CN111466149A - Random Access Technology in Wireless Network - Google Patents

Abstract

A wireless communication method implemented in a user equipment allows for starting a timer and initiating a random access procedure. The random access procedure is triggered in response to a random access trigger event. Furthermore, the timing instance associated with the start of the timer depends on the random access trigger event. In some embodiments, the random access procedure can be performed by detecting at least one random signal (RS) while the timer is running.

Description

Random Access Technology in Wireless Network

technical field

The present disclosure generally relates to digital wireless communications.

Background technique

Mobile telecommunications technology is propelling the world into an increasingly interconnected and networked society. Compared to existing wireless networks, next-generation systems and wireless communication technologies will need to support a wider range of use-case characteristics and provide more sophisticated and sophisticated access requirements and flexibility.

Long Term Evolution (LTE) is a wireless communication standard developed by the 3rd Generation Partnership Project (3GPP) for mobile devices and data terminals. LTE-Advanced (LTE-A) is a wireless communication standard that enhances the LTE standard. The fifth generation of wireless systems, known as 5G, further advances the LTE and LTE-A wireless standards and is committed to supporting higher data rates, massive connections, ultra-low latency, high reliability and other emerging business needs.

SUMMARY OF THE INVENTION

Exemplary embodiments disclose a wireless communication method. The exemplary method includes starting a timer and initiating, by the user equipment, a random access procedure in response to a random access trigger event, wherein the time instance associated with the starting of the timer depends on the random access trigger event; and The random access procedure is performed by detecting at least one reference signal (RS) while the timer is running.

In some embodiments, performing the random access procedure further includes, in response to determining that a reference signal (RS) is not present: applying a back-off time, and after applying the back-off time, detecting at least one reference signal (RS) while the timer is running.

In an exemplary embodiment, the reference signal (RS) is a qualified reference signal (RS). In some embodiments, the qualified reference signal (RS) is a synchronization signal (SS) resource or a channel state information reference signal (CSI-RS) resource. In some embodiments, the qualified reference signal (RS) includes resources that meet a predetermined threshold, or resources that allow the user equipment to meet the target received power of the random access channel (RACH) preamble with the maximum transmit power of the user equipment.

In some embodiments, the random access triggering event includes sending a scheduling request (SR), requesting system information (SI), performing initial access from RRC_IDLE to RRC_CONNECTED, performing RRC connection re-establishment, performing handover, performing RRC connection recovery, or Recover from beam failure.

In an exemplary embodiment, the wireless communication method further comprises: determining the expiration of the timer; in response to the random access triggering event being the sending of a scheduling request (SR), sending a media access control (MAC) entity to the MAC entity The first layer above indicates a random access problem; and a failed SI request is indicated in response to the random access triggering event being a request for system information (SI). In some embodiments, the first layer is a radio resource control (RRC) layer. In some embodiments, the second layer is a non-access stratum (NAS) layer or an application layer.

In some embodiments, in response to the random access triggering event being a request for system information (SI): a connection re-establishment procedure is initiated. In some embodiments, in response to the random access triggering event being a request for system information (SI): in response to a request for system information (SI) triggered by the second layer, to a radio resource control (RRC) layer above Layer 2 notifies failed SI requests.

In an exemplary embodiment, the instance of time when the timer is started is before or at the same time as the random access procedure is initiated by the random access trigger event. In some embodiments, the wireless communication method further includes stopping the timer in response to determining a successful random access procedure.

In another exemplary embodiment, a wireless communication method includes: initiating, by a user equipment, a random access resource selection procedure; starting a timer in response to initiation of the random access resource selection procedure during the random access procedure; and in response to detecting The timer is stopped when the reference signal (RS) is reached.

In some embodiments, the time instance associated with the initiation of the timer is prior to or concurrent with initiation of the random access resource selection procedure.

In an exemplary embodiment, the wireless communication method further includes determining expiration of a timer and indicating, by a medium access control (MAC) entity, a random access problem to a layer above the MAC entity.

In another exemplary embodiment, the wireless communication method further includes, determining expiration of a timer; after determining that the timer expires, increasing the number of random access resource selection procedures by a predetermined value; after determining that the timer expires Thereafter, in response to determining that the number of random access resource selection procedures is less than the maximum number of random access resource selection procedures, re-initiating the random access resource selection procedure; and after determining that the timer expires, in response to determining that the random access resource selection procedure The number of procedures is equal to the maximum number of random access resource selection procedures, and the random access problem is indicated by the medium access control (MAC) entity to the layers above the MAC entity.

In some embodiments, the random access resource selection procedure is re-initiated after the back-off time is applied.

In yet another exemplary embodiment, the wireless communication method further includes, determining expiration of a timer; indicating a random access resource selection failure to a layer above the MAC entity; and after determining that the timer expires, re-initiating random access Access resource selection process.

In some embodiments, the wireless communication method further comprises, in response to receiving the maximum number of random access resource selection failures, declaring, by a layer above the MAC layer, a radio link failure.

In yet another exemplary aspect, the above-described method is embodied in processor-executable code and stored on a computer-readable program medium.

In yet another exemplary embodiment, an apparatus configured or operable to perform the above-described method is disclosed.

The above and other aspects and embodiments thereof are described in greater detail in the drawings, specification and claims.

Description of drawings

Figure 1 shows several user equipments and base stations operating within a cell area of a wireless system.

Figure 2 shows an exemplary random access procedure.

3 illustrates an example reference signal resource selection process.

4 illustrates an example contention-based random access resource selection procedure using certain example timer features.

5 illustrates another exemplary contention-free random access resource selection process using certain exemplary timer features.

6 shows a block diagram of an example user equipment for implementing random access and timer features.

Detailed ways

In order to meet the increasing demands for bandwidth, the next generation of wireless systems will adopt high operating frequencies such as up to 100 GHz. Propagation losses can be high when using such high operating frequencies. To solve this problem, next-generation wireless communication devices may employ antenna arrays and beamforming (BF) techniques using multiple-input multiple-output (MIMO) technology. As an example, 1024 antenna elements may be employed for one node to achieve beam alignment and obtain sufficiently high antenna gain.

Typically, user equipments (UEs) may use random access procedures to access networks in wireless systems, such as Universal Terrestrial Radio Access Network (UTRAN), E-UTRAN or 5G New Radio (NR). The random access procedure can be triggered by a number of events, such as:

· Initial access from RRC_IDLE;

Radio Resource Control (RRC) connection re-establishment procedure;

switch;

Downlink (DL) or uplink (UL) data arrival during RRC_CONNECTED when the UL synchronization state is "Asynchronous";

· Transition from RRC_INACTIVE

a request for additional system information (SI); or

· Recover from beam failure.

Traditional random access procedures are designed for wireless systems and do not employ BF techniques such as UTRAN or E-UTRAN. With the introduction of BF technology in 5G NR, traditional random access procedures can be enhanced or redesigned to incorporate BF properties. A random access channel (RACH) configuration associated with reference signal (RS) resources (eg, beams) enables UEs to access the network. RS resources can include, for example, synchronization signal (SS) blocks or channel state information reference signal (CSI-RS) resources.

When implemented in 5G NR wireless systems, traditional random access procedures may have certain disadvantages. For example, taking the RACH configuration associated with the SS block provided from the network as an example, when the random access procedure is initiated, the UE selects one or more SS blocks and a Corresponding one or more PRACH resources for path loss estimation and (re)transmission. If no SS block is detected that meets the given threshold, the UE has the flexibility to select any SS block that allows the UE to meet the target received power of the RACH preamble with its maximum transmit power. However, wireless systems operating in the high frequency range (eg, above 6 GHz) are sensitive to changes in the wireless propagation environment. When the UE is selecting qualified RS resources, it may suffer from blocking. Eligible resources may be resources such as, for example, SS blocks that satisfy a threshold given from the network, or SS blocks that allow the UE to satisfy the target received power of the RACH preamble with the UE's maximum transmit power. In such a case, no eligible RS resources may be successfully detected. Or there may be situations where no eligible RS resources may be detected due to movement or rotational rotation of the UE during the RS selection process. Among other things, the random access techniques described in this document may be used by embodiments to address these situations.

Figure 1 shows several user equipments and base stations operating within a cell area of a wireless system. Base station BS1 (120a) Can communicate with user equipment UE1 (110a), UE2 (110b), UE3 (110c), or UE4 (110d) located in the cell area 130 line communication. One or more UEs are capable of implementing the exemplary random access techniques described in this patent document.

I. To control the timer of the random access procedure

Figure 2 shows an exemplary random access procedure. At start and initiate operation 202, the user equipment may start a timer when the random access procedure is triggered by a random access trigger event. The time instance associated with the activation of the timer depends on the random access triggering event. For example, the time instance when the timer is started may precede or coincide with the initiation of the random access procedure by the random access trigger event. In some embodiments, the time instance when the timer is started may be t1, and the time when the random access triggering event initiates the random access procedure may be t2, where t1<t2. In some other embodiments, the time instance when the timer is started and the time when the random access triggering event initiates the random access procedure may be the same time t1 (t1=t2). The timer may be configured by the network and sent to the UE using eg system information or RRC signaling.

At performing operation 204, while the timer is running, a random access procedure may be performed by detecting at least one eligible RS resource. While the timer is running, the UE may keep performing detection of eligible RS resources until at least one eligible RS resource is detected. In some embodiments, the UE may perform eligible RS resource selection each time the random access resource selection procedure is initiated during the random access procedure.

In some embodiments, the UE may also determine that no eligible RS resources are detected. For example, when the random access resource selection procedure is initiated, the UE may check the number of each RS resource available in the UE. If no qualified RS resource is available, the UE determines that no qualified RS resource is detected. If the UE detects that there are no eligible RS resources, and if the UE determines that a timer such as sr-RandomAccessTimer is still running, the UE may continue to perform eligible RS resource detection after the backoff time. Both the application of the back-off time and the continuation of the eligible RS resource detection process after the back-off time may be repeated until at least one eligible RS resource is detected or the sr-RandomAccessTimer timer expires.

The random access procedure can be triggered by various events. The random access triggering event may be a random access triggered by sending a scheduling request (SR), or a random access triggered by a request for other system information (SI). Details associated with random access triggered by SR or SI are further described in Sections I.(a) and I.(b) below. Additionally, as explained further below, the random access triggering event may also include performing initial access from RRC_IDLE to RRC_CONNECTED, performing RRC connection re-establishment, performing handover, performing RRC connection recovery, or recovering from beam failure.

In some embodiments, if random access is triggered by the transmission of an SR in the MAC entity, and if the UE determines that the timer has expired, the MAC entity may indicate random access problems to upper layers such as the RRC layer. In some embodiments, if random access is triggered by a request from another SI, and if the UE determines that the timer has expired, the SI request is considered to have failed, and the UE may perform at least one of the following: (a) A connection re-establishment procedure is initiated, or (b) if the SI request is triggered by an upper layer, the corresponding upper layer that triggered the SI request is notified of the SI acquisition failure. In this embodiment, the upper layer includes a layer such as a non-access stratum (NAS) layer or an application layer above the RRC layer.

For the case of initial access triggered by initial access from RRC_IDLE, the establish_timer (eg T300 timer) may be started when an RRCConnectionRequest message requesting connection establishment is initiated for transmission. As an example, an RRCConnectionRequest message may be issued from the RRC layer to the MAC entity for transmission. For the case of random access triggered by a transition from RRC_INACTIVE to RRC_CONNECTED, the resume_timer may be started when an RRCConnectionRequest message requesting connection recovery is initiated for transmission. For example, an RRCConnectionRequest message may be issued from the RRC layer to the MAC entity for transmission. In some embodiments, resume_timer can reuse the T300 timer or use a new timer. For the case of random access triggered by the RRC connection re-establishment procedure, the reestablish_timer may be started when the RRCConnectionReestablishmentRequest message requesting the re-establishment of the connection is initiated for transmission. As an example, an RRCConnectionReestablishmentRequest message may be issued from the RRC layer to the MAC entity for transmission. In some embodiments, reestablish_timer may use a timer such as T301, or it may reuse T300.

For the case of random access triggered by handover, the handover_timer may be started when a message for mobility such as a handover command is received. In some embodiments, the handover_timer may use, for example, T304 for the primary cell (PCell) or T307 for the primary and secondary cell (PSCell). For the case of random access triggered by the detection of a beam failure, the beamFailureRecoveryTimer may be started when a beam failure occurs.

For the above five situations, the corresponding establish_timer, resume_timer, reestablish_timer, handover_timer or beamFailureRecoveryTimer can be used to control the random access process. For example, the UE may perform eligible RS resource selection each time a random access resource selection procedure is initiated during random access triggered by one of the above five triggering events. While the timer is running, the UE may keep performing detection of eligible RS resources until at least one eligible RS resource is detected. If the UE detects that an eligible RS resource does not exist, and if the UE determines that a timer such as sr-RandomAccessTimer is still running, the UE may continue to perform eligible RS resource detection after the backoff time. Both the application of the back-off time and the continuation of the qualified RS resource detection process after the back-off time may be repeated until at least one qualified RS resource is detected or the sr-RandomAccessTimer timer expires.

When the random access is considered to be successfully completed, the user equipment may stop the timer.

In the following sections, the random access procedure control is described as a random access procedure, which may be triggered by the transmission of an SR or by the request of other SIs. Exemplary headings in the various sections below are used to facilitate an understanding of the disclosed subject matter and do not limit the scope of the claimed subject matter in any way. Accordingly, one or more features of one example section can be combined with one or more features of another example section.

I.(a). Control of random access triggered by transmission of SR

The SR may be triggered for the purpose of requesting uplink scheduling. For example, when (i) the MAC entity has new UL data available for logical channels belonging to a logical channel group (LCG), and when either (ii.a) the new UL data belongs to a logical channel with A Buffer Status Report (BSR) will be triggered when any logical channel belonging to any LCG's available UL data has a higher priority, or (ii.b) any logical channel belonging to the LCG does not contain any available UL data , to indicate new uplink (UL) data available to the network. However, since there are neither Uplink Shared Channel (UL-SCH) resources available for the new immediate transmission nor a configured UL grant at this time, an SR will be triggered to request UL scheduling.

SR can be transmitted on PUCCH resources configured for SR transmission. The configuration of dedicated PUCCH resources for SR transmission is determined by the network. Therefore, there are certain situations where there are no valid PUCCH resources configured for the transmission of the SR when the SR is triggered. In this case, the random access procedure is triggered. However, even if valid PUCCH resources for SR are configured, when the number of transmissions for this SR has reached the maximum number configured by the network, the random access procedure will still be triggered.

For the above two situations, when the random access procedure is initiated, the UE can start the sr-RandomAccessTimer. The UE may perform qualified RS resource selection for the purpose of path loss and subsequent (re)transmission for random access. During the qualifying RS resource selection process, when the sr-RandomAccessTimer is running, the UE may keep performing the detection of qualifying RS resources until at least one qualifying RS resource is detected. In some embodiments, if the UE detects that the qualified RS resource does not exist, the UE may keep performing the detection of the qualified RS resource until the UE detects at least one qualified RS resource or the UE determines that the sr-RandomAccessTimer has expired. In some other embodiments, during the qualifying RS resource selection process, if the UE detects that the qualifying RS resource does not exist, and if the UE determines that the sr-RandomAccessTimer is still running, the UE may continue the qualifying RS resource after the backoff time detection process. Both the application of the back-off time and the continuation of the eligible RS resource detection process after the back-off time may be repeated until at least one eligible RS resource is detected or the sr-RandomAccessTimer expires. In some embodiments, the UE may choose a random backoff time according to a uniform distribution between 0 and a constant provided by the network.

When more than one qualified RS resource is detected by the UE, the UE selects one of the detected RS resources and one or more corresponding PRACH resources associated with the selected RS resource for path loss estimation and (re- )transmission.

In some embodiments, the above qualified RS resource detection behavior may be applied to each random access resource selection procedure during the random access procedure. In such an embodiment, the above qualified RS resource detection behavior is not only applied to the random access resource selection procedure at the initial initiation of the random access procedure (such as the first random access attempt of the random access procedure), but also A random access resource selection procedure that is applied to each subsequent random access attempt. For example, after transmission of the random access preamble (Msg1), the UE may monitor the network's response to Msg1, eg, a random access response (RAR). If the UE fails to receive a correct response to Msg1 within the configured time window, the UE may initiate another random access attempt. Or for contention-based random access procedures, if the UE fails to resolve the contention solution, the UE may initiate another random access attempt. In some embodiments, the UE may begin with a random access resource selection procedure whenever a subsequent random access attempt is initiated. In such an embodiment, the above qualified RS resource detection behavior may also be applied to the random access resource selection process in subsequent random access attempts.

The UE may stop the sr-RandomAccessTimer when the random access is considered to be completed successfully. For random access triggered by the transmission of SR, contention-based random access may be performed. With contention resolution completed, random access is considered successful.

When a timer such as sr-RandomAccessTimer expires before random access is successfully completed, the MAC entity may indicate random access problems to upper layers such as the RRC layer. By receiving the random access failure indication, the RRC layer may initiate an RRC connection re-establishment procedure.

I.(b). Control of random access triggered by requests from other SIs

In a 5G NR wireless system, system information is divided into two types, one is basic SI including MIB and SIB1, and the other is other SI. Basic SI is actively broadcast by the network. For example, the independent cell periodically broadcasts the basic SI. Other SIs will only be broadcast by the network when requested by at least one UE.

In some embodiments, the other SI may be requested by the RRC layer, the NAS layer or the application layer in the UE, or the other SI may be requested by the user. When other SI is requested, the RRC layer triggers the MAC entity to initiate the random access procedure and can start a timer called si-RandomAccessTimer.

The UE performs qualified RS resource selection for the purpose of pathloss estimation and subsequent (re)transmission for random access. During the qualifying RS resource selection process, when the si-RandomAccessTimer is running, the UE may keep performing the detection of qualifying RS resources until at least one qualifying RS resource is detected. In some embodiments, if the UE detects that the qualified RS resource does not exist, the UE may keep performing the detection of the qualified RS resource until at least one qualified RS resource is detected or the UE determines that the si-RandomAccessTimer timer has expired until. In some other embodiments, during the qualifying RS resource selection process, if the UE detects that the qualifying RS resource does not exist, and the UE determines that the si-RandomAccessTimer timer is still running, the UE may continue the qualifying process after the backoff time RS resource detection. Both the application of the back-off time and the continuation of the qualified RS resource detection process after the back-off time may be repeated until at least one qualified RS resource is detected or the si-RandomAccessTimer timer expires. In some embodiments, the UE may choose a random backoff time according to a uniform distribution between 0 and a constant provided by the network.

When more than one eligible RS resource is detected, one of the detected RS resources and the corresponding one or more PRACH resources associated with the selected RS resource are selected for pathloss estimation and (re- )transmission. In some embodiments, the above qualified RS resource detection behavior may be applied to each random access resource selection procedure during the random access procedure.

The si-RandomAccessTimer is stopped when the random access is deemed to have completed successfully. To facilitate requests for other SIs, the network may provide dedicated RACH configurations associated with SS blocks. In this case, the contention-free random access procedure may be performed using the PRACH preamble and one or more PRACH resources indicated in the dedicated RACH configuration. With the successful reception of the RAR dedicated to the SI request (eg, including only the random access preamble IDentifier), the random access is considered to be successfully completed. Contention-based random access may be performed if the network does not provide a dedicated RACH configuration associated with the SS block for the SI request. In this case, with the completion of contention resolution, random access is considered to be completed successfully.

A SI request is considered failed when a timer (eg, si-RandomAccessTimer) expires before random access is successfully completed. If the timer expires, the UE may also perform at least one of the following: (i) initiate a connection re-establishment procedure; or (ii) if the SI request is triggered by an upper layer, notify the corresponding upper layer that triggered the SI request of the SI acquisition failure.

II. Timers that control the qualifying reference signal (RS) resource selection process

3 illustrates an example reference signal resource selection process. At initiating operation 302, the user equipment may initiate a random access resource selection procedure. The random access resource selection process is a sub-process in the random access process.

At start operation 304, the user equipment may start a timer (eg, ra-ResourceSelectionTimer) when the random access resource selection procedure is initiated. While the timer is running, the UE keeps detecting eligible RS resources. The timer may be configured by the network and sent to the UE using eg system information or RRC signaling. In some embodiments, the time instance associated with the initiation of the timer may precede or coincide with the initiation of the random access resource selection procedure. Furthermore, in some embodiments, an exemplary timer may be started each time the random access resource selection procedure is initiated.

At stop operation 306, the timer may be stopped while the random access preamble transmission procedure is performed. In some embodiments, the timer is stopped when an eligible RS resource can be selected or detected by the user equipment.

The example process of FIG. 3 may also implement features associated with expiration of timers. Features from the following exemplary options may be implemented by the user equipment when the timer expires.

Exemplary option 1: In this embodiment, if the user equipment determines that the timer has expired, the MAC entity may indicate a random access problem to upper layers (eg, the RRC layer). If the random access is performed on a secondary cell (SCell), and if the random access is not a random access triggered by a beam failure, the MAC entity may consider the random access procedure to be unsuccessfully completed. In exemplary option 1, if the timer is not configured, or if the timer is configured such that the timer length is set to zero, the indication of a random access problem when the user equipment determines that no eligible RS resources are detected Or unsuccessful completion of the random access procedure, the random access issue or indication of unsuccessful completion of the random access procedure may be performed as discussed in Exemplary Option 1. Features associated with example option 1 may be performed in both a contention resolution process and a contention-free resolution process.

Exemplary option 2: In this embodiment, if the user equipment determines that the timer has expired, the user equipment may increase the number of random access resource selection procedures by a predetermined value, such as 1 and if the user equipment determines that the random access resource selection process The number of random access resource selection procedures does not reach the maximum number of random access resource selection procedures, the MAC entity may consider that the random access resource selection procedure has failed, and may initiate another random access resource selection procedure.

In some embodiments, the number of random access resource selection procedures may be set to one when a random access preamble transmission such as a random access attempt is initiated. In some embodiments, the maximum number of random access resource selection procedures may be equal to one plus one with a constant that controls the maximum number of random access resource selection procedures. For example, if the constant is denoted as ra-ResourceSelection-Max, the maximum number of random access resource selection procedures may be equal to ra-ResourceSelection-Max+1. The following example further illustrates the relationship between the number of random access selection procedures and the maximum number of random access resource selection procedures in some embodiments. For example, if the maximum number of random access resource selection procedures is equal to 5 (eg, ra-ResourceSelection-Max=5), the UE may perform a total of five random access resource selection procedures each time the timer expires. In such an embodiment, when the UE performs the fifth random access resource selection procedure (eg, when the number of random access resource selection procedures reaches 5) and the timer expires, the UE will is increased to 6, and it is determined that the number of random access selections has reached the maximum number of random access selection procedures (eg, ra-ResourceSelection-Max+1). The constant for ra-ResourceSelection-Max can be provided by the network.

In some embodiments, when the timer expires, another random access resource selection procedure may be initiated immediately. In some other embodiments, when the timer expires, another random access resource selection procedure may be initiated after applying the back-off time. In some embodiments, if the timer is not configured, or if the timer is configured such that the timer length is set to zero, then when the user equipment determines that no eligible RS resources are detected, another randomization is initiated after the backoff time Access resource selection process.

For example option 2, when the user equipment determines that the number of random access resource selection procedures reaches a maximum value, the MAC entity indicates the random access problem to the upper layer (eg, the RRC layer).

For example option 2, if the timer is not configured, or if the timer is configured with a length set to zero, when the user equipment determines that no eligible RS resources are detected, it may be as discussed in example option 2 In that case, the determination of the comparison of the number of random access resource selection procedures with the maximum value, the determination of the failure of the random access resource selection procedure, and the initiation of another random access resource selection procedure are performed. Features associated with example option 2 may be performed in both contention resolution and contention-free processes.

Exemplary option 3: In this embodiment, if the user equipment determines that the timer has expired, the MAC entity may consider that the random access resource selection procedure has failed, and may indicate the random access resource selection failure to an upper layer (such as the RRC layer) , and another random access resource selection procedure may be initiated.

In some embodiments, when the timer expires, another random access resource selection procedure may be initiated immediately. In some other embodiments, when the timer expires, another random access resource selection procedure may be initiated after applying the back-off time. In some embodiments, if the timer is not configured, or if the timer is configured such that the timer length is set to zero, then when the user equipment determines that no eligible RS resources are detected, another is initiated after the backoff time Random access resource selection process.

For example option 3, if the upper layer (such as the RRC layer) receives a certain or maximum number of random access resource selection failure indications, the upper layer may declare a radio link failure.

For example option 3, if the timer is not configured, or if the timer is configured with a length set to zero, then when the user equipment determines that no eligible RS resources are detected, as discussed in example option 3 , the MAC entity may consider that the random access resource selection procedure has failed, may indicate the random access resource selection failure to upper layers such as the RRC layer, and may initiate another random access resource selection procedure. Features associated with example option 3 may be performed in both contention resolution and contention-free processes.

The following two examples are provided to further illustrate the embodiments in Section II. Example 1 below shows an example of contention-based random access for the features described in example option 1 above. Example 2 below shows an example of contention-free random access for example option 2 as described above. As mentioned above, any of the exemplary options 1, 2, or 3 may be used for contention-based or contention-free random access.

Example 1 for Exemplary Option 1:

In Example 1, the UE performs initial access from RRC_IDLE and initiates contention-based random access. The UE performs random access according to information acquired from system information such as the RACH configuration associated with the SS block.

4 illustrates an example contention-based random access resource selection process using the specific timer feature of example option 1. FIG.

At a first initiating operation 400, when the UE performs initial access from RRC_IDLE, a random access procedure may be initiated in the MAC entity. At a second initiation operation 401, the MAC entity may initiate a random access resource selection procedure and may start a timer (eg, ra-ResourceSelectionTimer).

At determination operation 402, while the timer is running, the MAC entity determines whether an eligible RS resource is selected. During the random access resource selection procedure, the UE performs eligible RS resource selection. To further illustrate the selection or detection characteristics of operation 402, example RS resources may include SS blocks. In such an example, the UE may detect whether there are any SS blocks that satisfy the threshold provided in the system information of the first priority. If no SS blocks meeting the threshold are detected, the UE may then detect whether there are any SS blocks that allow the UE to meet the target received power of the RACH preamble with its maximum transmit power. In some embodiments, the actual act of performing RS resource selection can be left to the UE.

If an eligible RS resource is selected before the ra-ResourceSelectionTimer expires, the UE selects the preamble and PRACH occasion associated with the selected RS resource, and proceeds to stop operation 403 .

At determination operation 402, the UE may maintain eligible RS resource detection until at least one eligible RS resource is detected or the ra-ResourceSelectionTimer expires. If the user equipment determines that the ra-ResourceSelectionTimer expires, at indicating operation 409, the MAC entity indicates a random access problem to the upper layer, and the process ends.

At determining operation 402, if more than one eligible RS resource is detected, the UE selects one of the detected RS resources, and the corresponding one or more PRACH resources ( including preamble and PRACH occasions) for path loss estimation and (re)transmission.

At stop operation 403, the MAC entity may stop the ra-ResourceSelectionTimer. At performing operation 404, the MAC entity may perform a random access preamble transmission procedure. In some embodiments, perform operation 404 may be performed with or concurrently with stop operation 403 . In some other embodiments, performing operation 404 may be performed before stopping operation 403 . After the random access preamble is transmitted at performing operation 404, the MAC entity may begin receiving RARs within the RAR window. The length of the RAR window is obtained by the UE from system information.

At receive operation 405 , if the correct RAR corresponding to the preamble transmitted in performing operation 404 is successfully received by the UE within the RAR window, the process may continue with transmit operation 406 . Otherwise, if the UE determines that the correct RAR corresponding to the preamble transmitted in performing operation 404 is not received within the RAR window, the MAC entity may transmit the number of random access preambles (such as the number of random access attempts) to ) is incremented by a predetermined value, such as 1, and it can be determined whether the number of random access attempts has reached the maximum number. If the number of random access attempts is less than the maximum number, the MAC entity may return to the second initiation operation 401 to initiate another random access resource selection procedure and restart (eg, reset and start the ra-ResourceSelectionTimer). If the UE determines that the number of random access preamble transmissions has reached the maximum number, the MAC entity considers the random access unsuccessful and indicates a random access problem to the upper layer, and the process ends.

At transmit operation 406, Msg3 may be transmitted according to the UL grant obtained in the RAR. After transmitting Msg3, the MAC entity may start receiving Msg4 transmitted by the network.

At contention resolution operation 407, the MAC entity may determine whether contention resolution is resolved. If the correct Msg4 corresponding to Msg3 transmitted in transmit operation 406 is successfully received, contention resolution is considered resolved and the UE proceeds to completion operation 408 . Otherwise, if the correct Msg4 is not received during the contention_resolution time, the MAC entity may add a predetermined value, such as 1, to the number of random access preamble transmissions, such as the number of random access attempts, and may determine the random access attempt has reached the maximum value. If the number of random access attempts is less than the maximum number, the MAC entity may return to the second initiation operation 401 to initiate another random access resource selection procedure and restart the ra-ResourceSelectionTimer. If the number of random access preamble transmissions has reached the maximum number, the MAC entity considers the random access unsuccessful and indicates a random access problem to the upper layers, and the process ends.

At completion operation 408, the MAC entity considers the random access completed successfully and the process ends.

Example 2 for Exemplary Option 2:

In Example 2, the UE receives a handover command from the network and provides contention-free RACH resources in the handover command. For example, the dedicated RACH configuration associated with the CSI-RS resource may be provided in the handover command. In Example 2, the UE performs contention-free random access according to the information acquired in the handover command.

5 illustrates an exemplary contention-free random access resource selection process using the specific timer feature of exemplary option 2. At a first initiation operation 500, a random access procedure may be initiated in the MAC entity when the UE performs handover. The MAC entity may set the number of random access resource selection procedures to one, for example. At a second initiation operation 501, the MAC entity may initiate a random access resource selection procedure and start a ra-ResourceSelectionTimer.

At determining operation 502, the MAC entity may determine whether an eligible RS resource is selected. During the random access resource selection procedure, the UE performs eligible RS resource selection. To further illustrate the selection or detection characteristics of operation 502, examples of RS resources may include CSI-RS resources. In such an example, the UE may detect whether there are any CSI-RS resources that satisfy the threshold provided in the handover command of the first priority. If no CSI-RS resources meeting the threshold are detected, the UE may then detect whether there are any CSI-RS resources that allow the UE to meet the target received power of the RACH preamble with its maximum transmit power. In some embodiments, the actual act of performing RS resource selection may be left to the UE.

If an eligible RS resource is selected before the ra-ResourceSelectionTimer expires, the UE selects the preamble and PRACH occasion associated with the selected RS resource, and enters stop operation 503, where the MAC entity stops the ra-ResourceSelectionTimer.

At determining operation 502, the UE may keep performing eligible RS resource detection until at least one eligible RS resource is detected, or the ra-ResourceSelectionTimer expires. If the user equipment determines that the ra-ResourceSelectionTimer expires, at a second determination operation 507, a predetermined value such as 1 may be added to the number of random access resource selection procedures, and the MAC entity determines the random access resource selection procedures has reached the maximum value. If the number of random access resource selection procedures has reached a maximum value, at indicating operation 508, the MAC entity may indicate a random access problem to upper layers, and the procedure ends.

If the number of random access resource selection procedures is less than the maximum value, the MAC entity initiates another random access resource selection procedure and restarts (eg, resets and starts the ra-ResourceSelectionTimer). In this example, the maximum value of the random access resource selection process may be equal to ra-ResourceSelection-Max+1. ra-ResourceSelection-Max may be a constant provided by the network.

At determination operation 502, if more than one eligible RS resource is detected, the UE selects one of the detected RS resources, and the corresponding one or more PRACH resources (including preambles) associated with the selected RS resource codes and PRACH occasions) for path loss estimation and (re)transmission.

At performing operation 504, the MAC entity may perform a random access preamble transmission procedure. In some embodiments, perform operation 504 may be performed with or concurrently with stop operation 503 . In some other embodiments, performing operation 504 may be performed before stopping operation 503 .

After the random access preamble is transmitted at performing operation 504, the MAC entity may begin receiving RARs within the RAR window. The length of the RAR window is provided in the switch command.

At receiving operation 505, if the correct RAR corresponding to the preamble transmitted in performing operation 504 is successfully received within the RAR window, the MAC entity considers the random access procedure to be successfully completed, and the procedure is performed at operation 506 Finish. Otherwise, if the UE determines that the correct RAR corresponding to the preamble transmitted in performing operation 504 was not received within the RAR window, a predetermined value such as 1 may be added to the number of random access preamble transmissions (such as , the number of random access attempts), and the MAC entity determines whether the number of random access attempts has reached the maximum value. If the number of random access preamble transmissions is less than the maximum number, the MAC entity may reset the number of random access resource selection procedures to, eg, 1, and may return to the second initiation operation 501 to initiate another random access Resource selection process, and restart (eg, reset and start ra-ResourceSelectionTimer). If the number of random access preamble transmissions has reached the maximum number, the MAC entity considers the random access unsuccessful, and indicates to the upper layer a random access problem, and the process ends.

6 shows a block diagram of an example user equipment for implementing random access and timer features. User equipment includes one or more processors 610 that can read code from memory 605 and perform operations associated with other blocks of user terminal 600 . The user terminal includes a transmitter 615 to initiate random access procedures as described in this patent document. The user terminal also includes a receiver 620 that can receive signals from the base station. As described in this patent document, the module for random access 625 may initiate or execute a random access resource selection procedure or a random access procedure as described in this patent document. As described further in this patent document, the timer 630 may be used by the user equipment to start or stop the timer, or to determine whether the timer is running or has expired.

The term "exemplary" is used to mean "an example of" and does not imply an ideal or preferred embodiment unless stated otherwise.

Some of the embodiments described herein are described in the general context of a method or process, which in one embodiment may be implemented by a computer program product embodied in a computer-readable medium, the computer program product Computer-executable instructions, such as program code, are included to be executed by computers in a network environment. Computer readable media may include removable and non-removable storage devices including, but not limited to, read only memory (ROM), random access memory (RAM), compact disks (CDs), digital versatile disks (DVDs), and the like. Accordingly, computer-readable media may include non-transitory storage media. Program modules may generally include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. A computer (or processor) can execute instructions, associated data structures, and program modules that represent examples of program code for executing steps of the methods disclosed herein. The specific sequences of such executable instructions or associated data structures represent examples of corresponding acts for implementing the functions described in such steps or processes.

Some of the disclosed embodiments, modules, and blocks can be implemented as devices or modules using hardware circuits, software, or a combination thereof. For example, a hardware circuit may include discrete analog and/or digital components, such as integrated as part of a printed circuit board. Alternatively or additionally, the disclosed components or modules may be implemented as application specific integrated circuits (ASIC) and/or field programmable gate array (FGPA) devices. Some implementations may additionally or alternatively include a digital signal processor (DSP), which is a dedicated microprocessor with a structure optimized for the operational needs of digital signal processing associated with the functions disclosed herein. Similarly, the various components or sub-components within each module may be implemented in software, hardware or firmware. Connections between modules and/or components within modules may be provided using any of the connection methods and media known in the art, including but not limited to communications over the Internet, wired or wireless networks using appropriate protocols.

Although this document contains many details, these should not be construed as limitations on the scope of the claimed invention or what may be claimed, but rather as descriptions of particular features of particular embodiments. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as functioning in a particular combination, and even originally claimed as such, in some cases one or more features of the claimed combination may be deleted from that combination, and The claimed combinations may be directed to subcombinations or variants of subcombinations. Similarly, although operations are depicted in the figures in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in a sequential order, or that all operations shown be performed to obtain the desired result.

Only a few embodiments and examples have been described, and other embodiments, modifications, and changes are possible based on what is described and illustrated in this disclosure.

Claims (28)

1. A wireless communication method, comprising In response to a random access trigger event, a timer is started and a random access procedure is initiated by the user equipment, wherein the time instance associated with the start of the timer depends on the random access trigger event; and The random access procedure is performed by detecting at least one reference signal (RS) when the timer is running. 2. The wireless communication method of claim 1, wherein the performing of the random access procedure further comprises: in response to determining the absence of the RS; apply the backoff time; and After applying the backoff time, at least one RS is detected while the timer is running. 3. The wireless communication method of claim 1, wherein the RS is a qualified RS. 4. The wireless communication method of claim 3, wherein the qualified RS is a synchronization signal (SS) resource or a channel state information reference signal (CSI-RS) resource. 5. The wireless communication method according to claim 3, wherein the qualified RS includes resources satisfying a predetermined threshold, or allows the user equipment to satisfy a random access channel (RACH) preamble with the user equipment maximum transmit power Resource for the target received power of the code. 6. The wireless communication method according to claim 1, wherein the random access trigger event comprises: sending a scheduling request (SR), requesting system information (SI), performing initial access from RRC_IDLE to RRC_CONNECTED, performing RRC Re-establish connection, perform handover, perform RRC connection recovery, or recover from beam failure. 7. The wireless communication method according to claim 6, further comprising: determining the expiration of the timer; In response to the random access triggering event being the sending of the SR, indicating a random access problem to a first layer above the MAC entity by a medium access control (MAC) entity; and In response to the random access triggering event being the request SI, a failed SI request is indicated. 8. The wireless communication method of claim 7, wherein the first layer is a radio resource control (RRC) layer. 9. The wireless communication method of claim 7, wherein in response to the random access trigger event is the request SI: Initiate the connection re-establishment process. 10. The wireless communication method of claim 7, wherein in response to the random access trigger event is the request SI: In response to the request of the SI triggered by the second layer, the second layer above the RRC layer is notified of the failed SI request. 11. The wireless communication method of claim 10, wherein the second layer is a non-access stratum (NAS) layer or an application layer. 12. The wireless communication method of claim 1, wherein the time instance when the timer is started is before the initiation of the random access procedure triggered by the random access trigger event or at the same time. 13. The wireless communication method of claim 1, further comprising: In response to determining a successful random access procedure, the timer is stopped. 14. A wireless communication method comprising: The random access resource selection process is initiated by the user equipment; during a random access procedure, in response to initiation of the random access resource selection procedure, starting a timer; and The timer is stopped in response to detecting a reference signal (RS). 15. The wireless communication method of claim 14, wherein the RS is a qualified RS. 16. The wireless communication method of claim 15, wherein the qualified RS is a synchronization signal (SS) resource or a channel state information reference signal (CSI-RS) resource. 17. The wireless communication method of claim 15, wherein the qualified RS includes a resource satisfying a predetermined threshold, or allows the user equipment to satisfy a random access channel (RACH) with a maximum transmit power of the user equipment Resource for the target received power of the preamble. 18. The wireless communication method of claim 14, wherein a time instance associated with initiation of the timer precedes or coincides with the initiation of the random access resource selection procedure. 19. The wireless communication method of claim 14, further comprising: determining the expiration of the timer; and Random access problems are indicated to layers above the MAC entity by a medium access control (MAC) entity. 20. The wireless communication method of claim 14, further comprising: determining the expiration of the timer; After it is determined that the timer expires, the number of random access resource selection procedures is increased by a predetermined value. After determining that the timer expires, re-initiating a random access resource selection procedure in response to determining that the number of random access resource selection procedures is less than the maximum number of random access resource selection procedures; and After determining that the timer expires, in response to determining that the number of random access resource selection procedures is equal to the maximum number of random access resource selection procedures, by a medium access control (MAC) entity to the MAC entity The layers above indicate random access problems. 21. The wireless communication method of claim 20, wherein the random access resource selection procedure is re-initiated after a back-off time is applied. 22. The wireless communication method of claim 14, further comprising: determining the expiration of the timer; and indicating a random access resource selection failure to a layer above a medium access control (MAC) entity; and After determining that the timer expires, the random access resource selection procedure is re-initiated. 23. The wireless communication method of claim 22, wherein the random access resource selection procedure is re-initiated after a back-off time is applied. 24. The wireless communication method of claim 22, further comprising: A radio link failure is declared by the layer above the MAC entity in response to receiving a maximum number of random access resource selection failures. 25. An apparatus for wireless communication comprising a memory and a processor, wherein the processor reads code from the memory and implements the method of any one of claims 1 to 13. 26. A computer readable program storage medium having code stored thereon which, when executed by a processor, causes the processor to implement the method of any one of claims 1 to 13. 27. An apparatus for wireless communication comprising a memory and a processor, wherein the processor reads code from the memory and implements the method of any one of claims 14 to 24. 28. A computer readable program storage medium having stored thereon code which, when executed by a processor, causes the processor to implement the method of any one of claims 14 to 24.

Images