PairGain 150-1236-54, Руководство пользователя

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Section 150-319-254
Revision 02
Page 3
TABLE 1. HDSL CABLE LOSS
Cable Gauge
Loss @ 260
kHz(db/km) Ohms per km
26/0.4 mm 13.94 272
24/0.51 mm 10.47 171
22/0.61 mm 8.14 105
19/0.91 mm 5.74 52
TABLE 2. HIGAIN E1 RANGES (KM) ON
UNIMPAIRED CABLES VS AVERAGE
MARGIN(M) IN DB
Cable Gauge M = 11 M = 7 M = 3
0.4 mm / #26 AWG 2.7 km 3.0 km 3.3 km
0.51 mm / #24
AWG
3.6 km 4.0 km 4.4 km
0.61 mm / #22
AWG
4.7 km 5.2 km 5.7 km
0.81 mm / #19
AWG
6.6 km 7.3 km 8.0 km
2. APPLICATIONS
2.01 The HiGain System provides a cost-
effective, easy-to-deploy method for
delivering G.703 High Capacity Digital Service
(HCDS) over metallic pairs. The fiber-like quality
service is deployed over two unconditioned, non-
loaded copper pairs. Conventional span repeaters
are not required. Cable pair conditioning, pair
separation and bridged tap removal, are also not
required.
2.02 The HiGain system operates with any
number of other G.703, Plain Old Telephone
System (POTS), digital or analog data service or
other HiGain Systems sharing the same cable
binder group. HiGain provides a means of quickly
deploying service in advance of fiber-optic
transmission systems. By using HiGain G.703, you
can connect service within a few days or even a few
hours. You can install fiber optic systems at a
leisurely pace and cut-over from HiGain when the
time allows. You can then easily remove the HiGain
and utilize it elsewhere.
2.03 Table 1 provides a guide for the loss of
various cable gauges at the HDSL line rate
of 260 kHz and 135 ohms. The table applies to the
HDSL cable pairs between the ELU and the EDU-
451 as well as between the EDU-451 and a second
EDU-451 or the ERU-412. Add 3 dB for each
bridged tap and 1 dB for each cable gauge change.
2.04 The ELU to ERU operating ranges, on
unimpaired cable pairs, are shown in Table
2 as a function of cable gauge and average margin.
2.05 The ELU-319, List 5D and 6D line units
support both one and two doubler
applications. For two doubler applications the ERU
must be locally powered. For one doubler
applications both the EDU and ERU can be line
powered.
3. FUNCTIONAL OPERATION
3.01 HiGain utilizes PairGain's 2-Bits-1-
Quaternary (2B1Q) HDSL transceiver
systems to establish two full-duplex 1040 Kbps data
channels between the ELU-319 and an ERU-412
HiGain Remote Unit or EDU-451 doubler unit. This
provides a total capacity of 2.080 Mbps between the
two units: 2.048 Mbps for the G.703 interface and 32
Kbps of overhead.
3.02 A block diagram of the ELU-319 is shown in
Figure 2. The HiGain ELU-319 receives a
2.048 Mbps data stream from the G.703 digital
cross-connect interface.
3.03 The ELU-319 contains a demultiplexer that
generates two parallel 1040 kbps data
streams. Each data stream consists of HDSL
frames that are nominally 4704 bits (4.5
milliseconds) in length. Each frame contains a 14-
bit Frame Sync Word (FSW), a 6-bit Cyclic
Redundancy Check (CRC), a 21-bit operations
channel and 16 of the 32 G.703 timeslots. The
demultiplexer provides frame synchronization for
each of the two HDSL channels. The multiplexer
and HDSL transceivers work under control of the
ELU-319 microprocessor and compensate for data
inversions caused by tip-ring reversals and for
channel swaps caused by pair reversals. The
HiGain system tolerates tip-ring reversals, HDSL
cable pair reversals but does not tolerate split pairs.
3.04 The two formatted HDSL channels pass to
the HDSL transceivers, which convert them
to 2B1Q format. The 2B1Q line code operates in
full-duplex mode on unconditioned pairs. The
transceiver's digital echo cancelers and adaptive
equalizers receive the signal from the remote end in
the presence of impairments and noise on the