Method to detect a User Equipment stuck on a dedicated channel

FIELD OF THE INVENTION [0001] This invention relates in general to communication networks. More specifically, the invention relates to the release of a User Equipment (UE) stuck on a dedicated channel.

BACKGROUND OF THE INVENTION [0002] Existing wireless communication systems include a User Equipment (UE), a Radio Access Network (RAN), and a Core Network (CN). The UE maybe connected to the CN through a dedicated channel. The dedicated channel may be used for operations including circuit-switched voice transfer, packet-switched voice transfer or data transfer. In the Wideband Code Division Multiple Access (WCDMA) network, CELL-DCH state refers to the state in which the UE is engaged in the dedicated channel. In the Global System for Mobile Communications (GSM) network, the

Traffic Channel (TCH) state refers to the state in which the UE is on a dedicated channel. The GSM network uses the TCH channel for the transfer of voice, circuitswitched data and circuit-switched related signaling.

[0003] While it is engaged in a dedicated channel, however, a UE may get stuck on the dedicated channel. This may happen due to an error or a fault in at least one UE,

RAN and CN. When the UE is stuck on the dedicated channel, the UE and the RAN keep performing actions that are necessary to maintain the channel. For the WCDMA Radio Access Technology (RAT), the actions include UEs sending MEASUREMENT

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REPORT messages and RANs sending MEASUREMENT CONTROL messages and ACTIVE SET UPDATE messages on the relevant Radio Bearers (RBs). In spite of the UE and the RAN performing the necessary actions, no useful data is exchanged between the UE and the CN for a significant period of time. In other words, there is no higher layer signaling and no data transfer over non-signaling RBs carrying user data or voice.

[0004] When stuck on the dedicated channel, the UE can suffer from several problems. First, battery consumption is high in a UE stuck on the dedicated channel. The dedicated channel is the highest battery consumption mode for the UE. In the dedicated channel, the UE continually monitors the downlink and transmits on the uplink. Second, this situation also results in the wastage of network resources. Maintaining a dedicated channel for the UE requires a significant amount of RAN resources and bandwidth. When the UE is stuck on the dedicated channel, these RAN resources and bandwidth are wasted, without any useful data being exchanged.

BRIEF DESCRIPTION OF THE DRAWINGS [0005] The present invention is illustrated by way of example and not limitation in the accompanying figures, in which like references indicate similar elements, and in which:

[0006] FIG. 1 shows a block diagram illustrating an exemplary wireless communication system, in accordance with an embodiment.

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PCT/US2006/020805 [0007] FIG. 2 shows a flowchart illustrating steps involved in utilizing the resources of a User Equipment (UE) stuck on a dedicated channel, and of the corresponding network, in accordance with an embodiment.

[0008] FIG. 3 shows a flowchart illustrating steps involved in determining whether the UE is stuck on a dedicated channel, in accordance with an embodiment.

[0009] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS [0010] Various embodiments of the present invention provide a method and a computer program product for resource utilization in a User Equipment (UE). When engaged in a dedicated channel, the UE may get stuck on it. The method and the computer program product detects whether the UE is stuck on the dedicated channel. When it is detected that the UE is stuck on the channel, either the UE or the corresponding network carries out a release of the UE from the dedicated channel. This is done by performing a local release of the dedicated channel’s radio resources alone or through executing a fatal error routine.

[0011] Before describing in detail the method of detecting and releasing a User Equipment stuck on a dedicated channel, it should be observed that the method can be implemented using software and/or circuitry in combination with conventional UE

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PCT/US2006/020805 software and hardware. Accordingly, the method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0012] FIG. 1 shows a block diagram illustrating an exemplary wireless communication system 100, in accordance with an embodiment. The wireless communication system 100 includes a User Equipment (UE) 102, a Radio Access Network (RAN) 104, and a Core Network (CN) 106. The UE 102 is sometimes also referred to as a Mobile Station (MS). Examples of the UE 102 include a cellular phone, a laptop computer, a Personal Digital Assistant (PDA), and so forth. The wireless communication system 100 may include a plurality of UEs. In this description, the wireless communication system 100 only shows a single UE 102.

[0013] The UE 102 manages communications links with the CN 106 through the RAN 104. The RAN 104 includes base stations 108 and 110. The base stations 108 and 110 are wireless transmitting and receiving stations for the wireless communication system 100. The CN 106 further manages communications links between the UE 102, and fixed or mobile communication networks. Examples of fixed networks include a public-switched telephone network (PSTN), an Integrated Services Digital Network (ISDN), and the Internet. An example of a mobile network is a Public Land Mobile Network (PLMN).

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PCT/US2006/020805 [0014] FIG. 2 shows a flowchart 200 illustrating steps involved in utilizing the resources of a User Equipment (UE) stuck on a dedicated channel, and of the corresponding network, in accordance with an embodiment. Step 202 determines whether the UE 102 is stuck on the dedicated channel. In one embodiment, the dedicated channel is accessed in a Wideband Code Division Multiple Access (WCDMA) network while the UE is in a CELL_DCH state. In another embodiment, the UE 102 is engaged in a dedicated channel while in a Traffic Channel (TCH) state in the GSM network.

[0015] The UE 102 may get stuck on the dedicated channel while performing the General Packet Radio Service (GPRS) attach operation on WCDMA network. The UE 102 may set the ‘follow on request flag’ in the GPRS Attach message, which it sends to the CN106 to indicate that it has additional data to send after the attach operation is complete. The UE 102 may then fail to send any additional data afterwards. If this occurs, the UE 102 may get stuck on the dedicated channel.

[0016] The UE 102 may also get stuck on the dedicated channel in WCDMA after failing to release a Circuit Switch (CS) signalling connection, once the transactions associated with the CS signalling connection are complete. Similarly in WCDMA, the UE 102 may get stuck on the dedicated channel after failing to release a Packet Switch (PS) signalling connection once the transactions associated with the PS signalling connection are complete.

[0017] Finally, the UE 102 may get stuck on the dedicated channel if the corresponding WCDMA network fails to release a Radio Resource Control (RRC)

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PCT/US2006/020805 connection once all signalling connections have been successfully released. Similarly, the UE 102 may get stuck on the dedicated channel if the corresponding GSM network fails to release a Radio Resource (RR) connection once all signalling connections have been successfully released. In addition to these specific examples, there may be other situations that present a risk of the UE 102 getting stuck on the dedicated channel.

[0018] In an embodiment, the UE 102 performs the step 202. In another embodiment, the RAN 104 triggers the UE to perform step 202. The RAN 104 may trigger the UE 102 to perform step 202 by broadcasting a message (which indicates that the check described in step 202 should be performed while the UE 102 is on the dedicated channel) to all, or a select group of UEs, in its coverage area. The trigger message may be sent as a system information message or as a device-specific message to individual UEs in its coverage area. In yet another embodiment, the RAN 104 performs the step 202 on its own, in which case no trigger needs to be sent to the UE.

[0019] Step 204 performs a local release of the radio resources when it is determined that the UE 102 is stuck on a dedicated channel. In one embodiment, the UE 102 performs the local release of the RRC connection. In another embodiment, a corresponding RAN 104 of the UE 102 performs the local release of the RRC connection. When the UE 102 performs a local release of the RRC connection, the release may be controlled by a Non Volatile Memory (NVM) field.

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PCT/US2006/020805 [0020] The NVM is a type of memoiy that retains its data even when the UE is switched off. Examples of NVM include Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM). The UE 102 performs the local release of the RRC connection based on a pre-defined value of a field in the NVM. If the field in the NVM contains a predefined first value is, for example, a 0 bit, then the local release of the RRC connection will be performed with little notice to the user of the UE. (Note that “first” is used solely to distinguish this value from another value introduced in the next paragraph).

[0021] If the field in the NVM contains a pre-defined second value, for example, a 1 bit, then the local release of the RRC connection will be performed according to a fatal error routine. A fatal error routine generally saves information regarding a failure of the UE (e.g., that the UE performed a local release due to a determination of being stuck on a dedicated channel, the time and date of the failure, etc.), forwards failure information to a remote server for analysis, and notifies the user of the UE (e.g., a tester) of the failure. The field of the NVM often contains a pre-defined second value when the UE is undergoing field testing, while the field of the NVM would often contain a pre-defined first value when the UE is a released product.

[0022] At step 206, after the RRC is released, the UE 102 is placed in an idle mode.

[0023] FIG. 3 shows a flowchart 300 illustrating steps involved in determining whether the UE 102 is stuck on a dedicated channel, in accordance with an

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PCT/US2006/020805 embodiment. This flowchart 300 provides details for implementing step 202 shown in FIG. 2.

[0024] At step 302, a timer is started. Step 304, determines whether the UE 102 is sending or receiving higher layer signaling messages. Examples of higher layer signaling messages for both the WCDMA and GSM networks include signaling performed by the Mobility Management (MM), General Packet Radio Service Mobility Management (GMM), Call Control (CC), Supplementary Services (SS), Short Message Service (SMS), and Session Management (SM) layers.

[0025] In a WCDMA implementation, WCDMA higher layer signaling messages are sent and received over a Signaling Radio Bearer 3 and a Signaling Radio Bearer 4. If the UE 102 is sending or receiving at least one of the higher layer signaling messages, then the flow returns to step 302. If the UE 102 is not sending or receiving any higher layer signaling messages, then the flow continues to step 306.

[0026] Step 306 determines whether the UE 102 is sending or receiving user data over non-signaling Radio Bearers (RBs). If the UE 102 is sending or receiving user data over non-signaling RBs, then the flow returns to step 302. If the UE 102 is not sending or receiving user data over non-signaling Radio Bearers (RBs), then the flow continues to step 308. Step 308 determines whether the UE 102 is sending or receiving signals over a voice RB. If the UE 102 is sending or receiving signals over a voice RB, then the flow returns to step 302. If the UE 102 is not sending or receiving signals over the voice RB, then the flow continues to step 310.

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PCT/US2006/020805 [0027] Step 310 determines whether a DCH Loopback Mode is active. The DCH Loopback Mode is a WCDMA test mode in UEs. A similar test mode is available for GSM networks and UEs. UEs with the test mode enabled on their Subscriber Identity Module (SIM) can be commanded to enter the DCH Loopback Mode by the corresponding network. The corresponding network commands the UE 102 to enter the DCH Loopback Mode through MM messages. The MM messages indicate when a test RB is to be activated, and also when the actual loopback of data sent on the test RB is to be enabled. When the DCH Loopback Mode is active, a downlink DCH data is looped back in the UE 102, and the looped back downlink DCH data becomes an uplink DCH data. When the DCH Loopback Mode is active, there is no guarantee about how often the corresponding network will send the useful data in this mode. Therefore, to determine that the UE 102 is stuck on the dedicated channel, the DCH Loopback Mode should be inactive. If the DCH Loopback Mode is active, then the flow returns to step 302. If the DCH Loopback Mode is not active, then the flow continues to step 312.

[0028] At step 312, a time period is determined from the timer that was started in step 302. At step 314, the determined time period is checked against a pre-defined time period. In an embodiment, the corresponding network controls the pre-defined time period by broadcasting information about the pre-defined time period to the UEs in its coverage area. The information about the pre-defined time period can be broadcast in a system information message. In another embodiment, the corresponding network controls the pre-defined time period by sending pre-defined time period information in a device-specific message to one or more UEs in its

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PCT/US2006/020805 coverage area. The UE 102 receives this message if it lies within the coverage area of the RAN 104.

[0029] If the determined time period is more than the pre-defined time period, then it is ascertained that the UE 102 is stuck on the dedicated channel. If the determined time period is less than the pre-defined time period, then the flow goes to step 316.

[0030] Step 316 determines whether the UE 102 is still engaged in the dedicated channel. If the UE 102 is still engaged in the dedicated channel, then the flow returns to step 304. If the UE 102 is not engaged in the dedicated channel, it is determined that the UE 102 is not stuck on the dedicated channel.

[0031] In an embodiment, the UE 102 performs steps 302 through 316. In another embodiment, the corresponding RAN 104 performs the steps 302 through 316.

[0032] The method and computer program product for resource utilization in the UE 102 is applied in Radio Access Technologies (RATs) such as WCDMA and GSM, in accordance with various embodiments. It should be clear from the preceding disclosure that the method and a computer program product for resource utilization in a UE reduce unnecessary battery consumption in the UE. In addition, the method and computer program product limits wastage of network resources and bandwidth by releasing the UE stuck on the dedicated channel.

[0033] It will be appreciated the methods described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the methods described herein. The non

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PCT/US2006/020805 processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform detection and release of a UE stuck on a dedicated channel. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein.

[0034] It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

[0035] In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms comprises, comprising, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises .. .a” does

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PCT/US2006/020805 not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0036] The term “another”, as used herein, is defined as at least a second or more.

The terms “including” and/or “having”, as used herein, are defined as comprising.

The term “program”, as used herein, is defined as a sequence of instructions designed for execution on a computer system. A “program”, or “computer program”, may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system.

[0037] In the foregoing specification, the invention and its benefits and advantages have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the 15 claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or 20 essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

2006266373 11 Jun 2008