Interference in ad hoc WLANs is a common occurrence as there is no centralized access point controlling device access to the wireless channel. IEEE 802.11 WLANs use carrier sense multiple access with collision avoidance (CSMA/CA) which initiates the Request to Send/Clear to Send (RTS/CTS) handshaking mechanism to solve the hidden node problem. While it solves the hidden node problem, RTS/CTS triggers the exposed node problem. In this paper, we present an evaluation of a method for reducing exposed nodes in 802.11 ad hoc WLANs. Using asymmetric transmission ranges for RTS and CTS frames, a cross-layer design is implemented between Layer 2 and 3 of the OSI model. Information obtained by the AODV routing protocol is utilized in adjusting the RTS transmission range at the MAC Layer. The proposed method is evaluated with the NS-2 simulator and we observe significant throughput improvement, and confirm the effectiveness of the proposed method. Especially when the mobile nodes are randomly distributed, the throughput gain of the Asymmetric RTS/CTS method is up to 30% over the Standard RTS/CTS method.

In mobile ad hoc networks, a malicious node can respond with a faked route reply (RREP) message to a source that explores a route in order to make the source establish a false route leading to the malicious node. Then, the malicious node can absorb all transmitted packets like a black hole. This paper proposes a totally secure defense against the black hole attack with low control overhead and high reliability. The proposed approach, named a bullet-proof verification (BPV) method, consists of a detection phase, in which a node detects a suspicious node by analyzing the data routing information of its neighbors and a verification phase, in which a node initiates the verification of a suspicious node conditionally only if it receives RREP from the suspicious node. The crux of this approach lies in using an encrypted verification message that goes straight to the destination through the path that may include some malicious nodes and also in using both destination sequence number and hop distance for verification. In addition, a distributed watchdog mechanism is employed to track down any malicious nodes. Simulation results show that the BPV approach reduces control overhead significantly and defends against black hole attack reliably.

In this paper a novel and effective two phase admission control (TPAC) for QoS mobile ad hoc networks is proposed that satisfies the real-time traffic requirements in mobile ad hoc networks. With a limited amount of extra overhead, TPAC can avoid network congestions by a simple and precise admission control which blocks most of the overloading flow-requests in the route discovery process. When compared with previous QoS routing schemes such as QoS-aware routing protocol and CACP protocols, it is shown from system simulations that the proposed scheme can increase the system throughput and reduce both the dropping rate and the end-to-end delay. Therefore, TPAC is surely an effective QoS-guarantee protocol to provide for real-time traffic.

In Vehicular Ad hoc Networks (VANETs), general purpose ad hoc routing protocols such as AODV cannot work efficiently due to the frequent changes in network topology caused by vehicle movement. This paper proposes a VANET routing protocol QLAODV (Q-Learning AODV) which suits unicast applications in high mobility scenarios. QLAODV is a distributed reinforcement learning routing protocol, which uses a Q-Learning algorithm to infer network state information and uses unicast control packets to check the path availability in a real time manner in order to allow Q-Learning to work efficiently in a highly dynamic network environment. QLAODV is favored by its dynamic route change mechanism, which makes it capable of reacting quickly to network topology changes. We present an analysis of the performance of QLAODV by simulation using different mobility models. The simulation results show that QLAODV can efficiently handle unicast applications in VANETs.

Routing in wireless ad hoc networks is a challenging issue because it dynamically controls the network topology and determines the network performance. Most of the available protocols are based on single-rate radio networks and they use hop-count as the routing metric. There have been some efforts for multirate radios as well that use transmission-time of a packet as the routing metric. However, neither the hop-count nor the transmission-time may be a sufficient criterion for discovering a high-throughput path in a multirate wireless ad hoc network. Hop-count based routing metrics usually select a low-rate bound path whereas the transmission-time based metrics may select a path with a comparatively large number of hops. The trade-off between transmission time and effective transmission range of a data rate can be another key criterion for finding a high-throughput path in such environments. In this paper, we introduce a novel routing metric based on the efficiency of a data rate that balances the required time and covering distance by a transmission and results in increased throughput. Using the new metric, we propose an on-demand routing protocol for multirate wireless environment, dubbed MR-AODV, to discover high-throughput paths in the network. A key feature of MR-AODV is that it controls the data rate in transmitting both the data and control packets. Rate control during the route discovery phase minimizes the route request (RREQ) avalanche. We use simulations to evaluate the performance of the proposed MR-AODV protocol and results reveal significant improvements in end-to-end throughput and minimization of routing overhead.

In this paper, we propose a new method using dynamic linkage with IP-based infrastructure to compose a wide-area MANET. The proposed method extends AODV and enables searches for destinations in the IP-based infrastructure. The proposed method settles the low scalability problem by creating shortcuts in the IP network. In addition, to overcome the geographical dependence problem, the proposed method connects terminals that are out of radio range with each other by using the IP-based infrastructure. In this way, the proposed method can flexibly establish a wide-area MANET that is scalable and free from geographical constraint.

Much recent research concentrates on designing an Intrusion Detection System (IDS) to detect the misbehaviors of the malicious node in MANET with ad-hoc and mobility natures. However, without rapid and appropriate IDS response mechanisms performing follow-up management services, even the best IDS cannot achieve the desired primary goal of the incident response. A competent containment strategy is needed to limit the extent of an attack in the Incident Response Life Cycle. Inspired by the T-cell mechanisms in the human immune system, we propose an efficient MANET IDS response protocol (T-SecAODV) that can rapidly and accurately disseminate alerts of the malicious node attacks to other nodes so as to modify their AODV routing tables to isolate the malicious nodes. Simulations are conducted by the network simulator (Qualnet), and the experiment results indicate that T-SecAODV is able to spread alerts steadily while greatly reduce faulty rumors under simultaneous multiple malicious node attacks.

In case of link failures, many ad hoc routing protocols recover a route by employing source-initiated route re-discovery, but this approach can degrade system performance. Some use localized route recovery, which may yield non-optimal paths. Our proposal provides a mechanism that can enhance the overall routing performance by initiating route recovery at the destination node. We elucidate the effects through simulations including comparisons with AODV and AODV with local repair.

Video multicast over wireless medium has gained increasing popularity in a wide range of applications, such as video-on-demand and group video conferencing. With mobile ad hoc networks emerging as a promising solution for future ubiquitous communications, supporting reliable video multicast over mobile ad hoc networks is a timely research topic. In this paper we tackle this issue by using multiple tree multicast routing protocol. Specifically, we introduce an extension to the Multicast Ad Hoc On-demand Distance Vector (MAODV) routing protocol to construct two optimally disjoint trees in a single routine. The extended protocol is called Multiple Tree Multicast Ad Hoc On-demand Distance Vector (MT-MAODV) routing protocol. In order to distribute the video evenly and independently between these disjoint trees, the Multiple Description Coding (MDC) scheme is used for video coding. Simulation shows that the proposed protocol demonstrates video multicast with better quality than the conventional video multicast using a single tree only.

In this paper, we propose SDRP: a new service discovery protocol combined with routing policies in MANETs. The protocol is performed upon a distributed network. We describe a service by a unique ID number and use a group-cast routing policy in advertisement and request. In addition, the nodes included in the reply path also cache the advertisement information. We compare SDRP with both Flood and MAODV in terms of overload, and average delay. Simulation results show SDRP can spend less response time and accommodate even high mobility network environments.

The single path routing protocol, known as the Ad Hoc On-demand Distance Vector, has been widely studied for use in mobile ad hoc networks. AODV requires a new route discovery whenever a path breaks. Such frequent route discoveries cause a delay due to route discovery latency. To avoid such inefficiency, a multipath routing protocol has been proposed that attempts to find link-disjoint paths in a route discovery. However, when there are two or more common intermediate nodes on the path, the protocol can not find a pair of link-disjoint paths even if the paths actually exist. To reduce this route discovery latency, it is necessary to increase the opportunities for finding a pair of link-disjoint paths. In this paper, we focus on AODV and propose an AODV-based new multipath routing protocol for mobile ad hoc networks. The proposed routing protocol uses a new method to find a pair of link-disjoint paths by selecting a route having a small number of common intermediate nodes on its path. Using simulation models, we evaluate the proposed routing protocol and compare it with AODV and the existing multipath routing protocol. Results show that the proposed routing protocol achieves better performance in terms of delay than other protocols because it increases the number of cases where a pair of link-disjoint paths can be established.

The AODV (Ad Hoc On-Demand Distance Vector) protocol is one of the typical reactive routing protocols in Ad Hoc networks, in that mobile nodes initiate routing activities only in the presence of data packets in need of a route. In this paper, we focus upon the local repair mechanism of AODV. When a link is broken, the upstream node of the broken link repairs the route to the destination by initiating a local route discovery process. The process involves the flooding of AODV control messages in every node within a radius of the length from the initiating node to the destination. In this paper, we propose an efficient local repair scheme for AODV, called AELR (AODV-based Efficient Local Repair). AELR utilizes the existing routing information in the downstream intermediate nodes which have been on the active route to the destination before a link break occurs. AELR can reduce the flooding range of AODV control messages and the route recovery time for route recovery because it can repair a route through the nearby downstream intermediate nodes. The performance results show that AELR can achieve faster route recovery than the local repair mechanism of AODV.