Method of and apparatus for providing an interface between an analog facsimile device and a wireless network

An interface device for faxing documents over a wireless network includes circuitry for emulating the public switched telephone network (PSTN) for communicating with an analog fax machine. The circuitry receives and stores a document image from the fax machine. It then prompts a wireless transceiver to establish a call connection. Once a call connection is created to a destination fax through the wireless network the interface device transmits the stored document image. The inventive method includes the steps of communicating with a fax over by means of one protocol to receive a document image, storing the document image, and transmitting the document image by means of a second protocol.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to interface systems and more particularly to 
interface systems for coupling a facsimile device to a fixed wireless 
access type of network. 
2. Description of Related Art 
Radio communication devices are often being used along with or in 
replacement of conventional wireline telephone systems. These radio 
communication devices provide many advantages over wireline systems. One 
advantage relates to the supporting infrastructure. Radio communication 
systems are simpler and less expensive to deploy in comparison to 
conventional wireline systems. Additionally, radio communication systems 
often have lower maintenance costs. Finally, radio communication systems 
are economically feasible in those sparse areas where low demand for 
communication services does not justify the cost of installing a wireline 
network. 
In a fixed wireless access system (FWA), base stations form an interface 
between conventional wireline networks and wireless subscriber units. A 
subscriber unit is a user device which contains a radio transceiver for 
communicating with a base station. Subscriber units are often made to be 
compatible with ordinary wireline telephones. Typically, an ordinary 
telephone is plugged into the subscriber unit through a standard telephone 
connector such as an RJ-11 jack in place of being connected to the public 
switched telephone network. For conventional telephones, such a subscriber 
unit allows an individual to use the ordinary wireline telephone in 
conjunction with the subscriber unit to place or receive a call. 
Unfortunately, facsimile (fax) machines do not work well when merely 
connected to a subscriber unit or wireless transceiver. 
Fax machines posses an interface that uses analog modem tones (compliant 
with ITU Recommendations V.17 or V.29) and are designed to allow the fax 
machine to communicate over the public switched telephone network (PSTN). 
The messaging protocol used to exchange documents follows the standards 
set ITU-T Recommendation T.30 "Procedures for Document Facsimile 
Transmission in the General Switched Telephone Network". Collectively, the 
fax machines following these provisions are known as Group III (G3) Fax. 
These G3 fax machines are referred to herein as analog fax machines in 
contrast fax machines or computers which emulate fax machines which 
communicate over a digital medium. For example, one common digital 
messaging format is known as Class 2.0. In particular, data devices such 
as laptop and desktop personal computers often implement Class 2.0 
messaging formats for the communications through wireless transceivers. 
There are, however, no systems or device which allow common analog fax 
machines to transmit in a time division multiple access (TDMA) or code 
division multiple access (CDMA) transmission medium. There are several 
technical reasons. 
Current wireless transceivers are not compatible with the various analog 
fax protocols. For example, even if a wireless transmitter is capable of 
establishing a link with a fax machine, the fax machine is not designed to 
wait until a wireless communication link is established by the 
transceiver. Accordingly, the fax machine's internal logic will typically 
cause it to time out and drop the call while the transceiver attempts to 
establish a wireless communication link. For obvious reasons, this 
situation is unacceptable. What is needed, therefore, is an interface 
device capable of communicating with a fax machine and with a wireless 
transceiver in a manner which avoids the loss of data or the dropping of a 
call. 
SUMMARY OF THE INVENTION 
One reason that fax interface devices have not been developed for wireless 
transmissions is that facsimile protocols include certain sequences of 
events which are not readily compatible with common wireless protocols. 
For example, analog fax machines require the acknowledgment of a dial tone 
prior to the initiation of a fax transaction. Moreover, the signals which 
are transmitted initially are transmitted in the form of DTMF tones for 
sending the dialed digits. After a call is connected and a line is 
established between the fax machine and the receiving system (fax or fax 
emulator), the fax protocol continues and eventually the fax data is 
transmitted. Additionally, fax protocols include time constraints which 
are not sufficient for establishing a communication link over a wireless 
network. 
Accordingly, an interface device includes a processing unit for emulating 
PSTN functions for establishing a communication link with a fax machine 
and for transmitting and receiving signals according to a plurality of 
different protocols and memory to store a document image. The interface 
device is an independent device which is compatible with common fax 
machines as well as with CDMA and TDMA wireless transceivers. In general, 
the interface device receives and sends fax documents at one interface 
port using the T.30 protocol and transmits and receives Class 2.0 AT 
commands and digital signals which conform to IS-99 and IS-135 digital fax 
standards at another interface port. Accordingly, no new protocols or fax 
compatible CDMA and TDMA wireless transceivers need to be developed. 
In operation, the inventive method generally includes creating a 
communication link with an analog fax machine connected to a first part of 
the interface device by emulating a PSTN connection as well as the T.30 
protocol for analog fax machines. This includes simulating a dial tone as 
well as other tones and exchanging T.30 messages which serve to prompt the 
analog fax machine to complete the connection and to transmit fax data. 
The method further includes receiving the fax data, which represents a 
document image, and storing the data. In one embodiment of the invention 
signals are sent to a wireless transceiver connected to a second port of 
the interface device in one of a plurality of digital fax protocols to 
initiate a wireless communication link after the communication with the 
fax machine is complete. In a second embodiment of the invention, signals 
are sent to the wireless transceiver connected to the second port of the 
interface device to initiate a wireless communication link after at least 
one page of a document image has been received but before transmission of 
the entire document is completed by the analog fax machine connected to 
the first port. In this embodiment, the analog fax machine communicates 
over the first and second ports simultaneously. 
Once a wireless communication link is established according to a select 
wireless communication protocol (for example, GSM, TDMA and CDMA) and a 
signal is received from the wireless transceiver indicating the same, 
digital fax data is transmitted to the wireless transceiver for 
transmission to a receiving transceiver. As a part of completing the 
wireless communication link, the receiving wireless transceiver must 
create a communication link to the final destination. Accordingly, if the 
final destination is a fax machine or a computer emulating a fax machine, 
a communication line must be established with it. When the fax machine is 
ready to accept data, the receiving wireless transceiver informs the 
transmitting transceiver of the same. Accordingly, once the transmitting 
transceiver informs the interface device that a link has been established 
and that a receiving fax machine is ready to receive data, the interface 
device begins data transmission. Known protocols are used by the interface 
device, the wireless transceivers and the receiving fax machine to 
complete the communication link to initiate the data transfer. 
Accordingly, no specialized equipment is necessary other than the 
interface device disclosed herein in order to send faxes from an analog 
fax machine over a wireless network. Additionally, because the interface 
device communicates with he fax machine on one port and with a wireless 
transceiver over a second port, it is also capable of receiving faxes from 
the wireless transceiver storing the document image and then initiating 
communication with the analog fax to deliver the document. In this 
embodiment, the inventive method includes transmitting a ring to the 
analog fax machine to prompt it to respond to receive the call and the fax 
document.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
FIG. 1 is a functional block diagram of a communications network which 
includes a preferred embodiment of an interface device. Referring now to 
FIG. 1, an analog to digital fax converter (ADFC) 100 is connected between 
a facsimile device (FAX) 104 and a wireless transceiver 108. Additionally, 
the ADFC 100 is connected to a wireline telephone 112. As may be seen, the 
fax 104 and the telephone 112 are commonly connected to port 116. The 
wireless transceiver 108 is connected to ADFC 100 through ports 120A and 
120B. For the preferred embodiment, as shown in FIG. 1, port 120A is an 
RS-232 serial digital data port for transmitting data while port 120B 
consists of a phone jack, by way of example, an RJ-11 phone jack for 
carrying analog voice signals. 
Continuing to refer to FIG. 1, the fax 104 is connected to port 116 by line 
120. Line 120 is, in the preferred embodiment, a phone line suitable for 
an RJ-11 jack. Similarly, the telephone 112 is connected to the port 116 
by a line 124. The Line 124 also appropriate for an RJ-11 jack and which 
is used in the system of FIG. 1 to carry voice signals from and to 
telephone 112. 
The ADFC 100 is connected to wireless transceiver 108 by line 128 through 
port 120A and by line 132 through port 120B. Because port 120A is in the 
preferred embodiment, an RS-232 port, line 128 must be suitable for 
carrying RS232 transmissions. Similarly, line 128 must be appropriate for 
connecting to the RJ-11 jack of port 120B for the transmission of voice 
signals. 
Continuing to refer to the network of FIG. 1, the ADFC 100 includes a 
processor 140 which is connected to receive and transmit signals through 
port 116. Processor 140 includes a store 144 which is used to store 
information, and more specifically protocol information, for 
communications through port 116. For example, store 144 may be formed of 
read only memory internal to processor 140 which defines the various tones 
which are used by telephony devices in common public switched telephone 
networks (PSTNs). Such tones are typically used to prompt external devices 
such as fax machines or switches to respond in specified manners. 
Processor 140 is connected to store 148 which includes register areas 148A 
and 148B. As may be seen, processor 140 is connected to store 148 by line 
152. Register area 148A is for storing a document image. Register area 
148B is for storing protocol information used by the ADFC 100 in 
communicating with wireless transceiver 108. The store 148 also is 
connected to a processor 156 by line 160. Processor 156 communicates with 
the store 148 over line 160 for storing and reading document images as 
well as for obtaining protocol information for communications with 
wireless transceiver 108. Processor 156 is also connected to processor 140 
by line 164. Line 164 is used, in part, for the exchange of control and 
hand off information between processors 140 and 156. Finally, as may be 
seen, processor 156 is connected to transmit and receive signals through 
ports 120A and 120B. 
In operation, the ADFC 100 of FIG. 1 is operable to receive and transmit 
fax documents through ports 116 and 120A. Similarly, the ADFC 100 is 
operable to receive and transmit voice signals through ports 116 and 120B. 
In general, the ADFC 100 merely passes a voice signal received at port 116 
through to port 120B and vice versa. In contrast, received document images 
in the form of fax data are stored in register area 148A, regardless of 
whether the document image is received at port 116 or port 120A. 
Thereafter, the ADFC 100 transmits the stored document image through the 
other of ports 116 and 120A. In general, a document image is received on 
one port, stored and then transmitted through the other port. Thus, a 
document image received from the fax 104 is stored in store 148 and then 
transmitted to wireless transceiver 108. Similarly, a fax document 
received from wireless transceiver 108 is stored in store 148 and then 
transmitted to the fax 104. 
The processor 140 uses T.30 protocol information stored in store 144 for 
interpreting data signals received at port 116 and for generating various 
PSTN signals which are transmitted from port 116. These various protocols 
relate to the setup and completion of a call with an external fax such as 
G3 fax 104. Similarly, the processor 156 uses IS-99/IS-135 protocol 
information (Class 2.0) stored in register area 148B for interpreting and 
generating control and data signals through port 120A. Class 2.0 protocol 
information is the Electronics Industry Association and the 
Telecommunications Industry Association (EIA/TIA-592) protocol standards. 
Additionally, processors 140 and 156 exchange control signals over line 
164 to and from the other processor that a document image has been stored 
in store 148 and is ready for delivery to an external source. Signaling 
information, such as the called party number, is also exchanged by the 
processors 140 and 156 over line 164. 
FIG. 2 is a functional block diagram of an alternate embodiment of an 
analog to digital fax converter. Referring now to FIG. 2, the ADFC 200 
includes a first processor 140, a second processor 202 and a third 
processor 204. The processor 204 includes a store 208. In this alternate 
embodiment of the invention, the processor 204 is similar in structure to 
the processor 140 and includes a read only memory 208 for storing protocol 
information for use in communications with an external wireless 
transceiver 108 through ports 120A and 120B. In general, the functionality 
which previously existed in the processor 156 of the ADFC 100 is now 
distributed between the processors 202 and 204. Accordingly, the processor 
202 performs system control while the processors 140 and 204 are used for 
the transceiving of signals through the external input/output ports 116, 
120A and 120B. The processor 204 stores and receives document images from 
store 148 over line 212. 
FIG. 3 is a functional block diagram of a second alternate embodiment of an 
analog to digital fax converter. Referring now to FIG. 3, an ADFC 300 
includes a processor 304 which is connected to ports 116, 120A and 120B. 
The processor 304 also is connected to the store 308 by line 312. The 
store 308 includes a register area 308A, a register area 308B, and a 
register area 308C. Register area 308A is for storing a document image. 
Register area 308B is for storing protocol information for communications 
over port 116. The register area 308C is for storing protocol information 
for communications over ports 120A and 120B. In general, the protocol 
information stored in the register area 308B is similar to that stored in 
the store 144 of FIG. 1 and the store 208 of FIG. 2. As may be seen, the 
functionality of processors 140, 202 and 204 have been combined and are 
largely performed by the processor 304. Accordingly, the processor 304 
uses protocol information stored in the register area 308B for receiving 
and placing calls through port 116. Similarly, the processing unit 304 
uses the protocol information stored in the register area 308C for 
communications through ports 120A and 120B. As before, in operation, the 
processor 304 will receive a fax document image through port 116 and will 
store the same in the register area 308A. Thereafter, the processing unit 
304 will extract the document image from the register area 308A and will 
transmit the same over port 120A. Likewise, the processing unit 304 will 
receive a fax document image from port 120A and will store the same in the 
register area 308A prior to transmitting the faxed document image through 
port 116 to an external fax 104 (not shown herein). 
FIG. 4 is functional block diagram of a wireless network which includes a 
second preferred embodiment of an analog to digital fax converter. 
Referring now to FIG. 4, an ADFC 400 is connected to a telephone 112 by 
line 120 through the port 404A. Port 404A is a port formed of a telephone 
jack such as an RJ-11, and is similar to port 116. The ADFC 400 is also 
connected to a fax 104 through port 404B. Port 404B, similar to port 404A, 
is formed of a telephone jack and is connected to the fax 104 by line 408. 
In structure, the ADFC 400 is similar to the ADFC 100 shown in FIG. 1. 
Namely, it includes a processor 140, a processor 156 and a store 148 which 
includes register areas 148A and 148B. Similar to the ADFC 100, the 
processors 140 and 156 of the ADFC 400 exchange control information over 
line 164. One difference between the ADFC 400 and the ADFC 100, however, 
is that the processor 140 communicates with the telephone 112 and the fax 
104 through separate ports rather than through a single port. As will be 
discussed herein this application, having different ports affects the 
operation of the ADFC 100 and the ADFC 400. As before, the ADFC 400 is 
connected to a wireless transceiver 108 by a line 128 and a line 132. As 
before, lines 128 and 132 support the RS-232 and RJ-11 ports, 
respectively. Wireless transceiver 108 communicates through wireless 
network 136. In general, the ADFC 400 operates in a manner similar to the 
ADFC 100, ADFC 200, and ADFC 300. Each ADFC receives a fax document by 
means of first protocol over a first port, stores the document image, and 
then transmits the document image through a second port by means of a 
second protocol. 
FIG. 5 is a sequence flow diagram which illustrates a method for faxing a 
document over a wireless network according to a preferred embodiment of 
the invention. Referring now to FIG. 5, a facsimile device 500 
communicates with a converter (interface device) 505 to setup a call (step 
510). Once the call is setup between the fax 500 and the converter 505, 
the fax 500 transmits a document image to converter 505 by exchanging 
messages and data following analog fax protocols (as specified in ITU 
T.30) (step 525). Typically, this fax data comprises a document image. 
This document image may comprise the entire document or just a part of the 
document (e.g., the first page). After the fax data transmission is 
complete, the call is terminated (step 530). Terminating the call includes 
disconnecting any reserved lines, and transmitting, from converter 505 to 
fax 500, a signal indicating "on-hook". The "on-hook" signal represents 
that converter 505 is, with respect to the foregoing call, now off line. 
After converter 505 receives a signal from fax 500 indicating that all fax 
data has been transmitted, converter 505 transmits signals to wireless 
terminal 535 to establish a call through it. In other words, converter 505 
sets up a call with wireless terminal 535 (step 540). While not shown 
explicitly herein, it is understood that wireless terminal 535 creates a 
wireless communication link with the wireless network in response to the 
fax call setup signals received in step 540. Once the fax call setup is 
complete and a communication link has been setup through the wireless 
network with a receiving fax device, fax data is transmitted from 
converter 505 to wireless terminal 535 (step 545). This fax data 
transmitted in step 545 corresponds to the fax data which converter 505 
received from fax 500. 
If, on the other hand, wireless terminal 535 is not able to setup a call, 
it transmits a signal indicating the same to converter 505 (step 550). For 
example, if a called party telephone is busy as indicated by the receiving 
wireless transceiver, then wireless terminal 535 transmits a signal to 
converter 505 in step 550 indicative of the same. A period of time after 
converter 505 receives the called party unavailable signal from wireless 
terminal 535 it attempts again to setup a fax call (step 555). Once the 
fax call is setup, the fax data is transmitted (step 545). As may be seen, 
therefore, the inventive method illustrated in FIG. 5 includes 
establishing a communication link with a first fax machine using a first 
communication protocol, receiving fax data, storing the faxed data, 
setting up a second communication link using a second communication 
protocol, and transmitting the faxed data. 
FIG. 6 is a sequence flow diagram which illustrates a second method of 
faxing a document over a wireless network according to a preferred 
embodiment of the invention. Referring now to FIG. 6, the wireless 
terminal 535 attempts to setup a call with converter 505 by transmitting a 
fax call setup signal (step 610). After a fax call is successfully setup, 
fax data is transmitted from wireless terminal 535 to converter 505 (step 
615). Once converter 505 has received a signal indicating that all fax 
data has been transmitted, it sets up the call with fax 500 (step 620). As 
before, if the call setup is unsuccessful because, by way of example, fax 
500 is either busy or does not answer, then the call setup procedures are 
repeated (step 625). Once a call is successfully setup between converter 
505 and fax 500, converter 505 transmits a document image to fax 500 by 
exchanging messages and data following analog fax protocols (step 630). As 
before, the inventive method includes communicating with a wireless 
terminal by means of a first protocol, receiving fax data, storing the fax 
data, setting up a call with a fax machine by means of a second protocol, 
and faxing the stored fax data thereto. 
FIG. 7 is a sequence flow diagram which illustrates a method for 
transmitting the faxed document over a wireless network according to a 
second preferred embodiment of the invention. Referring now to FIG. 7, a 
converter 700 (interface device) communicates with a fax 704 and a 
wireless terminal 708 to transmit a fax document over a wireless network. 
More specifically, the sequence diagram of FIG. 7 illustrates the method 
for transmitting a fax through a wireless network, which fax originated 
from a fax machine that is not connected to the public switch telephone 
network. As may be seen, the method is initiated when fax 704 transmits a 
signal to converter 700, which signal reflects "off-hook" (step 712) 
according to T.30 fax session protocol. The "off-hook" signal is one which 
fax machines typically produce to emulate the telephony signals which 
occur when a conventional wireline telephone is taken off hook. As is 
known by those skilled in the art, fax machines emulate certain wireline 
telephony functionalities to route a call through the PSTN. Accordingly, 
because such emulations are typically embedded in the firmware of a fax 
machine, the inventive interface device also is adapted to emulate PSTN 
DTMF digit collection to communicate with the fax machine 704. After 
receiving the "off-hook" signal from fax 704, converter 700 generates a 
dial tone to fax 704 (step 716). Thereafter, fax 704 transmits a plurality 
of dialed digits in the form of DTMF tones. In response, converter 700 
also generates a call station ID (CSI) (step 720). The purpose of 
generating a call station ID is to identify the called fax machine 
(usually the directory number is sent and the calling fax machine displays 
it). The CSI is the beginning of the analog fax protocol following T.30. 
Converter 700 also generates a digital signal ID (step 724). In response 
thereto, fax 704 transmits a station ID (step 728), a digital command 
signal (DCS) (step 732) and a training sequence (step 736). Thereafter, 
converter 700 transmits a confirmation signal to fax 704 (step 740). At 
this point, the initiation of the T.30 fax session is complete. 
Accordingly, fax 704 transmits a document image followed by an Return to 
Command (RTC) (step 744). After the fax transmission is complete, fax call 
termination takes place. Fax call termination includes the transmission of 
a signal indicating the end of the procedure (step 748), a response 
thereto from converter 700 which confirms the end of procedure signal 
(step 752), and a signal from fax 704 to converter 700 indicating that it 
has disconnected or is "on-hook" (step 756). 
When converter 700 receives fax data from fax 704, it stores the data in an 
internal store. By way of example, store 148 of FIGS. 1 and 2 stores fax 
data. In a first preferred embodiment of the invention, converter 700 does 
not attempt to transmit or initiate transmit processes of the document 
image until it has been completely received document image from fax 704. 
Accordingly, converter 700 does not attempt to initiate procedures to 
transmit the document image until the RTC signal is received from fax 704 
in step 744. In a second preferred embodiment, converter 700 initiates 
procedures to transmit the document over a second port while the document 
is being received over a first port converted to the analog fax machine. 
In the embodiment, procedures to initiate transmission begin at a point in 
time after document image transfer has begun from the analog fax machine. 
Thus, sometime after the RTC signal is received in step 744, converter 700 
transmits an origination message to wireless terminal 708 (step 760). For 
example, the origination message might include an "ATDT" (dialed digits), 
and an FCLASS=2.0" signal as is commonly known to those skilled in the 
art. The wireless terminal then responds by returning the parameters of 
the call followed by "OK" (step 762). Thereafter, converter 700 transmits 
an "AT+FDTS" signal to wireless terminal 708 (step 764). Sometime after 
wireless terminal 708 receives the origination message in step 760 from 
converter 700, it initiates procedures to establish a call connection 
through a receiving wireless terminal to a final destination. Once the 
call is connected to the final destination point, wireless terminal 708 
transmits a "CONNECT", "OK" signal to converter 700 (step 768). Once 
converter 700 receives the "CONNECT", "OK" signal, it transmits the 
document image and an RTC signal to wireless terminal 708 (step 772). The 
preceding messages and image data typically constitute an IS-99, IS-95 or 
IS-135 fax session. Once the transmission of the fax page data is 
complete, an end of procedure is signal is transmitted by converter 700 to 
wireless terminal 708 (step 776). Thereafter, the call is disconnected. 
Wireless terminal 708 indicates the same to converter 700 by transmitting 
a disconnect signal (step 780). 
As is clearly seen, the present invention is significant in the field of 
fixed wireless access networks. The present invention is believed to be 
especially effective when configured and employed as described herein, 
however, those skilled in the art will readily recognize that numerous 
variations and substitutions may be made in the invention and its use and 
configuration to achieve substantially the same results as achieved by the 
embodiments and, in particular, the preferred embodiment described herein. 
For example, the interface device described herein may be implemented as 
described as a stand alone device. Alternatively, it may be implemented 
either as a part of an analog fax machine or a wireless transceiver. Each 
variation is intended to be included in the description herein and forms a 
part of the present invention. The foregoing detailed description is, 
thus, to be clearly understood as being given by way of illustration and 
example only, the spirit and scope of the present invention being limited 
solely by the appended claims.