Optimizing Network Layer with Adaptive Modulation for Time Varying Channel

A finite group of nodes placed in the network layer for inter process communication has to guarantee specified performance measures like high throughput, low jitter, avoid contention, etc. At present, the data security is taken care by the upper layer i.e. Transport (TCP/IP) to some extent and the network layer has to simply deliver the packets in an optimal manner. The security now offered by the TCP/IP layer is in the form of retransmission for the corrupt packet(s). If the channel conditions are not good, then repeated retransmission requests, can lower the throughput, increase the jitter and render the network less useful. Hence, to ensure uniform SNR in each of the link, it is necessary to place critical design issues intrinsically in the individual nodes. This includes, for example, that, each node can autonomously detect the modulation and demodulate among a group set, and thereby support dynamic/adaptive modulation capability. This can enable the node to alter the modulation to maintain a uniform SNR and reduce the outage probability. Additionally, the communication strategy need to look for the shortest path, identify the channel support in that path and choose the best modulation based on shortest path algorithm. In this context, in this paper, each node is provided with the capability to perform (a) Autonomous Modulation (to maintain uniform SNR) (b) Switch to the corresponding demodulator and get the packet (reduces contention) and (c) route the packets to the next intended node through the shortest path (reduces jitter). This process is recursively done at every node as and when they receive the data. The metrics studied include the network layer metrics, wireless channel related metrics, modulation based aspects etc.