When a jamming attack occurs, existing ad hoc routing protocols can experience significant throughput degradation and unnecessary control overhead due to the inclusion of unreliable links into routing paths. In this work, we identify which factors hinder establishment of reliable routing paths by the existing routing protocols in the face of jamming attacks. Our solution is Jamming-Aware Routing (JAR) based on OLSR protocol, which provides explicit route recovery procedures to counteract jamming attack. By establishing a reliable routing path, the proposed scheme achieves significant throughput gains as well as control overhead reduction.

In this letter, we reveal redundant control traffic in the optimized link state routing protocol (OLSR) for MANET. Topology control (TC) messages, which occupy a part of control traffic in OLSR, are used to exchange topology information with other nodes. TC messages are generated and forwarded by only nodes that have been selected as multipoint relays (MPRs) by at least one neighbor node. These nodes selected as MPRs are called TC message senders in this letter. One of solutions to reduce the number of TC messages is to reduce the number of TC message senders. We describe a non-distributed algorithm to minimize the number of TC message senders. Through simulation of static-node scenarios, we show 18% to 37% of TC message senders in RFC-based OLSR are redundant. By eliminating redundant TC message senders, the number of TC packets, each of which contains one or more TC messages, is also reduced from 19% to 46%. We also show that high density scenarios have more redundancy than low density scenarios. This observation can help to consider a cooperative MPR selection in OLSR.

In OLSR (Optimized Link State Routing Protocol), the multipoint relay mechanism has been introduced to minimize routing overhead for flooding control traffic. In order to achieve as low a routing overhead as possible, the selection of MPRs (multipoint relays) is designed to limit the overall number of such relays in the network. OLSR provides the shortest paths in terms of hops; however, it does not take into account the QoS (quality of service) requirements. Therefore, QOLSR (Quality OLSR), which adds a QoS extension to the OLSR, has been proposed. Although QOLSR provides the best QoS path, its selection process does not consider the number of MPRs, which causes an increase in the routing overhead. In this paper, we focus on the selection process of MPRs in link state QoS routing protocol. We propose three heuristics for high-efficiency selections: MIMS, MQES, and MCIS. The basic approach of these selections is to determine a smaller set of MPRs that provide better QoS paths between any two nodes. The main objective in doing so is to maximize the QoS effect while limiting the routing overhead. In addition, we evaluate the performance of the routing protocols with the proposed selections by simulation. The results indicate that MIMS and MCIS achieve high-efficiency selection; as compared to QOLSR, MIMS reduces the maintenance cost by 30%, while the throughput of the resultant path is decreased by 13%, and MCIS reduces the cost by 21% without any decrease in the throughput.

IETF MANET (Mobile Ad Hoc Network) WG has standardized OLSR (Optimized Link State Routing) as its proactive routing protocol. In addition, TCP (Transmission Control Protocol) is still needed for MANET thanks to its suitability for smooth integration with the fixed Internet. In particular, TCP-Vegas is a well-known transport protocol that can efficiently take account of network condition. However, TCP-Vegas that requires an accurate BaseRTT estimation cannot be directly applied to MANET because a route change makes the estimated BaseRTT obsolete. We propose a technique to improve the performance of TCP-Vegas by considering the route change, and show the performance improvement through simulation study using the ns-2 simulator.

The Multi-Point Relay (MPR) of the Optimized Link State Routing protocol reduces the flooding overhead compared with classic flooding. To select MPR nodes, HELLO messages are used. In dense population environments, the overhead of HELLO messages is critical because the HELLO messages carry all adjacent node IDs in the classical manner. Consequently, wireless bandwidth is consumed for data communications. One solution for this problem is to compress HELLO messages using a differential technique. However, few, if any, studies have applied a differential technique to HELLO messages. We introduce the novel Differential HELLO technique to reduce the overhead of the HELLO messages. The Differential HELLO technique consists of two kinds of compression methods: Chronological Compression and Topological Compression. In addition, the inconsistency problems of the 1-hop node information in adjacent nodes caused by packet loss are discussed. As solutions to the inconsistency problems, No Compression Acknowledgement (NC-ACK) and HELLO Information Forecast (HIF) have been examined. Our simulation has taken the efficiency of the Differential HELLO technique into consideration. The HELLO message overhead was reduced to 29.1 IDs from 75.8 IDs using the Differential HELLO technique at a packet loss rate of 10-4 under random node arrangement. This result reveals that the Differential HELLO technique reduces the classic HELLO overhead by 38%. In environments with lower packet-loss rates, the Differential HELLO technique promises to offer even better performance.