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Re: [Discuss-gnuradio] Queries regarding FPGA
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] Queries regarding FPGA |
Date: |
Mon, 27 Feb 2006 09:04:54 -0800 |
User-agent: |
Mutt/1.5.9i |
On Mon, Feb 27, 2006 at 08:28:56AM -0800, Thomas Schmid wrote:
> Isn't one of the problems that Linux is not a real time os, i.e.,
> exact time scheduling is impossible? As far as I know, linux timers
> have an accuracy of 1ms (i.e. 1 jiffie in the kernel). If you want to
> have shorter delays, you use the udelay function and do a busy wait.
> Or is there something that I am missing?
This is basically true. However, it's possible to implement finer
timing granularity with the assistance of external hardware, e.g., the
USRP. One could imagine sending a packet of data to the USRP with a
header on it that said, "Do not transmit until time = X", where time
is measured relative to a high speed counter on the board.
Also, part of what is being discussed is getting rid of excess
latency. This will shorten the typical round-trip loop time. It
doesn't have to be "hard-real time", just good enough. It's also
possible to design MAC's that don't require extremely tight control
loops. 802.11 a/b/g RTS/CTS isn't one of them. Designing better MACs
is a very active research topic.
Eric
- Re: [Discuss-gnuradio] Queries regarding FPGA,
Eric Blossom <=
- Re: [Discuss-gnuradio] Queries regarding FPGA, Stephane Fillod, 2006/03/01
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Eric Blossom, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Frank Brickle, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Eric Blossom, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Frank Brickle, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Eric Blossom, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Robert McGwier, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Eric Blossom, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Frank Brickle, 2006/03/08
- Re: [Discuss-gnuradio] SCHED_FIFO and NPTL, Eric Blossom, 2006/03/08