Trust-Assisted Handover Approach in Hybrid Wireless Networks

In Next-Generation (NG) hybrid wireless networks, Mobile-Controlled Handover (MCHO) is expected to be employed as the handover control mechanism, in contrast to Network-Controlled Handover (NCHO) used in homogeneous wireless networks. As more independent network operators get involved in providing Internet access, roaming mobile users would have to deal with complex trust relationships between heterogeneous network domains. The state-of-the-art handover approaches just take into account Quality of Service (QoS), but ignore the complexities arising from the coexistence of multiple network operators in the NG networks. The existence of a complex trust relationship between networks may lead to unnecessary handover attempts in service roaming. In this regard, this paper introduces a novel approach of dynamically retrieving network trust information, and using it in MCHO. We show how network trust information can be utilised to obtain a 35% reduction in handover delay, meanwhile retain QoS in a handover. The proposed scheme does not need bulk storage in mobile handsets, and can react to changes to network topology and trust relationships dynamically. Analytical results are provided to demonstrate how roaming mobile users make more intelligent and reliable handover if implementing the proposed handover approach in a multi-operator and multi-technology environment.     

Cross-layer speculative architecture for end systems and gateways in computer networks with lossy links

The throughput degradation of Transport Control Protocol (TCP)/Internet Protocol (IP) networks over lossy links due to the coexistence of congestion losses and link corruption losses is very similar to the degradation of processor performance (i.e., cycle per instruction) due to control hazards in computer design. First, two types of loss events in networks with lossy links are analogous to two possibilities of a branching result in computers (taken vs. not taken). Secondly, both problems result in performance degradations in their applications, i.e., penalties (in clock cycles) in a processor, and throughput degradation (in bits per second) in a TCP/IP network. This has motivated us to apply speculative techniques (i.e., speculating on the outcome of branch predictions), used to overcome control dependencies in a processor, for throughput improvements when lossy links are involved in TCP/IP connections. The objective of this paper is to propose a cross-layer network architecture to improve the network throughput over lossy links. The system consists of protocol-level speculation based algorithms at transport layer, and protocol enhancements at middleware and network layers that provide control and performance parameters to transport layer functions. Simulation results show that, compared with prior research, our proposed system is effective in improving network throughput over lossy links, capable of handling incorrect speculations, fair for other competing flows, backward compatible with legacy networks, and relatively easy to implement.     

The future of security in Wireless Multimedia Sensor Networks

This is a position paper on our views on security aspects of Wireless Multimedia Sensor Networks (Secure WMSNs). It is meant to serve as a brief survey. But, more importantly, it gives a perspective on how we foresee the future of this research area, its main challenges, and its future trends. We believe that this paper will spur new discussions and research ideas among the researchers from both the industry and the academic world.     

Video Streaming with Network Coding

Recent years have witnessed an explosive growth in multimedia streaming applications over the Internet. Notably, Content Delivery Networks (CDN) and Peer-to-Peer (P2P) networks have emerged as two effective paradigms for delivering multimedia contents over the Internet. One salient feature shared between these two networks is the inherent support for path diversity streaming where a receiver receives multiple streams simultaneously on different network paths as a result of having multiple senders. In this paper, we propose a network coding framework for efficient video streaming in CDNs and P2P networks in which, multiple servers/peers are employed to simultaneously stream a video to a single receiver. We show that network coding techniques can (a) eliminate the need for tight synchronization between the senders, (b) be integrated easily with TCP, and (c) reduce server’s storage in CDN settings. Importantly, we propose the Hierarchical Network Coding (HNC) technique to be used with scalable video bit stream to combat bandwidth fluctuation on the Internet. Simulations demonstrate that under certain scenarios, our proposed network coding techniques can result in bandwidth saving up to 60% over the traditional schemes.     

Traffic grooming,routing, and wavelength assignment in an optical WDM mesh networks based on clique partitioning

In wavelength routed optical networks, the number of wavelength channels is limited due to several constraints and each wavelength as well as each lightpath support traffic in the Gbps range. On the other hand, the traffic requested by an individual connection is still in the Mbps range. Therefore, to utilize the network resources (such as bandwidth and transceivers) effectively, several low-speed traffic streams have to be efficiently groomed or multiplexed into one or more high-speed lightpaths. The grooming problem of a static demand is considered as an optimization problem. In this work, we have investigated the traffic grooming problem with the objective of maximizing the network throughput for wavelength-routed mesh networks and map this problem to the clique partitioning problem. We have proposed an algorithm to handle general multi-hop static traffic grooming based on the clique partitioning concept. The efficiency of our approach has been established through extensive simulation on different sets of traffic demands with different bandwidth granularities for different network topologies and compared the approach with existing algorithms.     

Design and Preliminary Experiment of 35 GHz Pulsed Extended Interaction Oscillator with Folded Waveguide

In this paper a 35 GHz pulsed extended interaction oscillator (EIO) was studied, with high current density electron gun based cylindrical and parallel shaped diode. The folded waveguide was employed as the slow wave structure (SWS) of the EIO. The transferring waveguide, electron gun and the EIO tube were designed and the corresponding testes have been finished, including the transmission characteristic of the SWS, the emitting ability of the electron gun and the performance of the EIO tube. Preliminary experiment results show that the pulsed power and the exciting frequency are about 150 W and 35 GHz, respectively, under conditions of the B_z 0.4 T, the high voltage 17 kV and the high current density 26 A/cm².     

Requirements for enforcing digital rights management in multicast content distribution

In this paper, we have collected the requirements for Digital Rights Management from various sources, and presented them as a set of 11 requirements, associated with five categories. We discuss each requirement, provide the motivation for each entry, and illustrate how each one could be achieved. Four example commercial DRM systems are briefly explained, and the requirements that they meet are presented in tabular format. None of the example systems meet all the requirements that we have listed. The security threats that are faced by DRM systems are briefly discussed. All of the example systems are based on unicast data distribution. The use of multicast data distribution can help the source of the data and the underlying network to reduce their resource requirements when distributing high-quality content at minimum cost and delay. Up to now, there has been little motivation to use standard Internet Protocol multicast because it does not support any protection mechanisms for the delivered data. Given that significant progress has been made by other researchers in providing “secure” multicast data distribution, we explore how the use of secure multicast as a distribution technology can bring significant improvement for some requirements, while making the achievement of others more difficult. We review how the architecture of the distribution must change to permit capturing the advantages of multicast distribution while retaining as much as possible the features of unicast systems. Some open problems are identified.     

A 12-bit 0.35 μm CMOS area optimized current-steering hybrid DAC

In this paper a 12-bit current-steering hybrid DAC is implemented using AMS 0.35 μm CMOS process technology. The architecture and design methodology used for the implementation of the DAC offer advantages like design speed up, easiness in design and a small active area. The proposed hybrid DAC consists of four 3-bit parallel matched current-steering subDACs and resistive networks that properly weight the current output of each subDAC to obtain the overall voltage-mode output of the 12-bit hybrid DAC. The performance of the hybrid DAC is validated through static and dynamic performance metrics. Simulations indicate that the DAC has an accuracy of 12-bit and a SFDR higher than 66 dB in whole Nyquist frequency band. The simulated INL is better than 1 LSB, while simulated DNL is better than 0.25 LSB. At an update rate of 250 MS/s the SFDR for signals up to 10 MHz is higher than 66 dB. The Figure of Merit (FoM) of the implemented hybrid DAC is better than recently presented DACs with 12-bit resolutions and implemented using various process technologies. The proposed hybrid DAC supporting high update rates with good dynamic performance can be used as an alternative in various applications in industry including video, digital TV, cable modems etc.     

Detailed Analysis of Temperature Characteristics of an InGaP/InGaAs/Ge Triple-Junction Solar Cell

Temperature characteristics of an InGaP/InGaAs/Ge triple-junction solar cell were analyzed in detail using an equivalent circuit calculation. The current–voltage (I–V) characteristics of single-junction solar cells (InGaP, InGaAs, Ge solar cells) were measured at various temperatures. Fitting of I–V curves between measured and calculated data was carried out, and the diode parameters and temperature exponents of the single-junction solar cells were extracted. The parameters for each single-junction solar cell were used in the equivalent circuit model for the triple-junction solar cell, and calculations of solar cell performance were carried out. Measured and calculated results of the I–V characteristics at various temperatures agreed well.     

Electrical Properties of Ca<Subscript>9</Subscript>ZnLi(PO<Subscript>4</Subscript>)<Subscript>7</Subscript> Ceramics Prepared by Reactive Pressureless Sintering

Well-crystallized Ca₉ZnLi(PO₄)₇ ceramics were prepared by reactive pressureless sintering at atmospheric pressure. The single-phase Ca₉ZnLi(PO₄)₇ ceramics were confirmed by x-ray diffraction (XRD). The dielectric and electrical properties were investigated over a wide frequency range (1 Hz to 1 MHz) by complex impedance spectroscopy at different temperatures between 25°C and 600°C. A dielectric anomaly was observed at 440°C, which might be related to the phase transition. The impedance Cole–Cole plot was used to analyze the results of complex impedance measurements, revealing that the electrical properties depend strongly on frequency and temperature. Two relaxation dispersions of the electrical parameters were found and analyzed in terms of bulk and grain-boundary ionic transfer processes. The slope of the alternating-current (AC) conductivity over a wide range of temperatures provides activation energies from 0.48 eV to 1.69 eV. These results suggest that the conduction process is of the mixed type.