Carlene E.-A. Campbell

A combinatorial optimization algorithm for multiple cloud service composition

Display Omitted The COM2 algorithm efficiently considers multiple clouds while composing services.The proposed algorithm successfully competes with previous algorithms.Low examined service number is achieved without impacting the combined cloud number. Service composition is an evolving approach that increases the number of applications of cloud computing by reusing existing services. However, the available methods focus on generating composite services from a single cloud, which limits the benefits that are derived from other clouds. This paper proposes a novel COMbinatorial optimization algorithm for cloud service COMposition (COM2) that can efficiently utilize multiple clouds. The proposed algorithm ensures that the cloud with the maximum number of services will always be selected before other clouds, which increases the possibility of fulfilling service requests with minimal overhead. The experimental results demonstrate that the COM2 successfully competes with previous multiple cloud service composition algorithms by examining a small number of services-which directly relates to execution time-without compromising the number of combined clouds.

Multi-Channel Multi-Radio Using 802.11 Based Media Access for Sink Nodes in Wireless Sensor Networks

The next generation surveillance and multimedia systems will become increasingly deployed as wireless sensor networks in order to monitor parks, public places and for business usage. The convergence of data and telecommunication over IP-based networks has paved the way for wireless networks. Functions are becoming more intertwined by the compelling force of innovation and technology. For example, many closed-circuit TV premises surveillance systems now rely on transmitting their images and data over IP networks instead of standalone video circuits. These systems will increase their reliability in the future on wireless networks and on IEEE 802.11 networks. However, due to limited non-overlapping channels, delay, and congestion there will be problems at sink nodes. In this paper we provide necessary conditions to verify the feasibility of round robin technique in these networks at the sink nodes by using a technique to regulate multi-radio multichannel assignment. We demonstrate through simulations that dynamic channel assignment scheme using multi-radio, and multichannel configuration at a single sink node can perform close to optimal on the average while multiple sink node assignment also performs well. The methods proposed in this paper can be a valuable tool for network designers in planning network deployment and for optimizing different performance objectives.

Multi-Channel Distributed Coordinated Function over Single Radio in Wireless Sensor Networks

Multi-channel assignments are becoming the solution of choice to improve performance in single radio for wireless networks. Multi-channel allows wireless networks to assign different channels to different nodes in real-time transmission. In this paper, we propose a new approach, Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks (WSNs) over 802.11 networks. We presented simulation experiments in order to investigate the characteristics of multi-channel communication in wireless sensor networks using an NS2 platform. Nodes only use a single radio and perform channel switching only after specified threshold is reached. Single radio can only work on one channel at any given time. All nodes initiate constant bit rate streams towards the receiving nodes. In this work, we studied the impact of non-overlapping channels in the 2.4 frequency band on: constant bit rate (CBR) streams, node density, source nodes sending data directly to sink and signal strength by varying distances between the sensor nodes and operating frequencies of the radios with different data rates. We showed that multi-channel enhancement using our proposed algorithm provides significant improvement in terms of throughput, packet delivery ratio and delay. This technique can be considered for WSNs future use in 802.11 networks especially when the IEEE 802.11n becomes popular thereby may prevent the 802.15.4 network from operating effectively in the 2.4 GHz frequency band.

A new MAC solution for multi-channel single radio in wireless sensor networks

Wireless communication has become the fastest growing area in the communication industry. The demand for using this medium ranges from security, military, Internet and scientific purposes and are rapidly replacing wire-line systems in many developing countries. Wireless Sensor Networks (WSN) is currently a research area that is being studied by many researchers and industries within the wireless communication arena. It is not only being considered for use for target detection, environmental monitoring and tactical systems, but is also a promising technology for use in multimedia systems such as streaming video and surveillance. The use of multichannel assignment can substantially improve the performance of WSNs using the IEEE specifications of non-overlapping channels simultaneously. The 802.11 multichannel Medium Access Control (MAC) schemes do not efficiently utilize this technology owing to the overhead caused by channel assignments. In this paper a new approach is used by applying multichannel to reduce the waiting time of a node when attempting to access a busy medium. The back-off algorithm will switch channel when the contention window of the Distributed Coordination Function (DCF) has reach an assigned threshold. The sink node will perform interface switching to receive data from channels coming from source nodes.