Kazi Atiqur Rahman

Characterization of the adverse effect of neighborhood capture in MANET and on the way to a remedy

The current era of mobile communication is passing through the days of rapidly changing technologies. A technology which holds promise to bring surprise to the future users is ad hoc networks. The multiple access procedure in ad hoc networks is not error prone till now, although significant researches are going on in its MAC layer. The communications in ad hoc networks are adversely affected by the neighborhood capture problem along with some other problems like hidden station problem, exposed station problem as well as channel capture problem. This paper will characterize the adverse effect of neighborhood capture problem with two views of a remedy and some analytical results

Extended sliding frame R-Aloha: Medium access control (MAC) protocol for mobile networks

Proliferation of mobile communication devices necessitates a reliable and efficient medium access control (MAC) protocol. In this paper, A MAC protocol, called extended sliding frame reservation Aloha (ESFRA), based on sliding frame R-Aloha (SFRA) is proposed for network access technique. ESFRA is particularly designed to solve the mobile hidden station (MHS) problem in a mobile ad hoc network (MANET) by including relative locations of transmitting stations in the packet frame information header. The MHS problem is unique in mobile networks and occurs if a mobile station enters in a collision free zone of any ongoing communication and disturbs this communication with its transmission. In addition to the MHS problem, ESFRA simultaneously solves hidden station, exposed station, and neighborhood capture problems typically observed in wireless networks. A Markov model of ESFRA is developed and provided here to estimate throughput, delay and collision probabilities of the proposed protocol. The Markov modeling is extended to the analysis of SFRA and IEEE 802.11 to compare these competing MAC protocols with ESFRA. The analysis shows that ESFRA decreases frame transmission delay, increases throughput, and reduces collision probabilities compared to IEEE 802.11 and SFRA. ESFRA improves the network throughput 28 percent compared to that of IEEE 802.11, and 33 percent compared to that of SFRA. The improved performance is obtained at the expense of the synchronization compared to IEEE 802.11, but there is virtually no extra cost compared to SFRA.

Towards a cross-layer based MAC for smooth V2V and V2I communications for safety applications in DSRC/WAVE based systems

The DSRC/WAVE system is standardized to disseminate safety critical information using IEEE 802.11p as a MAC protocol. Studies show that IEEE 802.11p does not address adverse effects of asymmetric radio link and mobility related problems in vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications. This paper presents a cross-layer (i.e. MAC and network) algorithm to address these problems for making the V2V and V2I communications efficient and reliable. The analysis shows that the proposed cross-layer algorithm removes contention in channel accessing and confirms a better channel utilization. The solution can be used to disseminate information up to three hops without using a routing protocol. This is particularly important for extending range of safety critical and emergency related messages in the vehicular network.

Markov analysis of the mobile hidden station problem in MANET

This paper provides Markov analysis of mobile hidden station problem in the medium access control (MAC) layer of vehicular/mobile ad hoc networks (VANET/MANET). If a mobile station enters a collision free zone of any ongoing communication and interferes with this communication, it is called a mobile hidden station, and problems associated with mobile hidden stations is called mobile hidden station problem. The mobile hidden station problem severely degrades the throughput and the delay performances of mobile networks. In order to show the effect of mobile hidden station problem, the Markov models of IEEE 802.11 with and without mobile hidden station problem are developed. The developed models show that mobile hidden station increases collisions at the receivers and decreases the throughput up to 36 percent. This paper shows that mobile hidden station problem must be resolved while designing a MAC layer protocol for VANET/MANET.

Analyzing extended sliding frame reservation-aloha MAC protocol against asymmetric radio link problem in MANET/VANET

Asymmetric/unequal radio links (ARL) in wireless communication can occur in MANETs/VANETs for many reasons such as hardware limitations, power saving protocols, shadowing effects, dynamic spectrum managements. Although largely overlooked, these ARLs are responsible for problems like hidden stations and exposed stations. This paper presents how Extended Sliding Frame Reservation Aloha (ESFRA) solves networking problems associated with ARLs. Performance of ESFRA has been compared to competing MAC protocols, namely IEEE 802.11 MAC and SFRA, proposed for VANETs. The simulation result shows that ESFRA provides about 80% channel utilization considering the effects of hidden stations due to ARLs.

Analyzing sliding frame reservation-Aloha MAC protocol against mobile hidden station problem in MANET

In this paper, the sliding frame reservation Aloha (SFRA) MAC protocol is analyzed considering the adverse effects of mobile hidden station problem. This paper also presents how SFRA addresses neighborhood capture problem. The analysis shows that any distributed protocol like IEEE 802.11 does not address the adverse effects of these problems. Probabilities of successful transmissions considering a variable number of mobile hidden stations as well as the channel accessing probabilities of a blocked station are calculated in this paper by using Combinatorics theory. The analysis shows that SFRA provides about 80 percent probability of successful transmission with two active mobile hidden stations.

A mobility tolerant routing algorithm for vehicular ad hoc networks

This paper presents a vehicular ad hoc network routing protocol with link expiration time (VARP-LET) that uses LET information in the creation of routes. The proposed protocol uses LET information to increase the reliability and stability of the routes. In addition to LET, a route break indicator (RBI) message is used to reduce the packet loss. The effective use of LET and RBI is tested in simulated network environment using NS-2. The simulation results show that VARP-LET protocol increases packet delivery ratio by 20.7% in Manhattan mobility model and by 30% in highway mobility scenario compared to the traditional AODV protocol. It is also shown that the protocol significantly reduces frequent route failure and routing overhead.

Reliable MAC layer designs for vehicular networks

This paper discusses mobile hidden station (MHS) problem which is a significant source of packet collisions in medium access control (MAC) protocols of vehicular networks due to relatively high node speeds. MHS problem occurs when mobile stations that are not present in the channel reservation period enter and disturb the existing communications. We present effect of MHS problem using Markov model of carrier sense multiple access with collision avoidance (CSMA/CA). Then we present how MHS affects the repetition broadcast protocols using analytical analysis results. Finally, protocols that mitigate effect of MHS at MAC layer for both infotaintment communication and safety broadcast messaging are presented. MAC protocol for infotaintment is Enhanced Sliding Frame Reservation Aloha (ESFRA) and for safety broadcast messaging is Passive Cooperative Collision Warning (PCCW). With these protocols, it is verified that effect of MHS is significantly reduced, which result in lower delay and significant improvement in reliability. Both analytical analysis and simulation results agree.

Mobility Assisted Routing in Mobile Ad Hoc Networks

This paper presents an algorithm to include mobility in a routing protocol to reduce packet losses in mobile ad hoc networks (MANETs). The algorithm is applicable to any on-demand routing protocol. If the degree of mobility of any node in any route increases, the route life time decreases. That causes frequent link failures, and results more packet loss and low throughput. Packet loss requires packet retransmissions, which further overload the network and can cause additional latency and packet loss. The proposed algorithm estimates the number of packets that can traverse through the route before it breaks be-cause of mobility. This algorithm increases network throughput and packet delivery ratio. The algorithm is implemented in dynamic source routing (DSR) protocol, and simulated in Network Simulator-2. The simulation results show that the packet delivery ratio of DSR with the algorithm can improve up to forty six percent over DSR in mobile ad hoc networks.

A probabilistic measure of extended reservation Aloha MAC protocol against some MAC problems in MANET

Mobile hidden station and neighborhood capture problems severely affect the communication in the MAC layer of a mobile ad hoc network. IEEE 802.11 cannot prevent blocking due to neighborhood capture problem and collisions due to mobile hidden station problem. Extended reservation-Aloha (ERA) solves these two problems in a probabilistic manner along with solving widely known hidden station and exposed station problems. This paper provides a probabilistic view of ERA to neighborhood capture and mobile hidden station problems. The analysis shows that the channel accessing probability of a station facing neighborhood capture problem is more than 90 percent with 60 percent traffic.