Telephonic communications – Centralized switching system – Switching controlled in response to called station...
Reexamination Certificate
1996-03-29
2003-06-10
Hong, Harry S. (Department: 2642)
Telephonic communications
Centralized switching system
Switching controlled in response to called station...
C340S002700, C340S870030, C370S227000, C370S228000, C370S244000, C370S524000, C379S009050, C379S022040, C379S221040, C379S279000, C379S333000
Reexamination Certificate
active
06577728
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to telephone communication systems and more particularly, to a method for providing automatic restoration of network access for user lines in the event of a failure.
BACKGROUND OF THE INVENTION
In modern telephone networks the use of digital technology has become widespread. Utilizing digital technology in telephone networks has a number of advantages. One advantage is that the digital transmission of data is less susceptible to noise, which improves the quality of the transmission. While another advantage is that the digital format is ideal for being implemented on solid state technology such as integrated circuits. This is significant because most of the developments in technology has been in this area.
In order to exploit the advantages of digital technology, new techniques and equipment had to be developed. These new developments have included new modulation techniques, digital switches and various digital interfaces.
An example of a system utilized in digital telephone networks is shown in
FIG. 1
, which is known as a Digital Loop Carrier or an Integrated Digital Loop Carrier (IDLC) system
10
. The IDLC system
10
is utilized to couple subscriber lines
22
,
24
,
26
,
28
to a switching system
12
, such as an EWSD® switching system, which routes calls from the subscriber lines
22
,
24
,
26
,
28
to other parts of the phone network.
The IDLC system
10
includes a remote digital terminal (RDT)
30
which interfaces the subscriber lines
22
,
24
,
26
,
28
to a number of 1.544 MPBS highways
14
,
18
. The 1.544 MPBS highways
14
,
18
are also known as Digital Signal Level
1
lines (DS
1
) and are utilized to carry calls from the subscriber lines
22
,
24
,
26
,
28
to the switching system
12
. Each DS
1
includes 24 individual 64 KBPS digital signal carrying facilities, which are also known as Digital Signal Level
0
lines (DS
0
). For discussion purposes, only one of the 24 DS
0
s is shown per each DS
1
.
The RDT
30
is utilized as an interface to assign and connect the DS
0
s to the subscriber lines. The assignment and connection of the DS
0
s is either accomplished on a per call basis or on a provisioned basis. The per call basis is utilized when a large concentration of subscriber lines are required. This means that the RDT
30
has to dynamically assign and connect the DS
0
s to the subscriber lines. The subscriber lines utilizing a per call basis interface are known as concentrated lines
24
,
26
. While DS
0
s assigned and connected on a provisioned basis are known as dedicated DS
0
s and the connected subscriber lines are known as non-concentrated lines
22
,
28
. The dedicated DS
0
s
16
,
20
are nailed up which means semi-permanently connected to the respective subscriber lines
22
,
28
at the RDT
30
.
A problem with utilizing a provisioned type of interface is that the non-concentrated subscriber lines
22
,
28
often lose access to the network. Very often this is caused by a failed or blocked DS
1
, which causes the DS
0
s to become unavailable to the subscriber lines. This is a serious problem since the subscriber lines connected to the blocked DS
1
are unable to be utilized to make calls. The DS
1
s are often blocked due to technical problems or maintenance purposes.
The above discussed problem is partially removed by incorporating DS
1
protection switching capability within the RDT
30
. An example of a IDLC system having DS
1
protection switching is shown in FIG.
2
. In such a system, a standby DS
1
36
is reserved in the event one of the other DS
1
s
32
,
34
fail or is blocked. When a DS
1
fails, the traffic from that DS
1
32
is switched to the standby DS
1
36
as shown in FIG.
3
. Thus, the DS
1
protection switching partially solves the problem of a non-concentrated line losing access. However, the problem remains if a subsequent DS
1
34
fails before the previous failed DS
1
32
is repaired as shown in FIG.
4
. In this situation, the non-concentrated line
40
loses access. Thus, DS
1
protection switching is inadequate when there are consecutive DS
1
failures within a IDLC system.
It is therefore an object of the present invention to provide a method of providing continual network access to subscriber lines even in the event of consecutive DS
1
failures within a Digital Loop Carrier system.
SUMMARY OF THE INVENTION
The aforementioned problems are obviated by the present invention which provides a method for enabling automatic restoration of network access for user lines within a communication system. The communication system includes said user lines interfaced with groups of transmission lines, each of said group of transmission lines including dedicated transmission lines which are connected to said user lines, idle transmission lines and reserved transmission lines. The method comprises distributing said dedicated transmission lines among said groups of transmission lines; providing a number of said reserved transmission lines from among said groups of transmission lines; identifying said user lines which have a dedicated transmission line in a group of transmission lines that fails; and coupling each of said identified user lines to a respective available transmission line in another group from the idle and the reserved transmission lines therein.
The method may also include the step of delaying coupling of said identified user lines if a sufficient number of said idle and reserved transmission lines are not available. The method may also include the step of delaying coupling of an identified user line if an idle and reserved transmission line is not available.
Advantageously, the method of the present invention reprovisions the non-concentrated subscriber lines of a Digital Loop Carrier system to the DS
0
s of the still functioning DS
1
s in the event of a DS
1
failure. Thus, the non-concentrated lines have continuous access to switched based services even if the DS
1
s carrying dedicated DS
0
s fail.
REFERENCES:
patent: 4197427 (1980-04-01), Hutcheson et al.
patent: 4455645 (1984-06-01), Mijioka et al.
patent: 4511762 (1985-04-01), Stockdale
patent: 5509065 (1996-04-01), Fitzgerald
patent: 6031906 (2000-02-01), Rao
patent: 6084853 (2000-07-01), Rao
patent: 6115355 (2000-09-01), Rao
Hong Harry S.
Siemens Information and Communication Networks Inc.
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