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#1 2016-May-17 18:20:06

ralph1999
Member
Registered: 2015-Feb-21
Posts: 21

Phase Noise in SISO single carrier code

Dear WARP Team,

Since there is no SISO Single Carrier example code avaiable on WARP v3. We are trying to modify the SISO example communication code (warplab_siso_example_Comm.m) in the previous WARPLab code, avaiable in the SVN folder \ResearchApps\PHY\WARPLAB\WARPLab_v05_2\M_Code_Examples. After mapping the WARPLab v7 code into this script, we create two ways to test the new code, simulation and using WARP v3 boards. Here are the constellation results.

http://s32.postimg.org/qsaogu551/QPSK_WARPv3_Simulation.png
http://s32.postimg.org/4c5qlcdc5/QPSK_WARPv3_Phase_Noise.png
http://s32.postimg.org/4mvmnnlhh/QPSK_WARPv3_Phase_Noise_Marked.png

It seems that when WARP boards are used, there are serious phase noise and errors, and the phase error correction and/or channel equalization will be needed. Any comments and advices are very welcome regarding this issue.

Thanks.

Last edited by ralph1999 (2016-May-17 18:22:51)

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#2 2016-May-18 09:12:50

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: Phase Noise in SISO single carrier code

The WARPLab 5 Comm Example does not implement any frequency or phase synchronization. Instead it uses differential encoding between symbols. Differential encoding assumes the symbol rate (5Msym/sec in that example) is much larger than the frequency offset (<5kHz at 2.4GHz is typical for WARP hardware). Differential encoding uses the phase difference between consecutive symbols to encode data bits. With this scheme the absolute phase of the received symbols are irrelevant, it's only the symbol-to-symbol phase difference that matters. If the nodes have a non-zero CFO the received constellation will definitely show symbols spread across many phases, even a full circle for a long transmission or large CFO.

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#3 2016-May-18 09:20:24

ralph1999
Member
Registered: 2015-Feb-21
Posts: 21

Re: Phase Noise in SISO single carrier code

Hi murphpo,

Can we have any advices on coding the SISO single carrier communication? Is this way (modifing the SISO Comm Example in WARPLab 5) a good way to do? Or any other example codes right now on the website are good to start from?

If this current way is fine, you mean a non-zero CFO coding is a possible solution to this issue, am I right?

murphpo wrote:

The WARPLab 5 Comm Example does not implement any frequency or phase synchronization. Instead it uses differential encoding between symbols. Differential encoding assumes the symbol rate (5Msym/sec in that example) is much larger than the frequency offset (<5kHz at 2.4GHz is typical for WARP hardware). Differential encoding uses the phase difference between consecutive symbols to encode data bits. With this scheme the absolute phase of the received symbols are irrelevant, it's only the symbol-to-symbol phase difference that matters. If the nodes have a non-zero CFO the received constellation will definitely show symbols spread across many phases, even a full circle with many symbols or a large enough CFO.

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#4 2016-May-18 09:28:06

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: Phase Noise in SISO single carrier code

We don't have much experience building single-carrier comm systems; our focus as been on OFDM PHYs for a long time. I would suggest looking at the examples in the MATLAB Comm Toolbox and in Mathworks File Central. WARPLab can be used with any PHY Tx/Rx scheme that operates on I/Q values sampled at 40MSps.

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#5 2016-May-18 09:29:29

ralph1999
Member
Registered: 2015-Feb-21
Posts: 21

Re: Phase Noise in SISO single carrier code

Sure, thanks. We will look at it.

murphpo wrote:

We don't have much experience building single-carrier comm systems; our focus as been on OFDM PHYs for a long time. I would suggest looking at the examples in the MATLAB Comm Toolbox and in Mathworks File Central. WARPLab can be used with any PHY Tx/Rx scheme that operates on I/Q values sampled at 40MSps.

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