On channel assignment and multicast routing in multi-channel multi-radio wireless mesh networks

Multicast is a key networking service, enabling one-shot delivery of information from a source to multiple destinations and is considered underlying for collaborating multimedia applications such as video conferencing, distance learning and other forms of content distributing over Multi-Channel Multi-Radio Wireless Mesh Networks (MCMR WMNs). Multicast protocol as designed in these networks, however, is tightly coupled with the specifi cs of the nodes’ channel-radio associations to realise minimum interference communication. The mainstream of research in WMN multicasting is oriented towards heuristic or meta-heuristic strategies which basically take on a sequential approach to solve the channel assignment and the multicast routing as two disjoint sub-problems. The resulting network confi gurations would be sub-optimal in this case. It is given that the cross-interaction between the two sub-problems is an effect of the problem’s specifi cations. In this paper, fi rst, we propose a cross-layer mathematical formulation of joint channel assignment and multicast tree construction in MCMR WMNs, which, opposed to the existing schemes guarantees optimal solution. The simulation results demonstrate that our cross-layer design outperforms the Level Channel Assignment (LCA), Multi-Channel Multicast (MCM), the Genetic Algorithm (GA), Simulated Annealing (SA) and the Tabu Search (TS)-based methods proposed by Zeng et al. (2010) and Cheng et al. (2011) respectively, in terms of inter-channel interference. Second, since joint optimisation modelling has been relatively demanding in terms of complexity, we relax the optimality requirement and alternatively explore the option of a layered formulation in which to ensure an optimal solution for each sub-problem. Our alternative design is proved superior to the prior art in terms of interference minimisation too. We conduct an extensive series of simulations to analyse the optimality and complexity of our two design strategies. The overall result of the interference, is our optimality measurement. Also, complexity is evaluated in terms of the memory consumption as well as the required time to solve the multicast problem. Keyword: WMN; wireless mesh network; multi-channel; multi-radio; channel assignment; multicast tree construction; cross-layer design; BIP; binary integer programming. Reference to this paper should be made as follows: Jahanshahi, M., Dehghan, M. and. Meybodi, M.R. (xxxx) ‘On channel assignment and multicast routing in Multi-Channel MultiRadio Wireless Mesh Networks’, Int. J. Ad Hoc and Ubiquitous Computing, Vol. x, No. x, pp.xxx–xxx. Biographical notes: Mohsen Jahanshahi completed his BS and MS in Computer Engineering in Iran in 2002 and 2005, respectively. He also achieved a PhD in Computer Engineering from the Islamic Azad University (Tehran Science and Research Branch) in 2011. He joined the faculty of the Computer Engineering Department at Islamic Azad University (Central Tehran Branch) in 2006. His research interests include wireless mesh networks, wireless sensor networks, cognitive networks, mathematical optimisation, learning systems and soft computing. 2 M. Jahanshahi et al. Protocol model (Gupta and Kumar, 2000; Kodialam and Nandagopal, 2005; Hossain and Leung, 2008), which is also the interference model underlying the formulation presented in this paper, minimising the number of interfering links in a wireless mesh network would have a direct impact on throughput maximisation, as also corroborated in Zeng et al. (2007, 2010) and Cheng and Yang (2011). Clearly, multicast routing in WMNs not only the best routing tree’s establishment requires but we also need to assign proper channels to its links. In MCMR WMNs, interference minimisation is normally tackled by devising channel assignment schemes in the MAC layer. Effi cient channel-radio associations often come at the expense of satisfying more complex connectivity constraints; in particular, for two nodes to be connected, not only should they be within transmission radius of one another, but also that the same channel should be assigned to their radios. Multicast routing, under this additional constraint, is even more complicated, since the multicast tree now has to be constructed for the channel-radio association, which also minimises inter-channel interference. Despite its vast number of applications and practical importance, few works have specifi cally been targeted at multicast performance optimisation in MCMR WMNs. The mainstream of research in this area has considered channel assignment and multicast routing as two disjoint sub-problems to be solved in sequence (Zeng et al., 2007, 2010; Cheng and Yang, 2008a, 2008b, 2011; Lim et al., 2009), as envisaged in Nguyen and Nguyen (2008, 2009a, 2009b) and Yin et al. (2007), it might even be the case that the solution for either one of these two sub-problems is assumed to be previously calculated and given as input to the other. The downside associated with these schemes, however, is that the cross-interaction between the two sub-problems would not be accounted for and that their reliance on heuristic or meta-heuristic initiatives does not come up with the optimal solution. Networking problems are ideally formulated in mathematical terms so that the resulting confi gurations