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

[Matt Ettus]

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.

Matt