Blogs
A free workshop on cognitive radio1, organised by Comreg and hosted in CTVR's HQ in Dublin was held on Wednesday July 21. The slides from this event, called Cognitive Radio - an Opportunity for Ireland, can be viewed below2. The workshop also featured several brainstorming sessions focusing on different aspects of how cognitive radio could benefit the consumer and society in general. The agenda and overview of the workshop are available from Comreg's site [PDF download required]
1If you're wondering what cognitive radio is, we'll post a starter guide on this blog soon. This guide was compiled by CTVR and was available to the workshop attendees.
2The following slides will be available on the new CTVR site as soon as it goes live. In the meantime however, this site, reconfigr.com, is being used to host them.
[Update: 06-Aug-2010]
John Holland, CTO Ericsson Ireland, covered topics ranging from the massive growth in demand for mobile connectivity, typical data rate demands for a range of applications from smart metering to HDTV, the need to use white space spectrum to cater for the ever increasing demand for connectivity, potential business cases for cognitive radio, and some outcomes from their recent LTE trials which featured wireless connectivity rates in excess of 1Gbps.
Linda Doyle, Director of CTVR, presented key principles of cognitive radio and dynamic spectrum access, and CTVR's dominant role in this development path.
Jim Connolly, Senior Spectrum Adviser for Comreg presented insights from an Irish spectrum regulator point of view and what opportunities are available for parties interested in conducting wireless tests and trials in Ireland.
Johnny Evans, Head of Frequency Planning in RTÉ Transmission Network Limited presented a brief overview of what cognitive radio means to a national broadcaster as a 'new neighbour' in the UHF bands
Andrew Stirling (Head of Spectrum Policy for Microsoft in the UK and Europe) discussed how 'nimble spectrum regulation' and sub 1-GHz spectrum usage are key elements of the solution to support the ever-increasing demand for wireless connectivity.
Following on from this, Andrew presented his insights in terms of the larger European context. This presentation also covers recent and ongoing trials in the U.S and Scotland.
Davide Cherubini from Alcatel-Lucent, Bell Labs Ireland (BLI) talked about their work on increasing energy efficiency in cellular networks through 'green radio' solutions.
Kerry Hartnett from Intel Labs presented an overview of a FP7 project called N4C, which mainly focuses on delay/disruption tolerant networking. He talked about the potential for cognitive radio-related technologies in this work.
Everyone is familiar with broadcast FM radio, right? As a ubiquitous source of entertainment, news, discussion, or just background sound, it is perhaps something we take for granted these days.
Turning music and voice into wireless signals
The radio stations are all corralled into a section of frequency spectrum extending from 87.5MHz to 108MHz in Ireland. Each licenced radio station is allocated a small part of this spectrum, just 200kHz wide.
Frequency modulation (FM)
FM works by using the amplitude of an information signal to vary the frequency of the carrier signal. The carrier signal is what you tune to e.g. 104.4MHz (FM104), 105.2MHz (Phantom FM). The carrier frequency can swing by ±75kHz either side of this centre frequency. A very quiet or silent audio signal results in little or no deviation while a loud audio signal causes the frequency to swing by the maximum ±75kHz allowed.
Receivers reverse this process to recover the information. This information signal comprises the mono and stereo audio. Extra services can also be included in this. Radio Data System (RDS), a low rate data service that can provide traffic alerts, station and song identification, and alternative tuning frequencies is a widely used example of this.
Some examples and colourful plots
To help visualise how radio stations use their allocated chunk of spectrum, we can take a look at how the signal power is distributed using power spectrum plots. In the following, the power of the FM signal is represented by the variation in colour from dark blue (low power) to dark red (high power) over 15-30 minute observation periods.
Music has a lot of rapidly changing audio components and causes the frequency of the carrier signal to swing wildly between ±75kHz about the centre frequency. A single voice results in a slower rate of change. The silences between words mean that no modulation takes place and therefore no swing in the carrier frequency.
The width of the red/orange bands in these plots indicates the deviation and therefore the complexity of the audio content e.g. music and jingles. The narrow red segments in the centre indicate the voice and silence portions of the FM signal e.g. DJ talk and the news.
The above plot is for 2FM during a morning talk show. The programme content was a mixture of voice and music. The songs and jingles are the wider bands of red and orange and the concentrated red bands right in the middle indicate periods where the DJ or other presenter was speaking.
Raidió na Gaeltachta - voice & music: In this case, the programme consisted of more spoken word content than music. During the midpoint of the plot timeline, it looks like the DJ played some music with a lot of complex components e.g. traditional Irish music perhaps.
FM 104: This is a mainly music-based station hence the almost constant use of the entire range of deviation. In a bid to sound as 'loud' as possible, radio stations compress the audio signal so that the normally quieter parts of songs and voice sound as powerful as the normally loud parts. In some cases, this can be pushed to the extreme where the dynamics of the music are heavily restricted.
98FM - music: As a predominately music-oriented station during the period of capture, the spectrum usage is quite similar to FM104. However, take a look at the concentration of power about the centre frequency. This was the news at 11am.
RTE Radio 1 - voice & music: The strong concentration of power close to the centre frequency indicates this was a period of time where the programme content consisted of mostly spoken word.
Phantom FM - music and voice. On 105.2MHz, Phantom FM's programme content comprised music and voice during the observation period. However, based on this plot, they don't appear to push the compression to the limit meaning that the music retains more dynamics than for the other examples above.
Sticking with Phantom, we had a look at spectrum usage over a two hour period. The plot below is an entire afternoon show called 'Phantom Daily' by Phantom FM DJ Simon Maher.
What are those extra signals at the band edge?
If you've read this far, perhaps you may be wondering what those extra signals near the edges of the band for some of the above plots are. We were wondering also so decided to ask RTE. Apparently they are trialling a new low-rate data service that will enable some satellite navigation systems in cars to get traffic alert information that will enable them to update their routes to avoid problem areas. This will eventually be incorporated into the RDS system and will cover the same area as the radio station. For the moment though, it's being tested using a dedicated frequency out of harms way on some radio stations.
We're speaking at the Irish Workshop on Opportunities for ‘Long Term Evolution Advanced’ (LTE+) Cellular Systems in Dublin today [May 27, 2010]. The talk will introduce reconfigr.com and briefly touch on some of the work that we're doing that applies to LTE+. Some nice features of LTE+ include up to 100Mbps connectivity in high-mobility scenarios, up to 1Gbps in low-mobility scenarios and low latency.
Though LTE is still to be deployed there is already talk of LTE+. LTE+ has the potential to truly deliver mobile high speed wireless access and radically change business organisation and service delivery. The purpose of the workshop is to ask whether Ireland should strive to get ahead of the LTE+ curve and if so how can we best do this?
Update [28/05/10]: Read a report about this workshop in irishdev.com
