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TopThe path selection problem for mobile stations has been discussed in different documents belonging to the IEEE 802.16’s relay task group and 3GPP LTE-Advanced. Multi-hop routing protocols using different cost metrics have been also proposed in several contributions (e.g., Perkins & Bhaguat, 1994; Perkins & Royer, 1999; Cao et al., 2008; Lee et al., 2009), such as shortest-path routing, load-aware routing, SINR-based selection or throughput-based selection.
Shortest-path routing: This routing algorithm described in Perkins and Bhaguat 91994) and Perkins and Royer (1999) aims at finding the route with the minimum hop count value. It assigns a path with the least number of hop-counts to a Mobile Station (MS); it has been widely used in both wired and wireless networks. The most important feature of the shortest path is that it usually has the minimum communication delay and is easily implemented. However, the use of the minimum hop count for path cost is not always perfect. Many researches show that this kind of protocols degrades network performance due to congestion on these selected relays along the minimum hop path (Bharadwaj et al., 2011).
Load-aware routing: The load-aware routing protocols is presented in Lee and Gerla (2001) and Cao et al. (2008); this protocol aims at discovering routes with the minimum traffic load. It selects the path that cumulates the least consumption. These load-aware routing protocols use different cost metrics to measure traffic load of a route. For example, they used the number of packets buffered at intermediate relays along the route as a route selection metric. Thus, load-aware routing protocols can avoid congestion by denying access to relays with high traffic load. Considering the path selection on the basis of a minimum load, may however not be very efficient. In fact, this selection can add more delays and does not guarantee high data rate, especially when the user is located at an important distance from the selected relays.