[evla-sw-discuss] Keeping track of spectral windows at the EVLA: SDM vs. BDF

[David Harland]

Hi, Michael.  Sorry for the delay in responding.  I've had the 
opportunity now to look at others' replies and provide the SSS (OPT) 
perspective, below.

Michael Rupen wrote:
> Hi folks --
> ...
> swbb is the "baseband ID" in the SDM sense.
>
>   ...
>
>   2. The BDF and the SDM use the BasebandName enumeration:
>
>        BB_1  BB_2  BB_3  BB_4 BB_5  BB_6  BB_7  BB_8  NOBB
>
>     I propose adding more useful EVLA names to this enumeration:
>
>        A1/C1_3BIT  A2/C2_3BIT   A/C_8BIT
>        B1/D1_3BIT  B2/D2_3BIT   B/D_8BIT
>
>     Part of the point here is to avoid confusion with WIDAR's baseband 
> IDs,
>     which are *not* the same (though they are closely related).

Anything here s/b fine w/ SSS.  As others pointed out, the '/' char s/b 
eliminated.  As Barry pointed out SSS uses A0/C0 for 8-bit.  This was a 
suggestion of Walter's from 2007 (i actually found the email) that SSS 
adopted.  Best case scenario for SSS: A0C0, A1C1, etc, or AC0, AC1, etc.

>
>     ...
>
>   3. The required ascending order is then:
>
>        BB_1  BB_2  BB_3  BB_4 BB_5  BB_6  BB_7  BB_8  NOBB
>        A1/C1_3BIT  A2/C2_3BIT  A/C_8BIT  B1/D1_3BIT  B2/D2_3BIT  B/D_8BIT

If the use of "0" is adopted (as in A0C0), then it would be nice to just 
sort these alphabetically, meaning the 8-bit A/C pairs would precede the 
3-bit A/Cs.

> ...
>
> Of course this begs the question of who comes up with swbbName and 
> swIndex
> to begin with.  This seems properly left to the OPT: there is enough
> information there, and these values can be determined independently for
> every scan.  

That's fine.

> It would be preferable to have a deterministic algorithm for
> doing so.  For swbbName this is trivial.  For swIndex within a given
> swbbName I propose:
>
>   1- sort by the lower edge of the lowest frequency channel in each 
> subband
>     (to match the ALMA ACA correlator)
>   2- for remaining matches, give the lower swIndex to the SpW with
>     the narrower channels
>   3- for remaining matches, give the lower swIndex to the SpW with the
>     fewer total channels
>   4- at this stage we have only exact matches left.  If the OPT or 
> whatever
>     is explicitly setting the StB filter to be used, the lower filter 
> gets
>     the lower swIndex.

Sonja made comments about #4; so we can use the VCI SB ID instead here.  
Any issue w/ replacing 2 & 3 w/ the SB's bandwidth?  So, sort keys would 
be:  low sky frequency edge, then BW, then SB ID.