Adrian S. Poulton

Dynamic fractional frequency reuse based hybrid resource management for femtocell networks

Femtocell access points are inexpensive, plug and play home base stations designed to extend radio coverage and increase capacity within indoor environments. Their inherent uncoordinated and overlaid deployment however, means existing radio resource management (RRM) techniques are often ineffectual. Recent advances in dynamic RRM have emphasised the need for more efficient resource management strategies. While centralised resource management offers improved coordination and operator control giving better interference management, it is not scalable for increasing nodes. Distributed management techniques in contrast, do afford scaled deployment, but at higher node densities incur performance degradation in both system throughput and link-quality because of poor coordination. The level of spectrum sharing mandated by macro-femto deployment also impacts on system throughput and is scenario dependant. This paper presents a new hybrid resource management algorithm( HRMA) for down-links in orthogonal frequency division multiple access-based systems, with the model analysed for a range of macro-femto deployment scenarios. HRMA employs a dynamic fractional frequency reuse scheme for macro-cell deployment with frequency reuse defined for femto users depending on their location by making certain frequencies locally available based on macro-femto tier information sharing and efficient localised spectrum utilisation. Quantitative performance results confirm the efficacy of the HRMA strategy for various key system metrics including interference minimisation, outage probability and throughput.

Energy efficient relay-assisted cellular network model using base station Switching

Cellular network planning strategies have tended to focus on peak traffic scenarios rather than energy efficiency. By exploiting the dynamic nature of traffic load profiles, the prospect for greener communications in cellular access networks is evolving. For example, powering down base stations (BS) and applying cell zooming can significantly reduce energy consumption, with the overriding design priority still being to uphold a minimum quality of service (QoS). Switching off cells completely can lead to both coverage holes and performance degradation in terms of increased outage probability, greater transmit power dissipation in the up and downlinks, and complex interference management, even at low traffic loads. In this paper, a cellular network model is presented where certain BS rather than being turned off, are switched to low-powered relay stations (RS) during zero-to-medium traffic periods. Neighbouring BS still retain all the baseband signal processing and transmit signals to corresponding RS via backhaul connections, under the assumption that the RS covers the whole cell. Experimental results demonstrate the efficacy of this new BS-RS Switching technique from both an energy saving and QoS perspective, in the up and downlinks.

Traffic-and-interference aware base station switching for green cellular networks

Base station (BS) sleeping in cellular networks has emerged as a promising solution for more energy efficient communications, concomitant with lowering the network carbon footprint. Switching off specific BS entirely however, can lead to coverage holes and severe performance degradation. To avoid coverage holes, the transmit power of neighbouring BS must be commensurately increased, which can cause higher interference to other cell users. Recently a BS-RS (relay station) switching model has been proposed where the BS changes operating mode to a RS during off-peak periods rather than being completely turned off. This paper presents a traffic-aware and traffic-and-interference aware switching strategy for both the BS sleeping and BS-RS switching paradigms, which dynamically establishes the conditions for a BS to alter its working mode. The switching is based upon a dynamic traffic threshold allied with the received BS interference level. Analysis corroborates both new algorithms significantly improve network energy efficiency, while upholding the requisite quality of service provision.

Progress of a Modular Prosthetic Arm

Active prosthetic devices to replace missing hands or arms have much in common with robotic dextrous manipulators for industrial tasks (Gruver, 1994). However, the design of an upper limb prosthesis presents a set of restraints which may differ considerably from those in other robotics applications. A mass-produced robot of standardised design may be usable in many different situations, while the needs of prosthetics users are highly individual. The degree of loss can vary from a partial hand up to a complete arm including the shoulder. Variants are needed to cater for different sizes and for the two sides. User surveys (Kyberd et al., 1998a; Kyberd et al., 1999) have confirmed that a prosthesis should be light, reliable, functional, look natural, and be quiet in operation. This contrasts with the requirements of industrial robots where weight, appearance and noise level may be less important than repeatability. If the prosthesis does not make life any easier for the user, it is likely to be rejected. A functional prosthesis must, then, offer real advantages over a purely cosmetic one for it to be accepted. Indeed, the majority of users have one good hand, and become quite adept at performing tasks one-handedly, with little involvement of the prosthetic hand.

An interference-aware virtual clustering paradigm for resource management in cognitive femtocell networks

Display Omitted We present a new generalised virtual clustering femtocell (GVCF) paradigm.An interference-aware management architecture for dense femtocell deployments.An adaptive resource allocation framework for femtocell networks.A scalable low computational solution for joint macro-femtocell deployment.Logical clustering of femtocells significantly improves SINR and SE performance. Femtocells represent a promising alternative solution for high quality wireless access in indoor scenarios where conventional cellular system coverage can be poor. They are randomly deployed by the end user, so only post-deployment network planning is possible. Furthermore, this uncoordinated deployment creates severe interference to co-located femtocells, especially in dense deployments. This paper presents a new architecture using a generalised virtual cluster femtocell (GVCF) paradigm, which groups together FAP into logical clusters. It guarantees severely interfering and overlapping femtocells are assigned to different clusters. Since each cluster operates on different band of frequencies, the corresponding virtual cluster controller only has to manage its own FAPs, so the overall system complexity is low. The performance of the GVCF algorithm is analysed from both a resource availability and cluster number perspective. Simulation results conclusively corroborate the superior performance of the GVCF model in interference mitigation, particularly in high density FAP scenarios.

A wireless telemetry system for training users of upper limb prostheses

Telemetry from prosthetic systems is useful in aiding the users and clinical team in setting up and training and monitoring in the use of a prosthesis. The different forms are discussed and a new radio frequency based telemetry system is described. This system uses a computer to display the data and a video mixer to place the information on the same screen as the image of the user so that their actions and control signals can be simultaneously recorded for later study.

FES Indoor Rowing and On-water Sculling

Although individuals with spinal cord injury (SCI) regard exercise as important and clearly can benefit from proper exercise, there are several hurdles to overcome. Most importantly, it has been suggested that an exercise intensity of at least 6 METs (i.e. oxygen consumption of 21 ml/kg/min) is required to lower the relative risk for coronary heart disease (Tanasescu et al., 2002) and to significantly improve blood lipids volumes of at least 1,200–2,200 kcal/week (Durstine et al., 2001). However, many persons with SCI can have difficulty achieving these levels (Manns and Chad, 1999). Even though some can achieve moderately high peak oxygen consumptions using their upper body muscles alone, maintaining sufficient aerobic power with small muscle mass exercise is difficult. Exercise performance may be limited by local fatigue of the highly stressed arm musculature despite adequate systemic responses.

Towards the Development of Full Motion FES Rowing with Accurate Ergometry: RowStim IV

A novel FES rowing system is presented that facilitates a near normal rowing style. The system is presently based on the Concept2 ergometer. He we present an error analysis the C2 performance monitor which suggests that a more accurate monitor will be required for medal placement in competitive rowing events.

A Cell Range Expansion Framework for Closed Access Femtocell Networks

While femtocell networks represent a promising solution for extending high data-rate wireless services in indoor environments, despite their many benefits the short coverage distances involved can lead to frequent handovers being triggered resulting in overloading the macrocells. This handover problem is further exacerbated for users operating at the cell boundary. One solution is to keep the mobile station (MS) connected to the femtocell access points (FAP) by applying a handover bias to expand the femtocells coverage, though arbitrarily increasing the cell range can have a detrimental effect on system performance as the received interference will increase and may exceed tolerable levels. Many disparate factors including: FAP deployment density; resource constraints; and cell range expansion (CRE) influence the crucial interference-system performance nexus, and this was the motivation to analyse this relationship in order to facilitate successful FAP deployment. This paper critically analyses the impact of femtocell range expansion with a system-level simulation being undertaken for cooperative and non-cooperative resource allocation strategies. A new CRE framework for femtocell networks is then proposed, which takes cognisance of the interplay between key system parameters, with results confirming the cooperative model consistently outperforms the non-cooperative approach so affording enhanced system flexibility in terms of FAP range expansion.

Use of Accelerometers in the Control of Practical Prosthetic Arms

Accelerometers can be used to augment the control of powered prosthetic arms. They can detect the orientation of the joint and limb, and the controller can correct for the amount of torque required to move the limb. They can also be used to create a platform, with a fixed orientation relative to gravity for the object held in the hand. This paper describes three applications for this technology, in a powered wrist and powered arm. By adding sensors to the arm making these data available to the controller, the input from the user can be made simpler. The operator will not need to correct for changes in orientation of their body as they move. Two examples of the correction for orientation against gravity are described and an example of the system designed for use by a patient. The controller for all examples is a distributed set of microcontrollers, one node for each joint, linked with the control area network bus. The clinical arm uses a version of the Southampton adaptive manipulation scheme to control the arm and hand. In this control form, the user gives simpler input commands and leaves the detailed control of the arm to the controller.