Connectivity in a Multi-radio, Multi-channel Heterogeneous Ad Hoc Network

Abstract. Future wireless networks are expected to integrate heterogeneous devices equipped with multiple radios and different characteristics. Nodes equipped with a single communication interface will co-exist with nodes equipped with multiple radios that can transmit and receive simultaneously. Therefore, it is important to understand how these heterogeneous radios can affect connectivity and overall multihop network performance. Maintaining connectivity in ad hoc networks has been a major challenge and many complex topology control algorithms have been investigated. In this paper, we study the connectivity of a heterogeneous ad hoc network. We consider two types of nodes: nodes equipped with a single communication interface with communication range r, and Dual-Mode (DM) nodes, equipped with two communication interfaces with two different communication ranges r and rf, respectively, where rf>r. We assume the radios in the DM nodes operate in two different channels. We provide a theoretical analysis of connectivity in a linear network and we present simulation results for the two-dimensional case that show the impact of DM nodes on connectivity, broadcast latency and robustness in static and mobile scenarios. 1

MDA: An Efficient Directional MAC scheme for Wireless Ad Hoc Networks

This paper addresses the issue of deafness and hidden terminal problem in a Mobile Ad Hoc Networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) which employs an enhanced directional network allocation vector (NAV) scheme and, a novel technique of Diametrically Opposite Directions (DOD) transmission of RTS and CTS. We compare MDA with IEEE 802.11 and two recently proposed directional MAC protocols and results show that MDA outperforms these protocols in the majority of scenarios investigated. We also point out that the performance does depend on the network topology and the traffic pattern

Motorola, Inc.

Abstract – In this work we addresses the issue of deafness and hidden terminal problem in Mobile Ad Hoc Networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) 5 which employs a novel Enhanced Directional Network Allocation Vector (EDNAV) scheme and, and an efficient technique of Diametrically Opposite Directions (DOD) transmission of RTS and CTS. We compare MDA with IEEE 802.11 and two recently proposed directional MAC schemes and results show that MDA outperforms these protocols in the majority of scenarios investigated. We also point out that the performance does depend on the network topology and the traffic pattern. Keywords: IEEE 802.11, MAC, Directional Antenna, Wireless Ad Hoc Networks. 1

Drp: An efficient directional routing protocol for mobile ad hoc networks

Abstract: This paper addresses the issue of routing in mobile ad hoc networks (MANETs) using directional antennas. Existing directional routing schemes either assume a complete network topology beforehand or simply use omni-directional routing schemes to forward packets in underlying directional environment. In this paper we propose a Directional Routing Protocol (DRP) for MANETs. DRP is an on-demand directional routing protocol which assumes a cross layer interaction between routing and MAC layer and is inspired by Dynamic Source Routing (DSR) protocol. The main features of DRP include an efficient route discovery mechanism, establishment and maintenance of directional routing and directional neighbor tables (DRT and DNT respectively) and novel directional route recovery mechanisms. We have implemented DRP on top of MDA, a MAC protocol for directional antennas and have compared its performance with the DSR protocol over both omni-directional and directional antenna models. Our results show that DRP considerably improves the packet delivery ratio, decreases the end to end packet latency, has lesser routing overhead and is robust to link failures

The Deafness Problems and Solutions in Wireless Ad Hoc Networks using Directional Antennas

Abstract – This paper addresses the issue of deafness in directional antennas for wireless ad hoc networks. Deafness is caused when a node X repeatedly attempts to communicate with node Y but is unsuccessful, because Y is presently tuned to some other antenna beam. In this paper, we first outline different factors which contribute to such deafness in directional antennas and its significant impact on network performance. We then propose two schemes to overcome deafness scenarios which are transparent to the underlying directional MAC protocol in use. In addition, we also claim that IEEE 802.11 Short Retry Limit (SRL) needs a special handling in directional environment because of the presence of deafness. We have done a detailed performance evaluation of our schemes with different directional MAC protocols running over switched beam antennas and the initial results are found to be very promising. Keywords: MAC, Deafness, Directional Antennas, MANETs. 1

Cross-Layer Directional Antenna MAC and Routing Protocols for Wireless Ad Hoc Networks

Abstract – In this paper we propose a Directional Antenna Medium Access (DAMA) protocol and its enhanced version called EDAMA (enhanced DAMA), which takes advantage of the benefits offered by directional antennas. Both of these schemes have been inspired by the IEEE 802.11 MAC, with major enhancements including a new neighbor discovery scheme, an optimized circular directional transmission of RTS and CTS to prevent the hidden node problem, reduce collisions and decrease node deafness, and also a multi-buffer management scheme. A pair of communicating nodes using these schemes simultaneously transmits the circular directional RTS and CTS only to those sectors with neighbors, hence reducing overall communication delay and enhancing throughput. The main difference between DAMA and EDAMA lies in the way buffering is provided in the MAC layer. Unlike DAMA which uses a single MAC buffer for all antenna beams as in IEEE 802.11, EDAMA employs separate buffers for each of the antenna sectors and introduces an integrated network and MAC cross-layer design. This helps in eliminating the “self induced blocking ” problem prominent in most existing directional MAC protocols including DAMA. We have compared DAMA, EDAMA, IEEE 802.11 and two recently proposed directional MAC protocols, and results show that DAMA and EDAMA perform better than existing MAC protocols in the majority of the scenarios investigated, while EDAMA is observed to perform best. We also point out that the performance usually depends on the network topology and traffic pattern