Abstract:
A system and method for initiating a dial-up connection between a remote computing device and a network over an infrared link between the remote computer and an infrared modem is disclosed. A unique protocol defines the universe of commands, responses, and behavior of the modem regarding initialization, response sequence, and switching between data transfer mode and AT command mode.

Description:
RELATED APPLICATION 
     This application is related to, and claims priority from, U.S. Provisional Application Serial No. 60/110,507, entitled “IR NET Dial”, filed on Dec. 1, 1998, the disclosure of which is expressly incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to electronic communication and more particularly to electronic communication over an infrared link, and even more particularly to a system and method for establishing a dial-up connection between a remote computing device and a network over an infrared communication link between a modem with infrared communications interface (Ir modem) and the remote computing device. 
     The rapid proliferation of digital computing equipment coupled with users&#39; desires to transmit data between computing devices has resulted in the rapid expansion of digital communication networks. The most visible example of this phenomenon is the internet. The growth in wireless communication, particularly in mobile phones, has made it desirable to enable mobile phones to exchange data with computing devices like personal computers. One solution to this problem has been to provide mobile phones with an Ir modem to enable the mobile phone to establish an infrared data link with a computing or communication device like a personal computer. Using an Ir modem, a mobile phone can provide wireless data transfer between a remote computing device like a personal computer and host computing device like a server connected to a conventional wireline network. 
     Infrared communication links are known in the art. An infrared data link transmits information using pulses of infrared light as the carrier signal. The Infrared Data Association (IrDA), an industry association, promulgated a proposed standard for establishing infrared communication links between electronic communication devices, generally referred to as the IrDA protocol. The IrDA protocol provides a multi-layered protocol stack governing communication between electronic devices over an infrared data link. The IrDA protocol stack is depicted in FIG.  1 . 
     Physical layer  10  includes the hardware constituting the optical transceiver and specifies optical characteristics of the infrared signal. Physical layer  10  also manages the interface between components of the system implemented in hardware and the upper layer protocol layers, typically implemented in software. To do this, physical layer  10  also manages encoding of data, and framing for various communication speeds. 
     Ir Link Access Protocol (IrLAP)  20  corresponds to data link layer (layer 2) of the Open Systems Interconnection (OSI) protocol. IrLAP  20  is responsible for initiating and maintaining an infrared connection between two devices. Two devices connected by an IrLAP connection exist in a master-slave, or primary-secondary relationship. The primary device is responsible for all aspects of managing the connection. The primary device sends command frames to initiate a connection, to transmit data, and to terminate a connection. The secondary device sends response frames. The primary device is also responsible for controlling data flow and resolving data link errors. Once a connection is established, the IRLAP service implements retransmission, error correction and low-level flow control procedures to provide a reliable data transfer service between two connected devices. 
     The Ir Link Management Protocol (IrLMP)  30  service utilizes the reliable connection provided by the IRLAP layer  20  and adds multiplexing services to allow multiple IrLMP clients to transmit data across a single IrLAP link. To implement multiplexing, IrLMP  30  implements a higher level addressing scheme in which the Logical Service Access Point (LSAP) defines the point of access to a service or application. The LSAP is identified by a one byte number referred to as a LSAP Selector (LSAP-SEL). Using this higher level addressing scheme, multiple IrLMP services or applications may be multiplexed over a single IrLAP connection. 
     The Tiny Transport Protocol (TinyTP)  40  is a transport layer service that provides flow control for each IrLMP connection and also performs segmentation and reassembly (SAR). Flow control is provided using a credit-based flow control scheme in which the devices transmit credit packets indicating how many IrLMP packets they can receive. 
     The IrDA protocol provides three optional services: Ir Object Exchange (IrOBEX)  60 , Ir Local Area Network (IrLAN)  50  and Ir Serial and Parallel Port Emulation (IrCOMM)  70 . IrOBEX  60  is an application layer protocol that provides a simple, compact data exchange service. IrLAN  50  is an application layer protocol that emulates a LAN connection. Finally, IrCOMM  70  is an application layer protocol that emulates communication over a parallel or serial communication port. 
     An Ir modem requires two additional layers residing logically above the IrCOMM layer  70  to communicate with a remote computing device (e.g., a personal computer (PC) or personal digital assistant (PDA)): the AT Parser layer  90  and the Data Transfer layer  95 . The AT Parser  90  accepts commands from applications running on the remote computing device. The commands are executed and a final response is sent back, optionally preceded by one or more intermediate responses. It will be noted that in normal operation, an application running on the remote computing device generates a single AT command and waits for a response. The AT Parser  90  may also generate unsolicited responses that are sent to the application at any time during execution of commands, but more likely during the execution of two AT commands, or when the application is idle. Unsolicited commands may be used by the modem to get the attention of the application when an incoming call has been detected. 
     AT commands are a generic method of commanding a modem and receiving responses. Standardized AT commands are detailed in International Telecommunications Union Standard ITU-T V.25 ter. In addition to standardized commands, each manufacturer can establish proprietary commands. The application must therefore know the type of modem with which it is communicating so it can issue the correct commands to configure the modem. By way of example, the Microsoft® Windows® operating system has hundreds of modem descriptions, each with their own set of commands that are needed to make sure the modem operates properly. 
     The Data Transfer layer  95  is active when a call is connected and performs the transport of the data to and from the remote modem. When the Data Transfer layer  95  is active, the AT parser  90  is inactive. The transition from the AT parser  90  mode to the Data Transfer layer  95  mode (e.g., data mode) is made after either the ATD or ATA commands have completed execution and the call is connected. Transition from data mode back to AT parser mode is required before the modem can be commanded to disconnect the call. For this, one of several industry standards can be implemented by the modem manufacturers. The transition can be initiated either by in-band signalling or out-of-band signalling using the V.24 pin DTR. In-band signalling is called the “escape sequence” and consists of a pattern of characters. 
     The escape sequence usually consists of three plus characters in sequence (“+++”), sometimes with a required delay either before or after the sequence, or both. The escape character is configurable using an AT command. Some escape sequences must be followed by a valid AT command before it is accepted by the modem. When the transition is made, the modem sends the final result code “OK” to the application. 
     The IrCOMM entity is, in some implementations, exposed to the applications as a COMM-port, so the application does not require special support for IrDA to operate with, for example, an IR modem. This is called a “Virtual COMM-port”. When the application connects to this virtual COMM-port, most known IR stack implementations lock the entire IR stack. This means that other applications and protocols like OBEX over IR cannot be operative while IrCOMM is used. 
     Finally, the IrDA Information Access Service (IAS)  80  acts as the “yellow pages” for a device. The IAS uses a client-server model in which client objects make requests about the services available on a particular device, and the server accesses an information base of objects supplied by local services or applications to respond to the request. An IAS object is represented by a data structure having a Class Name and up to 256 Named Attributes. 
     Presently, IrDA-compatible infrared communication links between an Ir modem and computing devices are established using the IrCOMM application layer service. IrCOMM includes a control channel that can be used to separate control signaling from data transfer. However, because IrCOMM was designed to emulate a serial or parallel communication port, it is poorly adapted for establishing connections between mobile phones and computing devices. For example, IrCOMM lacks a feature for initializing an Ir modem to start a communication session. In the absence of an initialization feature, this function must be addressed by higher level application software. Accordingly, there is a need in the art for a compact, yet robust system and method for establishing an infrared connection between an Ir modem and a remote communication device. 
     SUMMARY OF THE INVENTION 
     The present invention addresses these and other concerns by providing an alternate service for providing a connection between a computing device and an IR modem over an infrared communication link. The service is referred to herein as the IrNetDial protocol, or service. The IrNetDial service may be added to the IrDA protocol stack in conjunction with IrLAN, OBEX, and IrCOMM and is exposed to the application through the IAS. IrNetDial defines the initial state of the modem, thereby removing the need for initialization, and provides a strictly limited set of supported AT commands and responses. Further, IrNetDial provides a defined method for switching from data mode to AT parser mode. These features simplify the application that sets up the data connection, improve reliability, and remove the need for a description of the specific modem listing the AT commands valid for the modem in use. IrNetDial encourages ad-hoc networking since the modem configuration does not have to be installed from a removable media; instead, the Ir Modem with IrNetDial can be used at once. 
     The present invention addresses these and other needs by providing, in one aspect, a method of initiating, in a remote computing device, a request to establish a dial-up connection with a network over an infrared communication link between the remote communication device and an Ir modem. The method comprises the steps of querying the LMP_IAS to obtain the LSAP-SEL for the infrared communication link, establishing a logical connection to an IrDA TinyTP LSAP returned by the LMP_IAS query, and executing an ATD command to initiate a dial-up connection between the remote computing device and the network over the infrared link between the remote computing device and the Ir modem. 
     In another embodiment, the invention provides a method of receiving, in a remote computing device, a request to establish a dial-up connection with a network over an Ir communication link between the remote computing device and an Ir modem. The invention comprises the steps of querying an IrDA LMP_IAS to obtain the LSAP-SEL for the infrared connection, establishing a logical connection to an IrDA TinyTP LSAP returned by the LMP_IAS query, and executing an ATA command to answer the request for a dial-up connection between the remote computing device and the network over the infrared link between the remote computing device and the Ir modem. 
     In further embodiments of the invention, an initiation string is transmitted to the Ir modem. 
     In further embodiments of the invention, data is transmitting between the remote computing device and the Ir modem. 
     In further embodiments of the invention, the communication session is terminated by transmitting an ATH command to the Ir modem. 
     In another aspect, the invention provides a system for establishing a dial-up connection between a remote computing device and network over an infrared communication link between the remote computing device and an infrared modem. The system comprises means for querying a LMP_IAS to obtain a LSAP-SEL for the infrared connection, means for establishing a logical connection to an IrDA TinyTP LSAP returned by the LMP_IAS query, and means for executing an ATA command to initiate a dial-up connection between the remote computing device and the network over the infrared link between the remote computing device and the Ir modem. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These, and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art upon reading the following detailed description, in conjunction with the appended drawings, in which: 
     FIG. 1 is a schematic depiction of the IrDA protocol stack. 
     FIG. 2 is a schematic depiction of a communication system according to the present invention. 
     FIG. 3 is a schematic depiction of a protocol stack according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a system and method for establishing an infrared communication link between an Ir modem and a communication or computing device. In a preferred embodiment, the present invention provides the ability to set up and facilitate a wireless dial-up connection between a remote computing device and a network. Data is transferred over an infrared link between the remote computing device and the Ir modem. 
     1. Network Architecture 
     FIG. 2 presents a network architecture for dial-up networking implemented according to one embodiment of the present invention. Referring to FIG. 2, there is illustrated a remote computing device  110  connected to an Ir modem  120  by infrared communication link  115 . Ir modem  120  is connected to a mobile telephone  130  which establishes a wireless link  135  to a mobile communication network  140 . A base station  150  receives wireless signals from mobile communication network  140  and transmits the signals across a wireline link  160  through a wireline network  170 , to host computing devices  180   a  and/or  180   b.  A network architecture according to FIG. 2 allows a user of remote computing device  110  to use mobile communication network  140  to establish a data connection with more traditional wireline computer networks or network devices. 
     In one embodiment, remote computing device  110  may be embodied in a personal computer having an infrared communication port. Infrared communication ports are standard interfaces on many portable personal computers. By way of example, the Dell® Inspiron® line of portable personal computers, commercially available from Dell Computer Corporation, Round Rock, Tex., USA includes an IrDA 1.1 compatible serial infrared communication port. It will be appreciated that remote computing device  110  may be embodied as any computing device having an infrared communication port including, but not limited to, personal computers and personal digital assistants. 
     In one embodiment Ir modem  120  may be integrated into mobile phone  130 . An exemplary mobile phone including an integrated Ir modem is the Ericsson® model CF-888 commercially available from Ericsson. Preferably, Ir modem  120  is IrDA compliant. It will be appreciated that Ir modem  120  could be separate from mobile phone  130 . According to the invention, Ir modem  120  can operate in two different modes: an offline command mode and an online data mode. Communication sessions are started with Ir modem  120  in an offline command mode, in which there is no call established over mobile phone  130  and Ir modem  120  is waiting for instructions. When a communication session is established and a call is connected, Ir modem  120  switches to an online data mode in which the modem can transmit and receive data. In the online data mode, the only control instruction Ir modem  120  can act upon is an instruction that terminates the connection, as discussed below. 
     2. Data Architecture 
     The present invention is particularly concerned with establishing a dial-up connection over the infrared communication link  115  between remote computing device  110  and Ir modem  120 . As depicted in FIG. 2, infrared modem  120  is preferably integrated with or connected to mobile telephone  130  to enable remote computing device  110  to establish a wireless network connection. 
     FIG. 3 presents a schematic depiction of the protocol stacks that govern data transmission over infrared communication link  115  according to the present invention. The present invention provides a compact, robust procedure for establishing and maintaining a data connection over infrared communication link  115  using an IrDA TinyTP connection. To accomplish this, the present invention provides a service, referred to herein as IrNetDial, for establishing a data connection between a remote computing device and an infrared modem. Referring to FIG. 3, IrNetDial  350  is an optional IrDA protocol that uses the services of the lower-layer protocols (e.g., TinyTP  340 , IrLMP  330 , IrLAP  320 , Physical Layer  310 ), which are preferably IrDA compliant. 
     According to the present invention, user applications  370  (e.g., e-mail, file transfer applications, etc.) on remote computing device  110  pass data to the IrNetDial  350  service through an application programming interface (API)  360 . The IrNetDial service manages the process of setting up the dial-up connection, initializing the modem, if necessary, and terminating the dial-up connection when the session is finished. Advantageously, IrNetDial manages the connection process using a limited subset of commands from the ITU-T Rec. V.25 ter (July 1997) SERIAL ASYNCHRONOUS AUTOMATIC DIALING AND CONTROL, which is incorporated by reference herein. 
     3. V.25 ter Command Options 
     In a preferred embodiment, the present invention implements a limited subset of the V.25ter AT commands. These commands are transmitted in TinyTP frames. Pursuant to the V.25ter standard, the Ir modem echoes the command back to the host communication device and provides one or more responses to the AT command. Multiple commands may be transmitted in a single TinyTP frame, but a single command may not be split between TinyTP frames. By contrast, echoes and responses may be split between TinyTP frames. 
     The present invention follows the rules set forth in the V.25ter standard for separating AT commands. All AT commands are terminated with a &lt;CR&gt;. The echoed command also terminates with a &lt;CR&gt;. Responses from the Ir modem are of the form &lt;CR&gt;&lt;LF&gt;Response&lt;CR&gt;&lt;LF&gt;. Thus, each AT command issued results in the following transmission sequence between the host communication device and the Ir modem. It will be noted that one or more response codes may be returned in response to every command. In the following exemplary command sequence, it will be noted that &lt;CR&gt;is, by default, the character with the decimal number 13 and &lt;LF&gt; is the character with the decimal number 10. 
     
       
         
               
             
               
               
               
               
             
               
               
             
               
               
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Exemplary Command Sequence 
               
             
          
           
               
                   
                 Direction 
                 Content 
                 Format  
               
               
                   
                   
               
               
                   
                 PC→Modem 
                 Command 
                 AT . . . &lt;CR&gt; 
               
               
                   
                 PC←Modem 
                 Echo 
                 AT . . . &lt;CR&gt; 
               
               
                   
                 PC←Modem 
                 Response 
               
             
          
           
               
                   
                 &lt;CR&gt;&lt;LF&gt;Response&lt;CR&gt;&lt;LF&gt; 
               
             
          
           
               
                   
                 PC←Modem 
                 Response (possible) 
               
             
          
           
               
                   
                 &lt;CR&gt;&lt;LF&gt;Response&lt;CR&gt;&lt;LF&gt;  
               
               
                   
                   
               
             
          
         
       
     
     The present invention implements the following commands for the V.25ter protocol. The commands are presented as a character string, followed by a verbal description of the command. 
     
       
         
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Comments  
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 a. Link Control Commands 
               
               
                 ATD, Dial 
               
               
                 Description: 
               
               
                 Initiate a data call. The phone number used to establish the connection will 
               
               
                 consist of digits and modifiers or a stored number specification. An 
               
               
                 abortion of the operation can be made by sending any character during 
               
               
                 ATD connection before CONNECT is received. 
               
             
          
           
               
                 Execute command: 
                 D&lt;n&gt; 
                 Dial the phone number 
               
               
                   
                   
                 specified in the command as 
               
               
                   
                   
                 &lt;n&gt;. 
               
               
                 Dial examples: 
                 ATD+4646120345 
                 See below for possible 
               
               
                   
                   
                 responses. 
               
               
                 Response codes: 
                 CONNECT&lt;speed&gt; 
                 Data connection established at 
               
               
                   
                   
                 the rate given in &lt;speed&gt;. 
               
               
                   
                   
                 This puts the modem into 
               
               
                   
                   
                 Online Data Mode. 
               
               
                   
                 NO CARRIER 
                 Unable to establish a 
               
               
                   
                   
                 connection or the connection 
               
               
                   
                   
                 attempt was aborted. The 
               
               
                   
                   
                 modem remains in Offline 
               
               
                   
                   
                 Command Mode. 
               
               
                   
                 ERROR 
                 An unexpected error occurred 
               
               
                   
                   
                 while trying to establish the 
               
               
                   
                   
                 connection. The modem 
               
               
                   
                   
                 remains in Offline Command 
               
               
                   
                   
                 Mode. 
               
               
                   
                 NO DIALTONE 
                 The mobile phone is being 
               
               
                   
                   
                 used for a voice call or 
               
               
                   
                   
                 is not within coverage 
               
               
                   
                   
                 of the network. The 
               
               
                   
                   
                 modem remains in Offline 
               
               
                   
                   
                 Command Mode. 
               
               
                   
                 BUSY 
                 The called phone number is 
               
               
                   
                   
                 engaged. The modem remains 
               
               
                   
                   
                 in Offline Command Mode. 
               
             
          
           
               
                 ATH, Hook control 
               
               
                 Description: 
               
               
                 Terminates a connection. 
               
             
          
           
               
                 Execute command: 
                 H 
                   
               
               
                 Response code: 
                 NO CARRIER 
                 Connection terminated. 
               
               
                   
                   
                 Modem goes from Online 
               
               
                   
                   
                 Command Mode to Offline 
               
               
                   
                   
                 Command Mode. 
               
               
                   
                 OK 
                 This is returned if already in 
               
               
                   
                   
                 Offline Command Mode. 
               
               
                   
                 ERROR 
                 Unexpected error. 
               
               
                 ATA, Answer 
               
               
                 Description: 
               
             
          
           
               
                 Answers an incoming data call. To Receive an incoming data call the 
               
               
                 modem has to be IrDA connected and in offline command mode. If there 
               
               
                 is an incoming call the modem will send an unsolicited result code in 
               
               
                 the form &lt;CR&gt;&lt;LF&gt;RING&lt;CR&gt;&lt;LF&gt;. It is 
               
               
                 then possible to answer by using ATA. 
               
             
          
           
               
                 Execute command: 
                 A 
                 Answers and initiates 
               
               
                   
                   
                 connection to an incoming 
               
               
                   
                   
                 call. 
               
               
                 Examples: 
                 ATA 
               
               
                 Response code: 
                 CONNECT&lt;speed&gt; 
                 Data connection established at 
               
               
                   
                   
                 the rate given in &lt;speed&gt;. 
               
               
                   
                 ERROR 
                 This is returned if not a data 
               
               
                   
                   
                 call, or if no call at all. 
               
             
          
           
               
                 b. Initiation Commands 
               
               
                 AT+DS Data Compression Mode 
               
               
                 Description: 
               
               
                 Defines the compression parameters and negotiation used for V.42 bis 
               
               
                 compression specified in ITU-T Recommendation, Data Compression 
               
               
                 Procedures for Data Circuit Terminating Equipment (DCE) 
               
               
                 Using Error Correction Procedures. 
               
               
                 Set command: +DS=[&lt;dir&gt;,[&lt;neg&gt;,[&lt;md&gt;,[&lt;ms&gt;]]]] 
               
             
          
           
               
                   
                 &lt;dir&gt; 
                 0 
                 Disable V.42bis compression 
               
               
                   
                   
                 1 
                 Enable V.42bis compression on 
               
               
                   
                   
                   
                 transmitted data 
               
               
                   
                   
                 2 
                 Enable V.42bis compression 
               
               
                   
                   
                   
                 on received data 
               
               
                   
                   
                 3 
                 Enable V.42bis compression on 
               
               
                   
                   
                   
                 received and transmitted data. 
               
               
                   
                   
                   
                 Default = 3. 
               
               
                   
                 &lt;neg&gt; 
                 0 
                 Connect even if the compression 
               
               
                   
                   
                   
                 protocol does not comply with 
               
               
                   
                   
                   
                 that specified by dir. 
               
               
                   
                   
                 1 
                 Disconnect if compression protocol 
               
               
                   
                   
                   
                 does not comply with dir. 
               
               
                   
                   
                   
                 Default = 0. 
               
               
                   
                 &lt;md&gt; 
                 512-4096 
                 Defines the maximum dictionary 
               
               
                   
                   
                   
                 size. This value will be amended 
               
               
                   
                   
                   
                 automatically to comply with any 
               
               
                   
                   
                   
                 memory constraints. 
               
               
                   
                   
                   
                 Default = 2048 bytes. 
               
               
                   
                 &lt;ms&gt; 
                 6,250 
                 Defines the maximum string 
               
               
                   
                   
                   
                 length. Default = 32 bytes.  
               
               
                   
                   
               
             
          
         
       
     
     4. Initiation String and Default Settings 
     The Ir modem must be initialized before opening a communication session. A modem manufacturer may specify a default initiation setting. An exemplary default setting of an IrModem may be specified in accordance with ITU-T Recommendation V.25, ter, as follows. 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 Echo 
                 ON, EI 
               
               
                 Results 
                 Verbose, V1 
               
               
                 Result code suppression 
                 OFF, QØ 
               
               
                 Esc. Character 
                 =“+”, S2=43, 
               
               
                 Enter (CR) 
                 =dec. symbol # 13, S3=13 
               
               
                 Linefeed (LF) 
                 =dec. symbol # 10, S4=10 
               
               
                 V.42bis compression 
                 Enabled on received and transmitted data, 
               
               
                   
                 always negotiate, max dictionary size 
               
               
                   
                 2048, string length 32.  
               
               
                   
               
             
          
         
       
     
     Provided the user is willing to accept the default settings, no special initialization instruction by the PC are necessary when opening an IrNETDial connection. The IrModem preferably includes means for initializing itself when an infrared connection is opened. Such means may be embodied as logic instructions operating on a suitable microprocessor. However, the remote computing device may turn compression on and off. 
     To enable future expanded capabilities in the modem, each modem vendor can provide an initiation string for use with its modem. The initiation string contains AT commands configuring the modem in a desired way for dial-up networking. The PC must, before dial-up, send the initiation string to the modem. This string could be automatically stored in a memory location associated with the PC when the modem is installed. By using the phone Plug n&#39;Play number read by IrDA_IAS request, a control that the right modem is installed can be made. It may also be displayed in the modem configuration menu so it can be edited manually. In a preferred embodiment, the string format is as follows: 
     Each command in the string should be written using only the set command itself (i.e., without the characters AT in format). 
     The character &lt;CR&gt; shall NOT be included after each command. 
     Each command shall be separated by a semicolon (;). 
     EXAMPLE 
     Ir Modem Initiation String 
     
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 +XTRA=1,5;+NEW=3  
               
               
                   
                   
               
             
          
         
       
     
     5. Operation 
     A dial-up connection may be established over the infrared link between the remote computing device and the Ir modem pursuant to the following procedures: referring to FIG. 2, when remote computing device  110  initiates an outgoing call, a processor in the remote computing device  110  queries the IrDA LMP-IAS to obtain the LSAP-SEL for the connection and establishes a logical connection to the IrDA Tiny TP LSAP-SEL returned by the IAS query. Ir modem  120  is initialized for dial-up services. Ir modem  120  may be self-initialized or an initiation string may be transmitted with extra setting, if existing, from remote computing device  110  to the Ir modem  120 . Remote computing device  110  establishes a dial-up connection by transmitting an ATD command with the desired destination phone number. When destination device (e.g.  180   a,    180   b ) answers, remote computing device  110  and Ir modem  120  exchange data pursuant to existing IrDA procedures, and the data may be transmitted to destination device  180   a,    180   b.  Remote computing device  120  may end the telecommunication session by sending an escape sequence (e.g., +++) and an ATH command. The IR communication session may then be disconnected. 
     A slightly modified process applies when remote computing device  110  receives an incoming call through Ir modem  120 . In this case, an application on remote computing device  110  typically initiates the infrared link between remote computing device  110  and Ir modem  120  and waits for an incoming call, which is indicated by the IR modem sending the unsolicited code “RING” to the application. The infrared connection is then established in substantially the same manner. Remote computing device  110  queries the LMP-IAS 380 to obtain the LSAP-SEL for the connection and establishes a logical connection to the IrDA Tiny TP LSAP-SEL returned by the IAS query. Ir modem  120  is initialized for dial-up services. Ir modem  120  is self-initialized, but an initiation string may be transmitted with extra settings, if existing, from remote computer  110 . When Ir modem  120  receives an incoming call, Ir modem  120  transmits a ring indication in the form of an unsolicited result code in the following format: &lt;CR&gt;&lt;LF&gt;RING&lt;CR&gt;&lt;LF&gt;. Remote computing device  110  answers the call using the ATA command. Data may then be exchanged pursuant to existing IrDA procedures. Remote computing device  110  may end the telecommunication session by sending an escape sequence (e.g. +++) and an ATH command. The IR communication session may then be disconnected. 
     It will be noted that if the call is terminated for some reason, Ir modem  120  sends an unsolicited response &lt;CR&gt;&lt;LF&gt;NO CARRIER&lt;CR&gt;&lt;LF&gt;. Similarly, if the infrared connection for some reason is obstructed or interrupted, the general IrDA rules shall be followed with a timeout. If the infrared connection is then terminated, Ir modem  120  will, in turn, terminate the connection. 
     6. IAS and Hint Bits 
     To implement this service a new Class Name must be added to the LMP_IAS. The invention may be implemented by adding a new Class Name IrModem to the LMP_IAS. The Class Name IrModem has the attributes IrDA:TinyTP:LSAP-SEL. The correct LSAP-SEL may be retrieved by performing an LMP_IAS GetValueByClass query on the IrModem Class Name. IAS queries are defined in IrDA protocol. 
     To give the proper service hints in the device information field, the hint bit for the modem is set so that it is possible make an early detection of this service in an IrDA connection. A hint bit is a bit that indicates which services are included in the Ir device. The hint bit can be used by the Ir stack to determine whether the device has the services requested by the application before the higher level IrDA protocols connect to the device. Hint bits are discussed in the IrDA protocol. 
     The present invention has been described with reference to particular embodiments. It will be understood that the claims are not limited to the particular embodiments described herein, but should be construed to cover structural equivalents and modifications consistent with the ordinary skill in the art.