WO2018082683A1 - Techniques for reducing call delay using a session initiation protocol (sip) message timer - Google Patents
Techniques for reducing call delay using a session initiation protocol (sip) message timer Download PDFInfo
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- WO2018082683A1 WO2018082683A1 PCT/CN2017/109438 CN2017109438W WO2018082683A1 WO 2018082683 A1 WO2018082683 A1 WO 2018082683A1 CN 2017109438 W CN2017109438 W CN 2017109438W WO 2018082683 A1 WO2018082683 A1 WO 2018082683A1
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- H04W80/10—Upper layer protocols adapted for application session management, e.g. SIP [Session Initiation Protocol]
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Definitions
- the present disclosure relates generally to communication systems, and more particularly, to techniques and apparatuses for reducing call delay using a SIP message timer.
- Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts.
- Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power) .
- multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
- CDMA code division multiple access
- TDMA time division multiple access
- FDMA frequency division multiple access
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single-carrier frequency division multiple access
- TD-SCDMA time division synchronous code division multiple access
- LTE Long Term Evolution
- UMTS Universal Mobile Telecommunications System
- 3GPP Third Generation Partnership Project
- LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA on the downlink (DL) , SC-FDMA on the uplink (UL) , and multiple-input multiple-output (MIMO) antenna technology.
- OFDMA on the downlink
- UL uplink
- MIMO multiple-input multiple-output
- the method may include transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message.
- the method may include initiating, by the UE, a timer based at least in part on the transmission of the SIP message.
- the method may include triggering, by the UE and based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
- RLF radio link failure
- OOS out of service
- the apparatus may include means for transmitting a session initiation protocol (SIP) message.
- the apparatus may include means for initiating a timer based at least in part on the transmission of the SIP message.
- the apparatus may include means for triggering, based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
- RLF radio link failure
- OOS out of service
- the apparatus may include a memory and at least one processor coupled to the memory and configured to transmit a session initiation protocol (SIP) message.
- the at least one processor may be configured to initiate a timer based at least in part on the transmission of the SIP message.
- the at least one processor may be configured to trigger, based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
- RLF radio link failure
- OOS out of service
- the computer program product may include a non-transitory computer-readable medium storing computer executable code for wireless communication.
- the code may include code for transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message.
- the code may include code for initiating, by the UE, a timer based at least in part on the transmission of the SIP message.
- the code may include code for triggering, by the UE and based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
- RLF radio link failure
- OOS out of service
- FIG. 1 is a diagram illustrating an example of a network architecture.
- FIG. 2 is a diagram illustrating an example of an access network.
- FIG. 3 is a diagram illustrating an example of a DL frame structure in LTE.
- FIG. 4 is a diagram illustrating an example of an UL frame structure in LTE.
- FIG. 5 is a diagram illustrating an example of a radio protocol architecture for the user and control planes.
- FIG. 6 is a diagram illustrating an example of an evolved Node B and user equipment in an access network.
- FIG. 7 is a diagram illustrating an example system configured to reduce call delays using a SIP message timer.
- FIG. 8 is a diagram illustrating another example system configured to reduce call delays using a SIP message timer.
- FIG. 9 is a flow chart of a method of wireless communication.
- FIG. 10 is a conceptual data flow diagram illustrating the data flow between different modules/means/components in an example apparatus.
- FIG. 11 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.
- 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.
- DSPs digital signal processors
- FPGAs field programmable gate arrays
- PLDs programmable logic devices
- 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 functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium.
- Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer.
- such computer-readable media can comprise a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , compact disk ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.
- RAM random-access memory
- ROM read-only memory
- EEPROM electrically erasable programmable ROM
- CD-ROM compact disk ROM
- magnetic disk storage magnetic disk storage or other magnetic storage devices
- FIG. 1 is a diagram illustrating an LTE network architecture 100.
- the LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100.
- the EPS 100 may include one or more user equipment (UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, and an Operator’s Internet Protocol (IP) Services 122.
- the EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown.
- the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.
- the E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108, and may include a Multicast Coordination Entity (MCE) 128.
- the eNB 106 provides user and control planes protocol terminations toward the UE 102.
- the eNB 106 may be connected to the other eNBs 108 via a backhaul (e.g., an X2 interface) .
- the MCE 128 allocates time/frequency radio resources for evolved Multimedia Broadcast Multicast Service (MBMS) (eMBMS) , and determines the radio configuration (e.g., a modulation and coding scheme (MCS) ) for the eMBMS.
- the MCE 128 may be a separate entity or part of the eNB 106.
- the eNB 106 may also be referred to as a base station, a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , or some other suitable terminology.
- the eNB 106 provides an access point to the EPC 110 for a UE 102.
- Examples of UEs 102 include a cellular phone, a smart phone, a session initiation 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 camera, a game console, a tablet, or any other similar functioning device.
- SIP session initiation protocol
- PDA personal digital assistant
- the UE 102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, 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.
- the eNB 106 is connected to the EPC 110.
- the EPC 110 may include a Mobility Management Entity (MME) 112, a Home Subscriber Server (HSS) 120, other MMEs 114, a Serving Gateway 116, a Multimedia Broadcast Multicast Service (MBMS) Gateway 124, a Broadcast Multicast Service Center (BM-SC) 126, and a Packet Data Network (PDN) Gateway 118.
- MME Mobility Management Entity
- HSS Home Subscriber Server
- MBMS Multimedia Broadcast Multicast Service
- BM-SC Broadcast Multicast Service Center
- PDN Packet Data Network
- the PDN Gateway 118 provides UE IP address allocation as well as other functions.
- the PDN Gateway 118 and the BM-SC 126 are connected to the IP Services 122.
- the IP Services 122 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service (PSS) , and/or other IP services.
- the BM-SC 126 may provide functions for MBMS user service provisioning and delivery.
- the BM-SC 126 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a PLMN, and may be used to schedule and deliver MBMS transmissions.
- the MBMS Gateway 124 may be used to distribute MBMS traffic to the eNBs (e.g., 106, 108) belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.
- MMSFN Multicast Broadcast Single Frequency Network
- FIG. 1 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 1.
- FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture.
- the access network 200 is divided into a number of cellular regions (cells) 202.
- One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202.
- the lower power class eNB 208 may be a femto cell (e.g., home eNB (HeNB) ) , pico cell, micro cell, or remote radio head (RRH) .
- the macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point to the EPC 110 for all the UEs 206 in the cells 202.
- the eNBs 204 are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway 116.
- An eNB may support one or multiple (e.g., three) cells (also referred to as a sectors) .
- the term “cell” can refer to the smallest coverage area of an eNB and/or an eNB subsystem serving a particular coverage area. Further, the terms “eNB, ” “base station, ” and “cell” may be used interchangeably herein.
- the modulation and multiple access scheme employed by the access network 200 may vary depending on the particular telecommunications standard being deployed.
- OFDM is used on the DL
- SC-FDMA is used on the UL to support both frequency division duplex (FDD) and time division duplex (TDD) .
- FDD frequency division duplex
- TDD time division duplex
- the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) .
- EV-DO Evolution-Data Optimized
- UMB Ultra Mobile Broadband
- EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, and Flash-OFDM employing OFDMA.
- UTRA Universal Terrestrial Radio Access
- W-CDMA Wideband-CDMA
- GSM Global System for Mobile Communications
- E-UTRA Evolved UTRA
- IEEE 802.11 Wi-Fi
- WiMAX IEEE 802.16
- IEEE 802.20 Flash-OFDM employing OFDMA.
- UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization.
- CDMA2000 and UMB are described in documents from the 3GPP2 organization.
- the actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.
- the eNBs 204 may have multiple antennas supporting MIMO technology.
- MIMO technology enables the eNBs 204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity.
- Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency.
- the data streams may be transmitted to a single UE 206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL.
- the spatially precoded data streams arrive at the UE (s) 206 with different spatial signatures, which enables each of the UE (s) 206 to recover the one or more data streams destined for that UE 206.
- each UE 206 transmits a spatially precoded data stream, which enables the eNB 204 to identify the source of each spatially precoded data stream.
- Beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.
- OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol.
- the subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers.
- a guard interval e.g., cyclic prefix
- the UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR) .
- PAPR peak-to-average power ratio
- FIG. 2 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 2.
- FIG. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE.
- a frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots.
- a resource grid may be used to represent two time slots, each time slot including a resource block.
- the resource grid is divided into multiple resource elements.
- a resource block contains 12 consecutive subcarriers in the frequency domain and 7 consecutive OFDM symbols in the time domain, for a total of 84 resource elements.
- For an extended cyclic prefix a resource block contains 12 consecutive subcarriers in the frequency domain and 6 consecutive OFDM symbols in the time domain, for a total of 72 resource elements.
- Some of the resource elements, indicated as R 302, 304, include DL reference signals (DL-RS) .
- the DL-RS include Cell-specific RS (CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS) 304.
- UE-RS 304 are transmitted on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped.
- PDSCH physical DL shared channel
- the number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.
- FIG. 3 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 3.
- FIG. 4 is a diagram 400 illustrating an example of an UL frame structure in LTE.
- the available resource blocks for the UL may be partitioned into a data section and a control section.
- the control section may be formed at the two edges of the system bandwidth and may have a configurable size.
- the resource blocks in the control section may be assigned to UEs for transmission of control information.
- the data section may include all resource blocks not included in the control section.
- the UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.
- a UE may be assigned resource blocks 410a, 410b in the control section to transmit control information to an eNB.
- the UE may also be assigned resource blocks 420a, 420b in the data section to transmit data to the eNB.
- the UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section.
- the UE may transmit data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section.
- a UL transmission may span both slots of a subframe and may hop across frequency.
- a set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) 430.
- the PRACH 430 carries a random sequence and cannot carry any UL data/signaling.
- Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks.
- the starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH.
- the PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make a single PRACH attempt per frame (10 ms) .
- FIG. 4 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 4.
- FIG. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user and control planes in LTE.
- the radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3.
- Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions.
- the L1 layer will be referred to herein as the physical layer 506.
- Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and eNB over the physical layer 506.
- the L2 layer 508 includes a media access control (MAC) sublayer 510, a radio link control (RLC) sublayer 512, and a packet data convergence protocol (PDCP) 514 sublayer, which are terminated at the eNB on the network side.
- MAC media access control
- RLC radio link control
- PDCP packet data convergence protocol
- the UE may have several upper layers above the L2 layer 508 including a network layer (e.g., IP layer) that is terminated at the PDN gateway 118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .
- IP layer e.g., IP layer
- the PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels.
- the PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs.
- the RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) .
- the MAC sublayer 510 provides multiplexing between logical and transport channels.
- the MAC sublayer 510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs.
- the MAC sublayer 510 is also responsible for HARQ operations.
- the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 506 and the L2 layer 508 with the exception that there is no header compression function for the control plane.
- the control plane also includes a radio resource control (RRC) sublayer 516 in Layer 3 (L3 layer) .
- the RRC sublayer 516 is responsible for obtaining radio resources (e.g., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.
- FIG. 5 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 5.
- FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650 in an access network.
- upper layer packets from the core network are provided to a controller/processor 675.
- the controller/processor 675 implements the functionality of the L2 layer.
- the controller/processor 675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 650 based on various priority metrics.
- the controller/processor 675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 650.
- the transmit (TX) processor 616 implements various signal processing functions for the L1 layer (i.e., physical layer) .
- the signal processing functions include coding and interleaving to facilitate forward error correction (FEC) at the UE 650 and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) .
- FEC forward error correction
- BPSK binary phase-shift keying
- QPSK quadrature phase-shift keying
- M-PSK M-phase-shift keying
- M-QAM M-quadrature amplitude modulation
- Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream.
- the OFDM stream is spatially precoded to produce multiple spatial streams.
- Channel estimates from a channel estimator 674 may be used to determine the coding and modulation scheme, as well as for spatial processing.
- the channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 650.
- Each spatial stream may then be provided to a different antenna 620 via a separate transmitter 618TX.
- Each transmitter 618TX may modulate an RF carrier with a respective spatial stream for transmission.
- each receiver 654RX receives a signal through its respective antenna 652.
- Each receiver 654RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 656.
- the RX processor 656 implements various signal processing functions of the L1 layer.
- the RX processor 656 may perform spatial processing on the information to recover any spatial streams destined for the UE 650. If multiple spatial streams are destined for the UE 650, they may be combined by the RX processor 656 into a single OFDM symbol stream.
- the RX processor 656 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) .
- FFT Fast Fourier Transform
- the frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal.
- the symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 610. These soft decisions may be based on channel estimates computed by the channel estimator 658.
- the soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 610 on the physical channel.
- the data and control signals are then provided to the controller/processor 659.
- the controller/processor 659 implements the L2 layer.
- the controller/processor can be associated with a memory 660 that stores program codes and data.
- the memory 660 may be referred to as a computer-readable medium.
- the controller/processor 659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network.
- the upper layer packets are then provided to a data sink 662, which represents all the protocol layers above the L2 layer.
- Various control signals may also be provided to the data sink 662 for L3 processing.
- the controller/processor 659 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.
- ACK acknowledgement
- NACK negative acknowledgement
- a data source 667 is used to provide upper layer packets to the controller/processor 659.
- the data source 667 represents all protocol layers above the L2 layer.
- the controller/processor 659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 610.
- the controller/processor 659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 610.
- Channel estimates derived by a channel estimator 658 from a reference signal or feedback transmitted by the eNB 610 may be used by the TX processor 668 to select the appropriate coding and modulation schemes, and to facilitate spatial processing.
- the spatial streams generated by the TX processor 668 may be provided to different antenna 652 via separate transmitters 654TX. Each transmitter 654TX may modulate an RF carrier with a respective spatial stream for transmission.
- the UL transmission is processed at the eNB 610 in a manner similar to that described in connection with the receiver function at the UE 650.
- Each receiver 618RX receives a signal through its respective antenna 620.
- Each receiver 618RX recovers information modulated onto an RF carrier and provides the information to a RX processor 670.
- the RX processor 670 may implement the L1 layer.
- the controller/processor 675 implements the L2 layer.
- the controller/processor 675 can be associated with a memory 676 that stores program codes and data.
- the memory 676 may be referred to as a computer-readable medium.
- the controller/processor 675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 650.
- Upper layer packets from the controller/processor 675 may be provided to the core network.
- the controller/processor 675 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.
- FIG. 6 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 6.
- an eNB may be unable to receive a SIP message sent by the UE, such as a SIP INVITE message used to set up a Voice over Long Term Evolution (VoLTE) call.
- the UE may perform a Circuit Switched Fallback (CSFB) procedure to connect to a different RAT (other than LTE) and set up the call.
- CSFB Circuit Switched Fallback
- the UE may use a CSFB timer to trigger the CSFB procedure, and there may be a relatively long delay at the UE to detect such a failure using the CSFB timer. Further, performing the CSFB procedure to set up the call using a RAT other than LTE may cause additional delay.
- Implementations described herein reduce call setup delay using a SIP message timer that triggers selection of another LTE cell via a radio link failure (RLF) procedure, or that triggers selection of another RAT via an out of service (OOS) procedure. In this way, call setup delays may be reduced and a user experience may be enhanced.
- RLF radio link failure
- OOS out of service
- FIG. 7 is a diagram illustrating an example system 700 configured to reduce call delays using a SIP message timer.
- FIG. 7 relates to an example where expiration of the SIP message timer triggers cell selection via an RLF procedure.
- example system 700 may include a UE 710 (e.g., which may include one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, etc. ) , an eNB 720-a (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, etc. ) associated with a cell 730-a, and an eNB 720-b (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, etc. ) associated with a cell 730-b.
- the UE 710 may be camped on the cell 730-a of the eNB 720-a.
- the UE 710 may transmit a SIP message.
- the SIP message may be a SIP INVITE message used to set up a call, such as a VoLTE call.
- the SIP message may be another type of SIP message, such as a SIP REFER message, a SIP re-INVITE message, or the like.
- the eNB 720-a may fail to receive the SIP INVITE message.
- the eNB 720-a may fail to receive the SIP INVITE message due to poor network conditions or another adverse scenario.
- the UE 710 may initiate a timer based at least in part on transmission of the SIP message (e.g., the SIP INVITE message) .
- this timer may be referred to as a SIP message timer because the timer may be initiated by the UE 710 based at least in part on the transmission of the SIP message.
- the SIP message timer may be initiated and/or monitored by an access stratum (AS) layer of the UE 710.
- AS access stratum
- the UE 710 may trigger a radio link failure (RLF) procedure for cell selection (or reselection) .
- RLF radio link failure
- the UE 710 may perform the RLF procedure to connect to another cell, such as cell 730-b of eNB 720-b, and may retry call setup of the VoLTE call using the selected cell.
- the UE 710 may reduce delays associated with setting up the call, thereby improving a user experience and conserving computing and network resources.
- the UE 710 may be connected to a first cell (e.g., cell 730-a) using a RAT (e.g., LTE) .
- the UE 710 may determine that a second cell of the RAT (e.g., another LTE cell, such as cell 730-b) satisfies a condition, such as a handover condition, a reselection condition, a signal quality condition (e.g., the second cell 730-b has a threshold signal quality at the UE 710) , a signal strength condition (e.g., the second cell 730-b has a threshold signal strength at the UE 710) , or the like.
- a condition such as a handover condition, a reselection condition, a signal quality condition (e.g., the second cell 730-b has a threshold signal quality at the UE 710) , a signal strength condition (e.g., the second cell 730-b has a threshold signal strength at the UE
- the UE 710 may determine whether another LTE cell is available, whether a better LTE cell (e.g., an LTE cell with a higher signal strength, signal quality, etc. ) than the current LTE cell is available, or the like.
- the UE 710 may trigger the RLF procedure to select the second cell of the RAT (e.g., cell 730-b) based at least in part on determining that the second cell of the RAT satisfies the condition. In this way, the UE 710 may avoid connecting to the second cell 730-b when the second cell 730-b will provide a poor user experience or will waste resources (e.g., due to poor signal quality, poor signal strength, etc. ) .
- the UE 710 may perform cell reselection to transition from a first cell of a first eNB to a second cell of the first eNB. For example, in a carrier aggregation scenario, the UE 710 may select another cell of the same eNB by performing the RLF procedure (e.g., may select a cell that provides a better connection than a current cell on which the UE 710 is camped) .
- the RLF procedure e.g., may select a cell that provides a better connection than a current cell on which the UE 710 is camped
- the eNB 720-a may successfully receive the SIP message from the UE 710.
- the eNB 720-a may transmit a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message (e.g., a SIP ACK message) to the UE 710.
- RLC radio link control
- the UE 710 may stop the SIP message timer. In this way, the UE 710 may prevent the RLF procedure from being performed when the SIP message is successfully received by the eNB 720-a, thereby conserving computing resources and network resources.
- the UE 710 may not receive the RLC ACK (e.g., due to poor network conditions) .
- the SIP message timer may continue to run, and expiration of the SIP message timer may trigger the UE 710 to perform the RLF procedure to reduce call setup delays under poor network conditions.
- the UE 710 may also initiate another timer based at least in part on the transmission of the SIP message. This timer may be referred to as CSFB timer because expiration of this timer may trigger a CSFB procedure.
- the SIP message timer may have a shorter duration than the CSFB timer, thereby reducing delays in call setup that would otherwise require the UE 710 to wait until expiration of the CSFB timer.
- use of the SIP message timer may improve a user experience by keeping the UE 710 connected to a higher priority RAT (e.g., an LTE RAT rather than a GSM RAT) .
- the UE 710 may monitor the CSFB timer in the IMS layer of the UE 710, and may monitor the SIP message timer in the AS layer of the UE 710.
- FIG. 7 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 7.
- FIG. 8 is a diagram illustrating another example system 800 configured to reduce call delays using a SIP message timer.
- FIG. 8 relates to an example where expiration of the SIP message timer triggers RAT selection via an OOS procedure.
- example system 800 may include a UE 810 (e.g., which may include one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, the UE 710 of FIG. 7, etc. ) , an eNB 820 (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, the eNB 720-a, 720-b of FIG. 7, etc. ) associated with a GSM cell 830 and an LTE cell 840.
- the UE 810 may be camped on the LTE cell 840 of the eNB 820.
- the UE 810 may transmit a SIP message.
- the SIP message may be a SIP INVITE message used to set up a call, such as a VoLTE call.
- the SIP message may be another type of SIP message, such as a SIP REFER message, a SIP re-INVITE message, or the like.
- the eNB 820 may fail to receive the SIP INVITE message via the LTE cell 840.
- the eNB 820 may fail to receive the SIP INVITE message due to poor network conditions or another adverse scenario associated with the LTE cell 840.
- the UE 810 may not receive an RLC ACK from the eNB 820 (e.g., due to poor network conditions) .
- the SIP message timer may continue to run, and expiration of the SIP message timer may trigger the UE 810 to perform the OOS procedure to reduce call setup delays under poor network conditions.
- the UE 810 may initiate a SIP message timer based at least in part on transmission of the SIP message (e.g., the SIP INVITE message) , as described above in connection with FIG. 7.
- the UE 810 may trigger an out of service (OOS) procedure for RAT selection (or reselection) .
- OOS out of service
- the UE 810 may perform the OOS procedure to connect to another RAT, such as a GSM RAT (e.g., GSM cell 830 of eNB 820) , and may retry call setup using the selected RAT.
- GSM RAT e.g., GSM cell 830 of eNB 820
- the UE 810 may reduce delays associated with setting up the call, thereby improving a user experience and conserving computing and network resources.
- the UE 810 may be connected to a first cell using a first RAT, such as LTE cell 840.
- the UE 810 may determine that no cells of the first RAT (e.g., no other LTE cells, such as the multiple cells 730-a and 730-b of FIG. 7) satisfy a condition, such as a handover condition, a reselection condition, a signal quality condition, a signal strength condition, or the like.
- a condition such as a handover condition, a reselection condition, a signal quality condition, a signal strength condition, or the like.
- the UE 810 may determine that no other LTE cells are available, that no LTE cells with better signal conditions (e.g., higher signal strength, higher signal quality, etc. ) than the current LTE cell are available, or the like.
- the UE 810 may trigger the OOS procedure to select a second RAT (e.g., GSM cell 830) based at least in part on determining that no cells of the first RAT satisfy the condition. In this way, the UE 810 may avoid connecting to a cell that would provide a poor user experience or will waste resources (e.g., due to poor signal quality, poor signal strength, etc. ) .
- a second RAT e.g., GSM cell 830
- the UE 810 may perform RAT reselection to transition from a first cell of a first eNB to a second cell of the first eNB.
- the UE 710 may select another eNB that supports the second RAT (e.g., may select an eNB that provides a better connection than a current eNB on which the UE 810 is camped) .
- the first eNB may be provide network access using an LTE RAT
- the second eNB may provide network access using a GSM RAT.
- the eNB 820 may successfully receive the SIP message from the UE 810, and may transmit an RLC ACK message to the UE 810, which may cause the UE 810 to stop the SIP message timer, as described above in connection with FIG. 7. Additionally, or alternatively, the UE 810 may initiate a CSFB timer based at least in part on the transmission of the SIP message, as described above in connection with FIG. 7.
- FIG. 8 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 8.
- FIG. 9 is a flow chart 900 of a method of wireless communication.
- the method may be performed by a UE (e.g., one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, the UE 710 of FIG. 7, the UE 810 of FIG. 8, the apparatus 1002 of FIG. 10, the apparatus 1002′of FIG. 11, etc. ) .
- a UE e.g., one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, the UE 710 of FIG. 7, the UE 810 of FIG. 8, the apparatus 1002 of FIG. 10, the apparatus 1002′of FIG. 11, etc.
- the UE may transmit a SIP message.
- the UE may transmit a SIP message intended for an eNB.
- the SIP message may include a SIP INVITE message associated with setting up a VoLTE call.
- the UE may initiate a timer based at least in part on the transmission of the SIP message. For example, the UE may detect the transmission of the SIP message (e.g., at an access stratum layer of the UE) , and may initiate a timer (e.g., a SIP message timer) based at least in part on the transmission of the SIP message.
- this timer may trigger an RLF procedure or an OOS procedure upon expiration, as described in more detail elsewhere herein.
- this timer may be referred to as a SIP message timer, and may be different from a CSFB timer that triggers a CSFB procedure upon expiration.
- the SIP message timer may be initiated independently of the CSFB timer, may have a shorter duration than the CSFB timer, may be initiated and/or monitored at a different layer than the CSFB timer (e.g., the SIP message timer may be monitored at an access stratum layer, and the CSFB timer may be monitored at an IMS layer) , or the like.
- the UE may stop the timer based at least in part on receiving an RLC ACK message associated with the transmitted SIP message.
- the UE may determine whether a condition is satisfied for a RAT to which the UE is connected.
- the UE may be connected to a cell using a RAT, and may determine whether a condition is satisfied for the RAT.
- the condition may include, for example, whether there is another available cell of the RAT (e.g., whether any cells satisfy a handover condition, a reselection condition, a signal quality condition, a signal strength condition, or the like) .
- the UE may trigger an RLF procedure or an OOS procedure based at least in part on whether the condition is satisfied, as described below.
- the UE may trigger, based at least in part on expiration of the timer, an RLF procedure for cell selection.
- the UE may be connected to a first cell using a first RAT.
- the UE may determine that a second cell of the first RAT satisfies a condition, and may trigger the RLF procedure to select the second cell of the first RAT based at least in part on determining that the second cell of the first RAT satisfies the condition.
- the UE may be connected to a cell using a RAT.
- the UE may determine whether there are any available cells of the RAT, and may selectively trigger the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT. For example, the UE may trigger the RLF procedure when there is at least one available cell of the RAT.
- the UE may trigger, based at least in part on expiration of the timer, an OOS procedure for RAT selection.
- the UE may be connected to a first cell using a first RAT.
- the UE may determine that no cells of the first RAT satisfy a condition, and may trigger the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition.
- the UE may be connected to a cell using a RAT.
- the UE may determine whether there are any available cells of the RAT, and may selectively trigger the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT.
- the UE may trigger the OOS procedure when there are not any available cells of the RAT.
- the UE may reduce call setup delays associated with setting up a VoLTE call, and/or may reduce delays associated with one or more other procedures that involve SIP messaging.
- FIG. 9 shows example blocks of a method of wireless communication
- the method may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those shown in FIG. 9. Additionally, or alternatively, two or more blocks shown in FIG. 9 may be performed in parallel.
- FIG. 10 is a conceptual data flow diagram 1000 illustrating the data flow between different modules/means/components in an example apparatus 1002.
- the apparatus may be a UE, such as the UE 102, the UE 206, the UE 650, the UE 710, the UE 810, or the like.
- the apparatus includes a transmission module 1004, an initiation module 1006, a triggering module 1008, a determining module 1010, and a reception module 1012.
- the transmission module 1004 may transmit data 1014, which may include a SIP message, as described in more detail elsewhere herein.
- the apparatus 1002 may transmit the data 1014 as output to an eNB 1050 (e.g., which may include one or more of the eNBs described elsewhere herein) .
- the transmission module 1004 may provide data 1016 to initiation module 1006.
- Data 1016 may include an indication that the SIP message was transmitted Additionally, or alternatively, initiating module 1006 may monitor for the transmission of data 1014 (e.g., the SIP message) .
- the initiation module 1006 may initiate a timer (e.g., a SIP message timer) based at least in part on the transmission of the SIP message.
- the initiation module 1006 may provide information regarding the timer to triggering module 1008 as data 1018.
- Triggering module 1008 may monitor the timer (e.g., at an access stratum layer of the apparatus 1002) , and may trigger, based at least in part on expiration of the timer, at least one of an RLF procedure for cell selection, or an OOS procedure for RAT selection.
- Triggering module 1018 may output data 1020 to transmission module 1004 to trigger the RLF procedure or the OSS procedure (e.g., to cause the transmission module 1004 to initiate the RLF procedure or the OOS procedure by providing data 1014 to eNB 1050) .
- the initiation module 1006 may provide information regarding the timer to the determining module 1010 as data 1022.
- the determining module 1010 may determine whether a condition is satisfied for a RAT. In some aspects, upon expiration of the timer, the determining module 1010 may obtain data 1024 from the reception module 1012, and may determine whether the condition is satisfied based at least in part on the data 1024 (e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc. ) . The determining module 1010 may provide an indication regarding whether the condition is satisfied to triggering module 1008 as data 1028. The triggering module 1008 may use the data 1028 and/or the data 1018 to trigger the RLF procedure or the OOS procedure, and may provide data 1020 to the transmission module 1004 regarding which procedure is to be performed.
- the data 1024 e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc.
- the determining module 1010 may provide an indication regarding whether the condition is satisfied to triggering module 1008 as data 10
- the reception module 1012 may receive data 1026 (e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc. ) from one or more eNBs 1050, may process the data 1026 to form data 1024, and may output the data 1024 to the determining module 1010. In some aspects, the reception module 1012 may provide data 1030 to initiation module 1006 to stop the SIP message timer. For example, the data 1026 received from eNB 1050 may include an RLC ACK message and, as a result, the reception module 1012 may provide an instruction to stop the SIP message timer to the initiation module 1006 as data 1030.
- data 1026 e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc.
- the apparatus may include additional modules that perform each of the blocks of the algorithm in the aforementioned flow chart of FIG. 9. As such, each block in the aforementioned flow chart of FIG. 9 may be performed by a module and the apparatus may include one or more of those modules.
- the modules may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.
- modules shown in FIG. 10 are provided as an example. In practice, there may be additional modules, fewer modules, different modules, or differently arranged modules than those shown in FIG. 10. Furthermore, two or more modules shown in FIG. 10 may be implemented within a single module, or a single module shown in FIG. 10 may be implemented as multiple, distributed modules. Additionally, or alternatively, a set of modules (e.g., one or more modules) shown in FIG. 10 may perform one or more functions described as being performed by another set of modules shown in FIG. 10.
- FIG. 11 is a diagram 1100 illustrating an example of a hardware implementation for an apparatus 1002′employing a processing system 1102.
- the processing system 1102 may be implemented with a bus architecture, represented generally by the bus 1104.
- the bus 1104 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1102 and the overall design constraints.
- the bus 1104 links together various circuits including one or more processors and/or hardware modules, represented by the processor 1106, the modules 1004, 1006, 1008, 1010, 1012, and the computer-readable medium /memory 1108.
- the bus 1104 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits.
- the processing system 1102 may be coupled to a transceiver 1110.
- the transceiver 1110 is coupled to one or more antennas 1112.
- the transceiver 1110 provides a means for communicating with various other apparatus over a transmission medium.
- the transceiver 1110 receives a signal from the one or more antennas 1112, extracts information from the received signal, and provides the extracted information to the processing system 1102, specifically the reception module 1012.
- the transceiver 1110 receives information from the processing system 1102, specifically the transmission module 1004, and based on the received information, generates a signal to be applied to the one or more antennas 1112.
- the processing system 1102 includes a processor 1106 coupled to a computer-readable medium /memory 1108.
- the processor 1106 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1108.
- the software when executed by the processor 1106, causes the processing system 1102 to perform the various functions described supra for any particular apparatus.
- the computer-readable medium /memory 1108 may also be used for storing data that is manipulated by the processor 1106 when executing software.
- the processing system further includes at least one of the modules 1004, 1006, 1008, 1010, 1012.
- the modules may be software modules running in the processor 1106, resident/stored in the computer readable medium /memory 1108, one or more hardware modules coupled to the processor 1106, or some combination thereof.
- the processing system 1102 may be a component of the UE 650 and may include the memory 660 and/or at least one of the TX processor 668, the RX processor 656, and the controller/processor 659.
- the apparatus 1002/1002′for wireless communication includes means for transmitting a SIP message, means for initiating a timer based at least in part on the transmission of the SIP message, means for triggering at least one of an RLF procedure for cell selection or an OOS procedure for RAT selection, means for determining whether a condition is satisfied for a RAT, means for selectively triggering the RLF procedure or the OOS procedure based at least in part on determining whether the condition is satisfied for the RAT, and/or means for stopping the timer.
- the aforementioned means may be one or more of the aforementioned modules of the apparatus 1002 and/or the processing system 1102 of the apparatus 1002′configured to perform the functions recited by the aforementioned means.
- the processing system 1102 may include the TX Processor 668, the RX Processor 656, and the controller/processor 659.
- the aforementioned means may be the TX Processor 668, the RX Processor 656, and the controller/processor 659 configured to perform the functions recited by the aforementioned means.
- Combinations such as “at least one of A, B, or C, ” “at least one of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C.
- combinations such as “at least one of A, B, or C, ” “at least one of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C.
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Abstract
A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus may transmit a session initiation protocol (SIP) message. The apparatus may initiate a timer based at least in part on the transmission of the SIP message. The apparatus may trigger, based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
Description
The present disclosure relates generally to communication systems, and more particularly, to techniques and apparatuses for reducing call delay using a SIP message timer.
Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE) . LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP) . LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA on the downlink (DL) , SC-FDMA on the uplink (UL) , and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-
access technologies and the telecommunication standards that employ these technologies.
SUMMARY
In an aspect of the disclosure, a method, an apparatus, and a computer program product are provided.
In some aspects, the method may include transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message. The method may include initiating, by the UE, a timer based at least in part on the transmission of the SIP message. The method may include triggering, by the UE and based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
In some aspects, the apparatus may include means for transmitting a session initiation protocol (SIP) message. The apparatus may include means for initiating a timer based at least in part on the transmission of the SIP message. The apparatus may include means for triggering, based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
In some aspects, the apparatus may include a memory and at least one processor coupled to the memory and configured to transmit a session initiation protocol (SIP) message. The at least one processor may be configured to initiate a timer based at least in part on the transmission of the SIP message. The at least one processor may be configured to trigger, based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
In some aspects, the computer program product may include a non-transitory computer-readable medium storing computer executable code for wireless communication. The code may include code for transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message. The code may include code for initiating, by the UE, a timer based at least in part on the transmission of the SIP message. The code may include code for triggering, by the UE and based at least in part on expiration of the timer, at least one of: a radio link failure (RLF) procedure
for cell selection, or an out of service (OOS) procedure for radio access technology (RAT) selection.
FIG. 1 is a diagram illustrating an example of a network architecture.
FIG. 2 is a diagram illustrating an example of an access network.
FIG. 3 is a diagram illustrating an example of a DL frame structure in LTE.
FIG. 4 is a diagram illustrating an example of an UL frame structure in LTE.
FIG. 5 is a diagram illustrating an example of a radio protocol architecture for the user and control planes.
FIG. 6 is a diagram illustrating an example of an evolved Node B and user equipment in an access network.
FIG. 7 is a diagram illustrating an example system configured to reduce call delays using a SIP message timer.
FIG. 8 is a diagram illustrating another example system configured to reduce call delays using a SIP message timer.
FIG. 9 is a flow chart of a method of wireless communication.
FIG. 10 is a conceptual data flow diagram illustrating the data flow between different modules/means/components in an example apparatus.
FIG. 11 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.
The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.
By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. 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.
Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , compact disk ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.
FIG. 1 is a diagram illustrating an LTE network architecture 100. The LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS 100 may include one or more user equipment (UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, and an Operator’s Internet Protocol (IP) Services 122. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.
The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108, and may include a Multicast Coordination Entity (MCE) 128. The eNB 106 provides user and control planes protocol terminations toward the UE 102. The eNB 106 may be connected to the other eNBs 108 via a backhaul (e.g., an X2 interface) . The MCE 128 allocates time/frequency radio resources for evolved Multimedia Broadcast Multicast Service (MBMS) (eMBMS) , and determines the radio configuration (e.g., a modulation and coding scheme (MCS) ) for the eMBMS. The MCE 128 may be a separate entity or part of the eNB 106. The eNB 106 may also be referred to as a base station, a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , or some other suitable terminology. The eNB 106 provides an access point to the EPC 110 for a UE 102. Examples of UEs 102 include a cellular phone, a smart phone, a session initiation 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 camera, a game console, a tablet, or any other similar functioning device. The UE 102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, 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.
The eNB 106 is connected to the EPC 110. The EPC 110 may include a Mobility Management Entity (MME) 112, a Home Subscriber Server (HSS) 120, other
MMEs 114, a Serving Gateway 116, a Multimedia Broadcast Multicast Service (MBMS) Gateway 124, a Broadcast Multicast Service Center (BM-SC) 126, and a Packet Data Network (PDN) Gateway 118. The MME 112 is the control node that processes the signaling between the UE 102 and the EPC 110. Generally, the MME 112 provides bearer and connection management. All user IP packets are transferred through the Serving Gateway 116, which itself is connected to the PDN Gateway 118. The PDN Gateway 118 provides UE IP address allocation as well as other functions. The PDN Gateway 118 and the BM-SC 126 are connected to the IP Services 122. The IP Services 122 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service (PSS) , and/or other IP services. The BM-SC 126 may provide functions for MBMS user service provisioning and delivery. The BM-SC 126 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a PLMN, and may be used to schedule and deliver MBMS transmissions. The MBMS Gateway 124 may be used to distribute MBMS traffic to the eNBs (e.g., 106, 108) belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.
FIG. 1 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 1.
FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture. In this example, the access network 200 is divided into a number of cellular regions (cells) 202. One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202. The lower power class eNB 208 may be a femto cell (e.g., home eNB (HeNB) ) , pico cell, micro cell, or remote radio head (RRH) . The macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point to the EPC 110 for all the UEs 206 in the cells 202. There is no centralized controller in this example of an access network 200, but a centralized controller may be used in alternative configurations. The eNBs 204 are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway 116. An eNB may support one or multiple (e.g., three) cells (also referred to as a sectors) . The term
“cell” can refer to the smallest coverage area of an eNB and/or an eNB subsystem serving a particular coverage area. Further, the terms “eNB, ” “base station, ” and “cell” may be used interchangeably herein.
The modulation and multiple access scheme employed by the access network 200 may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support both frequency division duplex (FDD) and time division duplex (TDD) . As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) . EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.
The eNBs 204 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs 204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data streams may be transmitted to a single UE 206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE (s)
206 with different spatial signatures, which enables each of the UE (s) 206 to recover the one or more data streams destined for that UE 206. On the UL, each UE 206 transmits a spatially precoded data stream, which enables the eNB 204 to identify the source of each spatially precoded data stream.
Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.
In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR) .
FIG. 2 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 2.
FIG. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, for a normal cyclic prefix, a resource block contains 12 consecutive subcarriers in the frequency domain and 7 consecutive OFDM symbols in the time domain, for a total of 84 resource elements. For an extended cyclic prefix, a resource block contains 12 consecutive subcarriers in the frequency domain and 6 consecutive OFDM symbols in the time domain, for a total of 72 resource elements. Some of the resource elements, indicated as R 302, 304, include DL reference signals (DL-RS) . The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted on the resource blocks upon which the corresponding
physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.
FIG. 3 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 3.
FIG. 4 is a diagram 400 illustrating an example of an UL frame structure in LTE. The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.
A UE may be assigned resource blocks 410a, 410b in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks 420a, 420b in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency.
A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) 430. The PRACH 430 carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make a single PRACH attempt per frame (10 ms) .
FIG. 4 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 4.
FIG. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer 506. Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and eNB over the physical layer 506.
In the user plane, the L2 layer 508 includes a media access control (MAC) sublayer 510, a radio link control (RLC) sublayer 512, and a packet data convergence protocol (PDCP) 514 sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer 508 including a network layer (e.g., IP layer) that is terminated at the PDN gateway 118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .
The PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) . The MAC sublayer 510 provides multiplexing between logical and transport channels. The MAC sublayer 510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 510 is also responsible for HARQ operations.
In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 506 and the L2 layer 508 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer 516 in Layer 3 (L3 layer) . The RRC sublayer 516 is responsible for obtaining radio resources (e.g., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.
FIG. 5 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 5.
FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650 in an access network. In the DL, upper layer packets from the core network are provided to a controller/processor 675. The controller/processor 675 implements the functionality of the L2 layer. In the DL, the controller/processor 675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 650 based on various priority metrics. The controller/processor 675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 650.
The transmit (TX) processor 616 implements various signal processing functions for the L1 layer (i.e., physical layer) . The signal processing functions include coding and interleaving to facilitate forward error correction (FEC) at the UE 650 and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 674 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 650. Each spatial stream may then be provided to a different antenna 620 via a separate transmitter 618TX. Each transmitter 618TX may modulate an RF carrier with a respective spatial stream for transmission.
At the UE 650, each receiver 654RX receives a signal through its respective antenna 652. Each receiver 654RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 656. The RX processor 656 implements various signal processing functions of the L1 layer. The RX processor 656 may perform spatial processing on the information to recover any spatial streams destined for the UE 650. If multiple spatial streams are destined for the UE 650, they may be combined by the RX processor 656 into a single OFDM symbol
stream. The RX processor 656 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 610. These soft decisions may be based on channel estimates computed by the channel estimator 658. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 610 on the physical channel. The data and control signals are then provided to the controller/processor 659.
The controller/processor 659 implements the L2 layer. The controller/processor can be associated with a memory 660 that stores program codes and data. The memory 660 may be referred to as a computer-readable medium. In the UL, the controller/processor 659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink 662, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink 662 for L3 processing. The controller/processor 659 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.
In the UL, a data source 667 is used to provide upper layer packets to the controller/processor 659. The data source 667 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB 610, the controller/processor 659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 610. The controller/processor 659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 610.
Channel estimates derived by a channel estimator 658 from a reference signal or feedback transmitted by the eNB 610 may be used by the TX processor 668 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 668 may be provided to different
antenna 652 via separate transmitters 654TX. Each transmitter 654TX may modulate an RF carrier with a respective spatial stream for transmission.
The UL transmission is processed at the eNB 610 in a manner similar to that described in connection with the receiver function at the UE 650. Each receiver 618RX receives a signal through its respective antenna 620. Each receiver 618RX recovers information modulated onto an RF carrier and provides the information to a RX processor 670. The RX processor 670 may implement the L1 layer.
The controller/processor 675 implements the L2 layer. The controller/processor 675 can be associated with a memory 676 that stores program codes and data. The memory 676 may be referred to as a computer-readable medium. In the UL, the controller/processor 675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 650. Upper layer packets from the controller/processor 675 may be provided to the core network. The controller/processor 675 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.
FIG. 6 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 6.
When a UE is experiencing poor network conditions, an eNB may be unable to receive a SIP message sent by the UE, such as a SIP INVITE message used to set up a Voice over Long Term Evolution (VoLTE) call. In this case, the UE may perform a Circuit Switched Fallback (CSFB) procedure to connect to a different RAT (other than LTE) and set up the call. The UE may use a CSFB timer to trigger the CSFB procedure, and there may be a relatively long delay at the UE to detect such a failure using the CSFB timer. Further, performing the CSFB procedure to set up the call using a RAT other than LTE may cause additional delay. Implementations described herein reduce call setup delay using a SIP message timer that triggers selection of another LTE cell via a radio link failure (RLF) procedure, or that triggers selection of another RAT via an out of service (OOS) procedure. In this way, call setup delays may be reduced and a user experience may be enhanced.
FIG. 7 is a diagram illustrating an example system 700 configured to reduce call delays using a SIP message timer. FIG. 7 relates to an example where expiration of the SIP message timer triggers cell selection via an RLF procedure.
As shown in FIG. 7, example system 700 may include a UE 710 (e.g., which may include one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, etc. ) , an eNB 720-a (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, etc. ) associated with a cell 730-a, and an eNB 720-b (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, etc. ) associated with a cell 730-b. As an example, the UE 710 may be camped on the cell 730-a of the eNB 720-a.
As shown by reference number 740, the UE 710 may transmit a SIP message. For example, the SIP message may be a SIP INVITE message used to set up a call, such as a VoLTE call. In some aspects, the SIP message may be another type of SIP message, such as a SIP REFER message, a SIP re-INVITE message, or the like.
As shown by reference number 750, the eNB 720-a, with which the UE 710 is in communication, may fail to receive the SIP INVITE message. For example, the eNB 720-a may fail to receive the SIP INVITE message due to poor network conditions or another adverse scenario.
As shown by reference number 760, to reduce call setup delays caused by failure of the eNB 720-a to receive the SIP INVITE message, the UE 710 may initiate a timer based at least in part on transmission of the SIP message (e.g., the SIP INVITE message) . In some aspects, this timer may be referred to as a SIP message timer because the timer may be initiated by the UE 710 based at least in part on the transmission of the SIP message. In some aspects, the SIP message timer may be initiated and/or monitored by an access stratum (AS) layer of the UE 710.
As shown by reference number 770, upon expiration of the SIP message timer, the UE 710 may trigger a radio link failure (RLF) procedure for cell selection (or reselection) . In this case, the UE 710 may perform the RLF procedure to connect to another cell, such as cell 730-b of eNB 720-b, and may retry call setup of the VoLTE call using the selected cell. In this way, the UE 710 may reduce delays associated with setting up the call, thereby improving a user experience and conserving computing and network resources.
In some aspects, the UE 710 may be connected to a first cell (e.g., cell 730-a) using a RAT (e.g., LTE) . The UE 710 may determine that a second cell of the RAT (e.g., another LTE cell, such as cell 730-b) satisfies a condition, such as a handover condition, a reselection condition, a signal quality condition (e.g., the second cell
730-b has a threshold signal quality at the UE 710) , a signal strength condition (e.g., the second cell 730-b has a threshold signal strength at the UE 710) , or the like. For example, the UE 710 may determine whether another LTE cell is available, whether a better LTE cell (e.g., an LTE cell with a higher signal strength, signal quality, etc. ) than the current LTE cell is available, or the like. The UE 710 may trigger the RLF procedure to select the second cell of the RAT (e.g., cell 730-b) based at least in part on determining that the second cell of the RAT satisfies the condition. In this way, the UE 710 may avoid connecting to the second cell 730-b when the second cell 730-b will provide a poor user experience or will waste resources (e.g., due to poor signal quality, poor signal strength, etc. ) .
While shown in FIG. 7 as performing cell reselection to transition from a first cell of a first eNB to a second cell of a second eNB, in some aspects, the UE 710 may perform cell reselection to transition from a first cell of a first eNB to a second cell of the first eNB. For example, in a carrier aggregation scenario, the UE 710 may select another cell of the same eNB by performing the RLF procedure (e.g., may select a cell that provides a better connection than a current cell on which the UE 710 is camped) .
Further, while the eNB 720-a is shown as failing to receive the SIP message from the UE 710, in some aspects, the eNB 720-a may successfully receive the SIP message from the UE 710. In this case, the eNB 720-a may transmit a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message (e.g., a SIP ACK message) to the UE 710. Upon receipt of the RLC ACK message, the UE 710 may stop the SIP message timer. In this way, the UE 710 may prevent the RLF procedure from being performed when the SIP message is successfully received by the eNB 720-a, thereby conserving computing resources and network resources. In some aspects, the UE 710 may not receive the RLC ACK (e.g., due to poor network conditions) . In this case, the SIP message timer may continue to run, and expiration of the SIP message timer may trigger the UE 710 to perform the RLF procedure to reduce call setup delays under poor network conditions.
In some aspects, the UE 710 may also initiate another timer based at least in part on the transmission of the SIP message. This timer may be referred to as CSFB timer because expiration of this timer may trigger a CSFB procedure. In some aspects, the SIP message timer may have a shorter duration than the CSFB timer, thereby reducing delays in call setup that would otherwise require the UE 710 to wait until
expiration of the CSFB timer. Furthermore, use of the SIP message timer may improve a user experience by keeping the UE 710 connected to a higher priority RAT (e.g., an LTE RAT rather than a GSM RAT) . In some aspects, the UE 710 may monitor the CSFB timer in the IMS layer of the UE 710, and may monitor the SIP message timer in the AS layer of the UE 710.
As indicated above, FIG. 7 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 7.
FIG. 8 is a diagram illustrating another example system 800 configured to reduce call delays using a SIP message timer. FIG. 8 relates to an example where expiration of the SIP message timer triggers RAT selection via an OOS procedure.
As shown in FIG. 8, example system 800 may include a UE 810 (e.g., which may include one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, the UE 710 of FIG. 7, etc. ) , an eNB 820 (e.g., which may include one or more of the eNBs 106, 108 of FIG. 1, the eNBs 204, 208 of FIG. 2, the eNB 610 of FIG. 6, the eNB 720-a, 720-b of FIG. 7, etc. ) associated with a GSM cell 830 and an LTE cell 840. As an example, the UE 810 may be camped on the LTE cell 840 of the eNB 820.
As shown by reference number 850, the UE 810 may transmit a SIP message. For example, the SIP message may be a SIP INVITE message used to set up a call, such as a VoLTE call. In some aspects, the SIP message may be another type of SIP message, such as a SIP REFER message, a SIP re-INVITE message, or the like.
As shown by reference number 860, the eNB 820, with which the UE 810 is in communication via the LTE cell 840, may fail to receive the SIP INVITE message via the LTE cell 840. For example, the eNB 820 may fail to receive the SIP INVITE message due to poor network conditions or another adverse scenario associated with the LTE cell 840. In some aspects, the UE 810 may not receive an RLC ACK from the eNB 820 (e.g., due to poor network conditions) . In this case, the SIP message timer may continue to run, and expiration of the SIP message timer may trigger the UE 810 to perform the OOS procedure to reduce call setup delays under poor network conditions.
As shown by reference number 870, to reduce call setup delays caused by failure of the eNB 820 to receive the SIP INVITE message, the UE 810 may initiate a SIP message timer based at least in part on transmission of the SIP message (e.g., the SIP INVITE message) , as described above in connection with FIG. 7.
As shown by reference number 880, upon expiration of the SIP message timer, the UE 810 may trigger an out of service (OOS) procedure for RAT selection (or reselection) . In this case, the UE 810 may perform the OOS procedure to connect to another RAT, such as a GSM RAT (e.g., GSM cell 830 of eNB 820) , and may retry call setup using the selected RAT. In this way, the UE 810 may reduce delays associated with setting up the call, thereby improving a user experience and conserving computing and network resources.
In some aspects, the UE 810 may be connected to a first cell using a first RAT, such as LTE cell 840. The UE 810 may determine that no cells of the first RAT (e.g., no other LTE cells, such as the multiple cells 730-a and 730-b of FIG. 7) satisfy a condition, such as a handover condition, a reselection condition, a signal quality condition, a signal strength condition, or the like. For example, the UE 810 may determine that no other LTE cells are available, that no LTE cells with better signal conditions (e.g., higher signal strength, higher signal quality, etc. ) than the current LTE cell are available, or the like. The UE 810 may trigger the OOS procedure to select a second RAT (e.g., GSM cell 830) based at least in part on determining that no cells of the first RAT satisfy the condition. In this way, the UE 810 may avoid connecting to a cell that would provide a poor user experience or will waste resources (e.g., due to poor signal quality, poor signal strength, etc. ) .
While shown in FIG. 8 as performing RAT reselection to transition from a first cell of a first eNB to a second cell of the first eNB, in some aspects, the UE 810 may perform RAT reselection to transition from a first cell of a first eNB to a second cell of a second eNB. For example, the UE 710 may select another eNB that supports the second RAT (e.g., may select an eNB that provides a better connection than a current eNB on which the UE 810 is camped) . In some aspects, the first eNB may be provide network access using an LTE RAT, and the second eNB may provide network access using a GSM RAT.
Further, while the eNB 820 is shown as failing to receive the SIP message from the UE 810, in some aspects, the eNB 820 may successfully receive the SIP message from the UE 810, and may transmit an RLC ACK message to the UE 810, which may cause the UE 810 to stop the SIP message timer, as described above in connection with FIG. 7. Additionally, or alternatively, the UE 810 may initiate a CSFB timer based at least in part on the transmission of the SIP message, as described above in connection with FIG. 7.
As indicated above, FIG. 8 is provided as an example. Other examples are possible and may differ from what was described in connection with FIG. 8.
FIG. 9 is a flow chart 900 of a method of wireless communication. In some aspects, the method may be performed by a UE (e.g., one or more of the UE 102 of FIG. 1, the UE 206 of FIG. 2, the UE 650 of FIG. 6, the UE 710 of FIG. 7, the UE 810 of FIG. 8, the apparatus 1002 of FIG. 10, the apparatus 1002′of FIG. 11, etc. ) .
At 902, the UE may transmit a SIP message. For example, the UE may transmit a SIP message intended for an eNB. In some aspects, the SIP message may include a SIP INVITE message associated with setting up a VoLTE call.
At 904, the UE may initiate a timer based at least in part on the transmission of the SIP message. For example, the UE may detect the transmission of the SIP message (e.g., at an access stratum layer of the UE) , and may initiate a timer (e.g., a SIP message timer) based at least in part on the transmission of the SIP message. In some aspects, this timer may trigger an RLF procedure or an OOS procedure upon expiration, as described in more detail elsewhere herein. In some aspects, this timer may be referred to as a SIP message timer, and may be different from a CSFB timer that triggers a CSFB procedure upon expiration. For example, the SIP message timer may be initiated independently of the CSFB timer, may have a shorter duration than the CSFB timer, may be initiated and/or monitored at a different layer than the CSFB timer (e.g., the SIP message timer may be monitored at an access stratum layer, and the CSFB timer may be monitored at an IMS layer) , or the like. In some aspects, the UE may stop the timer based at least in part on receiving an RLC ACK message associated with the transmitted SIP message.
At 906, the UE may determine whether a condition is satisfied for a RAT to which the UE is connected. For example, the UE may be connected to a cell using a RAT, and may determine whether a condition is satisfied for the RAT. The condition may include, for example, whether there is another available cell of the RAT (e.g., whether any cells satisfy a handover condition, a reselection condition, a signal quality condition, a signal strength condition, or the like) . Upon expiration of the timer, the UE may trigger an RLF procedure or an OOS procedure based at least in part on whether the condition is satisfied, as described below.
At 908, if the condition is satisfied, then the UE may trigger, based at least in part on expiration of the timer, an RLF procedure for cell selection. For example, the UE may be connected to a first cell using a first RAT. The UE may determine that a
second cell of the first RAT satisfies a condition, and may trigger the RLF procedure to select the second cell of the first RAT based at least in part on determining that the second cell of the first RAT satisfies the condition. As another example, the UE may be connected to a cell using a RAT. The UE may determine whether there are any available cells of the RAT, and may selectively trigger the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT. For example, the UE may trigger the RLF procedure when there is at least one available cell of the RAT.
At 910, if the condition is not satisfied, then the UE may trigger, based at least in part on expiration of the timer, an OOS procedure for RAT selection. For example, the UE may be connected to a first cell using a first RAT. The UE may determine that no cells of the first RAT satisfy a condition, and may trigger the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition. As another example, the UE may be connected to a cell using a RAT. The UE may determine whether there are any available cells of the RAT, and may selectively trigger the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT. For example, the UE may trigger the OOS procedure when there are not any available cells of the RAT. In this way, the UE may reduce call setup delays associated with setting up a VoLTE call, and/or may reduce delays associated with one or more other procedures that involve SIP messaging.
Although FIG. 9 shows example blocks of a method of wireless communication, in some aspects, the method may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those shown in FIG. 9. Additionally, or alternatively, two or more blocks shown in FIG. 9 may be performed in parallel.
FIG. 10 is a conceptual data flow diagram 1000 illustrating the data flow between different modules/means/components in an example apparatus 1002. The apparatus may be a UE, such as the UE 102, the UE 206, the UE 650, the UE 710, the UE 810, or the like. As shown, the apparatus includes a transmission module 1004, an initiation module 1006, a triggering module 1008, a determining module 1010, and a reception module 1012.
The transmission module 1004 may transmit data 1014, which may include a SIP message, as described in more detail elsewhere herein. In some aspects, the apparatus 1002 may transmit the data 1014 as output to an eNB 1050 (e.g., which
may include one or more of the eNBs described elsewhere herein) . As shown, the transmission module 1004 may provide data 1016 to initiation module 1006. Data 1016 may include an indication that the SIP message was transmitted Additionally, or alternatively, initiating module 1006 may monitor for the transmission of data 1014 (e.g., the SIP message) .
The initiation module 1006 may initiate a timer (e.g., a SIP message timer) based at least in part on the transmission of the SIP message. The initiation module 1006 may provide information regarding the timer to triggering module 1008 as data 1018. Triggering module 1008 may monitor the timer (e.g., at an access stratum layer of the apparatus 1002) , and may trigger, based at least in part on expiration of the timer, at least one of an RLF procedure for cell selection, or an OOS procedure for RAT selection. Triggering module 1018 may output data 1020 to transmission module 1004 to trigger the RLF procedure or the OSS procedure (e.g., to cause the transmission module 1004 to initiate the RLF procedure or the OOS procedure by providing data 1014 to eNB 1050) . In some aspects, the initiation module 1006 may provide information regarding the timer to the determining module 1010 as data 1022.
The determining module 1010 may determine whether a condition is satisfied for a RAT. In some aspects, upon expiration of the timer, the determining module 1010 may obtain data 1024 from the reception module 1012, and may determine whether the condition is satisfied based at least in part on the data 1024 (e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc. ) . The determining module 1010 may provide an indication regarding whether the condition is satisfied to triggering module 1008 as data 1028. The triggering module 1008 may use the data 1028 and/or the data 1018 to trigger the RLF procedure or the OOS procedure, and may provide data 1020 to the transmission module 1004 regarding which procedure is to be performed.
The reception module 1012 may receive data 1026 (e.g., a handover parameter, a reselection parameter, a signal quality parameter, a signal strength parameter, etc. ) from one or more eNBs 1050, may process the data 1026 to form data 1024, and may output the data 1024 to the determining module 1010. In some aspects, the reception module 1012 may provide data 1030 to initiation module 1006 to stop the SIP message timer. For example, the data 1026 received from eNB 1050 may include an RLC ACK message and, as a result, the reception module 1012 may
provide an instruction to stop the SIP message timer to the initiation module 1006 as data 1030.
The apparatus may include additional modules that perform each of the blocks of the algorithm in the aforementioned flow chart of FIG. 9. As such, each block in the aforementioned flow chart of FIG. 9 may be performed by a module and the apparatus may include one or more of those modules. The modules may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.
The number and arrangement of modules shown in FIG. 10 are provided as an example. In practice, there may be additional modules, fewer modules, different modules, or differently arranged modules than those shown in FIG. 10. Furthermore, two or more modules shown in FIG. 10 may be implemented within a single module, or a single module shown in FIG. 10 may be implemented as multiple, distributed modules. Additionally, or alternatively, a set of modules (e.g., one or more modules) shown in FIG. 10 may perform one or more functions described as being performed by another set of modules shown in FIG. 10.
FIG. 11 is a diagram 1100 illustrating an example of a hardware implementation for an apparatus 1002′employing a processing system 1102. The processing system 1102 may be implemented with a bus architecture, represented generally by the bus 1104. The bus 1104 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1102 and the overall design constraints. The bus 1104 links together various circuits including one or more processors and/or hardware modules, represented by the processor 1106, the modules 1004, 1006, 1008, 1010, 1012, and the computer-readable medium /memory 1108. The bus 1104 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits.
The processing system 1102 may be coupled to a transceiver 1110. The transceiver 1110 is coupled to one or more antennas 1112. The transceiver 1110 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1110 receives a signal from the one or more antennas 1112, extracts information from the received signal, and provides the extracted information to the processing system 1102, specifically the reception module 1012. In addition, the
transceiver 1110 receives information from the processing system 1102, specifically the transmission module 1004, and based on the received information, generates a signal to be applied to the one or more antennas 1112.
The processing system 1102 includes a processor 1106 coupled to a computer-readable medium /memory 1108. The processor 1106 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1108. The software, when executed by the processor 1106, causes the processing system 1102 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1108 may also be used for storing data that is manipulated by the processor 1106 when executing software. The processing system further includes at least one of the modules 1004, 1006, 1008, 1010, 1012. The modules may be software modules running in the processor 1106, resident/stored in the computer readable medium /memory 1108, one or more hardware modules coupled to the processor 1106, or some combination thereof. The processing system 1102 may be a component of the UE 650 and may include the memory 660 and/or at least one of the TX processor 668, the RX processor 656, and the controller/processor 659.
In one configuration, the apparatus 1002/1002′for wireless communication includes means for transmitting a SIP message, means for initiating a timer based at least in part on the transmission of the SIP message, means for triggering at least one of an RLF procedure for cell selection or an OOS procedure for RAT selection, means for determining whether a condition is satisfied for a RAT, means for selectively triggering the RLF procedure or the OOS procedure based at least in part on determining whether the condition is satisfied for the RAT, and/or means for stopping the timer. The aforementioned means may be one or more of the aforementioned modules of the apparatus 1002 and/or the processing system 1102 of the apparatus 1002′configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1102 may include the TX Processor 668, the RX Processor 656, and the controller/processor 659. As such, in one configuration, the aforementioned means may be the TX Processor 668, the RX Processor 656, and the controller/processor 659 configured to perform the functions recited by the aforementioned means.
It is understood that the specific order or hierarchy of blocks in the processes /flow charts disclosed is an illustration of exemplary approaches. Based upon design
preferences, it is understood that the specific order or hierarchy of blocks in the processes /flow charts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.
The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “at least one of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “at least one of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”
Claims (30)
- A method of wireless communication, comprising:transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message;initiating, by the UE, a timer based at least in part on the transmission of the SIP message; andtriggering, by the UE and based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, oran out of service (OOS) procedure for radio access technology (RAT) selection.
- The method of claim 1, wherein the SIP message is a SIP INVITE message associated with setting up a voice over long term evolution (VoLTE) call.
- The method of claim 1, wherein the UE is connected to a first cell using a RAT;wherein the method further comprises determining that a second cell of the RAT satisfies a condition; andwherein the triggering comprises triggering the RLF procedure to select the second cell of the RAT based at least in part on determining that the second cell of the RAT satisfies the condition.
- The method of claim 1, wherein the UE is connected to a cell using a first RAT;wherein the method further comprises determining that no cells of the first RAT satisfy a condition; andwherein the triggering comprises triggering the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition.
- The method of claim 1, wherein the UE is connected to a cell using a RAT;wherein the method further comprises determining whether there are any available cells of the RAT; andwherein the triggering comprises selectively triggering the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT,wherein the RLF procedure is triggered when there is at least one available cell of the RAT, andwherein the OOS procedure is triggered when there are not any available cells of the RAT.
- The method of claim 1, further comprising:stopping the timer based at least in part on receiving a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message.
- The method of claim 1, wherein the timer is monitored by an access stratum (AS) layer of the UE.
- The method of claim 1, wherein the timer has a shorter duration than a circuit switched fallback timer used to trigger circuit switched fallback for the UE.
- An apparatus for wireless communication, comprising:means for transmitting a session initiation protocol (SIP) message;means for initiating a timer based at least in part on the transmission of the SIP message; andmeans for triggering, based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, oran out of service (OOS) procedure for radio access technology (RAT) selection.
- The apparatus of claim 9, wherein the SIP message is a SIP INVITE message associated with setting up a voice over long term evolution (VoLTE) call.
- The apparatus of claim 9, wherein the apparatus is connected to a first cell using a RAT;wherein the apparatus further comprises means for determining that a second cell of the RAT satisfies a condition; andwherein the means for triggering comprises means for triggering the RLF procedure to select the second cell of the RAT based at least in part on determining that the second cell of the RAT satisfies the condition.
- The apparatus of claim 9, wherein the apparatus is connected to a first cell using a first RAT;wherein the apparatus further comprises means for determining that no cells of the first RAT satisfy a condition; andwherein the means for triggering comprises means for triggering the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition.
- The apparatus of claim 9, wherein the apparatus is connected to a cell using a RAT;wherein the apparatus further comprises means for determining whether there are any available cells of the RAT; andwherein the means for triggering comprises means for selectively triggering the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT,wherein the RLF procedure is triggered when there is at least one available cell of the RAT, andwherein the OOS procedure is triggered when there are not any available cells of the RAT.
- The apparatus of claim 9, further comprising:means for stopping the timer based at least in part on receiving a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message.
- The apparatus of claim 9, wherein the timer is monitored by an access stratum (AS) layer of the apparatus.
- The apparatus of claim 9, wherein the timer has a shorter duration than a circuit switched fallback timer used to trigger circuit switched fallback for the apparatus.
- An apparatus for wireless communication, comprising:a memory; andat least one processor coupled to the memory and configured to:transmit a session initiation protocol (SIP) message;initiate a timer based at least in part on the transmission of the SIP message; andtrigger, based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, oran out of service (OOS) procedure for radio access technology (RAT) selection.
- The apparatus of claim 17, wherein the SIP message is a SIP INVITE message associated with setting up a voice over long term evolution (VoLTE) call.
- The apparatus of claim 17, wherein the apparatus is connected to a first cell using a RAT;wherein the at least one processor is further configured to determine that a second cell of the RAT satisfies a condition; andwherein the at least one processor, when triggering the RLF procedure, is configured to trigger the RLF procedure to select the second cell of the RAT based at least in part on determining that the second cell of the RAT satisfies the condition.
- The apparatus of claim 17, wherein the apparatus is connected to a first cell using a first RAT;wherein the at least one processor is further configured to determine that no cells of the first RAT satisfy a condition; andwherein the at least one processor, when triggering the RLF procedure, is configured to trigger the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition.
- The apparatus of claim 17, wherein the apparatus is connected to a cell using a RAT;wherein the at least one processor is further configured to determine whether there are any available cells of the RAT; andwherein the at least one processor, when triggering the RLF procedure, is configured to selectively trigger the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT,wherein the RLF procedure is triggered when there is at least one available cell of the RAT, andwherein the OOS procedure is triggered when there are not any available cells of the RAT.
- The apparatus of claim 17, wherein the at least one processor is further configured to:stop the timer based at least in part on receiving a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message.
- The apparatus of claim 17, wherein the timer is monitored by an access stratum (AS) layer of the apparatus.
- A non-transitory computer-readable medium storing computer executable code for wireless communication, comprising code for:transmitting, by a user equipment (UE) , a session initiation protocol (SIP) message;initiating, by the UE, a timer based at least in part on the transmission of the SIP message; andtriggering, by the UE and based at least in part on expiration of the timer, at least one of:a radio link failure (RLF) procedure for cell selection, oran out of service (OOS) procedure for radio access technology (RAT) selection.
- The non-transitory computer-readable medium of claim 24, wherein the SIP message is a SIP INVITE message associated with setting up a voice over long term evolution (VoLTE) call.
- The non-transitory computer-readable medium of claim 24, wherein the UE is connected to a first cell using a RAT;wherein the code further comprises code for determining that a second cell of the RAT satisfies a condition; andwherein the code for triggering comprises code for triggering the RLF procedure to select the second cell of the RAT based at least in part on determining that the second cell of the RAT satisfies the condition.
- The non-transitory computer-readable medium of claim 24, wherein the UE is connected to a first cell using a first RAT;wherein the code further comprises code for determining that no cells of the first RAT satisfy a condition; andwherein the code for triggering comprises code for triggering the OOS procedure to select a second RAT based at least in part on determining that no cells of the first RAT satisfy the condition.
- The non-transitory computer-readable medium of claim 24, wherein the UE is connected to a cell using a RAT;wherein the code further comprises code for determining whether there are any available cells of the RAT; andwherein the code for triggering comprises code for selectively triggering the RLF procedure or the OOS procedure based at least in part on determining whether there are any available cells of the RAT,wherein the RLF procedure is triggered when there is at least one available cell of the RAT, andwherein the OOS procedure is triggered when there are not any available cells of the RAT.
- The non-transitory computer-readable medium of claim 24, further comprising code for:stopping the timer based at least in part on receiving a radio link control (RLC) acknowledgement (ACK) message associated with the SIP message.
- The non-transitory computer-readable medium of claim 24, wherein the timer is monitored by an access stratum (AS) layer of the UE.
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