Weather balloons no longer a crazy idea for rural coverage
As the US gets serious about opening up mobile broadband to its entire population, it is hunting for new spectrum options to support that.
The UHF digital TV switchover spectrum sell-off brought in around $20bn, and one of the key uses of this 700MHz band will be to support long range radio signals to cover rural America more cheaply with mobile and broadband services.
This month we saw the claim by mobile satellite operator SkyTerra that this previously niche market could help expand broadband availability affordably, harnessing the 100MHz of spectrum that is available for hybrid terrestrial/satellite mobile communications. Now an even more niche option may be getting its place in the sun – the use of 'balloons‘ to act as base stations in the sky.
The use of hot air or helium balloons, or 'stratellites' (which live far closer to earth than satellites), for communications started out 20 years ago as a fairly laughable idea, but has refused to go away, and it now approaching commercially viable reality.
If it can be perfected it could deeply unsettle existing telecoms. What would happen to the value of current gold dust spectrum if it turns out that already available bands can be used to cheaply deliver rural services?
The near term potential is highlighted by new trial results from the main player in this field, Space Data, which last week put a mobile network in the sky on the back of a conventional weather balloon.
Currently, Space Data provides the southern US with something it calls SkySite, using its own narrow slice of 900MHz spectrum to offer private communications to the oil and gas, transportation and utilities industries in the region. It covers Texas, Oklahoma, Louisiana, New Mexico, Arkansas and the Gulf of Mexico but is ― always looking for opportunities to expand nationwide‖ via new spectrum partnerships.
As the major mobile players start to form alliances with mobile satellite operators to expand their rural reach and target new markets such as public safety, Space Data will hope to tap into the same trend. What it has done now is put a digital CDMA network into the sky using a miniaturized base station weighing a few pounds, carried by a balloon, to reach a 20,000 square mile coverage area from 60,000 feet.
The experiment was using 1.9GHz PCS spectrum with backhaul in the 2.4GHz band. After completion of each flight, the base station was released, parachuted to the ground and recovered intact for future reuse. SkySite high altitude, balloon borne transceivers need to be launched every 8-12 hours.
But why stop there - why not launch a number of balloons concurrently for redundancy? Because of the distance over which direct line-of-sight signals will travel, in an area with a well understood prevailing wind, a balloon can be released, fly over a huge area of a country, reaching a massive footprint.
And then (based on location information sent down to a local network operations center), it can release itself from the balloon, deploy a parachute, and be collected and reused the following day. A balloon can go up as often as required and a fraction of the number of base stations would be required, compared to the number of full scale stations for a terrestrial deployment.
Speaking to RCR Wireless News last year, Space Data claimed it could save a new national wireless player $2bn, or construction of 8,500 new towers across the country, in order to create a national public safety network in the 700MHz D Block. This spectrum is supposedly earmarked for a national safety system, but is still mired in political debate after failing to reach its reserve price at auction.
That report said cell sites cost about $250,000. Space Data pays $50 to launch a balloon and $100 to retrieve electronics (valued at $1,500) for reuse. One balloon 100,000 feet high covers a 420-mile diameter circle, so it would take 41 SkySites for national machine-to-machine wireless connectivity, or over 200 SkySites for nationwide wireless voice coverage across the US.
Space Data is the largest holder of nationwide narrowband PCS spectrum, and last year got 21 new iDEN-capable channels, making it likely the CDMA spectrum partner in its current trials is Sprint Nextel. Space Data also holds AWS licenses in the Gulf of Mexico and Alaska.
During two trial flights, a prototype miniaturized CDMA 1X-RTT base station was carried over a remote area in western Utah by the SkySite balloon platform to altitudes as high as 60,000 feet.
At that point, the base station was used to carry calls from, to, and between ordinary CDMA handsets located on the ground 60 miles away. Call quality was excellent, claims Space Data, with low frame error rates on both the forward and reverse channels.
The company says the trial confirmed the technical feasibility of serving ordinary wireless handsets from substantial distances using the SkySite system.
Applications include serving remote areas of low population densities, fill-in for gaps in rural networks, and the provision of emergency communications while terrestrial systems are out of service – another of the vital revenues streams for mobile satellite carriers in the US.
Other powerful allies might be found in the internet community, always looking for ways to extend low cost access and so stimulate uptake of services. In 2008, Google was said to have invested in Space Data and speculation of a further investment in the firm, or a cooperation on extending its network, resurface periodically.
And the shared spectrum/shared revenue model it is exploring with its CDMA partner (and which AT&T, in particular, is adopting with MSS allies) is not confined to the rural US, but will become increasingly important as countries round the world look to expand broadband coverage without loading all the cost and risk onto the cellcos.
The model of a satellite or stratellite firm operating and owning the network in a partner‘s spectrum, with revenues shared, is becoming increasingly common in emerging markets with large rural areas, such as Russia, where it has been adopted by some WiMAX providers.
Copyright © 2009, Wireless Watch
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