Company Confidential
29
Raveon Technologies Corp.
Example 3 (able to receive data from a sub-group, 1000
– 1999)
Sending to Destination Address =
1236
Receiving
RV-M29
Unit Address =
1234
Receiving
RV-M29
Address Mask =
F000
Result: Data will be received. 1236 AND
’ed with F000 is 1000. 1234 ANDed with F000 is
1000. The results of the ANDing perfectly match, and thus the data will be received.
Example 4 (able to receive from a sub-group, 34xx where xx is any two digits)
Sending Destination Address =
3410
Receiving
RV-M29
’s Unit Address =
3499
Receiving
RV-M29
’s Address Mask =
FF00
Result: Data will be received. FF00 means first two digits must match, and they do, so the
units will receive each other.
8.2.
TDMA Overview
TDMA, or
Time-Division-Multiple-Access
is a very effective way of allowing a lot of
radios to share one radio channel. Used extensively in GSM cellular and APCO
public-safety systems, TDMA excels at allowing quick and reliable access to radio
channels. It allows 2-10 times more radios to share a radio channel than
conventional carrier-sense methods. This allows 2-10 times more tracking radios
on one channel, as compared to radios that do not have TDMA capability.
The following diagram illustrates how it works.
When a
RV-M29
wants to report its position and status, it waits until its assigned
time-slot, and then transmits its data. By default, TDMA time slot positions are
assigned by unit-ID, so
RV-M29
with ID 1 uses the first slot, and ID 2 uses the
second slot, and so on.
A TDMA “
Frame
” time is the time it takes all units to transmit once. This is
configured with the
TDMATIME xx
command. The factory default is 1 second, so
every 1 second, each
RV-M29
may transmit. The TDMA frame must be set long
enough for all units to transmit. For example, if you have 5
RV-M29
s, and use
100mS TDMA slots, then the
TDMATIME
should be set to 1 seconds. The
simplest way to set the
TDMATIME
is to make it equal to the
TXRATE
, the rate
you wish to report position.
