Object tracking is one of the killer applications for wireless sensor networks (WSN) in which the network of wireless sensors is assigned the task of tracking a particular object. The network employs the object tracking techniques to continuously report the position of the object in terms of Cartesian coordinates to a sink node or to a central base station. A family tree of object tracking techniques has been prepared.In this paper we have summarized the object tracking techniques available so far in wireless sensor networks

Cloud computing and Web-based applications are creating a need for powerful data centers. Data centers have a great need for high bandwidth, low latency, low blocking probability, and low bit-error rate to sustain the interaction between different applications. Current data center networks (DCNs) suffer from several problems such as high-energy consumption, high latency, fixed throughput of links, and limited reconfigurability. Electronic switches are low radix and have high latency due to a large hop count since each hop employs a store-and-forward mechanism. Optical interconnects, on the other hand, offer several advantages such as low-energy consumption, high bandwidth, reconfigurability, malleability to changing traffic, high-radix switch design, fast switching transition times, and wavelength multiplexing. These benefits provide the incentive to shift from electrical interconnects to optical interconnects in DCNs. Despite several advantages over their electrical counterparts, the performance of optical interconnects can be further improved by considering some performance parameters of optical interconnects. One such important parameter for the performance of any communication network is the blocking probability. This paper makes a comprehensive investigation of the performance of optical interconnects in different DCN B Mohsin Fayyaz architectures on the basis of blocking probability and concludes by suggesting ways to reduce the blocking.

To support cloud services, Data Centre Networks (DCNs) are constructed to have many servers and network devices, thus increasing the routing complexity and energy consumption of the DCN. The introduction of optical technology in DCNs gives several benefits related to routing control and energy efficiency. This paper presents a novel Packet Classification based Optical interconnect (PCOI) architecture for DCN which simplifies the routing process by classifying the packet at the sender rack and reduces energy consumption by utilizing the passive optical components. This architecture brings some key benefits to optical interconnects in DCNs which include (i) routing simplicity, (ii) reduced energy consumption, (iii) scalability to large port count, (iv) packet loss avoidance, and (v) all-to-one communication support. The packets are classified based on destination rack and are arranged in the input queues. This paper presents the input and output queuing analysis of the PCOI architecture in terms of mathematical analysis, the TCP simulation in NS2, and the physical layer analysis by conducting simulation in OptiSystem. The packet loss in the PCOI has been avoided by adopting the input and output queuing model. The output queue of PCOI architecture represents an M/D/32 queue. The simulation results show that PCOI achieved a significant improvement in terms of throughput and low end-to-end delay. The eye-diagram results show that a good quality optical signal is received at the output, showing a very low Bit Error Rate (BER).

Summary Real time cloud computing applications require a low latency network. The latency of optical interconnect in Data Center Networks (DCNs) is dependent on the complexity of the routing algorithm. The routing algorithm makes decisions about the forwarding of a packet on each successive node. If a routing algorithm is more complex, it requires more hardware resources to implement, which incurs extra cost and latency to the optical interconnect. This paper analyzes the complexity of existing architectures for the first time by showing Big O notation of complexity for each architecture. Different factors affecting the computational complexity of any routing algorithm are identified. This paper proposes a new architecture named VLCC. It has very low fixed routing complexity irrespective of network size. It has no packet loss at the network layer under many to many and all to one communication pattern. The only packet loss is at the physical layer due to signal degradation caused by optical components. The level of signal degradation is analyzed in terms of received signal power, bit error rate (BER), receiver sensitivity, path loss, and blocking probability. VLCC architecture is highly suitable for real time applications that require deterministic quality of service (QoS), where network performance is not affected by the traffic pattern.

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