[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Discuss-gnuradio] M&M impl, its parameters, and why does it work for GM

From: George Nychis
Subject: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK?
Date: Fri, 11 Apr 2008 12:18:05 -0400
User-agent: Thunderbird (X11/20080227)

Hi all,

I've attempted to follow the M&M optimization algorithm paper, which GNU Radio implements, to try and select proper parameters for a O-QPSK / MSK implementation floating around that a UCLA group wrote:

I ask because it seems as though the PHY is not recovering from clock drift properly, which would be the goal of the M&M block. The blue in this graph is not important, but note the smearing on the right:

That smearing is not recovered from properly by M&M and causes loss, as an example. This causes approximately anywhere from 5-15% frame loss over _coax_.

So I was pointed to the M&M paper, to try and understand why its recovery is not working properly, looking to set proper parameters. The paper is here:

But, if you read the first paragraph, it states that this algorithm is NOT for MSK, or GMSK for that matter:
          "We are assuming a system whose output comprises nom-
inally synchronised data symbols subject to additive white Gaus-
sian noise, where the transmitter and the receiver use Nyquist root
raised-cosine filters."

So, before I go any further... I was hoping someone could shed light on how this ends up working out for GMSK which does not use an RRC filter.

Then, why would it not work with the MSK implementation? ;) I understand that GMSK is band-limited by the Gaussian filter, is this the significant difference?

I suppose the overall question is the implications of using a CPM signal when the GR clock recovery block was written using an RRC filter.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]