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Re: [Discuss-gnuradio] Ettus Research Announcements -- Nov 2010

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] Ettus Research Announcements -- Nov 2010
Date: Tue, 16 Nov 2010 17:45:55 -0800
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On 11/16/2010 05:20 PM, Steve Mcmahon wrote:
Hello Matt:

Sorry, one more question. Will the USRP N210 still support the raw
Ethernet interface to the host (like for the USRP2), or will it only
support the new UHD interface?

We have no intention of supporting the raw ethernet interface on there. If someone wanted to port it over from the USRP2 it is certainly possible, but not worthwhile.

Secondly, what is performance penalty of UHD interface versus the raw
Ethernet interface? UHD is based on UDP, so certainly there must be
some reduction in the maximum data rate (and thus the bandwidth)
compared the raw Ethernet interface. UDP certainly adds overhead...

UDP/IP only add a very small amount of overhead since we are using 1500 byte packets. Our max sample rate is 25 MS/s at 16 bits I, 16 bits Q. That gives us 800mbps, which is enough under the 1 Gbps capability that there is plenty of room for the overhead.

Finally, if the USRP N210 only supports the new UHD interface, what
is the reason that the current raw Ethernet interface is being
deprecated in favor of UHD? What are the advantages of UHD compared
to raw Ethernet? What are the disadvantages?

That is really 2 separate questions:

The first is raw ethernet vs. UDP/IP. UDP/IP allows packets to pass through routers. Raw ethernet requires root access on Linux, and is extremely tough to get at on Windows. UDP/IP plays nicer with the rest of the network stack.

The 2nd question is UHD vs. the drivers we had before. UHD consolidates all the control of the hardware in one place, so everybody doesn't have to reinvent those wheels. It allows you to switch between all of our motherboards and daughterboards (past, present, and future) transparently to the application writer and user. UHD gives a much better interface for timed transmission and reception, and other advanced features that just weren't available otherwise.


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