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| From: | Mostafa Alizadeh |
| Subject: | Re: [Discuss-gnuradio] Bluetooth Transmitter using GRC |
| Date: | Thu, 15 Jan 2015 10:20:04 +0330 |
On 01/14/2015 02:29 PM, Mostafa Alizadeh wrote:The X3xx series uses a 2.5PPM TCXO, just like the N2xx series. If that isn't accurate enough, you can always use an external, higher-accuacy
Hi
However, there is another point needed to be noticed and that's the LO (local oscillator) capability of the daughterboard. I mean, does have the X-series enough ppm (lower than 3 ppm)? The LO also shall have suitable switching time too.
reference.
You use the same daughtercards in the X3xx as the N2xx, except that with the -120 cards (designed specifically for X3xx), they have a wider
analog baseband, to "match" the ADC sample rate. So, the LO switching times would be the same--on the order of a few milliseconds.
LO architectures for wideband frequency hopping need to be explicitly engineered for that particular application, and it looks like BlueTooth
hop-rates are sub-millisecond, so you can't hop the LO fast enough, but as Marcus Mueller points out, you can hop within a wide baseband.
Best,Mostafa
On Tue, Jan 13, 2015 at 5:46 PM, Marcus Müller <address@hidden> wrote:
The architecture itself can basically deal at arbitrary sample boundaries; however, as soon as you tune a physical thing like an LO, you need some time, especially since the LOs generated on USRP daughterboards discipline the LOs to the high-quality reference clock using PLLs. Depending on the frequency, the frequency delta, the daughterboard, environmental situations as well as individual component variances, the time from tune to stable oscillator changes; these times are in the order of multiple milliseconds, in most cases.
You could avoid analog tuning by only doing frequency shifting in the DSP on the N210's FPGA; however, the N210-compatible daughterboards have a bandwidth of 40MHz, so this is not possible for Bluetooth (which is spread over 80MHz).
With the X3x0, you can use 120MHz daughterboards, which would enable you to do purely digital tuning.
I am, however, not familiar enough with the Bluetooth PHY to assess whether there are latency constraints that prohibit control by a PC -- if the hop sequence is known sufficiently before transmission starts, one could try to generate timed commands that tune the DSP on specific samples. However, that might get a bit ugly, because the on-device command queue has a limited length, so you might need to send timed commands at high rates.
Alternatively, the 80 MHz bandwidth comfortably fits into the sampling rate you can get in and out of the X3x0 via 10GigEthernet -- but then, your PC will be burdened with the task of continously generating more than 80MS/s -- for 2 MHz of instantaneous bandwidth.
Best regards,
Marcus
On 01/13/2015 02:44 PM, Mostafa Alizadeh wrote:
Yeah I have had a look at Bluetooth PHY. The hop rate of Bluetooth in paging substate increases as 3200 hop/sec too. So you mean the N210 USRP can't support 1600 (or 3200) hop/sec? What do you mean by "latency"? Is that the latency of the USB or Ethernet? Jeff, please clarify your stance. Why the latency problem doesn't matter X-series USRP? Best, Mostafa On Tue, Jan 13, 2015 at 3:02 PM, Jeff Long <address@hidden> wrote:On 01/12/2015 01:07 PM, Mostafa Alizadeh wrote:Hi Jeff, What is your reason for saying: "Latency and tuning" of the N210 device isn't appropriate???I should have said that, with either USB or Ethernet, and with a non-real-time O/S, the latency to too great. Hop rate is generally 1600 hops/sec. Take a look at the Bluetooth physical layer spec for more info.Best, Mostafa On Mon, Jan 12, 2015 at 2:52 PM, Jeff Long <address@hidden <mailto:address@hidden>> wrote: On 01/10/2015 02:46 PM, vaibhav kulkarni wrote: Hi All, I am searching for an implementation of a complete Bluetooth stack on GRC 3.7 ( Including the Bluetooth Transmitter and Receiver) preferably working with USRP N210. So far I got this "gr-Bluetooth, Bluetooth for You could build one in the FPGA of an X-series box. Latency and tuning requirements exceed what you can do with a N210. GNU Radio" (http://gr-bluetooth.__sourceforge.net/ <http://gr-bluetooth.sourceforge.net/>), However it is not a complete stack and I guess it doesent include the Bluetooth Transmitter. I built it and checked but couldn't find one. Can you suggest any existing implementation of complete Bluetooth stack ? Any Help is appreciated. Regards, Vaibhav _________________________________________________ Discuss-gnuradio mailing list address@hidden <mailto:address@hidden> https://lists.gnu.org/mailman/__listinfo/discuss-gnuradio <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> _________________________________________________ Discuss-gnuradio mailing list address@hidden <mailto:address@hidden> https://lists.gnu.org/mailman/__listinfo/discuss-gnuradio <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> -- *********************************************************** Department of Electrical Engineering Aboureyhan Building MMWCL LAB Amirkabir University Of Technology Tehran IRAN Tel: +98 (919) 158-7730 LAB: http://ele.aut.ac.ir/~mmwcl/?page_id=411 Homepage: http://ele.aut.ac.ir/~alizadeh/ ***********************************************************_______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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