good clocks (not using GPS) and multi-channel hw [was: sidebands of great justice]
On Thu, Nov 7, 2013 at 11:32 PM, coderman <coderman@gmail.com> wrote:
... SDR MIMO kit leaves much to be desired, however.
let me clarify: the hardware available for SDR MIMO development leaves much to be desired. ... the blocks and implementations for OFDM coding in software are OK :) USRP N2X0 can do it, other setups require external reference clock with high fidelity. any recommendations for non-GPS clocks performing at 50-100ppb or better?
________________________________ From: coderman <coderman@gmail.com> To: David I. Emery <die@dieconsulting.com>; cpunks <cypherpunks@cpunks.org> Sent: Subject: good clocks (not using GPS) and multi-channel hw [was: sidebands of great justice]
the hardware available for SDR MIMO development leaves much to be desired. ... the blocks and implementations for OFDM coding in software are OK :)
USRP N2X0 can do it, other setups require external reference clock with high fidelity. any recommendations for non-GPS clocks performing at 50-100ppb or better?
Other than a good ovenized crystal oscillator (OCXO), there is something called a "DCXO" (Digitally-Compensated Crystal Oscillator) that is probably as good as 50 ppb over a moderate temperature range. See, for example, : http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1546247&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4%2F33000%2F01546247.pdf%3Farnumber%3D1546247 http://electronicdesign.com/components/dcxo-combines-stability-low-power Jim Bell
On Thu, Nov 07, 2013 at 11:57:25PM -0800, coderman wrote:
On Thu, Nov 7, 2013 at 11:32 PM, coderman <coderman@gmail.com> wrote:
... SDR MIMO kit leaves much to be desired, however.
let me clarify:
the hardware available for SDR MIMO development leaves much to be desired. ... the blocks and implementations for OFDM coding in software are OK :)
USRP N2X0 can do it, other setups require external reference clock with high fidelity. any recommendations for non-GPS clocks performing at 50-100ppb or better?
You don't need a global clock like GPS for MIMO, just a local high quality clock pulse to build a time base across multiple transceivers. ... unless I'm missing something? Nuand already has 2x2 MIMO by slaving one board to another's clock, and is developing a 4x4 MIMO clock distribution board. -andy
On Fri, Nov 8, 2013 at 11:50 AM, Andy Isaacson <adi@hexapodia.org> wrote:
... You don't need a global clock like GPS for MIMO, just a local high quality clock pulse to build a time base across multiple transceivers.
correct. a common answer to inexpensive high quality clock is to pass the buck to GPS; this is explicitly not suitable, hence the qualifier... thanks for the heads up on Nuand. best regards,
On Fri, Nov 8, 2013 at 12:04 PM, coderman <coderman@gmail.com> wrote:
... correct. a common answer to inexpensive high quality clock is to pass the buck to GPS; this is explicitly not suitable, hence the qualifier.
GPS disciplining to keep a OCXO in check periodically (GPSDO) would be useful! GPS just can't be the primary source. has anyone used an OctoClock-G? https://www.ettus.com/product/details/OctoClock-G best regards,
participants (3)
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Andy Isaacson -
coderman -
Jim Bell