The benefits of a managed spectrum
We were now at the halfway point of our stay 2 week in Niue, most of our equipment had arrived, so it was time to set up OpenBTS and create the trial 900Mhz GSM service for the people of the island of Niue.
We had tested OpenBTS and everything was working, so the next step was to mount the antenna on the local TV transmitter tower.
Then we switched it all on……
Things started to go down hill at that point….
We realised that the Xorcom gateway which was to be used to connect OpenBTS to the island phone system was still stuck in customs in Auckland meaning that the system would have to be used in stand-alone mode for the time being.
We did some coverage and quality tests. We then found that the 900Mhz spectrum was pretty crowded – the old AMPS analog mobile system was present, which we knew about and had been warned to avoid by Niue Telecom. OpenBTS’s radio had been tuned to include a filter to ignore these frequencies.
We also found that there was widespread use of 900Mhz Wifi equipment – including on the TV tower we had our antenna on. This was a surprise, especially since 900Mhz is designated by the ITU as spectrum for licensed mobile communications in all parts of the world except North America. After some emails and asking around we found that the Wifi was run by the Internet Users Society of Niue who were using imported equipment that can be operated without a license in the USA.
It is worth noting that IUSN have had a complex relationship with the Government of Niue – see this article to get a flavour.
Anyhow, Harvind retuned the filter to try and block the wifi, which was threatening to overwhelm the signals from handsets. David adjusted the power management to encourage the handsets to put out more power (at the risk of poorer battery life) and we went out to test it.
We provisioned (by hand) some 30 test phones and started to use the system. Unfortunately an error on my part resulted in a Fijian visitor getting service, much to her and our surprise.
The system worked well, text messaging proving popular even in the small test group. Coverage however was more limited than we had hoped. We concluded that there were 3 reasons for this:
- The vegetation in Niue is very lush – which we should have expected since part of the island is a rain forest. This dense greenery absorbs the GSM signal
- The interference from the wifi was reducing our ability to detect weaker return signals from handsets (despite the filter)
- The antenna mounting wasn’t optimal
We had a progress meeting with our client, the Govt of Niue and Niue Telecom. This resulted in a flurry of action. The islands fishery repair shop was drafted in to fabricate an improved antenna mount, which allowed us to correct the angle of the antenna, improving the coverage in the commercial center of Alofi.
Niue Telecom loaned us the use of a spare satellite link, which let us test international calling.
These changes improved the system to the point that it was very useful. Indeed on the final day I called into the VoIP Users Conference from my iPhone using the system.
Probably the best demonstration of the system occurred later that morning while I was doing some last minute shopping for souvenirs and my phone rang, (you should have seen the looks on the faces of the other folks in the shop!) it was our client, telling me that a TV crew had arrived at our rented house and could I get back quickly to be interviewed!
Overall the test was a qualified success, the main lessons learnt were :
- Bring everything as personal luggage, ship nothing
- Don’t assume a spectrum will be clear just because you have a license for it
- OpenBTS works!