WO2022262707A1

WO2022262707A1 - Method, user equipment, and network node for feature based power ramping for random access

Info

Publication number: WO2022262707A1
Application number: PCT/CN2022/098588
Authority: WO
Inventors: Zhipeng LIN; Jonas SEDIN
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-06-18
Filing date: 2022-06-14
Publication date: 2022-12-22
Also published as: EP4356679A1

Abstract

The present disclosure is related to a UE, a network node, and methods for feature based power ramping for random access. A method at a UE for performing a random access (RA) procedure with a network node comprises: determining one or more first power parameters for physical random access channel (PRACH) transmission at least partially based on whether a first feature is to be requested or not; transmitting, to the network node, the PRACH transmission at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.

Description

METHOD, USER EQUIPMENT, AND NETWORK NODE FOR FEATURE BASED POWER RAMPING FOR RANDOM ACCESS

CROSS-REFERENCE TO RELATED APPLICATION (S)

This application claims priority to the PCT International Application No. PCT/CN2021/100922, entitled "METHOD, USER EQUIPMENT, AND NETWORK NODE FOR FEATURE BASED RANDOM ACCESS PROCEDURE" , filed on June 18, 2021, the PCT International Application No. PCT/CN2021/102258, entitled "METHOD, USER EQUIPMENT, AND NETWORK NODE FOR FEATURE BASED PREAMBLE GROUPING" , filed on June 25, 2021, and the PCT International Application No. PCT/CN2021/104301, entitled "METHOD, USER EQUIPMENT, AND NETWORK NODE FOR FEATURE BASED POWER RAMPING FOR RANDOM ACCESS" , filed on July 2, 2021, which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure is related to the field of telecommunication, and in particular, to a user equipment (UE) , a network node, and methods for feature based power ramping for random access.

Background

With the development of the electronic and telecommunications technologies, mobile devices, such as a mobile phone, a smart phone, a laptop, a tablet, a vehicle mounted device, becomes an important part of our daily lives. To support a numerous number of mobile devices, a highly efficient Radio Access Network (RAN) , such as a fifth generation (5G) New Radio (NR) RAN, will be required.

In order to be able to carry the data across the 5G NR RAN, data and information is organized into a number of data channels. By organizing the data into various channels, a 5G communications system is able to manage the data transfers in an orderly fashion and the system is able to understand what data is arriving and hence it is able to process the data in the required fashion. As there are many different types of data that need to be transferred -user data obviously needs to be transferred, but so does control information to manage the radio communications link, as well as data to provide synchronization, access, and the like. All of these functions are essential and require the transfer of data over the RAN.

In order to group the data to be sent over the 5G NR RAN, the data is organized in a very logical way. As there are many different functions for the data being sent over the radio communications link, they need to be clearly marked and have defined positions and formats. To ensure this happens, there are several different forms of data "channel" that are used. The higher level ones are "mapped" or contained within others until finally at the physical level, the channel contains data from higher level channels.

In this way there is a logical and manageable flow of data from the higher levels of the protocol stack down to the physical layer.

There are three main types of data channels that are used for a 5G RAN, and accordingly the hierarchy is given below.

- Logical channel: Logical channels can be one of two groups: control channels and traffic channels:

● Control channels: The control channels are used for the transfer of data from the control plane; and

● Traffic channels: The traffic logical channels are used for the transfer of user plane data.

- Transport channel: Is the multiplexing of the logical data to be transported by the physical layer and its channels over the radio interface.

- Physical channel: The physical channels are those which are closest to the actual transmission of the data over the radio access network /5G Radio Frequency (RF) signal. They are used to carry the data over the radio interface.

The physical channels often have higher level channels mapped onto them for providing a specific service. Additionally, the physical channels carry payload data or details of specific data transmission characteristics like modulation, reference signal multiplexing, transmit power, RF resources, etc.

The 5G physical channels are used to transport information over the actual radio interface. They have the transport channels mapped into them, but they also include various physical layer data required for the maintenance and optimization of the radio communications link between a UE and a base station (BS) .

There are three physical channels for each of the uplink and downlink: Physical Downlink Shared Channel (PDSCH) , Physical Downlink Control Channel (PDCCH) , and Physical Broadcast Channel (PBCH) for downlink, and Physical Random Access Channel (PRACH) , Physical Uplink Shared Channel (PUSCH) , and Physical Uplink Control Channel (PUCCH) for uplink.

Summary

According to a first aspect of the present disclosure, a method at a UE for performing a random access (RA) procedure with a network node is provided. The method comprises: determining one or more first power parameters for physical random access channel (PRACH) transmission at least partially based on whether a first feature is to be requested or not; transmitting, to the network node, the PRACH transmission at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.

In some embodiments, the first PRACH resource comprises at least one of: -a PRACH time/frequency resource; and -a PRACH preamble sequence. In some embodiments, the first feature comprises at least one of: -Msg3 repetition; -MsgA repetition; -a network slice; -small data transmission (SDT) ; -a UE with reduced capability (RedCap UE) ; -a random access in non-terrestrial network; and -a specific service type or UE priority. In some embodiments, the one or more first power parameters comprise at least one of: -a power ramping counter for PRACH transmission; -a power ramping step size for PRACH transmission; and -a preamble received target power for PRACH transmission. In some embodiments, each of the one or more first power parameters is one of: -a power parameter that is commonly configured for both PRACH transmission with the first feature to be requested and PRACH transmission without the first feature to be requested; -a power parameter that is specifically configured for PRACH transmission with the first feature to be requested; and -a power parameter that is specifically configured for PRACH transmission without the first feature to be requested.

In some embodiments, the method further comprises: transmitting, to the network node, the PRACH transmission at a second power, which is determined at least partially based on the one or more first power parameters and a power ramping counter that is maintained at the UE, by using a second PRACH resource that indicates a different result of whether the first feature is requested or not than that indicated by the first PRACH resource, in response to determining that all its previous RA attempts fail. In some embodiments, the power ramping counter is increased when starting a new attempt of the random access procedure no matter which PRACH resource is used in the new attempt. In some embodiments, the second power is calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

In some embodiments, the preamble received target power for calculating the second power is determined as follows:

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats,

is a power ramping step size used for the current PRACH transmission, and P _offset is the second power offset for compensating a power difference caused by different power ramping step sizes.

In some embodiments, P _offset is calculated as follows:

P _offset = (m -1) × (P _{step_1}-P _{step_2})

where m is the value of the power ramping counter when the PRACH transmission using the first PRACH resource is switched to the PRACH transmission using the second PRACH resource, and P _{step_1} is a power ramping step size used by the PRACH transmissions using the first PRACH resource.

In some embodiments, the power ramping counter is reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource. In some embodiments, whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource is determined by Radio Resource Control (RRC) signaling. In some embodiments, at least one of the following conditions is determined at least partially based on whether a PRACH occasion configured for the PRACH transmission is a shared PRACH occasion or a separate PRACH occasion: -whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -whether the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not; and -whether the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not.

In some embodiments, when the PRACH occasion configured for the PRACH transmission is a separate PRACH occasion, at least one of the following conditions is true: -the power ramping counter is reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource; and -the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource. In some embodiments, when the PRACH occasion configured for the PRACH transmission is a shared PRACH occasion, at least one of the following conditions is true: -the power ramping counter is kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -the preamble received target power for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource; and -the power ramping step size for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource.

In some embodiments, any PRACH transmission in the random access procedure that uses a PRACH resource indicating that the first feature is not requested is a part of Type-1 and/or Type-2 random access procedure without the first feature requested. In some embodiments, before the step of transmitting, to the network node, the PRACH transmission at a first power, the method further comprises: transmitting, to the network node, one or more PRACH transmissions by using a third PRACH resource until the random access procedure is successful or until switching the random access procedure from using the third PRACH resource to using the first PRACH resource. In some embodiments, the first power is calculated at least partially based on a preamble received target power that is compensated by a first power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

In some embodiments, the preamble received target power for calculating the first power is determined as follows:

P _n = P ₀ + Δp + (n -1) × P _{step_1} + P _{offset_1}

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_1} is a power ramping step size used for the current PRACH transmission, and P _{offset_1} is the first power offset for compensating a power difference caused by different power ramping step sizes.

In some embodiments, P _{offset_1} is calculated as follows:

P _{offset_1}= (m -1) × (P _{step_3} -P _{step_1})

where m is the value of the power ramping counter when the PRACH transmission using the third PRACH resource is switched to the PRACH transmission using the first PRACH resource, and P _{step_3} is a power ramping step size used by the PRACH transmissions using the third PRACH resource.

In some embodiments, the second power is calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

P _n = P ₀ + Δp + (n -1) × P _{step_2} + P _{offset_1} + P _{offset_2}

where Pn is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_2} is a power ramping step size used for the current PRACH transmission, and P _{offset_2} is the second power offset for compensating a power difference caused by different power ramping step sizes.

In some embodiments, P _{offset_2} is calculated as follows:

P _{offset_2} = (k -m + × (P _{step_1}-P _{step_2})

where k is the value of the power ramping counter when the PRACH transmission using the first PPACH resource is switched to the PPACH transmission using the second PPACH resource.

In some embodiments, the random access procedure comprises more than one switching between PPACH transmissions using different PPACH resources, which indicate that different combinations of one or more features are requested or not, wherein a power offset is determined for each switching, wherein a power used for a PPACH transmission is determined at least partially based on all the power offsets that are determined for all the switching before the PRACH transmission.

In some embodiments, the method further comprises: receiving, from the network node, a random access response (RAR) comprising an indicator indicating whether the first feature is to be used or not; and transmitting, to the network node, a Msg3 with or without the first feature enabled depending on the received indicator.

According to a second aspect of the present disclosure, a UE is provided. The UE comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the first aspect.

According to a third aspect of the present disclosure, a method at network node for performing a random access procedure with a UE is provided. The method comprises: transmitting, to the UE, a configuration indicating at least one of: -a power ramping step size for PRACH transmission; -a preamble received target power for PRACH transmission; -whether a power ramping counter is reset or kept increasing when switching the random access procedure from using a first PRACH resource to using a second PRACH resource; and -whether a shared or a separate PRACH occasion is configured for PRACH transmission.

According to a fourth aspect of the present disclosure, a network node is provided. The network node comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the third aspect.

According to a fifth aspect of the present disclosure, a computer program comprising instructions is provided. The instructions, when executed by at least one processor, cause the at least one processor to carry out the method of any of the first or third aspect.

According to a sixth aspect of the present disclosure, a carrier containing the computer program of the fifth aspect is provided. The carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

According to a seventh aspect of the present disclosure, a telecommunications system is provided. The telecommunications system comprises one or more UEs of the second aspect; and at least one network node of the fourth aspect.

Brief Description of the Drawings

Fig. 1 shows flow charts illustrating exemplary Type-1 and Type-2 RA procedures, respectively, with which a UE and gNB according to an embodiment of the present disclosure may be operable.

Fig. 2 is a diagram illustrating an exemplary one-to-one mapping between SSBs and PRACH occasions with which a UE and gNB according to an embodiment of the present disclosure may be operable.

Fig. 3 is a diagram illustrating an exemplary many-to-one mapping between SSBs and PRACH occasions with which a UE and gNB according to an embodiment of the present disclosure may be operable.

Fig. 4 is a flow chart illustrating an exemplary method at a UE for feature based power ramping for random access according to an embodiment of the present disclosure.

Fig. 5 is a flow chart illustrating an exemplary method at a network node for feature based power ramping for random access according to an embodiment of the present disclosure.

Fig. 6 schematically shows an embodiment of an arrangement which may be used in a UE or a network node according to an embodiment of the present disclosure.

Fig. 7 is a block diagram of an exemplary UE according to an embodiment of the present disclosure.

Fig. 8 is a block diagram of an exemplary network node according to an embodiment of the present disclosure.

Fig. 9 schematically illustrates a telecommunication network connected via an intermediate network to a host computer according to an embodiment of the present disclosure.

Fig. 10 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection according to an embodiment of the present disclosure.

Fig. 11 to Fig. 14 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station, and a user equipment according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, the present disclosure is described with reference to embodiments shown in the attached drawings. However, it is to be understood that those descriptions are just provided for illustrative purpose, rather than limiting the present disclosure. Further, in the following, descriptions of known structures and techniques are omitted so as not to unnecessarily obscure the concept of the present disclosure.

Those skilled in the art will appreciate that the term "exemplary" is used herein to mean "illustrative, " or "serving as an example, " and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms "first" , "second" , "third" , "fourth, " and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term "step, " as used herein, is meant to be synonymous with "operation" or "action. " Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.

Conditional language used herein, such as "can, " "might, " "may, " "e.g., " and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. Also, the term "or" is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Further, the term "each, " as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term "each" is applied.

The term "based on" is to be read as "based at least in part on. " The term "one embodiment" and "an embodiment" are to be read as "at least one embodiment. " The term "another embodiment" is to be read as "at least one other embodiment. " Other definitions, explicit and implicit, may be included below. In addition, language such as the phrase "at least one of X, Y and Z, " unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limitation of example embodiments. As used herein, the singular forms "a" , "an" , and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" , "comprising" , "has" , "having" , "includes" and/or "including" , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. It will be also understood that the terms "connect (s) , " "connecting" , "connected" , etc. when used herein, just mean that there is an electrical or communicative connection between two elements and they can be connected either directly or indirectly, unless explicitly stated to the contrary.

Of course, the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope and essential characteristics of the disclosure. One or more of the specific processes discussed below may be carried out in any electronic device comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs) . In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Although multiple embodiments of the present disclosure will be illustrated in the accompanying Drawings and described in the following Detailed Description, it should be understood that the disclosure is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications, and substitutions without departing from the present disclosure that as will be set forth and defined within the claims.

Further, please note that although the following description of some embodiments of the present disclosure is given in the context of 5G NR, the present disclosure is not limited thereto. In fact, as long as a random access procedure is involved, the inventive concept of the present disclosure may be applicable to any appropriate communication architecture, for example, to Global System for Mobile Communications (GSM) /General Packet Radio Service (GPRS) , Enhanced Data Rates for GSM Evolution (EDGE) , Code Division Multiple Access (CDMA) , Wideband CDMA (WCDMA) , Time Division -Synchronous CDMA (TD-SCDMA) , CDMA2000, Worldwide Interoperability for Microwave Access (WiMAX) , Wireless Fidelity (Wi-Fi) , 4th Generation Long Term Evolution (LTE) , LTE-Advance (LTE-A) , or 5G NR, etc. Therefore, one skilled in the arts could readily understand that the terms used herein may also refer to their equivalents in any other infrastructure. For example, the term "User Equipment" or "UE" used herein may refer to a terminal device, a mobile device, a mobile terminal, a mobile station, a user device, a user terminal, a wireless device, a wireless terminal, or any other equivalents. For another example, the term "gNB" used herein may refer to a network node, a base station, a base transceiver station, an access point, a hot spot, a NodeB, an Evolved NodeB, a network element, or any other equivalents. Further, please note that the term "indicator" used herein may refer to a parameter, a coefficient, an attribute, a property, a setting, a configuration, a profile, an identifier, a field, one or more bits/octets, an information element, or any data by which information of interest may be indicated directly or indirectly.

Further, following 3GPP documents are incorporated herein by reference in their entireties:

- 3GPP TS 38.321 V16.4.0 (2021-03) , 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Medium Access Control (MAC) protocol specification (Release 16) ; and

- 3GPP TS 38.331 V16.4.1 (2021-03) , 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 16) .

When a UE wants to access to a 5G NR network, it has to synchronize in downlink as well as in uplink. Downlink synchronization may be obtained after successfully decoding Synchronous Signal and PBCH block (SSB) . In order to establish uplink synchronization and an RRC connection, the UE has to perform a random access procedure.

Fig. 1 shows flow charts illustrating exemplary Type-1 and Type-2 RA procedures, respectively, with which a UE and gNB according to an embodiment of the present disclosure may be operable. As shown in Fig. 1, there are two types of RA procedures:

- Type-1 RA procedure, also known as 4-step RACH, or 4-step RA procedure; and

- Type-2 RA procedure, also known as 2-step RACH, or 2-step RA procedure.

Further, RA procedures may also be classified into Contention Based Random Access (CBRA) or Non Contention or Contention Free Random Access (CFRA) depending on how its resource is selected. In the contention based RA procedure, a UE may select a preamble randomly from a pool of preambles shared with other UEs. This means that the UE has a potential risk of selecting a same preamble as another UE and subsequently may experience conflict or contention. The gNB may use a contention resolution mechanism to handle this type of access requests. In this procedure, the result is random and not all RA succeeds.

CFRA is the mode where the UE performs random access in resources where there is no contention, i.e., the UE is specifically allocated a random access resource. In 4-step CFRA, the non-contention is ensured by giving the UE one or a set of preambles, and in 2-step CFRA, the non-contention is ensured by similarly giving the UE one or a set of preambles as well as MsgA PUSCH resources. CFRA use cases examples may comprise:

- Handover (Reconfiguration with sync) . The source cell will give the random access configuration of the target cell; and

- Beam Failure recovery (BFR) .

Referring to the top flow chart of Fig. 1, an exemplary 4-step RA procedure may comprise four steps 125 to 155 for a UE 110 to access a gNB 120 after necessary system information, which is broadcasted by the gNB 120, is obtained at the

steps

105 and 115.

At step 105, the UE 110 may receive a Master Information Block (MIB) from the gNB 120 by detecting an SSB which may comprise a Primary Synchronous Signal (PSS) , a Secondary Synchronous Signal (SSS) , and a PBCH carrying the MIB. Upon successful reception and decoding of the MIB, the UE 110 may determine time/frequency positions for monitoring Remaining Minimum System Information (RMSI) or System Information Block 1 (SIB1) broadcasted by the gNB 120, for example, by a pdcch-ConfigSIB1 information element (IE) comprised in the MIB.

At step 115, the UE 110 may receive the RMSI and Other System Information (OSI) from the gNB 120. For example, the UE 110 may receive and decode the RMSI (SIB1) based on the information determined at the step 105 to determine time/frequency positions for monitoring OSI broadcasted by the gNB 120, for example, by a searchSpaceOtherSystemInformation IE comprised in the SIB1. Further, the UE 110 may also obtain any parameters necessary for the 4-step RA procedure. For example, the UE 110 may determine a set of preambles by a RACH--ConfigCommon IE which can be used later during the 4-step RA procedure.

At step 125, the UE 110 may transmit a preamble which is selected from the set of preambles determined at the step 115 or otherwise determined to the gNB 120 in Msg1.

At step 135, upon reception of Msg1, the gNB 120 may select a Temporary Cell -Radio Network Temporary Identifier (TC-RNTI) and uplink and downlink scheduling resources for the UE 110. Then, the gNB 120 may transmit an RA response (RAR or Msg2) over PDCCH/PDSCH. The response may contain the RA-preamble identifier, timing alignment information, initial uplink grant, and the TC-RNTI. One PDSCH may carry RA responses to multiple UEs. On the other hand, after transmitting the preamble, the UE 110 may monitor the PDCCH and wait for the RAR within an RA response window:

- If the UE 110 receives a response containing an RA-preamble identifier which is the same as the identifier contained in the transmitted RA preamble, the response is successful. The UE 110 may then transmit uplink scheduling information later.

- If the UE 110 does not receive a response within the RA response window or fails to verify the response, the response fails. In this case, if the number of RA attempts is less than the upper limit (e.g., 10) , the UE 110 may retry the RA procedure. Otherwise, the RA procedure fails.

Further, the UE 110 may use the timing alignment information comprised in the RAR to adjust the timing of any subsequent PUSCH transmission, allowing PUSCH to be received at the gNB 120 with a timing accuracy within the cyclic prefix (CP) . Without this timing advance functionality, a very large CP would be needed in order to be able to demodulate and detect PUSCH, unless the system is applied in a cell with very short distance between the UE 110 and the gNB 120. Since NR will also support larger cells, there is a need for providing a timing advance to the UE 110.

At step 145, the UE 110 may transmit uplink scheduling information (Msg3) over the PUSCH. The signaling messages and information transmitted by the UE 110 may vary across different RA scenarios and some examples are listed below:

- Initial RRC connection setup: The RRCSetupRequest message (carrying NAS UE_ID) is transmitted over the common control channel (CCCH) in TM at the Radio Link Control (RLC) layer. The message is not segmented.

- RRC connection reestablishment: The RRC Reestablishment Request message (not carrying the NAS message) is transmitted over the CCCH in TM at the RLC layer. The message is not segmented.

- Handover: Contention-based RA, instead of contention-free RA, is triggered if the UE 110 accesses the target cell and no dedicated preambles are available during a handover. The RRC Handover Confirm message and C-RNTI are transmitted over the dedicated control channel (DCCH) . If required, a buffer status report (BSR) may also be carried.

- Other scenarios: At least the C-RNTI of the UE 110 may be transmitted.

At step 155, after transmitting the Msg3, a contention resolution timer may be started at the UE 110. The gNB 120 may assist the UE 110 in contention resolution using the C-RNTI on the PDCCH or using the UE Contention Resolution Identity IE on the PDSCH.

The UE 110 may keep monitoring the PDCCH before the timer expires and considers the contention resolution successful and stops the timer if either of the following conditions is met:

- The UE 110 receives a PDCCH on its C-RNTI.

- The UE 110 successfully decodes the MAC PDU addressed by the temporary C-RNTI. Specifically, the UE Contention Resolution Identity IE received over the PDSCH is the same as that carried in Msg3 sent by the UE.

If the contention resolution timer expires, the UE 110 may consider the contention resolution failed. Then, the UE 110 may perform the RA procedure again if the number of RA attempts has not reached the upper limit. If the number of RA attempts has reached its upper limit, the RA procedure fails.

In non-contention based Random Access or CFRA, the preamble may be pre-allocated by the gNB 120 and such preambles may be known as dedicated random access preamble. The dedicated preamble may be provided to the UE 110 either via RRC signalling (e.g., allocated preamble (s) can be specified within an RRC message) or PHY Layer signalling (e.g., DCI on the PDCCH) . Therefore, there is no preamble conflict. When dedicated resources are insufficient, the gNB 120 may instruct UEs to initiate contention-based RA.

The gNB 120 may allocate an RA preamble to the UE 110 and sent it using an RRC message or DCI signaling. Some scenarios are listed below:

- Handover: The MobilityControlInfo IE sent by the source gNB may carry the allocated preamble;

- DL Data Arrival: When downlink data arrives at the gNB 120, the gNB 120 may instruct the UE 110 to initiate an RA procedure through DCI over PDCCH, which carries the allocated preamble;

- Non-Standalone (NSA) networking: When NR cells are added in NSA, the gNB 120 may instruct the UE 110 to initiate an RA procedure through the PDCCH, which carries the allocated preamble.

Referring to the bottom flow chart of Fig. 1, an exemplary 2-step RA procedure may comprise two steps 185 and 195 for a UE 110 to access a gNB 120 after necessary system information, which is broadcasted by the gNB 120, is obtained at the

steps

165 and 175.

Similar to the step 105, at step 165, the UE 110 may receive a MIB from the gNB 120 by detecting an SSB. Upon successful reception and decoding of the MIB, the UE 110 may determine time/frequency positions for monitoring RMSI or SIB1 broadcasted by the gNB 120.

Similar to the step 115, at step 175, the UE 110 may receive the RMSI and OSI from the gNB 120. For example, the UE 110 may receive and decode the RMSI (SIB1) based on the information determined at the step 105 to determine time/frequency positions for monitoring OSI broadcasted by the gNB 120, for example, by a searchSpaceOtherSystemInformation IE comprised in the SIB1. Further, the UE 110 may also obtain any parameters necessary for the 2-step RA procedure. For example, the UE 110 may determine available time/frequency occasions for PRACH by a msgA-ConfigCommon IE comprised in the SIB1, which can be used later during the 2-step RA procedure.

Similar to the step 125, at the step 185, the UE 110 may transmit to the gNB 120 an RA preamble (MsgA) , which may be pre-allocated by the gNB 120 when it is a CFRA procedure, together with higher layer data such as an RRC connection request possibly with some small additional payload on PUSCH. In such a case, no confliction with other UEs will happen.

Similar to the step 135, the gNB 120 may transmit an RA response (MsgB) to the UE 110. Since no conflict with other UEs will occur, and the steps for contention resolving (e.g., Msg3 and Msg4 in the 4-step RA procedure) may be omitted.

In the handover scenario, the RA response may contain the timing alignment information and initial uplink grant. In the DL data arrival scenario, when downlink data arrives at the gNB 120, the RA response may contain the timing alignment information and RA preamble identifier (RAPID) . In the NSA networking scenario, when NR cells are added in NSA, the RA response may contain the timing alignment information and RAPID.

Please note that although Fig. 1 shows a 4-step contention-based RA procedure (or CBRA of Type 1) and a 2-step non-contention-based RA procedure (or CFRA of Type 2) , the present disclosure is not limited thereto. In other embodiments, other RA procedures may also be applicable, such as, a 4-step non-contention-based RA procedure (or CFRA of Type 1) and/or a 2-step contention-based RA procedure (or CBRA of Type 2) .

In 3GPP RAN#90e, the following objectives have been approved for NR coverage enhancement work item in NR Rel-17 for PUSCH:

● Specification of PUSCH enhancements [RAN1, RAN4]

○ Specify the following mechanisms for enhancements on PUSCH repetition type A [RAN1]

■ Increasing the maximum number of repetitions up to a number to be determined during the course of the work.

■ The number of repetitions counted on the basis of available UL slots.

○ Specify mechanism (s) to support transport block (TB) processing over multi-slot PUSCH [RAN1]

■ TB size (TBS) determined based on multiple slots and transmitted over multiple slots.

○ Specify mechanism (s) to enable joint channel estimation [RAN1, RAN4]

■ Mechanism (s) to enable joint channel estimation over multiple PUSCH transmissions, based on the conditions to keep power consistency and phase continuity to be investigated and specified if necessary by RAN4 [RAN1, RAN4]

Potential optimization of DMRS location/granularity in time domain is not precluded

■ Inter-slot frequency hopping with inter-slot bundling to enable joint channel estimation [RAN1]

● Specification of PUCCH enhancements [RAN1, RAN4]

○ Specify signaling mechanism to support dynamic PUCCH repetition factor indication [RAN1]

○ Specify mechanism to support DMRS bundling across PUCCH repetitions [RAN1, RAN4]

● Specify mechanism (s) to support Type A PUSCH repetitions for Msg3 [RAN1]

In some embodiments of the present disclosure, the Type A PUSCH repetitions for Msg3 will be described.

As already described with reference to Fig. 1, two types of random access procedures are supported in NR till release 16, where a MsgA PUSCH or a Msg3 PUSCH transmission is used for transmission of RRC setup request message in 2-step RACH RA type and 4-step RA type, respectively. Neither Msg3 PUSCH nor MsgA PUSCH can be repeated in NR up to Rel-16.

In both 4-step RACH and 2-step RACH, PRACH resources may be selected based on the SSB selection and a SSB to RACH occasion (RO) /preamble mapping. Detailed procedures of PRACH resource selection may be found in section 5.1.2 and 5.1.2a of 3GPP TS 38.321 for 4-step RACH and 2-step RACH, respectively.

The mapping between SSB and PRACH occasions may be one-to-one, one-to-many, and many-to-one in a predetermined order specified in standard. For example, Fig. 2 and Fig. 3 show exemplary one-to-one and many-to-one mapping between SSB and PRACH occasions, respectively.

When a UE (e.g., the UE 110) determines a good enough SSB beam with Synchronous Signal -Reference Signal Received Power (SS-RSRP) above an RSRP threshold (e.g., rsrp-ThresholdSSB) , a preamble in the set of one or more preambles in a PRACH occasion mapped to this SSB may be selected for the random access, then when the gNB (e.g., the gNB 120) detects the preamble, the determined SSB beam for this UE may be known indirectly to some extent so that determined beam can be used for transmitting signals to or receiving signals from this UE.

Fig. 2 shows four SSBs (e.g., SSB 0, SSB1, SSB2, and SSB3) broadcasted by the gNB 120 and four PRACH occasions for the UE 110 to transmit its PRACH for its random access procedure. As shown in Fig. 2, there is one-to-one mapping between the four SSBs and four PRACH occasions, which is indicated by the arrows. After the UE 110 detects the four SSBs and select one of them, for example, the SSB with the highest SS-RSRP (e.g., SSB 1) , the UE 110 may choose the PRACH occasion mapped to the SSB 1 for its PRACH transmission. By detecting the PRACH received over the PRACH occasion, the gNB 120 may determine which of the SSBs is selected by the UE 110 (i.e., SSB 1) and corresponding radio resources may be assigned accordingly based on this selection.

Fig. 3 shows four SSBs (e.g., SSB 0, SSB1, SSB2, and SSB3) broadcasted by the gNB 120 and two PRACH occasions for the UE 110 to transmit its PRACH for its random access procedure. As shown in Fig. 3, there is many-to-one mapping between the four SSBs and two PRACH occasions, which is indicated by the arrows. After the UE 110 detects the four SSBs and select one of them, for example, the SSB with the highest SS-RSRP (e.g., SSB 3) , the UE 110 may choose the PRACH occasion mapped to the SSB 3 for its PRACH transmission. By detecting the PRACH received over the PRACH occasion, the gNB 120 may determine which ones of the SSBs are selected by the UE 110 (i.e., SSB2 or SSB3) and corresponding radio resources may be assigned accordingly based on this selection.

Please note that the present disclosure is not limited thereto. In some other embodiments, a different number of SSBs and/or a different number of PRACH occasions and/or a different mapping may be provided. Further, although it looks like, in Fig. 2 and Fig. 3, the SSBs and the PRACH occasions are located within a same frequency band, they actually may be not. In some embodiments, they may be located within different frequency bands, for example, different resource elements (REs) , different resource blocks (RBs) , different bandwidth parts (BWPs) , or even different carriers.

In 4-step RACH, PRACH transmission may be re-attempted if the maximum number of reattempts has not been reached in the following cases:

- UE fails in receiving an expected RAR message within the RAR window;

- UE fails in receiving an expected msg4 for contention resolution.

Similarly, in 2-step RACH, MsgA transmission may be re-attempted if the maximum number of reattempts has not been reached in the following case:

- UE fails in receiving an expected RAR message in MsgB within the RAR window.

Please note that in 2-step RACH both MsgA PUSCH and MsgA PRACH parts will be re-attempted.

A UE may calculate the PRACH transmit power for the reattempt of the preamble based on the most recent estimated pathloss, the configured preamble received target power (the RRC parameter preambleReceivedTargetPower) , a power ramping step size (the RRC parameter powerRampingStep) and a power ramping counter that is a UE-internal variable in the MAC layer. The power ramping means that the UE will increase its power with every re-attempt until the maximum attempts have been reached. In 4-step random access, the maximum number of attempts is limited by the RRC parameter preambleTransMax, which is defined as the maximum number of preamble transmissions before the UE declares a failure.

During the discussions in the meetings from 3GPP RAN1 #104-e, the first meeting of the NR coverage enhancement work item in Rel-17, to 3GPP RAN1 #105-e, following agreements have been made regarding the Msg3 repetition criteria:

● UE determines a separate PRACH resource (separate preamble and/or separate PRACH occasions) based at least on RSRP of the downlink pathloss reference and the RSRP threshold;

● Based on the PRACH resource on which a PRACH is detected, gNB is aware of whether a Msg3 repetition can be enabled for the UE sending this PRACH.

Based on the agreement, at least preamble partitioning or grouping (i.e., a separate group of preambles on the PRACH occasions shared with legacy PRACH transmission) will be supported for requesting Msg3 repetition.

Agreement: For Msg3 PUSCH repetition, support the following modified Option 2-1.

● Option 2-1: For UE requested Msg3 PUSCH repetition with gNB indicating the number of repetitions,

○ A UE can request Msg3 PUSCH repetition via separate PRACH resources (For further study (FFS) details, e.g., separate PRACH occasion or separate PRACH preamble in case of shared PRACH occasions after SSB association, etc. ) .

■ Whether a UE would request is based on some conditions, e.g., measured SS-RSRP threshold, which may or may not have spec impact.

○ If Msg3 PUSCH repetition is requested by UE, gNB decides whether to schedule Msg3 PUSCH repetition or not. If scheduled, gNB decides the number of repetitions for Msg3 PUSCH 3 (re) -transmission.

○ FFS the UE capability of supporting Msg3 PUSCH repetition can be reported after initial access procedure as usual

○ FFS details if any.

Agreement: A UE requests Msg3 PUSCH repetition at least when the RSRP of the downlink pathloss reference is lower than an RSRP threshold.

● FFS the determination of the RSRP threshold.

Agreement:

● For requesting Msg3 PUSCH repetition, support the following:

○ Use separate preamble with shared RO configured by the same PRACH configuration index with legacy UEs.

■ FFS whether to introduce a PRACH mask to indicate a sub-set of ROs associated with a same SSB index within an SSB-RO mapping cycle for requesting Msg3 repetition for a UE.

■ FFS definition of shared RO (e.g., whether the shared RO can be an RO with preamble (s) for 4-step RACH only or with preambles for both 4-step RACH and 2-step RACH) .

○ FFS whether or not to additionally support one (&only one) more option:

■ E.g., option 2: Use separate RO configured by a separate PRACH configuration index from legacy UEs

■ E.g., Option 3: Use separate RO, which include:

the separate RO configured by a separate RACH configuration index from legacy UE, and

the remaining RO (if any) configured, by the same PRACH configuration index with legacy UEs, which cannot be used by legacy rules for PRACH transmission.

When performing a random access procedure, a UE might have to switch its random access method or stop performing the random access procedure. When PRACH is reattempted and switching between legacy RA and RA for requesting Msg3 repetition happens, how to deal with the power ramping should be specified considering whether the PRACH resource for requesting Msg3 repetition is separately configured or not. Further, when multiple features are indicated by multiple different types of PRACH resources, how to do power ramping among them also needs to be addressed.

Some embodiments of the present disclosure provide methods on how power ramping of random access re-attempts may be performed along with Msg3 repetitions and/or other new features. Some embodiments of the present disclosure provide a set of procedures to allow for optimized power ramping of re-attempts when performing Msg3 repetition random access attempts and the RA reattempts for indicating other new features. With these embodiments, a set of procedures may be provided to allow for optimized power ramping of re-attempts when performing Msg3 repetition random access attempts and the RA reattempts for indicating other new features.

Some embodiments of the present disclosure deal with power ramping of random access reattempt with Msg3 repetitions. In some embodiments, PRACH resource may be the PRACH time frequency resources and/or PRACH preamble sequences. In some embodiments, the "Msg3 repetition PRACH resource selection" may refer to the PRACH resource selection based on the conditions on whether a PRACH resource used for requesting Msg3 repetition may be selected. Further, "Msg3 repetition PRACH resource" may be the PRACH resource separately configured for UE to request Msg3 repetition. Further, "Msg3 repetition PRACH transmission" may refer to the PRACH transmissions on the PRACH resources used for requesting Msg3 repetition.

In some embodiments, the "legacy RA" , "legacy PRACH" may refer to the random access with PRACH transmissions on PRACH resources not for requesting Msg3 repetition. In some embodiments, the "SSB selection" means the SSB selection for further PRACH resource selection as PRACH resources are always associated to SSBs.

The determination of the power of PRACH may be related to a power ramping step size, the preamble received target power, a power ramping counter, and/or the pathloss estimate. For power control of PRACH requesting Msg3 repetition, in different use cases, different configurations may be needed meaning that a more flexible configuration may be needed. In some embodiments, the methods on determination of power ramping for PRACH requesting Msg3 repetition are provided.

In some embodiments, the power ramping step size for PRACH transmission requesting Msg3 repetition may be separately configured. This is beneficial because a more flexible power ramping step can be configured specifically for the PRACH transmissions for requesting Msg3 repetition. For example, when UEs in a cell are expected to be in a power saving mode, while the power ramping is caused by bad Msg3 performance instead of bad Msg1 performance, a smaller power ramping step may be enough. When UEs in the cell are expected to be in normal power consumption mode and in latency critical communication, a faster and more reliable random access may be required, and therefore a larger power ramping step may be configured along with the Msg3 repetition requested.

In some embodiments, the power ramping step size for PRACH transmission requesting Msg3 repetition may be the same as legacy RA. In this way, it avoids additional signaling to indicate the power ramping step size for PRACH transmission requesting Msg3 repetition, which may be enough in some cases e.g. when the load of the system is not that high meaning that the collision probability of PRACH transmissions is ow.

In some embodiments, the preamble received target power for PRACH transmission in RA supporting Msg3 repetition may be separately configured. This provides a more flexible preamble received target power that can be configured specifically for the PRACH transmissions for requesting Msg3 repetition. Even for initial PRACH transmission with Msg3 repetition requested, for example, with a larger initial preamble received target power configured, a more reliable Msg1 and Msg3 transmission can be achieved from the beginning for fast random access.

In some embodiments, the preamble received target power for PRACH transmission in RA supporting Msg3 repetition may be the same as legacy RA. In this way, it avoids additional signaling to indicate the preamble received target power for PRACH transmission requesting Msg3 repetition, which may be enough in some cases, for example, when the load of the system is not that high meaning that the collision probability of PRACH transmissions is low.

In some embodiments, "legacy RA" mentioned in the above embodiments may be 2-step RA and/or 4-step RA with PRACH resources not for requesting Msg3 repetition.

When a switching happens between RA with one type of PRACH resource and RA with another type of PRACH resource, whether to continue doing power ramping of PRACH or the power of PRACH should be reset may depend on different use cases.

In some embodiments, for switching between legacy PRACH and Msg3 repetition PRACH, the power ramping counter may continue increasing after switching. This can for instance help a UE succeed random access quicker, since moving to the initial transmit power after having already performed the legacy PRACH will mean that one would still have to "compete" with UEs that are performing their first random access transmissions but having chosen Msg3 repetitions first.

For example, when the number of UEs supporting Msg3 repetition is greater than the number of UEs not supporting Msg3 repetitions in the system, the collision of PRACH transmissions on the PRACH resources for requesting Msg3 repetition may be more serious and the UE may switch from Msg3 repetition PRACH transmission to legacy PRACH transmission. In this case, the target power level follows the legacy PRACH transmission power control formula plus an offset, where the offset may be calculated as follows:

OFFSET= (N-1) × (PREAMBLE_POWER_RAMPING_STEP_MSG3REP-PREAMBLE_POWER_RAMPING_STEP) (1)

- N is the power ramping counter when switching to RA with Msg3 repetition requested;

- PREAMBLE_POWER_RAMPING_STEP_MSG3REP is the power ramping step size used in PRACH transmission when Msg3 repetition is requested; and

- PREAMBLE_POWER_RAMPING_STEP is the power ramping step size used in PRACH transmission when Msg3 repetition is not requested.

The power control formula for legacy PRACH transmission mentioned above may be changed as follows:

PRACH_tx_power=preambleReceivedTargetPower+DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER-1) ×PREAMBLE_POWER_RAMPING_STEP+OFFSET (2)

- the value of DELTA_PREAMBLE is provided according to clause 7.3 of 3GPP TS 38.321, and it is used for compensating power differences caused by preamble formats;

- preambleReceivedTargetPower is the received target power for preamble transmissions not for requesting Msg3 repetition; and

- PREAMBLE_POWER_RAMPING_STEP is the power ramping step size for preamble transmissions not for requesting Msg3 repetition.

For another example, in one case, when the number of UEs supporting Msg3 repetition is less than the number of UEs not supporting Msg3 repetitions in the system, the collision of PRACH transmissions on the PRACH resources not for requesting Msg3 repetition may be more serious and UE may switch from the legacy PRACH transmission to the Msg3 repetition PRACH transmission. For yet another example, the Msg3 link quality may be quite bad due to low uplink timing alignment accuracy even if the RSRP measured on pathloss reference is good enough to select a legacy RA without requesting Msg3 repetition, which will cause frequent power ramping in PRACH reattempts when the contention resolution timer expires, then a switching from legacy PRACH transmission to Msg3 repetition PRACH transmission may be needed.

In the above two examples, legacy PRACH transmission may be switched to the Msg3 repetition PRACH transmission, and the target power level may follow the Msg3 repetition PRACH transmission power control formula plus an offset, where the offset is

OFFSET= (N-1) × (PREAMBLE_POWER_RAMPING_STEP-PREAMBLE_POWER_RAMPING_STEP_msg3Rep) (3)

- PREAMBLE_POWER_RAMPING_STEP is the power ramping step size used in PRACH transmission when Msg3 repetition is not requested

The Msg3 repetition PRACH transmission power control formula mentioned above may be given as follows:

PRACH_tx_power=preambleReceivedTargetPowerMsg3Rep+DELTA_PREAMBLE+ (PREAMBLE_POWER_RAMPING_COUNTER-1) ×PREAMBLE_POWER_RAMPING_STEP_msg3Rep+OFFSET (4)

- preambleReceivedTargetPowerMSG3REP is the received target power for preamble transmissions for requesting Msg3 repetition; and

- PREAMBLE_POWER_RAMPING_STEP_msg3Rep is the power ramping step size for preamble transmissions for requesting Msg3 repetition.

In some embodiments, for switching between the legacy PRACH and the Msg3 repetition PRACH, the power ramping counter may be reset after switching. This may be needed to save UE power via reducing the ramped power of PRACH especially when the PRACH reattempts may be triggered due to bad Msg3 performance, and power ramping of PRACH reattempt may be not necessary in such case.

In some embodiments, whether the power ramping should continue after the switching between legacy RA and msg3 repetition RA can be configured by RRC signaling. As an example, one-bit field continueRampingToMsg3 in RACH-ConfigCommon can be defined to enable continuously increasing of power ramping counter after RA switching from legacy 4-step RA or 2-step RA to msg3 repetition RA. Tf the field is absent, the power ramping counter may be reset after RA switching from legacy 4-step RA or 2-step RA to msg3 repetition RA.

In some embodiments, one or more of the following may depend on whether separate PRACH occasions are configured for RA with Msg3 repetition requested:

- whether the power ramping counter is reset after switching between RA with Msg3 repetition requested and the RA without Msg3 repetition request;

- whether preamble received target power for PRACH transmission in RA supporting Msg3 repetition is separately configured or same as legacy RA not for requesting Msg3 repetition; and

- whether the power ramping step size for PRACH transmission in RA supporting Msg3 repetition is separately configured or is the same as legacy RA not for requesting Msg3 repetition.

For example, in some embodiments, only when separate ROs are configured for RA with Msg3 repetition requested, separate power ramping step size and/or separate preamble received target power may be configured, and the power ramping counter may be reset after switching from RA with requesting Msg3 repetition to legacy RA.

For another example, in some embodiments, when shared ROs are used for legacy RA and the RA with Msg3 repetition requested, same power ramping step size and preamble received target power may be configured for both RA types and the power ramping counter may continue increasing after switching from RA with requesting Msg3 repetition to legacy RA.

In some embodiments, "legacy RA" mentioned in above embodiments could be 2-step RA and/or 4-step RA with PRACH resources not for requesting Msg3 repetition.

In some embodiments, for switching among 2-step RA, legacy 4-step RA, and 4-step RA with Msg3 repetition requested, more than one power offset may be applied when the RA includes switching among these 3 types of PRACH resources.

For example, when a UE initially selects 2-step RACH, then switches to 4-step RACH without requesting Msg3 repetition, and then switches to 4-step RA with requesting Msg3 repetition, assuming different power ramping steps are configured, MSGA_PREAMBLE_POWER_RAMPING_STEP, PREAMBLE_POWER_RAMPING_STEP, MSG3Rep_PREAMBLE_POWER_RAMPING_STEP for 2-step RACH, legacy 4-step RACH, and 4-step RACH with Msg3 repetition requested.

A first power offset POWER_OFFSET_2STEP_RA may be needed for switching from 2-step RA to legacy 4-step RA at the time when

PREAMBLE_POWER_RAMPING_COUNTER has a value of Cont1:

POWER_OFFSET_2STEP_RA= (Cont1-1) × (MSGA_PREAMBLE_POWER_RAMPING_STEP-PREAMBLE_POWER_RAMPING_STEP) (5)

Then a second power offset POWER_OFFSET_MSG3REP_RA may be needed for switching from legacy 4-step RA to 4-step RA with Msg3 repetition requested at the time when PREAMBLE_POWER_RAMPING_COUNTER has a value of Cont2:

POWER_OFFSET_MSG3REP_RA= (Cont2-Cont1+1) × (PREAMBLE_POWER_RAMPING_STEP-MSG3Rep_PREAMBLE_POWER_RAMPING_STEP) (6)

In this way, the transmission power for each attempt may be calculated, for example, in a way similar to the equations (1) to (4) described above.

In some embodiments, the term "the PRACH resource for requesting Msg3 repetition" may be replaced by one or more of the following:

- The PRACH resource for indicating a network slice;

- The PRACH resource for indicating a small data transmission;

- The PRACH resource for indicating a RedCap UE (UE with reduced capability) ;

- The PRACH resource for indicating a random access in non-terrestrial network; and

- The PRACH resource for indicating a specific service type or UE priority.

In other words, Msg3 repetition is merely an example of a feature that can be requested or not during a RA procedure mentioned above, and the present disclosure is not limited to Msg3 repetition.

In some embodiments, when multiple features (e.g. those features listed above) are requested/indicated by different PRACH preambles, multiple power ramping offsets may be needed in a way similar to the equations (5) and (6) described above.

Please note that the term "feature X RA" used herein may refer to the RA with PRACH resources selected for requesting/indicating the feature X. With this method, complexity of switching between different RA procedures for indicating different features may be reduced.

Fig. 4 is a flow chart of an exemplary method 400 at a UE for feature based power ramping for random access according to an embodiment of the present disclosure. The method 400 may be performed at a user equipment (e.g., the UE 110) . The method 400 may comprise step S410 and S420. However, the present disclosure is not limited thereto. In some other embodiments, the method 400 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 400 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 400 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 400 may be combined into a single step.

The method 400 may begin at step S410 where one or more first power parameters for physical random access channel (PRACH) transmission may be determined at least partially based on whether a first feature is to be requested or not.

At step S420, the PRACH transmission may be transmitted to the network node at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.

In some embodiments, the first PRACH resource may comprise at least one of: -a PRACH time/frequency resource; and -a PRACH preamble sequence. In some embodiments, the first feature may comprise at least one of: -Msg3 repetition; -MsgA repetition; -a network slice; -small data transmission (SDT) ; -a UE with reduced capability (RedCap UE) ; -a random access in non-terrestrial network; and -a specific service type or UE priority. In some embodiments, the one or more first power parameters may comprise at least one of: -a power ramping counter for PRACH transmission; -a power ramping step size for PRACH transmission; and -a preamble received target power for PRACH transmission. In some embodiments, each of the one or more first power parameters may be one of: -a power parameter that is commonly configured for both PRACH transmission with the first feature to be requested and PRACH transmission without the first feature to be requested; -a power parameter that is specifically configured for PRACH transmission with the first feature to be requested; and -a power parameter that is specifically configured for PRACH transmission without the first feature to be requested.

In some embodiments, the method 400 may further comprise: transmitting, to the network node, the PRACH transmission at a second power, which is determined at least partially based on the one or more first power parameters and a power ramping counter that is maintained at the UE, by using a second PRACH resource that indicates a different result of whether the first feature is requested or not than that indicated by the first PRACH resource, in response to determining that all its previous RA attempts fail. In some embodiments, the power ramping counter may be increased when starting a new attempt of the random access procedure no matter which PRACH resource is used in the new attempt. In some embodiments, the second power may be calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

In some embodiments, the preamble received target power for calculating the second power may be determined as follows:

In some embodiments, P _offset may be calculated as follows:

P _offset= (m-1) × (P _{step_1}-P _{step_2})

In some embodiments, the power ramping counter may be reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource. In some embodiments, whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource may be determined by Radio Resource Control (RRC) signaling. In some embodiments, at least one of the following conditions may be determined at least partially based on whether a PRACH occasion configured for the PRACH transmission is a shared PRACH occasion or a separate PRACH occasion: -whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -whether the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not; and -whether the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not.

In some embodiments, when the PRACH occasion configured for the PRACH transmission is a separate PRACH occasion, at least one of the following conditions may be true: -the power ramping counter is reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource; and -the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource. In some embodiments, when the PRACH occasion configured for the PRACH transmission is a shared PRACH occasion, at least one of the following conditions may be true: -the power ramping counter is kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource; -the preamble received target power for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource; and -the power ramping step size for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource.

In some embodiments, any PRACH transmission in the random access procedure that uses a PRACH resource indicating that the first feature is not requested may be a part of Type-1 and/or Type-2 random access procedure without the first feature requested. In some embodiments, before the step S410, the method 400 may further comprise: transmitting, to the network node, one or more PRACH transmissions by using a third PRACH resource until the random access procedure is successful or until switching the random access procedure from using the third PRACH resource to using the first PRACH resource. In some embodiments, the first power may be calculated at least partially based on a preamble received target power that is compensated by a first power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

In some embodiments, the preamble received target power for calculating the first power may be determined as follows:

P _n=P ₀+Δp+ (n-1) ×P _{step_1}+P _{offset_1}

In some embodiments, P _{offset_1} may be calculated as follows:

P _{offset_1}= (m-1) × (P _{step_3}-P _{step_1})

In some embodiments, the second power may be calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.

P _n=P ₀+Δp+ (n-1) ×P _{step_2}+P _{offset_1}+P _{offset_2}

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_2} is a power ramping step size used for the current PRACH transmission, and P _{offset_2} is the second power offset for compensating a power difference caused by different power ramping step sizes.

In some embodiments, P _{offset_2} may be calculated as follows:

P _{offset_2}= (k-m+1) × (P _{step_1}-P _{step_2})

where k is the value of the power ramping counter when the PRACH transmission using the first PRACH resource is switched to the PRACH transmission using the second PRACH resource.

In some embodiments, the random access procedure may comprise more than one switching between PRACH transmissions using different PRACH resources, which indicate that different combinations of one or more features are requested or not, wherein a power offset may be determined for each switching, wherein a power used for a PRACH transmission may be determined at least partially based on all the power offsets that are determined for all the switching before the PRACH transmission.

In some embodiments, the method 400 may further comprise: receiving, from the network node, a random access response (RAR) comprising an indicator indicating whether the first feature is to be used or not; and transmitting, to the network node, a Msg3 with or without the first feature enabled depending on the received indicator.

Fig. 5 is a flow chart of an exemplary method 500 at a network node for feature based power ramping for random access according to an embodiment of the present disclosure. The method 500 may be performed at a network node (e.g., the gNB 120) . The method 500 may comprise step S510. However, the present disclosure is not limited thereto. In some other embodiments, the method 500 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 500 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 500 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 500 may be combined into a single step.

The method 500 may begin at step S510 where a configuration may be transmitted to the UE, the configuration indicating at least one of: -a power ramping step size for PRACH transmission; -a preamble received target power for PRACH transmission; -whether a power ramping counter is reset or kept increasing when switching the random access procedure from using a first PRACH resource to using a second PRACH resource; and -whether a shared or a separate PRACH occasion is configured for PRACH transmission.

Fig. 6 schematically shows an embodiment of an arrangement 600 which may be used in a user equipment (e.g., the UE 110) or a network node (e.g., the gNB 120) according to an embodiment of the present disclosure. Comprised in the arrangement 600 are a processing unit 606, e.g., with a Digital Signal Processor (DSP) or a Central Processing Unit (CPU) . The processing unit 606 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 600 may also comprise an input unit 602 for receiving signals from other entities, and an output unit 604 for providing signal (s) to other entities. The input unit 602 and the output unit 604 may be arranged as an integrated entity or as separate entities.

Furthermore, the arrangement 600 may comprise at least one computer program product 608 in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and/or a hard drive. The computer program product 608 comprises a computer program 610, which comprises code/computer readable instructions, which when executed by the processing unit 606 in the arrangement 600 causes the arrangement 600 and/or the UE/network node in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 4 to Fig. 5 or any other variant.

The computer program 610 may be configured as a computer program code structured in

computer program modules

610A and 610B. Hence, in an exemplifying embodiment when the arrangement 600 is used in a UE, the code in the computer program of the arrangement 600 includes: a module 610A for determining one or more first power parameters for PRACH transmission at least partially based on whether a first feature is to be requested or not; and a module 610B for transmitting, to the network node, the PRACH transmission at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.

Further, the computer program 610 may be further configured as a computer program code structured in computer program modules 610C. Hence, in an exemplifying embodiment when the arrangement 600 is used in a network node, the code in the computer program of the arrangement 600 includes: a module 610C for transmitting, to the UE, a configuration indicating at least one of: -a power ramping step size for PRACH transmission; -a preamble received target power for PRACH transmission; -whether a power ramping counter is reset or kept increasing when switching the random access procedure from using a first PRACH resource to using a second PRACH resource; and -whether a shared or a separate PRACH occasion is configured for PRACH transmission.

The computer program modules could essentially perform the actions of the flow illustrated in Fig. 4 to Fig. 5, to emulate the UE or the network node. In other words, when the different computer program modules are executed in the processing unit 606, they may correspond to different modules in the UE or the network node.

Although the code means in the embodiments disclosed above in conjunction with Fig. 6 are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.

The processor may be a single CPU (Central processing unit) , but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the UE and/or the network node.

Correspondingly to the method 400 as described above, an exemplary user equipment is provided. Fig. 7 is a block diagram of a UE 700 according to an embodiment of the present disclosure. The UE 700 may be, e.g., the UE 110 in some embodiments.

The UE 700 may be configured to perform the method 400 as described above in connection with Fig. 4. As shown in Fig. 7, the UE 700 may comprise a determining module 710 for determining one or more first power parameters for PRACH transmission at least partially based on whether a first feature is to be requested or not; and a transmitting module 720 for transmitting, to the network node, the PRACH transmission at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.

The above modules 710 and/or 720 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 4. Further, the UE 700 may comprise one or more further modules, each of which may perform any of the steps of the method 400 described with reference to Fig. 4.

Correspondingly to the method 500 as described above, a network node is provided. Fig. 8 is a block diagram of an exemplary network node 800 according to an embodiment of the present disclosure. The network node 800 may be, e.g., the gNB 120 in some embodiments.

The network node 800 may be configured to perform the method 500 as described above in connection with Fig. 5. As shown in Fig. 8, the network node 800 may comprise a transmitting module 810 for transmitting, to the UE, a configuration indicating at least one of: -a power ramping step size for PRACH transmission; -a preamble received target power for PRACH transmission; -whether a power ramping counter is reset or kept increasing when switching the random access procedure from using a first PRACH resource to using a second PRACH resource; and -whether a shared or a separate PRACH occasion is configured for PRACH transmission.

The above modules 810 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 5. Further, the network node 800 may comprise one or more further modules, each of which may perform any of the steps of the method 500 described with reference to Fig. 5.

With reference to Fig. 9, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211, such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of

base stations

3212a, 3212b, 3212c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a

corresponding coverage area

3213a, 3213b, 3213c. Each

base station

3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first UE 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of

UEs

3291, 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The

connections

3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown) .

The communication system of Fig. 9 as a whole enables connectivity between one of the connected

UEs

3291, 3292 and the host computer 3230. The connectivity may be described as an over-the-top (OTF) connection 3250. The host computer 3230 and the connected

UEs

3291, 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211, the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Fig. 10. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311, which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Fig. 10) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Fig. 10) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides.

It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Fig. 10 may be identical to the host computer 3230, one of the

base stations

3212a, 3212b, 3212c and one of the

UEs

3291, 3292 of Fig. 9, respectively. This is to say, the inner workings of these entities may be as shown in Fig. 10 and independently, the surrounding network topology may be that of Fig. 9.

In Fig. 10, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network) .

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the latency and power consumption and thereby provide benefits such as reduced user waiting time, better responsiveness, extended battery lifetime.

A measurement procedure may be provided for the purpose of monitoring data rate, latency, and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which

software

3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc. ; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer's 3310 measurements of throughput, propagation times, latency, and the like. The measurements may be implemented in that the

software

3311, 3331 causes messages to be transmitted, in particular empty or ′dummy′ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Fig. 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 9 and Fig. 10. For simplicity of the present disclosure, only drawing references to Fig. 11 will be included in this section. In a first step 3410 of the method, the host computer provides user data. In an optional substep 3411 of the first step 3410, the host computer provides the user data by executing a host application. In a second step 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 3440, the UE executes a client application associated with the host application executed by the host computer.

Fig. 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 9 and Fig. 10. For simplicity of the present disclosure, only drawing references to Fig. 12 will be included in this section. In a first step 3510 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 3530, the UE receives the user data carried in the transmission.

Fig. 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 9 and Fig. 10. For simplicity of the present disclosure, only drawing references to Fig. 13 will be included in this section. In an optional first step 3610 of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second step 3620, the UE provides user data. In an optional substep 3621 of the second step 3620, the UE provides the user data by executing a client application. In a further optional substep 3611 of the first step 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 3630, transmission of the user data to the host computer. In a fourth step 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Fig. 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 9 and Fig. 10. For simplicity of the present disclosure, only drawing references to Fig. 14 will be included in this section. In an optional first step 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 3720, the base station initiates transmission of the received user data to the host computer. In a third step 3730, the host computer receives the user data carried in the transmission initiated by the base station.

The present disclosure is described above with reference to the embodiments thereof. However, those embodiments are provided just for illustrative purpose, rather than limiting the present disclosure. The scope of the disclosure is defined by the attached claims as well as equivalents thereof. Those skilled in the art can make various alternations and modifications without departing from the scope of the disclosure, which all fall into the scope of the disclosure.

Abbreviation Explanation

BFR Beam Failure Recovery

SSB Synchronization Signal Block

PRACH Physical Random Access Channel

RACH Random Access Channel

RO PRACH occasion, i.e., the timing frequency resource used for on PRACH transmission

RSRP Reference Signal Received Power

TA Timing Advance

Claims

A method (400) at a user equipment (UE) (110) for performing a random access (RA) procedure with a network node (120) , the method (400) comprising:

determining (S410) one or more first power parameters for physical random access channel (PRACH) transmission at least partially based on whether a first feature is to be requested or not;

transmitting (S420) , to the network node (120) , the PRACH transmission at a first power, which is determined at least partially based on the one or more first power parameters, by using a first PRACH resource that indicates whether the first feature is requested or not.
The method (400) of claim 1, wherein the first PRACH resource comprises at least one of:

- a PRACH time/frequency resource; and

- a PRACH preamble sequence.
The method (400) of claim 1 or 2, wherein the first feature comprises at least one of:

- Msg3 repetition;

- MsgA repetition;

- a network slice;

- small data transmission (SDT) ;

- a UE with reduced capability (RedCap UE) ;

- a random access in non-terrestrial network; and

- a specific service type or UE priority.
The method (400) of any of claims 1 to 3, wherein the one or more first power parameters comprise at least one of:

- a power ramping counter for PRACH transmission;

- a power ramping step size for PRACH transmission; and

- a preamble received target power for PRACH transmission.
The method (400) of any of claims 1 to 4, wherein each of the one or more first power parameters is one of:

- a power parameter that is commonly configured for both PRACH transmission with the first feature to be requested and PRACH transmission without the first feature to be requested;

- a power parameter that is specifically configured for PRACH transmission with the first feature to be requested; and

- a power parameter that is specifically configured for PRACH transmission without the first feature to be requested.
The method (400) of any of claims 1 to 5, further comprising:

transmitting, to the network node (120) , the PRACH transmission at a second power, which is determined at least partially based on the one or more first power parameters and a power ramping counter that is maintained at the UE (110) , by using a second PRACH resource that indicates a different result of whether the first feature is requested or not than that indicated by the first PRACH resource, in response to determining that all its previous RA attempts fail.
The method (400) of claim 6, wherein the power ramping counter is increased when starting a new attempt of the random access procedure no matter which PRACH resource is used in the new attempt.
The method (400) of claim 7, wherein the second power is calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.
The method (400) of claim 8, wherein the preamble received target power for calculating the second power is determined as follows:

P _n = P ₀ + Δp + (n -1) × P _{step_2} + P _offset

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_2} is a power ramping step size used for the current PRACH transmission, and P _offset is the second power offset for compensating a power difference caused by different power ramping step sizes.
The method (400) of claim 9, wherein P _offset is calculated as follows:

P _offset = (m-1) × (P _{step_1} -P _{step_2})

where m is the value of the power ramping counter when the PRACH transmission using the first PRACH resource is switched to the PRACH transmission using the second PRACH resource, and P _{step_1} is a power ramping step size used by the PRACH transmissions using the first PRACH resource.
The method (400) of claim 6, wherein the power ramping counter is reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource.
The method (400) of claim 6, wherein whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource is determined by Radio Resource Control (RRC) signaling.
The method (400) of claim 6, wherein at least one of the following conditions is determined at least partially based on whether a PRACH occasion configured for the PRACH transmission is a shared PRACH occasion or a separate PRACH occasion:

- whether the power ramping counter is reset or kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource;

- whether the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not; and

- whether the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource or not.
The method (400) of claim 13, wherein when the PRACH occasion configured for the PRACH transmission is a separate PRACH occasion, at least one of the following conditions is true:

- the power ramping counter is reset when switching the random access procedure from using the first PRACH resource to using the second PRACH resource;

- the preamble received target power for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource; and

- the power ramping step size for the PRACH transmission using the first PRACH resource is separately configured from that for the PRACH transmission using the second PRACH resource.
The method (400) of claim 13, wherein when the PRACH occasion configured for the PRACH transmission is a shared PRACH occasion, at least one of the following conditions is true:

- the power ramping counter is kept increasing when switching the random access procedure from using the first PRACH resource to using the second PRACH resource;

- the preamble received target power for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource; and

- the power ramping step size for the PRACH transmission using the first PRACH resource is not separately configured from that for the PRACH transmission using the second PRACH resource.
The method (400) of any of claims 1 to 15, wherein any PRACH transmission in the random access procedure that uses a PRACH resource indicating that the first feature is not requested is a part of Type-1 and/or Type-2 random access procedure without the first feature requested.
The method (400) of claim 7 or 8, where before the step of transmitting, to the network node (120) , the PRACH transmission at a first power, the method further comprises:

transmitting, to the network node (120) , one or more PRACH transmissions by using a third PRACH resource until the random access procedure is successful or until switching the random access procedure from using the third PRACH resource to using the first PRACH resource.
The method (400) of claim 17, wherein the first power is calculated at least partially based on a preamble received target power that is compensated by a first power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.
The method (400) of claim 18, wherein the preamble received target power for calculating the first power is determined as follows:

P _n = P ₀ + Δp + (n -1) × P _{step_1} + P _{offset_1}

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_1} is a power ramping step size used for the current PRACH transmission, and P _{offset_1} is the first power offset for compensating a power difference caused by different power ramping step sizes.
The method (400) of claim 19, wherein P _{offset_1} is calculated as follows:

P _{offset_1} = (m -1) × (P _{step_3} -P _{step_1})

where m is the value of the power ramping counter when the PRACH transmission using the third PRACH resource is switched to the PRACH transmission using the first PRACH resource, and P _{step_3} is a power ramping step size used by the PRACH transmissions using the third PRACH resource.
The method (400) of claim 20, wherein the second power is calculated at least partially based on a preamble received target power that is compensated by a second power offset for different power ramping step sizes used by the previous PRACH transmissions and the current PRACH transmission.
The method (400) of claim 21, wherein the preamble received target power for calculating the second power is determined as follows:

P _n = P ₀ +Δp + (n -1) × P _{step_2} + P _{offset_1} + P _{offset_2}

where P _n is the preamble received target power to be calculated, n is the value of the power ramping counter, P ₀ is an initial preamble received target power, Δp is a power offset for compensating a power difference caused by different preamble formats, P _{step_2} is a power ramping step size used for the current PRACH transmission, and P _{offset_2} is the second power offset for compensating a power difference caused by different power ramping step sizes.
The method (400) of claim 22, wherein P _{offset_2} is calculated as follows:

P _{offset_2} = (k -m + 1) × (P _{step_1} -P _{step_2})

where k is the value of the power ramping counter when the PRACH transmission using the first PRACH resource is switched to the PRACH transmission using the second PRACH resource.
The method (400) of any of claims 1 to 23, wherein the random access procedure comprises more than one switching between PRACH transmissions using different PRACH resources, which indicate that different combinations of one or more features are requested or not,

wherein a power offset is determined for each switching,

wherein a power used for a PRACH transmission is determined at least partially based on all the power offsets that are determined for all the switching before the PRACH transmission.
The method (400) of any of claims 1 to 24, further comprising:

receiving, from the network node (120) , a random access response (RAR) comprising an indicator indicating whether the first feature is to be used or not; and

transmitting, to the network node (120) , a Msg3 with or without the first feature enabled depending on the received indicator.
A user equipment (110, 600, 700) , comprising:

a processor (606) ;

a memory (608) storing instructions which, when executed by the processor (606) , cause the processor (606) to perform the method (400) of any of claims 1 to 25.
A method (500) at network node (120) for performing a random access procedure with a user equipment (UE) , the method comprising:

transmitting, to the UE (110) , a configuration indicating at least one of:

- a power ramping step size for PRACH transmission;

- a preamble received target power for PRACH transmission;

- whether a power ramping counter is reset or kept increasing when switching the random access procedure from using a first PRACH resource to using a second PRACH resource; and

- whether a shared or a separate PRACH occasion is configured for PRACH transmission.
A network node (120, 600, 800) , comprising:

a processor (606) ;

a memory (608) storing instructions which, when executed by the processor (606) , cause the processor (606) to perform the method (500) of claim 27.
A computer program (610) comprising instructions which, when executed by at least one processor (606) , cause the at least one processor (606) to carry out the method (400, 500) of any of claims 1 to 25 and 27.
A carrier (608) containing the computer program (610) of claim 29, wherein the carrier (608) is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.
A telecommunications system (3210) comprising:

one or more UEs (110, 3291, 3292) of claim 26; and

at least one network node (120, 3212) of claim 28.