Demessie Girma

Artificial Neural Network Implementation on a Fine-Grained FPGA

This paper reports on the implementation of an Artificial Neural Network (ANN) on an Atmel AT6005 Field Programmable Gate Array (FPGA). The work was carried out as an experiment in mapping a bit-level, logically intensive application onto the specific logic resources of a fine-grained FPGA. By exploiting the reconfiguration capabilities of the Atmel FPGA, individual layers of the network are time multiplexed onto the logic array. This allows a larger ANN to be implemented on a single FPGA at the expense of slower overall system operation.

A Hopfield neural-network-based dynamic channel allocation with handoff channel reservation control

As channel allocation schemes become more complex and computationally demanding in cellular radio networks, alternative computational models that provide the means for faster processing time are becoming the topic of research interest. These computational models include knowledge-based algorithms, neural networks, and stochastic search techniques. This paper is concerned with the application of a Hopfield (1982) neural network (HNN) to dynamic channel allocation (DCA) and extends previous work that reports the performance of HNN in terms of new call blocking probability. We further model and examine the effect on performance of traffic mobility and the consequent intercell call handoff, which, under increasing load, can force call terminations with an adverse impact on the quality of service (QoS). To maintain the overall QoS, it is important that forced call terminations be kept to a minimum. For an HNN-based DCA, we have therefore modified the underlying model by formulating a new energy function to account for the overall channel allocation optimization, not only for new calls but also for handoff channel allocation resulting from traffic mobility. That is, both new call blocking and handoff call blocking probabilities are applied as a joint performance estimator. We refer to the enhanced model as HNN-DCA++. We have also considered a variation of the original technique based on a simple handoff priority scheme, here referred to as HNN-DCA+. The two neural DCA schemes together with the original model are evaluated under traffic mobility and their performance compared in terms of new-call blocking and handoff-call dropping probabilities. Results show that the HNN-DCA++ model performs favorably due to its embedded control for assisting handoff channel allocation.

Dynamic 3G network selection for increasing the competition in the mobile communications market

This paper proposes a market-based framework in which service providers, network operators and users are able to trade communications services. For this purpose, a middleware has been specified in which software agents can supply or purchase QoS contracts. Benefits from the proposal are increased competition in the provision of mobile services, an integrated framework for the management of services and networks in a multi-provider environment and the possibility to develop smarter applications that make an efficient use of the scarce radio spectrum.

H.263 video traffic modelling for low bit rate wireless communications

Video traffic exhibits a greater complexity than traditional services such as voice. Therefore, it is necessary to identify the relevant statistical properties, which characterise this type of traffic and provide the tools to properly model them so that networks could be efficiently dimensioned. This work presents on one hand a detailed analysis of the statistical features, which characterise H.263 video traffic streams coded at bit rates suitable for wireless communications. On the other hand, the paper presents and evaluates an on-line video traffic model, which captures the most significant features observed.

Efficient UMTS data service provision using Infostations

This paper presents an extension to the proposal for small discontinuous data cells known as Infostations. By increasing the data rates which can be supported in certain areas, Infostations offer the possibility of cheap data service provision. This paper examines the effect of discontinuous coverage on capacity, and proposes the concept of a logical Infostation which controls a number of radio parts connected by a DQDB subnetwork. The advantages of this architecture are indicated and its relationship to existing proposals such as GPRS and mobile IP are studied. Furthermore, the integration of such a system into a future UMTS with particular emphasis on issues such as registration, authentication and billing are discussed.

Real-time generation of synthetic MPEG-4 video traffic using wavelets

This paper presents a wavelet-based video traffic model capable of real-time generation of synthetic MPEG-4 video traffic streams. The strength of the model includes a unified approach to LRD (long range dependence) and SRD (short range dependence) modelling, computational efficiency and benefits associated with the on-line aspect of the model, e.g. no storage requirements. The model accurately estimates system performance for every video quality considered.

QoS management with dynamic bearer selection schemes

This paper presents an evaluation of a radio level QoS management scheme developed to ensure the maintenance of QoS contracts. The concept of QoS contract is defined as the specification of the quality requirement for various types of services. According to the contracted QoS, a dynamic bearer selection is performed to adapt the link to the channel quality variations. Terrestrial Trunked Radio system (TETRA) presents itself as a suitable platform for illustrating the concept of QoS contract. This arises from its feature-rich bearer services that support data and voice with varying levels of error protection. The generic QoS management scheme presented in this paper has been applied to a private mobile radio system but it also represents an appropriate platform for multi-vendor, multi-technology and multimedia environments such as those found with 3G systems.

Statistical analysis and evaluation of modelling techniques for self-similar video source traffic

Video is expected to be a significant part of information in future mobile communication systems. An accurate and efficient video source traffic characterisation is therefore essential in order to assess new traffic handling algorithms and appropriately dimension the supporting communication networks. Modelling VBR traffic as a stochastic process is often challenging since such traffic exhibits the co-existence of long-term and short-term dependencies. To highlight such issues, in this paper, three video traffic-modelling techniques are presented and analysed in terms of first- and second-order statistics. A comparative evaluation of these models has been carried out based on simulation.

Dynamic channel assignment in a DQDB MAN based PCN access network

This paper considers a PCN architecture based on the DQDB MAN for implementing distributed control of resource allocation in mobile communications systems. In particular the paper considers dynamic resource allocation (DCA) strategies based on the distributed MAN architecture which may be implemented at a rate fast enough to accommodate statistical multiplexing on the air interface at the talkspurt level. A DCA strategy is proposed based on the interconnection of microcellular base stations by a hierarchical MAN topology. Performance estimates of the distributed DCA scheme are provided and comparisons made with a fixed channel allocation strategy.

Semicustom ASIC design facility based on logic cell arrays

Abstract Application-specific integrated circuits (ASICs) are an increasingly important option for electronic systems designers, primarily as a result of rapid advances in CAD and manufacturing technology. As a result there is now a need to include ASIC design methodologies and considerations in undergraduate and postgraduate experience courses in electronic engineering. The paper describes a semicustom design laboratory set-up for teaching such a course at the University of Strathclyde. The main technology chosen for design exercises is the logic cell array (LCA). The unique feature of this device is that its configuration is determined by the contents of an on-chip static memory. This means that the device may be reconfigured an unlimited number of times, which makes it very economical and particularly attractive for educational use. Furthermore, field-programmable semicustom devices such as the LCA allow design exercises to be taken from the concept stage to ‘working silicon’ in a timescale that is much shorter than other ASIC alternatives. The paper outlines a sequence of design procedures performed in a typical design laboratory. In particular, it describes a low cost LCA prototyping board designed to act as a verification tool for LCA-based circuit development.