Electrical computers and digital processing systems: multicomput – Computer-to-computer session/connection establishing
Reexamination Certificate
1999-11-09
2003-02-11
Vu, Viet D. (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer-to-computer session/connection establishing
C709S237000, C709S250000, C709S241000
Reexamination Certificate
active
06519644
ABSTRACT:
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' 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
Harris Jonas
Lindquist Tobias
Tuneld Mats
Van Der Winkel Ramon
Burns Doane Swecker & Mathis L.L.P.
Telefonaktiebolaget LM Ericsson (publ)
Vu Viet D.
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