HDB3

1
HDB3

• Alan Mitford-Taylor

2
What is the issue with HDB3

• HDB3 systems can be adversely impacted by ADSL
  systems in same cable binder
• The IMP requires the separation of HDB3 and ADSL
• The draft STD requires
• Removal of HDB3, or
• Replacement of HDB3 as soon as reasonably
  practical, and reduced power on ADSL until
  removed.
• Chorus requires a process to remove HDB3 that
  reflects the need of end users for time to
  migrate to replacement services

3
What is HDB3

• HDB3 means high density bipolar of order 3 and it
  is a method of encoding data signals to ensure
  there are an equal number of positive and
  negative pulses.

• HDB3 provides several advantages over early
  systems
• No DC component to data signal enabled power
  feeding of repeaters
• Network synchronisation maintained
• Data errors easily detected.

4
What is HDB3 used for

• HDB3 has been used since the late 1960s as the
  signalling method for 2 Megabit/sec digital
  systems from exchange to exchange or exchange to
  end customer premise.
• These systems support
• Voice ISDN
• Data - WDDS
• Interconnect - Megalink

5
What is wrong with HDB3

• Nothing is wrong with HDB3, it is still fit for
  purpose
• It can be adversely impacted by ADSL systems in
  same cable binder
• STD requires
• Separation of HDB3 and ADSL, or
• STD requires Replacement of HDB3 as soon as
  reasonably practical, and
• Reduced power on ADSL until removed.

6
End Customer will be impacted by removal of HDB3
systems

• While there are many more ADSL circuits that the
  15,864 HDB3 circuits, there can be many end users
  affected by one HDB3 link
• Need to upgrade communications equipment
• May need to upgrade entire systems including
  premise wiring and CPE (phones terminals)
• Need to be able to choose their own timing and
  have plenty of notice
• Have to meet costs that are potentially
  unbudgeted and also earlier than expected

7
How can we mitigate impact of HDB3

• Chorus has designed pair selection process to
  avoid HDB3 binders until only choice
• All have opportunity to sell end users an
  upgraded system
• Where distance permits replace HDB3 span with
  alternative xDSL based systems

8
Long term view of HDB3

• Undertakings require progressive closure of
  legacy services based on HDB3 systems from
  December 2007 through to the end of 2009
• HDB3 will still be required for interconnect and
  voice mux systems after 2009, but in much reduced
  numbers mainly in non-urban areas
• Work with Customers to manage removal of HDB3
  systems where possible
• Sales opportunity for all to up sell end users