Common Control Channel Based MAC And Routing Protocol Design For Cognitive Radio Ad Hoc Networks

Natural available spectrum is scarce and cost effective. In order to efficiently utilize the available spectrum, existing spectrum allocation and its management should be changed. To achieve this, dynamic spectrum access through software defined radio is proposed. Cognitive Radio (CR) is a special type of Software Defined Radio that can change its operating parameters (modulation, frequency and data rate) dynamically based on environmental conditions. To deploy cognitive radio in real networks, it is important to enhance the existing TCP/IP protocol stack to support dynamic spectrum access, spectrum mobility and SDR functionalities. To accomplish this, protocols in every layer of TCP/IP protocol stack should be modified or new protocols should be designed for cognitive radio deployment in existing traditional ad-hoc networks.State-of-the-art research in CR-MAC and routing protocols design CCC (Common Control Channel) with In-band or out-of-band overlay spectrum bands. With existing In-band, interference with respect to multi-channel hidden terminals (primary and secondary users) is not avoided due to per-hop and group CCC coverage. Moreover, channel rendezvous time will be very high for more number of PU channels which results in increased control overhead and reduced network throughput. On the other hand, existing out-of-band CCC is subject to intruder attacks that results in single point of network failure. Furthermore, out-of-band (2.4 GHz ISM) CCC can be saturated and have interference with other technologies like WI-FI, Bluetooth etc. This clearly shows that existing CR-MAC and routing protocols doesn't emphasize in-depth on CCC design for node synchronization (multi-channel hidden terminals), channel rendezvous delays, cognitive control message overhead, control channel saturation and intruder attacks which needs to explore significantly. This motivates us to design "low rate and hybrid CCC based MAC and routing protocols for cognitive radio ad-hoc networks" to overcome existing problems in current CCC based CR-MAC and routing protocols. This dissertation mainly focus on enhancing the link and network aggregate throughput by reducing link, end-to-end cognitive and control message delays at MAC and network layer. To resolve existing CCC design issues in CRAHNs, this dissertation propose two CCC based CR-MAC protocols at link level and two CCC based CR-routing protocols at network level.Firstly, low rate energy efficient CCC based routing protocol for cognitive radio ad-hoc networks is proposed. This is because existing cognitive routing protocols either use 2.4 GHz unlicensed dedicated common control channel (CCC) or licensed PU free CCC for channel-path selection and CR node co-ordination message exchange. With licensed CCC, end-to-end channel-path selection and CR node co-ordination time will be high due to sequential or group based CCC coverage whereas dedicated 2.4GHz unlicensed CCC is subject to saturation and interference with other services. Hence, there is a greater extent for 2.4 GHz CCC to be congested which increases link failures and routing control overhead that successively degrade the performance of routing protocol. Our proposed work make use of lower unlicensed spectrum band (902-928 MHz (USA) or 915-917 MHz ISM band (China)) as a low rate Ad-Hoc On Demand Distance Vector (AODV) common control channel for broadcasting route control(channel-path) and CR coordination messages which abbreviates hop count, link failures, routing overhead and end-to-end data transmission delay. With this, low rate CCC based AODV protocol selects energy efficient channel-route paths through reduced hop count and minimized cognitive control overhead. Experimental results show that performance of low rate CCC based AODV routing protocol outperforms when compared with existing In-band and out-band CCC based routing protocols.Secondly, hybrid CCC based CR-MAC protocol is proposed. This is because multi-channel hidden terminal due to imperfect node synchronization at Cognitive-MAC is one of the crucial problems in dynamic channel availability of Cognitive radio ad-hoc networks. Most state-of-the-art CR MAC protocols either use "In-band" or "Out-of-band" overlay based common control channel (CCC) design for network setup, CR co-ordination message exchange and CR node synchronization. With In-band CCC, neighbor discovery and network setup time will be very long especially whenever, available PU free spectrum channels are large in number. Moreover, multi-channel hidden terminal problem and node synchronization cannot be effectively resolved due to link based (sequence) and group based CCC design in opportunistic licensed spectrum bands. With out-of-band CCC, network setup with dedicated unlicensed control channel is relatively fast when compared with In-band technique. Subsequently, CR node synchronization problem will be reduced due to network-wide coordination (broadcast) without channel switching delay. But, out-of-band Common control channel is subject to saturation, intruder attacks and may have interference with other wireless services which will severely degrade the performance of CR networks. Even though channel saturation problem is solved with low rate out-of-band CCC design, it is still susceptible to intruder attacks and security depletion. To overcome this, hybrid CCC based MAC protocol is proposed to enhance the performance of the CR network with respect to CR node synchronization, multi-channel hidden terminal and network connectivity time. Experimental results show that the performance of proposed hybrid CCC based MAC protocol is out performed when compared with existing In-band CCC-MAC protocols with high number of PU free channels and saturated out-of band CCC-MAC protocols.Thirdly, energy efficient hybrid CCC based CR-MAC protocol with directional antenna for CRAHNs is proposed. This is because control message overhead and Common Control Channel (CCC) in Cognitive Radio-Medium Access Control (CR-MAC) protocol has direct impact on transmitter power consumption and link application throughput. Hence, design of CCC in CR-MAC plays a pivotal role in selecting energy efficient channel-path for enhanced throughput. With existing In-band, imperfect node synchronization due to per hop and group CCC coverage leads to increased power consumption for multi-channel hidden terminal packet drops and longer network access delays. On the other hand, global coverage with existing dedicated out-of-band CCC results in increased power consumption due to saturation and intruder attacks. To overcome existing problems, an energy efficient hybrid CCC based CR-MAC protocol with Omni-directional control and directional data transmission is proposed to reduce power consumption due to link access overhead, multi-channel hidden terminal, deafness and spectrum mobility. In this proposal, antenna index numbers through Global Positioning System (GPS) and Angle of Arrival (AoA) is used for directional data transmission, whereas hybrid CCC is used to avoid interference due to multi-channel hidden terminals. Experimental results briefly explains that the proposed hybrid CCC-CR-MAC with directional antennas has increased network throughput and reduced transmit power consumption when compared with existing In/out-of-band Omni-directional CCC-based CR-MAC protocols.Finally, hybrid CCC based AODV routing protocol with directional antenna is proposed. This is because end-to-end application throughput and node energy consumption at cognitive network layer is based on CCC characteristics and route control messages. Hence, new CCC based CR-AODV routing protocol is important in selecting energy efficient shortest end-to-end channel-path and reduce route control overhead. State-of-the-art routing protocols propose CCC design with In or Out-of-band overlay spectrum bands in Omni-directional mode. Per hop and group coverage with In-band CCC is subject to higher end-to-end channel switching delays and increased multi-channel hidden terminal packet drops. On the other hand, global coverage with out-of-band CCC leads to channel saturation and intruder attacks which results in increased node power consumption due to higher control overhead. To overcome this, we propose a hybrid CCC design for AODV routing protocol with Omni-directional control and directional data transmission that reduce end-to-end channel-route power consumption, avoid hidden terminal packet drop and minimize spectrum handover packet drops. Experimental results reveal that proposed hybrid CCC based AODV routing with directional data transmission has increased throughput, reduced power consumption and less control overhead when compared with existing In/Out-of-band Omni-directional based CR-routing protocols.