmission during the SCHI is proposed. Computer simulations and mathematical analysis show that CMD performs better than the legacy IEEE 1609.4 and a selected state-of-the-art multi-channel message dissemination schemes in terms of end-to-end delay and packet reception ratio.Comment: 15 pages, 10 figures, 7 table

Efficient medium access control protocol for vehicular ad-hoc networks

Intelligent transportation systems (ITS) have enjoyed a tremendous growth in the last decade and the advancement in communication technologies has played a big role behind the success of ITS. Inter-vehicle communication (IVC) is a critical requirement for ITS and due to the nature of communication, vehicular ad-hoc network technology (VANET) is the most suitable communication technology for inter-vehicle communications. In Practice, however, VANET poses some extreme challenges including dropping out of connections as the moving vehicle moves out of the coverage range, joining of new nodes moving at high speeds, dynamic change in topology and connectivity, time variability of signal strength, throughput and time delay. One of the most challenging issues facing vehicular networks lies in the design of efficient resource management schemes, due to the mobile nature of nodes, delay constraints for safety applications and interference. The main application of VANET in ITS lies in the exchange of safety messages between nodes. Moreover, as the wireless access in vehicular environment (WAVE) moves closer to reality, management of these networks is of increasing concern for ITS designers and other stakeholder groups. As such, management of resources plays a significant role in VANET and ITS. For resource management in VANET, a medium access control protocol is used, which makes sure that limited resources are distributed efficiently. In this thesis, an efficient Multichannel Cognitive MAC (MCM) is developed, which assesses the quality of channel prior to transmission. MCM employs dynamic channel allocation and negotiation algorithms to achieve a significant improvement in channel utilisation, system reliability, and delay constraints while simultaneously addressing Quality of Service. Moreover, modified access priority parameters and safety message acknowledgments will be used to improve the reliability of safety messages. The proposed protocols are implemented using network simulation tools. Extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANET technologies. Finally, improvements in delay and packet delivery ratios are presented

Evaluation study of IEEE 1609.4 performance for safety and non-safety messages dissemination

The IEEE 1609.4 was developed to support multi-channel operation and channel switching procedure in order to provide both safety and non-safety vehicular applications. However, this protocol has some drawback because it does not make efficient usage of channel bandwidth resources for single radio WAVE devices and suffer from high bounded delay and lost packet especially for large-scale networks in terms of the number of active nodes. This paper evaluates IEEE 1609.4 multi-channel protocol performance for safety and non-safety application and compare it with the IEEE 802.11p single channel protocol. Multi-channel and single channel protocols are analyzed in different environments to investigate their performance. By relying on a realistic dataset and using OMNeT++ simulation tool as network simulator, SUMO as traffic simulator and coupling them by employing Veins framework. Performance evaluation results show that the delay of single channel protocol IEEE 802.11p has been degraded 36% compared with multi-channel protocol

TDMA Slot Reservation in Cluster-Based VANETs

Vehicular Ad Hoc Networks (VANETs) are a form of Mobile Ad Hoc Networks (MANETs) in which vehicles on the road form the nodes of the network. VANETs provide several services to enhance the safety and comfort of drivers and passengers. These services can be obtained by the wireless exchange of information among the vehicles driving on the road. In particular, the transmission of two different types of messages, safety/update and non-safety messages. The transmission of safety/update message aims to inform the nearby vehicles about the sender\u27s current status and/or a detected dangerous situation. This type of transmission is designed to help in accident and danger avoidance. Moreover, it requires high message generated rate and high reliability. On the other hand, the transmission of non-safety message aims to increase the comfort on vehicles by supporting several non-safety services, from notifications of traffic conditions to file sharing. Unfortunately, the transmission of non-safety message has less priority than safety messages, which may cause shutting down the comfort services. The goal of this dissertation is to design a MAC protocol in order to provide the ability of the transmission of non-safety message with little impact on the reliability of transmitting safety message even if the traffic and communication densities are high. VANET is a highly dynamic network. With lack of specialized hardware for infrastructure and the mobility to support network stability and channel utilization, acluster-based MAC protocol is needed to solve these overcomes. This dissertation makes the following contributions: 1. A multi-channel cluster-based TDMA MAC protocol to coordinate intracluster communications (TC-MAC) 2. A CH election and cluster formation algorithm based on the traffic flow and a cluster maintenance algorithm that benefits from our cluster formation algorithm 3. A multi-channel cluster-based CDNIA/TDMA hybrid MAC protocol to coordinate inter-cluster communications I will show that TC-MAC provides better performance than the current WAVE standard in terms of safety/update message reliability and non-safety message delivery. Additionally, I will show that my clustering and cluster maintenance protocol provides more stable clusters, which will reduce the overhead of clusterhead election and re-clustering and leads to an efficient hierarchical network topology

Analysis of VANET Standard IEEE 1609.4 Mac Layer Multi-Channel Operations Using OMNeT++ and Veins

VANETS is an ad hoc network in vehicles with wireless communication capability. The network utilizes a system to relay data from one vehicle to another vehicle or to a Road Side Unit (RSU). This communication is also known as Vehicle to Vehicle (V2V) [31] and Vehicle to Infrastructure (V2I) [31]. The communication protocol for Wireless Access in Vehicular Environment (WAVE) [10], is the industry standard IEEE 802.11p to communicate between vehicles. This thesis examines the Medium Access Control (MAC) layer of this IEEE 1609.4 multi-channel communication protocol. In Dedicated Short Range Communications, the core of the WAVE protocol, there is an allocated spectrum in the frequency area of 5.9-GHz [20]. In the U.S, the allocated spectrum of 75 MHz was split into seven channels. A channel is defined as a frequency range of 10 MHz for a radio to tune into [28]. There is a control channel to relay safety messages and six service channels to relay non-safety messages, giving us two types of channels to choose from when in message transmission. Both the type and priority of the message are the factors considered. Many existing studies illustrate the impact of multi- channel and single-channel switching for non-safety and safety message transmissions. Most studies focus on optimizing the usability of the service channels. This thesis aims to determine the best use of the single radio in a vehicle i.e. to best utilize the Control Channel (CCH) and Service Channels (SCHs) in a Single Radio Multi-Channel (SR-MC) system [20]. We analyze the channel utilization, beacon transmission, and packet transmission of IEEE 1609.4 multi-channel operations in CCH and SCH. Some of the parameters used for comparison are the number of collisions, channel utilization, packet transmissions, and beacon transmissions. We investigate the scenario with density of n vehicles in a real world map, using safety (beacons) and non-safety (data) messages. The technologies used are Instant Veins 4.6, OMNET++ 5.2.1, SUMO 0.30, Debian GNU/Linux 9 (stretch) 64-bit, VMware Fusion (Professional Version 10.1.4) and an open street map from Northampton. The advantage of using OMNeT++ and Simulation Urban Mobility (SUMO) framework is the thorough implementation of IEEE 1609.4 DSRC/ WAVE and IEEE 802.11p in the framework [29]. Additionally, important feature of realistic traffic along with factual map can be generated with SUMO [21]. The contributions provided in this thesis include the integration of the testing framework Catch, randomizing the SCH, adding beacon transmission to the MAC layer, tracking of vehicle neighbors, tracking of collisions, and channel utilization. Plus an analysis on multi-channel switching. In our results we found that the CCH is highly overloaded both with beacon and channel switching management, which has a strong impact on the switching operation with a high number of collisions. Furthermore we also found that as the number of beacons generated increased, there was an increase in lost frames independent of the channel . Lastly there was little fluctuation in the number of collisions with a higher “n” of vehicles

Effect of pressure on density, porosity and flexural strength during cold isostatic press of alumina-ysz chromia cutting too

This study presented the effect of pressure on the density, porosity and flexural strength when cold isostatic press (CIP) was applied to compact the ceramic powders in the form of insert cutting tools. Specific composition of alumina (Al2O3) wt.90%,yittria stabilized zirconia (YSZ) wt.10%, chromium oxide(Cr2O3) wt.0.6% and polyethylene glycol (PEG) wt.0.6% were ball milled and hand pressed to form green body of ceramic inserts. These green body were undergone further compaction inside CIP with pressures variation of 200 MPa, 300 MPa, 400 MPa with 30 seconds and 60 seconds pressuring time. The ceramic composts were then sintered at 1440°C for 9 hours before being assessed with density, porosity, Rockwell hardness (HRC) and bending test. The results show that CIP use with 300 MPa parameters with 60 seconds shows the best mechanical properties with relative density 95.5%, porosity 4.5% and HRC 65.5 hardness. Further assessment of microstructure revealed that the particles size distributed evenly along fracture surface with coarse grain and porosity dominant in the certain area

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