Feb 18 2011

Key Experiences from ‘Cognitive Radio Standards and Market 2010′

In end 2010 I attended the workshop on Cognitive Radio Standards and Market (CRSM) 2010, where I also gave a talk about a business case study for a cognitive radio system based on a wireless sensor network carried out in the SENDORA project. The workshop is yearly arranged by IBBT with Pieter Ballon and Simon Delaere in cooperation with MIT with William Lehr. The key takeaways from this event are the status and different views on the main cognitive radio enablers:

  • geo-location database
  • sensing
  • cognitive pilot channel (CPC)

When comparing the three cognitive radio enablers it can be summarized that the geo-location database approach is the most supported one, the sensing approach still seems to be promising but technology must evolve in order to become secure enough, and at the moment there seems to be little support for the CPC approach. However it should be mentioned that the three approaches will have different value depending on the specific application of cognitive radio, (eg. TV White Spaces (TVWS), grey spaces, spectrum sharing). Simon Delaere discussed the geo-location database and CPC approaches, and he mentions that databases might have to meet the CPC half way. The database approach is by no doubt the cognitive radio enabler that is most debated these days and also the one that seems to reach the market first. This is first of all due to the recent move by the US regulator FCC on September 23 to allow usage of the TVWS by accessing a geo-location database without the requirement of spectrum sensing. This is also due to the same approach by the UK regulator OFCOM. FCC also appointed nine datbase administrators early in January and Spectrum Bridge already has an operating TVWS database.

The FCC and OFCOM approaches was compared in terms of database design, where it was discussed whether it is best that the market designs the database system as proposed by FCC or if the regulator designs the database system such as proposed by OFCOM. It was stated that the former is beneficial in order to achieve the most optimized database system whereas the latter is beneficial in order to achieve harmonization between countries. Hence, maybe the first is best for the US and the second is best for Europe? Sofie Pollin (IMEC) and Vânia Gonçalves gave an interesting talk on the value of sensing for TVWS where they also debated the database systems and states that currently the database approach is more reliable than sensing. It should also be noted that sensing is promising and will be able to detect more white spaces.

It was also some discussion around that OFCOM is progressively making its own approach without harmonizing with the rest of Europe and leaving the rest of Europe behind, whereas most stated that this is positive since a harmonized European approach will take long time to establish due to coordination between many countries. From OFCOMs statement on cognitive access in the digital dividend it is noted that they are considering European harmonization and are active in the CEPT groups SE43 and SE42.  It is also a good thing that the database approach for TVWS access is being tested before being standardized in the rest of Europe and globally. However, Europe faces a bigger challenge than the US when allowing usage of TVWS due to interference at all the country boarders in Europe and the fact that many regulators have to coordinate and harmonize. An interesting  presentation and overview of European regulation was given by Benoist Deschamps from the French regulator which is especially seeking input on when the market is ready for cognitive radio among other issues.

Paulo Marques from the COGEU project presented results from a measurement campaign of TVWS in Munich, Germany, which showed that there are many available channels for TVWS access both for using consecutive channels or only one (report).

As mentioned in a previous blogpost the operator Orange are intensively following cognitive radio and at CRSM 2010 Wladimir Bocquet gave a talk including views on TVWS, but also about other aspects of cognitive radio: optimization of radio access network performance, femto cells, refarming and relay performance. He also concluded his presentation by saying that cognitive radio not should be allowed for use in licensed bands used by existing networks and infrastructures without the consent of the respective license holder. This raised discussions and confusion since it somehow contradicts with TVWS access. However, this also emphasizes the fact that operators are careful with cognitive operation in mobile and cellular bands due to interference, which also is the concern of TV broadcasters. Anyway, mobile and cellular bands are among the best exploited bands and hence there are not that much white spaces in these bands.

In my presentation about a business case study for a cognitive radio system based on a wireless sensor network, we show that it is possible to make business when deploying a sensor network both as external sensors and for sensors embedded in terminals. The business case study is from 2015 to 2020 and the parameter assumptions are uncertain. Therefore it is important to note that the main value of this business case study is for research purposes to identify the critical aspects for profitability, so that the technical R&D work can focus on them. Two of the most critical parameters were the sensors price and the sensor radius which is important for the amount of sensors needed. It was also found that it is important to plan the network such that as many existing base station sites as possible are reused since establishment of new sites is costly. The full study will be presented at DySPAN 2011.

Sep 24 2010

5 Most Promising Applications for TV White Spaces

Recently, FCC officially opened for TV white space spectrum, now without the strict requirement of sensing in the terminals. Interestingly, Ofcom in the UK also seem to take a similar approach. There is much discussion about which applications that will be used in the TV White Spaces (TVWS) and trials have been launched among others by Google. Obviously we have rural broadband and super-WiFi, but there are many others. In fact, most generally used applications for wireless communications could potentially be used in TVWS, but the big pros with the TVWS are the great propagation characteristics which provide for great coverage and also the relatively great bandwidths.  However, some applications are more attractive than others when considering commercial and technical aspects. Therefore I provide a ranked list of 5 promising applications in the TV White Spaces:

  1. Wide area coverage in rural areas (e.g. IEEE 802.22): This has great potential since there especially exist much white spaces in the rural areas. Also, TVWS has perfect characteristics for this applications where propagation effects give high ranges and there are relatively wide bandwiths of 6, 7 or 8 MHz in US, Asia and Europe respectively. Broadband to rural areas might therefore be provided very cheap.
  2. Hotspot/low-power broadband (e.g. IEEE 802.11af): Since the much used 2.4 GHz band for WiFi is quite congested in urban areas, IEEE 802.11af also called super-WiFi will probably be used in the unlicensed TVWS. In some urban areas there does not exist much white spaces for high power systems such as (1) above, but there could be potential for low power broadband systems such as for WiFi hotspots that exploit smaller portions of TV white space.  Femto-, pico and micro-cells for wireless broadband in TVWS are other examples, but these are not naturally unlicensed such as WiFi.
  3. Backhaul for WiFi in hotels, campuses, businesses (WiFi could be IEEE 802.11af or IEEE 802.11a/b/g/n): When WiFi is installed in hotels, campuses or business the greatest challenge is often the cabling to provide internet connectivity to the WiFi access points. By using TVWS as backhaul for WiFi access points in such installations we could avoid the costly, time consuming and challenging cabling issues. This is due to the propagation effects in the TVWS where radio signals better penetrates building walls and floors.
  4. Connectivity for security cameras (example):With TVWS it will be easier to install security cameras anywhere with lack of connectivity.
  5. Remote monitoring (power plants, patients, metering, …): Due to the propagation effects of TVWS it will be easy to provide access to power plants far away, and to patients far away and moving around potentially in the basement where signal loss is severe, but connectivity achievable with TVWS.

Other domains of interest for TVWS applications that could be mentioned are ad-hoc networks  (e.g. internal sensor network or mesh network communication), healthcare applications, vehicular communications and cellular networks offloading.

Aug 31 2010

IEEE 802.11af vs. IEEE 802.22

The first cognitive radio standard IEEE 802.22 that started standardization in 2004 approaches its final release after some years of standardization. Why is it going so slow recently and why is there no push from the industry, or are these statements wrong? Is “fixed broadband in rural areas based on cognitive radio” not that attractive to most operators, hence no massive push from the manufacturers to develop equipment.  Is the business case for fixed broadband in rural areas really positive when considering the risk of using access technology based on cognitive radio. Does there exist any initiatives to build an ecosystem around IEEE 802.22? In total, maybe cognitive radio is too immature and uncertain for the industry to make investments. However, it would certainly be interesting to see a realistic business case for IEEE 802.22.

Another standard which emerges is IEEE 802.11af, which will provide services similar to the traditional IEEE 802.11 standard, also known as WiFi when certified by the WiFi alliance. The main difference from the well known IEEE 802.11a/b/g standards is that IEEE802.11af will be a based on cognitive radio for operation in the TV White Spaces, that is the spectrum already allocated to the TV broadcasters and at the same time not used. No big investments are necessarily required in order to install and use a WiFi access point which actually can be done by everyone. The only prerequisite, when the regulatory rules are in place such as in the US,  is the need for an incumbent database that maintains data about used frequencies in the TV band.  Google has already announced that hey want to operate such a database. Rumors also say that WiFi alliance will certify IEEE 802.11af, which then will be WiFi, just based on cognitive radio.

The WiFi alliance which certifies WiFi products will be important for the success of IEEE 802.11af. In contrary, to my best knowledge, no such forums or alliance exist for IEEE 802.22. Maybe WiFi alliance could be the success factor required for the first commercialization of a cognitive radio technology in the TV white spaces, namely IEEE 802.11af. Also, rumors say that IEEE 802.11af only considers the minimum required cognitive functions for the first certified product, thus focus is on getting the standard released ASAP and then get products certified before FCC withdraws the rules. For later releases, more advanced functions could be introduced. This is similar to the IEEE 802.11b/g/n story.

In summary, maybe IEEE 802.11af will be seen commercially before IEEE 802.22 due to the speed of standardization and the ecosystem inherited from the WiFi alliance, even though IEEE 802.22 have existed for many years now. However, IEEE 802.22 should not be left out as it could be more attractive to general mobile networks if the use case and services offered are changed. For example, smaller cells such as micro-, pico- or femto-cells. Also mobility could be included. This would not be the most difficult change I guess. In fact, IEEE 802.22 would then be similar to WiMAX and LTE but with cognitive radio functions and opportunistic access. Such use cases and services could provoke more interests among the industry. Consequently, maybe an alliance or forum could be established for IEEE 802.22, or maybe the total IEEE 802.22 or the main cognitive functions could be adapted by the WiMAX Forum!