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Executive Summary

Introduction

This report provides an overview of the technology research and development programme at Ofcom. It presents key findings and outlines the conclusions and implications that Ofcom has drawn from this work.

Ofcom intends to publish an overview of technology research and development on an annual basis to inform stakeholders of findings and to solicit feedback on both the results and the direction of the programme.

Context

Ofcom regulates a sector where technology developments are key to delivering new applications and services to the consumer. Technology development can be both facilitated and hampered by regulatory policy. Ofcom must therefore take a forward view to understand the benefits and impact that emerging technologies may bring and inform appropriate regulatory action. It is one of Ofcom’s statutory duties to encourage the most efficient use of the radio spectrum, so the research effort aims to investigate the technologies which can help to achieve this.

Most visions of the future foresee dramatic increases in the amount of information sent wirelessly. However, the areas of the radio spectrum that can be used for this kind of transmission expand slowly. Only by making better use of the radio spectrum can the visions be achieved. For example, broadcasting content to mobiles may require greater spectrum efficiency; in the future this could be provided by Mesh networks or using adaptive antenna technology. By understanding potential future developments, Ofcom can determine how technologies and services might develop and shape regulation policy accordingly. Hence the technology R&D programme is focused around understanding and furthering the fundamental building blocks for a whole raft of new technologies and services.

Ofcom’s technical research programme is divided into three strands:

• Understanding and furthering emerging technologies , such as Software Defined Radio and Smart Antennas. This will allow Ofcom to develop an appropriate regulatory environment to enable future developments.
• Understanding the state and use of the spectrum, by monitoring its quality and usage. This will allow Ofcom to look at ways of enhancing efficiency and ensure that spectrum is not becoming progressively polluted by interference.
• Enhancing spectrum efficiency , for example looking at options for improving the use of spectrum by existing radar systems. This will help to ensure there is sufficient spectrum to allow for the envisaged growth in usage.

While Ofcom is the regulator for the UK communications industries, with responsibilities across television, radio, telecommunications and wireless communications services, this research programme is deliberately biased towards radio spectrum. This is because spectrum underpins the operation of broadcasting, fixed and wireless telecommunications systems.

Emerging technologies

The work in this area has covered an investigation of Software Defined Radio, Smart Antennas, Cognitive Radio and wireless Mesh networking. The potential impact of these technologies on the spectral efficiency of future systems is significant. To varying degrees each of these technologies today exist in some form. However, there are still technical hurdles to be overcome.

Software Defined Radio

Many future visions of wireless communications involve multi-modal devices connecting to a wide range of different networks such as 2G, 3G, WiFi and Bluetooth. At present this is achieved by incorporating the chipsets from each of the different standards, e.g. 3G and Bluetooth, into the handset. While such an approach works, it is relatively expensive and inflexible. An alternative is for communications devices to be designed like computers with general purpose processing capabilities and different software for different applications. Such devices could then call up, or download, the appropriate software for the particular communications requirement currently in use.

The underlying architecture needed to achieve this is termed Software Defined Radio (SDR). In the future this flexibility might enable more efficient use of the available spectrum through rapid deployment of the latest radio technologies.

To date the defence industry has been the main sector to explore SDR. It is, for example, being deployed as part of the US Joint Tactical Radio System programme. The cellular industry is now showing an interest in using SDR in base stations. SDR could help to make the equipment more ‘future proof’, allowing operators to more rapidly introduce new technologies and services and allow manufacturers to fix bugs and add new features post-manufacture.

Work commissioned by Ofcom has confirmed the potential benefits of SDR but has found that there are many issues with its implementation. They include difficulties in implementing antennas, the speed of chipsets, the battery power required and cost. This has led Ofcom to conclude that SDR is a promising technology but it will be gradually implemented, starting with devices that are able to download minor protocol changes, likely around 2008, through to devices that are able to make major changes to the radio solutions, which could become available in 2015.

Smart Antennas

Smart antenna technology has the potential to significantly increase the efficient use of spectrum in wireless communication applications.

Simple antennas radiate the communications signal equally in all directions. This is wasteful because only a small amount of the signal reaches the intended user; the signal that is radiated in other directions can also cause interference to other users.

Smart antennas intelligently direct the communications signal at the user. The technology has the potential to increase the range and capacity of transmission equipment and reduce interference with other devices.

Smart antennas have been used for many years, notably in defence radar and sonar. Low volume production of such systems has meant that the cost of smart antenna technology has remained high. Significant advances in, for example, processing power are now bringing the technology closer to being commercially viable in the near future for civil communications applications.

Smart antennas could be used to meet the demand for higher bandwidths in future mobile communications systems which operate in the highly-congested area of the radio spectrum. With many systems running close to their theoretical limits of performance, realising the capabilities of smart antennas offers the prospect of performance improvements without placing more demands on the spectrum.

However, there are a number of issues that are restricting the widespread adoption of smart antenna technology, including:

• technical – mainly hardware constraints;
• business – the current relatively high cost of deployment often outweighs the benefits; and
• standards – standards bodies have been slow to agree a global consensus.

For mobile handsets, smart antenna deployment would be complex and expensive. The business case for this application is uncertain at present. For wireless Local Area Network ( LAN) applications where the size, power and processing complexity constraints are relaxed, access points with smart antennas have a stronger business case and early versions are now available on the market.

A semi-smart approach - where the communications signal from an antenna is broadened to a sector rather than a narrow beam - would be simpler and cheaper to introduce. Therefore, the business case is stronger and the technology could be introduced within the next three to five years.

Cognitive Radio

Not all the spectrum is in use all of the time. Cognitive Radio is a technology that could make efficient use of unused spectrum, potentially allowing large amounts of spectrum to become available for future high bandwidth applications.

Most of today’s radio systems are unaware of their spectrum environment - they are designed to operate in a specific frequency band. A Cognitive Radio system senses and understands its local radio environment to identify temporarily vacant spectrum to operate in. Cognitive Radio would hop into unused bands of the radio spectrum and hop out again if a primary user of a band required that spectrum.

Although the technology holds much promise its introduction might require a different approach to spectrum regulation – this was discussed in Ofcom’s recent Spectrum Framework Review. There are also technical issues to be overcome to ensure that primary users of a band are protected from interference.

There are currently no Cognitive Radio systems in wide deployment, although some early demonstrations of the technology have been built and some existing systems such as DECT cordless phones make use of much simplified Cognitive Radio principles.

Ofcom’s studies in this area are just commencing and no firm conclusions have yet been reached. The work undertaken into SDR suggests that flexible, multi-protocol, multi-band Cognitive Radio systems are some way off. Handsets employing this technology are unlikely before 2010. In the interim there is the possibility of specific band sharing technologies emerging which would provide a stepping stone towards the full Cognitive Radio vision.

Wireless Mesh Networking

In a Mesh network every user connecting to a particular wireless communications network acts as a node, relaying information for other users as well as transmitting and receiving its own data. In Mesh networks, information can be transmitted from one user to another via multiple hops through the nodes. Such a network can contain just a few nodes or thousands, all exchanging data.

The advantages of Mesh networks include:

• new communications networks can be formed without the need for new network infrastructure;
• they potentially make more efficient use of spectrum;
• they can extend coverage of cellular and other networks by allowing terminals on the edge of a coverage zone to relay signals to those who do not have coverage; and
• they can be entirely unplanned.

The military already makes use of Mesh networks for battlefield communications. The technology is now beginning to be adopted to provide commercial wireless services using Mesh WiFi technology. Systems already exist in several US metropolitan areas to provide municipal low cost broadband services or in some cases for improved communications for emergency service crews.

Ofcom’s work has concluded that wireless Mesh networks will work best when they are incorporated with some level of fixed infrastructure, for example connections to the telephone network and the internet, or alongside existing networks, such as cellular. This type of Mesh would support applications such as extending wireless hotspots filling in areas of poor wireless coverage, the provision of broadband networks and internet in rural communities.

Understanding the use and quality of our spectrum

If Ofcom is to effectively manage the radio spectrum then it requires detailed information on the quality of spectrum and how it is used.

Quality information allows Ofcom to understand the degree to which the spectrum is being “polluted” by interference from sources such as unwanted emitters.

Usage information allows Ofcom to understand how intensively the spectrum is being used, helping to judge, for example, whether the licence-exempt spectrum is becoming congested. It might also provide information on which judgements about the introduction of new technologies can be made, or allow Ofcom to quickly detect and locate sources of illegal transmissions, such as pirate radio.

To understand spectrum quality Ofcom has commissioned the development of a portable and automated system which can measure the amount of interference compared to actual signal strengths across a wide band from 100 MHz to 10.6 GHz. This will allow detailed analysis of the spectrum use and levels of interference across the most heavily used and demanded frequencies. It will also allow the interference from new systems which generate noise-like signals, such as Ultra Wideband, to be monitored. This system, called the Autonomous Interference Monitoring System (AIMS), will be tested and completed in early in 2006.

To understand spectrum usage Ofcom has commissioned the design of several prototype Automatic Monitoring Stations ( AMS). These are being developed to demonstrate the feasibility of deploying a network of monitoring systems across the UK to provide real-time information on spectrum usage. Such a system would allow Ofcom to rapidly detect and locate sources of illegal transmissions, such as pirate radio. It would also provide valuable information on how intensively the spectrum is being used and provide information on which judgements on the introduction of new technologies such as Cognitive Radio can be made.

Enhancing spectral efficiency

Demands from new communications technology and services are putting pressure on spectrum, which is a finite resource. Therefore, Ofcom’s research programme has examined whether new technology can make more efficient use of this resource.

The work in this area includes:

investigating whether the spectral efficiency of radar systems can be improved;

• considering whether there is potential for communications applications to be deployed in the little used high frequency bands; and
• examining whether there are opportunities for sharing spectrum.

Spectrally efficient radar systems

In the frequency band between 1GHz and 3GHz around 30% of the spectrum is primarily allocated to radar systems. This is largely unavailable to other users of the spectrum but these frequency bands have very desirable properties which could be used to support other communication services, such as cellular telephony, messaging and wireless LANs. Large amounts of spectrum could potentially be freed up for commercial purposes if the spectral efficiency of radar systems was improved, moved to a different frequency band in lower demand, or shared with commercial users.

Carrier Wave radar has been identified as a technology that in the longer term could dramatically increase the spectral efficiency for some radar applications, such as Air Traffic Control. Conventional radar systems use very narrow pulses to accurately detect the range of a target. They operate on relatively broad bandwidths of 10s of MHz. An alternative is to move to a continuous transmission, termed Carrier Wave. In principle, this would allow a bandwidth of just a few Hz, offering extremely high spectral efficiency.

However, there are a number of technical hurdles to overcome before Carrier Wave radars are practicable for deployment. They include the susceptibility of the systems to interference and the accurate measurement of target range.

Carrier Wave is unlikely to be retrofitted to existing radar systems so it must be treated as a new deployment. There are also technological, operational and cost hurdles to be first overcome and incumbent radar operators have little incentive to improve spectral efficiency either with short term or longer term measures. The long replacement cycle for existing radar systems means that a timescale for significant improvements in the spectrum efficiency of radar systems is likely to be 2025 or later.

Reliable Communications Systems at Frequencies above 60 GHz

The demand for spectrum in the highly congested lower frequency spectrum bands means that there is now a need to consider the higher frequencies for communications systems. If greater use of the bands above 60GHz could be made then this would provide a useful increase in the spectrum available for new services.

High frequency systems suffer much greater propagation losses making them unsuitable for long range applications. However, Ofcom’s research has shown that the higher frequency bands could be useful for a range of applications, including:

• Broadband Fixed Wireless Access (BFWA) with very high capacities. This could allow applications such as HDTV to the home to be deployed on demand;
• fixed line of sight point to point links, where link lengths of up to 5km are possible with 99.99 % availability, supporting short range backhaul;
• high speed (1GB/s) short range wireless LANs, operating over a range of a few hundred metres. This could be used to provide a wireless access system for large buildings such as exhibition halls; and
• short range repeaters (500m to 1km) with very high data rates of up to 5GHz for applications such as network backhaul. Such systems could be applied to a lamp post mounted system for the provision of high bandwidth backhaul to a city-wide WiFi network.

Ofcom’s research has concluded that higher frequency systems are possible within a five year timescale if technology developments, such as improved power generation, occur as expected. However , device costs may take longer to fall to acceptable levels to allow low unit cost production.

Improving the sharing of radio spectrum

Traditionally, radio services in the UK have been allocated spectrum on an exclusive basis to minimise any possibility of interference from other radio users. In certain cases secondary uses of the spectrum are allowed, but only where interference is judged unlikely. More frequency channels could be made available if successful sharing between different services could be achieved.

The research examined innovative methods for sharing the spectrum between multiple services in order to maximise its use. The most promising schemes are:

• beacons, which detect whether it is safe to share in a particular spectrum frequency;
• widespread frequency hopping, where spectrum users move across the entire spectrum allotment; and
• spectrum commons, which are rules and methods used for wireless communications .

The research suggests that there is little regulatory action required in the short term. In the five to 10 year timescale, when some of these technologies and services may be better developed, there may be beneficial courses of regulatory action.

Overall Conclusion

We have discussed a number of interesting technologies that promise enhanced spectrum efficiency and improvements in device implementation, but broadly, as we would expect at this stage of research, these are around a decade away from commercial realisation.Much of our research is still ongoing, and while we have researched all the leading contenders for spectrum efficiency improvements there may be other technologies that we are not aware of and new technologies are likely to emerge over time. Given these caveats, we tentatively conclude that unless other technologies emerge which are rapidly developed and deployed, then dramatic enhancements in spectrum efficiency will take a decade or longer to achieve. This is an important conclusion which will have major implications for spectrum use and research over the coming decade.

This does not imply that no enhancements are possible in the next decade – there are many deployed systems which are not using the most advanced existing technology. For example, upgrading existing 2G networks to 3G would provide a gain of around three-fold in spectrum efficiency. Also, many new services can be introduced without dramatic improvements in spectrum efficiency. Finally, major change in services often take five to 10 years – the same timescales as the emergence of the technologies we have discussed here. Hence, we are encouraged that developing technology will continue to underlie developments in wireless systems.

Next Steps

Ofcom’s research programme has focused on emerging technologies and improving the use of the radio spectrum. In the next 12 months Ofcom’s research will explore:

• possible mechanisms for spectrum sharing between the Government and private sector users;
• the role of licence-exempt spectrum; and
• the continued development of monitoring systems to provide information about the radio spectrum.

The full document is available below

• Technology Research Programme: Research and Development at Ofcom 2004/05 [pdf]
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