Design of fast core node processor for packet forwarding without header modification in optical networks

We present a design of a fast all-optical core-node processor that performs packet-forwarding in optical networks without header-modification. The design is based on bit-serial architecture using TOADs as logic-gates that perform modulo-arithmetic to forward packets.

Wavelet packet decomposition-based fault diagnosis scheme for SRM drives with a single current sensor

Power converters are a key, but vulnerable component in switched reluctance motor (SRM) drives. In this paper, a new fault diagnosis scheme for SRM converters is proposed based on the wavelet packet decomposition (WPD) with a dc-link current sensor. Open- and short-circuit faults of the power switches in an asymmetrical half-bridge converter are analyzed in details. In order to obtain the fault signature from the phase currents, two pulse-width modulation signals with phase shift are injected into the lower-switches of the converter to extract the excitation current, and the WPD algorithm is then applied to the detected currents for fault diagnosis. Moreover, a discrete degree of the wavelet packet node energy is chosen as the fault coefficient. The converter faults can be diagnosed and located directly by determining the changes in the discrete degree from the detected currents. The proposed scheme requires only one current sensor in the dc link, while conventional methods need one sensor for each phase or additional detection circuits. The experimental results on a 750-W three-phase SRM are presented to confirm the effectiveness of the proposed fault diagnosis scheme.

Packet voice/data in local broadcast networks

A local area network that can support both voice and data packets offers economic advantages due to the use of only a single network for both types of traffic, greater flexibility to changing user demands, and it also enables efficient use to be made of the transmission capacity. The latter aspect is very important in local broadcast networks where the capacity is a scarce resource, for example mobile radio. This research has examined two types of local broadcast network, these being the Ethernet-type bus local area network and a mobile radio network with a central base station. With such contention networks, medium access control (MAC) protocols are required to gain access to the channel. MAC protocols must provide efficient scheduling on the channel between the distributed population of stations who want to transmit. No access scheme can exceed the performance of a single server queue, due to the spatial distribution of the stations. Stations cannot in general form a queue without using part of the channel capacity to exchange protocol information. In this research, several medium access protocols have been examined and developed in order to increase the channel throughput compared to existing protocols. However, the established performance measures of average packet time delay and throughput cannot adequately characterise protocol performance for packet voice. Rather, the percentage of bits delivered within a given time bound becomes the relevant performance measure. Performance evaluation of the protocols has been examined using discrete event simulation and in some cases also by mathematical modelling. All the protocols use either implicit or explicit reservation schemes, with their efficiency dependent on the fact that many voice packets are generated periodically within a talkspurt. Two of the protocols are based on the existing 'Reservation Virtual Time CSMA/CD' protocol, which forms a distributed queue through implicit reservations. This protocol has been improved firstly by utilising two channels, a packet transmission channel and a packet contention channel. Packet contention is then performed in parallel with a packet transmission to increase throughput. The second protocol uses variable length packets to reduce the contention time between transmissions on a single channel. A third protocol developed, is based on contention for explicit reservations. Once a station has achieved a reservation, it maintains this effective queue position for the remainder of the talkspurt and transmits after it has sensed the transmission from the preceeding station within the queue. In the mobile radio environment, adaptions to the protocols were necessary in order that their operation was robust to signal fading. This was achieved through centralised control at a base station, unlike the local area network versions where the control was distributed at the stations. The results show an improvement in throughput compared to some previous protocols. Further work includes subjective testing to validate the protocols' effectiveness.

Adaptive modulation scaling scheme for wireless sensor networks

Limited energy is a big challenge for large scale wireless sensor networks (WSN). Previous research works show that modulation scaling is an efficient technique to reduce energy consumption. However, the impacts of using modulation scaling on packet delivery latency and loss are not considered, which may have adverse effects on the application qualities. In this paper, we study this problem and propose control schemes to minimize energy consumption while ensuring application qualities. We first analyze the relationships of modulation scaling and energy consumption, end-to-end delivery latency and packet loss ratio. With the analytical model, we develop a centralized control scheme to adaptively adjust the modulation levels, in order to minimize energy consumption and ensure the application qualities. To improve the scalability of the centralized control scheme, we also propose a distributed control scheme. In this scheme, the sink will send the differences between the required and measured application qualities to the sensors. The sensors will update their modulation levels with the local information and feedback from the sink. Experimental results show the effectiveness of energy saving and QoS guarantee of the control schemes. The control schemes can adapt efficiently to the time-varying requirements on application qualities. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.

An adaptive code position modulation scheme for wireless sensor networks

In this letter, an energy-efficient adaptive code position modulation scheme is proposed for wireless sensor networks to provide the relatively stable bit error ratio (BER) performance expected by the upper layers. The system is designed with focus on the adaptive control of transmission power, which is adjusted based on the measured power density of background noise. Interfaces among the modulation module, packet scheduling module and upper layer are provided for flexible adjustments to adapt to the background noise and deliver expected application quality. Simulations with Signal Processing Worksystem (SPW) validate the effectiveness of the scheme. © 2005 IEEE.

An enhanced scalable probe-based multicast admission control scheme

To guarantee QoS for multicast transmission, admission control for multicast sessions is expected. Probe-based multicast admission control (PBMAC) scheme is a scalable and simple approach. However, PBMAC suffers from the subsequent request problem which can significantly reduce the maximum number of multicast sessions that a network can admit. In this letter, we describe the subsequent request problem and propose an enhanced PBMAC scheme to solve this problem. The enhanced scheme makes use of complementary probing and remarking which require only minor modification to the original scheme. By using a fluid-based analytical model, we are able to prove that the enhanced scheme can always admit a higher number of multicast sessions. Furthermore, we present validation of the analytical model using packet based simulation. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.

A quality driven adaptation scheme for DASH streaming

In this work we present a quality driven approach to DASH (Dynamic Adaptive Streaming over HTTP) for segment selection in varying network conditions. Current adaption algorithms focus largely on regulating data rates using network layer parameters by selecting the level of quality on offer that can eliminate buffer underrun without considering picture fidelity. In reality, viewers may accept a level of buffer underrun in order to achieve an improved level of picture fidelity. In this case, the conventional DASH algorithms can cause extreme degradation of the picture fidelity when attempting to eliminate buffer underrun with scarce bandwidth availability. Our work is concerned with a quality-aware rate adaption scheme that maximizes the client's quality of experience in terms of both continuity and fidelity (picture quality). Results show that the scheme proposed can maintain a high level of quality for streaming services, especially at low packet loss rates. It is also shown that by eliminating buffer underrun completely, the PSNR that reflects the picture quality of the video is greatly reduced. Our scheme offers the offset between continuity-based quality and resolution-based quality, which can be used to set threshold values for the level of quality desired by clients with different quality requirements. © 2013 IEEE.

Toward a business-to-business channel incentives classification scheme

A recent focus on intermediary compensation underscores the need to organize the many complex incentives used by channel practitioners. Employing a grounded theory methodology, a channel incentives classification scheme is induced from 170 unique channel incentives used in 59 high technology suppliers’ channel programs. The incentives are organized into 16 subcategories and 5 major categories: Credible Channel Policies, Market Development Support, Supplemental Contact, High-Powered Incentives, and End-User Encouragements. Each incentive subcategory is discussed as a means of controlling reseller behaviors. Also, the conditions that give rise to the implementation of incentives are investigated through four testable research propositions.

Packet switching in wide area broadband private networks

B-ISDN is a universal network which supports diverse mixes of service, applications and traffic. ATM has been accepted world-wide as the transport technique for future use in B-ISDN. ATM, being a simple packet oriented transfer technique, provides a flexible means for supporting a continuum of transport rates and is efficient due to possible statistical sharing of network resources by multiple users. In order to fully exploit the potential statistical gain, while at the same time provide diverse service and traffic mixes, an efficient traffic control must be designed. Traffic controls which include congestion and flow control are a fundamental necessity to the success and viability of future B-ISDN. Congestion and flow control is difficult in the broadband environment due to the high speed link, the wide area distance, diverse service requirements and diverse traffic characteristics. Most congestion and flow control approaches in conventional packet switched networks are reactive in nature and are not applicable in the B-ISDN environment. In this research, traffic control procedures mainly based on preventive measures for a private ATM-based network are proposed and their performance evaluated. The various traffic controls include CAC, traffic flow enforcement, priority control and an explicit feedback mechanism. These functions operate at call level and cell level. They are carried out distributively by the end terminals, the network access points and the internal elements of the network. During the connection set-up phase, the CAC decides the acceptance or denial of a connection request and allocates bandwidth to the new connection according to three schemes; peak bit rate, statistical rate and average bit rate. The statistical multiplexing rate is based on a `bufferless fluid flow model' which is simple and robust. The allocation of an average bit rate to data traffic at the expense of delay obviously improves the network bandwidth utilisation.

An examination of adverse drug reaction reporting to the yellow card scheme

Chief pharmacists in 209 hospitals were surveyed about ADR reporting schemes, the priority given to ADR reporting, and attitudes towards ADR reporting. ADR reporting had a low managerial priority. Local reporting schemes were found to be operating in 37% trusts, but there were few plans to start new schemes. Few problems were discovered by the introduction of pharmacist ADR reporting. Chief pharmacists had concerns about the competence of hospital pharmacists to detect ADRs and were in favour of increased training. Lack of time on wards, and recruitment difficulties were suggested as reasons for hospital pharmacist under-reporting. Teaching hospitals appeared to have an increased interest in ADR reporting. A retrospective analysis of reporting trends within the West Midlands region from 1994, showed increasing or stable reporting rates for most sectors of reporters, except for general practitioners (GPs). The West Midlands region maintained higher ADR reporting rates than the rest of the UK. National reporting figures showed a worrying decline in ADR reports from healthcare professionals. Variation was found in the ADR reporting rates of Acute NHS Hospital Trusts and Primary Care Trusts (PCTs) in the West Midlands region, including correlations with prescribing rates and other PCT characteristics. Qualitative research into attitudes of GPs towards the Yellow Card scheme was undertaken. A series of qualitative interviews with GPs discovered barriers and positive motivators for their involvement in the Yellow Card scheme. A grounded theory of GP involvement in the Yellow Card scheme was developed to explain GP behaviour, and which could be used to inform potential solutions to halt declining rates of reporting. Under-reporting of ADRs continues to be a major concern to those who administer spontaneous reporting schemes.

The evaluation and development of the lead authority partnership scheme as a central intervention strategy for health and safety enforcement by local authorities

The research comprises a suite of studies that examines and develops the Lead Authority Partnership Scheme (LAPS) as a central intervention strategy for health and safety by local authority (LA) enforcers. Partnership working is a regulatory concept that in recent years has become more popular but there has been little research conducted to investigate, explore and evaluate its practical application. The study reviewed two contrasting approaches to partnership working between LAs and businesses, both of which were intended to secure improvements in the consistency of enforcement by the regulators and in the health and safety management systems of the participating businesses. The first was a well-established and highly prescriptive approach that required a substantial resource commitment on the part of the LA responsible for conducting a safety management review (SMR) of the business. As a result of his evaluation of the existing ‘full SMR’ scheme, the author developed a second, more flexible approach to partnership working. The research framework was based upon a primarily qualitative methodology intended to investigate and explore the impact of the new flexible arrangements for partnership working. The findings from this study of the flexible development of the scheme were compared and contrasted with those from studies of the established ‘full SMR’ scheme. A substantial degree of triangulation was applied in an attempt to strengthen validity and broaden applicability of the research findings. Key informant interviews, participant observation, document/archive reviews, questionnaires and surveys all their particular part to play in the overall study. The findings from this research revealed that LAPS failed to deliver consistency of LA enforcement across multiple-outlet businesses and the LA enforced business sectors. Improvement was however apparent in the safety management systems of the businesses participating in LAPS. Trust between LA inspector and safety professional was key to the success of the partnerships as was the commitment of these key individuals. Competition for precious LA resources, the priority afforded to food safety over health and safety, the perceived high resource demands of LAPS, and the structure and culture of LAs were identified as significant barriers to LA participation. Flexible approaches, whilst addressing the resource issues, introduced some fresh concerns relating to credibility and delivery. Over and above the stated aims of the scheme, LAs and businesses had their own reasons for participation, notably the personal development of individuals and kudos for the organisation. The research has explored the wider implications for partnership working with the overall conclusion it is most appropriately seen as a strategic level element within a broader structured intervention strategy.