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Reverse Path Troubleshooting: Evaluating TDMA Return Path Signals

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likelihood of this occurring, the transmitter should be configured such that

the video signal input level is at approximately 0 dBmV. In the event that

instrument related intermodulation occurs, the reverse channel plan may be

set up such that the frequencies at which the intermod products appear are

not included. Alternatively, an SDA-5510 can be used. This instrument is

used for reverse testing only, and as no forward signals are present on its

input, it is not susceptible to this phenomenon.

Time Division Multiple Access (TDMA) is a term commonly used in reference

to D-AMPS or IS-54B mobile telephone systems. Time Division Multiple

Access implies a signal assigned to a particular frequency that has multiple

time-slots for multiple transmitters.

TDMA modems have specifically assigned times to send and receive

information. The controller deciphers the messages by knowing when each

modem is talking.

Fig. 5-3 shows how TDMA timing works. As you can see, in this scheme

each user is assigned a distinct time slot.

Fig. 5-3 Nominal TDMA Timing

TDMA signals were introduced to the commercial electronic world a few

years ago with the advent of digital cellular phones. Data compression and

EVALUATING TDMA RETURN PATH SIGNALS

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