The cross layer based reliable routing algorithm, is designed using the metric from the physical layer, data link layer and transferring it to the network layer to make the routing decisions. This algorithm involves the mobile node cooperatively to establish the route and introduces the radio link stability with extensive cross layer cooperation to establish reliable and stable routes. We have developed this algorithm by modifying the underlying principle of dynamic source routing protocol. Dynamic source routing is known for its benefits of routing in multiple paths avoiding the overhead of new route discovery whenever the route in use breaks [10. Hang Shen et.al, 2008]. The route discovery and route maintenance easily support uni-directional links and asymmetric routes. DSR is also compatible for internetworking routing consisting of different types of network. The only drawback of DSR could be reported as its performance is not par with other reactive routing protocols in a high mobility environment. Another reason for selecting DSR as base protocol, is much of researches done on cross layer design protocol is discussed with AODV, and minimal work is on with DSR.
Our cross layer, dynamic source routing (CL-DSR) has had two phases Route Discovery and Route Maintenance. Figure 2 represents the architecture of the proposed algorithm.
The cross layer metrics discussed in the literature focus on the link lifetime based on received signal strength, distance between the nodes, the number of damaged received packets which are contributed by SNR (Signal to noise ratio). In reality fading effects due to mobility and multipath propagation also affects the transmission and cause fluctuation of signal strength leading to breakage of an active link [12.Justus Ch. Fricke, et.al, 2007] Forward Error Correction (FEC) channel coding is used in digital transmission system for error correcting provides reliable information that can be retrieved from the soft outputs of the channel decoder. Figure 3 depicts the transfer of required data to compute the metric to establish the route. In our approach of cross layer design along with link SNR, fading effect and FEC role is also accounted to find a stable routes.
Route discovery in CL-DSR
Route discovery consists of link metric computations to decide on the stability, quality of the link to prioritize the route. The components of the link metric is the link instability index contributed by the average bit error probability from the soft output decoder and path loss from the received signal strength.
Similar to DSR, the route discovery is initiated by the source only when it has to send data packets to the destination. The source node broadcasts a RREQ packet to its neighboring nodes. The receiving nodes of the RREQ packet will update the RREQ packet with its ID, next hop and link metric computed based on the CL-DSR rules. At the destination node populates its RREP packet with both metric and...