Re: [Discuss-gnuradio] Dynamic Channel bandwidth allocation

[Michael Ford]

If I can't change the bandwidth covered, that's okay, as long as I can be confident in that the analog RSSI will cover the constant ~30MHz that you say it does, and that I can cover different ~30 MHz chunks based on what I set the carrier frequency to be.

-Michael Ford-

On 7/25/06, Matt Ettus <address@hidden> wrote:

The way we have envisioned RSSI is as a 3-part measurement:
    Analog RSSI
    Digital RSSI in FPGA (from output of ADCs)
    Digital RSSI in host (computed however you like, from the
channelized signal sent over the bus by the USRP)

If you want to use the measured analog RSSI, it will measure whatever
passes through the analog channel filter.  You can only change that
bandwidth by changing inductors and capacitors.

Note also that analog RSSI is only on the RFX900, RFX1200, RFX1800, and
RFX2400.  The RFX400, TVRX, and DBSRX do not have that capability.

Matt

Michael Ford wrote:

> Matt,
>
> I'll actually want to be able to control how far I can detect
> interference from my carrier, and the carrier I'll be detecting
> interference from. Do I have no choice but to cover ~30Mhz at a time?
>
> -Michael Ford-
>
> On 7/25/06, *Matt Ettus* <address@hidden <mailto: address@hidden>> wrote:
>
>     Michael Ford wrote:
>
>     > So, I'm trying tomake a system where nodes communicate, not on set
>     > channels, but on as much of the spectrum as they can use based
>     on the
>     > level of interference. For example, we know that 802.11 divides the
>     > spectrum into 13 channels with the center frequencies set at 5MHz
>     > apart. In my ideal situation, a network with only two nodes would be
>     > able to use the entire spectrum to send data, a network with 4
>     nodes
>     > and two transmissions would divide the spectrum in half for each
>     > transmission, and so on and so forth.
>     >
>     > In order to do this, I need to be able to scan for interference at
>     > specific channels/frequencies to determine whether or not they're
>     > available. Before I get too deep into the project, is this even
>     > possible with the USRP motherboard and the RFX2400 transceiver
>     board?
>     > I know we have the RSSI circuit onboard, but I don't know on which
>     > frequencies it scans.
>
>     The RSSI on the motherboard will tell you the power within approx. +/-
>     15 MHz from your carrier.  You can also get a digital RSSI which will
>     tell you the power within your signal of interest.
>
>     Matt
>
>
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