Scalable unidirectional routing with zone routing protocol (ZRP) extensions for mobile ad-hoc networks

Abstract

Abstract-Ad-Hoc Networks consist of peer-to-peer communicating nodes that are highly mobile. As such, an ad-hoc network lacks infrastructure and the topology of the network changes dynamically. The task of routing data from a source to a destination in such a network is challenging. Several routing protocols have been proposed for wireless ad-hoc networks. Most of these protocols, however, pre-suppose the presence of bi-directional links between the nodes in the network. In reality the ad-hoc network may consist of heterogeneous nodes with different power capabilities and hence, different transmission ranges. When this is the case, a given node might be able to receive the transmission of another given node but might not be able to successfully transmit to the latter. Thus, unidirectional links are formed. Most of the current routing protocols are unsuitable for deployment when such unidirectional links are present. We consider a routing protocol called the zone routing protocol (ZRP) that has been proposed for wireless ad-hoc networks with bi-directional links. The zone routing protocol employs a hybrid proactive (table driven) and reactive (ondemand) methodology to provide scalable routing in the ad-hoc network. However, in the presence of unidirectional links some routes remain undiscovered if ZRP is used. We propose extensions to ZRP to support its deployment when unidirectional links are present. In particular, we propose a query enhancement mechanism that recursively builds partial routes to a destination. Simulation results show that even at a high mobility of 20m/s, the queries resulting due to the enhancement mechanism result in the computation of valid routes more than 80% of the time. These results are valid even when a large number (40% of nodes have half the transmission range as that of the remaining nodes) of unidirectional links are present in the network.

Handling asymmetry in power heterogeneous ad hoc networks

“…Handling Link Asymmetry At the Routing Layer: Routing in the presence of unidirectional links has been studied in [2,3,19,27,31]. In [19], authors propose to bypass the unidirectional links and route the packets via only bi-directional links; this strategy may lead to the overloading of certain links, while under-utilizing others.…”

“…In [3], reverse multi-hop paths are used to proactively discover and use unidirectional links. In [31], the authors extend the well-known Zone Routing Protocol (ZRP) [10] to support unidirectional links. With these routing schemes, at the MAC layer either the traditional IEEE 802.11 MAC protocol is employed, or an ideal MAC protocol that can handle unidirectional links is assumed.…”

“…Link asymmetry at the MAC layer has also been studied in [4] and [18]; however, these studies are limited to certain scenarios with strict assumptions. In parallel, [19], [24], [3], [2], [31] propose methods for routing in the presence of unidirectional links; however, most of these studies ignore interactions with the MAC layer. Specifically, they either (i) employ the traditional IEEE 802.11 MAC protocol, which is inefficient with link asymmetry, or (ii) they assume an ideal MAC protocol which can only function effectively in the presence of unidirectional links.…”

On demand multicast routing with unidirectional links

“…This problem is referred to as the asymmetric/unidirectional link problem in routing. Recently, a number of researchers investigated the impact of unidirectional links on the performance of unicast routing protocols and developed new routing protocols to handle the problem [6][8] [16].…”

Handling Asymmetry in Power Heterogeneous Ad Hoc Networks: A Cross Layer Approach

“…Specifically, at the MAC layer, this leads to an exacerbation of the hidden terminal problem [5]. Routing becomes more complex due to the presence of such unidirectional links [15,17,19,20].…”