Nurul Mu'azzah Abdul Latiff

Proactive integrated handoff management in cognitive radio mobile ad hoc networks

In cognitive radio networks, the secondary users (SUs) switch the data transmission to another empty spectrum band to give priority to primary users (PUs). In this paper, channel switching in cognitive radio mobile ad hoc networks (CR-MANETs) through an established route is modeled. The probability of channel availability in this route is calculated based on the PUs activity, SUs mobility, and channel heterogeneity. Based on the proposed model, the channel and link availability time are predicted. These predictions are used for channel assignment in the proposed channel allocation scheme. A handoff threshold as well as a life time threshold is used in order to reduce the handoff delay and the number of channel handoffs originating from the short channel usage time. When the channel handoff cannot be done due to the SUs mobility, the local flow handoff is performed to find an appropriate node in the vicinity of a potential link breakage and transfer the current data flow to it. The local flow handoff is performed to avoid possible flow disruption and also to reduce the delay caused by the link breakage. The study reveals that the channel heterogeneity and SUs mobility must be considered as important factors, which affect the performance of the handoff management in the CR-MANETs. The results emphasize on the improvement of the route maintenance probability after using the local flow handoff. It is also stated that the amounts of handoff requirement and handoff delay are decreased after using the predicted channel usage life time and handoff threshold time.

Prolonging lifetime of wireless sensor networks with mobile base station using particle swarm optimization

Wireless sensor networks are a family of networks in wireless communication system and have the potential to become significant subsystem of engineering applications. In view of the fact that the sensor nodes in wireless sensor networks are typically irreplaceable, this type of network should operate with minimum possible energy in order to improve overall energy efficiency. Therefore, the protocols and algorithms developed for sensor networks must incorporate energy consumption as the highest priority optimization goal. Since the base station in sensor networks is usually a node with high processing power, high storage capacity and the battery used can be rechargeable, the base station can be utilized to collect data from each sensor node in the sensing area by moving closer to the transmitting node. In this paper, we proposed an energy-efficient protocol for the movement of mobile base station using particle swarm optimization (PSO) method in wireless sensor networks. Simulation results demonstrate that the proposed protocol can improve the network lifetime, data delivery and energy consumption compared to existing energy-efficient protocols developed for this network.

Adaptive transport layer protocol for highly dynamic environment

Computer and wireless communication require Internet accessibility at anytime and anywhere; this includes in a high-speed mobile station such as in speedy trains, fast moving cars as vehicle-to-infrastructure communication. However, wireless Quality of Service (QoS) provisioning in such an environment is more challenging. This increased the development of numerous schemes concerning the need of smooth handover of the mobile nodes. Conversely, transport layer (L4 in ISO layers) protocols such as stream control transmission protocol can support such a seamless handover in high-speed mobility users. This article highlights on the issues of moving users in mobile WiMAX networks. An adaptation of transport layer protocol of the high mobility vehicle that supports seamless handover can guarantee and maintain QoS for rapid handover rates. The results show an improvement of L4 protocol in terms of delay time and throughput in order to enable efficient and robust mobility aware protocols.

Reconfiguring Software Defined Radio platform for Dynamic Spectrum Access

Traditional static spectrum allocation policy has resulted in current day spectrum scarcity and inefficient spectrum utilization. Dynamic Spectrum Access (DSA) technique allows cognitive (unlicensed) user (CU) to opportunistically transmit in a primary (licensed) user (PU) frequency band for a given time if it does not detect any ongoing operations. In this work, CU is implemented on Software Defined Radio (SDR) platform consisting of GNU Radio and USRP. This platform is then reconfigured for DSA based on Cognitive Radio (CR) technology which features include abilities to sense, learn, adapt and react according to the environment. The proposed design of the DSA based CR system consists of four main functional blocks: spectrum sensing, spectrum management, spectrum decision and data transmission. In this paper, we address the implementation of DSA based CR on IEEE802.15.4 standard. The result shows a significant improvement in term of Packet Reception Rate (PRR) for CU with DSA based CR system compared to the system without DSA capability.

Locating Optimum Receiver Position in Seismic Acquisition: Example from Carbonate Region

The existence of carbonate pinnacle disrupts the propagation of seismic wave from source to receivers, thus creating un-illuminated reflectors image. In previous years, several methods have been studied and applied in order to improve the subsurface data by restoring true reflectivity, with certain degrees of success. We can improve the seismic images in hand either by the implementation of complex migration algorithm or by conducting a fresh seismic data acquisition within the affected region. Following the seismic value chain, we can easily analyse the quality of the seismic images before any new acquisition took place through the forward modelling procedure using synthetic data for illumination analysis. In current illumination procedure, the required inputs are velocity model, acquisition set-up and the wave propagation. Although velocity information and wave propagation parameters are generally consistent within a basin, the seismic acquisition set-up needs to be revolutionized in order to bring a higher subsurface illumination. In this work, we proposed an optimum receiver position by using the particle swarm optimization approach, for better seismic images in carbonate-affected region.

Modelling of routing and spectrum handoff in CR-MANETs

There is an extensive research interest in cognitive radio mobile ad hoc networks (CR-MANETs) to improve the spectrum efficiency by developing innovative design techniques through various layers of the protocol stacks. This paper presents the optimisation of CR-MANETs by exploiting the efficient usage of the available wireless spectrum through a framework for spectrum-aware handoff. In this paper, the concept of integrated handoff management in CR-MANETs is considered. An analytical model for a spectrum handoff scheme is introduced based on spectrum mobility in which secondary users (SUs) will move to another unused spectrum band, giving priority to a Primary User (PU), while satisfying its communication quality of service (QoS). The main contribution is using the Markov chain to model the evolution of the network (node position, node speed, channel quality, etc.) and to propose the combined spectrum handoff and routing. The performance of the network is analyzed based on the Markov chain. The comparison results from both analytical modelling and simulation clearly show an improvement in the performance of the SU network in terms of the route maintenance probability and the SU throughput. It is also proved that not only the PU activity affects the performance of the handoff management scheme but also the channel transmission range and the node mobility have a significant effect on the performance of the management scheme.

Optimizing Distributed Cooperative Sensing Performance Using Swarm Intelligence

Cognitive radio (CR) technology offers attractive solution to overcome spectrum scarcity problem and improve spectrum utilization. Opportunistic spectrum access concept adopted by a CR network allows unlicensed or cognitive users (CUs) to access a frequency band that is not in use by the licensed or primary users (PUs). In enabling such spectrum-aware communication protocol, spectrum sensing becomes the fundamental requirement to exploit the unused spectrum and effectively protect the quality of service (QoS) of PUs. An increase in sensing time results in a higher detection probability (P d ) and lower false alarm probability (P f ), which leads to better protection of the primary users from harmful interference in addition to improved utilization of the available unused spectrum. However, this will reduce the amount of time for data transmission and hence, affects the achievable throughput of CUs. In this paper, this sensing-throughput tradeoff is addressed in terms of distributed approach of cooperative channel sensing. In order to find the optimal sensing time that maximizes the throughput of an OSA based CR network, the decision fusion scheme of OR rule are subjected to particle swarm optimization (PSO). The results show that a lower sensing time is achieved under PSO based cooperative sensing. The maximum achievable normalized throughput also increases with the increase of sensing terminals under optimal fusion scheme compared to normal fusion technique.