Re: 'Real' cost ?

On Sat, 16 Aug 2008 09:58:54 +0100, LR <lrme@xxxxxxxxxxx> wrote:

DanS wrote:
Jeff Liebermann <jeffl@xxxxxxxxxx> wrote in

There is a pdf of the camera locations and on a quick look there are
some differences between the two.
Thanks. That's much better. What I wanted to do is see how 60
cameras would play if they were all mesh. I'm assuming they're all at
street level, which means that the cameras have to be at intersections
and looking down an "urban corridor" to get a shot at the next MESH
node. A quick look at the map seems to indicate this is not the case.
Either I'm missing something or this system can't be done with
wireless mesh (at street level).

I'm thinking it is not really a true mesh network, but broken down into
segments of x amount of nodes that can cross communicate, and then
backhauled back somehow.

There doesn't appear to be any mention of where the other 37 firetide
nodes were deployed and since these are probably used for
interconnectivity it is impossible to get a realistic idea of the number
of nodes used to cover each area.

Good point. The cameras might be at ground level, while the mesh
nodes (repeaters) might be on the rooftops. That would work, but
without knowing the repeater locations, there's not much I can do in
the way of guessing channel loading and preformance. 2:1
camera:repeater seems a bit overkill, but that leaves room to add more
cameras later without adding repeaters. It also deals with the rather
wide spread of the cameras.

Incidentally, the 4.9GHz band is only 50MHz wide. (4.940 to 4.990GHz)
with a mix of 1 and 5 Mhz channels. To get full motion 30fps (about
37MHz at 640x480) "evidence quality" video, they would need to use the
maximum 20MHz channel bandwidth. That leaves one more 20Mhz
"channel", plus the assorted 1Mhz channels. My guess(tm) is that the
RFC (regional frequency coordinators) reserved the 2nd 20MHz for other
users. That means they're running this thing on store an forward with
a single radio. Yech.

Any clue where I might find the original RFQ document?

Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D
Santa Cruz CA 95060
Skype: JeffLiebermann AE6KS 831-336-2558