Hello OsmocomBB community,
I am the manufacturer of a GSM mobile station development board based on the Calypso+Iota+Rita chipset from TI. The hardware product in question has been created for the primary purpose of running the end-use-oriented GSM+CSD+GPRS modem firmware that was previously maintained by TI and whose maintenance has since been taken over and continued by FreeCalypso, but being based on the Calypso chipset, my board is also capable of running OsmocomBB. The purpose of the present inquiry is to find out whether this hardware product might be of interest to the OsmocomBB community, or if those who wish to run OsmocomBB (as opposed to TI-based FreeCalypso firmware) would be better advised to use an SDR device instead.
As I understand it, there are two reasons for why the original incarnation of OsmocomBB (prior to the recent addition of SDR PHY support) used Calypso phones as its physical transceiver instead of USRP-style SDR devices: (1) the work done by the Calypso DSP is already done, hence there was less work for OsmocomBB developers to do, and (2) Calypso phones used to be dirt-cheap, whereas SDR devices cost some non-trivial money.
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?
One argument I have heard against the use of SDR for GSM MS role is that SDR devices supposedly have a difficult time retuning every 4.615 ms, and thus would have a difficult time connecting in the MS role to a GSM network that employs frequency hopping. Is there any truth to that argument, or has that problem already been solved? Are there any other areas in which a chipset like the Calypso that is specifically designed for the GSM MS role would perform better than an SDR device of the kind that are viable cost competitors against newly made Calypso hardware?
Just seeking some clarification...
M~
P.S. Before anyone says that Calypso chips themselves are no longer made and thus don't constitute a viable option, please note that I can still buy them on the Chinese grey market at least in tens of thousands of pieces, maybe more, and there is no conceivable way that all current phone hacking and phone liberation communities combined can produce enough demand to exhaust that supply. And if someone does order 100 thousand Calypso boards at $300 or so apiece, that would be more than enough money to hire a pirate chip fab to clone every chip in the Calypso chipset.
Hi Mychaela,
On Fri, Nov 10, 2017 at 05:17:21PM -0800, Mychaela Falconia wrote:
As I understand it, there are two reasons for why the original incarnation of OsmocomBB (prior to the recent addition of SDR PHY support) used Calypso phones as its physical transceiver instead of USRP-style SDR devices: (1) the work done by the Calypso DSP is already done, hence there was less work for OsmocomBB developers to do, and (2) Calypso phones used to be dirt-cheap, whereas SDR devices cost some non-trivial money.
Actually, it's also (3) the (particularly) receiver performance of the TIS DSP is pretty damn good and it is quite some effort to achieve comparable performance with a general-purpose SDR. You can e.g. add external band filters for downlink, but then you're still missing the analog matches 270kHz baseband filter in front of the ADC to avoid loosing any ADC resolution to nearby in-band carriers. The analog filters in integrated RFICs today typically don't go smaller than 1MHz (if at all) which is quite far from the 270kHz that GSM uses. (4) you can actually run the entire application (e.g. http://osmocom.org/projects/baseband/wiki/Rssibin) inside a small, hand-held, battery-powered device. Try that with PC + SDR and look at your size + power budget. (5) somewhat ties into (4): One goal was always to run also 'mobile' inside a phone and have a FOSS-based telephone. Nobody has had the time + endurance to get there, and I doubt it will still happen at this point.
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.
It is also something to keep in mind that a lot of the people who had an interest in OsmocomBB have those phones for years. And the number of new people who haven't been around for many years with an interest in playing with "old" cellular systems such as GSM is quite low.
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,
Having done a fair amount of electronics manufacturing in this kind of quantity, I would seriously be surprised if you'd still be at that kind of pricing in a MOQ-100 situation. But sure, it will not be at the level of a used old phone.
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?
See above.
Hi Mychaela,
On Sat, Nov 11, 2017 at 4:17 AM, Mychaela Falconia mychaela.falconia@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.
baseband-devel@lists.osmocom.org
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Alexander Chemeris -
Harald Welte -
Mychaela Falconia