19 Nov
2017
19 Nov
'17
4:32 p.m.
Hi Mychaela,
On Sat, Nov 11, 2017 at 4:17 AM, Mychaela Falconia
<mychaela.falconia(a)gmail.com> wrote:
But the dirt-cheap Calypso phone situation is now
firmly in the past,
and newly made Calypso devices like my FCDEV3B are nowhere close to
cheap. The qty-1 retail price for one of my FCDEV3B boards is
$500 USD; if someone were to order a large batch (say, 100 boards),
I am reasonably confident that the per-unit price can be brought down
to $300 USD or maybe even lower, but getting any kind of firm numbers
beyond a guesstimate would require actual work, and that work will
only be done if I receive some expression of serious and genuine
interest. But even if we manage to bring the price down to, say, $200
per board with a really large order quantity, it *still* won't be
anywhere near as cheap as old Calypso phones used to be, and the price
is still essentially in the same ballpark as a midrange SDR device.
Thus with the cost of an SDR device and that of a newly made Calypso
device being comparable (or as things stand presently, the Calypso
option is more expensive), is there any remaining reason to use
Calypso devices as opposed to SDR PHY for OsmocomBB? In other words,
is there any solid technical reason (not involving cost) to prefer a
Calypso device over SDR PHY for OsmocomBB purposes, or is there not?
Which translates into: is there any reason to support running OsmocomBB
on FreeCalypso hardware and to market such hw to the OsmocomBB
community, or would it be better to tell people that if they want
OsmocomBB, they should use an SDR PHY, and leave FC hardware for
people like me who are interested in end use applications (as opposed
to hacking) using TI-based FC firmware?
I'm not an active OsmocomBB user or developer, but being involved with
SDR development since 2008 I want to add my 2cc.
I personally think that the SDR way makes much more sense at this
moment. Combine an SDR like our XTRX with any of the widely available
ARM boards and you get a very portable device which can do GSM and
more. If you create a custom board you can even add PA, filters
(bandpass and/or channel), SIM card slot and get a real phone. Such a
carrier board will be very easy to route and cheap to manufacture so
I'm quite sure it'll be at least no more expensive. And given a much
wider functionality, it will be probably much higher volume, again
helping drive the cost down.
Another benefit of the SDR approach is that it will allow you to have
a real FOSS phone - see Harald's comment which I 100% support.
In a "naive" approach receive sensitivity will be degraded compared to
a real phone, but you can put an extra PLL with channel filter to
resolve this at a slight increase in the cost. Most researchers don't
probably need champion sensitivity though, so you can make this an
option. It's easy to route it so that you can populating or not those
components depending on your customer requirements.
Obvious "cons" of the SDR approach is a higher power consumption. In
our XTRX (not sure about other SDRs) we can turn off RFIC or even the
FPGA but I think it will be more power hungry anyway.
Frequency hoping should be doable as well. We haven't done real
measurements yet, but our back-of-the-envelope calculations showed
that we can hop much faster than what you need for GSM. We'll do
measurements once we're done with more basic stuff.
That said, SDR path while more forward-looking and liberating will
require a different skillset than hacking an existing hardware
platform. So at the end, it's your choice which path you find more
compelling.
--
Regards,
Alexander Chemeris.
CTO/Founder, Fairwaves, Inc.
https://fairwaves.co