Usrp x310 LTE support, with/without external clock

GNU Radio
1

I’m new to gnuradio and sdr. I’m looking to use a x310 usrp in an lte
project.
I have read it can support a 184.32MHz clock frequency
which is great for LTE and a sample
rate of 30.72MHz.
I have looked at the uhd source code.
I get the impression that the lte frequencies can only be supported
if you use an external clock,
I guess this means, external reference clock or Gspdo…
I haven’t found anything in my googling, which clarifies the situation.

I liked to start withe the basic x310 and a daughter board
, for example the sbx and add a gspdo
etc… at a later date.

2

Hi Paul,

in (maint branch) host/lib/usrp/x300/x300_clock_ctrl.cpp,
set_master_clock_rate(double):
if(doubles_are_equal(_system_ref_rate, 10e6)) {
if(doubles_are_equal(clock_rate, 184.32e6)) {
/* 10MHz reference, 184.32 MHz master clock out, NOT Zero
Delay. */
clocking_mode = m10M_184_32M_NOZDEL;
}
[…]

Since the m10M_184_32M_NOZDEL-case further down seems implemented, I’d
expect that to work.

Greetings,
Marcus

3

Hi Paul,

On Fri, Oct 10, 2014 at 7:19 AM, Paul C. [email protected]
wrote:

I’m new to gnuradio and sdr. I’m looking to use a x310 usrp in an lte project.
I have read it can support a 184.32MHz clock frequency
which is great for LTE and a sample
rate of 30.72MHz.
I have looked at the uhd source code.
I get the impression that the lte frequencies can only be supported
if you use an external clock,
I guess this means, external reference clock or Gspdo…

184.32 MHz is supported without external referencing. A wide range of
X310 users are running at that rate both with and without using
supplemental reference sources.

-TT

4

On 10/10/2014 06:34 PM, Tom T. wrote:

184.32 MHz is supported without external referencing. A wide range of
X310 users are running at that rate both with and without using
supplemental reference sources.

You can init your device with master_clock_rate=184.32e6 to get your
desired rate.

M

5

Thank you for the replies. I succeeded in using a clock rate of
184.32Mhz and
a sample rate of 30.72MHz.

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