Section 150-231-134
Revision 01
Page 4
B. FUNCTIONAL DESCRIPTION
6. OPERATIONAL CAPABILITIES
6.01
HiGain utilizes PairGain’s 2B1Q HDSL
transceiver systems to establish two full-
duplex 784 Kb/Sec data channels between the HLU-
231 and a remotely mounted HRU-412 HiGain
Remote Unit. This provides a total capacity of 1.568
Mb/Sec between the two units.
6.02
A block diagram of the HLU-231 is shown in
Figure 2. The HiGain HLU-231 receives a
1.544 Mb/Sec DS1 data stream from the DSX-1 digital
cross connect interface. The HLU contains a DS1
frame synchronizer controlled by an 8-bit
microprocessor that determines the type of framing on
the DS1 stream and synchronizes to it. The HLU-231
recognizes Superframe (SF) (including D4) or
Extended Superframe (ESF) framing. When the data
is unframed, the HLU-231 arbitrarily defines a frame
bit.
6.03
The HLU-231 contains a demultiplexer that
generates two parallel 784 Kb/Sec data
streams. The data streams contain HDSL frames that
are nominally 4704 bits (6 milliseconds) in length. The
HDSL frames contain a 14 bit Frame Sync Word
(FSW), 6 bit Cyclic Redundancy Check (CRC), 21 bit
operations channel and DS1 payload. The DS1
stream is separated into two parallel streams that
comprise the payloads of the HDSL channels. HDSL
channel 1 contains the DS1 time slots 1 thru 12.
HDSL channel 2 contains the DS1 time slots 13 thru
24 The 8 Kb/Sec frame bits of the DS1 stream are
included on both HDSL channels.
6.04
The two formatted HDSL channels are
passed to the HDSL transceivers which convert them
to 2B1Q format on the HDSL lines. The 2B1Q line
code is designed to operate in a full-duplex mode on
unconditioned pairs. The transceiver’s echo canceler
and adaptive equalizer receive the signal from the
remote end in the presence of impairments and noise
on the copper pairs.
Figure 2. HLU-231 List 3D Block Diagram. PairGain’s HDSL technology provides full-duplex services at standard T-1 rates
over copper wires between an HLU and an HRU, which comprise one HiGain system.
