Cooperative energy management in distributed wireless real-time systems

This work is based on the observation that existing energy management techniques for mobile devices, such as Dynamic Voltage Scaling (DVS), are non-cooperative in the sense that they reduce the energy consumption of a single device, disregarding potential consequences for other constraints (e.g., end-to-end deadlines) and/or other devices (e.g., energy consumption on neighboring devices). This paper argues that energy management in distributed wireless real-time systems has to be end-to-end in nature, requiring a coordinated approach among communicating devices. A cooperative distributed energy management technique (Co-DVS) is proposed that (1) adapts and maintains end-to-end latencies within specified timeliness requirements (deadlines) and (2) enhances energy savings at the devices with the highest pay-off factors that represent the relative benefits or significance of conserving energy at a device. The proposed technique employs a feedback-based approach to dynamically distribute end-to-end slack among the devices based on their pay-off factors.     

PRNN/ERLS-based predictive QoS-promoted DBA scheme for upstream transmission in EPON

This article proposes a PRNN/ERLS-based predictive QoS-promoted dynamic bandwidth allocation (PQ-DBA) scheme for upstream transmission in Ethernet passive optical network (EPON) systems. The proposed PQ-DBA scheme originally divides incoming packets of voice, video, data service traffic into six priorities, where packets having less room before QoS requirements violation or being in starvation situation will be dynamically promoted to high priority cycle-by-cycle. It predicts packets arriving at prediction interval for ONUs using pipeline recurrent neural network (PRNN)/extended recursive least squares (ERLS) so that the bandwidth allocation can be more up-to-date and then accurate. Simulation results show that the proposed PQ-DBA scheme achieves higher system utilization and lower average voice, video, data packet delay time than the DBAM scheme [Luo and Ansari, OSA J Opt Netw 4(9):561–572] by 4, and 21, 90, 43%, respectively, and the PQ-DBA scheme but without prediction by 2, and 26, 29, 34%, respectively.     

Formulae for determining heterodyne system spurious frequencies that coincide with desired output frequency

In this paper, formulae to determine the lowest order and other higher order spurious frequencies that coincide with desired output signal frequencies of mixers have been derived. The proposed formulae give general expressions that are suitable for any order of heterodyne mixing. The formulae have been verified using a suitable example and compared with the simulation results obtained through the radio frequency simulation software of Advanced Design System. The formulae directly reveal the order of the troublesome spurious frequencies that the designers would encounter in heterodyne systems. In comparison with these direct formulae, the results of existing spurious analysis software are based on the maximum order of simulation carried out. Based on these simulations, the coinciding spurious components have to be manually sorted out. Proposed formulae are quick tools used by the microwave system and circuit designers for choosing and finalizing heterodyne frequencies in their designs without the need for any simulations.     

The Design of Linear-Phase FIR Multiple-Notch Filters with Variable Notch Frequencies

In this paper, a paradigm is developed to design the linear-phase FIR multiple-notch filters with variable notch frequencies. The design procedure can be proceeded through two steps: First, a linear-phase narrow-band low-pass filter met the given bandwidth and stopband ripple specifications is designed. Second, a tuning procedure is applied to the computed low-pass filter to yield the desired multiple-notch filter. When the notch frequencies are varied, the same tuning procedure can be employed to render the multiple-notch filter with the new set of the notch frequencies. The tuning procedure employed reduces the computational complexity of designing the multiple-notch filter with the new set of the notch frequencies. The simulation results demonstrate the effectiveness of our scheme.     

ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios

Multi-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.     

Design and Evaluation of DNS as Location Manager for HIP

Host Identity Protocol (HIP) is designed to provide secure and continuous communication by separating the identifier and locator roles of the Internet Protocol (IP) address. HIP also has efficient solutions to support host mobility. In this paper, we propose a location management scheme based on Domain Name System (DNS) for HIP. In the proposed scheme, a new DNS HIP resource record is used to translate a domain name into a host identity tag and an IP address. We also develop an analytical model to study the performance of DNS as location manager in terms of success rate, which takes into account the velocity of mobile nodes, the radius of a subnet, the regional network size, the packet transmission delay between the mobile node and the rendezvous server, and the packet processing delay at the DNS and the rendezvous server. The performance results show that for a reasonable range, the DNS is a feasible solution for location management with high success rate for HIP.

A novel iterative scheme for parallel inter-symbol interference channels

In this paper, we propose a novel iterative scheme for exploiting transmit diversity using parallel independent Inter-Symbol Interference （ISI） channels. In this adaptive iterative scheme, we use EXtrinsic Information Transfer （EXIT） chart tool to choose appropriate iterative method from Iterative Combining （IC）, used as parallel concatenation turbo-like scheme, and Turbo Equalization （TE）, used as serial concatenation turbo-like scheme. It is show that the proposed iterative scheme provides excellent performance both analytically and through simulations without any compute complexity increase comparable to IC.     

Modified SMC method of blind multiuser detection for DS-CDMA systems over fading channels

This paper presents the application of sequential Monte Carlo (SMC) methodology for blind detection in wireless direct sequence code division multiple access (DS-CDMA) systems over fading channels. It is known that the conventional SMC method requires a high-computational complexity that grows exponentially with the number of active users. This paper proposes a solution to this problem by employing Cholesky factorization to decompose the observed data into separate components for each user and then the parameters of each user are estimated with the SMC inference method under the decision feedback framework. Based on these concepts, an efficient blind decision feedback SMC (DF-SMC) receiver is developed for differentially encoded DS-CDMA systems. Simulation results demonstrate the promising performance of the proposed receiver for both flat fading and frequency-selective fading channels.     

A NOVEL CONSISTENCY CONTROL ALGORITHM IN COOPERATIVE GRAPHICS EDITOR（CGE）

The research work presented in this paper is based on the concrete background of the Cooperative Graphics Editor(GGE),allowing two or more persons to remotely deit a graphic document simultaneously.A new concurrency control algorithm based on partial order set is presented,which has fast response and less undo-redo operations as there are no lock mechanisms.It is used to solve inconsistency caused by operation on intersecting graphics concurrently.CGE also possesses a mask strategy to solve inconsistency caused by operation on the same graphic concurrently.     

Preparation of nano-hydroxyapatite/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) biocomposite microspheres

Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water (s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and transmission electron microscopy (TEM).