---------- Forwarded message ----------
From: Amanda Pratt <pratt.amanda.l@gmail.com>
Date: Thu, Feb 21, 2013 at 1:54 AM
Subject: Re: [TIER] TV White Spaces. Was: Re: Economist: On tech and Africa
To: Alexander Chemeris <alexander.chemeris@gmail.com>
Cc: TIER <tier@tier.cs.berkeley.edu>

Hello Everyone,

This is mostly directed at Claro's comment:

"There is plenty of opportunity for innovation. As software radios
have matured, radio designers observe that software is optional, i.e.
one would build a highly configurable radio that could do anything a
software radio could do but based on dynamically configurable hardware
modules, instead. Say a silicon design that implements an RF engine in
the form of an ASIC. There are reasons to believe that such an ASIC
would simplify the path toward both trusted spectrum agile and
cognitive radios."

These IC radios are what I do research on here at Berekeley. DARPA
has put forth money for many organizations to work towards such a
'universal' or 'cognitive' radio. Together with Raytheon and Nokia,
we at the BWRC are looking into the problem. There are a number of
technical difficulties in this space, given the broad number of
protocols and frequencies, but it is a hot area in integrated circuit
design right now and solutions are likely to be commercialized in the
next few years.

Right now, the work is focused mostly on consumer applications (i.e.
making your iPhone work both here and in Europe) and military
applications. But, I personally am involved with the project because
of its applications to the developing world. I would love to speak
with any of you in the space regarding the opportunities and
challenges for getting the last 3 billion on the WWW. Please reach
out with any insights on the the market and demand for mobile,
obstacles to adaption/demand satisfaction, areas for innovations, and
other general implementation issues in both Africa and the rest of the
developing/rural markets.

Thanks!
Amanda

UC Berkeley Graduate Student Researcher
apratt@eecs.berkeley.edu

On Mon, Feb 18, 2013 at 10:58 AM, Alexander Chemeris
<alexander.chemeris@gmail.com> wrote:
> I agree with Steve. Working on OpenBTS I'm looking for time when we'll
> see GSMWS and LTEWS. I.e. when one could install a GSM or an LTE base
> station in any place where there is an available spectrum. At this
> moment explosion of mobile networks is held by this single thing
> called spectrum regulation, which prohibit you to deploy mobile
> services until you pay a lot of money upfront. I hope that TVWS and
> initiatives like the Netherlands' low-power unlicensed GSM will pave
> the way to a wider shift in spectrum regulation.
>
> On Mon, Feb 18, 2013 at 5:42 PM, Steve Song <steve@villagetelco.org> wrote:
>> I think it is worth considering too that TVWS is as much a regulatory
>> innovation as a technological innovation. Secondary spectrum use through
>> the use of a geo-location database and ultimately hopefully through spectrum
>> sensing offers a real opportunity for regulators to by-pass the typically
>> glacial process of spectrum re-allocation and re-farming. One need only
>> look at the digital switch-over process in Africa to see how that is a
>> reality. Not to mention the risk reduction associated with secondary use
>> versus betting a big chunk of licensed spectrum.
>>
>> Cheers... Steve
>>
>> P.S. For interest, I attach a couple of charts on propagation from some
>> BBC-funded research.
>>
>>
>> On 15 February 2013 21:45, Ermanno Pietrosemoli <ermanno@ula.ve> wrote:
>>>
>>> The free space loss is 6 dB less at 450 MHz as compared to 900 MHz.
>>> However, this is if you can clear the first Fresnel zone, which, as Yahel
>>> pointed out, requires more antenna elevation at 450 MHz.
>>> Besides, to obtain the same gain at 450 MHz the antenna should be twice as
>>> big as at 900 MHz. So the real world advantage is kind of iffy with regards
>>> to 900 MHz. But the latter frequency is not unlicensed in most of the world
>>> (outside US and some Latin American Countries), sot the comparison that
>>> matters is with respect to 2.4 GHz.
>>> I agree with Yahel that for long distance point to point links 5 GHz is
>>> more cost effective, but stick to my point for BTS coverage to both mobile
>>> and fixed subscribers.
>>> Regards,
>>> Ermanno
>>>
>>>
>>> On Fri, Feb 15, 2013 at 6:51 PM, Kurtis Heimerl <kheimerl@cs.berkeley.edu>
>>> wrote:
>>>>
>>>> Can you tell me how much better the propagation is for a 450mhz BTS vs a
>>>> 900mhz BTS?
>>>>
>>>> On Friday, February 15, 2013, Ermanno Pietrosemoli wrote:
>>>>>
>>>>> Hi Yahel and group,
>>>>>
>>>>> The lower frequencies have much better propagation characteristic. While
>>>>> it is true that the Fresnel zone size increases with the square root of the
>>>>> wavelength, the diffraction coverage also increases with wavelength, and the
>>>>> absorption losses in walls and foliage are also less, that is why TV bad
>>>>> devices are touted as NLOS. Of course, this might not be the case for very
>>>>> long distance links, but it is very significant for a multipoint coverage of
>>>>> a base statiion.
>>>>> These frequencies have been used in commercial deployments in several
>>>>> countries in what is known as CDMA 450 systems. The improved propagation
>>>>> properties have indeed been proved, although the commercial succes has been
>>>>> limited.
>>>>>
>>>>> Yahel is right that the antennas are considerably bigger, and have lower
>>>>> gain at reasonable sizes, but there is a plethora of offers in this band.
>>>>> Regards
>>>>> Ermanno
>>>>>
>>>>> On Fri, Feb 15, 2013 at 5:32 PM, Shaddi Hasan <shaddi@berkeley.edu>
>>>>> wrote:
>>>>>
>>>>> Great points Yahel. On the subscriber density issue, there's a lot of
>>>>> demand for capacity at lower frequencies, primarily due to their ability to
>>>>> penetrate foliage. I think 900MHz unlicensed equipment has 28MHz of
>>>>> bandwidth available; I hear in practice this is about 10MB of capacity per
>>>>> access point for modern equipment. TVWS would augment this existing
>>>>> equipment very nicely, assuming it ever becomes available at cost-effective
>>>>> prices.
>>>>>
>>>>>
>>>>> On Fri, Feb 15, 2013 at 2:07 PM, Yahel Ben-David <yahel@airjaldi.org>
>>>>> wrote:
>>>>>
>>>>>
>>>>> TVWS might not be the panacea for rural broadband as commonly
>>>>> believed...
>>>>> At least not for fixed-wireless (stationary roof-top antennas to replace
>>>>> non-existent DSL solutions).
>>>>>
>>>>> Where it comes to long-distance links, we're doing just fine with
>>>>> conventional WiFi:
>>>>>
>>>>> 1. We have enough bandwidth even if all links are 40Mhz-wide, since
>>>>> these are highly directional links that do not interfere with each other,
>>>>> and ahh... rural typically means sparse - so bandwidth scarcity is not a
>>>>> problem...
>>>>>
>>>>> 2. We won't enjoy the "better" propagation qualities of the lower
>>>>> frequencies - we already build high capacity links on 5Ghz for as long as we
>>>>> can see... The only limitation is line-of-sight (LoS). In-fact, LoS is not
>>>>> the accurate term here - the limiting factor is a clear Fresnel zone and
>>>>> that's worse the longer the wave-length. To put simply, if to get a 70%
>>>>> clear Fresnel zone for a link on 5.8Ghz between two buildings at 50 miles
>>>>> distance you'll need tower heights of 25m (at both ends), that same link on
>>>>> 700mhz would require tower heights of 72m. To be honest, you get more energy
>>>>> through that 70% clearance on the 700Mhz than on the microwave link, but
>>>>> only about 12% more - so in practice 12% less in the tower height for the
>>>>> same link quality - that's 63 meter tower for the TVWS vs. 25 meter for
>>>>> WiFi.
>>>>>
>>>>> * BTW, the above calculation ignores the curvature of the earth - the
>>>>> real towers needed for such a link are much higher, since the "earth height"
>>>>> in the middle of that link is about 127 meters - far higher than the towers
>>>>> in the example. However, we assume the use of mountains or hills for such
>>>>> links and hence the above example simply show how much taller hill is needed
>>>>> for 700Mhz vs. 5.8Ghz.
>>>>>
>>>>> 3. The antennas are huge - if I'm to build such a link (between two
>>>>> hills or from a high mountain to a far valley) I'll choose high-gain
>>>>> antennas. Say about 30+ dBi or higher. On 5.8Ghz, that's a small low-cost
>>>>> antenna that I could easily mount on balconies' railings by myself. For
>>>>> 700Mhz - ohh well, most balconies won't hold the size and most railings
>>>>> won't hold the weight, not to mention the truck and crane needed to haul and
>>>>> lift the thing... And.. don't forget wind-load and maintenance...etc...
>>>>> True - 700Mhz might not need as high gain as it propagates better, but only
>>>>> about 12% better...
>>>>>
>>>>> 4. Costs and availability - I guess that's obvious... but some may argue
>>>>> this would change with increase in demand... I doubt that - for the above
>>>>> reasons, there won't be any demand for fixed-wireless gear on these bands...
>>>>> Moreover, the whole manufacturing cost structure is against these bands, not
>>>>> to mention operational complexities due to the regulatory domain.
>>>>>
>>>>>
>>>>> So are TVWS good for nothing?!
>>>>>
>>>>> These bands are promising for rural mobile!
>>>>> They may offer the increase in subscribers density per base-station that
>>>>> may drive operators to serve the more rural areas, given them a less risky
>>>>> chance to ROI than with current technologies, not to mention the reduced (or
>>>>> none) license fees.
>>>>> Given the super-low gain antennas that are used in mobile-phones, their
>>>>> physical size increase for use of these bands would not be significant.
>>>>> * Mobile phones must not use higher gain antennas - or else we'll have
>>>>> to hold them straight or point them in the direction of the tower.
>>>>>
>>>>> So yes - TVWS are great, but might not do what many of us think they
>>>>> will...
>>>>>
>>>>> BTW - TVWS are ill-suited for dense urban areas for their strong
>>>>> propagation qualities - in the cities, we strive to contain
>>>>>
>>>>> Ermanno Pietrosemoli
>>>>>
>>>>> Presidente
>>>>> Fundación Escuela Latinoamericana de Redes (EsLaRed)
>>>>> www.EsLaRed.org.ve
>>>
>>>
>>>
>>>
>>> --
>>> Ermanno Pietrosemoli
>>> Presidente
>>> Fundación Escuela Latinoamericana de Redes (EsLaRed)
>>> www.EsLaRed.org.ve
>>>
>>> _______________________________________________
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>>> TIER@tier.cs.berkeley.edu
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>>>
>>
>>
>>
>> --
>> Steve Song
>> +1 902 529 0046
>> +27 83 482 2088 (SMS only)
>> http://villagetelco.org
>>
>> _______________________________________________
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>>
>
>
>
> --
> Regards,
> Alexander Chemeris.
> CEO, Fairwaves LLC / ООО УмРадио
> http://fairwaves.ru
>
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