A MAC layer protocol for real-time inter-vehicle communication

We examine the performance of inter-vehicle communication (IVC) systems using the IEEE802.11b standard CSMA scheme and a proposed system in which packet transmission timing is decided by the vehicle position. For the realization of safety cruise-assist systems by IVC systems, the spread of transceivers on vehicles is important. To improve the equipped rate of transceivers on vehicles, it is necessary that the implementation of more simple and cheaper IVC systems. One of the solutions is using conventional wireless LAN systems for IVC systems. So we evaluate the performance of an IVC system using the conventional IEEE802.11b CSMA system. In addition, we propose and evaluate an improvement scheme for solving the performance degradation caused by packet collision. The results of simulation show that the proposed scheme is superior to other schemes when the bit rate is low. Also, it is shown that the proposed scheme has the same or higher performance than the other schemes in high bit rate.

This paper discusses the IVC (Inter Vehicle Communication) system using the UWB (Ultra Wideband) radar. DSUWB (Direct Sequence - UWB) signal is used for this IVC system because it has CDMA (Code Division Multiple Access) Capability. However, there is the near-far problem due to difference of signal power from each vehicles, it becomes the cause of degradation of communication characteristics and detection accuracy of the signal. In this paper, we propose the iterative detection system using the SIC (Successive Interference Cancellation) to improve detection rate of the signal and the bit error rate (BER) performance. The signals except the desired signal detected by the SIC is subtracted from the original received signal. As the result, the performance was improved.

Networking methods and applications of the inter-vehicle packet communication system are discussed. In a proposed system, vehicles and roadside beacons broadcast individual ID, position, speed in a cyclic manner using time-dots allocated with a distributed algorithm. Other information is transmitted with the random access. The routing method using 1-hop cyclic information is applied to relay the information packet to farther terminals efficiently. This communication system is extensible and realize its applications efficiently. As a new remarkable application of the inter-vehicle communication system, we propose the drive control of vehicles. >

Mutual exchange of status data between vehicles in close proximity is the basis for safe vehicle operation. Application areas range from driver assistance/warning to fully autonomous driving. To enable this data exchange we need an intervehicle communication (IVC) system. Vehicles involved in mutual data exchange form a kind of local area network; however, the characteristics of this network are quite different from those of conventional networks. The configuration of this kind of network changes from time to time, in terms of organization, proximity group, group position, and relative position; therefore, it is very challenging to establish. The authors have been working on this problem from the point of view of communication media and protocol. The characteristics and requirements of IVC are discussed, and several preliminary communication protocols are proposed. The authors also present some experimental results from the implementation of a function integrating communication by infrared ray with a gap-measuring technique by the vision system.

Recent development has a tremendous growth in the ad-hoc wireless networks. Ad-hoc wireless networks are dynamic topology networks organized by a collection of mobile nodes that utilize multi-hop radio relaying and are capable of operating without the support of any fixed infrastructure. Ad-hoc wireless networks are very useful in emergency operations, collaborative and distributed computing and military applications. Multicasting plays an important role in the ad-hoc wireless networks, where nodes form groups to carry out certain tasks that require point-to-multipoint and multipoint-to-multipoint voice and data communication. The biggest challenge in the ad-hoc wireless networks is to find an optimized path between the two nodes. In this paper, we present an ant colony based metaheuristic multicast routing protocol for ad-hoc wireless networks, in that we analyzed the performance of dynamic core based multicast routing protocol (DCMP). This approach maps the solution capability of swarm intelligence to mathematical and engineering problems. The DCMP is highly adaptive, efficient and scalable. The performance of these protocols has been examined under realistic scenarios using NS 2, the network simulator tool. Performance has been analyzed for the metrics packet delivery ratio and control overheads with the multicast routing protocol. The proposed ant colony based routing protocol reduce the overheads in routing.

A novel collaborative strategy employing two relays is developed for the multihop inter-vehicle communication (IVC) systems in this paper, which has great complexity degradation. Instead of the traditional terminal collaboration or relay tier space-time coding (STC), a relay tier interaction is proposed. Considering time division multiple access (TDMA) scheme, two spatial adjacent vehicles are conjoined by an interaction radio link to create a virtual antenna array (VAA). Then the collaborative two-relay is integrated into a multihop IVC network mentioned above, which enables a single-antenna terminal to share its antenna with other terminals easily, and avoids the synchronization or other complicated requirements in terminal collaboration or STC systems. Furthermore, except the low complexity in hardware implementation, the proposed method also can enhance the performance of the IVC systems over both the quasi-static fading channel and time varying Rayleigh fading relay channel, which is verified through the Monte-Carlo simulations

In wireless mobile ad-hoc networks, data packets have to be relayed hop by hop from a given source node to a destination node. This means that some or all of the mobile nodes must accept to forward information for the benefit of other nodes. It has been shown by F. Nait-Abdesselam, et al., (2003) that this ability of forwarding packets leads to a new unfairness problem in wireless ad-hoc networks, where a node which is forwarding other node's packets gets less bandwidth, for its own use, than a node which is not participating to the routing service. The proposed RAMAC scheme by F. Nait-Abdesselam, et al., (2003), has shown all its effectiveness to cope with this unfairness problem. However, an extra bandwidth is sometimes allowed to the routing node's own traffic comparing to other nonrouting node's own traffics, and the routing node's routed traffic gets much less bandwidth. This is explained by the fact that at the upper layer (for instance the IP layer) does not differentiate between the routing and the own traffics, and that the multiplicative factor used to compute the new contention window is too aggressive. In this paper, an enhanced RAMAC scheme is proposed, by taking into account the differentiation on top of the MAC layer, between the and routed traffics within a routing node, and by smoothing the multiplicative factor used to compute the new contention window. The simulation results obtained showed a good improvement of the original RAMAC scheme, leading to better approximate equal bandwidth share among all the mobile nodes in the wireless ad-hoc network.

Engineering real-time communication protocols is a complex task, particularly in the safety-critical domain. Current protocols exhibit a strong tradeoff between flexibility and the ability to detect and handle faults in a deterministic way. Model-driven engineering promises a high level design of verifiable and directly runnable implementations. Arrangements of logic-labelled finite-state machines (LLFSMs) allow the implementation of complex system behaviours at a high level through a subsumption architecture with clear execution semantics. Here, we show that the ability of LLFSMs to handle elaborate hierarchical module interactions can be utilised towards the implementation of testable, safety-critical real-time communication protocols. We present an efficient implementation and evaluation of INCUS, a time-triggered protocol for safety-critical real-time communication that transcends the rigidity imposed by existing real-time communication systems through the use of a high-level subs umption architecture.

The development of practical, localization algorithms is probably the most needed and most challenging task in wireless ad-hoc sensor networks (WASNs). Localized algorithms are a special type of distributed algorithms where only a subset of nodes in the WASN participate in sensing, communication, and computation. We have developed a generic localized algorithm for solving optimization problems in wireless ad-hoc networks that has five components: (i) data acquisition mechanism, (ii) optimization mechanism, (iii) search expansion rules, (iv) bounding conditions and (v) termination rules. the main idea is to request and process data only locally and only from nodes who are likely to contribute to rapid formation of the final solution. The approach enables two types of optimization: The first, guarantees the fraction of nodes that are contacted while optimizing for solution quality. The second, provides guarantees on solution qualities while minimizing the number of nodes that are contacted and/or amount of communication. The localized optimization approach is applied to two fundamental problems in sensor networks: location discovery and exposure-based coverage. We demonstrate its effective-ness on a number of examples

Geographic routing protocols establish scalable and robust routes for multi-hop trsdansmission in wireless mobile ad-hoc networks, where accurate location information of the mobile nodes is needed. Aiming to alleviate the influence of location errors, existing works focus on modifying routing protocols through modeling the error sources and mobility prediction. In this paper, we propose a cooperative cluster based geographic routing (CCGR) protocol, which views the cooperative cluster as one virtual relay node, and lessens the impact of location errors through opportunistic receiving and cooperative radio range extension. Opportunistic receiving achieves the link diversity and radio range extension enlarges the transmission distance of one hop. The performance of CCGR is analyzed under scenarios of both static and mobility location errors in terms of reliability index, which is defined to represent the link stability. Further more, numerical results demonstrate that our proposed transmission scheme CCGR outperforms non-cooperative routing schemes in terms of link error probability with location errors.

Minimizing interference of a wireless ad-hoc network in a plane

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Inter-vehicle wireless communication systems are currently being developed as a promising technology to improve traffic safety. Considering their decentralized nature, its deployment faces important challenges to guarantee an efficient and reliable transmission of broadcast safety messages. This paper investigates the dimensioning of such systems by analysing the impact of key operating conditions on its performance. The final aim of this investigation is to identify efficient radio resource management techniques for inter-vehicle wireless systems.

Broadcasting is an essential operation for Wireless Ad Hoc Networks to perform routing path discovery, and it has become the predominant technology for message dissemination in Vehicular Ad Hoc Networks (VANETs). In the reactive routing schemes of wireless ad hoc network, Routing Request (RREQ) packets are broadcast from the source, and once received the destination traces back the broadcasting path to build an on-demand route. In VANETs, different broadcasting schemes have been proposed for safety, comfort, and commercial applications. However, broadcasting usually generates a lot of redundant messages which would cause excessive channel contention and packet collisions, especially when the density of the network becomes higher. In this survey article, we first introduce the most common data dissemination techniques used in wireless ad hoc networks. After that, we discuss techniques that have been proposed to mitigate the broadcast storm problem. Finally, we introduce an effective model for analyzing the broadcasting schemes, and based on the model we propose an adaptively adjusted probabilistic scheme that highly improves the reliability of broadcasting in dense ad hoc networks.

In this paper, LMS (Least Mean Square) adaptive array antenna is applied to IVC(Inter-Vehicle Communication) in order to reduce interference which is caused by surrounding vehicles. The LMS adaptive array antenna has a characteristic that the control of directivity is possible according to surrounding radio wave condition, if the receiving vehicle knows the information of the target vehicle. Under the case where the adaptive array antenna is used in IVC systems, packet error rate characteristic, throughput performance and improvement in near-far problem are evaluated by comparing with the performance of the IVC system using omni-directional antenna.