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This application is related to application Ser. No. 07/677,717, filed Mar.
29, 1991, entitled "Interactive Sequencing Method for ETC Systems", which
is incorporated herein by reference.
FIELD OF THE INVENTION
This invention relates generally to telecommunication systems and, more
specifically, to a system for transmitting non-conventional data over a
signalling channel such as a D-channel of a Signalling System Number 7
network which is typically part of an Integrated Services Digital Network.
A specific and preferred embodiment of this invention relates to a method
for transmitting transactions such as authorization requests in an
electronic ticket capture (ETC) system having a plurality of remote
terminals and at least one host computer, in which the remote terminals
communicate with and transmit such transactions to the host computer over
the ISDN network and, in particular, over the signalling channel.
BACKGROUND OF THE INVENTION
1. Conventional ETC Systems
A wide variety of payment schemes may be employed by the consumer to
purchase goods or services. For example, a consumer may use credit cards,
debit cards, personal checks, cash, etc. In accepting any or all of the
non-cash forms of payment, it is important that the retail establishment
be assured that the credit which it extends to the consumer is within the
limits specified by the financing service and that the consumer is current
in payments made to the financing service, or that the consumer's checking
account and payment history are sufficient to warrant acceptance of a
personal check. For these reasons, a variety of services have been
established which enable a retailer to perform some type of credit check
in a non-cash transaction. Particularly in the case of credit cards, this
may include the circulation of pamphlets or other listings indicating the
account numbers of credit cards which are not to be honored for various
reasons, including poor credit risk and theft. However, such listings are
generally cumbersome in use, and exhibit an inherent time lag between
distribution of the pamphlets and their actual use which can result in the
erroneous acceptance of a charge. Additionally, such pamphlets are not
readily applicable to the verification of personal checks.
As a result, a variety of automated systems have been developed which
enable a retail merchant to communicate with the company issuing the
credit card (or its representative), or a company which will guarantee the
personal check or otherwise extend credit, to obtain an immediate
indication as to whether or not the credit card or check should be
accepted or rejected. Such systems may take the form of a clearing house
which, in response to a conventional telephone call, provides verification
against listings it maintains at the clearing house. More recently, such
systems employing voice communications have been replaced with automated
dial-up systems. Such systems automatically read magnetic markings on the
credit card or check and transmit data over the conventional voice
telephone facilities to interrogate a database as to whether or not the
credit card or check may be accepted. These systems are generally known as
electronic ticket capture (ETC) systems.
A conventional ETC system employs a plurality of remote terminals which
communicate over conventional telephone lines with at least one host
computer. Such an ETC system is used to electronically process credit
sales and the like. Typically, such remote terminals are located at retail
establishments and are referred to as point-of-sale (POS) terminals. These
POS terminals provide the host computer with information relating to a
variety of transactions such as sales, returns, authorizations, deposit
inquiries and voiding of a previously entered transaction.
Of particular interest to the present invention, an authorization
transaction typically seeks approval from the host computer for the
extension of credit as in credit card sales. An authorization may be
performed alone or in conjunction with other transactions such as sales.
Transactions which require authorization from the host or which
communicate with the host while the transaction is performed, are referred
to as on-line transactions. For example, transactions in which a consumer
is given credit, e.g., those in which an amount is charged to an account,
typically need to be authorized by the host; therefore, such transactions
are generally performed on-line. Transactions which may be performed at
the remote terminal and which do not require interaction with the host
when such transactions are performed, are referred to as off-line
transactions.
Each on-line transaction typically involves a conventional telephone call
to the host for approval at the time the consumer attempts the
transaction. Since off-line transactions do not require communication with
the host when the user attempts the transaction, the cost of the telephone
call associated with that transaction is saved. However, such off-line
transactions eventually need to be communicated to the host. Typically,
these off-line transactions are transmitted to the host during end-of-day
processing. End-of-day processing is a procedure in which the information
related to off-line transactions is transmitted to the host and checked
for errors, errors are corrected to the extent possible, and databases are
updated, etc. Of course, a telephone call is still required for
transmitting off-line data, but the cost of such a call is less than the
cost of making a call for each off-line transaction. Such telephone calls
are conventional in the sense that a communication link is established
between the calling station (i.e., remote terminal) and the called station
(i.e., host computer) as in a conventional station-to-station phone call
when the called station places its phone or modem in an off-hook state in
response to the call from the calling station.
While they reduce the need for human intervention in the verification of
credit transactions and decrease delays in compiling and accessing a list
of unacceptable account numbers, such automated systems are still subject
to a number of drawbacks. Such drawbacks include the high cost of
transmission, the need to establish conventional telephone calls, high
data transmission errors, lengthy and complex end-of-day processing,
inadequate error detection and error recovery schemes, and limited
capabilities of the POS terminals.
2. ISDN and SS7 Protocol and Architecture
Integrated Services Digital Network (ISDN) is being promoted by telephone
companies in an effort to improve quality and capacity of
telecommunications network and provide a variety of services. ISDN
specifications have already been introduced by the CCITT, the
international communications standards committee. In the U.S. and Canada,
subsets and minor variations of these standards are being defined by the
major central office equipment vendors. ISDN is generally defined as a
network that provides end-to-end digital connectivity to support a wide
range of telecommunication services, including voice and non-voice
services, to which users have access by a limited set of standard customer
interfaces.
The technical concept of ISDN is implemented by using the existing
telephone lines to carry a digital signal instead of the conventional
analog voice signal. In one embodiment referred to as the basic rate
interface (BRI), the digital information is transmitted over three
multiplexed channels. In this illustrative embodiment, two 64 kilobits per
second (kbps) bearer channels (referred to as "B" channels) are provided
for voice or data calls, and one 16 kbps signalling channel (referred to
as the "D" channel) is provided for exchanging control information between
user and network. Another embodiment, referred to as the primary rate
interface (PRI), employs twenty-three B channels and one D channel.
Implementation of ISDN requires new central office switching and
transmission equipment, and sometimes dramatically different terminal
equipment (e.g., telephones, modems, data terminals) at the user or
subscriber end of the telephone line. At present, ISDN is available in
some cities in the U.S., and is widely implemented in Europe.
As noted above, in basic (BRI) ISDN service, the voice or data information
is carried by one of the two B channels of the ISDN. Call set-up
transactions necessary to make a connection, or link, are established via
the signalling channel. Messages sent to and from the central office on
the signalling channel contain the information defining the status of the
link and enable the call to be set up on the B channel.
FIG. 1 schematically depicts an Integrated Services Digital Network (ISDN),
which illustratively employs a common channel signalling network (CCS)
such as Signalling System 7 (SS7) for network control. Specifically, the
ISDN comprises a circuit-switched digital network 10, a channel-switched
digital network 12 and a common channel signalling network 14.
Illustratively, the common channel signalling network 14 is a Signalling
System Number 7 (SS7) network. An ISDN station typically accesses the
digital transport facilities via either one of two 64 kbps bearer (B)
channels 16. Access to the signalling network occurs on, for example, a 16
kbps signalling (D) channel 18. Alternatively, the D channel may be a 64
kbps channel or any other channel suitable for the transmission of call
set-up information.
Each of the two B channels is conventionally used to convey digitized voice
samples at the rate of eight thousand, eight-bit samples per second, or
data at a rate of 64 kbps. The D channel is used to convey signalling or
call set-up information in the form of signalling packets which effect
message signalling between ISDN stations. Such message signalling includes
signalling among various network nodes which typically control or define
path(s) between two ISDN stations.
To establish communication between any two stations in a network it is
necessary to organize the information being communicated in a form
mutually acceptable to all of the communicating entities. Such an
organization of information is referred to as a communications protocol.
Typically a communications protocol is designed as a structured set of
protocols which form a hierarchy. Each protocol of the hierarchy is
referred to as a "layer" or "level", and each layer is dedicated to a
specific function or a set of functions. SS7 uses a hierarchical protocol
which comprises the following protocols (or layers): message transfer part
(MTP), signalling connection control part (SCCP), transaction capabilities
applications part (TCAP) and ISDN user part (ISDN UP).
The overall function of the MTP is to transfer signalling messages between
signalling points (SPs) of the network in correct sequence and without
message loss or duplication. The MTP is subdivided into three layers: a
physical layer, a link layer, and a network layer. These layers correspond
to layers of the well-known open system interconnection (OSI) standard and
provide standardized connectivity, signalling and message-routing
functions.
The physical layer, also referred to as OSI layer 1, consists of
requirements on physical connection, power transfer, line transmission
receive and send signals, timing, framing, multiplexing, maintenance and
performance. In other words, this layer provides for transmission of
unstructured bit streams over physical medium. Each signalling data link
illustratively consists of two data channels providing opposite directions
of transmission.
The link or data link layer, also referred to as OSI layer 2, provides the
functions of message sequencing and message delineation into frames, error
detection and correction through retransmission of error frames,
subdivision of the signalling channel into a multiplicity of logical
channels, and data layer link recovery.
The MTP signalling network layer, also referred to as OSI layer 3, or more
generally as a signalling layer, provides the means to establish,
maintain, and terminate network connections at the ISDN user-network
interface. Such information is illustratively defined in terms of messages
exchanged over a signalling channel such as, illustratively, the D channel
of basic and primary rate interfaces. Layer 3 provides reconfiguration of
the signalling network during failures and controls traffic during
congestion periods. Layer 3 provides functions such as traffic management,
link management and route management. This layer makes the utilization of
underlying resources such as data link connections transparent to the
higher layers of the protocol.
The messages associated with layer 3 protocol control circuit-switched
and/or packet-switched connections. Layer 3 utilizes functions and
services provided by the data link layer (layer 2), including
establishment of data link connections, error-protected transmission of
data, notification of unrecoverable data link errors, release of data link
connections, notification of data link layer failures, recovery from
certain error conditions, and indication of data link layer status. These
functions and services provided by layer 2 are further defined in CCITT
Recommendations Q.920 and Q.921.
Specific functions performed by layer 3 include the following: processing
of primitives for communicating with the data link layer (a primitive
specifies the function to be performed and is used to pass data and
control information), administration of timers and logical entities (e.g.,
call-references which are used to identify the call or request at the
local user-network interface) used in call control procedures,
administration of access resources including B channels and packet-layer
logical channels, and checking to ensure that services provided are
consistent with user requirements (e.g., compatibility, addresses, service
indicators). The following general functions may also be performed by
layer 3: routing and relaying, network connections, network connection
multiplexing, segmenting (i.e., dividing a long message into smaller
messages) and blocking, error detection, error recovery, sequencing, and
flow control.
The Signalling Connection Control Part (SCCP) protocol exists at a higher
level or layer of the hierarchy than MTP and enhances the functionality
provided by MTP. More specifically, the SCCP layer of the protocol is
responsible for logical signalling connections, routing and management.
The ISDN UP provides call-related services which include interexchange
(IXC) signalling to support ISDN access signalling, circuit control and
specialized subscriber facilities such as calling party identification,
call status checking and trunk management. TCAP supports non-circuit
control applications such as service control point (SCP) access for number
translation and dial 800 services.
Two separate series of CCITT Recommendations (the I series and the Q
series) define the D channel protocol. In particular, the network layer
(layer 3) of the D channel protocol is defined in CCITT Recommendation
1.451 or Q.931, each of which is incorporated herein by reference. As
stated, this network layer provides call or connection set-up, alerting,
routing, and release of ISDN calls. The data link layer (layer 2) is
defined in CCITT Recommendation 1.441 or Q.921.
In general, the Q.931 protocol is responsible for call routing and control.
The protocol defines various messages that are transmitted between
stations such as POS terminals and the host computer by way of various
elements or nodes of the network. Further information regarding Q.931 and
1.451 may be found in "Data Communications Standards" Edition III,
McGraw-Hill, 1986, which is incorporated herein by reference.
Referring now to FIG. 2, there is depicted a generic Q.931 message
structure. As seen from FIG. 2, the data is organized as a plurality of
eight-bit bytes, referred to as octets.
More specifically, octet 1 comprises a "protocol discriminator" which
indicates that the message which follows is in accordance with the Q.931
standard. A portion of octet 2 comprises a "length of call reference
value" which indicates the length of the message which follows. Octet 3 is
a "call reference value" which identifies the call or facility at the
user-network interface to which a particular message applies. After the
"call reference value" a "message type" field is provided to identify the
type of message being sent.
The above elements are common to all Q.931 messages and must always be
present, while the content of the following octets are specific to each
message type and may include other mandatory and optional elements. These
other elements may be single octet information elements or variable length
information elements. The variable length elements typically comprise an
"information element identifier" to indicate the information elements
which follow, as well as a "length of information element" which indicates
the number of octets in the following information elements, and the
contents of the information element.
FIG. 3 symbolically illustrates an SS7 connection, or call set-up,
sequence. As is well known, the telephone network is organized
hierarchically. The lowest level of the network beyond a calling or called
station is typically referred to as an end office (EO), and the next level
of the network hierarchy is typically referred to as an access tandem (AT
or AT office). The basic function of the AT office is to provide
interconnection for a group of EOs and to provide access to the other
levels of network hierarchy such as interexchange carriers (IXCs) and/or
local exchange carriers (LECs).
More specifically, FIG. 3 illustrates a typical sequence of messages which
may be transmitted over the D channel in accordance with the Q.931
standard. This sequence illustrates the steps necessary for setting up a
telephone connection between a calling and a called station. The messages
issued and received by the calling station are depicted on the left-hand
side of FIG. 3 as 170; the messages issued and received by the called
station are depicted on the right-hand side of FIG. 3 as 172. The messages
generated by the SS7 network are depicted in the center of FIG. 3 as 174.
Traditionally, when a user places a telephone or modem associated with the
calling station off-hook, the calling station sends a "set-up" message to
indicate call establishment. The specific fields required for this message
and the messages mentioned hereafter are defined in the Q.931 protocol
specifications. In response to the "set-up" message the system sends an
acknowledgment (not shown) to the calling station and starts the
information exchange sequence. When all of the information, such as dialed
digits, is collected at the calling station, the set-up message is sent to
the called station directly if the stations are directly connected by a
local exchange carrier.
Alternatively, and as depicted in FIG. 3, the set-up message is sent to the
called station through the SS7 network if the stations are connected by an
interexchange carrier. In this case an initial address message (IAM) is
sent by the calling station to the called station after the caller
completes dialing the number of the called station. The IAM includes an
originating point code (OPC) identifying the calling station, a
destination point code (DPC) identifying the called station, and a
signalling link selection and circuit identification code (CIC) which
uniquely identifies the SS7-supported circuit employed, as well as other
information such as information encoded as part of the set-up message. The
IAM progresses from switch to switch until it is routed to the called
station at which time the called station rings.
In response, the called station then sends an "alerting" message to, for
example, the SS7 network. The "alerting" message indicates that the called
station received the set-up message. This alerting message is forwarded by
the SS7 network as part of an "address complete" message to the calling
station to indicate the reception of the appropriately addressed "set-up"
message by the called station. At this point a ring back signal associated
with the alerting message is returned to the calling station to indicate
that the called station is ringing. When the called station answers, a
"connect" message is sent by the called station to the SS7 network which
forwards the connect message as part of an "answer" message to the calling
station to indicate call acceptance by the called station. At this point,
the B channel voice circuit is established.
When one of the connected parties hangs up, a "disconnect" message (not
shown in FIG. 3) is issued. This message is an invitation to release the
connection and to free the network resources. The network resources,
previously used for the call which just ended, are then available for the
next call.
ISDN and SS7 have enabled the development of useful features such as
incoming calling line identification, often referred to as "caller ID".
Incoming calling line identification displays the caller's number for
incoming calls to a called customer station. The feature is implemented by
transmitting the calling line identification to the called customer
station in a data message. Such data message may be transmitted to an
analog station, for example, during a silent interval between ringing
periods.
Thus, it is known to display a calling party's number at a called party's
station prior to placing the called party's phone off-hook. However, such
communication is severely limited in the nature of the information which
may be transmitted to the called party. Moreover, the called party must
still place his/her phone off-hook to enable any meaningful communication.
Additionally, known systems are limited to one-way signalling
communication of information useful to a user such as a calling party's
number. That is, the called station is incapable of sending equivalent
information back to the calling station.
SUMMARY OF THE INVENTION
This invention relates to a communication system for exchanging information
between a remote terminal and a host terminal over a signalling channel of
an ISDN network without the need to establish communication over voice or
data channels of the ISDN. More specifically, this invention relates to a
communication system which transmits credit transactions such as
authorization requests from a remote terminal to a host computer,
processes such transactions, and transmits a response back to the
terminal, in which all such communication is performed over a signalling
channel of ISDN.
One particular embodiment relates to a method of exchanging information
between a host computer and at least one remote terminal comprising the
steps of sending a first message from the remote terminal to the host
computer over a signalling channel of an ISDN network, sending a second
message from the host computer to the terminal over the signalling
channel, and sending a third message from the host computer to the
terminal over the signalling channel. In this embodiment, the first
message contains data representing an information element which contains
encoded information to be communicated to an application running on the
host computer, the second message is sent in response to the first
message, and the third message is sent in response to the first message
and typically includes a disconnect message. Advantageously, the exchange
of messages between the host computer and the terminal is accomplished
without establishing communication over any non-signalling channel
provided by the ISDN network.
Preferably, such an embodiment includes the steps of processing the
information element communicated to the host, and interacting with at
least one database accessible by the host to determine whether a
transaction is to be authorized. In this embodiment, the first and second
messages correspond respectively to "set-up" and "alerting" messages in
accordance with the Q.931 standard.
In one specific implementation, an authorization request is encoded as the
contents of an information element of the first message and authorization
information such as an approval or denial or an authorization code is
encoded as the information element of the second or third messages.
Another embodiment relates to a transaction processing system comprising a
host computer system, a plurality of remote terminals, and a network for
enabling communication between the host computer and the terminals, the
network providing each of the terminals with a plurality of multiplexed
communication channels, at least one of which channels is a signalling
channel. The host computer includes means for retrieving transaction data
from information transmitted to said host, and each of the terminals
includes means for generating a message to be communicated to the host
computer and means for interpreting a message received from the host
computer, the message communicated to the host including the transaction
data.
Each of the terminals includes means to exchange information with the
computer by sending and receiving messages over the signalling channel of
the network without utilizing other channels of the network. Each of the
messages includes a first portion for data required for network
communication by an appropriate protocol and a second portion for data
representing the information that is exchanged between the host computer
and the terminal.
Advantageously, the messages to be communicated to the host computer and
the messages received from the host computer are transmitted over the ISDN
network as part of a user-user information element formatted according to
the Q.931 standard, and the exchange of information between the host
computer and each of the terminals is typically accomplished solely over a
signalling channel such as in the D channel of the ISDN network.
Another embodiment relates to a method for transmitting a request related
to a consumer transaction from a merchant to a host computer and for
processing the request. This method comprises providing a terminal
connected to the host via an ISDN network, inputting consumer data
including account information identifying a consumer's account into a
memory of the terminal, and encoding an application message string, which
includes the consumer data, in accordance with an application-oriented
protocol, such that the message string can be interpreted by software
running on the host. The communication message is formatted according to a
communications protocol, which communication message includes the
application message string and data for controlling message transmission
across the ISDN network from the terminal to the host. The communication
message is then transmitted over a signalling channel of the ISDN network
to the host.
Once the host receives the communication, i.e., request message, it is
parsed so as to separate the application message string from the other
data in the request message. The message string is then interpreted in
accordance with the application-oriented protocol so as to identify and
process consumer data including consumer account information. Information
related to the consumer is then retrieved from the database, a response
message is generated on the basis of the retrieved information, and a
response communication message is sent over the signalling channel of the
ISDN network.
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