Apparatus and method for increasing reliability of serving cell change

Methods and apparatus are described herein to manage a serving cell change. A HS-SCCH monitored set is maintained to store entries for all pending serving cell change requests. The HS-SCCH for each entry is monitored for a timer period. Once a change request has been confirmed for one entry, monitoring for the other entries continues until expiration of the associated timers.

BACKGROUND

This application relates generally to wireless communications, and more particularly to handling handovers during a wireless communication session.

Enhanced Serving Cell Change (ESCC) is a feature in 3GPP Release 8 designed to improve reliability of the serving cell change procedure. In an ESCC procedure, the network receives a serving cell change request, such and an event 1d (e1d) measurement report message (MRM), and decides to perform a serving cell change. Rather than sending a Physical Channel Reconfiguration message on the source cell HSPDA link, the network sends HS-SCCH orders on the target cell to instruct the UE to start a serving cell change procedure.

Once a user equipment (UE) sends a change request message, the UE begins to monitor the HS-SCCH from the target cell. Once the network processes the change request, the network orders the target cell to send HS-SCCH orders. When a sufficient number of HS-SCCH orders are received by the UE, the UE sends an acknowledgement to the network and starts to receive data from the target cell.

In a rapidly changing RF environment, it is common to generate multiple measurement events back-to-back. In the ESCC procedure, as soon as an e1d MRM is sent, the UE starts to monitor the HS-SCCH for the target cell. That is, the UE assumes that the network will process the e1d MRM just sent by the UE next. However, the network is not required to process e1d MRM messages in the same order as is assumed by the UE. Accordingly, as only a single target cell is monitored at a time even where multiple e1d MRMs are pending, unnecessary serving cell change failure can occur if the e1d MRMs are not processing in the same order by the UE and the network. It would be desirable to have a system and method to alleviate these and other problems associated with the ESCC procedure.

SUMMARY

In accordance with some aspects of the disclosure, a method of changing a high speed data serving cell comprises making a first determination, at a mobile user equipment, to switch a high speed data link from a source serving cell to a first target serving cell; transmitting a first serving cell change request message indicating the first determination to switch to the first target serving cell; monitoring for a first serving cell change order from the first target serving cell for a first time period associated with a first timer; making a second determination, while monitoring for the first serving cell change order from the first target cell, to switch the high speed data link to a second target serving cell; transmitting a second serving cell change request message indicating the second determination to switch to the second target serving cell; and monitoring for a second serving cell change order from the second target serving cell for a second time period associated with a second timer, the second time period occurring during at least a portion of the first timer period.

In accordance with some aspects of the disclosure, an apparatus comprises means for making a first determination to switch a high speed data link from a source serving cell to a first target serving cell; means for transmitting a first serving cell change request message indicating the first determination to switch to the first target serving cell; means for monitoring for a first serving cell change order from the first target serving cell for a first time period associated with a first timer; means for making a second determination, while monitoring for the first serving cell change order from the first target cell, to switch the high speed data link to a second target serving cell; means for transmitting a second serving cell change request message indicating the second determination to switch to the second target serving cell; and means for monitoring for a second serving cell change order from the second target serving cell for a second time period associated with a second timer, the second time period occurring during at least a portion of the first timer period.

In accordance with some aspects of the disclosure, an apparatus comprises a serving cell processing module configured to make a first determination to switch a high speed data link from a source serving cell to a first target serving cell; and transmit a first serving cell change order request message indicating the first determination to switch to the first target serving cell; and a HS-SCCH monitoring module configured to monitor for a first serving cell change order from the first target serving cell for a first time period associated with a first timer, wherein the serving cell processing module is further configured to make a second determination, while monitoring for the first time period, to switch the high speed data link to a second target serving cell, and to transmit a second serving cell change request message indicating the second determination to switch to the second target serving cell, and wherein the HS-SCCH monitoring module is further configured to monitor for a second serving cell change order from the second target serving cell for a second time period associated with a second timer, the second time period occurring during at least a portion of the first time period.

DETAILED DESCRIPTION

An example of a communications system employing various apparatus will now be presented with reference to a network architecture100as shown inFIG. 1. As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for High-Speed Downlink Packet Access (HSDPA) applications. However, these concepts may be readily extended to other communications standards. By way of example, these concepts may be extended to Long Term Evolution (LTE), Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), and/or other communications standards.

The network architecture100is shown with a core network110and an access network120. The core network110may provide packet-switched services to the access network120. For example, core network110may provide a connection for access network120to a packet-based network112, such as the Internet. However, as those of skill in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to core networks providing access to other types of packet-based networks as well as to circuit-switched network services.

Access network120may serve as an access point to the core network110for a mobile apparatus130. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initial protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player, a cameral, a game console, or any other similar functioning device. The mobile apparatus130is commonly referred to as a user equipment (UE) in applications such as HSDPA and LTE, but may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Access network120may include a Radio Network Controller (RNC)122linked to a plurality of cells. Three cells, designated by reference numerals124,126, and128are shown inFIG. 1. Each of cells124,126, and128may be covered by one or separate Node Bs (not shown). The Node Bs may be terrestrial base stations capable of communicating with UE130wirelessly. Cells124,126, and128may be called sectors of a serving Node B, for example, where the cells are served by a single Node B.

UE130may establish initial communications via one of the plurality cells, which is know as the serving cell. For example, if UE130has established a communication session through cell124, then cell124would be known as the serving cell. UE130may maintain an active set (ASET) of cells. The active set includes pilot signal strength and/or other information related to cells in addition to the serving cell. The other cells in the active set may become the candidates for the serving cell if the signal pilot strength exceeds that of the serving cell. For example, as UE130moves to a different coverage area, such as the coverage area provided by cells126or126, the pilot signal strength from one or these cells may exceed that of the current serving cell—cell124. In a communication system such as HSPDA, the serving cell is tracked by both the network and the mobile. That is, both UE130and access network120track the serving cell. Typically, event 1d (“e1d”) reporting is used to provide e1d measurement reports (MRMs) which are sent by UE130to access network120indicating a desired serving cell change.

FIG. 2is a message flow diagram depicting a serving cell change process that may occur in a conventional HSPDA network implementing the enhanced serving cell change (ESCC) mechanism defined in 3GPP Release 8. A UE230may be communicatively coupled to an initial serving cell240, a first target serving cell250, and a second target serving cell260. Information related to these cells may be maintained in the active set (ASET) of UE230.

Since cell240is initially the serving cell, it transmits signaling and data to UE230via the HS-SCCH and HS-PDSCH, respectively, as depicted at204. As depicted at206, UE230may transmit an e1d MRM to RNC270upon determining that first target serving cell250has become stronger than initial serving cell240. This message indicates that UE230wishes to perform a serving cell change from initial serving cell240to first target serving cell250. Upon sending the first e1d MRM, UE230may begin to monitor the HS-SCCH of the first target250, as depicted at208. RNC270buffers the first e1d MRM for processing, as depicted at210.

As shown at212, UE230may send a second e1d MRM to RNC270, the second e1d MRM requesting a change to the second target serving cell260. The second e1d MRM is sent to RNC270prior to receiving and processing an HS-SCCH order from first target serving cell250. In the conventional approach, UE230only monitors a single HC-SCCH at a given time. Moreover, the UE may perform e1d processing in a separate and distinct manner from that of RNC270. In the example depicted inFIG. 2, UE230is configured to always process the latest MRM. Thus, as depicted at214, UE230stops monitoring the HS-SCCH for first target serving cell250and begins to monitor the HS-SCCH for second target serving cell260.

In this example, the RNC270is configured to always process MRM messages in sequence. Thus, as depicted at216, RNC270processes the first e1d MRM, which requested a change to first target serving cell250. RNC270then transmits a message to first target serving cell250requesting that the first target serving cell begin transmitting HS-SCCH order message to UE230. As depicted at220, first target serving cell250sends HS-SCCH order messages to UE230. However, because UE230is no longer monitoring the HS-SCCH for first target serving cell250, these messages are not received/detected. As such, UE230times out waiting to receive messages from second target serving cell260. Meanwhile, RNC270times out waiting to receive an acknowledgement from UE230that the HS-SCCH order from first target cell250has been received. Thus, neither change request is successful, and initial serving cell240remains the serving cell.

This disclosure will now describe exemplary methods and apparatus for avoiding the failures depicted inFIG. 2. In accordance with the exemplary aspects described herein, the HS-SCCH for multiple channels can be monitored by a UE. As such, messages are not missed which may avoid a failed cell change process.

FIG. 3is a conceptual block diagram illustrating an example of a hardware implementation for a UE300employing a processing system310. In this example, processing system310may be implemented with a bus architecture, represented generally by bus302. The bus302may include any number of interconnecting buses and bridges depending on the specific application of the processing system310and the overall design constraints. The bus links together various circuits including one or more processors, represented generally by processor320, and computer-readable media, represented generally by computer-readable medium330. The bus302may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the link, which are well known in the art, and therefore, will not be described any further. A bus interface340provides an interface between the bus302and transceiver350. The transceiver350provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of UE300, a user interface360(e.g., keypad, display, speaker, microphone, etc.) may also be provided.

The processor320is responsible for managing the bus and general processing, including the execution of software stored on the computer-readable medium330. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. A computer-readable medium may include, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, or any other suitable medium for storing or transmitting software. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. Computer-readable medium may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

The functions and methods described herein may be implemented by various modules in UE300. As used herein, the term “modules” is intended to refer to hardware, firmware, a combination of hardware and software, software, or software in execution. By way of example, a module may be a process, an object, an executable, a thread of execution, a program, an application, a routine, a subroutine, a block of code or instructions, or any other software executed by the processor320or by another processing device. In this example, these modules may reside in the computer readable medium330which represents a single storage device, multiple storage devices, or other media. The software, when executed by the processor320, causes the processing system310to perform various functions described herein. The computer-readable medium330may also be used for storing data that is manipulated by the processor320when executing software.

As depicted inFIG. 3, computer readable medium330may store a plurality of UE processing modules, including a serving cell change processing module332and a HS-SCCH monitoring module334. It is noted that while two modules are depicted, the functionality of these two modules may be performed using a single module, multiple modules, or multiple sub-modules. Serving cell change processing module332may be configured to maintain an active set of cells. The cells in the ASET may be candidates for becoming the serving cell if a cell becomes stronger than the current serving cell. The number of cells in the active set may be preconfigured to a maximum number of cells, depending upon the technology in use. In order to monitor additional cells, cell change processing module332may also maintain a monitored set for monitoring additional neighboring cells.

Cell change processing module332may be configured to initiate a serving cell change upon determining that criteria for a cell change have been met. Criteria may include, for example, determining that a cell other than the serving cell has become stronger, met certain quality of service requirements, etc., for a predefined time period. Serving cell change processing module332may be configured to generate a MRM to be transmitted to the network identifying a target cell for the serving cell change.

In accordance with exemplary aspects of the invention, HS-SCCH monitoring module334may be configured to maintain an HS-SCCH order monitored set that contains the set of cells for which an MRM cell change request has been generated and is still pending.

FIG. 4depicts is a conceptual block diagram illustrating an example of a hardware implementation for an RNC400employing a processing system410. In this example, processing system410may be implemented with a bus architecture, represented generally by bus402. The bus402may include any number of interconnecting buses and bridges depending on the specific application of the processing system410and the overall design constraints. The bus links together various circuits including one or more processors, represented generally by processor420, and computer-readable media, represented generally by computer-readable medium430. The bus402may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the link, which are well known in the art, and therefore, will not be described any further. A bus interface440provides an interface between the bus402and transceiver450. The transceiver450provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of RNC400, a user interface460(e.g., keypad, display, speaker, microphone, etc.) may also be provided.

The processor420is responsible for managing the bus and general processing, including the execution of software stored on the computer-readable medium430. One or more processors in the processing system may execute software. The software may reside on a computer-readable medium. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. Computer-readable medium may be embodied in a computer-program product.

As depicted inFIG. 4, computer readable medium430may store one or more RNC processing modules, including a network cell change processing module432. It is noted that while only a single module is depicted, the functionality of this module may be performed using a single module, multiple modules, or multiple sub-modules. Network cell change processing module432may be configured to receive and process cell change request messages, such as e1d MRMs, from a UE such as UE300depicted inFIG. 3. Network cell change processing module432may be configured to implement predefined rules for processing multiple MRMs. These rules may be independent and distinct from any rules implemented by a UE in communication with RNC400. For example, in some instances network cell change processing module432may be configured to process MRMs sequentially. In other implementations, module432may be configured to process the latest received MRM first. Network cell change processing module432may be further configured to issue request to target serving cells to initiate the cell change process, issue commands to update the active set by adding or dropping cells, and/or other processing.

FIG. 5is a high-level flowchart illustrating a method for facilitating a serving cell change. The method depicted inFIG. 5may be implemented, for example, by a UE. As depicted at502, a UE may make a determination to switch from an initial serving cell to a first target serving cell. The determination to switch may be based, for example, on signal strength of the first target serving cell. As depicted at504, the UE may transmit a serving cell change request to an RNC. The change request may be an e1d MRM. The UE may then place an entry for the first target serving cell in its HS-SCCH order monitored set, as depicted at506. This indicates that the HS-SCCH for the first target serving cell should be monitored. As depicted at508, the UE may begin monitoring the control channel for the first target serving cell. That is, the UE may monitor the HS-SCCH associated with the first target serving cell for HS-SCCH orders from the first target serving cell.

As depicted at510, while monitoring the HS-SCCH for the first target serving cell, the UE may make a determination to switch to a second target serving cell. Accordingly, as depicted at512, the UE may transmit a second cell change request (e.g., an e1d MRM) to the RNC requesting a change to the second target serving cell. An entry for the second target serving cell may then be placed in the HS-SCCH order monitored set, as depicted at514, indicating that the second target serving cell is also to be monitored. As depicted at516, the UE then begins monitoring the HS-SCCH channel associated with the second target serving cell.

FIG. 6is a flowchart illustrating further details of an exemplary serving cell change process. As depicted at602, the UE may place an entry in its HS-SCCH order monitored set to monitor a target serving cell after a serving cell change request has been submitted for the target serving cell. Upon placing an entry in the HS-SCCH order monitored set, a timer associated with the target serving cell may be started, as depicted at604. The timer may be used to provide a predefined monitoring period in which the UE monitors an HS-SCCH associated with the target serving cell. Thus, in the case of a rapidly changing environment wherein back-to-back e1ds have been transmitted, the UE monitors the channels for all pending requests for a pre-configured time period. As such, even if the RNC is programmed to process messages in a different order from that of the UE, the UE has time to receive all messages. As depicted at606, an entry in the SCCH monitored set is removed upon expiration of the associated timer. This indicates that the UE no longer needs to monitor the HS-SCCH associated with the removed entry.

FIG. 7is a flowchart illustrating additional details of an exemplary serving cell change process. As depicted at702, a UE may begin monitoring the HS-SCCH associated with a target serving cell. Upon receiving the pre-defined number of HS-SCCH orders from the target serving cell, the UE may then transmit a confirmation message to the RNC to confirm the serving cell change, as depicted at704. The UE may then set the target serving cell as its new serving cell, as depicted at706. Upon setting the target cell as the new serving cell, the UE may also remove the corresponding entry from the HS-SCCH order monitored set, and may cancel the corresponding timer. As depicted at708, the UE determines that there are additional entries in the HS-SCCH order monitored set for additional target serving cells. As depicted at710, the UE continues to monitor the HS-SCCH associated with the additional serving cells until their respective timers expire, or until a predefined number of HS-SCCH orders are received for a target cell. If a predefined number of HS-SCCH orders are received for one of the additional target cells prior to expiration of its associated timer, the cell may become the new serving cell.

FIG. 8is a message flow diagram800depicting an exemplary exchange of messages among a UE802, an initial serving cell804, a first target serving cell806, a second target serving cell808, and an RNC810. As depicted at820, upon determining that a serving cell switch from initial serving cell804to first target serving cell806is desired, UE802transmits an e1d MRM to RNC810requesting a switch to first target serving cell806. The RNC810buffers the e1d message for processing, as depicted at822. As depicted at824, the initial serving cell804remains the serving cell, and UE802places an entry for first target serving cell806in its SCCH monitored set. At this time, the only entry in the HS-SCCH order monitored set is the entry for first target serving cell806.

Prior to completing the serving cell change from initial serving cell804to first target serving cell806, the UE802may determine that a switch to second target serving cell808is desired. Accordingly, as depicted at826, UE802transmits an e1d MRM to RNC810requesting a serving cell change to second target serving cell808. As depicted at828, an entry for second target serving cell808is added to the SCCH monitored set. Thus, the HS-SCCH order monitored set now contains entries for first target serving cell804and second target serving cell806. This means UE802is monitoring both HS-SCCH for both first target serving cell804and second target serving cell806. While not shown inFIG. 8, UE802starts a timer for each of first target serving cell804and second target serving cell806upon placing an entry for each cell in the HS-SCCH order monitored set.

RNC810may be pre-configured with rules which indicate the order in which e1d messages are processed. In the example depicted inFIG. 8, RNC810has been configured to process the latest received e1d message first. Thus, as depicted at830, RNC810process the e1d MRM transmitted in step826, which requested a change to second target serving cell806. As depicted at832, the RNC810issues a command to second target serving cell806to start transmitting HS-SCCH orders to the UE802. Accordingly, as depicted at834, second target serving cell808transmits HS-SCCH orders to UE802. The number of orders to be transmitted may be preconfigured by RNC810. Once UE802has received the pre-defined number of HS-SCCH orders, UE802transmits a physical channel reconfiguration complete message to RNC810to confirm the serving cell change, as depicted at836.

As depicted at838, second target serving cell808becomes the new serving cell. The HS-SCCH order monitored set now contains only an entry for first target serving cell806. Even though the serving cell change to second target serving cell is complete, UE802continues to monitor the HS-SCCH for first target serving cell806until its associated timer expires.

FIG. 9is a message flow diagram900depicting another exemplary exchange of messages among a UE802, an initial serving cell804, a first target serving cell806, a second target serving cell808, and an RNC810. As depicted at920, upon determining that a serving cell switch from initial serving cell804to first target serving cell806is desired, UE802transmits an e1d MRM to RNC810requesting a switch to first target serving cell806. As depicted at922, the initial serving cell804remains the serving cell, and UE802places an entry for first target serving cell806in its SCCH monitored set. At this time, the only entry in the HS-SCCH order monitored set is the entry for first target serving cell806.

Prior to completing the serving cell change from initial serving cell804to first target serving cell806, the UE802may determine that a switch to second target serving cell808is desired. Accordingly, as depicted at924, UE802transmits an e1d MRM to RNC810requesting a serving cell change to second target serving cell808. As depicted at926, an entry for second target serving cell808is added to the SCCH monitored set. Thus, the SCCH monitored set now contains entries for first target serving cell804and second target serving cell806. This means UE802is monitoring both HS-SCCH for both first target serving cell804and second target serving cell806. While not shown inFIG. 9, UE802starts a timer for each of first target serving cell804and second target serving cell806upon placing an entry for each cell in the SCCH monitored set.

RNC810may be pre-configured with rules which indicate the order in which e1d messages are processed. In the example depicted inFIG. 9, RNC810has been configured to process e1d message sequentially, as depicted at928. Thus, as depicted at930, the RNC810issues a command to first target serving cell806to start transmitting HS-SCCH orders to the UE802. Accordingly, as depicted at932, first target serving cell806transmits HS-SCCH orders to UE802. The number of orders to be transmitted may be preconfigured by RNC810. Once UE802has received the pre-defined number of HS-SCCH orders, UE802transmits a physical channel reconfiguration complete message to RNC810to confirm the serving cell change, as depicted at934.

As depicted at936, first target serving cell806becomes the new serving cell. The SCCH monitored set now contains only an entry for second target serving cell808. Even though the serving cell change to first target serving cell is complete, UE802continues to monitor the HS-SCCH for second target serving cell808until its associated timer expires. As depicted at938, RNC810issues a command to second target serving cell808to begin transmitting HS-SCCH orders to UE802. Accordingly, as depicted at940, second target serving cell808transmits HS-SCCH orders to UE802. The HS-SCCH orders from second target serving cell808are received prior to expiration of the associated timer. Accordingly, as depicted at942, UE802transmits a physical channel reconfiguration complete message to RNC810to confirm the serving cell change to second target serving cell808. Thus, as depicted at944, the UE802sets the second target serving cell808as the new serving cell.

In the examples depicted inFIGS. 8 and 9, back-to-back e1d MRMs are transmitted. The transmission of back-to-back e1d MRMs is likely to occur in fast-changing radio environments. For example, when a UE is moving through an urban canyon, or among hills and valleys, it is likely that the signal strengths associated with candidate cells will change often. Moreover, the process of reconfiguring a packet data protocol (PDP) context may take up to a few seconds. During this time, in a fast changing radio environment, it is very likely that back to back MRM events are triggered.

In addition to e1d MRMs, which are used to request a cell change switch, a UE may also transmit event 1b (“e1b”) messages to drop a cell.FIG. 10is a message flow diagram1000depicting another exemplary exchange of messages among a UE802, an initial serving cell804, a first target serving cell806, a second target serving cell808, and an RNC810mwherein e1d and e1b messages are processed. As depicted at1002, UE802transmits an e1d MRM to RNC810requesting to switch from initial serving cell804to first target serving cell806. As depicted at1004, while the initial serving cell804remains the serving cell, UE802adds an entry to its SCCH monitored set for first target serving cell806. The UE may also activate a timer associated with first target serving cell806.

After transmitting the e1d MRM to switch to first target serving cell806, the UE802may determine that the first target serving cell806should be dropped from its active set. For example, the signal from first target serving cell806may be lost, may drop below a pre-defined threshold, or otherwise fail to meet the requirements for being included in the ASET. Thus, as depicted at1006, UE802may transmit an e1b message to RNC810requesting that first target serving cell806be dropped from its active set. UE802may then transmit an e1d MRM to RNC810requesting a serving cell change to second target serving cell808, as depicted at1008. Thus, as depicted at1010, an entry for second target serving cell808is added to the SCCH monitored set, and an associated timer is started.

In the example depicted inFIG. 10, RNC810may be configured to process e1d message sequentially. Thus, the MRM to switch to first target serving cell806would be processed first. However, the RNC810may further be configured to drop the e1d request to switch to the first target cell since it has also received an e1b message to drop the first target serving cell from the ASET. Accordingly, as depicted at1010, RNC810processes the e1d MRM to switch to second target serving cell808first. RNC810orders second target serving cell808to begin transmitting HS-SCCH orders, as depicted at1014, and the second target serving cell808complies, as depicted at1016.

Upon receipt of the pre-defined number of HS-SCCH orders from second target serving cell808, UE802transmits a physical channel reconfiguration complete message to RNC810, as depicted at1018. Accordingly, as depicted at1020, second target serving cell808becomes the new serving cell, and the SCCH monitored set retains its entry for first target serving cell806. As depicted at1022, the RNC810may then begin to process the e1b MRM transmitted by UE802in step1006. The RNC810issues an active set update message to UE802instructing the UE to remove the first target serving cell806from its ASET, as depicted at1024. The UE802responds with a physical channel reconfiguration complete message, as depicted at1026, and UE802removes the entry for the first target serving cell806from its HS-SCCH order monitored set, as depicted at1028.

Turning toFIG. 11, illustrated is a system1100for managing serving cell changes. As depicted, system1100includes functional blocks that can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). System1100includes a logical grouping1102of electrical components that act in conjunction. System1100may be implemented, for example, by a UE.

Logical grouping1102can include a module for making a first determination to switch to a high speed data link from a source serving cell to a first target serving cell1104. Moreover, logical grouping1102can include a module transmitting a first serving cell change request message indicating the first determination to switch to the first target serving cell1106. Logical group1102may further include a module for monitoring for a first serving cell change order from the first target serving cell for a time period associated with a first timer1108; a module for making a second determination, while monitoring for the first serving cell change order from the first target cell, to switch the high speed data link to a second target serving cell1110; a module for transmitting a second serving cell change request message indicating the second determination to switch to the second target serving cell1112; and a module for monitoring for a second serving cell change order from the second target serving cell for a second timer period associated with a second timer, the second time period occurring during at least a portion of the first timer period1114. Additionally, system1100can include a memory1118that retains instructions for executing functions associated with electrical components1104-1114. While shown as being external to memory1118, it is to be understood that electrical components1104-1114can exist within memory1118.