DIY BTS

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Barnaby Astles bjastles at gmail.com
Tue Nov 30 12:46:09 UTC 2010


Just a side note the octasic also would permit WCDMA/HSPA+ witch would be a
good idea as it would permit us to explore the other half of the cell world.

Barnaby J Astles
Solutions Saminov inc

166 rue Cowie
Suite 201
Granby, QC, Canada
J2G 3V3

Cell: (450) 522-7153
Fax: (450) 372-8430


On Mon, Nov 29, 2010 at 12:25, David A. Burgess <dburgess at jcis.net> wrote:

> We have tried a half-duplex BTS with OpenBTS, only transmitting on 3 slots
> to avoid a duplexer, and it did not work very well.  Most handsets would not
> camp to it, even when it was the only signal available.  So you need to deal
> with the frequency duplexing problem and the antenna switch that you find in
> a typical MS will not work.  There are also some small-but-important
> important changes in L1 and L2 that might not be possible in a highly
> integrated, optimized product.
>
>
> On Nov 29, 2010, at 12:29 AM, Hans Witvliet wrote:
>
>  On Sun, 2010-11-28 at 23:49 +0100, Sylvain Munaut wrote:
>>
>>> Hi,
>>>
>>>  My first reaction was one of sceptism, but according to the people of
>>>> huwei it is do-able, no hardware changes needed, just some (major)
>>>> software rewrite.
>>>>
>>>
>>> With a single dongle ? Sounds weird.
>>>
>>> The "client"/MS side of GSM have no duplexer but a TX/RX switch and a
>>> BTS needs to be able to TX and RX at the same time.
>>> (to be easily detectable by phones. It could 'possibly' work without
>>> it and phone would stay camped onces they are there but it could take
>>> several try for them to 'see' the network).
>>>
>>>
>> Indeed, i am still skeptic: seeing is believing.
>> Got my HF-licence since 1978, so i know that it is very hard to do tx
>> and rx on nearby frequencies. One needs extreme good (cavity) filters.
>> Without those, even separate transmitters and receivers will not be
>> sufficient, as your receiver input stage will be completely saturated.
>>
>> Eventhough "normal" bts must be capable of handling multiple handhelds,
>> while these dongles needs only to communicate with just a single one, at
>> extreme low power, there is not enough space inside for decent filters.
>>
>> Hans (PE1CXJ)
>>
>>
>>
>
> David A. Burgess
> Kestrel Signal Processing, Inc.
>
>
>
>
>
>
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