Functionality of the DRU
11-3
Wireless Solutions
DualMode 800 Enclosure
Maintenance Manual
MTX08
Figure 11-3
MCPA front panel layout
Functionality of the DRU
The TRU provides a Time Compressed Multiplex (TCM) interface with the
Integrated Cellular Remote Module (ICRM). It also provides dual-receive
paths and diversity switching, and controls the Operation, Administration,
and Maintenance (OA&M) functions for the DRU. Control and signaling
messages communicated between the ICRM and the TRU are through a TCM
D-channel. Voice and data signals are communicated between the ICRM and
the TRU through a TCM B-channel.
Depending on the mode, the AMPS or TDMA baseband signal generated by
the TRU in a DualMode 800 Enclosure is modulated in the TRU. The
modulated signal is then sent to the MCPA. The MCPA amplifies and
transmits the signal to the mobile in the appropriate AMPS (analog) or
π
/4
DQPSK (digital) format. The TRU receives composite RF signals from the
mobile, extracts embedded control messages, and routes the control and voice
signals to the ICRM.
Audio sensitivity of the TRU
In AMPS mode, as a speaker talks, the FM carrier varies as a function of the
audio waveform produced by the speaker’s voice. This variance is known as
the frequency deviation that corresponds to a specific audio level. Typical
audio levels range anywhere from -18 dBm0 to -22 dBm0.
For TDMA, the speech signal is encoded using the VSELP coding algorithm.
The VSELP codec per the IS-54-B standard is optimized for a value being
equated to an audio level of -18 dBm0. Therefore, if an AMPS radio is not set
to an audio sensitivity of -18 dBm0, there will be some noticeable contrast in
audio level (loudness) when handoff occurs between the two modes.
To minimize the contrast between the two modes, Nortel Networks
recommends that the audio level in an analog network be adjusted to -18
dBm0, corresponding to
±
2.9 kHz deviation, in each direction of
transmission. This recommendation concurs with the Joint Experts Meeting
as reported to the CTIA in March 1992. For TRUs working in the AMPS
OFF
ON
Pwr
Low
DISAB
.
Alarms
Off
On
RF ON
-5VDC
Reset
Pwr
LPA
+5VDC
Loop
Fail
Fail
Fan
Fail
+15VDC
+27VDC
VSWR
DC
High
Temp
Over
Status
Содержание DualMode 800
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Страница 6: ...vi Publication history Nortel Networks Confidential 411 2051 500 Draft 00 01 November 1999...
Страница 82: ...2 20 Periodic maintenance 411 2051 500 Draft 00 01 November 1999...
Страница 90: ...3 8 Test equipment and precautions 411 2051 500 Draft 00 01 November 1999...
Страница 100: ...5 6 Master Oscillator tests 411 2051 500 Draft 00 01 November 1999...
Страница 106: ...6 6 Antenna and transmission line tests 411 2051 500 Draft 00 01 November 1999...
Страница 116: ...8 4 Alarm Control Unit ACU tests 411 2051 500 Draft 00 01 November 1999...
Страница 138: ...10 2 ICRM tests 411 2051 500 Draft 00 01 November 1999...
Страница 200: ...12 10 Enclosure maintenance 411 2051 500 Draft 00 01 November 1999...
Страница 208: ...A 8 Appendix A Frequency table 411 2051 500 Draft 00 01 November 1999...
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