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Showing posts with label Cognitive radio. Show all posts
Showing posts with label Cognitive radio. Show all posts

Wednesday, 11 April 2012

Whitespace Spectrum Management Issues

BT has been conducting a "White Space" trial in Isle of Bute, UK. Initial report suggests that the results are not very impressive. The following is from ISP Review:


Early feedback from BT’s trial of ‘White Space‘ (IEEE 802.22) wireless broadband technology on the Isle of Bute suggests that the service, which delivers internet access by making use of the unused radio spectrum that exists between Digital TV channels, still has a lot of problems to overcome, not least in terms of its sporadic performance.

In theory the 802.22 specification suggests that download speeds of up to 22Mbps per channel (Megabits per second) could be possible and some UK trials claim to have reached around 16Mbps, which is incidentally a long way off the UK’s chosen definition for superfast broadband (24Mbps+).
But separate reports from both PC Pro and the BBC today found that the service, which is complicated to deliver due to the ever changing spectrum and the risk of causing interference to DTV services, could struggle to deliver its top speeds.

At present BT’s implementation claims to be offering speeds of up to 10Mbps per channel, which will soon be upgraded to 15Mbps, but this reduces down to a maximum of just 4Mbps when 6km away from the transmitter. New tests at various points on the Isle of Bute showed speeds varying between just 1.5Mbps and 6Mbps (the latter was recorded within sight of BT’s mast).
In fairness White Space solutions are designed to target the last 10% of the UK where the government has so far only committed to a minimum download speed of just 2Mbps for all (Universal Service Commitment), which is a very low target. In addition White Space tech appears to deliver strong upload speed that is, in some cases, symmetrical. That makes it good for video conferencing and other upload dependent tasks.



As Fierce Broadband Wireless suggests, the low speeds could also be due to pre-standard gear that will just improve as time goes on.

The main reason for using this shared whitespace spectrum is due to the fact that the total amount of spectrum is limited and we want to make use of every available free spectrum to increase capacity of the overloaded networks.

Michael Fitch from BT recently spoke in our Cambridge Wireless Small Cells SIG event. The slide from his presentations neatly lays out the vision for shared spectrum.


In theory, even though this looks simple, in practice managing the database is a challenge by itself. The embedded slides below (Page 17 onwards) show the problems and the complexity associated with the database.
Time will tell how efficient and practical using whitespaces is.

Wednesday, 15 June 2011

Explaining the Alcatel-Lucent 'lightRadio' concept

Sunday, 10 April 2011

Cognitive radio – the way out of spectrum crunch?

Another presentation from the Cambridge Wireless Event on Avoiding Cellular Gridlock. One of the ways suggested in the discussions with regards to the 'Geo-location database' (see slide 12) is that they could also be done using Smart Grids. Though it sounds simple in theory, practically we may never see that happen and that would not be due to any technical reasons.

Thursday, 7 October 2010

Locating Wireless Devices Where GPS May Not Be Available

Some of you may have read my earlier posts on stealing spectrum via Femtocells and using Femtocells abroad illegally. This presentation tries to answer one such problem on how do you find the location where GPS cannot be used. This could also be used in case of Cognitive Radios. See my old blog entry here.

Thursday, 27 November 2008

SDR: Today and Future

I also got an opportunity to attend the SDR briefing in LTE World Summit. There were many interesting presentations including one titled "SDR in Mobile Devices" by Thierry Dubois, SDR Market Analyst, IMEC, Belgium. Infact last year I blogged about SDR from Imec presentation as well. The following is an extract from Thierry's presentation:

The key benefits of SDR are as follows:
  • Reducing the Bill Of Materials (BOM)
  • Lower development costs
  • Facilitate better reuse of intellectual property (IPR)
  • Possibility to upgrade products already in the field
  • Enabler of the Cognitive Radio vision
There are three main areas where SDR's are required but some problems exist as can be seen from the diagram above.
  • Flexibility is the key for baseband. Some of the common signal processing blocks may not be reusable. This means that though some protocols can easily be defined for a particular baseband, others may not be possible for that baseband. Good progress is still being made though on this front.
  • Reconfigurable RF is some way away, further down the road.
  • The biggest challenge is the antenna interface for which no proper solution exists. Some solutions being worked on right now include MEMS based solution, Carbon nanotubes, Special ceramic materials, etc.
The next step after SDR is cognitive radio (CR). The main advantage for using CR would be because spectrum is over-allocated but under-utilised. There are lots of white spaces in the spectrum that could be utilised by devices intelligently of their own.

Cognitive Radios are defines as: A radio that can autonomously change its parameters based on interaction with, and possibly learning of, the environment in which it operates. Through appropriate radio resource management, such a cognitive radio should make flexible and efficient use of network/spectrum resources.

CR would consist of Intelligent Sensing hardware and Intelligent Sensing Algorithms. There are two types of CR being considered:
  • Opportunistic Radio: A radio that co-exists with other systems using the same spectrum. E.g., White Space Devices
  • Smart Reconfigurable Radio Systems: A radio that makes flexible and efficient use of network/spectrum resources across heterogeneous environments. Seamlessly roaming possible on different networks, countries, frequencies, etc. It requires true paradigm shift i.e., spectrum liberalization
An Introductory paper on SDR is available on Bitwave Semiconuctor website.

Monday, 18 June 2007

Cognitive radio


Cognitive radio (CR) is a newly emerging technology, which has been recently proposed to implement some kind of intelligence to allow a radio terminal to automatically sense, recognize, and make wise use of any available radio frequency spectrum at a given time. The use of the available frequency spectrum is purely on an opportunity driven basis. In other words, it can utilize any idle spectrum sector for the exchange of information and stop using it the instant the primary user of the spectrum sector needs to use it. Thus, cognitive radio is also sometimes called smart radio, frequency agile radio, police radio, or adaptive software radio,1 and so on. For the same reason, the cognitive radio techniques can, in many cases, exempt licensed use of the spectrum that is otherwise not in use or is lightly used; this is done without infringing upon the rights of licensed users or causing harmful interference to licensed operations.

The only difference with SDR (Software Defined Radio) is that a cognitive radio needs to scan a wide range of frequency spectra before deciding which band to use, instead of a predefined one, as an SDR terminal does. One of the most important characteristic features of an SDR terminal is that its signal is processed almost completely in the digital domain, needing very little analogue circuit. This brings a tremendous benefit to make the terminal very flexible (for a multimode terminal) and ultrasmall size with the help of state-of-the-art microelectronics technology.

More Information at: