drivers for cognitive radio – part...

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Cognitive Radio & Dynamic Spectrum AccessIntroductory Lectures

Drivers for Cognitive Radio – PART 1

Linda Doyle, Allen Mackenzie, Luiz Da Silva

focus

• Allen & Luiz will have introduced the basic concepts of cognitive radio

• The purpose of these slides is to look at the applications driving the research in the field – Luiz has mentioned some in passing already.

at the end of this lecture you will be expected to understand the main application areas that are currently driving cognitive radio, begin to discuss the feasibility of these areas and envisage other potential areas …..plus the added bonus of being able to say the phrase“mobile phone” …..

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why bother with cognitive radio?

over complicatedsolution? wisdom – specific

targeted solution betterthan one that fits

everything?

huge costs?

do we really needit?

software radiostill struggling?

why bother with cognitive radio?

over complicatedsolution? wisdom – specific

targeted solution betterthan one that fits

everything?

huge costs?

do we really needit?

software radiostill struggling?

so what are the drivers of cognitive radio?

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general answer

we need cognitive radio for two main reasons

1. there are things we will not be able to do without it.

2. there are other things we can do already but will be able to do much better with it

whether any of these ‘things’ are worth doing in the first place is for you to decide

Can’t Do WITHOUT it

dynamic spectrum accessopportunistic use of spectrum

general new paradigms for spectrum management

truly self-organising networks, self planning networks

real commercialisation of ‘concepts’ that are out there but not yet used

Can Do Better WITH it

spectrum commons regimesspectrum property rights

interference mitigation / coexistence of different systems

exploitation of complex systems such as MIMO type communication systems or even full exploitation of ad hoc

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commercial, public safety and military aspects to all of these

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"The wireless telegraph is not difficult to understand. The ordinary telegraph is like a very long cat. You pull the tail in New York and it meows in Los Angeles. The wireless is the same, only without the cat." - Albert Einstein

to the end use the fact a cognitive engine is at work may not at all be obvious other than knowing that you will be able to hear the meow no matter what …..

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“I see the emergence of a new discipline, called cognitive dynamic systems, which builds on ideas in statistical signal processing, stochastic control, and information theory, and weaves those well-developed ideas into new ones drawn from neuroscience, statistical learning theory, and game theory. The discipline will provide principled tools for the design and development of a new generation of wireless dynamic systemsexemplified by cognitive radio and cognitive radar, with efficiency, effectiveness, and robustness as the hallmarks of performance”.

how I will tackle this

• I will begin by looking at spectrum regimes as principles of these manifest themselves in the other drivers for cognitive radio …..

• I will then move on to interference mitigation/coexistence/truly self organising systems

• I will look at public safety, military and commercial opportunities

• I will do some today and finish next week

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Existing Spectrum Management Regimes

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what has the Titanic got to do with anything?

• The Californian, a passenger ship, was within sight of the titanic, but failed to acknowledge the distress flares of the Titanic, or turn on its own wireless.

• The passenger ship Carpathia, fifty-eight miles southeast of the Titanic, responded to the distress call and rescued seven-hundred and five survivors adrift in lifeboats. The other fifteen-hundred passengers, having no lifeboats available to them, succumbed to the cold sea.

• Wireless for signaling distress was incidental. The multitude of ships in categories other than passenger carrying, had no purpose to be equipped with wireless This was the sentiment of the period.

so then …..

• The "Safety of Life at Sea" Conference was held in London, November 12, 1913 attended by the sixty-five countries. This conference was the turning point of communications as we know ittoday. Sweeping regulations were put into effect governing all ships at sea, whether motor propelled or under sail.

• Further regulations followed governing spectrum in general.

• The (amended) Wireless Telegraphy Act 1926 is the principal legislation governing the licensing and use of the radio spectrum in Ireland.

much of what our regulations on based on today actually stems from the 1920s

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• The system for management of spectrum that is currently mainly in use is known as Command & Control

• Suggests tight control on the part of the regulator.

• Huge focus on “the apparatus”

Command & Control (1)• Highly prescriptive management of the radio spectrum.• The entire radio spectrum is divided into blocks, or bands, of

frequencies established for a particular type of service by the process of frequency allocation.

• Frequency allocation is performed on an international and national basis.

• The ITU's International Radio Regulations allocates the spectrum from 9 kHz to over 275 GHz to a range of different uses. In Europe the EU has a further say! Will learn more in later lectures.

• At national level typically a national regulatory authority (NRA) manages the day to day use of the spectrum

• The national regulatory authority can make more specific channelplans. For example, allocations made to the land mobile service can be divided into allotments for business users, public safety users, and cellular users.

COMREG is the Irish NRA, the FCC in the USA and OfCOM in the UK

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Command & Control (2)

• Frequency assignment, which happens at national level, refers to the final subdivision of the spectrum in which the spectrum is actually assigned to a specific party for use.

• Wide range of mechanisms for assignment: first come, first served, free allocations, beauty contests, limited use of auctions, other procedures

• LICENSES are assigned.• Key point: Licenses have tended to be very specific

detailing what kind of services can be delivered and which kind of technologies should be used to deliver the services.

specified technologies, specified services

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advantages

The control of interference is easy to manage

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some disadvantages

• slow and static• no spectrum left • favours incumbent• regulators need to pick service and technology winners• can result in inefficiencies• impossible to put a real value on spectrum

disadvantages

• slow and static• favours incumbent• regulators need to pick service and technology winners• can result in inefficiencies• impossible to put a real value on spectrum

LOTS OS CHALLENGES TO THIS SYSTEM

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challenge 1

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SO

• ONLY 5%-10% OF SPECTRUM USED AT ANY ONE TIME

• WHY CAN’T WE SHARE?

overlay underlay?

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• This is known as Dynamic Spectrum Access – users don’t get a static allocation of spectrum.

• They dynamically access whatever is available. Sometimes I use the phrase opportunistic use of spectrum.

• In context of sharing with existing regime we think of the current license holders as PRIMARY users

• We think of the new users as SECONDARY users.

• The secondary users can share with the primary users.

• In much of the literature the secondary users are considered to be UNLICENSED users. However this is by no means a necessity and there could be some kind of licensed secondary users.

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current regime

overlay: opportunistic use

underlay: easement use

secondary (unlicensed?)white space

primary licensed

secondary (unlicensed?)grey space

• In the slides so far we looked at finding opportunities to operate on the basis of sharing with users who had this primary right.

• It is also possible to imagine a world in which all the users access the network dynamically and new entrants work around existing users and move to ‘better’ spectrum if existing users go off the air.

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first arrivals

overlay: opportunistic use

underlay: easement use

later arrivalswhite space

later arrivalsgrey space

The Act of Fitting in the White Space is Quite Tough

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The Act of Fitting in the Grey Space is Quite Tough

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The US Federal Communications Commission, in 2002, chartered an internal study, the Spectrum Policy Task Force, to investigate the future needs of RF spectrum and the limitations of current spectrum policies, as well as develop recommendations for enhancing current policies. The suggestion of a common interference metric was one of the outcomes of the task force. The proposed metric was termed the Interference Temperature. The Notice of Proposed Rule Making, ET Docket No. 03-237, details the ideas involved.

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FCC in May 2007 came to the following conclusions,

• Commenting parties generally argued that the interference temperature approach is not a workable concept and would result in increased interference in the frequency bands where it would be used.

• 1. While there was some support in the record for adopting an interference temperature approach, no parties provided information on specific technical rules that we could adopt to implement it.

• 2. Further, with the passage of time, the Notice and the record in this proceeding have become outdated.

• We are therefore terminating this proceeding without prejudice to its substantive merits. Accordingly, IT IS ORDERED that, pursuant to Sections 4(i) and 4(j) of the Communications Act, 47 U.S.C. 154(i) and 154(j), ET Docket No. 03-237 IS TERMINATED, effective upon issuance of this Order."

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Cognitive Radio is the Technology to Deliver

• Need devices that can sense white space or understand what options are there for using grey space

• Need devices that can then shape the signal they transmit so as to fit in to the white space

• OBSERVE / DECIDE / ACT crucial to this issue.

you will have to possibly manipulate everything you can to make something fit, frequency power, antenna pattern, modulation techniques, coding formats …….basically completely manipulate the spatial and frequency footprint of the transmitted signal ……twist it into the form you want

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suggested underlay technology??

suggested overlaytechnology??

Allen will talk to you about cognitive network architectures in more detail.

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• white spaces – empty – can overlay on these

• grey spaces – not really full - can underlay

do you think there will be limits on the kind of applications that can be used?

• white spaces – empty – can overlay on these

• grey spaces – not really full - can underlay

• persistent white space

• temporary white space --- what are the technological limits?

do you think there will be limits on the kind of applications that can be used?

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where are the first possibilities for this approach?

TV White Spaces

“DIGITAL DIVIDEND”

• The Digital Dividend is the name given to the spectrum that willbecome free when TV channels switch from analogue to digital operation. This switchover has been mandated for 2012.

• Analogue TV uses large amounts of spectrum. For example, OfCOM, the UK regulators state that the five terrestrial television channels that currently broadcast in analogue in Britain (BBC1, BBC2, ITV, Channel 4 and 5) use nearly half of the most valuablebands of spectrum below 1GHz.

• Digital broadcasting is roughly six times more efficient than analogue, allowing more channels to be carried across fewer airwaves.

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• Broadcast television services in the United States operate on 6 MHz channels, designated 2 through 69, namely 54 - 806 MHz in the VHF and UHF portions of the radio spectrum.

• To replace the current channels with digital TV channels, requires less bandwidth, as mentioned above, with all the digital TV stations contained within channels 2 - 51.

• Hence once switchover is finished a portion of the spectrum, channels 52 through 69, namely 698 – 806 MHz, will be reallocated to other services. UPCOMING AUCTIONS WHICH WE WILL DISCUSS NEXT WEEK

• In channels the channels occupied by the digital TV stations, i.e. channels 2 - 51, in any given geographical area not all available channels will be used. The reason for this is that certain physical spacing is needed between each digital station to ensure interference won't occur.

• In addition, in some areas, not all of the channels that could be used by TV stations will be used. In most rural areas, there are more empty channels than occupied channels. Even in urban areas, a substantial amount of spectrum could be made available for wireless broadband.

TV WHITE SPACES

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sensing challenges

• Digital TV signals that are as low as -116 dBm, • Analog TV signals that are as low as -94 dBm and

wireless• microphone signals that are as low as -107 dBm.

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The Future is Bright, The Future is

Cognitive Radio

ledoyle@tcd.ie