Note: Descriptions are shown in the official language in which they were submitted.
CA 02279067 1999-07-29
11P257CA
yIRTUAL PHONE LINE ACCESS DEVICE
FIELD OF THE INVENTION
This invention relates to the field of
telephony, and in particular to a method for providing
telephone line access to digital communication services.
BACKGROUND TO THE INVENTION
With the deployment of wide bandwidth digital
communication services, such as cable modems, digital
subscriber lines (DSL) and wireless communication
networks, multiple voice or data calls can be made over
a single medium, such as a wire pair, fiber or coaxial
cable. An analog to digital telephone interface to a
system which provides this service is used.
A typical subscriber today has a digital
interface which routes all traffic from that subscriber
to the digital network service to which the subscriber
has subscribed. However, we have discovered that only
some kinds of telephone traffic are suitable or
desirable to be carried over such digital networks. For
example, it may be advantageous or cost effective for
wide band (e. g. TV telephone or massive data signals),
or toll voice signals, to be carried by the digital
communications network (DCN), and toll-free calls and
voice signals carried by the public switched telephone
network (PSTN). Alternatively, the DCN may become
overloaded, the DCN may be reserved for certain types of
calls, or the initiation of calls may fail.
With all calls from a particular subscriber
being routed to a DCN, it has been impossible to
discriminate between different kinds of calls. Previous
systems would not allow automatic routing over the PSTN
if the call over the DCN failed for unforeseen reasons.
CA 02279067 1999-07-29
Routing of calls over an alternate route required manual
intervention by a caller to dial a modified digit
stream.
SUMMARY OF THE INVENTION
The present invention provides a method of
automatically routing certain kinds of calls to a DCN
and other kinds of calls to the PSTN, in a seamless and
transparent manner. A code can be prestored preferably
at an interface to the DCN which indicates which kinds
of calls would be accepted by the DCN (which code can be
supplied from the DCN), or on presentation of a call to
be completed to the DCN, calls can be accepted or
rejected on a call by call basis. All calls which are
not accepted by the DCN are routed to a PSTN.
In the event a call which is accepted by the DCN
cannot be completed or otherwise fails, the interface
then routes the call to the PSTN for completion.
Reasons for rejecting a call can be that it is a
no revenue or low revenue call, that the DCN is
overloaded, that there is insufficient DCN bandwidth to
carry the call, that all destination trunks are busy,
that it is otherwise not cost effective to carry the
call over the DCN, that the DCN does not provide service
to a particular destination area, etc.
Thus for example the resources of the DCN can be
kept from having to handle low or non revenue generating
traffic.
It should be noted that in this specification,
it is intended that wireless communication networks,
cable telephone networks, and other digital
communications or data networks be construed to be DCNs.
In accordance with an embodiment of the
invention, a method of providing phone line access to a
2
CA 02279067 1999-07-29
digital communication network (DCN) comprises:
(a) storing a control code indicating at least
one call routing criterion in a memory,
(b) receiving a sequence of digits dialled from
a telephone line, which designates a called subscriber,
and
(c) processing one or more of the dialled
digits with the control code and routing the call to one
of a public switched telephone network (PSTN) and the
DCN for onward routing of the call to a called
subscriber's line.
In accordance with another embodiment, a method
of providing phone line access comprises:
(a) receiving a sequence of digits dialled from
a telephone line which designates a called subscriber,
(b) processing one or more of the digits and
offering the call to a DCN,
(c) receiving an indicator from the DCN which
is one of acceptance of the call and rejection of the
call,
(d) in the event of the indicator indicating
acceptance of the call, providing the call to the DCN
for completion, and
(e) in the event of rejection of the call,
setting up the call via a line to a PSTN for completion.
BRIEF INTRODUCTION TO THE DRAWINGS
A better understanding of the invention may be
obtained by reading the detailed description of the
invention below, in conjunction with the following
drawings, in which:
Figure 1 is a block diagram of a system for
implementing embodiments of the invention, and
Figure 2 is a more detailed block diagram of a
3
CA 02279067 1999-07-29
system for implementing embodiments of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Turning to Figure 1, a user takes a telephone 1,
which is coupled via a subscriber's line to a virtual
calling device 3, offhook. The virtual calling device
is coupled to both a digital service provider network
(DCN) 5 and to a PSTN 7. The PSTN is coupled to a
telephone 9 to which an initiated call is to be
directed.
The virtual calling device 3 returns dial tone
to the subscriber. The subscriber then dials the
directory number of the called subscriber in the usual
manner.
The virtual calling device 3 collects the digits
dialled, processes them, and then makes a decision which
can be based on the number which has been dialled, to
either route the call over the analog PSTN 7, or to a
DCN 5 for processing.
Alternatively, the call (or an indication of at
least some of the digits of the called subscriber's
directory number) can be routed to the DCN 5, which
makes the decision of whether to accept or reject the
call for completion over the DCN 5 and subsequently via
the PSTN 7.
The routing decision is made such that only
calls that the DCN service provider wants would be
placed over that DCN.
If the call is not wanted by the DCN 5, the
dialled number is sent to the analog PSTN 7, and the
telephone 1 of the calling subscriber is coupled to the
PSTN 7 via virtual calling device 3, to complete the
call. The dialed number and routing decision are then
logged to memory 23.
4
CA 02279067 1999-07-29
If the call is wanted by the DCN 5, the
processed data representing the called subscriber's
number is sent to the DCN 5, which sets up the call
through a combination of the DCN 5 and the PSTN 7. The
telephone call to the called telephone 9 is then
completed. The dialed number and routing decision are
then logged to memory 23.
If for any reason the called telephone 9 cannot
be reached via the DCN, the virtual calling device 3
detects that an error is occurring and logs that error
to memory 23. Virtual calling device 3 then sends the
called directory number to the analog PSTN 7, which
connects the calling telephone 1 to the PSTN 7 for
completion of the call.
IS Figure 2 is a more detailed block diagram of the
virtual calling device 3 in a system which can implement
the invention. The interface includes a line circuit 11
to which the telephone 1 is connected via a subscriber's
line 13. The virtual calling device 3 also includes a
digital subscriber's line circuit (DLS) interface 15
and a line circuit 17 which is connected via a line 19
to the PSTN 7. The DCN 5 is connected to the PSTN 7 in
a well known manner.
The virtual calling device 3 also includes a
register 21, a processor and associated memory 23, and a
switching circuit 25.
In accordance with one embodiment, a code which
designates which calls are not to be sent to the DCN 5
is stored in the memory 23. This code can be stored on
installation of the virtual calling device 3, manually
stored after installation, stored upon receipt from a
remote programming device connected to virtual calling
device 3, via the line 13 or the equivalent, a separate
5
CA 02279067 1999-07-29
programming line such as the Internet or other
programming line, or stored upon receipt from a digital
line from the DCN 5. When received from the DCN 5, the
code can be received via a digital channel on a digital
line circuit between the DCN and the line circuit 15, or
via a separate control or supervisory line or channel.
The digits dialled by the calling subscriber are
received by the virtual calling device 3 via line
circuit 11, and are stored in register 21. once at
least some of the dialled digits have been received, the
processor analyzes them with respect to the stored code,
to determine whether the call should be routed via the
DCN 5.
For example, if the initial digit is a "1" and
is not followed by "800" or "888" (indicating a long
distance call in North America which is not a toll free
call), the processor can control switch 25 to route the
call via digital line circuit 15. This can be done by
the processor waiting for all of the digits to be
received in register 21, formulating a message to the
DCN 3 which indicates the destination of the call, and
transmitting the message via a message channel to the
DCN3. The DCN can then indicate by a return message
whether it can complete the call (for example if it
operates in the called party region, if it is not
overloaded, etc.). Assuming that the DCN can complete
the call and returns a message to the processor of the
virtual calling device 3, it also reserves a line or
channel and indicates in the return message which
digital line or channel to be used for the call.
The processor control switch 25 to switch the
incoming call to the digital line circuit 15 indicated
in the message, and the DCN 5 carries the call via the
6
CA 02279067 1999-07-29
designated channel to an analog line circuit to the PSTN
7 in the area of the called subscriber telephone 9.
In the event the DCN 5 is overloaded or cannot
otherwise carry the call, it returns a message
indicating that it rejects the call. The processor 23
interprets that return message and controls switch 25 to
switch the call to analog line circuit 17, for provision
of the call to the PSTN 7. The line connected to line
circuit 17 is seized in a well known manner, and
processor 23 causes the stored digits in register 21 to
be sent via the seized line to PSTN 7 to complete the
call in a well known manner. In the latter case, the
virtual calling device 3 operates in a similar manner to
automatic diallers manufactured by Mitel, Inc.
It should be noted that the code which is stored
need not only indicate that the calls to be rejected are
long distance calls which are not toll-free, but can
include an indication of area codes, central office
codes and other codes such as other country codes, other
country code prefixes, etc., on which a decision for
rejection of calls can be based. For example, the code
stored can be plural codes contained in a database of
the actual digits which, if included as a prefix to the
dialled digits, would prompt a decision by the processor
to route calls to the PSTN. Alternatively or in
addition, the code can be an indicator which includes a
logical value and/or formula. For example, the code can
indicate that all calls which have in excess of a
predetermined number of digits should be rejected (which
might indicate that the major part of the revenue for a
call would be allocatable to a different carrier, for
example, due to it including a PIN number).
In another manner of operation, no code is
7
CA 02279067 1999-07-29
stored by memory 23. In this case, all calls are
offered to the DCN 5. The DCN analyzes at least some of
the digits of the call, and decides whether or not to
accept or reject the call based on various criteria such
as those noted above. The offer of the call can be sent
from the processor 23 to the DCN 5 via a data channel or
separate data line as described above, and the
acceptance or rejection reply signal transmitted back to
the processor also as described above.
In the event a call is offered to the DCN and
the call is accepted, yet the DCN does not complete the
call due to a fault or other reasons, this will become
evident to the processor 23 by for example the processor
monitoring the digital line circuit 15 and noting that
the call has not been completed within a predetermined
time period. In that case, the processor can switch the
call to analog line circuit 17 which leads to the PSTN 7
in place of the digital line circuit 15, to have the
call completed. In this manner a fault in the DCN 3 can
be overcome by the call being completed via the PSTN 7
in a manner which is seamless and transparent to the
calling subscriber.
Indeed, a combination of any or all of the
described embodiments may be used together.
A person understanding the above-described
invention may now conceive of alternative designs, using
the principles described herein. All such designs which
fall within the scope of the claims appended hereto are
considered to be part of the present invention.
8
