The tremendous development in wireless technologies and multimedia applications persuaded upsurge in spectrum utilization in the past. One of the adequate clarifications to overwhelm this limitation is by using Cognitive Radios (CR). These networks are likely to boost spectrum consumption professionally by permitting Secondary Users (SUs) to take advantage of the use of the approved spectrum of primary users (PUs). CR is a kind of a sensible radio that can sense the extraneous surroundings, analyze the past and build perspicacious conclusions to switch its transmission factors in step with the current state of the atmosphere. An Ad-hoc Network engaging Cognitive Radios (CR) can often be termed as Cognitive Radio Adhoc Network (CRAHN). Routing in CRAHN

This article presents a framework for performance comparison between Long Term Evolution (LTE) and WiMAX technologies, depended on link level simulation, under different conditions (e.g. a mixture of channel models and modulation coding schemes (MCS)). Two performance metrics have been used: throughput against SNR for both downlink (DL) and uplink (UL) and block error rate (BLER) against SNR for both DL and UL. Simulation results, conducted in network simulator OPNET Modeler ver. 17.1, show that the throughput and the BLER increases as the MCS increase (i.e. MCS=5, 15, 24).

The Ad-hoc On Demand Distance Vector (AODV) is one of the most famed reactive routing protocols, which is used in Mobile Ad Hoc Networks (MANETs) for routing purposes, where the routes are built only when it is required. The AODV is related to the problem of route constructing and maintaining among any two-node in the presence of the dynamic topology of a network. High routing control packets, during route construction, is a limiting factor of AODV. Also, the route created during route discovery process may not be optimum (in terms of the number of hop counts between the originating and target node). The construction of non-optimal route arises from many reasons such as temporary congestion of one or more links in the short path to the target node, or nodes in those paths may contend the channel late, or the nodes may be busy for that moment to entertain other engagement. Moreover, during the route discovery phase, a large amount of unnecessary control packets may be generated which result in the debasement of the performance and the efficiency of the protocol by congesting the network and increasing the overhead. In this article the cases at which non-ideal routes are created and unimportant control packets generated during route discovery process will be identified. The modified AODV (AODV_MOD) with enhanced route discovery mechanism is proposed that will be used to avoid these cases by suppressing unimportant control packets and avoiding non-ideal routes formation. Simulation results, conducted in network simulator (NS2), prove the skillfulness of the proposed enhanced route discovery scheme from point of view of packet delivery ratio, endto-end delay, and normalized overhead.