Multi-channel Medium Access Control Schemes Research Articles

Optimized data transmission scheme based on proper channel coordination used in vehicular ad hoc networks

In recent years, standardization bodies, academia and automobile manufacturers are working together to develop vehicular ad hoc network (VANET) based communication technologies. VANETs apply various channels like service channels (SCHs) and control channel (CCH) for supplying unbarred street safety facilities and the better condolence as well as effectiveness of driving. In this paper, we suggests a VCI known as variable control CH interval (VCI) MAC (multichannel medium access control) scheme which reduces safety message transmission time and helps to minimize collision probability when the vehicle node increases in the road by using k-means and donkey-smuggler optimization algorithm. The donkey-smuggler algorithm used to find the shortest path among the nodes and k-means clustering algorithm is used to group the sensor nodes. The distance ratio connecting with SCHs and CCHs can be effectively modified in MAC scheme. To improve the intermissions based on traffic situation, a model is carried out called Markov model and this process is called as stochastic process. Conceptual analysis and the simulation resulted to the recommended scheme which is capable to assist IEEE 1609.4 and IEEE 802.11p protocol. While retaining the methodized channelling of condemnatory safety data on control CH, the MAC scheme consequentially improves the higher saturated throughput and gives effective channel utilization of service CHs and minimizes transmission interval of service packets.

An optimized multichannel MAC scheme with dynamic control channel interval in dense VANET

To deliver emergency messages to notify other road users of dangerous events quickly, an Intelligent Transportation System (ITS) is required. Vehicular Ad-Hoc Networks (VANETs) is one of the solution to develop ITS. However, VANETs have various challenges to disseminate safety messages. VANETs apply multichannel medium access control scheme according to the IEEE 1609.4 standard draft. According to the standard draft multichannel medium access control scheme, channels are split into service channels (SCHs) and control channel (CCHs). This work proposes a dynamic control channel interval (DCI) MAC scheme that can variably fix the time interval efficiency percentage between SCHs and CCH. This work divides the SCHs interval time into small interval time slots according to the current network traffic load.

A Novel Coordinated Medium Access Control Scheme for Vehicular Ad Hoc Networks in Multichannel Environment

Vehicular ad-hoc networks (VANETs) aim to provide efficient safety and infotainment services. Wireless Access in Vehicular Environments (WAVE), which is a standard designed specifically for VANETs, stipulates seven 10-MHz channels: one control channel (CCH) for safety message transmission and six service channels (SCHs) for service message transmission. However, providing reliable broadcasting of safety messages on the CCH and efficient coordination of vehicles for service message transmission across the multiple SCHs in highly dynamic VANET environment is a nontrivial problem. In this paper, we propose a coordinated, adaptive, and reliable multichannel medium-access control scheme for the VANETs (VCAR-MAC). In VCAR-MAC, a novel time-division multiple access (TDMA)-based scheme that considers real-world environmental conditions is proposed to identify every vehicle quickly so that a time slot on the CCH can be allocated efficiently for reliable safety message transmission. On the SCHs, VCAR-MAC provides a multi-SCH coordination scheme, which adaptively adjusts the SCH reservation period in order to fully utilize the channel bandwidth. Furthermore, a dynamic contention window (CW) mechanism is proposed, in which the initial CW size is adaptively optimized to maximize the number of successful SCH reservations, thereby maximizing the service message throughput. It has been proven via the mathematical analysis and simulation experiment that VCAR-MAC can significantly improve throughput and reduce delay for both safety and service messages.

MC-MAC: a multi-channel based MAC scheme for interference mitigation in WBANs

Wireless body area networks (WBANs) support the inter-operability of biomedical sensors and medical institutions with convenience and high-efficiency, which makes it an appropriate solution for the pervasive healthcare. Typically, WBANs comprise in-body or around-body sensor nodes for collecting data of physiological feature. Therefore, the efficient medium access control (MAC) protocol is a crucial paramount to coordinate these devices and forward data to the medical center in an efficient and reliable way. However, the extensive use of wireless channel and coexistence of WBANs may result in inevitable interference which will cause performance degradation. Besides, contention-based access in single channel in WBANs is less efficient for dense medical traffic on account of large packet delay, energy consumption and low priority starvation. To address these issues above, we propose a multi-channel MAC (MC-MAC) scheme to obtain better network performance. Considering the characteristic and emergency degree of medical traffic, we introduce a novel channel mapping and selection mechanism, cooperating with conflict avoidance strategy, to organize nodes to access available channels without collisions. In addition, we have evaluated the performance of MC-MAC and the standard IEEE 802.15.6 via simulation and hardware test. The test is conducted by hardware platform based on prototype system of WBANs. Both of the analysis and simulation results show that MC-MAC outperforms the IEEE 802.15.6 in terms of packet delay, throughput, packet error rate and frame error rate.

A bandwidth-efficient and fair CSMA/TDMA based multichannel MAC scheme for V2V communications

Designing QoS-aware medium access control (MAC) scheme is a challenging issue in vehicular ad hoc networks. Proportional fairness and bandwidth utilization are among the significant requirements that should be taken into account by a MAC scheme. In this paper, a bandwidth-efficient and fair multichannel MAC protocol is proposed to address these two requirements, specifically in vehicle-to-vehicle communications. The proposed scheme is based on clustering of vehicles and exploits time division multiple access (TDMA) method alongside the carrier sense multiple access with collision avoidance mechanism to allocate DSRC-based resources in a different manner from IEEE 802.11p/IEEE 1609.4 protocols. It divides each channel into aligned dynamic-sized time frames. In each time frame, in a fully TDMA-based period, transmission opportunities are assigned to vehicles letting them have dedicated transmissions on the service and control channels. The maximum number of transmission opportunities per each frame is determined by the cluster head (CH) based on a defined optimization problem which aims at maximizing both proportional fairness and bandwidth utilization. Furthermore, the bandwidth utilization is assumed to be enhanced more through reallocation of unused transmission opportunities in each time frame, using a proposed reallocation algorithm. The proposed MAC protocol is treated as a lightweight scheme such that various types of unicast, multicast and broadcast communications are possible within the cluster without involving the CH. Evaluation results show that the proposed scheme has more than 90 % achievement in terms of proportional fairness and bandwidth utilization simultaneously, and in this case, has a considerable superiority over TC-MAC. In addition, using the proposed scheme, the satisfaction level of vehicles is preserved appropriately.

An RSU-Coordinated Synchronous Multi-Channel MAC Scheme for Vehicular Ad Hoc Networks

This paper proposes a roadside unit (RSU)-coordinated synchronous multi-channel medium access control (MAC) scheme for vehicular ad hoc networks (VANETs). The proposed scheme allows the on board unit (OBU) to reserve service channels (SCHs) on the control channel (CCH) during almost the whole synchronous interval and supports simultaneous transmissions on different SCHs. It enhances the performance of VANETs and decreases the CCH congestion. Moreover, we use RSU to record the rendezvous information and broadcast it to the OBUs. This method avoids the multi-channel hidden terminal problem. An analytical model is developed to evaluate the aggregate throughput on SCHs. This model considers the following factors: non-safety message transmission probability in each synchronous interval, average size of the non-safety message, and the number of OBUs. Furthermore, the requirement of obtaining the maximum throughput is computed. Simulation results are provided to validate the analytical model and to demonstrate the improvement in throughput. The results indicate that the proposed scheme can provide higher aggregate throughput than that of the vehicular enhanced multi-channel MAC and IEEE 1609.4, and better performance in CCH congestion control especially under high network load conditions.

GaS: A Gateway Scheduling-Based Beamforming Scheme for Handoff Support in Wireless Mesh Networks

Fast handoff support is a basic requirement for an Internet-based wireless mesh network (WMN), aiming to guarantee mobile users continuous connection to the Internet, regardless of their physical locations or moving trajectory. Due to the multihop transmission of network-layer handoff signaling packets, handoff performance in WMNs can be largely degraded by the increasing number of wireless hops as well as the channel access contentions between data and signaling packets in the mesh backbone. However, these issues are ignored in existing handoff solutions and multichannel medium-access control schemes. In this paper, we address the seamless handoff support from a different perspective and propose a gateway scheduling-based (GaS) beamforming scheme for handoff support in single-radio multichannel multihop WMNs. Our proposed beamforming scheme can realize single-hop handoff signaling packet transmissions and eliminate the channel contentions between data and signaling packets. Simulation results show that the total handoff delay is significantly improved using our proposed GaS beamforming scheme under various scenarios, as compared with existing handoff solutions in multihop WMNs. In addition, due to the single-hop transmission of signaling packets, the signaling overhead in the wireless mesh backbone can be substantially reduced.

A Novel Distributed Asynchronous Multichannel MAC Scheme for Large-Scale Vehicular Ad Hoc Networks

This paper proposes a novel distributed asynchronous multichannel medium access control (MAC) scheme for large-scale vehicular ad hoc networks (VANETs), i.e., asynchronous multichannel medium access control with a distributed time-division multiple-access mechanism (AMCMAC-D). The proposed scheme supports simultaneous transmissions on different service channels while allowing rendezvous and broadcast of emergency messages on the control channel. The scheme is distributed, because it handles access to the shared control channel for different access categories without relying on the beacon frames from roadside units. This condition eliminates the overhead that is associated with channel allocation, making the proposed scheme suitable for large-scale networks in terms of the number of active nodes. Service differentiation in the proposed scheme is enhanced by allocating different numbers of time slots for different access categories. We compare the performance of the proposed scheme with the IEEE 1609.4 standard and the asynchronous multichannel Coordination Protocol (AMCP) in terms of throughput, packet delivery rate, collision rate, utilization of service channels, service differentiation, and the penetration rate of noncollided emergency messages. The results show that AMCMAC-D outperforms the IEEE 1609.4 standard and AMCP in terms of system throughput by increasing the utilization of the control channel and service channels. The proposed scheme also demonstrates better performance in terms of packet delivery rate, collision rate on a service channel, load balancing, and service differentiation. Finally, AMCMAC-D mitigates the multichannel hidden terminal and missing receiver problems, which occur in asynchronous multichannel MAC schemes.

Can multiple subchannels improve the delay performance of RTS/CTS-based MAC schemes?

We analyze the delay performance of RTS/CTS-based (Request-To-Send/Clear-To-Send) multi-channel MAC (Medium Access Control) schemes for wireless networks. These schemes usually employ multiple data subchannels for data transmission and one control subchannel to send the RTS/CTS dialogue for channel reservation. Through theoretical analysis and simulations, we show that, in fully-connected networks, such multi-channel MAC schemes suffer longer delays than the corresponding single channel MAC scheme, that puts the RTS/CTS dialogue on the same channel as data packet transmissions. This conclusion holds even when data packets have different priorities and higher priority traffic is sent ahead of lower priority traffic.

Analyzing multi-channel medium access control schemes with ALOHA reservation

In order to improve the throughput performance of medium access control (MAC) schemes in wireless communication networks, some researchers proposed to divide a single shared channel into several sub-channels: one as control sub-channel and the others as data sub-channels. In this paper, we analyze and evaluate the maximum achievable throughput of a class of generic multi-channel MAC schemes that are based on the RTS/CTS (ready-to-send/clear-to-send) dialogue and on ALOHA contention resolution. We study these multi-channel MAC schemes under two split-channel scenarios: the fixed-total-bandwidth scenario and the fixed-channel-bandwidth scenario. In the fixed-total-bandwidth scenario, we show that the throughput of the multi-channel MAC schemes is inferior to that of the corresponding single-channel MAC scheme, which sends the RTS/CTS packets and DATA packets on a single shared channel. For the fixed-channel-bandwidth scenario, where CDMA or similar techniques can be applied, we derive the optimal number of the data sub-channels that maximizes the throughput. The analytical framework that we derive in this paper can also be used to evaluate other contention resolution technique, when the average contention period is known