Patent ID: 12193075

DETAILED DESCRIPTION

The example embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The description herein is intended merely to facilitate an understanding of ways in which the example embodiments herein can be practiced and to further enable those of skill in the art to practice the example embodiments herein. Accordingly, this disclosure should not be construed as limiting the scope of the example embodiments herein.

Embodiments herein disclose methods and systems for handling multiple Random Access Channel (RACH) procedures.

A method according to various embodiments enables the DAPS feature to handle simultaneous multiple RACH, thereby leading to faster RACH handling. The method according to various embodiments enables the DAPS feature to simultaneously attempt to connect to multiple beams or cells when multiple beams of cells satisfy the selection criteria.

A method according to various embodiments can be used to enhance the user experience and reduce delay in second RACH using processing 2 RACH simultaneously. In a method according to various embodiments, accommodating 2 RACH at same time will help UE in many scenarios mentioned and thus help in better user experience and also avoid delay in critical data and services. A method according to various embodiments uses Dual Active protocol stack (DAPS) which will have 2 MAC entity, so each MAC entity can accommodate one RACH procedure.

In a method according to various embodiments, UE's which support DAPS mechanism can activate 2 stacks by themselves without network intervention and trigger RACH on 2 different beams, which will help a UE to overcome from temporary issues on some beams, and thus enable a UE to compete the RACH procedure at a faster rate.

For latency critical applications, performing RACH on 2 different beams will help to recover from beam failure with reduced latency, resume the services as soon as possible, and benefit UE to completed RACH earlier on one of the beam. Also accessing 2 different cells at same time is made possible, even if RACH is failing on one cell or there is extra delay on one of the cells, then UE can (re) gain services if RACH is successful on one cell. Also, in un-licensed spectrum this solution will be very helpful as there can be LBT (listen before talk) failure on one beam but other beam RACH can be successful due to the nature of devices working on un-licensed spectrum.

Various example embodiments are shown with reference to the drawings, and more particularly toFIGS.3A through22, where similar reference characters denote corresponding features consistently throughout the figures.

FIGS.3A,3B, and3Cdepict an example wireless network300, according to various embodiments herein. The wireless network300includes a plurality of Base Stations302, and a plurality of User Equipments (UEs)304.

The BS(s)/network302may be a radio node configured to communicate with the one or more UEs304and connect the one or more UEs304with a core network (not shown) for communication services. The BS302may communicate with the one or more UEs304via a same or different Radio Access Technologies (RATs). Examples of the RATs may be, but are not limited to, a Third Generation Partnership 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE/4G), an LTE-Advanced (LTE-A), a Fifth Generation (5G) New Radio, a 6G wireless system, a Wireless Local Area Network (WLAN), a Worldwide Interoperability for Microwave Access (WiMAX/IEEE 802.16), a Wi-Fi (IEEE 802.11), an Evolved-UTRA (E-UTRA), or any other next generation network. The BS302provides at least one cell to the UE304, wherein the at least one cell indicates a geographical area in which the communication services may be offered to the UE304. The BS302may be at least one of, a macro-BS, a micro-BS, a femto-BS, a pico-BS, and so on.

The BS302of the at least one RAT may support dual connectivity (DC). In order to achieve the DC, the BS302may support a bearer split functionality. In an example herein, the BS302may act as a master node (MN) or a secondary node (SN). The MN may be the BS/node associated with the macro cell, which provides radio resources to the UE304by acting as a mobility anchor towards the core network. The SN may be the BS/node associated with the small cell/pico cell, which provides additional radio resources to the UE304. If the BS302acts as the MN, then the BS302may be associated with serving cells/carrier frequencies such as a primary carrier/Master Cell Group. If the BS302acts as the SN, then the BS302may be associated with the serving cells/carrier frequencies such as a secondary carrier/Secondary Cell Group (SCG), respectively. The MCG and the SCG may be a group of cells including a primary cell (PCell)/primary SCell (PSCell) and optionally one or more Secondary Cells (SCells).

In an example, the wireless network300may be a beam forming millimeter wave (mmWave) network, as depicted inFIGS.3B and3C. In such a scenario, the BS/cell302may transmit one or more beams to the UE304for connecting. Embodiments herein use the terms such as “BSs”, “network”, “cells”, “macro-BSs”, “pico-BSs”, “eNodeBs (eNBs)”, “gNBs”, “Radio Access Network (RAN)”, “network”, “beams”, and so on, interchangeably to refer to a Base Transceiver System (BTS)/station that communicates with the one or more UEs304.

The UE(s)304referred herein may be a user device capable of supporting the wireless network300. Examples of the UE304may be, but are not limited to, a mobile phone, a smartphone, a tablet, a phablet, a Personal Digital Assistant (PDA), a laptop, a computer, a wearable computing device, a vehicle infotainment device, an Internet of Things (IoT) device, a Wireless Fidelity (Wi-Fi) router, a USB dongle, a television, a vehicle with communication facility (for example, a connected car), or any other processing device supporting the wireless network300.

The UE304may be configured to synchronize with the at least one BS302in downlink (DL) as well as in uplink (UL), when the UE304wants to connect to the at least one BS302or the associated RAT. The UE304performs the synchronization with the BS302in the DL, on obtaining DL synchronization by successfully decoding a Synchronization Signal Block (SSB) received from the BS302. The UE304performs a Random Access Channel (RACH) procedure to establish an UL synchronization (sync) and a Radio Resource Control (RRC) connection with the BS302. The RACH procedure may include at least one of, a Contention Based Random Access (CBRA) procedure, and a Non-Contention or Contention Free Random Access (CFRA) procedure (as defined in the 3GPP specification).

In an embodiment, the UE304may be configured to handle/perform multiple RACH procedures simultaneously. In an example embodiment, the multiple RACH procedures may be same RACH procedures. In an example embodiment, the multiple RACHs procedures may be different RACH procedures.

Embodiments herein describe the handling of the multiple RACH procedures, wherein the multiple RACH procedures are different RACH procedures.

For performing the multiple RACH procedures, the UE304detects triggering of a first RACH procedure on a primary stack304a, while the UE304is connected to the at least one cell/BS302in the wireless network300. Embodiments herein use terms such as “primary stack”, “UE stack 1”, “first stack”, and so on, interchangeably through the document. The primary stack304amay include a physical layer (PHY) entity, a Medium Access Channel (MAC) layer entity, a Radio Link Control (RLC) layer entity, Packet Data Convergence Protocol (PDCP) layer entity, or the like.

In an example herein, the first RACH procedure may include at least one of, but is not limited to, a non-handover procedure, a RACH procedure triggered for UL grants and UL synchronization, or a RACH procedure triggered on the at least one cell/BS302from a Primary Timing Advance Group (pTAG) in the wireless network300, wherein the at least one cell/BS302is the primary cell/MN.

The UE304detects triggering of a second RACH procedure, while the first RACH procedure is ongoing on the primary stack304a. In an embodiment, the second RACH procedure may be different from the first RACH procedure. In an example, the second RACH procedure may be an on-demand System Information (SI) RACH procedure, when the first RACH procedure is the RACH procedure triggered for the UL grants and the UL synchronization. In another example, the second RACH procedure may be a RACH procedure triggered on a secondary cell from a Secondary Timing Advance Group (sTAG) in the wireless network300, when the first RACH procedure is the RACH procedure triggered on the primary cell from the pTAG, wherein the RACH procedure is configured with a Carrier Aggregation (CA). In another example, the second RACH procedure may be a RACH procedure triggered due to a System Information (SI) request/on-demand SI request received from the at least one cell/BS302for one or more services or based on cell reselection parameters. The SI request may be a request other than a System Information Block 1 (SIB1). Examples of the one or more services may be, but are not limited to, a Vehicle to Everything (V2X) service, a Device to Device (D2D) service, a Side link service, and so on.

In an embodiment, the second RACH may be triggered, when the UE304receives the on-demand SI request for the one or more services during the ongoing first RACH procedure. In an embodiment, the second RACH may be triggered, when the UE304has UL data to send to the cell/BS302for the UL synchronization during the ongoing first RACH procedure. In an embodiment, the second RACH procedure may be triggered, when the UE304has the UL data to send to the cell/BS302and no grants are available for the UE304to send the UL data during the ongoing first RACH procedure. In an embodiment, the second RACH procedure may be triggered on the secondary cell/SN, when the UE304configured with a UL-CA triggers the first RACH procedure on the primary cell. The primary cell and the secondary cell may have a single Medium Access Control (MAC) entity.

On detecting the second RACH procedure while the ongoing first RACH procedure, the UE304enables a Dual Active Protocol Stack (DAPS) capability to initiate/create a secondary stack304bfor handling the second RACH procedure. The UE304creates the secondary stack by configuring the secondary stack304bwith configurations of one or more entities/layers of the primary stack304a. Examples of the one or more entities/layers of the secondary stack304bmay be, but are not limited to, the physical layer entity, the MAC layer entity, the RLC layer entity (an optional layer), or the like. Embodiments herein use terms such as “secondary stack”, “UE stack 2”, “second stack”, and so on, interchangeably through the document.

The UE304shares RACH trigger configurations/RACH configurations corresponding to the second RACH procedure from the primary stack304ato the secondary stack304bto handle the second RACH procedure. The UE304receives the RACH trigger configurations corresponding to the secondary RACH procedure on the primary stack304aas part of the SIB1, or an RRC reconfiguration message, based on a trigger reason for the second RACH procedure and/or network configurations.

On sharing the RACH trigger configurations, the UE304configures the secondary stack304bfor handling the second RACH procedure. In an example, the UE304configures the secondary stack304bby providing configurations of the physical layer entity and the configurations of the MAC entity to the secondary stack304b. The UE304also shares configurations of the RLC entity from the primary stack304ato the secondary stack304b, only if the configurations of the RLC entity are required for the secondary stack304bto handle the second RACH procedure.

For an embodiment, below are parameters to configure the secondary stack304b:1. rlc-BearerToAddModList=>RLC and MAC Logicalchannel configuration is received from network using this Information Element (IE). This IE is a part of RRCReconfiguration message from a network.

For an embodiment, below are parameters shared to secondary cells for configuring secondary cell:1. mac-LogicalChannelConfig=>MAC Logical channel configuration.2. logicalChannelIdentity ID (LCDI): used for the Mapping of MAC logical channel and for the RLC bearers.3. servedRadioBearer: SRB or DRB ID for mapping to RLC layer4. rlc-Config: Contains RLC configures. Can be used if UE wants to configure RLC layer.5. PHY Layer configuration: The current serving cell ID, Frequencyband, Bandwidth, BWP details are passed on to the second stack.6. These details are part of ‘spCellConfigCommon’ IE (in case of NSA mode) or ServingCellConfigCommonSIB IE in SIB1 (in case of SA mode) which the network sends to UE.

Below are the RLC, MAC configurationRRCReconfiguration-IEs::=SEQUENCE{rlc-BearerToAddModList SEQUENCE RLC-BearerConfig}RLC-BearerConfig::=SEQUENCE {logicalChannelIdentity,servedRadioBearer CHOICE {srb-Identity SRB-Identity,drb-Identity DRB-Identity}rlc-Config RLC-Config OPTIONAL, --Cond LCH-Setupmac-LogicalChannelConfig logicalChannelConfig. . . ,}

Below is a Physical Layer config:SIB1 {ServingCellConfigCommonSIB. . .}Reconfiguration WithSync::={spCellConfigCommon ServingCellConfigCommon

Sharing RACH configuration for on-demand SI: For MSG1 based on-demand SI collision, primary stack will send the RACH configuration present in SI-RequestConfig in SIB1 to the secondary stack.1. SI-SchedulingInfo: The IE SI-SchedulingInfo contains information needed for acquisition of SI messages. This is present in sib12. SI-RequestConfig: The IE SI-RequestConfig contains configuration for Msg1 based SI request

Table 1 below describes examples of SI-RequestConfig and SI-RequestResources.

TABLE 1SI-RequestConfig ::=SEQUENCE {rach-OccasionsSISEQUENCE {rach-ConfigSIRACH-ConfigGeneric,ssb-perRACH-OccasionENUMERATED {oneEighth, oneFourth, oneHalf,one, two, four, eight, sixteen}}OPTIONAL, -- NeedRsi-RequestPeriodENUMERATED {one, two, four, six, eight, ten, twelve,sixteen} OPTIONAL, -- Need Rsi-RequestResourcesSEQUENCE (SIZE (1..maxSI-Message)) OF SI-RequestResources}SI-RequestResources ::=SEQUENCE {ra-PreambleStartIndexINTEGER (0..63),ra-AssociationPeriodIndexINTEGER (0..15)OPTIONAL, -- Need Rra-ssb-OccasionMaskIndexINTEGER (0..15)OPTIONAL -- Need R}

Sharing RACH configuration for RLF, UL SYNC, UL Grants:if rach-ConfigDedicated is not configured, ‘rach-ConfigCommon’ configuration is passed from the primary stack to secondary stack configuration. This configuration is present in SIB1.

Table 2 below describes an example of RACH-ConfigCommon.

TABLE 2RACH-ConfigCommon ::=SEQUENCE {rach-ConfigGenericRACH-ConfigGeneric,totalNumberOfRA-PreamblesINTEGER (1..63)OPTIONAL, -- Need Sssb-perRACH-OccasionAndCB-PreamblesPerSSB CHOICE {oneEighthENUMERATED{n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},oneFourthENUMERATED{n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},oneHalfENUMERATED{n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},oneENUMERATED{n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},twoENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32},fourINTEGER (1..16),eightINTEGER (1..8),sixteenINTEGER (1..4)}

IE RACH-ConfigDedicated is used to specify the dedicated random access parameters.

RACH-ConfigDedicated is passed to secondary stack if it is configured in RRCReconfiguration message inside ‘Reconfigwithsync’ IE by network.

Table 3 below describes an example of RACH-ConfigDedicated.

TABLE 3RACH-ConfigDedicated ::=SEQUENCE {cfraCFRAOPTIONAL, --Need Sra-PrioritizationRA-PrioritizationOPTIONAL,-- Need N...,[[ra-PrioritizationTwoStep-r16RA-PrioritizationOPTIONAL,-- Need Ncfra-TwoStep-r16CFRA-TwoStep-r16OPTIONAL-- Need S]]}

In case of Beam failure recovery RACH, the configuration present in ‘RACH-ConfigGeneric’ is used from BeamFailureRecoveryConfig.

The UE304may receive the configurations of the physical layer entity on the primary stack as part of a “ServingCellConfigCommonSIB” Information Element (IE) present in a System Information Block 1 (SIB1). The UE304may receive the configurations of the MAC entity on the primary stack in one of, but not limited to, a Radio Resource Configuration (RRC) message, a MAC logical channel configuration, a logical channel identity, a served radio bearer, or the like.

The UE304may also perform a bearer split at the RLC entity for mapping one or more Dedicated Radio Bearers (DRBs) to logical channels on the secondary stack304bto support the second RACH procedure.

On creating and configuring the secondary stack304b, the UE304performs the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304bsimultaneously.

The UE304disables the secondary stack upon successful completion of the second RACH procedure or the first RACH procedure. The UE304continues an ongoing second RACH procedure or the first RACH procedure on the primary stack304a.

Various example embodiments herein describe the handling of the RACH procedure in multi-beam scenarios.

The UE304detects a requirement to connect to at least one element depending on an event triggered to perform the RACH procedure by the UE304, while the UE304is connected to the at least one cell/BS302using at least one beam. In an embodiment, the at least one element refers to the cell/BS302or the beam. In an embodiment, the event triggered to perform the RACH procedure may be an event triggered to perform the RACH procedure to resume the one or more services on the at least one cell302including multiple beams. Such an event may be triggered due to at least one of, but is not limited to, a Beam Failure Recovery (BFR), an initial access, a Radio Link Failure (RLF), an UL synchronization, UL grants, or so on. In an embodiment, the event triggered to perform the RACH procedure may be an event triggered to select the cell among the plurality of different cells302, when the UE304has valid RACH configurations of the plurality of different cells.

The UE304detects a first cell/beam302and a second cell/beam302including parameters satisfying cell selection criteria, when the UE304wants to connect to the at least one cell//beam. The parameters satisfying the cell selection criteria may include at least one of, but is not limited to, cell parameters, beam parameters, or so on.

The UE304enables the DAPS capability to create/initiate the secondary stack304b. The UE304creates the secondary stack304bby sharing at least one of, but not limited to, the configurations of the physical layer entity, the configurations of the MAC entity, the RACH configuration corresponding to the RACH procedure, or preamble information from the primary stack304ato the secondary stack304b. The UE304sends a RACH request to the primary stack304aand the secondary stack304bto perform the RACH procedure to connect on the at least two cells/beams302using both the primary stack304aand the secondary stack304b.

For sharing the preamble information from the primary stack304ato the secondary stack304b, the UE304identifies a type of the RACH procedure. The RACH procedure includes one of the CFRA procedure or the CBRA procedure. Based on the identified type of the RACH procedure, the UE304shares the preamble information from the primary stack304ato the secondary stack304b.

If the RACH procedure is the CFRA procedure, the UE304shares the dedicated preamble information from the primary stack304ato the secondary stack304b. The preamble information includes an element (cell/beam) identifier (ID) of the primary stack304a, if a message 2 (MSG2) is failed at least once or Reference Signal Received Power (RSRP) is poor. The element ID includes one of a beam ID or a cell ID of the primary stack304a.

If the RACH procedure is the CBRA procedure, the UE304shares the different sets of preamble information between the primary stack304aand the secondary stack304b. In an embodiment, for sharing the different sets of preamble information between the primary stack304aand the secondary stack304b, the UE304divides content-based preambles into a first set and a second set. The UE304allocates the first set for the primary stack304aand the second set for the secondary stack304b. In an embodiment, for sharing the different sets of preamble information between the primary stack304aand the secondary stack304b, the UE304divides the content-based preambles into an even set of preambles and an odd set of preambles. The UE304allocates the even set of preambles for the primary stack304aand the odd set of preambles for the secondary stack304b. In an embodiment, for sharing the different sets of preamble information between the primary stack304aand the secondary stack304b, the UE304dynamically shares the currently used preamble information from the primary stack304ato the secondary stack304b. The UE304enables the secondary stack304bto use the shared preamble information only on receiving a subsequent notification. The preamble information includes the beam ID of the primary stack. The shared preamble information for the secondary stack is valid only until an expiry of a Random-Access Response (RAR) window.

The UE304initiates the RACH procedure on the first cell/beam302and the second cell/beam302using the primary stack304aand the secondary stack304bsimultaneously.

The UE304aborts the ongoing RACH procedure using the secondary stack304b, if the RACH procedure using the primary stack304ais completed before completion of the RACH procedure using the secondary stack304b. The UE304aborts the ongoing RACH procedure using the primary stack304a, if the RACH procedure using the secondary stack304bis completed before completion of the RACH procedure using the primary stack304a.

The UE304disables the secondary stack304b, upon successful completion of the RACH procedure using any of the primary stack304aor the secondary stack304b.

FIGS.3A,3B, and3Cshow example blocks of the wireless network300, but it is to be understood that embodiments are not limited to the blocks shown in these figures. In various embodiments, the wireless network300may include fewer or more blocks. Further, the labels or names of the blocks are used only for illustrative purposes and do not limit the scope of embodiments herein. One or more blocks may be combined together to perform same or substantially similar function in the wireless network300.

FIG.4is a block diagram depicting components of the example UE304for managing the RACH procedures, according to various embodiments. The UE304includes a memory402, a communication interface404, and/or a RACH procedures processing circuitry/controller406. The UE304may also include a Radio Frequency (RF) transceiver, signal processing circuitry, an Input/Output ports, a display, and so on (not shown).

The memory402stores information about at least one of the primary stack304a, the secondary stack304b, the RACH configurations, the configurations of the physical layer entity, the MAC layer entity, and the RLC layer entity, the preamble information, or so on. Examples of the memory402may be, but are not limited to, NAND, embedded Multimedia Card (eMMC), Secure Digital (SD) cards, Universal Serial Bus (USB), Serial Advanced Technology Attachment (SATA), solid-state drive (SSD), and so on. Further, the memory402may include one or more computer-readable storage media. The memory402may include one or more non-volatile storage elements. Examples of such non-volatile storage elements may include Random Access Memory (RAM), Read Only Memory (ROM), magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory402may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may, for example, indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted to mean that the memory is non-movable. In certain examples, a non-transitory storage medium may store data that may, over time, change (e.g., in Random Access Memory (RAM) or cache).

The communication interface404(e.g., including communication interface circuitry) may be configured to enable the UE304to communicate with at least one BS302using an interface supported by the respective RAT. Examples of the interface may be, but are not limited to, a wired interface, a wireless interface, or any structure or circuitry supporting communications over a wired or wireless connection.

The term ‘controller/processing circuitry’ may refer to, for example, hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the processing circuitry more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), etc. For example, the controller406may include at least one of a single processer, a plurality of processors, multiple homogeneous or heterogeneous cores, multiple Central Processing Units (CPUs) of different kinds, microcontrollers, special media, or other accelerators.

The controller406may be configured to handle the RACH procedures on the UE304.

In an embodiment, the controller406may handle the different RACH procedures on the UE304. The controller406detects the triggering of the first RACH procedure on the primary stack304a, while the UE304is connected to the at least one cell302in the wireless network300. The controller406detects the triggering of the second RACH procedure while the first RACH procedure is ongoing. The second RACH procedure may be different from the first RACH procedure. The controller406uses the DAPS capability to create/initiate the secondary stack304bfor handling the second RACH procedure. On creating the second RACH procedure, the controller406performs the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304bsimultaneously. The controller406disables the secondary stack304bupon successful completion of the second RACH procedure.

In an embodiment, the controller406is configured to handle the RACH procedure, while the UE304is connected to the at least one cell302using at least one beam.

The controller406detects the requirement to connect to the at least one cell/beam302depending on the event triggered to perform the RACH procedure by the UE304, while the UE304is connected to at least one cell302using the at least one beam. The controller406detects the first cell/beam and the second cell/beam including the parameters satisfying the cell selection criteria, when the UE304wants to connect to the at least one cell/beam302.

The controller406enables the DAPS capability to create/initiate the second stack304b. The controller406initiates the RACH procedure on the first cell/beam and the second cell/beam using the primary stack304aand the secondary stack304bsimultaneously. The controller406aborts the ongoing RACH procedure using the secondary stack, if the RACH procedure using the primary stack304ais completed before completion of the RACH procedure using the secondary stack or vice-versa. The controller406disables the secondary stack304b, upon successful completion of the RACH procedure using any of the primary stack304aor the secondary stack304b.

FIG.4shows example blocks of the UE304, but it is to be understood that embodiments are not limited in this respect. In various embodiments, the UE304may include fewer or more blocks. Further, the labels or names of the blocks are used only for illustrative purposes and do not limit the scope of embodiments herein. One or more blocks may be combined together to perform same or substantially similar function in the UE304.

FIG.5is a diagram depicting an example use case scenario of performing the different RACH procedures, according to various embodiments.

Consider an example scenario, wherein the UE304initiates the first RACH procedure on the primary stack304a. While the first RACH procedure is ongoing on the primary stack304a, the UE304detects the trigger for the second RACH procedure due to at least one of, the on-demand SI request, the UL grants, the UL CA scenarios, and so on.

On detecting the trigger for the second RACH procedure, the UE304creates the secondary stack304bby enabling the DAPS capability. The UE304performs the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304b, simultaneously.

FIG.6is a diagram depicting example use case scenarios of handling the second RACH procedure, on detecting the collision of the second RACH procedure with the ongoing first RACH procedure, according to various embodiments.

Consider an example scenario, wherein the RACH procedure for the UL data (i.e., the first RACH procedure) is ongoing on the primary stack (a stack 1). While the RACH procedure for the UL data is ongoing, the UE304detects the triggering of a RACH procedure for the on-demand SI (i.e., the second RACH procedure). The RACH procedure for the on-demand SI may be triggered for SIB's based configurations such as, but not limited to, side link configurations, V2X/D2D configurations, and cell reselection (intra, inter frequency, and the RAT). In such a scenario, the UE304creates the secondary stack304busing the DAPS capability. The UE304performs the RACH procedure for the UL data on the primary stack304aand the RACH procedure for the on-demand SI on the secondary stack304bsimultaneously.

Consider another example scenario, wherein the UE304initiates the RACH procedure (for example, the first RACH procedure) on the secondary cell/Scell (belonging to the sTAG) using the primary stack304a. While the RACH procedure is ongoing on the Scell, the UE304identifies the triggering of a RACH procedure on the primary cell/Pcell (belonging to the pTAG). In such a scenario, delaying the RACH procedure on the Pcell may cause delay in the services on the Pcell. For example, when the UE304requires the grants for sending the UL data on the Pcell, the UE304may not be able to send the UL data, until the completion of the ongoing RACH procedure on the Scell. When the critical data on the Pcell requires the RACH for the UL synchronization or the UL grants, and when the RACH for the Scell is ongoing, the UL data on the Pcell may be delayed till the RACH on the Scell is completed. Thus, in order to avoid delaying of the RACH procedure, the UE304creates the secondary stack304busing the DAPS capability. The UE304performs the RACH procedure on the Pcell using the secondary stack304b. Thus, helping the UE304to trigger the Pcell RACH immediately without having to wait for the Scell RACH to be completed.

FIG.7is a depicting example identification of the collision of the two RACH procedures, according to various embodiments.

When the first RACH procedure on the MAC entity has initiated/started and not completed all 4 steps of the RACH procedure (as defined the 3GPP specification) by the time the second RACH procedure is triggered on the same MAC entity (same cell or the different cell, in case of the UL-CA scenarios), the UE304identifies that initiating the second RACH procedure on the same MAC entity may lead to the RACH collision.

Also, there may be a possibility of message (MSg)1/MSg2/Msg3/Msg4 failures. In such cases, the UE304observes the multiple corresponding messages being transmitted and may take more time to complete the RACH procedure.

FIG.8AandFIG.8Bdepict an example configuring process of the secondary stack304b, according to various embodiments.

The UE304creates the secondary/new stack304busing the DAPS capability, on detecting the collision of the first RACH procedure with the second RACH procedure. In an example, the UE304may create the secondary stack304blike when the UE304is powered on. The secondary stack304bmay include the physical layer entity, the MAC layer entity, and the RLC layer entity (the optional entity). The configurations of the physical layer entity of the secondary stack304b(for example, a frequency, a band, bandwidth, a physical cell ID, Bandwidth part (BWP), and so on) may be same as the configurations of the physical layer entity on the primary stack304a. The UE304may receive the configurations of the physical layer entity as a part of a ‘ServingCellConfigCommonSIB’ IE present in ‘SIB1’ received on the primary stack304a. The UE304shares the configurations of the physical layer entity from the primary stack304ato the secondary stack304bto configure the physical layer entity on the secondary stack304b. Unlike, a handover case, where secondary stack target details are given by the network/BS302, the UE304receives the configurations of the physical layer entity from the primary stack304a.

The configurations of the MAC layer entity and the RLC entity of the secondary stack304bare same as the primary stack304a. The UE304may receive the configurations of the MAC layer entity, and the RLC layer entity from the BS302/network using the “RRCReconfiguration message”. Alternatively, the UE304may receive the configurations of the MAC layer entity, and the RLC layer entity from ‘mac-LogicalChannelConfig’, logicalChannelIdentity ID and servedRadioBearer. The UE304passes the configurations of the MAC layer entity and the RLC entity of the primary stack304ato the secondary stack304bto configure the MAC layer entity and the RLC layer entity on the secondary stack304b.

The UE304may share the configurations of the RLC layer entity (rlc-Config configuration) from the primary stack304ato the secondary stack304b, only if the configurations of the RLC layer entity are required.

The secondary stack304bmay be used for only the RACH procedure. Once the RACH procedure is completed, the secondary stack304bmay be deactivated. Thus, in an embodiment, a lightweight secondary stack has been created, wherein the split may be performed at the RLC layer entity. The secondary stack may have only the MAC layer entity and the physical layer entity. The splitting at the RLC layer entity may also help the UE304to save resources (for example, the memory402, a CPU clock, processing, or the like) used of extra RLC layer entity/protocol.

Once the secondary stack304bis created, the UE304passes the RACH trigger configurations/RACH configurations corresponding to the second RACH procedure from the primary stack304ato the secondary stack304b. The UE304may receive the RACH trigger configurations as a part of the SIB1 or the RRCReconfiguration message based on the trigger reason and network configuration. Depending on the trigger reason, the UE304shares only the corresponding RACH trigger configurations to the secondary stack304bfrom the primary stack304a.

For example, if the second RACH procedure for the on-demand SI is triggered and the primary stack304amay already have an on-demand SI RACH configuration (an example of the RACH trigger configuration) received from the network/BS302. In such a scenario, the on-demand SI RACH configuration may be passed onto the secondary stack304bfrom the primary stack304a, thus saving the secondary stack processing/time in obtaining the RACH trigger configuration from the network/BS302again.

Once the secondary RACH procedure is triggered and completed successfully, the secondary stack304binforms the primary stack304aabout the triggered second RACH procedure. The secondary stack304bmay also share timing advance details to the primary stack304ain case the secondary stack304bis triggered for the UL sync/RLF/BFR scenario. Then, the primary stack304adeactivates the secondary stack304b.

Thus, in embodiments herein, the UE304creates the secondary stack304bonly for the RACH procedure. Once the RACH procedure is completed, the UE304deactivates the secondary stack304bunlike the typical DAPS used in the HO, where the data may continue on a target cell. When the split is at the RLC layer entity, the DRB may be mapped to logical channels on the secondary stack304blike on the primary stack304a. In an example, as shown in theFIG.8A, the split is at the PDCP, providing a typical secondary stack304bused in the dual connection and DAPS scenarios. As shown in theFIG.8B, the split is at the RLC, providing a light weight secondary stack to support only RACH.

FIG.9depicts an example call flow, which may be used on all types of RACH type triggers, according to various embodiments.

As depicted inFIG.9, a RAR window indicates a time period, wherein the UE304is expected to receive a MSG2 from the network/BS302when the RACH procedure is ongoing. A CT window may be a time period, wherein the UE304is expected to receive a MSG4 from the network/BS302. The UE304may receive the RAR window and the CT window from the network/BS302as the part of the RACH configuration.

In an embodiment, the UE304starts RACH #1 on gnB #1 and RACH #2 is triggered and RACH collision is detected. The UE304activates the second stack304band share MAC, RLC, PHY configuration to the second stack304b. If the UE304identifies the second RACH procedure during the RAR window of the first RACH procedure, the UE304creates the secondary stack304busing the DAPS capability. The UE304performs the first RACH procedure and the second RACH procedure on the primary stack304a(a UE stack 1) and the secondary stack304b(a UE stack 2) simultaneously. If the UE304receives the MSG4 from the network/BS302during the CT window of the second RACH procedure, the UE304deactivates/disables the secondary stack304b.

FIG.10depicts an example call flow for handling the multi-RACH trigger for the CFRA procedure during an on-demand SI scenario, according to various embodiments.

As depicted inFIG.10, the UE304identifies the triggering of the second RACH procedure before receiving the MSG4 from the network/BS302when the first RACH procedure is ongoing with the network/BS302. In such a scenario, the UE304activates the secondary stack304b/dual stack using the DAPS capability. The UE304completes the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304bsimultaneously/in parallel. On completing the second RACH procedure, the UE304deactivates the secondary stack304b, thus avoiding the delay in receiving the on-demand services.

FIG.11depicts an example call flow for handling the multi-RACH trigger for the CBRA procedure during the on-demand SI scenario, according to various embodiments.

As depicted inFIG.11, the UE304identifies the triggering of the second RACH procedure before receiving the MSG2 from the network/BS302when the first RACH procedure is ongoing with the network/BS302. In such a scenario, the UE304activates the secondary stack304b/dual stack using the DAPS capability. The UE304completes the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304bsimultaneously/in parallel. On completing the second RACH procedure, the UE304deactivates the secondary stack304b.

FIG.12depicts an example call flow for handling the RACH collisions during the UL CA scenario, according to various embodiments.

As depicted inFIG.12, the UE304may identify the collision of the two RACH procedures, when the second RACH procedure is triggered on the MAC entity on which the first RACH procedure is ongoing. In such a scenario, the UE304activates the secondary stack304b/dual stack using the DAPS capability. The UE304completes the first RACH procedure and the second RACH procedure on the primary stack304aand the secondary stack304bsimultaneously/in parallel. On completing the second RACH procedure, the UE304deactivates the secondary stack304b.

FIG.13is a flowchart depicting an example process/method for handling the multiple RACH triggers, according to various embodiments.

On the second RACH procedure being triggered while the first RACH procedure is ongoing on the primary stack304a(as depicted inFIG.14A), the UE304checks if the UE304is capable of the dual stack/DAPS. If the UE304is not capable of the dual stack, the UE304follows a legacy approach. If the UE304is capable of the DAPS, the UE304shares the configurations of the RLC layer entity, the physical layer (PHY) entity, and the MAC entity from the primary stack304ato the secondary stack304b. The UE304also shares the RACH trigger configurations/RACH configuration corresponding to the second RACH procedure with the secondary stack304b. The UE304initiates the secondary RACH procedure on the secondary stack (as depicted inFIG.14B). On completion of the second RACH procedure, the UE304disables the secondary stack304b(as depicted inFIG.14C). On successful completion of the first RACH procedure, the UE304may choose to disable the secondary stack304band continue the secondary RACH procedure on the first stack304a(if the second stack has not yet been completed).

Consider an example scenario, wherein the UE304receives the request for V2X or D2D or any specific services, which require the on-demand SI request. If the wireless network300is a NR network, then only SIB1 is mandatorily broadcasted by the BS/network302and all the other SIBs may be configured to be acquired by the UE304using an on-demand SI process. As of 38.331 V16.2, there may be 14 SIBs defined, so there is a possibility for the UE304to acquire the SIB2 to SIB 14 via the on-demand-SI request. So, the UE triggers the RACH #1 procedure (the first RACH procedure) on a NR cell #1 (RACH #1, cell #1, Trigger reason on-demand SI). In an example herein, during the RACH #1 procedure, the UE304has some uplink data to send to the BS302and the UE304has to trigger the RACH procedure process for the uplink synchronization. (i.e., RACH #2, cell #1, trigger reason UL_SYNC). In another example herein, during the RACH #1 procedure, the UE304has some uplink data to send to the BS302and there are no grants currently available for the UE304to send the uplink data, which may eventually lead the UE304to trigger the RACH procedure on the cell 1 (i.e., RACH #2, cell #1, Trigger Reason is UL_Grants).

The UE304configured with the UL-CA triggers the RACH #1 on the primary cell #1 for the uplink synchronization (RACH #1, cell #1, Trigger Reason UL_Grants). During the first RACH procedure, there may be a trigger for the second RACH on the secondary cell for the uplink synchronization (RACH #2, cell #2, Trigger reason UL_SYNC). In the UL-CA, all the multiple cells may have the single MAC entity). As per the 3GPP specification 38.331-5.1.1, since there is no possibility of having 2 RACH at same time by UE304on the single MAC entity, there may be a delay on the RACH #2, as the second RACH procedure may be started only upon completion of the first RACH.

In contrast, various embodiments disclosed herein enable the UE to overcome the restriction of single RACH procedure in the RAT at an instance using DAPS possibility effectively. In NR, there may a possibility of multiple RACH triggers when a RACH procedure is currently ongoing. In such scenarios, the UE304may trigger the second RACH procedure on the secondary stack304bwhile the first RACH procedure is ongoing. Thus, reducing the delay of having to wait for the completion of the first RACH.

Various embodiments disclosed herein initiate the secondary stack304bwhen the RACH collision is detected to perform the two RACH procedures simultaneously and avoid the delay for the second RACH services, which may be completely initiated and controlled by the UE itself. In an embodiment:1. The DAPS may be released by the UE304upon completion of the RACH procedure;2. Both the primary stack and the secondary stack may be latched to the same cell/BS302;3. the RACH configurations may be shared to the secondary stack by the primary stack itself;4. the two RACH may be performed simultaneously using the primary cell RACH configuration on the same cell/BS302; and5. the secondary stack may be initiated using the same configuration of the primary cell.

FIG.15is a diagram depicting example handling of the RACH procedure in the multiple/multi beam scenarios, according to various embodiments.

The UE304may handle the RACH procedure in the following scenarios:

Single Cell/BS302with Multiple Beams:

1. Beam Failure Recovery (BFR): During the BFR, the UE304has to perform the two same RACH procedures simultaneously on the two candidate beams. The RACH resources and the candidate beam to use during a recovery from the beam failure may be known to the UE304in advance, which may be an ideal scenario for the UE304to initiate the dual stack/DAPS itself without network intervention for performing the two RACH procedures simultaneously. Performing the two same RACH procedures simultaneously may help the UE304to recover from the beam failure and resume the data activity with the cell/BS302with less interruption to the user. Even when the RACH procedure on one of the beams fails, the other RACH procedure may be success and allow the UE304to resume the data services quickly.2. Initial access, RLF, UL grants, UL sync, or the like: For UE's operating in greater than 6 Giga Hertz (6 GHz) frequency range, there may be possibility of up to 64 beams. Thus, there may be a temporary network, and environmental issues such as, but not limited to, vehicle blockage, or the like. Such issues may block the beam temporarily and may delay the RACH procedure on the respective beam. Thus, in such scenarios, the UE304may use the DAPS capability to active the dual stack (i.e., the primary stack304aand the secondary stack304b) by itself without network intervention and to trigger the two same RACH procedures on the two different beams, thereby helping the UE to overcome from the temporary issues on some of the beams, which further enables the UE to complete the RACH procedure at a faster rate.
Multi-Cell Scenario:1. 2 different cells during an initial access: when the UE304has a valid RACH configuration of two different cells/BSs302, the UE304may exploit the multiple stacks to trigger the RACH on the multiple cells/BSs302. Thus, during the initial access, the UE304may access the cell302on which the RACH may be successfully completed first. Further, at a cell edge, where the UE304have poor signal coverage/unlicensed spectrum on multiple cells may be very beneficial.

Thus, in general, various embodiments disclosed herein may be used any time when the RACH procedure is predicted to be triggered in the UE304. Also, handling the multiple RACH procedure may be useful in an unlicensed spectrum also, where the UE304has to do “listen before talk” for every uplink transmission. In such a spectrum, there may be a possibility that one beam may be more congested than other, thus delaying the RACH procedure.

In an embodiment, when the UE304has to trigger the RACH procedure in the multi-beam environment on encountering the beam failure/RLF/UL sync/UL grants or on performing the initial access, the UE304activates the secondary stack304bwith the same configurations of the physical layer entity, the MAC layer entity, and the RLC layer entity of the primary stack304a. The UE304shares the RACH configuration corresponding to the RACH procedure and the beam ID to the secondary stack.

If the RACH procedure is the CFRA procedure, the UE304shares the beam ID (to check the possibility of other best beams) of the primary stack304ato the secondary stack304band initiates the RACH procedure on the secondary stack304b, if the MSG2 is not received/failed at least once or Reference Signal Received Power (RSRP) is very poor. Since the CFRA procedure is only 2 step procedure with the dedicated preamble, there may be high chance of successful RACH. Thus, if the RACH procedure is the CFRA procedure, the UE304chooses the beam on the secondary stack and performs the RACH on the chosen beam simultaneously along with the RACH on the primary stack304aon the first chosen beam.

In case of the CBRA procedure, since the same RACH trigger may be used in both stacks, there may be a possibility of choosing the same RACH preamble in both stacks, which may result in a contention failure. To avoid the contention failure, the UE304shares the preamble information with the primary stack304aand the secondary stack304b. In case of CBRA procedure, if the MSG2 is passed, then the RACH procedure on the other stack may be aborted by the UE304optionally assuming most RACH failure may occur at the MSG1. The aborted RACH may be re-started again, if there is the RACH failure at the MASG3 on the other stack. If the RACH procedure is successfully completed on the primary stack304afirst, the UE304aborts the RACH procedure on the secondary stack304b. If the RACH procedure is successfully completed on the secondary stack first, the UE304aborts the RACH procedure on the primary stack304aand informs the primary stack304aabout the successful completion of the RACH procedure. The UE304then deactivates the secondary stack304b.

Consider an example scenario, as depicted inFIG.15, wherein the UE304identifies the triggering of the RACH procedure. In an example, the RACH procedure may be triggered due to the BFR, the UL grants, the UL sync, or the like. In another example, the RACH procedure may be triggered due to the temporary RACH issues such as, but not limited to, the MSG1 not reaching network, a RAPID mismatch, a MSG2 decoding failure, the contention failure, vehicular/environmental issues, and so on. In such a scenario, the UE304activates the secondary stack304busing the DAPS capability. The UE304performs the same RACH procedure on a beam 1 and a beam 2 using the primary stack304aand the secondary stack304bsimultaneously. Thus, the UE304may connect to at least one of the beam 1 or the beam 2, even if the RACH procedure is failed on one of the beam 2 or the beam 1, respectively. In an example, as depicted inFIG.15, the RACH procedure performed on the beam 1 using the primary stack304amay fail, and the RACH procedure performed on the beam 2 using the secondary stack304bmay be successful. Thus, the UE304may connect to the beam 2 for accessing the critical services without any delay, which enhances the user experience.

FIG.16AandFIG.16Bare example diagrams depicting configuring the secondary stack304bfor performing the RACH procedure in the multi-beam scenarios, according to various embodiments.

When the event occurs to trigger the RACH procedure to resume/connect the service on the cell/BS302consisting of the multiple beams (for example, FR2 frequency cells), or an event occurs to select the cell302among the two different cells302when the UE304has the valid RACH configuration of both the cells, the UE304activates the secondary stack304b. In an example, the event occurring to trigger the RACH procedure to resume/connect the service may include at least one of the BFR, the initial access, the RLF, the UL sync, the UL grants, or the like. In an example, the event occurring to select the cell among the two different cells may include the initial access.

The UE304activates the secondary stack304busing the DAPS without network intervention. The UE304performs the second RACH procedure (with the same trigger reason) on the secondary stack304bsimultaneously with the first RACH procedure on the primary stack304a.

The activated secondary stack304bmay include the physical layer entity, the MAC layer entity, and the RLC layer entity (an optional layer). The configurations of the physical layer entity of the secondary stack304bmay be same as the primary stack304a. The UE304may receive the configurations of the physical layer entity as a part of ‘ServingCellConfigCommonSIB’ IE present in the ‘SIB1’ received from the cell/BS302on the primary stack304a. The UE304shares the configurations of the physical layer entity to the secondary stack304bfrom the primary stack304ato configure the physical layer entity at the secondary stack304b. Similarly, the configurations of the MAC layer entity and the RLC layer entity may be the same as the physical layer entity. The UE304may receive the configurations of the RLC layer entity and the MAC layer entity from the cell/BS302in the primary stack304ain the “RRCReconfguration message”. The UE304may also receive the configurations of the MAC layer entity and the RLC layer entity in ‘MAC-LogicalChannelConfig’, logicalChannelIdentity ID and servedRadioBearer. The UE304may share the configurations of the MAC layer entity and the RLC layer entity to the secondary stack304bfor configuring the MAC layer entity and the RLC layer entity at the secondary stack304b. The UE304may share the configurations of the RLC layer entity to the secondary stack304b, if the configurations of the RLC layer entity are required for handling the RACH procedure.

The UE304may deactivate/disable the secondary stack304bonce one of the RACH procedures is completed, since the secondary stack304is used only for the RACH procedure. Thus, the lightweight secondary stack304bmay be provided (FIG.16B), wherein the split may happen at the RLC layer entity. Thus, the secondary stack304bmay include only the physical layer entity and the RLC layer entity. Splitting at the RLC layer entity may help the UE304to save the resources used of the extra RLC protocol.

Once the secondary stack304bis created, the UE304also passes the corresponding RACH trigger configuration/RACH configuration to the secondary stack304b, which may be the trigger reason for the second RACH procedure. The trigger reason may include at least one of the RLF, the UL sync, the UL data, the BFR, or so on. The UE304may receive the RACH configuration as the part of the SIB1 or the “RRCReconfiguration message” based on the trigger reason and the network configuration. Depending on the trigger reason, the UE304may pass only the corresponding RACH configuration to the secondary stack304b.

The UE304also shares the preamble information between the primary stack304aand the secondary stack304b. For handling the same RACH procedure on both stacks, the RACH resources have to be chosen from the same set of contention-based preambles. The UE304ensures that both stacks304a,304bmay not choose the same preamble.

FIGS.17A,17B,17C, and17Dare diagrams depicting example sharing of the preamble information between the primary stack304aand the secondary stack304b, according to various embodiments.

When the same RACH configuration is used in both the primary stack304aand the secondary stack304b, there may be a possibility of a same preamble used on both the primary stack304aand the secondary stack304b. Also, there may be a possibility that the beams change dynamically during the RACH procedure. Thus, in order to avoid the same preamble on both the primary stack304aand the secondary stack304b, the UE304may divide the preamble information among both the primary stack304aand the secondary stack304b, while the RACH configuration is shared from the primary stack304ato the secondary stack304b.

In various embodiments, the UE304may share the preamble information between the primary stack304aand the secondary stack304busing three methods.

In a first method/method #1, as depicted inFIG.17A, the UE304divides the preamble information/content-based preambles into the two sets, the first set and the second set. The UE304assigns the first set to the primary stack304aand the second set to the secondary stack304b. In an example, consider that there may be maximum up to 64 (e.g., x=8) preambles allocated for the beam. In such a scenario, the UE304divides the preambles into two halves so that the primary stack304amay choose from the first 32 (x/2) (e.g., the first 4 inFIG.17A) set of preambles and the secondary stack304bmay choose from the second32(x/20) (e.g., the second 4 inFIG.17A) set of preambles. When the UE304uses the first method to share the preamble information between the primary stack304aand the secondary stack304b, the preamble sharing may not happen frequently. However, if the number of preambles allocated (the value of x) is less than the both the primary stack304aand the secondary stack304b, the UE304has to choose from further less number of preambles using a third method/method #3.

In the second method depicted inFIG.17B, the UE304divides the preambles such that an even set of preambles may be used by the primary stack304aand an odd set of preambles may be used by the secondary stack304b. In an example, consider that a maximum of 64 preambles may be allocated for the contention. In such a scenario, the primary stack304aindicates the secondary stack304bto choose only from the odd preambles. Thus, the primary stack304achooses from the even preambles. When the UE304uses the second method to share the preamble information between the primary stack304aand the secondary stack304b, the preamble sharing may not happen frequently. However, if the number of preambles allocated (the value of x) is less than the both the primary stack304aand the secondary stack304b, the UE304has to choose from further less number of preambles using the third method/method #3.

In the third method depicted inFIG.17C, the UE304shares the currently used preamble ID and the beam ID to the secondary stack304bfrom the primary stack304a, so that the secondary stack304bmay not use the particular preamble till the subsequent notification. The third method of sharing the preamble information between the primary stack304aand the secondary stack304bmay be a dynamic approach of sharing the preambles whenever the stack sends the preamble, the stack sends the corresponding preamble ID and the beam ID to the other stack. The other stack may consider the received preamble ID and the beam ID as valid only till the RAR window is expired. The third method of sharing the preamble information between the primary stack304aand the secondary stack304bmay be advantageous when the number of preambles allocated is small, as the UE304may have almost all preambles to choose from. Since at any point of time only one preamble is not valid for other stack, but there may be more communication between the stacks (i.e., whenever the preamble is sent to the network/BS302).

An example method of configuring the preambles and sharing of the preambles among the SSB's depending on the RACH configuration is depicted inFIG.17D.

FIG.18depicts an example call flow for handling the multiple same RACH procedures in the multi-beam scenario, wherein the RACH procedure is the CFRA procedure, according to various embodiments.

Consider an example scenario, wherein the UE304initiates the RACH procedure on the beam 1 using the primary stack304adue to the BFR. When the UE304does not receive the MSG2 during the RAR window, the UE304activates the secondary stack304busing the DAPS. The UE304initiates the RACH procedure on the beam 2 using the secondary stack304b. When the RACH procedure performed on the primary stack304aor the secondary stack304bis successful, the UE304aborts the ongoing RACH procedure and deactivates the secondary stack304b. Thus, the BFR may be recovered with more probability of success, as recovery is tried on 2 beams in parallel. When the BFR recovery is performed on the 2 beams simultaneously, the UE304may have more probability to pass the BFR quickly on one of the beams, even if there is some temporary issue on the other beam.

FIGS.19A and19Bdepict example call flows for handling the multiple same RACH procedures in the multi-beam scenario, wherein the RACH procedure is the CBRA procedure, according to various embodiments.

The UE304activates the secondary stack304busing the DAPS capability to handle the RACH procedure on the multiple beams. The UE304activates the secondary stack304bby sharing the configurations of the physical layer entity, the MAC layer entity, and the RLC layer entity, the RACH trigger configuration, and the preamble information. In an example herein, the preamble information may be shared between the primary stack304aand the secondary stack304busing the method2. The primary stack304amay use the even set of preambles and the secondary stack304buses the odd set of preambles.

On activating the secondary stack304b, the UE304initiates the RACH procedure on the beam 1 and the beam 2 due to the BFR using the primary stack304aand the secondary stack304bsimultaneously. In an example herein, as depicted inFIG.19A, consider that the RACH procedure on the beam 2 using the secondary stack304bis successfully completed before the RACH procedure on the beam 1. In such a scenario, the UE304aborts the ongoing RACH procedure on the beam 1 using the primary stack304aand deactivates the secondary stack304b.

In another example herein, as depicted inFIG.19B, consider that the RACH procedure on the beam 1 using the primary stack304ais successfully completed before the RACH procedure on the beam 2. In such a scenario, the UE304aborts the ongoing RACH procedure on the beam 2 using the secondary stack304band deactivates the secondary stack304b.

FIG.20is a sequence diagram depicting example performing of the RACH procedure on the different cells/BSs302, according to various embodiments.

When the UE304with the valid RACH configuration wants to perform an initial access/RACH procedure on the two different cells/BSs302(a gNB1, and a gNB2), the UE304activates the secondary stack304busing the DAPS capability. The UE304starts the RACH procedure for the initial access on the primary cell/gNB1 using the primary cell RACH configuration and the secondary cell/gNB 2 using the secondary cell RACH configuration simultaneously.

In case of the contention-based RACH, if the MSG2 is passed then the RACH on the other stack may be aborted optionally assuming the most RACH failure happen at the MSG1. In an example, consider that the initial access is successfully completed on the primary stack first. In such a scenario, the UE304aborts the RACH procedure on the secondary stack304band continues the services from the cell/gNB 1 selected on the primary stack304a. The UE304then deactivates the secondary stack304b.

In another example, consider that the initial access is successfully completed on the secondary stack first. In such a scenario, the UE304aborts the RACH procedure on the primary stack304aand informs the primary stack304aabout the successful completion of the RACH procedure. The UE304continues the services from the cell/gNB 2 selected on the secondary stack304b. The UE304then deactivates the secondary stack304b.

FIG.21is a flow chart depicting an example method for handling the RACH procedure in the multi-beam scenario, according to various embodiments.

At step1, the UE304detects the event (for example, the beam failure, the RLF, the initial access, or the like) occurring to trigger the RACH procedure. At step2, the UE304checks if the UE304is capable of supporting the dual stack/DAPS. If the UE304does not support the dual stack/DAPS, at step3, the UE304follows the legacy approach to perform the RACH procedure.

If the UE304supports the dual stack/DAPS, at step4, the UE304starts the RACH procedure on the beam 1/cell 1 using the primary stack304a. At step5a, the UE304checks if the RACH procedure passed on the primary stack304a. If the RACH procedure is passed on the primary stack304a, at step5b, the UE304aborts the secondary stack304b. If the RACH procedure is not passed on the primary stack304a, the UE304repeats the step4to continue with the step6.

At step6, the UE304activates the secondary stack304bby sharing the configurations of the physical layer entity, the MAC layer entity, and the RLC layer entity to the secondary stack304bfrom the primary stack304a. At step7, the UE304checks if the triggered RACH procedure is the CFRA procedure. If the RACH procedure triggered is not the CFRA procedure, at step8, the UE304shares the RACH configuration and the preamble sharing information to the secondary stack304b. At step9, the UE304starts the RACH procedure on the secondary stack304bin parallel with the RACH procedure ongoing on the primary stack304a. At step10, the UE304checks if the RACH procedure is passed on the secondary stack304b. If the RACH procedure is passed on the secondary stack304b, at step11, the UE304indicates the primary stack304aabout the successful RACH procedure on the secondary stack304b.

If the triggered RACH procedure is the CFRA, at step12, the UE304checks if the RSRP is poor (for example, if the RSRP is less than −100 dbm) and if the MSG2 is failed on the primary stack. If the RSRP is not poor and the MSG2 is not failed, at step13, the UE304continues the RACH procedure on the primary stack304a. If the RSRP is poor and the MSG2 is failed, at step14, the UE304shares the beam ID and the RACH configuration to the secondary stack304band initiates the RACH procedure on the secondary stack304b. On performing step14, the UE304continues with step9. The various actions listed inFIG.21may be performed in the order presented, in a different order or simultaneously. Further, in various embodiments, some actions listed inFIG.21may be omitted.

FIG.22is a diagram depicting example distinguishing between the two same RACH procedures at the cell/BS/network302, according to various embodiments.

Each preamble shared between the primary stack304aand the secondary stack304bmay have an own set of time, frequency resources, or the like. Also, each RACH procedure may have its own preamble to choose from. Thus, the combination of the preamble and its RACH resources (time and frequency) may be used to distinguish the RACH procedures at the network302.

Unlike the UE304, a MAC entity of the network302may serve all the UEs304that are camped on the particular cell using its single MAC entity. Thus, network302may differentiate between the RACH procedures of the UE304based on the resources selected by the UE304.

Embodiments herein enable the UE304to perform the RACH procedures with the following advantages:1. for latency critical applications, performing the RACH procedures on the two different beams may help to recover from the beam failure with reduced latency and resume the services as soon as possible;2. there may be some temporary issues on one beam (especially due to vehicular blockage or environment issues) which may take more time for the RACH procedure to complete. Hence performing the RACH procedure on the two beams may benefit the UE304to complete the RACH procedure earlier on one of the beams;3. also accessing the two different cells at same time is made possible, even if the RACH procedure is failing on one cell or extra delay on one of the cells, then UE304may (re) gain the services if the RACH procedure is successful on one cell;4. performing the RACH procedure on the 2 different beams using the two stacks in parallel may be helpful if the best beam is highly congested during the CBRA procedure, since there may be a high chance of the RACH procedure being successful earlier in one of the beams; and5. performing the RACH procedure on the 2 different beams using the two stacks in parallel may be helpful in the un-licensed spectrum as there may be a LBT (listen before talk) failure on the one beam but on the other beam the RACH procedure may be successful due to the nature of devices working on the un-licensed spectrum.

The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the elements. The elements shown inFIGS.3A,3B,3C, and4can be at least one of a hardware device, or a combination of hardware device and software module.

FIG.23illustrates an example electronic device according to various embodiments.

Referring to theFIG.23, the electronic device2300may include a processor (or a controller)2310, a transceiver2320and a memory2330. However, all of the illustrated components are not essential. The electronic device2300may be implemented by more or fewer components than those illustrated inFIG.23. In addition, the processor2310and the transceiver2320and the memory2330may be implemented as a single chip according to various embodiments.

The electronic device2300may correspond to the electronic device described above. For example, the electronic device2300may correspond to the terminal or the UE304illustrated inFIGS.3A,3B,3C and4.

The aforementioned components will now be described in detail.

The processor2310(e.g., including processing circuitry) may include one or more processors or other processing devices that control the proposed function, process, and/or method. Operation of the electronic device2300may be implemented by the processor2310.

The transceiver2320may include an RF transmitter for up-converting and amplifying a transmitted signal, and an RF receiver for down-converting a frequency of a received signal. However, according to various embodiments, the transceiver2320may be implemented by more or fewer components.

The transceiver2320may be connected to the processor2310and transmit and/or receive a signal. The signal may include control information and data. In addition, the transceiver2320may receive the signal through a wireless channel and output the signal to the processor2310. The transceiver2320may transmit a signal output from the processor2310through the wireless channel.

The memory2330may store the control information or the data included in a signal obtained by the electronic device2300. The memory2330may be connected to the processor2310and store at least one instruction or a protocol or a parameter for the proposed function, process, and/or method. The memory2330may include read-only memory (ROM) and/or random access memory (RAM) and/or hard disk and/or CD-ROM and/or DVD and/or other storage devices.

FIG.24illustrates an example base station according to various embodiments.

Referring to theFIG.24, the base station2400may include a processor (or a controller)2410, a transceiver2420and a memory2430. However, all of the illustrated components are not essential. The base station2400may be implemented by more or fewer components than those illustrated inFIG.24. In addition, the processor2410and the transceiver2420and the memory2430may be implemented as a single chip according to another embodiment.

The base station2400may correspond to the gNB described above. For example, the base station2400may correspond to the gNB302illustrated inFIGS.3B and3C.

The aforementioned components will now be described in detail.

The processor2410(e.g., including processing circuitry) may include one or more processors or other processing devices that control the proposed function, process, and/or method. Operation of the base station2400may be implemented by the processor2410.

The transceiver2420may include an RF transmitter for up-converting and amplifying a transmitted signal, and an RF receiver for down-converting a frequency of a received signal. However, according to various embodiments, the transceiver2420may be implemented by more or fewer components.

The transceiver2420may be connected to the processor2410and transmit and/or receive a signal. The signal may include control information and data. In addition, the transceiver2420may receive the signal through a wireless channel and output the signal to the processor2410. The transceiver2420may transmit a signal output from the processor2410through the wireless channel.

The memory2430may store the control information or the data included in a signal obtained by the base station2400. The memory2430may be connected to the processor2410and store at least one instruction or a protocol or a parameter for the proposed function, process, and/or method. The memory2430may include read-only memory (ROM) and/or random access memory (RAM) and/or hard disk and/or CD-ROM and/or DVD and/or other storage devices.

Although this disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that this disclosure encompass such changes and modifications as fall within the scope of the appended claims.

Embodiments disclosed herein describe methods and systems for handling multiple Random Access Channel (RACH) procedures. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable medium having at least one instruction therein, such computer readable storage medium containing program code for implementation of one or more operations of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in embodiments through or together with a software program written in e.g., Very high speed integrated circuit Hardware Description Language (VHDL), another programming language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device may be any kind of portable device that may be programmed. The device may also include means which could be e.g., hardware such as e.g., an ASIC, or a combination of hardware and software, e.g., an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. Embodiments described herein could be implemented partly in hardware and partly in software. The concepts may be implemented on different hardware devices, e.g., using a plurality of CPUs.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.