Service Channel Interval Research Articles

Adaptive and Optimized Control Channel Utilization in Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) are counted as a state-of-art technology which can be considered to provide reliable communication which is increase the safety and convenience of drivers in the road. Due to channel congestion occurrence in both highway and urban scenario, many VANET’s safety applications face degradation in their quality of service especially in a high-density environment. To improve the performance, reliability, and safety of VANETs, message overhead on the standard wireless channel dedicated short-range communications (DSRC) should be alleviated to guarantee safety-related applications. To this end, this paper proposes an approach to optimize the utilization of the control channel (CCH) and make the control channel interval (CCHI) adaptive to the emergency cases in the vehicular scenarios. More precisely, when there is an emergency cases, a part of service channel interval (SCHI) is exploited to ensure the guarantee of emergency message delivery. When a vehicle intended to transmit the safety message to the surround vehicles, the proposed method granted that CCH is allocated to meet the traffic safety demands; then, the safety messages disseminate properly to the transmission range. A part of the service channel interval (SCHI) is exploited to ensure the guarantee of emergency message delivery, Then, applying the laying chicken algorithm (LCA) to solve the derived CCH optimized utilization. Finally, extensive simulations are carried out to validate the proposed optimized CCH utilization. To validate the performance of the proposed adaptive congestion control approach (ACCA), we used the network simulator Ns-3 [35] to simulate the vehicle’s environment, after generating vehicles’ mobility traces of the nodes using the network simulator for urban mobility (SUMO) with OpenStreetMap (OSM). The simulation indicates that our congestion algorithm (ACCA) performs better service quality than other existing algorithms. We got a better network connection regarding safety messages, beacon rate with time, and packet length for different vehicles’ densities.

A flexible and adaptive medium access control protocol for improving quality of service in vehicular ad-hoc networks

Designing MAC (Medium Access Control) protocols for VANETs is a difficult task due to the inherently unstable nature of these networks when compared to traditional ad hoc networks (high node speed, position changes that lead to disconnections, signal losses, etc.). In recent years, several standardization efforts have been made by the IEEE in association with the scientific community in this area and they proposed the 1609.4 MAC protocol in the IEEE WAVE (Wireless Access in Vehicular Environments) stack. The aim of our work is to improve the quality of service and overall performances of this 1609.4 MAC protocol by proposing three mechanisms. First, we introduce an equity algorithm that aims to ensure more fairness between nodes. We also adapt the SCH (Service CHannel) interval to the network's needs with a dynamic SCH interval mechanism. Finally, we propose an emergency mechanism that aims to ensure the transmission of critical safety packets when dangerous events occur on the road. The results of our simulations show a significant improvement of the protocol's performances in terms of throughput, packet loss and critical packet delivery rates under several scenarios.

Information-Priority-Oriented Adaptive MAC Protocol for High Dynamic UAV Network

In recent years, unmanned aerial vehicles (UAVs) have attracted wide attention in both military and civilian fields because of their versatility, flexibility, and low-cost characteristics. In this letter, a UAV network architecture oriented to the virtual cloud processing center (VCPC) is considered, where the highly dynamic UAV network can transmit real-time data from sensors on the ground as well as data observed by the UAV nodes to the VCPC. Due to the high dynamic characteristics of UAVs, the topology of networks and traffic load within the coverage of the VCPC change frequently, especially when the priority of the information is different, and it is necessary to design a novel media access control (MAC) protocol to reduce the transmission delay of high priority and improve throughput of UAV networks. Therefore, an information priority oriented adaptive (IPOA-MAC) protocol is presented in this letter for high dynamic UAV networks. The relative length of control channel interval and service channel interval can be adaptively adjusted to improve network throughput in high dynamic application scenarios. Also, priority flag bits are set in data to ensure real-time transmission of high-priority information. Finally, the simulation results show the proposed IPOA-MAC can improve network performance effectively than other existing protocols.

An intelligent scheme for slot reservation in vehicular ad hoc networks

Vehicular ad hoc network is a solution for increasing road traffic demand. Non-safety messages are sent during the service channel interval. The slots during which the messages are sent are not decided prior to the transmission. If the reservation of slots is done during the control channel interval, then the non-safety messages can be transmitted without any collision and thus the network performance can be improved. Further, to improve the network performance, the safety packets can be scheduled in the queue according to the time remaining for which sender and receiver are in the range of each other. This work proposes and evaluates the performance of safety message scheduling and infotainment message reservation through a MAC protocol SSIR-MAC to ensure network stability by transmitting beacons without any collision. The safety messages are queued according to their deadline and the slots for the transmission of non-safety packets are reserved during the control channel itself. Further, a hybrid queue is proposed to decrease the delay of enqueue and dequeue operations. Evaluation through extensive simulation results demonstrates the strength of SSIR-MAC. Comparisons are made with IEEE 802.11p standard and with two existing protocols which are relevant to the proposed work.

An Adaptive Channel Division MAC Protocol for High Dynamic UAV Networks

Nowadays, unmanned aerial vehicle (UAV) has captured great attentions for its versatility, flexibility, and low-cost. In this paper, we consider a high altitude platform (HAP) assisted UAV network towards Internet of Things (IoT), where high dynamic UAVs can transmit real-time IoT data to remote ground control center via the HAP. Because of the movement characteristic of UAVs, the number of UAVs within the HAP coverage and the traffic load change frequently, which poses new challenges for the Media Access Control (MAC) protocol in this network. To make full use of the channel resources and guarantee the communication performance of multiple UAVs, we firstly propose an adaptive channel division MAC (ACD-MAC) protocol for this high dynamic UAV network, where the relative length of control channel interval to service channel interval, denoted by channel allocation parameter, can be flexibly adjusted according to the number of UAVs and traffic load. Then, based on a Markov model, we give an algorithm to calculate the optimal channel allocation parameter in the proposed ACD-MAC protocol. Finally, simulation results show that the proposed ACD-MAC protocol can achieve a lower end-to-end delay and a higher throughput performance in such a high dynamic UAV network than the traditional fixed channel division MAC protocol.

Joint Optimization of Message Transmissions With Adaptive Selection of CCH Interval in VANETs

In vehicular networks, the safety-related messages (emergency and periodic messages) and non-safety message (RFS: request for service message) should share the scarce wireless resource. Emergency messages deliver time-critical information with guaranteed reliability, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g.</i> road-safety information, whereas periodic ones convey normal status update information, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g.</i> vehicular positions, show that is less time- and loss-critical. The RFS message is used for reserving Internet data service through the infrastructure on the road. In the channel access for vehicles, the synchronization interval (SI) is repeated every 100 ms and each SI is divided by one control channel interval (CCHI) for the transmission of safety-related messages and RFS message and by one service channel interval (SCHI) for the Internet service from the roadside infrastructure. It is crucial to set the length of CCHI appropriately in the SI because of the dynamic environment of VANETs. In this paper, we consider two optimization problems of message transmissions depending on whether the length of CCHI is flexible or not: 1) a fixed CCHI (non-adaptive) and 2) a variable CCHI (adaptive), respectively, and obtain the optimal MAC parameters where we adopt the IEEE 802.11e enhanced distributed channel access (EDCA) protocol with a “strict” priority for the emergency message. Finally, we conduct extensive simulations to validate our analytical findings.

A Priority-Based Multichannel Mac to Support the Non-Safety Applications in SCH Interval at RSU in V2I Communication

Abstract The transmission of safety applications in VANET is clearly the top concern. However, the non-safety applications, which improve the quality of experience, as well as the efficiency of the traffic, also need to be paid more attention. In VANET, the safety applications are transmitted in control channel interval and the non-safety applications can be transmitted only in service channel interval. In this paper, we propose a priority-based multichannel MAC to support the non-safety applications in service channel interval in Vehicle-to-Infrastructure communication with the presence of roadside unit. The novel MAC also allocates service channel according to the priority and divides the vehicles, which have the same required service channel, into four priority groups to enhance the EDCA mechanism. We use the mathematical model and the simulation for evaluating the performance under the influence of velocity with a different number of vehicles in the network.

CMD: A Multichannel Coordination Scheme for Emergency Message Dissemination in IEEE 1609.4

The IEEE 1609.4 legacy standard for multichannel communications in vehicular ad hoc networks (VANETs), specifies that the control channel (CCH) is dedicated to broadcast safety messages, while the service channels (SCHs) are dedicated to transmit infotainment service content. However, the SCHs 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 SCHs 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 multichannel VANET scenarios to ensure reliable safety message dissemination. To tackle this challenge, three primary contributions are in this article: first, a cooperative multichannel coordinator (CMD) selection approach based on the least average separation distance (LAD) to the vehicles that expect to tune to other SCHs 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 multichannel message dissemination scheme in terms of end-to-end delay and packet reception ratio.

MAC protocols with dynamic interval schemes for VANETs

Under the dynamically changing topology of Vehicular Ad-hoc NETworks (VANETs), the restricted intervals in Medium Access Control (MAC) protocols cannot provide sufficient capacity to carry both safety and non-safety applications. One approach which can solve these issues is a dynamic MAC protocol that can adapt itself to the vehicle density or traffic conditions. In this survey, we, therefore, study various techniques for dynamic intervals used in MAC protocols, their advantages, and disadvantages. First, we classify these protocols into three following categories: 1) contention-based, 2) contention-free, and 3) a hybrid between contention-free and contention-based medium access methods. Second, in each medium access method, we classify the methodologies depending on their operating principles. The conclusions of our study are as follows: 1) Adaptive MAC protocols improve the channel utilization and adapt themselves to various traffic states, 2) Adaptive MAC protocols perform better than protocols using fixed intervals, 3) Currently, MAC protocols using dynamic intervals, which are suitable to VANET standards, are only applicable to optimize control channel interval; therefore, it is necessary to expand to both optimize control channel interval and service channel interval according to network and traffic condition. Finally, we discuss some open issues and whether designing MAC protocols using dynamic intervals can meet the QoS requirements for different applications in the future.

Adaptive multichannel MAC protocol based on SD‐TDMA mechanism for the vehicular ad hoc network

In this study, the design of an adaptive medium access control (MAC) protocol based on the space-division–time-division multiple access (SD-TDMA) mechanism is presented to improve the utilisation and fairness of the time-slot allocation scheme in the vehicular ad hoc network. The SD-TDMA mechanism dynamically allocates time-slots owing to a dynamic topology. This protocol reduces transmission collisions through user detection procedures. Most users can thus access the service channel (SCH) without conflict and acquire time slots according to the mapping between geographic locations and time slots. Users failing to access the channel in user detection procedures can send request access packets in security channels to again participate in SCH time-slot allocation during the SCH interval. Simulations are conducted to evaluate the performance of the proposed method in urban scenarios. The SD-TDMA mechanism is compared with an SDMA-based MAC protocol, the IEEE 802.11p distributed coordination function and an MAC protocol based on transmission sequences. Owing to the decreased rate of transmission collisions and the dynamic time-slot allocation scheme, it is shown that the SD-TDMA mechanism provides a significantly higher utilisation of time slots and better fairness of data transmission than existing approaches.

Triggered CCHI Multichannel MAC protocol for Vehicular Ad Hoc Networks

This paper proposes a Triggered CCHI Multichannel MAC protocol for efficient safety message dissemination in Vehicular Ad Hoc Networks. The proposed protocol allows a vehicle to start control channel interval (CCHI) by terminating service channel interval (SCHI) whenever a safety message arrives during SCHI. It enhances the performance of VANET by reducing resource wastage and unwanted delay caused by fixed interval of CCHI and SCHI. Further, CCHI keeps on increasing until all safety messages are not transmitted. A virtual TDMA beaconing process is also proposed in this paper to ensure delivery of periodic status messages. Multichannel hidden terminal problem is also addressed using cluster member request and cluster head request. An analytical model is developed to evaluate the proposed protocol with respect to packet delivery ratio, throughput, safety message delay and packet loss ratio. Extensive simulation is carried out to validate the analytical model and to demonstrate the improvement in comparison to existing similar MAC protocols and IEEE802.11p.

Performance Analysis of the IEEE 802.11p Multichannel MAC Protocol in Vehicular Ad Hoc Networks.

Vehicular Ad Hoc Networks (VANETs) employ multichannel to provide a variety of safety and non-safety applications, based on the IEEE 802.11p and IEEE 1609.4 protocols. The safety applications require timely and reliable transmissions, while the non-safety applications require efficient and high throughput. In the IEEE 1609.4 protocol, operating interval is divided into alternating Control Channel (CCH) interval and Service Channel (SCH) interval with an identical length. During the CCH interval, nodes transmit safety-related messages and control messages, and Enhanced Distributed Channel Access (EDCA) mechanism is employed to allow four Access Categories (ACs) within a station with different priorities according to their criticality for the vehicle’s safety. During the SCH interval, the non-safety massages are transmitted. An analytical model is proposed in this paper to evaluate performance, reliability and efficiency of the IEEE 802.11p and IEEE 1609.4 protocols. The proposed model improves the existing work by taking serval aspects and the character of multichannel switching into design consideration. Extensive performance evaluations based on analysis and simulation help to validate the accuracy of the proposed model and analyze the capabilities and limitations of the IEEE 802.11p and IEEE 1609.4 protocols, and enhancement suggestions are given.

Efficient Channel Management Mechanism to Enhance Channel Utilization for Sensing Data Delivery in Vehicular Ad Hoc Networks

IEEE 1609.4 defines MAC layer implementation in a vehicular ad hoc network (VANET). In IEEE 1609.4 multichannel operation, the control channel interval (CCHI) and the service channel interval (SCHI) are defined such that service channels cannot be utilized during the CCHI, and vice versa, which leads to poor utilization of scarce spectrum resources. In this paper, we propose a multi-schedule-based channel switching mechanism to improve channel utilization and uniformly distribute channel load. In our proposed mechanism, four schedules are defined to switch between the control channel and service channels. Therefore, service channels can be utilized during the CCHI, and the control channel can be utilized during the SCHI. Moreover, control channel load is distributed throughout the whole sync interval. We compared our proposed MAC protocol with IEEE802.11p for wireless access in the vehicular environment using the OMNET++ 4.5 network simulator. In the simulation results, we determined that utilization of the service channel increased and contention on the control channel was reduced, compared with the legacy standard, especially in slow motion and high-density VANETs.

Performance Analysis of Connectivity Probability and Connectivity-Aware MAC Protocol Design for Platoon-Based VANETs

Vehicular ad hoc networks (VANETs) can provide safety and nonsafety applications to improve passenger safety and comfort. Grouping vehicles into platoons in VANETs can improve road safety and reduce fuel consumption. It is critical to design an efficient medium access control (MAC) protocol for platoon-based VANETs. Moreover, because of the space and time dynamics of moving vehicles, network connectivity is an important performance metric to indicate the quality of the network communications and the satisfaction of users. Unfortunately, network connectivity is often ignored in the design of existing MAC protocols for VANETs. In this paper, we study the connectivity characteristics and present a connectivity-aware MAC protocol for platoon-based VANETs. The connectivity probabilities are analyzed for vehicle-to-vehicle and vehicle-to-infrastructure communication scenarios in one- and two-way VANETs, respectively. A multipriority Markov model is presented to derive the relationship between connectivity probability and system throughput. Based on variable traffic status and network connectivity, a multichannel reservation scheme is adopted to dynamically adjust the length of the control channel interval and the service channel interval for the improvement of the system throughput. Analysis and simulation results show that the throughput increases with connectivity probability. However, with a further increase in connectivity probability, the throughput will decrease due to numerous channel contentions.

An Efficient and Reliable MAC in VANETs

Vehicular Ad hoc Network (VANET) is developed to enhance the safety, comfort and efficiency of driving. The IEEE 802.11p/WAVE and IEEE 1609.4 family are standards intended to support wireless access in VANETs. In this paper, we propose an Efficient and Reliable MAC protocol for VANETs (VER-MAC) which allows nodes to broadcast safety packets twice during both the control channel interval and service channel interval to increase the safety broadcast reliability. By using the additional data structures, nodes can transmit service packets during the control channel interval to improve the service throughput.

A Scalable CSMA and Self-Organizing TDMA MAC for IEEE 802.11 p/1609.x in VANETs

vehicular ad hoc networks (VANETs) have been a key topic for research community and industry alike. The wireless access in vehicular environment standard employs the IEEE 802.11p/1609.4 for the Medium Access Control (MAC) layer implementation for VANETs. However, the carrier sense multiple access (CSMA) based mechanism cannot provide reliable broadcast services, and the multi-channel operation defined in IEEE 1609.4 divides the available access time into fixed alternating control channel intervals (CCH) and service channel (SCH) intervals, which may lead to the low utilization of the scarce resources. In this paper, a novel multichannel MAC protocol called CS-TDMA considering the channel access scheduling and channel switching concurrently is proposed. The protocol combines CSMA with the time division multiple access (TDMA) to improve the broadcast performance in VANETs. Meanwhile, the dwelling ratio between CCH and SCH changes dynamically according to the traffic density, resulting in the improvement of resource utilization efficiency. Simulation results are presented to verify the effectiveness of our mechanism and comparisons are made with three existing MAC protocols, IEEE MAC, SOFT MAC and VeMAC. The simulation results demonstrate the superiority of CS-TDMA in the reduction of transmission delay and packet collision rate and improvement of network throughput.