Single Communication Channel Research Articles

Architecture of Wireless Sensor Networks with Mobile Sinks: Multiple Access Case

We propose to develop Wireless Sensor Networks with Mobile Sinks (MSSN), under high sensor node density, where multiple sensor nodes need to share one single communication channel in the node-to-sink transmission. By exploiting the tradeoff between the successful information retrieval probability and the nodes energy consumption, a number of multiple nodes transmission scheduling algorithms are proposed. Both optimal and suboptimal algorithms, which exhibit exponential and linear complexity respectively, are discussed under the desired application. Computer simulations show that suboptimal algorithms perform nearly as good as the optimal one. The study leads to the cross-layer Wireless Link layer design for MSSN.

Securing the Critical National Infrastructure

Having held nine ministerial jobs in ten years, Home Secretary John Reid has had the tremendous task of tackling the issue of security from almost every conceivable political angle. He has assumed positions as defence spokesman in opposition, armed forces minister, Secretary of State for Northern Ireland, Secretary of State for Defence and now Home Secretary. This puts him in a unique position to talk about the security of the UK within the context of the twenty‐first century. On 25 April 2007, Reid delivered the keynote address at the annual RUSI Critical National Infrastructure conference. The text below is an article formed from his address. This address followed the launch, on 29 March 2007, of the National Security and Resilience Industrial Council (RISC). RISC is an alliance of suppliers, trade associations and academics that will provide a single industry voice and channel of communication for government and others on strategic issues affecting national security and resilience. That same day, John Reid also announced that the Home Office was to be restructured into two separate departments: one covering security and the other justice.

Compact multilayer ultra-wideband six-port device for modulation/demodulation

A compact multilayer ultra-wideband (UWB) six-port device, composed of power combiners and dividers, is presented. Implemented in hybrid microstip/stripline technology, the six-port can be used as a front-end transceiver. The operational frequency spans a range of 3-5 GHz (50% fractional bandwidth), suitable for pulse signals in UWB single channel communication. Measurements and simulation results validate circuit performance as a transceiver using quaternary phase spectrum modulation.

Introduction to the Special Issue on Cost-Effectiveness Analysis

Communication is at the heart of behavior change programs in developing countries. It is hard to imagine a program designed to bring about some type of change in behavior or health status that does not utilize at least some type of directed communication. How effective are these interventions however in bringing about the desired change? And at what cost? This special issue of the Journal of Health Communication examines the state of the art for addressing the familiar question What is the bang for the buck? We expect this issue to be of interest to two main audiences: (1) health communication specialists interested in designing the most effective programs on limited budgets and (2) researchers/evaluators interested in applying state-of-the-art methods for conducting cost-effectiveness analysis of communication programs for behavior change. Health communication programs aim to bring about change in individual behaviors and social norms using some combination of (1) mass media (2) community-level interventions (e.g. community mobilization) and (3) interpersonal communication/ counseling. Programs today tend to incorporate the highly effective elements of entertainment education. Earlier evaluations often measured the effects of a program consisting of a few or even a single communication channel in a limited geographical area. Todays communication programs however often use a more comprehensive approach consisting of multiple mutually reinforcing media. (excerpt)

Group Consensus: The Impact of Multiple Dialogues

The research results on group consensus have been ambiguous within the field of Group Support Systems (GSSs). Some research studies have shown that groups using multiple communication channels produce more ideas, and more unique ideas than groups using a single communication channel. In addition, a second set of research findings have shown that groups using GSSs report group members hold “less consensus” with the group's decision. This research studies more closely how these two characteristics; communication channel and consensus, interact. Specifically, can “less consensus” be a function of the choice of channels used in problem solving. The results show that groups using a single communication channel generate more actual consensus than groups using multiple communication channels. Furthermore, the single channel discussions provide more integrative comments and these integrative comments may help explain the difference in consensus. These results suggest that those striving for consensus from group members should consider production methods used to create the information that is to be used in the decision.

Resource-constrained rate control for motion JPEG2000

With the increasing importance of heterogeneous networks and time-varying communication channels, fine scalability has become a highly desirable feature in both image and video coders. A single highly scalable bitstream can provide precise rate control for constant bitrate (CBR) traffic and accurate quality control for variable bitrate (VBR) traffic. We first propose two leaky-bucket rate allocation methods that provide constant quality video under buffer constraints. These methods can be used with all scalable coders. Moreover, we make use of one of these methods (DBRC) and extend it so that it can be used when multiple sequences are multiplexed over a single communications channel. The goal is to allocate the capacity of the channel between sequences to achieve constant quality across all sequences. Experimental results using Motion JPEG2000 demonstrate substantial benefits.

Modeling and verification of a class of real-time systems by the use of High Level Petri Nets

Homogeneous, shared memory multiprocessors that incorporate real-time operating systems constitute in many corporations the basic platforms for developing applications of plant monitoring and automation. In this work, a template model based on the High Level Petri Net (HLPN) formalism is proposed for this class of computers. Mapping functional and timing requirements of the application software to states of this model and searching for their existence in the reachability tree of the net can verify the satisfaction of these requirements. A state searching algorithm has been developed for the case of a shared memory multiprocessor in which there is a bus-based interconnection network supporting a single communication channel for the exchange of data among the CPUs, the common memory and the computer interfaces. This algorithm groups the infinite number of states of the HLPN to a number of finite regions, identifies the region, which the desired state belongs to, and checks for the existence of a path from the initial state that leads to this region. In order to demonstrate the use of the template in the modeling and verification of timing and functional specifications of a system of the considered class, the implementation of the automation functions of a chemical reactor by a VME-bus based multiprocessor with two CPUs and running under the control of the OS-9 operating system was studied. In this study the template model was used to create a specific for this application HLPN model. The response times of two automation functions were predicted by the use of this model and compared with those derived from the operating characteristics of the reactor.

Phase jitter in single-channel soliton systems with constant dispersion

The phase jitter of optical solitons in single-channel communication systems with constant dispersion and distributed amplification is studied in detail. The variational method is used to derive equations that model phase jitter caused by amplifier noise. These equations are solved analytically. Simple formulas are obtained for the phase variance of an ensemble of solitons, which together cover the entire range of practical transmission distances. These formulas are validated for parameters of current interest by numerical solutions of the nonlinear Schroedinger equation.

Microarrays: The Reincarnation of Multiplexing in Laboratory Medicine, But Now More Relevant?

Multiplexing is a relatively new addition to the Oxford English Dictionary and in the encyclopedic version is defined as “the simultaneous transmission of several messages along a single channel of communication”. It is also a relatively new addition to the vocabulary of the clinical chemist, having been imported from the lexicon of the genomics, proteomics, and drug discovery scientists, but it is not a new concept for the clinical chemist who has been exposed to the use of so-called multichannel analyzers for many years, first continuous flow and then discrete analyzers. Some historians of automation might look back to the centrifugal analyzer as the first challenge to multichannel analysis, but there is now at least one example of this technology that provides a profile of analytes on a single sample (1). If these are indeed early examples of multiplexing analyzers, then they distinguish themselves—by today’s standards—by using large amounts of sample and reagents, by a choice of analytes that are not always clinically justified, and by an inability (with a few notable exceptions) to embrace immunoassay and other ligand-binding assay techniques for low-concentration analytes. However, the greatest legacy of the first era of multiplexing analysis is probably the perception that there is too much laboratory testing as well as numerous apocryphal stories of patients being investigated after the generation of an abnormal result, rather than for the presenting symptoms! So with the advent of microarray platforms, are we seeing the reincarnation of multiplexing analytical strategies and the evolutionary cycle turning full circle? The concept of the multianalyte array based on immunologic capture and interrogation technology is not new, with an editorial on the subject in this Journal almost a decade ago (2). So what has been achieved in the intervening period? Certainly the interrogation of captured molecules using antibodies with …

Ca2+ signalling between single L-type Ca2+ channels and ryanodine receptors in heart cells.

Ca2+-induced Ca2+ release is a general mechanism that most cells use to amplify Ca2+ signals. In heart cells, this mechanism is operated between voltage-gated L-type Ca2+ channels (LCCs) in the plasma membrane and Ca2+ release channels, commonly known as ryanodine receptors, in the sarcoplasmic reticulum. The Ca2+ influx through LCCs traverses a cleft of roughly 12 nm formed by the cell surface and the sarcoplasmic reticulum membrane, and activates adjacent ryanodine receptors to release Ca2+ in the form of Ca2+ sparks. Here we determine the kinetics, fidelity and stoichiometry of coupling between LCCs and ryanodine receptors. We show that the local Ca2+ signal produced by a single opening of an LCC, named a 'Ca2+ sparklet', can trigger about 4-6 ryanodine receptors to generate a Ca2+ spark. The coupling between LCCs and ryanodine receptors is stochastic, as judged by the exponential distribution of the coupling latency. The fraction of sparklets that successfully triggers a spark is less than unity and declines in a use-dependent manner. This optical analysis of single-channel communication affords a powerful means for elucidating Ca2+-signalling mechanisms at the molecular level.

PARALLEL NEURAL LEARNING FOR CONTROL PROBLEMS ON A BUS-BASED ARCHITECTURE

In [6], we distributed training instances over a single-channel broadcast communication model to speed up execution of the back-propagation learning algorithm for classification problems. In this paper, we extend this concept to control problems, where the output is not necessarily 0 or 1, but ranges over an interval. We first propose a modified back-propagation learning algorithm that incrementally decreases the error threshold by half in order to process training instances with large weight changes as quickly as possible. This modified back-propagation learning algorithm is then parallelized using the single-channel broadcast communication model to n processors, where n is the number of training instances. Finally, the parallel back-propagation learning algorithm is modified for execution on a bounded number of processors to cope with real-world conditions.

Advertising Food to Children — Dispelling the Myths

This paper explores some misconceptions about children's advertising, in the context of food brands. It concludes that children are in essence ‘mini‐adults’, both in their approach to food, and to advertising generally. It illustrates children's sophistication about advertising, but concludes that it is essential to create a rounded ‘brand experience’ beyond any single communication channel.

Reconstruction of dynamic systems as applied to secure communications

An analysis is made of a method of reconstructing signals which parametrically modulate a chaotic generator using a one-dimensional realization of its oscillation process. Test examples are used to demonstrate the efficiency of this method for simultaneous independent transmission of several information signals over a single communication channel.

An interval-amplitude algorithm for deinterleaving stochastic pulse train sources

We consider the deinterleaving of pulse trains transmitted by N independent sources. The deinterleaving problem considered has applications in spectral estimation, where N (known number) stochastic parameterized sources are sampled using a fast sensor recording the sign of the signal from each source. Due to communication constraints, the recorded signals-pulse trains or sequences of zeros and ones-are superimposed and transmitted through a single Gaussian communication channel. The aim of this paper is to estimate the parameters that characterize the sources and identify those sources that are responsible for the observed noisy pulses. Our proposed algorithm, subject to modeling assumptions, optimally combines hidden Markov model and binary time series estimation techniques and yields maximum likelihood parameter estimates of the sources.

Quasi-soliton propagation with periodic optical phase conjugation

By using optical phase conjugation, the quasi-soliton is shown to support ultra-high speed single-channel optical communication over 102 Tb·km/s.

Speech enhancement for crosstalk interference

Speech signals are often degraded by additive interference over single-channel communication systems. For stationary and well defined noise sources, effective solutions exist. However, it is often difficult to formulate a model for nonstationary and speechlike noise sources such as crosstalk or multispeaker babble, which exist in real scenarios. In this paper, we propose a solution to this problem under the assumption that we have access to the clean speech signal prior to transmission. A novel method for tracking transmission noise characteristics is described. Based on this noise estimate, a new speech enhancement technique is proposed. The enhancement method is evaluated for multispeaker babble noise, and shown to substantially improve both the quality and intelligibility of the processed speech signal.

Dynamic prioritized conflict resolution on multiple access broadcast networks

In a multiple access broadcast network, all network nodes share a single shared communication channel, and there is the possibility of a collision when two or more nodes transmit at overlapping times. We propose a dynamic prioritized conflict resolution algorithm in which, when a collision occurs, all colliding messages are retransmitted according to their priority. When a new message arrives, it is allowed to participate in the algorithm as soon as it finds its priority is higher than that of some broadcast message. Using a time-slotted model, for any arrival pattern and priority distribution, we show that our algorithm runs in expected linear time, i.e., O(r), where r is the total number of message transmitted. We also show that the expected waiting time for any message x is O(rank(x)+log s), where rank(x) is the expected number of messages with higher priority which transmit while x is waiting, and s is the minimum of the total number of messages participating in the algorithm and the total number of nodes in the network. The analysis presented in this work also includes an improved analysis of our original (static) prioritized conflict resolution algorithm. This work is applicable to multimedia communications where different priority values could be assigned to different kinds of traffic, and our algorithm ensures that the high-priority real-time traffic has the minimum delay.

Use of a single chip fixed-point DSP for multiple speech channel vocoders

In this paper, the use of an advanced digital signal processor (DSP) makes possible the parallel real-time implementation of more than one speech coder on a single-chip DSP. Thus, many speech channels can share a single digital communications channel at low cost. Besides the hardware requirements, the algorithms' implementation is considered for multi-channel single-pitch excited LPC vocoders. The Motorola DSP56000/DSP56001 is selected and the execution times are presented. A variable length coding scheme for reduced bit-rate is also described. Up to 10 vocoders are simultaneously implemented on a single DSP and the algorithms can be used as the basis for the implementation of more sophisticated speech coders.

Communication protocol for a local network based on code division multiplexing

A communication protocol for a local network that handles voice signals and uses ‘direct sequence spread spectrum’ techniques ( DS-SS), is presented. The control of the protocol is distributed among the network users, providing them with the capability for full-duplex communication and successful channel acquisition without data collisions. The access of the single communication channel by any user of the network and the routing of calls are based on the detection of the number of the decoded signal levels. The implementation of the network is simplified with the use of a single code per communication. The protocol operation ( including the call scheduling and signalling processes) that generates all the signals necessary for communication in the network ( ring, idle, busy) is described in detail.

Optimal prioritized conflict resolution on a multiple access channel

A multiple access broadcast network (MABN) is a computer network in which there is a single shared communication channel and every network node can receive all messages transmitted over the channel. A major difficulty in using broadcast communication is the issue of access to the channel. The authors deal with the following prioritized conflict resolution problem: a collection of c messages is initially distributed among nodes on an MABN; each message is associated with a value representing its priority or deadline; and it is required that the messages be broadcast in ascending order of this value. This problem is solved by a distributed prioritized conflict resolution algorithm. It is proved that the expected waiting time of the ith network node to transmit is Theta (i+log c), which is optimal. It is also shown that the algorithm runs in the expected linear time, which is optimal in both the number of slots used and the total elapsed time including local processing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>