Dave Wisely

A 100 Mbit/s tracked optical wireless telepoint

This paper describes the design, construction and testing of a demonstration 100 Mbit/s tracked optical wireless telepoint system. The prototype uses switched linear laser and detector arrays, each imaged onto a small part of the total area, to allow wide coverage at high data rates. A separate tracking system monitors the relative mobility of nodes and switches the transceiver elements to maintain communication. A combination of operation at 1500 nm and a large number of switched laser elements (16) result in Class 1, eye safe, operation.

Broadband Radio Access for IP-based networks (BRAIN)-a key enabler for mobile Internet access

Second generation digital mobile radio systems have been very successful for voice communications and are now beginning to offer support for data services. Third generation mobile radio systems are currently being standardized worldwide to be initially deployed starting in 2001 providing support for multimedia applications with a flexible air interface and higher bandwidths. Wireless LAN technology is complementary to 3G systems and could be used to provide high bandwidth hot spot coverage, for example in railway stations and offices, for the emerging video and broadband services that will begin to emerge on fixed networks. The IST BRAIN project, which is partly funded by the European Commission, has been formed to solve the problems of providing seamless service for broadband users in these hot spots. This paper describes these problems in greater detail as well as outlining how the BRAIN project is tackling them.

A Novel Micro Mobility Solution Based on Media Independent Handover and SIP

Media Independent Handover (MIH) is a technique proposed by the emerging IEEE 802.21 standard that provides solutions for seamless handover across heterogeneous networks. The IEEE standard provides link layer intelligence information to upper layer to optimize handover between networks of the same type as well as handover between different network types. Session Initiation Protocol (SIP) is becoming the leading protocol for multimedia call control in IP networks and is expected to be widely deployed in the near future. The existing SIP infrastructures and signalling could be optimized to provide a good solution for mobility support. In this paper we introduce the concept of MIH and propose a solution for vertical handover of a multimedia session based on SIP with the triggers being provided by MIH for efficient terminal mobility management in a SIP environment.

Multi-rate power-controlled link scheduling for mesh broadband wireless access networks

The problem of multi-rate power-controlled collision-free scheduling in spatial time division multiple access (STDMA) wireless mesh networks is formulated as a mathematical program utilising cross layer information. As these mixed integer linear programs are intractable (NP-hard problems), optimal collision-free schedules can be found only for topologies consisting of a few nodes. To this end, approximation algorithms that are based on linear programming relaxation and randomised rounding are studied. The proposed framework, which aims to maximise the spatial timeslot reuse under predefined signal-to-interference noise ratio thresholds, is suitable for providing centralised scheduling in the mesh mode of the IEEE 802.16 standard. Performance aspects of the approximation algorithms under different scenarios are investigated.

BRAIN—an architecture for a broadband radio access network of the next generation

The tremendous growth rates of the Internet as well as the area of mobile communications give rise to the chance that the mobile Internet is most promising by combining both the Internet and mobile communications. These prospects are the motivation for the European research project BRAIN (Broadband Radio Access for IP-based Networks), which is developing an open architecture for a broadband wireless mobile access network offering an integrated communication platform across heterogeneous networks and, thus, goes beyond current third generation systems and towards the mobile Internet. The project covers three major technical areas: support of seamless service provision in a mobile environment; the design of an IP-based access network that will support non-cellular technologies such as wireless LANs; and requirements of a broadband air interface suitable for hot spots. BRAIN is going to integrate HIPERLAN/2 with UMTS by means of an IP access network. The work is guided by a user-centric top-down approach ensuring that user functionality is the key driver of the project. This article will focus on that part of the BRAIN work which specifies the main interfaces of the BRAIN architecture and deals with aspects related to the support of Quality of Service and mobility. Copyright

Sharing your Urban Residential WiFi (UR-WiFi)

Cheap and ubiquitous broadband wireless access is what most of the operators are aiming for. This paper analyses an innovative proposal to extend the traditional fixed coverage offered by residential broadband into an urban wireless coverage using urban residential wireless fidelity (UR-WiFi) project. UR-WiFi assumes that by giving some incentive, the broadband customer would extend his surplus broadband and wireless bandwidth for public usage. The study performs a feasibility study of coverage, capacity and interference modelling based on different 802.11x technologies. In-depth technical analysis is complimented with detailed analytical and experimental data and is extrapolated on a countrywide basis. Based on results, we believe UR-WiFi provides a viable option for next generation broadband wireless access

Impact of EIRP Limit Changes on the Performance of 2.4 GHz WiFi Systems

This paper addresses whether or not an increase in the equivalent isotropic radiated power limit would benefit WiFi performance in typical UK urban environments. Using simulation, it compares two types of system: one that is designed to provide blanket coverage and another that is a random collection of home networks. It also considers their impact on each others performance for a range of home network deployment densities. It is shown that when both types of network co-exist the average downlink throughput performance can be improved by increasing the UK regulatory limit from 20 to 27 dBm. However, this improvement decreases with network deployment density and ranges from approximately a twenty percent improvement at the lowest density to a negligible one at the highest. Uplink performance is not considered.

Radio access networks beyond 3G: a first comparison of architectures

We consider the role and possible architectures of access networks in systems beyond the current third generation. We consider the motivations for defining specialised infrastructure to support mobile radio access, and look at the various criteria for determining the scope of such systems. We then introduce and compare the access network architectures of four widely varied IST projects, BRAHMS, BRAIN/MIND, DRiVE and WINEGLASS. We compare the different approaches that these projects have taken, and conclude with a view on how this can provide a pointer to future access network architectures.

Paving the road to systems beyond 3G - the IST MIND project

In systems beyond 3G mobile access will be considerably more diverse than is currently the case with highly integrated cellular technologies. Complemented with new access technologies, such as wireless LANs, future mobile systems will offer a different mix of bandwidth, cost and coverage. There will also be extensions to traditional wireless access networks - both by operators with wireless routers and by users forming ad-hoc networks that attach at the fringe of the access network. Creating services and delivering multimedia over these networks is a very real technical challenge. In this paper the overall approach of the IST MIND project to tackling these issues is described. Further the rationale for an IP-based architecture and how it is being extended to encompass new access concepts of wireless and mobile routers is detailed. Finally the paper looks at how we are enhancing WLAN systems to give greatly increased performance for systems beyond 3G.

Non-Independent Randomized Rounding for Link Scheduling in Wireless Mesh Networks

In this paper, a family of integer linear programs is formulated for performing collision free scheduling in Spatial-TDMA wireless mesh networks. We extend previous formulations for power aware STDMA scheduling to include discrete power transmission and multi-rate support via adaptive constellation selection. Despite the theoretical attractiveness of these (mixed) integer linear programs, STDMA scheduling problems are in general intractable (NP-hard problems). Thus, the practicality of providing optimal solutions is rather limited. To this end, we study approximation algorithms that are based on linear programming relaxation and randomized rounding. Based on these approximation algorithms we focus our study on the trade-off between optimality of the solution and feasibility. Conducted numerical investigations aim to vindicate the claim regarding the strength of randomized algorithms. In that respect the performance of the approximation algorithms under different scenarios, such as the number of active links and number of nodes in the mesh network, is investigated.