Performance comparison of hop count and radio aware path selection protocols in IEEE 802.11s WLAN Mesh networks Sana Ghannay *† LIP6 University of Paris-VI 104, Avenue Pd Kennedy 75016, Paris, France Email: sana.ghannay@lip6.fr Sonia Mettali Gammar and Farouk Kamoun † National School of Computer Sciences CRISTAL Laboratory 2010 Manouba, Tunisia Emails: sonia.gammar@ensi.rnu.tn, frk.kamoun@planet.tn Abstract— IEEE 802.11s wireless LAN mesh network technol- ogy is the next step in the evolution of wireless architecture. A WLAN mesh network consists of WLAN devices with relay functions that communicate directly. In this type of networks, path selection is based on two protocols: RM-AODV and RA- OLSR. These protocols use MAC addresses (layer 2 routing) and use a radio-aware routing metric for the calculation of paths. This paper presents a study of the performance of the proposed path selection algorithms under different scenarios and a comparison with hop count routing protocols AODV and OLSR. I. I NTRODUCTION WLAN mesh networks are anticipated to deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. The main characteristic of wireless mesh networking is the communication between nodes over multiple wireless hops on a network [1]. Indeed, WLAN mesh networks consist of mesh point and mesh stations, where mesh point have minimal mobility and form the backbone of WLAN mesh network. They provide network access for both mesh and conventional stations. Compared with ad hoc nodes, which constitute mobile ad hoc networks, mesh point can be either stationary or minimal mobile, they also have a sufficient battery power and a powerful processing capacity. The integration of WLAN mesh networks with other networks such as the Internet, cellular, etc., can be accomplished through the gateway and bridging functions in the Mesh Point [2]. The standardization of WLAN Mesh network in IEEE 802.11s is work in progress. One of the key functionalities of IEEE 802.11s is the wireless multi-hop routing, which sets up the paths for the wireless forwarding. For that reason, efficient routing protocols have to provide paths through the wireless mesh and react to dynamic changes in the topology so that mesh nodes can communicate with each other even if they are not in direct wireless range. Mesh networks can use the ad hoc routing protocols such as OLSR and AODV. However, the quality of a WLAN mesh network depends on the quality of the wireless links, on interference and on the utilization ratio of radio resources. To reflect all of these conditions and to target a high network capacity, the Airtime Link Metric (ALM) was adopted as a default radio metric. IEEE 802.11s proposes two path selection protocols based on ALM : RM- AODV (Radio Metric Ad hoc On demand Distance Vector) and RA-OLSR ( Radio-Aware Optimized Link State Routing). We note here that IEEE 802.11s adopts the Hybrid Wireless Mesh Protocol (HWMP), which incorporates RM-AODV with a function added for establishing tree-based routes. In this paper, we present RM-AODV and RA-OLSR, we evaluate their performance and we compare them with hop count routing protocols. The remainder of the paper is structured as follows. Section 2 gives a brief overview of IEEE 802.11s future standard. Path selection protocols RM-AODV and RA-OLSR are explained in section 3. Section 4 presents simulation results and compares the proposed path selection protocols. II. THE IEEE 802.11S STANDARD The IEEE 802.11s working group specifies an extension to the IEEE 802.11 MAC to solve the interoperability problem by defining an architecture and protocol that support both broadcast/multicast and unicast delivery using ” radio-aware” metrics over self-configuring multi-hop topologies [1]. The IEEE 802.11s WLAN mesh network architecture is composed of (Fig. 1) [3]: • MP (Mesh Point): is a dedicated node for forwarding packets on behalf of other MP that may not be within direct wireless transmission range of their destinations. • Mesh Access Point (MAP): is a particular MP that provides the network access to the clients or stations. • MPP (Mesh Portal Point): is a particular MP that acts as a bridge to access external networks like Internet. • STA (Station): connected via a MAP to the mesh net- work. Each network uses a single method to determine paths through the Mesh. The standard includes a default mandatory path selection protocol RM-AODV to ensure interoperability and an optionnal routing protocol called RA-OLSR. Moreover, 978-1-4244-2829-8/08/$25.00 ©2008 IEEE