Â It is for UMTS based standard LTE (20MHz bandwidth) which has 30.72Msps
and this is beyond USRP2’s instantaneous bandwidth (25MHz). I am
simulating LTE (10MHz bandwidth) where I can halve the sampling rate of
15.36Msps. Reading the earlier mail threads and responses from Matt I
understand that it is better to handle the sample rate converters at the
software level rather than doing at the FPGA level in the USRP2 code.
LTE is based on OFDM and is not using any spectral shaping filter,
instead the samples generated for OFDM symbols at the above rate are
directly read/write into DAC/ADC. I could successfully do the aboveÂ by
performing downlink and uplink using interpolation factor 16 which boils
down to 6.25Msps but when I used the interpolation factor 6 (or 8) it
gives the overflowing errors. I am using Quadcore PC (2.6GHz), can you
suggest any other high end PC that can handle the above processing?
Krishna S Â Â Â
— On Fri, 9/4/10, John O.
[email protected] wrote:
From: John O. [email protected]
Subject: Re: [Discuss-gnuradio] sampling rate of tx_sampless.cc and
To: “Johnathan C.” [email protected]
Cc: “Krishna S” [email protected], “gnu”
Date: Friday, 9 April, 2010, 4:15 PM
Just a guess, but that sounds like 4x the UMTS chip rate (which is
3.84 Mchips/sec).Â If this is the case, there is an RRC filter at the
last DSP stage typically, so your suggestion for folding this
re-sampling in is spot-on.
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