Wireless data communications for packet data communication

[0001] The invention relates to data communication, especially packet data communication via a wireless interface between a mobile device and an access network in a communication system.

Background of the invention [0002] A communication system is an object enabling communication between at least two entities, such as user equipment and / or network units or other nodes associated with the communication system. The communication system may include, for example, communication of various types of data, such as voice data, e-mail (e-mail), text messages, multimedia etc. A communication system can be used to provide its user with various types of services.

[0003] A communication system typically operates according to a given standard or specification that defines what activities various system components can perform and how this should be achieved. For example, a standard or specification can define whether the user, and more specifically, has the switched circuit service provided by the user, switched package service, or both. Typically, communication protocols and / or parameters are also defined that must be used. For example, the manner in which communication is to be implemented between user equipment and communication network elements is usually based on a previously defined communication protocol. In other words, you need to define a specific set of "principles" on which communication can be based so that user equipment communicates through a communication system.

[0004] Communication can be provided via fixed link and / or wireless interfaces. A feature of the data communication system in which data is transported to the user's equipment via wireless interfaces is their ability to provide mobility to their users. By this, wireless systems can also be called mobile communication systems. Examples of communication systems that provide wireless communication include a public land mobile communications network (PLMN), communication systems based on satellite communications, and wireless data networks such as a local wireless data network (WLAN).

[0005] Wireless communication systems may be provided based on radio access units, called cells. Hence, these systems are often called cellular communication systems. In a cellular system, the transceiver base station (BTS) radio access network (RAN) provides a wireless communication unit that supports mobile devices, such as mobile stations (MS) or similar mobile user equipment (UE) via an air or radio interface within range of an area

- 2 cells. It should be noted that the name of the station may differ between different communication systems. For example, names such as base station and Node B nodes may be used to refer to a communication system station. In the context of wireless local area networks, stations may be called access points. The shape and size of the cells may vary between them. You can also group several cells together to create larger service areas. A base station can provide more than one cell.

[0006] Examples of cellular communication systems include standards such as global mobile communication system (GSM) and various GSM-based systems (such as universal mobile packet transmission service - GPRS), American mobile communication system (AMPS), digital AMPS (DAMPS) , broadband multi-access code division (WCDMA), multi-access time division / multi-access code division (TDMA / CDMA) in the universal mobile telecommunications system (UMTS), CDMA2000, i-Phone etc.

[0007] In third generation systems such as CDMA2000 or UMTS, mobile devices can establish a continuous connection over a radio access network (RAN) and a backbone network (CN) of the cellular system. For example, a continuous connection may be established by an access network controller such as a base station controller (BSC) or packet control function (PCF) of a radio access network (RAN) and a core network access gateway. The access gateway and access network controller can then manage the context files of mobile devices and stop the context files for connection continuity.

[0008] If the mobile device is turned off or otherwise prevented from communicating with the access network, the connection is lost and it will need to be renewed when the mobile device is turned on again or when the reason for communication blocking is removed. After the access gateway and access network controller determine that the mobile device has been turned off or out of range for another reason, the mobile device context files are usually deleted.

[0009] It may happen that the mobile device is not intentionally disconnected but will go out of range or be at a dead end in the coverage area. This may result, for example, from the fact that the user enters a tall building, into the tunnel, goes out of the cell, etc. If this happens, the mobile device may temporarily be unable to respond to requests or other messages from the access gateway or access network controller. When the mobile device is back in the radio range again, it must rebuild the context file in the access network controller and access gateway. This can cause additional and unwanted signaling over the radio link. In addition to causing a load on the radio link, additional signaling can also reduce the battery life of the mobile device.

[0010] For example, it has been proposed in CDMA2000 that support for always-on mobile devices must be a mandatory feature of an access gateway. An access gateway can be provided through a packet data service (PDSN) node. In the "always on" proposal, the service manages the subscriber's packet data session on the local network. In short, the access gateway is always on and is organized so that it does not initiate a release

- 3 packet data sessions until you are sure that the mobile device is no longer reachable.

[0011] Currently two types of services are proposed, a mobile IP service or a simple IP service. The main difference between the mobile IP service and the simple IP service is the way in which mobility detection management is supported. In the simple IP service, the packet data service is interrupted when the mobile device moves to another access gateway or attachment point. The mobile IP service tries to avoid any interruptions in the service in such cases.

[0012] Proposition No. TR45.6 / 2002.08.05.10r1 of August 2002 for the Subcommittee Adjunct Wireless Packet Data Standards subcommittee of the TIA (Telecommunications Industry Association), entitled "Proposed Resolution to Battery Life and Reachability issues in PN-3-4732- RV2-A (Research In Motion Ballot comment # 1) "by Dan Willey and Willy Verbestel deals with these issues. The proposal discloses a method for a packet data service (PDSN) node or access gateway to perform an operation known as a connection control protocol (LCP) echo request layer-point-to-point protocol (PPP). (Those interested can find a more detailed description of the echo request message in the IETF RFC 1661 document of the Internet Engineering Task Force.) In a communications system controlled according to the protocol, the mobile device responds at a specified time to the LCP echo request message, LCP protocol echo reply message PDSN can maintain a configurable timer for the maximum allowed echo response time and echo request retry counter. After entering the state of the open Internet Protocol Control Protocol (IPCP) on a point-to-point (PPP) session configured for an always-on device, PDSN can also start the PPP inactivity clock for a given PPP session. After the PPP inactivity clock has expired, PDSN sends an LCP echo request message through the main service instance and starts the clock for the maximum allowed echo response time for a given PPP session. PDSN can also initialize the counter echo request retry counter to the configurable integer value. The system is such that if, after the maximum echo response time clock has expired, the value of the echo retry request retry counter is greater than zero, PDSN sends the LCP echo request message, reduces by one value the echo retry retry counter and starts the maximum allowed echo response time counter .

[0014] For the simple IP service, the proposal is that the mobile station must be informed of the PPP inactivity clock value.

[0015] After receiving the LCP echo reply message for a given PPP session, PDSN stops the clock of the maximum allowed echo response time, sets the echo request retry counter again, and restarts the PPP inactivity clock. After the maximum allowed echo response time has expired, and the echo request retry count value is zero, PDSN releases the PPP session. PDSN

- 4 can only delete PPP after the PPP inactivity clock has expired. However, if the mobile device is out of radio range long enough, the network will slow down the packet data session. Hence, the mobile device will still need to restart the packet data session.

[0016] In addition, in order to extend the battery life of devices always on and to avoid losing air interface performance, the proposal suggests for devices always on using a two-hour PPP inactivity clock value.

[0017] The above described operation may result in a significant amount of signaling and a loss of resources. And still the current CDMA2000 wireless IP network and the radio access network are not satisfactorily providing "always on" services when the mobile station is temporarily out of range. The proposal only offers limited help for simple IP services.

[0018] The requirement to never pick PPPs may also violate approved CDMA2000 specifications. PDSN must comply with any RAN requests to free resources using cleanup procedures. In addition, the current project of retrying the echo request is in the form of a configurable value. This value can be set relatively high to ensure session retention. The disadvantage is that RAN and PDSN resources are allocated unnecessarily. In addition, the proposal requires implementation of a trigger and clock logic in the mobile station.

[0019] Document WO02 / 47404 describes a technique that triggers a new session or handover procedure for a mobile station in a communication network with a switched data packet network connected to a wireless network.

Document WO02 / 056564 describes a communication system comprising a network resource manager (NRM) for monitoring and / or controlling resources in an IP network. In contrast, 3GPP2, S.R00370, pages 1-46 mentions the use of the packet control function to communicate with PDSN to support sleep relaying.

Summary of the Invention [0020] Embodiments of the invention aim to overcome at least one of the above problems.

[0021] The invention provides a method according to claim 1 and a device according to claim

10.

[0022] Embodiments of the invention may provide various advantages. The embodiments allow for proper protection of an ongoing packet data session between the backbone unit and the mobile device in the event that the wireless connection is temporarily lost. The number of signaling can be limited. For example, in the detailed embodiments disclosed below, the amount of signaling and radio resource utilization between the core data packet data service node and the mobile station, base station controller or packet control function, and the digital telephone exchange (MSC) can be significantly reduced or completely eliminated. The power consumption of a mobile device can be reduced, thus reducing battery consumption

- 5 and extend its life. In specific embodiments, accurate accounting data can be provided because the core network node does not need to count packets sent to the radio access network. Some of the embodiments may result in limited service interruptions in the embodiments of packet data services.

Brief Description of the Drawings [0023] For a better understanding of the invention, embodiments of the invention have been described with reference to the accompanying drawings, in which:

Figure 1 shows a communication system according to the invention;

Figure 2 is a block diagram showing an embodiment of the invention;

Figure 3 is a block diagram showing another embodiment of the invention;

Figure 4 schematically shows a particular embodiment of the invention and Figure 5 shows a further embodiment of the invention.

Description of preferred embodiments of the invention [0024] Before discussing the preferred embodiments of the invention in more detail, reference will be made to Figure 1, which is a simplified representation of parts of a representative cellular system. In particular, Figure 1 shows some of the elements of the radio access network (RAN) 9 and the representative backbone network (CN) 19 of the cellular system.

[0025] In the arrangement shown, three base stations 4, 5 and 6 provide three access units or cells 1 to 3 of the cellular telecommunications network. The cells are controlled by the controller unit 10. Hereinafter, this unit will be called the base station controller. These units belong to the radio access network 9.

[0026] It should be noted that the diagram shown in Fig. 2 is very schematic and in practical implementations the number of base stations will be much larger. One cell may include at least one location of the base station. The base station device or location may also provide at least one cell. The radio access network can also include only one cell. These features depend on the implementation and circumstances.

[0027] Each base station 4 to 6 is adapted to transmit signals (downlink) through the wireless interface and receive signals (uplink) of the mobile user's mobile device 7. The mobile user may use any appropriate mobile device adapted to the Internet (IP) protocol or other packet data communication over the network. For example, a mobile user can access the mobile network using a personal computer (PC), handheld computer (PDA), mobile station (MS), etc. The following examples are presented in the context of mobile stations.

[0028] The skilled person has knowledge of the functions and operation of a typical mobile station. Hence, it is sufficient to note that the user can use the mobile station 7 for tasks such as, but not limited to, making and receiving phone calls, receiving and sending data from and to the network, and experiencing, for example, multimedia content. The mobile station may include an antenna element (not shown for clarity) for wireless reception and transmission of signals from and to base stations of the mobile communication network. The mobile station 7 can also be equipped with a screen for displaying to the user of the mobile user equipment images or other graphic information. Speakers are usually also provided. The operation of the mobile user equipment can be controlled by means of a proper user interface, such as control buttons, voice commands, etc. In addition, the mobile user equipment is supplied with a processor unit and memory means.

[0029] The mobile station 7 is able to transmit signals on the uplink via the wireless interface and receive signals on the downlink from the base stations. It should be noted that although only one base station is shown in Figure 1 for clarity, multiple mobile stations can communicate with each base station simultaneously.

[0030] The radio access network 11 is controlled by the appropriate controller 10. The controller 10 can be provided by any appropriate controller. A controller can be provided for each base station or the controller can control multiple base stations. Solutions are also known in which controllers are provided both for individual base stations and at the radio access network level to control multiple base stations. It should be noted that the name, location and number of radio access network controllers depend on the system. For example, the UMTS terrestrial radio access network (UTRAN) uses a controller node, which is called a radio network controller (RNC). In GSM and CDMA2000 networks, the radio network controller unit can be provided by the base station controller (BSC). In Fig. 1, possible radio network controllers are indicated by the controller unit 10.

[0031] Backbone network (CN) units typically include various switching elements and gates enabling communication through multiple radio access networks as well as for coupling one cellular system with another communication system, such as but not limited to other cellular systems and / or fixed systems communication lines. The controller unit 10 assigned to the radio access network may be connected to any appropriate backbone network element via the appropriate interface and / or gate system.

[0032] Element 12 in Fig. 1 may include a packet control function (PCF) provided between the radio access network 9 and the core gateway access gateway 19. In Fig. 1, the access gateway is provided by means of node data packet services (PDSN) 14 .

[0033] Fig. 1 also shows a service provider unit 16. The unit 16 creates a possible source of packet data to be sent to the mobile station 7 via the backbone network 19 and the radio access network 9 of the communication system. Service provider entity 16 should be understood

- 7 as any unit that can deliver content or other data to a mobile station. The service provider entity 16 may include a server and / or other data processing means. The service provider entity 16 may also be only a node in an Internet Protocol (IP) network. The service provider entity may operate and be served by an external service provider or communications network operator. It should be noted that the service provider's entity does not have to form the necessary element of the invention and is therefore not described in detail.

[0034] The mobile telecommunications network provides its users with mobility. In other words, a mobile device such as mobile station 7 can move from the coverage area of ​​one cell to the coverage area of ​​another cell. The position of the mobile station 7 can therefore change over time, since the mobile station can move freely from one location (the range of the base station or cell) to another position (to another cell), as well as within a single cell.

[0035] From here, the mobile station 7 may temporarily move to a position where the wireless interface is blocked or where the mobile station and the appropriate base station cannot otherwise communicate with each other via the wireless interface. It is then assumed that such a mobile station is out of range. In fig. 1 this situation of temporary out of range occurs when the mobile station 7 moves to a position where signals from base station 6 are blocked by building 8.

[0036] In a first embodiment of the invention, a mechanism for monitoring requests and other messages from the gateway node is implemented in the controller associated with the radio access network. Other messages may be any messages requiring a response from base station 7 to maintain a packet data connection. In Fig. 1, the controller providing the monitoring mechanism 11 is implemented in the controller unit 10.

[0037] The monitoring mechanism 11 can also be used to monitor at least one parameter associated with the wireless interface between the radio access network and the mobile station 7. When the parameter meets the predefined condition, the monitoring mechanism may send a message to the backbone network. The message may be sent as a response to the backbone message or the message may be a notification regarding the state of the wireless interface between the mobile station 7 and the access network 9.

[0038] The following is an operation according to an embodiment with reference to the block diagram of Fig. 2. In a preferred embodiment, the monitoring mechanism monitors the signal strength transmitted on the uplink from the mobile station to the base station according to the packet data communication interface set up. More specifically, the signal strength of the link layer frames continuously transmitted by the mobile station 7 can be measured and monitored by the monitoring function 11 of the radio access network (RAN) 9.

[0039] A certain threshold value can be assigned to the signal strength. If the monitoring function detects that the signal strength drops below the threshold value, the monitoring function 11 can determine if the mobile station 7 has fallen out of range and therefore there is no longer a proper communication interface with the base station 6. The monitoring function 11 can then respond to the requests of the backbone network to the mobile station 7 to prevent the backbone network from breaking the packet data connection.

[0040] The monitoring function 11 can continue monitoring until the decision is made that the connection is in any case broken. This may be based on a local principle. For example, the rules for this can be configured at the access network level or for a group of access networks covering a specific area. The decision on whether to break the connection can be based on any appropriate criterion. For example, the decision may be based on clock or subscriber profile information, service type, quality of service, etc.

[0041] If the monitoring shows that the mobile station is again reachable, in other words it will return to the base station's radio coverage area, all unsent data can be sent to the mobile station via the radio access network. Unsent data from the service provider can be buffered at node 14 of the packet data service, for example at its buffer 13. Packet data communication can then continue as before. The decision on whether to cache or drop packets can also be based on a local principle.

[0042] According to Fig. 3, the monitoring function 11 may send notifications to the node in the backbone network 19 that the mobile station 7 is not available. The notification can be sent as an alternative to sending a response to the mobile station. Notifications can also be sent in addition to sending responses to backbone messages.

[0043] In Fig. 1, the monitoring mechanism 11 is provided in the base station controller 10. The monitoring mechanism can also be provided at any other node assigned to the radio access network. For example, a monitoring function may be provided in the packet control function (PCF) 12.

[0044] In the above example, the monitored condition is related to signal strength. It is also possible to monitor other conditions. For example, a failed paging of a mobile station may trigger similar actions as above until the mobile station responds to a paging attempt. In another example, the base station requests the mobile station to re-register at specific intervals. If the mobile station does not register again after the interval has expired, it can be concluded that the mobile station is unreachable. Information from the detected pilot signals from a mobile station can also be used to determine the quality of the wireless interface between the mobile station and the base station.

[0045] It is possible to associate a clock with backbone messages. If the mobile station does not respond before the clock has expired, for example by indicating disconnection or transferring the connection, the access network node will respond to the mobile station.

[0046] As an option, the monitoring mechanism 11 monitors the clock in the access network that is activated when a message for the mobile station, such as a request, comes from the backbone. A clock may be provided for the specified period to expire before the core network request has expired. If the mobile station does not send any signals that could indicate disconnection or transfer of the connection, the monitoring mechanism may then send a response just before the request expires and thus prevent the loss of the established communication interface.

[0047] A combination of conditions may also be used. For example, the above disclosed response mechanism may be triggered if at least one possible condition indicates wireless interface quality problems. Triggering can occur if at least two conditions meet the criteria, etc.

[0048] In some communication systems, the controller providing the monitoring mechanism according to the radio access network may not be able to respond to the mobile station to backbone network messages. This can occur, for example, when the monitoring mechanism may require a PPP stack and link state message knowledge before it can send a response. In such cases, the monitoring mechanism can respond to messages from the backbone by sending information that the mobile station cannot be reached. The sending of such notification is shown in Figure 3.

[0049] The information regarding the state of the mobile station may be, for example, a simple out of range indicator or other indicator informing the backbone network that the mobile station cannot be reached. These indicators can be selected to take only two values, such as binary values ​​zero or one. Examples of the use of such indicators are shown in Fig. 4 and Fig. 5.

[0050] Hereinafter, the specific embodiment shown in general in Fig. 3 and with reference to Fig. 4 is detailed. In accordance with the above explanation, it has been proposed that to determine whether a mobile station (MS) can be achieved, node data packet data service 14 may perform operations known as the connection control protocol (LCP) link layer echo request (LCP) message. According to the protocol, after receiving the LCP protocol echo request message, the mobile station must respond with an LCP protocol echo response.

[0051] To implement the above, the packet data service node 14 may manage the configurable timer 20 of the maximum allowed echo response time and the counter 22 attempts of the echo request. After entering the open state of the Internet Protocol Control Protocol (IPCP) on a point-to-point protocol (PPP) session configured for an always-on service, node 14 of the packet data service can start the PPP inactivity clock 24 for the PPP session. After the PPP inactivity clock has expired, the node

- packet data services may send to the mobile station 7 an LCP echo request message and / or may activate a clock 20 of the maximum allowed echo response time for a given PPP session. The node 14 packet data service may also initialize the counter 22 echo request retries with a configurable integer value.

[0052] The system is such that after the clock 20 of the maximum allowable echo response time has expired, when the value of the echo request retry counter 22 is greater than zero, the node 14 of the packet data service must send the LCP echo request message, reduce by one retry counter echo requests and run the clock for the maximum allowed echo response time. After receiving the LCP echo reply message for a given PPP session, node 14 of the packet data service must stop the clock 20 of the maximum allowed echo response time, reset the counter 22 attempts of the echo request again and restart the inactivity clock 24. After the maximum allowable echo response time has expired when the value of the echo request retry counter is zero, node data packet data service 14 may free the PPP session.

[0053] In the embodiment shown in Fig. 4, the node associated with the radio access network is adapted to respond to the message by sending an out of coverage indicator 30 to the backbone if it is determined by the monitoring function 11 that the mobile station 7 cannot be reached. After the indicator has been received, the 22 retry counter can be reset and / or the clock (s) can be restarted. Thanks to this, you can also avoid breaking the connection.

[0054] According to another embodiment, shown in Fig. 5, the out of range indicator is sent from the radio access network (RAN) to PDSN 14 in response to the detection that the mobile station 7 is out of range. The pointer may be used by an access gateway, e.g., node data packet data service 14, to determine when not to send messages (e.g., echo messages) or send data received from the service provider entity 16 to the access network (RAN). The RAN can cancel blocking by sending another pointer to the backbone.

[0055] The arrangement may be such that, for example, core network node 14 may normally send data to the radio access network if the indicator value is 0. However, if the indicator value changes to 1, the core network node may be prevented from sending any data to radio access networks.

[0056] Accordingly, the monitoring mechanism determines the state of the wireless interface between the radio access network and the mobile station after receiving a data message from the backbone. Based on this status, the monitoring mechanism can respond to data messages with an out of range indicator. If the indicator is negative (i.e. the mobile station is out of range), then the backbone may decide not to send any further data until a positive indicator is received.

[0057] It should be noted that although specific embodiments of the invention have been described with reference to mobile stations, many embodiments of the invention can be applied to any other appropriate user equipment.

[0058] An embodiment of the invention has been described in the context of the CDMA2000 system. The invention can also be applied to all other communication standards and access techniques, including broadband code division multiple access, frequency division multiple access, time division multiple access and spatial division multiple access, as well as their hybrids.

[0059] It should also be noted that base stations on different systems may have different names, for example Node B or access point. In addition, the term radio access network is intended to include a group of cells in cases where more than one cell is controlled by a controller unit. The radio network controller of the above examples can be replaced by any suitable access network controller, such as a WLAN access network controller.

[0060] It should also be noted here that although illustrative preferred embodiments of the invention have been described above, there are many variations and modifications that can be made to the disclosed solution without departing from the scope of the invention in accordance with the appended claims.

Prepared and verified

Grażyna Palka Patent Attorney