WO2005062551A1

WO2005062551A1 - Avoid disruption of gprs/umts traffic

Info

Publication number: WO2005062551A1
Application number: PCT/NO2003/000434
Authority: WO
Inventors: Per Magne Lindvik Hoff; Per Øyvind ØDEGAARD; Ezzat Kaafarani; Paul Schliwa-Bertling
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2003-12-22
Filing date: 2003-12-22
Publication date: 2005-07-07
Also published as: AU2003291783A1

Abstract

A method within a GPRS/UMTS telecommunication network for interruption free unidirectional communication between a sender (2) and one or more receivers (1), where the communication traffic is of a unacknowledged mode and the sender (2) and one or more receivers (1) constitutes a run time timer that is started at initialization of a new traffic session, the session will run uninterrupted while the timer(s) is/are running, and the timer(s) have/has a fixed or prechosen run time before time out, said time out will start a sender initiated procedure so as to restart the run time timer specified in that simultaneously or substantially simultaneously as the run time timer(s) has/have been initialized.

Description

AVOID DISRUPTION OF GPRS/UMTS TRAFFIC

Field of the Invention

The present invention relates to packet switched communication within mobile communication network, more particularly to half duplex communication over such networks .

Background of the invention

There is a growing interest in services within telecommunication that uses simplex or half duplex, such services can be streaming of data, broadcast services, narrowcasting, multi-casting, anycasting, that is; when the closest member of a group retransmits, using multicasting, a pet child has many names, the common feature being one transmitter is sending information to one or more receivers, using unacknowledged modes. There are a lot of services from ISP's, most common are maybe the download services, that is, services where subscribers can download content to their mobile station, such as multimedia files etc. These services are quite often streaming services, using unacknowledged mode and they often need quite long periods of downloading without any interruption. If these kind of services are interrupted, particularly when it is moving pictures, films or music that are downloaded, one will experience this as poor listening quality, and/or watching quality. In some markets, other services running uni-directional over GPRS is growing very popular, particularly the walkie-talkie service in the USA.

Thus there is a need for improvement of the GPRS bearer to support better payload services where MS terminated traffic is sent over longer periods (half duplex service) without any requirement for MS originated responses. Technical Background

Problem seen from Mobile End User:

The GPRS bearer service has a nasty non-transparent feature: SGSN must regularly halt the downlink flow and get a confirmation of the current MS cell position. This procedure is denoted as Paging and is initiated by SGSN, and performed by BSS. Downlink is the direction from SGSN to MS. This problem exists when these three conditions apply:

1. Payload is only sent from SGSN for a long period (more than 44 sec) without any response from the mobile .

2. LLC unacknowledged mode is used for the payload transfer.

3. The mobile does not change radio cell.

This periodic disruption (typically each 44 second) is of course quite annoying for the End User, and the reason is found in the GPRS standard, ref . [2] .

The above mentioned problems regarding interrupts affects many services and in particular all services running over a GPRS bearer which are uni-directional (MS terminated) in nature in longer periods than the READY timer in GPRS Mobility Management (GMM) . One relevant example, as mentioned above, is the "Walkie-Talkie" service "Push To Talk", which is very popular in the United States. Another example is Multimedia Streaming services. These are, but a few services, as earlier mentioned, that are severely affected by interrupts in the communication between the transmitter and the one or many MS. Following are two figures that in a schematic way illustrate the transmission plane and the signalling plane between a SGSN and a MS . It should be understood that the shown mobile station in all of the enclosed figures, can be replaced by many mobile stations for example in a multicast or broadcasting scenario.

The enclosed figure 1 and 2 shows the LLC and GMM protocols in its correct environment within the GPRS. Figure 1 show the protocol stack used for payload (e.g., IP-packets) and Figure 2 shows the protocol stack involved when MS and SGSN wants to do signalling, including Short Message Service (SMS) .

With reference to the enclosed figure 3 it is shown a functional Mobility Management State Model. The state GMM machine that contains READY state is located in GMM layer in both SGSN and MS, as shown in fig. 3. The BSSGP layer at BSS adds cell position to all messages sent from MS to SGSN.

Figure 3 describes the following state transitions (quote from ref [3] ) :

Moving from IDLE to READY: - GPRS Attach: The MS requests access and a logical link to an SGSN is initiated. MM contexts are established at the MS and SGSN.

Moving from STANDBY to IDLE: Implicit Detach: The MM and PDP contexts in the SGSN shall return to IDLE and INACTIVE state. The MM and PDP contexts in the SGSN may be deleted. The GGSN PDP contexts shall be deleted.

Cancel Location: The SGSN receives a MAP Cancel Location message from the HLR, and removes the MM and PDP contexts. Moving from STANDBY to READY: PDU transmission: The MS sends a LLC PDU to the SGSN, possibly in response to a page.

PDU reception: The SGSN receives a LLC PDU from the MS.

Moving from READY to STANDBY: READY timer expiry: The MS and the SGSN MM contexts return to STANDBY state.

Force to STANDBY: The SGSN indicates an immediate return to STANDBY state before the READY timer expires.

Abnormal RLC condition: The SGSN MM context returns to STANDBY state in case of delivery problems on the radio interface or in case of irrecoverable disruption of a radio transmission.

Moving from READY to IDLE: GPRS Detach: The MS or the network requests that the MM contexts return to IDLE state and that the PDP contexts return to INACTIVE state. The SGSN may delete the MM and PDP contexts. The PDP contexts in the GGSN shall be deleted.

Cancel Location: The SGSN receives a MAP Cancel Location message from the HLR, and removes the MM and PDP contexts .

In the following is described a specific example of a sequence wherein disruption, due to expiration of the timer period, can cause a severe problem. Figure 4 shows the sequence as described in this specific example. References to Figure 4 are made when appropriate. The GPRS Mobility Management (GMM, also denoted as MM) in both SGSN and MS has a state machine which includes a READY State, see Figure 3. For GMM in the MS, the READY state is entered when an LLC-PDU has been sent to SGSN. For SGSN GMM, the READY state is entered when a LLC-PDU has been received from the MS, see Figure 3 above. When entering this READY state, the READY Timer T3314 is started in the SGSN according to Ref . [2] . The default value for READY Timer, T3314 is 44 second. If no new uplink LLC-PDU is received before expiry of the READY Timer, the READY state will be left (Fig. 4, arrow 5) . LLC UI frame is one type of LLC- PDU. The content of an LLC UI frame is either payload or signalling. If new LLC-PDU' s (e.g., payload) shall be sent to the MS when not being in READY state (Fig. 4, arrow 6), the SGSN will initiate the Paging procedure. SGSN orders BSS to page the MS (Fig. 4, arrow 6). When the MS detects the Paging signal on the air interface (Fig. 4, arrow 6) the MS will send an LLC-PDU to SGSN (Fig. 4, arrow 7) . The BSS will add the cell position to the message sent from the MS. The SGSN will 1) store the reported cell position, 2) enter READY state and 3) start READY Timer (Fig. 4, arrow 7) . The LLC-PDU that triggered the Paging is sent to the MS (Fig. 4, arrow 8) . The rationale behind this scheme is to ensure that MS is still able to receive the information sent from SGSN. The SGSN must tell BSS where the MS is located for all MS terminated traffic.

Note that during the time interval the READY timer is running (typically 44 seconds), the SGSN can send several thousands UI frames with payload to the MS without any response from the MS.

The above scheme has one major weakness. If the traffic flows only from SGSN to MS, and the application at the MS side does not have to send any response, and the MS does not change cell, the flow of payload to the MS is disturbed, each time the READY timer expires. The flow of payload will resume after a reception of the Cell Update, the response on the Paging request. If the MS changes radio cell when being in READY state, the MS has to initiate a Cell Update, i.e., send a LLC-PDU to SGSN which stores the new cell position. There are two variants of Cell Update: 1. The original Cell Update procedure as specified in the first GPRS release (R97) : If the MS changes radio cell when being in READY state, the MS has to initiate a Cell Update, i.e., send a LLC-PDU, i.e., an UI frame with no user data (empty) to SGSN which stores the new cell position, and restarts the READY timer.

2. An improved Cell Update procedure, called Cell Notification: If the MS changes radio cell when being in READY state, the MS has to initiate a Cell Notification, i.e., send a LLC-PDU, i.e. a U frame (not UI frame) with no user data (empty) to SGSN which stores the new cell position, but SGSN does not restart the READY timer. The reason for not resetting the READY timer is to avoid the GMM to be in READY state when only changes of cells are performed before expiry of READY timer. This is a problem in urban areas even when no payload is handled. For more information see Ref. [1] Section " 6. 4 . 1 . 7 NULL command" and Ref. [3], Section " 6. 9. 1 . 1 Cell Upda te Procedure " .

There are several known solutions to the problems described above regarding disruption of downlink traffic due to expiration of the READY timer, in the following section is given examples of these known solutions. 1. Applications running at MS side must regularly send uplink, UL, Dummy packets.

The application (s) running at the MS-side must ensure to send something at regular basis. The application must send some kind of response in due time for the GMM READY timer to expire, typically in due time before the typical expiration period of 44 second. This is a problem for, at least, the following two reasons:

a) The application must be modified to work well over the GPRS bearer service, that is every MS running applications in unacknowledged mode and where disruption is unwanted, have to be aware that GPRS bearer is used, so that the application can be adapted accordingly. This of course puts extra demands on the developers of new services.

b) The expiry time for the GMM READY timer might be PLMN specific, i.e., the application must be informed about the current setting of the READY timer value. I.e., the MS application and GMM in the MS must interact with each other, implying a dependency to get the application (s) to work well.

2. Set the READY timer to an infinitive value

Another solution is to change the timeout value for the READY timer to an infinitive value during the GPRS attach. This solution is stated in ref. [2], Section 10.5.7.3 "GPRS Timer" . If the timer length is set to all Is (binary) , then the READY timer function shall be deactivated, i.e., the timer no longer runs and the MS remains in READY state.

This will lead to higher frequency of Cell Update. Each time the MS changes Cell when being in READY state, a Cell Update must be performed. Frequent Cell Updates will lead to;

a) significant increase of MS battery consumption, due to increased signalling and time spent in, non-Discontinuous Reception mode, non-DRX mode, i.e. continuous reception mode. b) waste of radio resources; c) increase of Urn and Gb network load; These consequences are of course not desirable.

3. Reset of GMM timer in SGSN only.

Another solution is to restart READY timer due to handling of downlink, DL, traffic in both MS and SGSN. Problem: When using LLC unacknowledged mode, SGSN can not really know if the data was received by the MS or not, and the READY timers in SGSN and MS will then get out of synchronization. If the MS GMM state is not in READY, while SGSN GMM state still is in READY, there is a risk of sending MS terminating traffic to the wrong cell. The MS shall not perform cell update when not being in READY.

4. Using LLC acknowledge mode to transfer payload.

LLC acknowledged mode of operation will force the MS to send an acknowledgment for every received DL payload packet. Compared to the invention (using LLC unacknowledged mode) , this approach will require an allocated uplink radio resource in addition to the allocated downlink radio resource. I.e., bigger demand for UL, up-link, radio resources and more UL LLC ack. packets must be sent.

The above described problems have only been addressed toward GPRS mobile networks, however these problems will appear wherever one have; unacknowledged downlink traffic, a "time out" timer running at the transmitting end and/or at the receiving end and said transmitting end requests some kind of response from the receiving end for the resetting of said "time out" timer.

Summary Of the invention

It is an object of the present invention to provide a method avoiding the above described problems, further it is an object to provide such a method applicable not only to GPRS traffic but to all kind of, half duplex unacknowledged traffic, where the transmitter is requesting a response from the receiver (s) so as not to get a time out and hence a disruption in the traffic from the transmitter to the receiver .

The features defined in the independent claims enclosed characterize this method.

In particular, the present invention provides a method within telecommunication network for interruption free unidirectional communication between a sender (2) and one or more receivers (1), where the communicated traffic is of a unacknowledged type and the sender (2) and the one or more receivers (1) constitutes a run time timer that is started at initialization of a new traffic session, the traffic session will run uninterrupted while the timer (s) is/are running, and the timer (s) have/has a fixed or prechosen run time before time out, said time out will start a sender initiated procedure so as to restart the run time timer specified in that simultaneously or substantially simultaneously as the run time timer (s) has/have been initialized, the method further comprises the following steps:

- a flag is set to a first state at the sender (2) or at the one or more receivers (1),

- payload is transmitted from the sender (2), - the flag is set to a second state, different from the first state and

- a preset period, z, of time before expiration of the run time for the timer (s), and if the flag is in a second state, a restart procedure is initiated by the sender(2) or by the one or more receivers (1).

Brief Description of the drawings

In order to make the invention more readily understandable, the discussion that follows will refer to the accompanying drawing.

Figure 1 shows the transmission plane, including the LLC and GMM protocols within GPRS networks.

Figure 2 shows the signalling plane, MS <-> SGSN, including SMS.

Figure 3 shows functional Mobility Management State Model (from ref. [3]) for an MS and an SGSN.

Figure 4 shows DL traffic only as is known from the prior art interrupted by paging.

Figure 5 shows a first preferred embodiment of the present invention, where SGSN initiates XID negotiation prior to expiry of READY timer.

Figure 6 a second preferred embodiment according to the present invention, where the MS sends an empty LLC UI frame prior to expiry of the READY timer.

Figure 7 shows a third preferred embodiment of the present invention, where the MS initiates XID negotiation prior to expiry of READY timer. Detailed description of the invention

To solve the problems as addressed above, there is needed a method where unnecessary use of paging is avoided, further no unnecessary interrupts during downloading of files at one or more mobile station or other receiving party resulting in halting transfer of information. Hence a new method for restarting of the READY timers before expiration of a run time period can be one approximation to the problem. Based on this single idea of restarting of the timers before expiration of one or more READY timers running in ready mode and participating in the same session, is one basic solution with three approximations according to the present invention disclosed.

The basic solution is the introduction of a flag that can be set to a first certain state at the transmitting party or at the receiving side when the READY timer is started. This flag is set to an opposite state than the first state for each handled downlink package. Regarding the latter one can of course also start a subroutine that is testing the status of the flag for each handled downlink package thus avoiding the setting of the flag for each handled package. The choice of either running a test or setting the flag for each handled package is not important, as both solutions are revealing the same result; the latter however needs less software programming. A preset, or operator chosen period, before the expiration of the READY timer a action either from the one or more mobile stations (s) or from the transmitting party must be invoked as to restart the READY timer and thus prohibiting unnecessary paging. Choosing the mobile stations or the transmitting parties as the initiators of the needed action will not affect the result, and they are to be looked upon as merely two opposite solutions. However if the mobile station (s) is/are the initiator (s) , then each single mobile station participating in the said session must be adapted to this solution, thus a much more elaborating upgrade than having the transmitting party as the initiator.

The action can be either to start some kind of negotiation between the communicating parties participating in said session or it can be that a valid and empty payload frame is transmitted from the mobile station (s) to the transmitting party, in case of the latter the mobile station (s) will simultaneously or substantially simultaneously restart its READY timer (s) (run time timers) and simultaneously or substantially simultaneously set the flag to the first state.

If the negotiation solution is chosen the transmitting party or the mobile station (s) initiates a negotiation and the corresponding negotiation signalling is transmitted to either the transmitting party, if the mobile stations where the initiators, or to the mobile stations if the transmitting party where the initiator. In the latter case the mobile station (s) will transmit a first response to the invitation to negotiate and restart its/their READY timer (s), at the time of, or substantially at the time of reception of the first response from the mobile stations (s) will the transmitting party restart its timer and simultaneously or substantially simultaneously set the first flag to the first state.

In the first case where the restart procedure is initiated by the mobile station (s) the transmitting party will at the time of or substantially at the time of reception of the negotiation signalling originating from the mobile station (s) responds to the received negotiations signalling and simultaneously or substantially simultaneously restart its READY timer (run time timer) .

Where to implement the three different alternatives described above as sub solutions of the basic idea according to the present invention can be summarized as disclosed in the three following subsection:

• Method 1; this method must be implemented in SGSN, in case of operation within GPRS networks, for GSM, and all existing mobile station types will see the improvement (no regular disruption of downlink traffic). SGSN's supporting Method 1 will be perceived as better compared to SGSN's not supporting this method. This method can be described as the transmitting party initiated negotiation method.

• Method 2; is the method where the mobile station is sending a valid and empty payload frame. It must be implemented in the mobile station for GSM. Method 2 will help a mobile station vendor to offer good Push-To-Talk support even when the SGSN has not implemented Method 1 in case of GPRS communication.

• Method 3 must be implemented in the mobile station for GSM in case of GPRS sessions. This method can be described as the mobile station (s) initiated negotiations method. Very similar to Method 2, one more message must be sent, thus less optimal. Method 3 will help a MS vendor to offer good Push-To-Talk support even when the SGSN has not implemented Method 1.

It is enough to select only one of these methods, but Method 1 can inter work with Method 2, or Method 1 can inter work with Method 3.

In the following sections a more detailed description of the "non interruption method of half duplex mobile station terminated traffic" will be given with references to the accompanying figures as preferred embodiments, as well as a more comprehensive description of the advantages as achieved according to the present invention. Further examples of widening the scope of the invention will be given.

Advantages

No periodic disruption of downlink, DL, traffic. This is the case when 1) no change of radio cell occurs; 2) no uplink, UL, traffic is generated by the application on top of the GPRS bearer and 3) LLC unacknowledged mode of operation is used for payload. Applications at the MS do not have to bother about to send UL traffic other than required. No dummy application UL packets are required to keep the DL data to flow towards the MS. The solution makes the GPRS bearer to be even more transparent for the application.

The SGSN supporting Method 1 will be perceived as better from all its attached MS's (no matter of type) compared to a SGSN not supporting it.

Method 2 or 3 will help a MS vendor to offer good Push-To- Talk support even when the SGSN has not implemented Method 1.

Especially Conversational and Streaming QoS Traffic classes will benefit of using the proposed methods (less chance of disruption of the DL flow) , but also the Interactive and Background Traffic Classes will also see the same benefit. Broadening

Also for later releases of GPRS standards.

This invention is not tied to a specific 3GPP release of the standards. The references are made to Release 5 of the GPRS standards, but this invention is also applicable to earlier or later releases where LLC and GMM layers exist at the Gb-interface . In fact, it will be applicable wherever there is uni directional traffic between a transmitting party and one or more receiving parties, where the receiving parties communicates via radio links, and further there is one or more run time timers that are started at the initialization of a the session and if the run time timers at its expiration causes an interrupt in the session. Still further it must be possible to restart the mentioned timers so as to "virtually" start a new session.

The present invention is also applicable for generations of Mobile systems after GPRS.

GPRS for GSM is a 2.5^th generation of Mobile standards. This Patent Idea is also relevant for generations of Mobile systems after GPRS where equipment between MS and service provider are not allowed to send payload to the MS after a while due too old reported radio position of the MS.

A first preferred embodiment of the invention, SGSN takes action to provoke a MS to send an LLC PDU

Following is the first preferred embodiment according to the present invention, earlier in the present document also referred to as the method one. Figure 5 shows the sequence described here. References to Figure 5 are made when appropriate. The following example is a typical real life example taking into account parameter values for the timers etc. The SGSN has a flag per MS which is set to true each time a DL packet is handled. It should be noted, as described earlier, that it is not important whether the flag is set for each packet or if it is set for the first package and tested for in the following sequences. This flag is denoted as "Handled-DL" in figure 5. Z seconds before the Ready timer (per MS) in SGSN has expired and DL traffic has been sent after last start of the READY timer, SGSN will initiate an XID negotiation of a parameter, e.g., the maximum size of the LLC PDU used for GMM signalling (Fig. 5, arrow 3) . The SGSN will propose the same maximum value as before. A typical value for Z is 4 seconds. When the MS receives this request (Fig. 5, arrow 3), it has to respond either with accept or reject to the new value, see Ref [1], Section 6.4.1.6. Note that an XID negotiation can be interleaved into the flow of DL LLC frames containing payload (Fig. 5, arrow 3, 4 and 5). When the SGSN receives the response on the XID negotiation, the 1) current Radio Cell position is stored, 2) the READY timer is restarted and 3) the "Handled-DL" flag is set to false (Fig. 5, arrow 5) . In both cases, accept or reject of new value, the max size value is unchanged, and no functional change has been performed. The SGSN has achieved the intention to receive an updated cell position and prolong the time in READY state. Thus, a paging has been avoided and the ongoing MS terminated traffic Flow is not disturbed (Fig. 5, arrow 6 and 7) .

Note that during the time interval the READY timer is running (typically 44 seconds), the SGSN can send several thousands UI frames with payload to the MS without any response from the MS. A second preferred embodiment of the invention, a MS sends an empty LLC UI LLC frame before expiry of the READY timer

Following is the second preferred embodiments earlier referred to as the second method, further the description is accompanied by figure 6. This figure shows the sequence as described below. References to Figure 6 are made when appropriate .

The MS has flag which is set to true each time a DL packet is handled or set to true the first time a DL packet is handled and the next time a DL packet is handled a false/true test is performed. This flag is denoted as "Handled-DL" in Figure 6. Z seconds before the READY timer in the MS has expired, and DL traffic has been received after last start of the READY timer, the MS will send an empty LLC UI frame to SGSN (Fig. 6, arrow 4) . Typical value for Z will be 4 seconds. The current Radio Cell position will be added to the Cell Update by BSS. The READY timer will be restarted in SGSN upon reception of UL LLC PDU (Fig. 6 arrow 4) . Thus, a paging has been avoided and the ongoing MS terminated traffic flow is not disturbed.

Since an empty UI frame is sent (instead of empty U frame) , Method 2 will work even when Cell Notification procedure is agreed upon between SGSN and MS. Cell Notification procedure is the improved Cell Update procedure.

Note that during the time interval the READY timer is running (typically 44 seconds), the SGSN can send several thousands UI frames with payload to the MS without any response from the MS. A third preferred embodiment of the invention, a MS sends an XID negotiation before expiry of the READY timer

This is a variant of Method 2, referred to as method three, instead of sending empty LLC UI frame, an LLC U frame containing XID negotiation is sent from the MS. This will force SGSN to respond to the XID negation and thus send an unnecessary DL packet.

Figure 7 shows the sequence described here. References to Figure 7 are made when appropriate.

The MS has a flag per MS which is set to true each time a DL packet is handled or tests as described according to the two above mentioned embodiments may be performed regarding the flag status. This flag is denoted as "Handled-DL" in Figure 7. Z seconds before the READY timer in the MS has expired, and DL traffic has been received after last start of the READY timer, the MS will initiate an XID negotiation of e.g., the maximum size of the LLC PDU used for GMM signalling. The MS will propose the same maximum size as before (Fig. 7, arrow 4). Note that an XID negotiation can be interleaved into the flow of DL LLC frames containing payload (Fig. 7, arrows 3 to 7). When the SGSN receives the XID request; 1) the current Radio Cell position is stored and 2) the READY timer is restarted (Fig. 7, arrow 4). The SGSN will accept or reject the change and send it in a U frame back to the MS (Fig. 7, arrow 6) .

As before with the other proposed methods, the intention has been achieved; to inform the SGSN with an updated cell position and prolong the time in READY state. Thus, a paging has been avoided and the ongoing MS terminated traffic Flow is not disturbed.

Note that while in the foregoing, there has been provided a detailed description of particular embodiments of the present invention, it is to be understood that equivalents are to be included within the scope of the invention as claimed. In particular equivalents involving the use of status testing of the first flag instead of the setting of the flag for each downlink package as described in the dependent claims will be covered by the scope of the invention.

References

[1] 3GPP TS 44.064: "3rd Generation Partnership Project; Technical Specification Group Core Network; Mobile Station - Serving GPRS Support Node (MS-SGSN) ; Logical Link Control (LLC) layer specification; (Release 5), version 5.1.0, March 2002.

[2] 3GPP TS 24.008 "3rd Generation Partnership Project; Technical Specification Group Core Network; Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 6)", version 6.1.0, June 2003.

[3] 3GPP TS 23.060: "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS) ; Service Description; Stage 2, (Release 6)", version 6.1.0, June 2003.

Abbreviations and Terminology

BSS Base Station System

BSSGP BSS GPRS Protocol

Cell-Id Identifies uniquely a radio cell within a BSS

CPU Central Processing Unit

DL Downlink (direction : MS <- SGSNOGGSN )

DRX mode Ref 3GPP TS 23.060 V4.5.0 (2002 06) , (ref [3] in disclosure) 8.1.2 Discontinuous Reception A GSM MS may use discontinuous reception (DRX) or not. If using DRX, the MS shall also be able to specify other DRX parameters that indicate the delay for the network to send a page request or a channel assignment to the MS (see GSM 03.64). The DRX parameters shall be indicated by the MS in the attach procedure. The SGSN shall then send these parameters in each page request to the BSS that uses this information and the IMSI to calculate the correct paging group. DRX usage is independent of the MM states IDLE, STANDBY and READY. When a GPRS MS in READY state uses DRX, DRX has to be considered when assigning a packet data channel for downlink transfer. The SGSN shall therefore indicate the DRX parameters for the MS in all packet transmission

Claims

P a t e n t c l a i m s

1. A method within telecommunication network for interruption free unidirectional communication between a sender (2) and one or more receivers (1), where the communicated traffic is of a unacknowledged type and the sender (2) and the one or more receivers (1) constitutes a run time timer that is started at initialization of a new traffic session, the traffic session will run uninterrupted while the timer (s) is/are running, and the timer (s) have/has a fixed or prechosen run time before time out, said time out will start a sender initiated procedure so as to restart the run time timer c h a r a c t e r i z e d i n that simultaneously or substantially simultaneously as the run time timer (s) has/have been initialized, the method further comprises the following steps: a) . a flag is set to a first state at the sender (2) or at the one or more receivers (1), b) . payload is transmitted from the sender (2) to the one or more receivers (1) , c) . the flag is set to a second state, different from the first state for each handled payload packet alternatively the flag is set to a second state different from the first state for a first handling of a payload packet and for each payload packet following this first payload packet there will be a test of the status of the flag and d) . a preset period, z, of time before expiration of the run time for the timer (s), and if the flag is in a second state, a restart procedure is initiated by the sender (2) or by the one or more receivers (1) .

2. A method according to claim 1, c h a r a c t e r i z e d i n that the restart procedure is initiated by the sender (2) and comprises the following steps; a) the sender (2) initiates a negotiation and the corresponding negotiation signalling is transmitted to the one or more receivers (1), b) the one or more receivers (1) sends a first response to the negotiations and restarts its run time timer. c) at the time of, or substantially at the time of reception of the first response from the one or more receivers (1) will the sender (2) restart its timer and simultaneously or substantially simultaneously set the flag to the first state.

3. A method according to claim 1, c h a r a c t e r i z e d i n that the restart procedure is initiated by the one or more receivers (1) and comprises the following steps; a) a valid and empty payload frame is transmitted from the one or more receivers (1) to the sender (2), simultaneously or substantially simultaneously will the one or more receivers (1) restart its run time timer and simultaneously or substantially simultaneously set the flag to the first state, b) at the time of or substantially at the time of reception of the valid and empty payload frame from the one or more receivers (1) to the sender (2), will the sender (2) restart its run time timer for the corresponding receiver (1) .

4. A method according to claim 1, c h a r a c t e r i z e d i n that the restart procedure is initiated by the one or more receivers (1) and comprises the following steps; a) the one or more receivers (1) initiates a negotiation and the corresponding negotiation signalling is transmitted from the one or more receivers (1) to the sender (2), simultaneously or substantially simultaneously is the flag at the receivers (1) set to the first state and the run time timer at the receivers (l)is restarted, b) at the time of or substantially at the time of reception at the sender (2) of the negotiation signalling originating from the one or more receivers (1) will the sender (2) respond to the received negotiations signalling and simultaneously or substantially simultaneously restart its run time timer.

5. A method according to any of the previous claims, c h a r a c t e r i z e d i n that the communication between the sender (2) and the one or more receivers (1) is over a GPRS bearer.

6. A method according to claim 5, c h a r a c t e r i z e d i n that the sender (2) is a combination of an SGSN (2) and a BSS (2), where the SGSN (2) is a node that is initialising payload traffic in the downlink direction whereas BSS (2) is the base station node physically transmitting payload traffic over the air to the one or more receivers (1) .

7 A method according to claim 1 and 5 or 6, c h a r a c t e r i z e d i n that the run time timer at the one or more receivers (1) and at the sender (2) is a READY timer (3) .

8. A method according to claim 1 and 5-7, c h a r a c t e r i z e d i n that at the initialization of a of a new traffic session will a GMM enter a READY state at the one or more receivers (1) and at the sender, simultaneously or substantially simultaneously will the

READY timer at the one or more receivers and at the sender be started.

9. A method according to claim 8, c h a r a c t e r i z e d i n that the flag is a flag indicating handling of downlink traffic, and said first state of the flag is false and said second state of the flag is true.

10. A method according to any of the claims 2, 4-9, c h a r a c t e r i z e d i n that the negotiations are XID negotiations.

11 A method according to any of the claims 2, 4-10, c h a r a c t e r i z e d i n that the sender or one or more receivers Z seconds before the READY timer has expired will initiate said XID negotiation of a maximum size of a LLC PDU used for GMM signalling, the initiator will propose to use the same maximum size of a LLC PDU as previous agreed upon.

12. A method according to any of the claims 3, 5-9, c h a r a c t e r i z e d i n that the valid and empty payload frame is an empty LLC UI frame.

13. A method according to any of the claims 1 and 11, c h a r a c t e r i z e d i n that the parameter Z is preferably set to between 1 and 10 seconds.

14 A method according to claim 11, c h a r a c t e r i z e d i n that the parameter Z is set to approximately 4 seconds.