Abstract:
A gateway interface between the public switched telephone system (PSTN) and cellular network. The gateway interface provides a conversion function between the SMS text messaging protocol and TD device text messaging protocol. The conversion function includes appropriate queuing and timing features that allow the SMS and TD functions to communicate. In an embodiment of the invention, the method and apparatus is implemented as a stand-alone gateway. The gateway may be implemented anywhere there is access to the public switched telephone network (PSTN) and coverage by a cellular system having short messaging service (SMS) capability.

Description:
CLAIM OF PRIORITY FROM A COPENDING PROVISIONAL PATENT APPLICATION 
     Priority is herewith claimed under 35 U.S.C. §119(e) from Provisional Patent Application 60/159,523, filed Oct. 15, 1999, entitled “TD-SMS Messaging Gateway,” by George Bernhart, Douglas Deeds, Paul Kearney, Jari Kiuru, and Kari-Pekka Wilska. The disclosure of this Provisional Patent Application is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to text messaging in a telecommunication system and, more particularly, to a method and apparatus for providing text messaging between mobile handsets and TD devices in a telecommunication system. 
     BACKGROUND OF THE INVENTION 
     Telecommunication devices for the deaf (TDD) have been developed that allow deaf persons to communicate by text messaging through the public switched telephone network (PSTN). The most common type of TDD is a telecommunication device (TD) at which a user may type in text messages for transmission and read received messages on a screen printout. A TD is fixed in location and is intended for communication with other TDDs over a landline network in an interactive manner. TDs commonly communicate according to the Electronic Industry Association&#39;s (EIA) “Telecommunications Devices for the Deaf” PN-1663 Standard (PN-1663). 
     A TDD, operating according to the PN-1663 Standard, communicates through the PSTN by transmitting and receiving strings of 1s and 0s that are encoded as either Baudot or ASCII codes. For Baudot coding, a 1 is transmitted through the PSTN as a 1400 Hz signal and a 0 is transmitted as an 1800 Hz signal. For ASCII coding, an originating TDD transmits a 1 through the PSTN as a 1270 Hz signal and a 0 as a 1070 Hz signal, and an answering TDD transmits a 1 as a 2225 Hz signal and a 0 as a 2025 Hz signal. 
     Recent advances in communication technology have resulted in cellular systems and technology that free users from the typical restraints of conventional landline telephone use. These advances include small, lightweight, portable, wireless phones that may be carried and used to communicate anywhere cellular service is provided. Present wireless phones have the capacity to send and receive short-text messages through a short messaging service (SMS). The SMS is standardized according to the standard in which the system operates. Unlike TDD systems using TD devices, SMS systems do not operate interactively over a circuit connection between communicating devices. SMS systems operate according to a store-and-deliver service, and SMS text messages have a fixed character length. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for providing text messaging between mobile handsets and telecommunication devices in a telecommunication system. The method and apparatus allows short messaging service (SMS) capable mobile handsets to communicate with a telecommunication device (TD). The method and apparatus may be implemented into a mobile network/public switched telephone network (PSTN) as a stand-alone gateway interface without the need to reconfigure or modify the network hardware. A user of an SMS-capable mobile handset may send text messages to a user of a TD device or receive text messages sent by the user of a TD device. The method provides an interface function that allows a deaf person having access to a TD device to communicate with mobile handset users. It also allows a mobile handset user to send communications to a deaf person using a TD device. 
     The method and apparatus utilizes a gateway interface between the public switched telephone system (PSTN) and cellular network. The gateway interface provides a conversion function between the SMS text messaging protocol and TD device text messaging protocol. The conversion function includes appropriate queuing and timing features that allow the SMS and TD functions to communicate. 
     In an embodiment of the invention, the method and apparatus is implemented as a stand-alone gateway. The gateway may be implemented anywhere there is access to the public switched telephone network (PSTN) and coverage by a cellular system having short messaging service (SMS) capability. The gateway includes a controller and a transceiver. The controller may be implemented in a personal or similar type of computer. The transceiver operates according to the standard of a cellular system, including the system&#39;s SMS features covering the area in which the transmitter is located. The transceiver is assigned a mobile network phone number and is capable of making and receiving calls under the control of the controller. The transceiver may be a conventional cellular handset connected to the controller through, for example, a bus such as an RS-232, or the transceiver may be a specially constructed transceiver built into the controller. The controller may be connected to the PSTN through a TD modem. The controller is assigned a PSTN phone number and communicates with TD devices that are connected to the PSTN using a TDD protocol. Connections may be provided through the Internet to allow multiple gateways to communicate with one another. The Internet connections allow multiple gateways to bypass the PSTN when communicating. 
     In order to initiate TD to mobile station communications, the user of a TD device dials the PSTN phone number that is assigned to the gateway. When a connection is made, the gateway then sends the appropriate responses in TDD protocol to prompt the user of the TD to enter the phone number of the mobile station(s) that are to receive a message. As the message is entered at the TD, the gateway buffers and converts the message to an appropriate format for SMS, according to the embodiment. By entering the message and following the prompts, the user is able to have the message sent to a destination mobile through the gateway. 
     In order to initiate mobile station to TD communications, the user of a mobile station sends a message via SMS to the mobile network phone number of the gateway transceiver. The message includes a phone number for each TD device that is to receive the message. Messages received by the gateway that are intended for a TD are placed in a queue within the gateway. The gateway processes the messages in the queue by dialing the phone number(s) of the message that has been in the queue the longest time. For each TD phone number that is busy, the gateway will retry dialing for a predetermined period of time. If the TD phone number is busy, the gateway will send an SMS message informing the mobile station that the TD is busy, but that the gateway will retry for the predetermined period of time. If the TD answers, the gateway performs appropriate functions so that the message sent to the TD meets TTD protocol requirements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a telecommunication system including a TD/SMS gateway according to an embodiment of the invention; 
     FIGS. 2A and 2B are flow diagrams showing steps performed while processing a TD to mobile station message according to an embodiment of the invention; and 
     FIGS. 3A,  3 B and  3 C are flow diagrams showing steps performed while processing a mobile station to TD message according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, therein is illustrated a telecommunication network including a TD/SMS gateway according to an embodiment of the invention. Network  100  includes a public switched telephone network (PSTN)  114 , cellular network  118 , cellular network  116 , gateway  102 , gateway  104 , remote computer  128 , telecommunication device (TD)  124  and TD  126 . In the embodiment, cellular networks  118  and  116  operate according to the Global System for Mobile (GSM) cellular standard. TDs  124  and  126  operate according to the Electronic Industry Association&#39;s (EIA) “Telecommunications Devices for the Deaf” PN-1663 Standard (PN-1663). 
     PSTN  114  may be a conventional public landline phone system. Each of TD  124 , TD  126 , gateway  102 , gateway  104  and remote computer  128  is assigned a phone number of PSTN  114  and is connected to PSTN  114  through appropriate communication interfaces. Gateway  102  comprises gateway controller  106  and mobile station (MS)  108 . Gateway  104  comprises gateway controller  110  and mobile station (MS)  112 . In the embodiment, MS  108  and MS  112  function as the transceiver in each of gateways  102  and  104 , respectively. MS  108  and MS  112  are each assigned a mobile phone number in cellular network  118  and cellular network  116 , respectively. Cellular network  118  and cellular network  116  each may comprise at least one cellular network and may also include a portion of a PSTN, such as PSTN  114 , as necessary for communicating phone calls between MS  120  and MS  108 , and MS  122  and MS  112 . 
     The embodiment of FIG. 1 is designed so that gateway  102  or gateway  104  may be installed without modifying equipment in network  100 . MS  108  and MS  112  may be conventional handsets or mobile communicator type devices with SMS text messaging protocol capability, connected to gateway controllers  106  and  110 , respectively, through an RS-272 bus, USB bus or other connection, for example, a handset manufacturer-specific bus. In alternative embodiments, MS  108  and MS  112  may be replaced with transceivers built into gateway controllers  106  and  110 , respectively. Gateway controllers  106  and  110  are capable of handling text messages according to either SMS text messaging protocol or the PN-1663 text messaging protocol of TDs  124  and  126  and may be implemented in a PC computer or a specially designed hardware/software apparatus. For multiple gateways, such as gateways  102  and  104 , Internet  130  may provide communication between the multiple gateways. This may provide an advantage, for example, in communication between MS  122  and TD  124  or  126  when cellular network  116  is remotely located, with no connection to PSTN  114 , and Internet connection  130  is by satellite or wireless. It may also avoid expensive phone call charges for communication between MS  122  and TD  124  or TD  126  if it would be necessary for gateway  104  to incur long-distance charges to communicate with PSTN  114  through another PSTN. 
     Gateway controllers  106  and  110  are configured with appropriate hardware/software to perform the TD/SMS interface function according to the invention. In order to install the embodiment of FIG. 1, an operator procures a PSTN phone number for each of gateway controllers  106  and  110  and a cellular phone number for each of MS  108  and  112 . Gateway controllers  106  and  110  are each connected to PSTN  114  by a standard modem for communication with remote computer  128  and a TD modem for communication with TD  124  and TD  126 . Gateways  102  and  104  may be implemented independent of, and without modifying, PSTN  114  and cellular networks  116  and  118 . 
     Referring now to FIGS. 2A and 2B, therein are flow diagrams showing steps performed while processing a TD to mobile station message according to an embodiment of the invention. The process steps of FIGS. 2A and 2B are performed by the various components of network  100  of FIG.  1 . The functions may be implemented into the components of network  100  using appropriate hardware and/or software. An illustrative example using communication between MS  120  and TD  124  through gateway  102  will be shown. 
     The process begins at step  200 . At step  202 , the user of TD  124  dials the PSTN phone number of gateway  102 . Next, at step  204 , gateway controller  106  answers and sends a prompt message to TD  124 . A TD connection, according to TDD protocol, is now set up between gateway controller  106  and TD  124 . The prompt message may include a welcome message, for example, “Welcome to the TD/SMS gateway,” and a request message, for example, “Please enter the phone number of the destination, then press return.” At step  206 , the user of the TD responds by entering the number of the mobile station, in this example MS  120 , that is to receive the message. The number may be entered in the same manner as numbers are entered when using the PSTN or using a delineation, such as a dash or space character, to enter the number in one of the following formats: 1-xxx-xxx-xxxx, xxx-xxx-xxxx, or xxx-xxxx, where x is a digit from 0 to 9. 
     Next, at step  208 , gateway  102  processes the number. If the entered number was not entered in a valid format, gateway  102  will send out a text message to TD  124 , such as, “The phone number xxx-xxx is not a valid number. Please re-enter the number.” Steps  206  and  208  may be repeated until the TD user enters a valid phone number in place of the invalid number or hangs up. In alternative embodiments, multiple numbers may be entered as the destination of a message. 
     At step  210 , gateway  102  responds with a prompt message, for example, “Please enter the message text, then press return to send.” Next, at step  212 , the TD user enters the message text. At step  212 , the process moves to FIG.  2 B. At step  230  of FIG. 2B, character entry begins. Next, at step  232 , gateway controller  106  buffers each character as it is entered. Next, at step  234 , it is determined whether or not a text character has been entered. If a text character was entered, the process returns to step  230 . At step  232 , gateway controller  106  receives and buffers the next input character. If, however, at step  234  it is determined that a text character has not been received, the process moves to step  236 . At step  236 , it is determined whether or not a backspace character has been received. If a backspace character has been received, the process moves to step  238 . At step  238 , gateway controller  106  deletes the last entered character. The process then moves to step  232  where gateway controller  106  receives and buffers the next input character. If, however, at step  236  it is determined that a backspace character is not received, the process moves to step  240 . 
     At step  240 , it is determined whether or not an esc character has been entered. If an esc character has been entered, the process moves to step  248 . At step  248 , gateway controller  106  sends a prompt to TD  124 . The prompt may read, for example, “Continue with this message? Y/N.” Next, at step  250 , it is determined if a “Y” character was received in response to the prompt sent in step  248 . If a “Y” character was not entered, the process moves to step  252 . At step  252 , gateway controller  106  dumps the buffer. From step  252  the process returns to step  204  of FIG.  2 A. If, however, at step  250  it is determined a “Y” character has been received, the process returns to step  232 , where gateway controller  106  receives and buffers the next input character. If, however, at step  240  it is determined that an esc character has been received, the process moves to step  242 . At step  242 , it is determined that a return character has been received, since in the embodiment all characters other than backspace, esc and return are considered text. At step  244 , gateway controller  106  divides the buffer into messages of  160  characters, with additional concatenation characters inserted as necessary. The process then moves to step  214  of FIG.  2 A. 
     At step  214 , gateway controller  106  sends the formatted message(s) through the SMS function of MS  108  over cellular network  118  to MS  120 . At step  216 , gateway controller  106  will send a receipt indication to TD  124 , if the SMS function of cellular network  118  sends an SMS delivery receipt to gateway  102 . 
     Referring now to FIGS. 3A and 3B, therein are flow diagrams showing steps performed while processing a mobile station to TD message according to an embodiment of the invention. The process steps of FIGS. 3A and 3B are performed by the various components of network  100  of FIG.  1 . The functions may be implemented within the system using appropriate hardware and/or software. 
     The process begins at step  300 . At step  302 , the user of MS  120  enters an SMS message at MS  120 . The SMS message includes the phone number of the TD device that is to receive the message as a prefix. Next, at step  304 , the SMS message is sent through the SMS function of cellular network  118  to MS  108 , and the SMS message is transferred to gateway controller  106 . Next, at step  306 , the message is placed in the TD message queue of gateway controller  106 . At step  308 , a timer associated with the received message is initialized to run a predetermined period of time and the timer value is placed in the queue. The TD message queue for the received SMS message includes the message text, the phone number of the sending mobile station, MS  108 , the time of arrival of the message, and the value of the timer. In alternative embodiments, multiple destination phone numbers could prefix a message and a separate queue entry could be created for each destination TD. 
     Next, at step  310 , it is determined whether or not the prefix of the message includes a valid phone number. If it is determined that there is not a valid phone number in the prefix, the process moves to step  312 . At step  312 , the message is deleted from the queue. Next, at step  314 , gateway  102  sends an SMS message to MS  120  indicating the message was not sent, such as, for example, “The message-[sample text from message]-was not sent due to an invalid number.” The process then moves to step  318  and ends. If however, at step  310 , it is determined that the prefix of the message includes a valid phone number, the process moves to step  316 . At step  316 , gateway controller  106  processes the messages in the queue. The queue is processed according to the process steps shown in FIG.  3 B. 
     The process of FIG. 3B begins at step  324 . At step  326 , gateway controller  106  dials the number of the destination TD of the first (next) message in the queue. In the embodiment, the messages are processed in the order received at gateway  102 . Next, at step  328 , it is determined whether or not the dialed number is busy. If the number is not busy, the process moves to step  336 . At step  336 , gateway controller  106  sends the message to the recipient TD using the TDD protocol. Gateway  102  inserts a carriage return and a line feed after every  72  characters to meet TD backward capability specifications. Next, at step  338 , gateway  102  sends a return receipt SMS to MS  120 , if required by the mobile station user. The process then moves to step  340 . If, however, at step  328 , it is determined that the dialed number is busy, the process moves to step  330 . At step  330 , gateway  102  sends an SMS message to MS  120  indicating that the destination TD is not available, such as, for example, “The message-[sample text from message]-was not sent due to a busy signal. The system will retry for one hour.” Next, at step  332 , it is determined whether or not the timer associated with the message has expired. If the timer has not expired, the message and its associated information are moved to the bottom of the queue. The process then moves to step  340 . If, however, at step  332 , it is determined that the timer has expired, the process moves to step  350 . At step  350 , the message is deleted from the queue. The process then moves to step  340 . 
     At step  340 , it is determined whether or not every message in the gateway queue has been processed for the latest entrance into the process of FIG. 3B from step  324 . If the complete queue has not been processed, the process returns to step  326  and the next message in the queue is processed. If, however, at step  340  it is determined that the complete queue has been processed, the process of FIG. 3B moves to step  342  and ends. 
     In the embodiment, the queue is processed every time a new SMS-to-TD message is received to be sent to a TD device. The queue may be also periodically processed, for example, every x minutes. Referring now to FIG. 3C, therein is a flow diagram showing process steps performed when the mobile station to TD message queue is periodically processed according to an embodiment of the invention. The process begins at step  344  when a queue processing timer is triggered. At step  346 , it is determined whether or not the queue is empty. If it is determined that the queue is empty, the process moves to step  348  and ends. If, however, at step  346  it is determined that the queue is not empty, the process moves to step  352 . At step  352 , gateway  102  processes the messages in the queue. The queue is processed according to the process steps of FIG.  3 B. 
     Although described in the context of particular embodiments, it will be realized that a number of modifications to these teachings will be apparent to one skilled in the art. Thus, while the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and scope may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.