METHOD IN A TELECOMMUNICATIONS NETWORK FOR CONNECTING A DEVICE WIRELESSLY TO ANOTHER

Abstract: The present invention relates to a method and an arrangement in a data communications system. The object of the invention is to achieve a wireless communication between a processing unit and a printer using a safe transmission and an increased transmission range compared to the infrared transmission. The solution, according to the invention is a way of printing a document in a data communications system using a protocol profiled for printing in the Bluetooth protocol architecture.

Description: METHOD IN A TELECOMMUNICATIONS NETWORK FOR CONNECTING A DEVICE WIRELESSLY TO ANOTHER FIELD OF INVENTION The present invention relates to a method and an arrangement in a data communications system according to the preambles of the independent claims. More specifically it relates to a processing unit wirelessly connected to a printer. It further relates to printing a document by means of the printer, the printer being controlled by the processing unit. DESCRIPTION OF RELATED ART Processing units, e.g. PC's requiring to print documents uses typically a printer. A processing unit and a printer are generally communicating with each other through cables. But communication disruption caused by wire breakage or inadequate securing of the cable ends, added cost of providing a reliable cable and reliable associated connectors, tangling of the cables and requirements of flexibility, etc. leads to a requirement of replacing the cables. A way of communicating, using a infrared link instead of a cable is shown in the American patent US 6,055,062, which discloses an electronic printer having an attached accessory unit. The accessory unit handles e.g. optional media (e.g. paper) supply units and optional media output. To communicate with the accessory unit, the printer uses a two-ways infrared communications connection to the accessory unit to which it is immediately adjacent. However the range of the infrared link is short, so that the distance between processing unit and the printer have to be less than a few meters and there must be a clear line of sight between them. The so-called Bluetooth interface is an example of a modern radio interface, which was originally intended as replacement for cables between units. The term Bluetooth is in this disclosure used as an example of usage of short-range radio communication. By replacing the cables, the short-range radio technology provides a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures or connected to a fixed network infrastructure via a gateway. Designed to operate in a noisy frequency environment, the Bluetooth radio uses a fast acknowledgement and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a data packet, as shown in Figure 1 wherein the X-axis represents the frequency f and the Y- axis represents the time t. Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter radio packets. This makes Bluetooth radio more robust than other systems. Use of Forward Error Correction (FEC) limits the impact of random noise on longdistance links. Bluetooth radio is a wireless communication technology using a frequency- hopping scheme in the unlicensed Industrial Scientific Medical (ISM) band at 2,4 GHz. A frequency hop transceiver is applied to combat interference and fading. A shaped, binary FM modulation is applied to minimise transceiver complexity. The gross data rate is IMb/s and Time-Division Duplex (TDD) scheme is used for full duplex transmission. The Bluetooth protocol is a combination of circuit and packet switching. In Figure 1, SI denotes one time slot, and PI denotes a packet covering three time slots. A time slot is 0,625 ms long. Time slots can be reserved for synchronous packets. Each packet is normally transmitted in a different hope frequency. A packet normally covers a single slot, but can be extended to cover up to five slots. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel with simultaneously supports asynchronous data and synchronous voice. Each voice channel supports 64 kb/s synchronous (voice) link. The asynchronous channel can support an asymmetric link of maximally 721 kb/s in either direction while permitting 57,6 kb/s in the return direction, or a 432,6 kb/s symmetric link. In figure 2, the different function blocks of a system using short-range radio transceivers such as Bluetooth are shown. A radio unit 201 is connected to a link control unit 202 providing the base band. The link control unit 202 is connected to the Central Processing Unit, called CPU, 203 providing the link management. The CPU is connected to the memory 204 providing software functions and consisting of two memory units: a SRAM 205 and a FLASH 206. The CPU 203 is connected to a host interface 207. A SRAM is a fast temporary memory. FLASH is a programmable ROM. Two or more, up to eight Bluetooth units sharing the same channel form a piconet, i.e. a piconet is a collection of devices connected via Bluetooth technology in an ad hoc fashion. Within a piconet a Bluetooth unit can have either of two roles: master or slave. Within each piconet there may be one and only one master, and up to seven active slaves, i.e. a piconet starts with two connected devices, such as a portable PC and a cellular telephone, and may grow to eight connected devices. All Bluetooth devices are peer units and have identical implementations. Any Bluetooth unit can become master in a piconet. A master unit is the device in a piconet whose clock and hopping sequence are used to synchronise all other devices within the piconet. A slave unit is every device in a piconet that is not a master. The communication within a piconet is organised such that the master polls each slave according to some polling scheme. Master-to-slave transmission always starts in an even-numbered time-slot while slave-to-master transmission always starts in an odd-numbered time slot. With one exception the slave is only allowed to transmit after have been polled by the master. The slave then starts its transmission in a slave-to-master time slot immediately following the packet received from the master. The master may or may not include data in the packets used to poll the slave. The only exception to the above principle is that when a slave has an established Synchronous Connection Oriented (SCO) link, the slave is always allowed to transmit in the pre-allocated slave-to-master slot, even if not explicitly polled by the master in the preceding master-to slave slot. The term SCO-link will be disclosed in more details below. In a Bluetooth communications system there is no direct transmission between slaves in a piconet. The Bluetooth protocol stack will be described, according to the specifications of the Bluetooth system. The protocol stack which is depicted in figure 3, includes two Bluetooth units 301 and 302. In the figure the physical layer and the data link layer are shown. Baseband BB The base band describes the digital signal processing part of the hardware, i.e. the Bluetooth link controller, which carries the Bluetooth protocols and other low-level link routines. The Baseband resides in the physical layer 301 and the data link layer 304. The baseband specification defines two link types: Synchronous Connection-Oriented (SCO) links and Asynchronous Connection-Less (ACL) links. SCO links support real-time voice traffic using reserved bandwidth. ACL links support best effort traffic. Link Manager Protocol LMP LMP handles messages used for link set-up, security and control. LMP is layered over the Baseband protocol and resides in the data link layer 304. Logical Link Control and Adaptation layer Protocol, L2CAP L2CAP is also layered over the Baseband protocol and resides in the data link layer 304. L2CAP provides connection oriented and connectionless data services to upper layer protocols with multiplexing capabiHty, segmentation and reassemble operation, and group abstractions. The L2CAP Specification is only defined for ACL Hnks. Network layer 305 The network layer is currently not specified in the Bluetooth standard. High level protocol or appHcation 306 Device information, services and the characteristics of the services can be queried using the Service Discovery Protocol SDP. Like SDP, RFCOMM is layered on top of the L2CAP. RFCOMM is the 'cable replacement' protocol, which provides transport capabilities for high-level services (e.g. OBEX protocol) that use serial line as the transport mechanism. On top of the Hnk and transport protocols, the appHcations still need some specific protocols to complete the protocol stack. In the Bluetooth architecture, the appHcation-specific protocols are added on top of RFCOMM or directly on the L2CAP. L2CAP can only be accessed via a protocol which is supported by a Bluetooth profile such as RFCOMM.. The enumerated appHcation-specific protocols offer the basic functionaHty in the Bluetooth environment and they provide only the cable-replacement capabiHties. Features such as broadcasting, point-to-multipoint topologies, and scatternet possibiHties are not really utiHsed by these current high-level protocols and usage models. Thus, there are numerous possibiHties for developers to create more appHcations, the nature of which can be totally different from the existing ones. The object of the present invention is to achieve a wireless communication between a processing unit and a printer using a safe transmission and an increased transmission range compared to the infrared transmission used in the above mentioned US-patent. SUMMARY OF THE INVENTION The object of the invention is to unravel the above mentioned drawbacks and achieve a way of printing a document in a data communications system using a protocol profiled for printing in the Bluetooth protocol architecture. This is achieved according to the method and arrangement set forth in the characterising parts of the independent claims. Preferred embodiments are set forth in the independent claims. An advantage of the method and arrangement according to the present invention is that it is possible to communicate wirelessly with a printer at a wide range, up to 10 meters and extendable up to 100 meters. Another advantage is that it offers a safe transferring of data. Yet another advantage is that the present invention makes it possible to wirelessly select a printer among available printers. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram showing the relationship between timeslots and frequency hops in a system using Bluetooth. Figure 2 is a diagram illustrating the different function blocks of a Bluetooth system. Figure 3 is a diagram showing the Bluetooth protocol stack. Figure 4 is a schematic block diagram showing a communications system according to the present invention. Figure 5 is a schematic block diagram showing an entity according to the present invention. Figure 6 is a schematic block diagram showing a printer entity according to the present invention. Figure 7 shows a flowchart of the method according to the invention. Figure 8 is a bloc diagram depicting a protocol overview over the Bluetooth protocols according to the invention. Figure 9 shows a signalling sequence over a typical SDP transaction. Figure 10 shows a signalling sequence over typical WPP transactions. Figure 11 shows a signalling sequence over typical WPP transactions. Figure 12 shows a signalHng sequence over typical WPP transactions. Figure 13 shows a signalHng sequence over typical WPP transactions. Figure 14 shows a signalHng sequence over typical WPP transactions. Figure 15 shows a signalHng sequence over typical WPP transactions. DESCRIPTION OF PREFERRED EMBODIMENTS Figures 1-3 are related to prior art and described above under "Description of related art". The wording "cHent" is in this disclosure defined as the entity sending a request, and the wording "server", is in this disclosure defined as the entity receiving a request. Figure 4 shows a possible scenario of the present invention. A Bluetooth data communications system 401 includes two nodes whereof one is a processing unit, which in this example is a PC 402 and the other is a printer 403. A wireless printer protocol according to the invention is implemented in the Bluetooth protocol stack which is included in a entity, e.g. a PC-card 404, connected to or implemented in the PC 402, and in a printer entity , e.g. a printer adapter 405, connected to or implemented in the printer 403. According to the Bluetooth standard the distance between the processing unit and the printer is up to 10 meters and extendable up to 100 meters The printer adapter 405 might be connected to the printer port on the printer. The PC 402 and the printer 403 are connected to each other via a Bluetooth air interface 406. Both entities 404 and 405 comprise a respective computer, each computer comprising an internal memory for storing computer program not visible in Figure 4. The entity 404 connected to or implemented in the processing unit 402, will now be described more in detail. The entity, now referred to as 501 is shown in Figure 5. The entity 501 includes a Bluetooth protocol stack in which protocol stack a wireless printer protocol is implemented. The printer protocol comprises a printer cHent which communicates with a printer server by means of the wireless printer protocol, the Bluetooth protocol stack and air interface,. The printer server is included in a printer but is not visible in Figure 5. The entity 501 includes estabHshing means 502 for estabHshing a bi-directional wireless ACL connection between the processing unit and the printer by means of the Bluetooth protocol. The entity 501 comprises further means 503 for sending a connection request message to the printer server and negotiating means 504 for negotiating configuration parameters with the printer server. The negotiating means 504 comprises sending means 505 for sending, to the printer server, a configuration request message including no new options if the printer cHent uses default values. The negotiating means 504 comprises also sending means 506 for sending, to the printer server, a configuration request message including a suggestion of configuration options. The negotiating means 504 comprises further sending means 507 for sending, to the printer server, a further configuration request message including a suggestion of configuration options which differs from earHer suggestions of configuration options. This latter sending means 507 is to be used if the printer cHent receives a response message from the printer server that the configuration request was not acceptable due to e.g. unacceptable parameters, unknown option etc. The entity 501 comprises sending means 508 for sending a set attribute request message to the printer server, the message comprising e.g. a coding table concerning a negotiated coding type and is to be loaded by the printer server. The entity 501 comprises sending means 509 for sending keep aHve messages frequently to the printer server. A keep aHve timer 510 is implemented in the entity 501 and comprises starting means 511 for starting and restarting the keep aHve timer 510 each time a vaHd message is sent to the printer server and each time a vaHd message is received from the printer server. The keep aHve timer 510 further comprises closing means 512 for closing the connection between to the printer server, when the keep aHve timer 510 expires. For starting one or more printjobs the entity 501 comprises starting means 513 which starting means 513 comprises sending means 514 for sending a request message to the printer server comprising a request to start a printjob. The print data that is to be printed by the printer is sent by means of the sending means 515 for sending the print data to the printer server. Said means 515 includes sending means 516 for sending a number of request messages to the printer server, the messages comprising print data. A printing process might be broken, e.g. because the printer runs out of paper or the ACL connection is broken, etc. This is reported by the printer server in a message received by the printer cHent. The entity 501 comprises means 527 for interpret the message and give a note to the user of the processing unit, e.g. by presenting the note on the screen of the PC. E.g. a refill of paper or a new creation of a disconnected ACL connection might make, but the entity 501 comprises continuing means 517 for continuing the printing process by continuing to send print data request messages to the printer server, starting with the print data subsequent to a last received print data acknowledgement message. The entity 501 comprises stopping means 518 for stopping the keep aHve timer 510 when an ACL connection is disconnected during a printing process. The entity 501 further comprises requesting means 519 for requesting a reconnection of a session defined by the session identifier in a message sent to the printer server to be used when a new ACL connection is created to the printer, after a break. The entity 501 comprises stopping means 520 for stopping the print job said stopping means 520 comprises sending means 521 for sending a message to the printer server, the message comprising a request to stop the printjob. The stopping means 520 wiU be used when all data to be printed in a printjob is sent to the printer. The entity 501 further comprises closing means 522 for closing the connection between the processing unit and the printer, the closing means comprising sending means 523 for sending a message to the printer server, the message comprising a request to disconnect a session identified by a session identity. The entity 501 comprises stopping means 524 for stopping the sending of keep aHve messages after closing a connection between the printer cHent and the printer server. The entity also comprises a receiver 525 for receiving messages sent from a printer and a transmitter 526 for sending messages to the printer. The printer entity 405 connected to or implemented in the printer 403 shown in Figure 4, wiU now be described more in detail. The printer entity, now referred to as 601 is shown in Figure 6. The printer entity 601, including a Bluetooth protocol stack in which a wireless printer protocol is implemented, said protocol comprising a printer server which communicates, by means of the wireless printer protocol, the Bluetooth protocol stack and air interface, with a printer cHent, e.g. the printer cHent in the entity 501 described above . The printer cHent is included in a processing unit 402 and is not visible in Figure 6. The printer entity 601 comprises a receiver 602 for receiving messages sent from a processing unit and a transmitter 603 for sending messages to the processing unit. The printer entity 601 further comprises responding means 604 for responding upon a connection request whether the connection is successful or not, in a response message sent to the printer cHent. The printer entity 601 comprises negotiating means 605 for negotiating configuration parameters with the printer cHent within the processing unit. The negotiating means 605 comprises responding means 606 for responding upon a configuration request whether the configuration options in the configuration request are supported by the printer server or not. The negotiating means 605 comprises loading means 607 for loading a coding table or other optional attributes sent from the printer cHent. The negotiating means 605 further comprises sending means 608 for sending a response, whether the loading of the coding table was successful or not, to the printer cHent. The printer entity 601 comprises sending means 609 for sending keep aHve messages frequently to the printer cHent. A keep aHve timer 610 is implemented in the printer server within the printer entity 601. The printer entity 601 comprises starting and restarting means 611 for starting the keep aHve timer each time a vaHd message is received from the printer cHent and each time a vaHd message is sent to the printer cHent. The printer entity 601 comprises starting means 612 for starting a print job. The starting means 612 comprises confirming means 613 for confirming a start printjob request message sent to the printer cHent The printer entity 601 comprises receiving means 614 for receiving print data from the printer cHent. The receiving means 614 including sending means 615 for sending an acknowledgement message to the printer cHent after receiving a previous decided number of print data request messages. The printer entity 601 comprises indicating means 616 for indicating, in a message sent to the printer cHent, that the printer has reported an exemption condition, e.g. that the printer is out of paper, if the printer runs out of paper. The printer entity 601 further comprises indicating means 617 for indicating, in a message sent to the printer cHent, when the printer clears the exemption, e.g. that the printer is refilled, when the printer is refilled. The printer entity 601 comprises stopping means 618 for stopping the keep aHve timer when an ACL connection to the processing unit is disconnected during a printing process. The printer entity 601 comprises sending means 619 for sending a response message to the printer cHent, according to whether a reconnection request is granted or not. The printer entity 601 comprises stopping means 620 for stopping the print job. The stopping means 620 including sending means 621 for sending a response message, after the printer server has received a request to stop the printjob, the message comprising a confirmation that this is apprehended and is sent to the printer cHent. The printer entity 601 comprises sending means 622 for sending a response message to the printer cHent, according to whether a disconnection request is granted or not. The printer entity 601 further comprises stopping means 623 for stopping the sending of keep aHve messages after the connection to the printer cHent is closed. Figure 7 shows a flowchart of a possible scenario of the printing process according to the present invention. The method includes the foUowing steps: 701. A bi-directional wireless Asynchronous Connection-Less (ACL) connection is estabHshed between the processing unit 402 and the printer 403 by means of the printer protocol calHng the L2CAP requesting the connection and the L2CAP creating the connection. 702. A connection is estabHshed between the printer cHent and the printer server for one or more printjobs. 703. The processing unit 402 and the printer 403 negotiate configuration parameters for said connection. 704. Keep aHve messages are sent frequently during the session from the processing unit 402 to the printer 403 and from the printer 403 to the processing unit 402. 705. The processing unit 402 starts the printjob and 706. sends the printer data to the printer 403. 707. The print job is stopped and 708. the connection is closed between the processing unit 402 and the printer 403. The method is implemented by means of a computer program product comprising the software code portions for performing the steps of the method. The computer program product is run on a computer stored in a digital computer within the process unit 402 and within the printer 403, e.g. in the printer adapter 405. The computer program is loaded directly or from a computer usable medium, such as floppy-disc, CD, Internet etc. Figure 8 is a bloc diagram depicting a protocol overview over the Bluetooth protocols including the wireless printer protocol WPP according to the invention. The left side represents the PC 801 and the right side represents the Printer 802. The Host Control Interface HCI is marked as a horizontal Hne. The HCI provides a command interface to the baseband controUer, Hnk manager, and access to hardware status and control registers. SDP, L2CAP and LMP are described above, under Related Art. WPP will be described more in detail below. The interface between two entities on the same layer , a so-called horizontal interface, is defined by it's protocol 803, 804, 805 and 812, e.g. L2CAP on PC communicates with L2CAP on printer using the L2CAP protocol. The actual flow of data (Protocol Data Units, PDU:s) is done between entities in different layers 806, 807, 808, 809, 810 and 811, a so-caUed vertical interface. On the PC side the protocols is implemented by following appHcations: - . CHent L2CA AppHcation implements L2CAP - CHent Printer AppHcation implements WPP - CHent Discovery AppHcation implements SDP On the printer side the protocols is implemented by following appHcations: - Server L2CA AppHcation implements L2CAP. - Server Printer AppHcation implements WPP. - Server Discovery AppHcation implements SDP. The printing method according to the invention wiU now be described more in detail. A processing unit requires to print a document, i.e. to perform a printjob, by means of a printer. The processing unit wishes to know which printers that are available, and select one of them, therefore the printing process starts with the Device Discovery procedure, which is a procedure known from the art. Figure 9 shows a sequence diagram of a typical SDP transaction between the CHent Discovery AppHcation 901 and the Server Discovery AppHcation 902. It is assumed that inquire has been performed. As a result of inquire the class of device is retrieved. Class of device indicates the type of device and which type of services the device supports. It is also assumed that a point to point connection with the server has been estabHshed, using L2CAP. The PrinterServiceClassId is represented as a UniversaHy Unique Identifier (UUID) and is known by cHent discovery appHcation. A message, e.g. a denoted SDP_ServkeSearch&eq message 903 is sent, from CHent to Server, to ask which services, in this case printers that are available. The server returns service records handles associated with the respective available printers, e.g. in a denoted SDP_ServiceSearchRsp message 904. The printer service record database serves as a repository of discovery-related information. All of the information about a service that is maintained by an SDP server is contained in a single service record. The service record consists entirely of a Hst of attributes. A service record handle uniquely identifies each service record within the SDP server, according to Service Discovery Protocol, Bluetooth Specification version 1.0 B concerning SDP and Appendix VIII, Bluetooth Assigned Numbers, Bluetooth Specification version 1.0 B concerning assigned numbers for predefined attributes and their identity. The CHent selects one of the available printers and requests for its attributes, e.g. the address of the printer, a in a message, e.g. a denoted SOP_ServkeAttήbuteϊeq message 905 using the service record handle. The attributes are returned in one or more messages, e.g. denoted SDP_ ServkeAttributeRsp messages 906. The CHent stores the received attributes and terminate the L2CAP connection A bi-directional wireless asynchronous connection-less (ACL) connection is estabHshed (701) between the processing unit and the printer. This is achieved by means of the printer protocol in the processing unit calHng the L2CAP in the within the same unit, requesting the connection to the printer. The printer is connected e.g. by means of the printer address being one of the attributes received. The L2CAP creates the connection and notifies the created connection the printer protocol. Figure 10 shows sequence diagrams of a typical WPP transactions concerning the connection operations between the WPP CHent 1001 and the WPP Server 1002, according to the invention A creation of a session between a cHent printer appHcation (source) and a server printer appHcation (destination) is to be requested, i.e. for estabHshing a connection for one or more printjobs. This is performed by sending a message, e.g. a denoted WTP_ConnectionXReq message 1003, from the WPP cHent 1001 to the WPP server 1002. This is shown in Figure 10. A status indication to the cHent printer appHcation whether the connection was successful or not and making the session vaHd if successful is required. This is be performed in a message by the WPP server 1002, e.g. in a denoted WPP_Connection_Rsp message 1004, also shown in Figure 10. This message also includes a session identity. The next step of the printing process is the WPP negotiation procedure according to the invention. Figure 11 a-c and 12 shows sequence diagrams of a typical WPP transactions concerning the negotiation operations between the WPP CHent 1001 and the WPP Server 1002, according to the invention. After creating the session a configuration of the WPP server 1002 is required. Examples of configuration options are e.g. the number of print data request messages to be received by the printer before return a confirmation message, coding type and table size. Figure 11a, b and c shows three different sub-scenarios of a successful negotiation of a coding type for data compression. A message, e.g. a denoted WPP_Configuration_Req message, is sent from the WPP cHent 1001 to WPP server 1002 to estabHsh an initial logical Hnk transmission contract between the WPP cHent 1001 and WPP server 1002 and to negotiate configuration parameters, e.g. the coding type. In this example the WPP server 1002 supports the coding types hamming, table size = 80 (default) and huffman table size = 80. The three respective sub-scenarios may be a continuation of the connection scenario in Figure 10. In the first sub-scenario, shown in Figure 11a, the WPP cHent 1001 uses default values, i.e. hamming, table size = 80 and accordingly the WVP_Configuration_Req message 1101 sent, from the WPP cHent 1001 to the WPP server 1002, includes no new options. Since that is a coding type that the WPP server 1002 supports, it responses success in a message, e.g. a denoted WPP_Configuration_Rsp message 1102. Figure lib shows the second sub-scenario in which the WPP cHent 1001 requests the WPP server 1002, in message, e.g. a denoted WPP_Configuration_Req message, if hamming, table size = 100 can be used 1103. This is not a coding type that the WPP server 1002 supports and accordingly it responses in a message, e.g. a denoted WVP_Configuration_Ksp message 1104, failure and suggests that hamming, table size = 80 can be used. The WPP cHent 1001 supports also hamming, table size = 80 and responses this to the WPP server 1002 in a message, e.g. a denoted WPP_Configuration_Req message 1105. The WPP server responses success in a message, e.g. a denoted WPP_Configuration_Rsp message 1106. In the third scenario, shown in Figure 11 c, the WPP cHent 1001 suggests an coding type which is unknown for the printer, i.e. a coding type not supported by the printer, and a size = 100, in a message, e.g. a denoted WPP_Configuration_Req message, sent 1107 to the WPP server 1002. Since this coding type is unknown for the WPP server 1002, it responses in a message, e.g. a denoted W r PP_Config raήon_Rsp message 1108 failure and that the coding type is unknown. The WPP cHent 1001 then tries another coding type that it supports, in this example huffman, size = 80, in a subsequent message, e.g. a denoted WTP_Configuration_Req message 1109 sent to the WPP server 1002. The WPP server 1002 supports huffman, size = 80 and accordingly it responses success and confirms huffman, size = 80 in a message, e.g. a denoted WPP_Configuration_Rsp message that is sent 1110 to the WPP cHent 1001. After the configuration negotiation of coding type according to e.g. the scenarios depicted in Figures lla-c, the WPP cHent 1001 requests to set an attribute which is iUustrated in Figure 12. The WPP cHent 1001 sends a coding table concerning the negotiated coding type in a message, e.g. a denoted WPP_Set_Attribute_ eq message sent 1201 to the WPP server 1002. The WPP server loads the coding table to be used and confirms whether it was successful or failure in a message, e.g. a denoted WPP_Set_Attribute_Rsp message 1202 sent to the WPP cHent 1001. The next step of the printing process is the WPP printing procedure. Figure 13a- d, 14 and 15 shows sequence diagrams of a typical WPP transactions concerning the printing operations, between the WPP cHent 1001 and the WPP server 1002, according to the invention. Figures 13a-d shows a first sub-scenario of a successful printing of one print job. Figure 13a shows the procedure for sending keep aHve messages. When the connection has been estabHshed and negotiation has been performed, keep aHve messages are to be sent, by the WPP cHent 1001, 1303 and WPP server 1002, 1304, frequently, e.g. once each 5 second, as an indication that the source is up and running. Such a message is a denoted WPP_Keep_Alive message. If a break occurs when printing, the printer wiU find out that, since it does not receive any more keep aHve messages. The printer then terminates the printjob and can let other users in. A break can also occur on the printer side. There is also occasions when the printer or processing unit are hard loaded, sending keep aHve messages just to tell the receiver that it still aHve but it goes slowly at the moment. When a connection has been disconnected by WPP cHent ,WPP cHent 1001 and WPP server 1002 shall stop sending denoted WV _Keep_Aliυe messages. A WPP Keep AHve Timer is restarted each time a vaHd message is received from the remote endpoint. The timer is implemented on both cHent and server side. If the Keep AHve timer expires the remote endpoint is considered faulty and the connection is closed and higher level appHcations is notified. The Keep AHve Timer shaU be stopped when a Hnk is disconnected and restarted when a new Hnk is estabHshed with the remote endpoint. If a new Hnk is estabHshed within a reasonable time, e.g. 10 seconds, the printjob continues where broken. Each WPP message will trigger a restart of a WPP timer. In Figure 13b a start of a printjob and sending of data to be printed is shown. The WPP cHent 1001 requests the WPP server 1002 to start a printjob in a denoted WPP_StartJPrint_Req message 1305 s, which in turn confirmed by the WPP server (1002) in a denoted WPP_Start_Print_Cfm message 1306. The WPP cHent then requests the WPP server 1002 to print data included in a number of denoted WΨP_Pήnt_D ta_Req messages 1307, 1308. A confirmation is to be sent after the WPP server 1002 has received a number N WPP_Print_Data_Req messages 1307, 1308. The value of N is negotiated during configuration e.g. N = 4. The acknowledgement is e.g. sent in a denoted WPP Print_ Oata_Ack message 1309. This procedure goes on until all data to be printed is received by the printer server. I.e. until the last WPP_Print_Data_Req message 1310 is received. When aU data to be printed is sent to the printer server the cHent requests the printer server to stop the printjob. This is shown in Figure 13c wherein the WPP cHent 1001 sends a denoted WPP_End_Pήnt_ eq message 1311 to the WPP server 1002. That this is apprehended by the printer server is reported e.g. in a denoted WPPJ nd_Print_Rsp message 1312 sent to the WPP cHent 1001. After performing one or more printjobs or if a break of the printjob is requested, the cHent requests a disconnection of a session defined by the session identifier. Depicted in Figure 13d, this request is performed by e.g. sending a denoted WPP_DisconnectJβq message 1313 from the WPP cHent 1001 to the WPP server 1002 and a response, whether the disconnection is granted or not, is sent in the opposite direction in a denoted WΨP_Disωnnect_Rsp message 1314. When the session is disconnected the WPP cHent 1001 and the WPP server 1002 stops sending WPP_K.sep_A.live messages. Figures 14 shows a second sub-scenario of a successful printing of one printjob when the printer is out of paper. Negotiation has been performed, a connection is estabHshed and keep aHve messages are sent as described above though not visible in Figure 14. The WPP cHent 1001 has requested the WPP server 1002 to start the printjob in a message, e.g. a denoted WPP_Start_Print_Req message 1401, which is responded success to in a message, e.g. a denoted WVP_Start_Print_Rsp message 1402. When the WPP cHent 1001 has requested the WPP server 1002 to print data included in a number of messages, e.g. denoted WPP_Print_Data_Req messages 1403, 1404, being acknowledged by the WPP server 1002 in a message, e.g. a denoted WPP_Pήnt_Data_Ack message 1405, the printer is out of paper. The printer server then has to report this to the cHent. This can be performed by the WPP server 1002 sending a message, e.g. a denoted WPP_Statιts_lnd message 1406, indicating that the printer is out of paper to the WPP cHent 1001. The message is interpreted by the wireless printer protocol and reported to the user of the processing unit, e.g. by presenting a note on the PC screen. The message is obtained by a user of the processing unit including the cHent, who refills the printer. The printer server then reports that the printer is refiUed to the WPP cHent 1001 by sending a message, e.g. a denoted WPP_Status_Ind message 1407. The last received denoted WPP_Print_Data_Ack message 1405 defines where to continue the printing by sending messages, e.g. denoted WPP_Print_Data_R£q messages 1408, 1409 from the WPP cHent 1001 to the WPP server 1002. The printer wiU throw data if already printed or if a part of it has been printed. The printing process then continues as described above. Figures 15 shows a third sub-scenario of a successful printing of one printjob when the ACL connection is disconnected. Negotiation has been performed, a connection is estabHshed and keep aHve messages are sent as described above though not visible in Figure 15. The WPP cHent 1001 has requested the WPP server 1002 to start the printjob in a message, e.g. a denoted WPP_Start_Print_Αsq message 1501, which is responded success to in a message, e.g. a denoted WPP_Start_Pήnt_ sp message 1502. When the WPP cHent 1001 has requested the WPP server 1002 to print data included in a number of messages, e.g. WPP_Print_Data_Req messages 1503, 1504, the ACL connection is disconnected, indicated by HCI. The Keep AHve Timer is stopped by the WPP cHent 1001. A reconnection of the session is required because it is possible for another cHent to start a printjob during ACL-disconnected. A session identity is used to identify the different WPP entities. If another job is ongoing the server will not accept the reconnection. The time the server will wait for the reconnection has to be handled by a reconnection timer. If the timer times out the ongoing job will be flushed. After creating a new ACL-connection a reconnection of the session is requested. This can be performed by the WPP cHent 1001 by sending a message, e.g. a denoted WPP_Jkeconnect_Req message 1506 requesting a reconnection of the session defined by the session identifier. A response according to whether the reconnection is granted or not is sent in a message, e.g. a denoted WPP_ReconnectXKsp message 1507. In this example it is granted. The WPP Keep AHve timer is started again. The last received denoted WPP_Print_J)ata_Ack message 1505 defines where to continue the printing by sending messages, e.g. a WPPJ > ήnt_DataX&βq messages 1507, 1508 from the WPP cHent 1001 to the WPP server 1002. The printer server wiU throw data if already printed or if the packet is detected to be a retransmission. The printing process then continues as described above. The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of invention, which is defined by the appendant claims.

Claims: CLAIMS 1. A method for printing a document in a data communications system, the system including a processing unit including a printer cHent (1001) and a printer including a printer server (1002), the processing unit and the printer using for communication between each other a wireless printer protocol, the Bluetooth protocol stack and air interface, the Bluetooth protocol stack including a wireless printer protocol and a Logical Link Control and Adaptation Protocol (L2CAP), the method including the steps of: establishing (701) a bi-directional wireless asynchronous connection-less (ACL) connection between the processing unit and the printer by means of the printer protocol calHng the L2CAP requesting the connection and the L2CAP creating the connection; establishing (702) a connection for one or more printjobs between the printer cHent (1001) and the printer server (1002); negotiating (703) configuration parameters between the printer cHent (1001) and the printer server (1002); sending (704) keep aHve messages frequently from the printer cHent (1001) to the printer server (1002) and from the printer server (1002) to the printer cHent (1001); starting (705) a print job; sending (706) the print data from the processing unit to the printer; stopping (707) the print job; and closing (708) the connection between the processing unit and the printer. 2. The method according to claim 1, comprising the further step to be taken before the step of estabHshing (701) a bi-directional wireless ACL connection: selecting a printer among a number of available printers. 3. The method according to claim 2, wherein the step of selecting a printer is performed by using the Device Discovery Protocol. 4. The method according to any of the previous claims, comprising the further step to be taken before the step of estabHshing (701) a bi-directional wireless ACL connection: obtaining an address of a printer. 5. The method according to claim 4, wherein die step of obtaining an address of a printer is performed by using the Device Discovery Protocol. 6. The method according to claim 5, wherein the estabHshing a connection for one or more printjobs is performed by sending a connection request message (1003) from the printer cHent (1001) to the printer server (1002). 7. The method according to claim 6, wherein the estabHshing a connection for one or more printjobs is performed by responding upon the request whether the connection was successful or not, in a response message (1004) sent from the printer server (1002) to the printer cHent (1001). 8. The method according to any of the previous claims, wherein the step of negotiating configuration parameters (503), between the printer cHent (1001) and the printer server (1002), is performed by the printer cHent (1001) requesting configuration in a message (1101) sent to the printer server (1002), the message including no new options, if printer cHent (1001) uses default values. 9. The method according to any of the previous claims, wherein the step of negotiating configuration parameters(503), between the printer cHent (1001) and the printer server (1002), is performed by the printer cHent (1001) requesting configuration in a message (1103) sent to the printer server (1002), the message including a suggestion of configuration options. 10. The method according to claim 9, wherein said configuration request is responded to by the printer server (1002) in a message (1102, 1104, 1106) indicating whether the configuration options in the configuration request are supported by the printer server (1002) or not. 11. The method according to claim 10, including the further step, if the configuration request responds failure; sending a further configuration request message (1105, 1109) from the printer cHent (1001) to the printer server (1002), the message including suggestion of configuration options which differs from earHer suggestions of configuration options.. 12. The method according to any of the previous claims, comprising the further step to be taken after the step of negotiating configuration parameters (503): sending a set attribute request message (1201) from the printer cHent (1001) to the printer server (1002) the message comprising a coding table concerning a negotiated coding type. 13. Method according to claim 12, comprising the further step of: the printer server (1002) loading the coding table by means of said received set attribute request message (1201). 14. Method according to claim 13, comprising the further step of: sending a response whether the loading of the coding table was successful or not in a message (1202) from the printer server (1002) to the printer cHent (1001). 15. The method according to any of the previous claims, wherein a keep aHve timer is implemented in the printer cHent (1001) and in the printer server (1002), comprising the further step of : starting the keep aHve timer each time a vaHd message is received from the remote endpoint. 16. The method according to claim 15, wherein said keep aHve timer expires, comprising the further step of: closing the connection. 17. The method according to any of the previous claims, wherein the step of starting a print job (505) is performed by the printer cHent (1001) requests the printer server (1002) to start a printjob in a request message (1305). 18. The method according to claim 17, wherein said start printjob request message (1305) is received and confirmed by the printer server (1002), the confirmation sent in message (1306) to the printer cHent (1001). 19. The method according to any of the previous claims, wherein the step of sending the print data from the processing unit to the printer (506), is performed by requesting the printer server (1002) to print data sent in a number of messages (1307, 1308, 1310). 20. The method according to claim 19, comprising the further step to be taken after the printer server (1002) have received a previous decided number of print data request messages: sending an acknowledgement message (1309) from the printer server (1002) to the printer cHent (1001). 21. The method according to any of the previous claims, comprising the further step to be taken if the printer runs out of paper: indicating that the printer is out of paper in a message (1406) sent from the printer server (1002) to the printer cHent (1001). 22. The method according to claim 21, comprising the further step to be taken when the printer is refilled: indicating that the printer is refilled in a message (1407) sent from the printer server (1002) to the printer cHent (1001). 23. The method according to claim 22, comprising the further step to be taken after the printer cHent (1001) has received an indication message (1407) that the printer is refiUed: continuing the printing process by continuing to send print data request messages, (1408, 1409) starting with the print data subsequent to the last received print data acknowledgement message (1405). 24. The method according to any of the claims, wherein the ACL connection is disconnected during printing, the method comprising the further step of: stopping the keep aHve timer. 25. The method according to claim 24, wherein a new ACL connection is created comprising the further step of: requesting a reconnection of the session defined by the session identifier in a message (1506) sent from the printer cHent (1001) to the printer server (1002). 26. The method according to claim 25, comprising the further step of: sending a response according to whether the reconnection is granted or not in a message (1507) from the printer server (1002) to the printer cHent (1001). 27. The method according to claim 26, comprising the further step to be taken after the printer cHent (1001) has received a granted reconnection response: continuing the printing process by continuing to send print data request messages (1508, 1509), starting with the print data subsequent to the last received print data acknowledgement message (1505). 28. The method according to any of the previous claims, wherein the step of stopping the print job (707), is performed by, after sending all data to be printed to the printer server (1002), sending a request to stop the printjob in a message (1311)from the printer cHent (1001) to the printer server (1002). 29. The method according to claim 28, comprising the further step to be taken after the printer server (1002) has received a request to stop the printjob; sending a response message (1312), comprising a confirmation that this is apprehended, from the printer server (1002) to the printer cHent (1001). 30. The method according to any of the previous claims, wherein the step of closing the connection between the processing unit and the printer (708) is performed by the printer cHent (1001) requesting a disconnection of the session defined by the session identity in a message (1313) sent to the printer server (1002). 31. The method according to claim 30, wherein the printer server responses to whether the disconnection was granted or not, in a response message (1314) sent from the printer server (1002) to the printer cHent (1001). 32. The method according to any of the previous claims, comprising the further step to be taken after the step of closing the connection between the processing unit and the printer (708): stopping the sending of keep aHve messages. 33. A computer program product directly loadable into the internal memory of a digital computer within a processing unit or printer in a communication system, comprising the software code portions for performing the steps of any of the claims 1-32, when said product is run on a computer. 34. A computer program product stored on a computer usable medium, comprising readable program for causing a computer within a processing unit or printer in a communication system, to control an execution of the steps of any of the claims 1-32. 35. An entity (501) included in a Processing unit (402), the entity includes a Bluetooth protocol stack comprising a Logical Link Control and Adaptation Protocol (L2CAP) characterised in that the Bluetooth protocol stack further comprises a wireless printer protocol, said printer protocol comprising a printer cHent which communicates (803) with a printer server, included in a printer (403), by means of the Bluetooth protocol stack and air interface, the entity (501) further comprises: estabHshing means (502) for estabHshing a bi-directional wireless ACL connection to the printer (403) by calHng the L2CAP requesting the connection; estabHshing means (503) for estabHshing a connection for one or more printjobs negotiating means (504) for negotiating configuration parameters with a printer server within the printer(403); sending means (509) for sending keep aHve messages frequently to the printer server ; starting means (513) for starting a print job; sending means (515) for sending the print data to the printer server; stopping means (520) for stopping the print job; and closing means (522) for closing the connection between the processing unit (402) and the printer (403). 36. The entity (501) according to claim 35, characterised by comprising sending means for sending a connection request message from the printer cHent to the printer server. 37. The entity (501) according to any of the claims 35-36 wherein when negotiating configuration parameters, the printer cHent uses default values, characterised by comprising sending means (505) for sending a configuration request message to the printer server, the message including no new options. 38. The entity (501) according to any of the claims 35-37, characterised by comprising sending means (506) for sending a configuration request message to the printer server, the message including a suggestion of configuration options. 39. The entity (501) according to any of the claims 35-38, characterised by comprising sending means (507) for sending a further configuration request to the printer server, the message including suggestion of configuration options which differs from earHer suggestions of configuration options. 40. The entity (501) according to any of the claims 35-39, characterised by comprising sending means (508) for sending a set attribute request message to the printer server, the message comprising a coding table concerning a negotiated coding type. 41. The entity (501) according to any of the claims 35-40, characterised in that a keep aHve timer (510) is implemented in the printer cHent. 42. The entity (501) according to claim 41, characterised by comprising starting means (511) for starting the keep aHve timer (510) each time a vaHd message is received from the printer (403). 43. The entity (501) according to claim 42, characterised by comprising closing means (512) for closing the connection between the printer cHent and the printer server, when the keep aHve timer(510) expires. 44. The entity (501) according to any of the claims 35-43, characterised by comprising sending means (514) for sending a request message to the printer server comprising a request to start a printjob. 45. The entity (501) according to any of the claims 35-44, characterised by comprising sending means (516) for sending a number of request messages to the printer server, the messages comprising print data. 46. The entity (501) according to any of the claims 35-45, wherein a refiU of paper has broken a printing process, characterised by comprising continuing means (517) for continuing the printing process by continuing to send print data request messages to the printer server, starting with the print data subsequent to the last received print data acknowledgement message. 47. The entity (501) according to claim 41, characterised by comprising stopping means (518) for stopping the keep aHve timer when the ACL connection is disconnected during a printing process. 48. The entity (501) according to any of the claims 35-47, wherein a new ACL connection is created to the printer after a break, characterised by comprising requesting means (519) for requesting a reconnection of a session defined by the session identifier in a message sent to the printer server. 49. The entity (501) according to claim 48, wherein a granted reconnection response message is received, characterised by comprising continuing means (517) for continuing the printing process by continuing to send print data request messages to the printer server, starting with the print data subsequent to the last received print data acknowledgement message. 50. The entity (501) according to any of the claims 35-49, wherein all data to be printed is sent to the printer characterised by comprising sending means (521) for sending a message to the printer server, the message comprising a request to stop the printjob. 51. The entity (501) according to any of the claims 35-50, characterised by comprising sending means (523) for sending a message to the printer server, the message comprising a request to disconnect a session identified by a session identity. 52. The entity (501) according to any of the claims 35-51, characterised by comprising stopping means (524) for stopping the sending of keep aHve messages after closing a connection between the printer cHent and the printer server. 53. A printer entity (601) included in a Printer (403), the printer entity (601) including a Bluetooth protocol stack comprising a Logical Link Control and Adaptation Protocol (L2CAP) characterised in that the Bluetooth protocol stack further includes a wireless printer protocol, said printer protocol comprising a printer server which communicates with a printer cHent, included in a processing unit (402), by means of the wireless printer protocol, the Bluetooth protocol stack and air interface, the printer entity (601) further comprises: negotiating means (605) for negotiating configuration parameters with a printer cHent within the processing unit; sending means (609) for sending keep aHve messages frequendy to the printer cHent ; starting means (612) for starting a print job; receiving means (614) for receiving print data from the printer cHent; and stopping means (620) for stopping the print job. 54. The printer entity (601) according to claim 53 characterised in comprising responding means (604) for responding upon a connection request whether the connection is successful or not, in a response message sent to the printer cHent. 55. The printer entity (601) according to any of the claims 53-54 characterised in comprising responding means (606) for responding upon a configuration request whether the configuration options in the configuration request are supported by the printer server or not. 56. The printer entity (601) according to any of the claims 53-55 characterised in comprising loading means (607) for loading a coding table sent from the printer cHent. 57. The printer entity (601) according claim 56 characterised in comprising sending means (608) for sending a response whether the loading of the coding table was successful or not to the printer cHent. 58. The printer entity (601) according to any of the claims 53-57, characterised in that a keep aHve timer (610) is implemented in the printer server. 59. The printer entity (601) according to claim 58, characterised by comprising starting means (611) for starting the keep aHve timer each time a vaHd message is received from the printer. 60. The printer entity (601) according to any of the claims 53-59, characterised in comprising confirming means (613) for confirming a start printjob request message sent to the printer cHent. 61. The printer entity (601) according to any of the claims 53-60, characterised in comprising sending means (615) for sending an acknowledgement message to the printer cHent after receiving a previous decided number of print data request messages. 62. The printer entity (601) according to any of the claims 53-61, characterised in comprising indicating means (616) for indicating, in a message sent to the printer cHent, that the printer is out of paper, if the printer runs out of paper. 63. The printer entity (601) according to any of the claims 53-62, characterised in comprising indicating means (617) for indicating, in a message sent to the printer cHent, that the printer is refilled, when the printer is refilled. 64. The printer entity (601) according to any of the claims 53-63, characterised by comprising stopping means (618) for stopping the keep aHve timer when an ACL connection to the processing unit is disconnected during a printing process. 65. The printer entity (601) according to any of the claims 53-64, characterised in comprising sending means (619) for sending a response message to the printer dient, according to whether a reconnection request is granted or not. 66. The printer entity (601) according to any of the claims 53-65, characterised in comprising sending means (621) for sending a response message, after the printer server has received a request to stop the printjob, the message comprising a confirmation that this is apprehended and is sent to the printer cHent. 67. The printer entity (601) according to any of the claims 53-66, characterised in comprising sending means (622) for sending a response message to the printer cHent, according to whether a disconnection request is granted or not. 68. The printer entity (601) according to any of the claims 53-67, characterised in comprising stopping means (623) for stopping the sending of keep aHve messages after the connection to the printer cHent is closed. 69. Communications system (401) characterised by comprising a processing unit (501) according to any of the claims 35-52 and a printer entity (601) according to any of the claims 53-68.

Inventors: ERIKSSON HENRIK, FRITZ OERJAN, OEBERG ANDERS, PELDAN PETER, ERIKSSON, HENRIK, FRITZ, OERJAN, OEBERG, ANDERS, PELDAN, PETER
Applicants: ALLGON AB
Application year: 2001
Main classification: H04L12
IPC codes: H04L12