WO2020221861A1

WO2020221861A1 - Enhanced initial access for efficient small data transmission

Info

Publication number: WO2020221861A1
Application number: PCT/EP2020/062033
Authority: WO
Inventors: Daniela Laselva; Claudio Rosa; Nuno Manuel KIILERICH PRATAS; Renato Barbosa ABREU; Marco CENTENARO
Original assignee: Nokia Technologies Oy
Priority date: 2019-05-02
Filing date: 2020-04-30
Publication date: 2020-11-05

Abstract

A method including determining a size of data in a buffer of a user equipment; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

Description

ENHANCED INI TIAL ACCESS FOR EFFICIENT SMALL DATA

TRANSMISSION

BACKGROUND

Technical Field

[0001] The example and non-limiting embodiments relate generally to communications and, more particularly, to a user equipment in a radio resource control inactive state.

Brief Description of Prior Developments

[0002] A radio resource control inactive state (RRC_INACTIVE ) is known for use in a user equipment for a reduced control signaling required for requesting and obtaining the resume of a suspended RRC connection to a radio resource control connected state (RRC_CONNECTED) versus a radio resource control idle state (RRC_IDLE) .

SUMMARY

[0003] The following summary is merely intended to be exemplary. The summary is not intended to limit the scope of the claims. [0004] In accordance with one aspect, an example method is provided comprising: determining a size of data in a buffer of a user equipment; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

[0005] In accordance with another aspect, an example embodiment is provided in an apparatus comprising at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: determine a size of data in a buffer of the apparatus; select, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmit a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

[0006] In accordance with another aspect, an example embodiment is provided with a non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: determining a size of data in a buffer of a user equipment; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

[0007] In accordance with another aspect, an example apparatus is provided comprising: means for determining a size of data in a buffer of the apparatus; means for selecting, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and means for transmitting a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

[0008] In accordance with another aspect, an example method is provided comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message .

[0009] In accordance with another aspect, an example apparatus is provided comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: receive a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determine a random access mode selected by the user equipment based upon the message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[ 0010 ] In accordance with another aspect, an example is provided with a non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message .

[ 0011 ] In accordance with another aspect, an example apparatus is provided comprising: means for receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; means for determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing aspects and other features are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0013] Fig. 1 is a diagram illustrating one example of a system comprises features as described herein;

[0014] Fig. 2A is a diagram illustrating a 4-Step contention-based random access procedure;

[0015] Fig. 2B is a diagram illustrating a 2-Step RACH procedure ;

[0016] Fig. 3 is a diagram illustrating a NR RRC state machine with RRC state transitions;

[0017] Fig. 4 is a diagram illustrating an uplink small data transmission (SDT) ;

[0018] Fig. 5 is a diagram illustrating an uplink small data transmission (SDT) in RRC inactive with 2-Step RACH;;

[0019] Fig. 6 is a diagram illustrating features as described herein; and

[0020] Fig. 7 is a diagram illustrating features as described herein.

DETAILED DESCRIPTION OF EMBODIMENT

[0021] The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

3GPP third generation partnership project 5G fifth generation

5GC 5G core network

ACK Acknowledgement

AMF access and mobility management function

AS Access Stratum

BLER Block error rate

BSR Buffer status report

C-RNTI Cell RNTI

CSI Channel state information

CU central unit

DL Downlink

DMRS Demodulation reference signal

DU distributed unit

EDT Early data transmission

efeMTC even further enhanced MTC

eMTC enhanced MTC

eNB (or eNodeB) evolved Node B (e.g., an LTE base station)

EN-DC E-UTRA-NR dual connectivity

en-gNB or En-gNB node providing NR user plane and control plane protocol terminations towards the UE, and acting as secondary node in

EN-DC

eRA enhanced Random Access

E-UTRA evolved universal terrestrial radio access, i.e., the LTE radio access technology

gNB (or gNodeB) base station for 5G/NR, i.e., a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC

I/F interface

IIoT Industrial IoT

IoT Internet of Things

I-RNTI Inactive RNTI

LCH Logical channel LTE long term evolution

MAC medium access control

MCS Modulation and coding scheme

MME mobility management entity mMTC Massive MTC

MTC Machine type communications ng or NG new generation

ng-eNB or NG-eNB new generation eNB

NR new radio

N/W or NW network

PDCCH Physical DL Control Channel

PDCP packet data convergence protocol

PDU Protocol data unit

PHY physical layer

PRACH Physical RACH

PRB Physical RB

PUSCH Physical UL Shared Channel

RA Random Access

RACH Random Access Channel

RB Resource Block

RAN radio access network

Rel release

RLC radio link control

RNTI Radio Network Temporary Identifier

RRC Radio Resource Control

RRH remote radio head

RRC radio resource control

RU radio unit

Rx receiver

SIB System Information Block

SDAP service data adaptation protocol

SDT Small data transmission SGW serving gateway

SMF session management function

TBS Transport block size

TC-RNTI Temporary C-RNTI

TS technical specification

Tx transmitter

UCI Uplink control information

UE user equipment (e.g., a wireless, typically mobile device)

UL Uplink

UP User plane

UPF user plane function

[ 0022 ] Turning to FIG. 1, this figure shows a block diagram of one possible and non-limiting example in which the examples may be practiced. A user equipment (UE) 110, radio access network (RAN) node 170, and network element (s) 190 are illustrated. In the example of FIG. 1, the user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140, comprising one of or both parts 140-1 and/or 140-2, which may be implemented in a number of ways. The module 140 may be implemented in hardware as module 140-1, such as being implemented as part of the one or more processors 120. The module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with RAN node 170 via a wireless link 111.

[ 0023 ] The RAN node 170 in this example is a base station that provides access by wireless devices such as the UE 110 to the wireless network 100. The RAN node 170 may be, for example, a base station for 5G, also called New Radio (NR) . In 5G, the RAN node 170 may be a NG-RAN node, which is defined as either a gNB or a ng-eNB. A gNB is a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to a 5GC (such as, for example, the network element (s) 190) . The ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC. The NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DUs) (gNB-DUs), of which DU 195 is shown. Note that the DU may include or be coupled to and control a radio unit (RU) . The gNB-CU is a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs . The gNB-CU terminates the FI interface connected with the gNB-DU. The FI interface is illustrated as reference 198, although reference 198 also illustrates a link between remote elements of the RAN node 170 and centralized elements of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB- CU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the FI interface 198 connected with the gNB-CU. Note that the DU 195 is considered to include the transceiver 160, e.g., as part of a RU, but some examples of this may have the transceiver 160 as part of a separate RU, e.g., under control of and connected to the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station, for LTE (long term evolution), or any other suitable base station or node.

[ 0024 ] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor (s) 152, memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memory/memories and processor ( s ) , and/or other hardware, but these are not shown. [0025] The RAN node 170 includes a module 150, comprising one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways. The module 150 may be implemented in hardware as module 150-1, such as being implemented as part of the one or more processors 152. The module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the RAN node 170 to perform one or more of the operations as described herein. Note that the functionality of the module 150 may be distributed, such as being distributed between the DU 195 and the CU 196, or be implemented solely in the DU 195.

[0026] The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 may communicate using, e.g., link 176. The link 176 may be wired or wireless or both and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0027] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 for gNB implementation for 5G, with the other elements of the RAN node 170 possibly being physically in a different location from the RRH/DU, and the one or more buses 157 could be implemented in part as, for example, fiber optic cable or other suitable network connection to connect the other elements (e.g., a central unit (CU) , gNB-CU) of the RAN node 170 to the RRH/DU 195. Reference 198 also indicates those suitable network link ( s ) .

[ 0028 ] It is noted that description herein indicates that "cells" perform functions, but it should be clear that equipment which forms the cell will perform the functions. The cell makes up part of a base station. That is, there can be multiple cells per base station. For example, there could be three cells for a single carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single base station' s coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and a base station may use multiple carriers. So, if there are three 120 degree cells per carrier and two carriers, then the base station has a total of 6 cells.

[ 0029 ] The wireless network 100 may include a network element or elements 190 that may include core network functionality, and which provides connectivity via a link or links 181 with a further network, such as a telephone network and/or a data communications network (e.g., the Internet) . Such core network functionality for 5G may include access and mobility management function(s) (AMF(S)) and/or user plane functions (UPF(s)) and/or session management function(s) (SMF(s)) . Such core network functionality for LTE may include MME (Mobility Management Entity) /SGW (Serving Gateway) functionality. These are merely exemplary functions that may be supported by the network element (s) 190, and note that both 5G and LTE functions might be supported. The RAN node 170 is coupled via a link 131 to a network element 190. The link 131 may be implemented as, e.g., an NG interface for 5G, or an SI interface for LTE, or other suitable interface for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the network element 190 to perform one or more operations.

[ 0030 ] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects. [ 0031 ] The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processors 120, 152, and 175 may be means for performing functions, such as controlling the UE 110, RAN node 170, and other functions as described herein.

[ 0032 ] In general, the various embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, tablets, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions. [0033] Features as described herein may be used to provide a new dedicated Uplink Control Information (UCI) format for UEs in RRC Inactive to carry control information as part of the PUSCH associated to a random access preamble, which is sent as part of MsgA in 2-step RACH. Such format is denoted to herein as "RRC Inactive UCI-Scheduling Assisting Information (SAI) format" or simply "UCI-SAI format". This may be used, for example, for enhancement of the initial access procedure of 5G NR systems for UEs in the RRC Inactive state.

[0034] In RAN#82 a new Rel-16 work item on "2-step RACH for NR" was agreed in RP-182894. The 4-step RACH procedure is supported in NR Rel-15. Fig. 2A shows the basic procedure for 4-step contention-based random access and Fig. 2B shows the 2-step RACH procedure. In 2-step RACH, MsgA combines the preamble signal (Msgl) and the data signal (Msg3), and MsgB combines the random access response (Msg2) and the contention resolution (Msg4) .

[0035] A new independent RRC state, referred to as RRC_INACTIVE , was introduced in 3GPP NR Rel-15 complementing the existing states, RRC_CONNECTED and RRC_IDLE, with the goal of lean signaling and energy- efficient support of NR services. Rel-15 RRC Inactive in NR (TS 38.300/4) allows faster transition to RRC CONNECTED (~10ms CP delay) . It requires a transition to RRC_CONNECTED for data transmission. Although, the design was conceived particularly for mMTC/MIoT services [see TR 22.824], it could be beneficial to efficiently deliver small/infrequent traffic of eMBB and URLLC services as well. The NR RRC state machinery is illustrated in Fig. 3. The RRC_INACTIVE state enables to more quickly resume the connection and start the transmission of small or sporadic data with a much lower initial access delay and associated signaling overhead as compared to the RRC_IDLE state. This is achieved mainly thanks to reduced control signaling required for requesting and obtaining the resume of a suspended RRC connection, which results in UE power saving. At the same time, a UE in RRC_INACTIVE is able to achieve similar power savings as in RRC_IDLE, benefiting from e.g. a much larger period of PDCCH monitoring (e.g. paging) and relaxed measurements compared to RRC_CONNECTED . Furthermore, compared to keeping the UE in RRC_CONNECTED, the new state minimizes mobility signaling both to RAN (e.g. RRC measurement reporting, HO messages) and to the core network (e.g. to/from the AMF) . When a UE is moved to RRC_INACTIVE via a RRC Connection Suspend message, the UE Access Stratum (AS) context (referred to as UE Inactive AS Context) , necessary for the quick start of the connection, is maintained both at the UE side and RAN side, and it is identified by the UE identifier, i.e. Inactive- RNTI (I-RNTI) .

[ 0036 ] Rel-14 TR 38.304 describes Small Data Transmission (SDT) in RRC Inactive with 4 step RACH. Data is sent in Msg3 (together with RRC Resume Request) and is ciphered as per security keys in the stored UE AS context. Noteworthy, in Rel-15, UL small data transmission (SDT) in RRC Inactive is not supported. Thus, a UE in RRC Inactive requires always a transition to RRC Connected before any data transfer. However, such support is expected to be introduced in Rel-17. This could be realized as described in TR 38.804 (see Fig. 4), which assumes 4-step RACH. [ 0037 ] Rel-15 LTE supports Early Data Transmission (EDT) during 4-step RACH (up to 1000 bits in Msg3 of random access using a special EDT PRACH preamble) ; limited to uplink eMTC/efeMTC scenarios. UL data transmissions in Msg3 of 4-step RACH reduces the connection setup signaling overhead and shortens the overall transmission time. Indeed, if the entire data transmission is completed in Msg3, the network can thereafter move the UE to RRC_IDLE. To enable EDT, a UE needs to indicate to the eNB that it desires to have data transmission in Msg3. Otherwise, the eNB would have no knowledge if the UE intends to send only one packet in UL, or if the initiated RA and RRC Connection Establishment aims to set up a multi-packet connection. For EDT, the UE indicates its wish to use EDT to the network in Msgl by selecting a special PRACH preamble that has been dedicated to EDT by the eNB in system information. Also, the network broadcasts the maximum transport block size (TBS) that can be used for Msg3 in EDT (see 3GPP TS 36.321) .

[ 0038 ] Introducing uplink small data transmission (SDT) for UEs in the RRC Inactive state together with 2-step RACH appears straightforward. This is illustrated in Fig. 5. It is noted that the resume ID in Fig. 5 is the I-RNTI which is assigned to a UE in RRC Inactive state. However, the payload size that can be accommodated in the PUSCH allocation carried as part of MsgA (i.e. "Payload" in Fig. 5) is expected to be rather limited, and could be smaller than 1000 bits (maximum TBS which can be carried in Msg3 for LTE EDT) . The LTE EDT feature allows for carrying a payload of up to 1000 bits based on the eMTC scenarios and applications envisioned, such as by SA2 to benefit from such feature for example. This implies that SDT in RRC Inactive with 2-step RACH (i.e. "SDT+2-step RACH") may have reduced applicability since in many scenarios the user plane uplink payload will not fit in MsgA.

[0039] Whenever the data in the UE buffer exceeds the payload size available in MsgA, the fallback to either 2- step (or 4-step RACH) without SDT may be employed by the UE . This, however, results in larger delay as the network is unaware of UE buffer and channel state when providing the uplink grant to the UE as part of Msg2. There have been proposals for UE in RRC Inactive to provide the slice identifier information as part of the resume request.

[0040] The content of MsgA is still open. However, there are proposals to provide UCI as part of it, see following extract from Rl-1902136: o “Unique ID in order to allow for contention resolution in MsgB. The ID might be different for the different 2 -step RACH use cases [2] For example, for state transition and/or data transmission in RRC IDLE/INACTIVE states, the ID can be the UE transmitted RRC message (or part of it) which is regarded as“UE Contention Resolution Identity” in MAC, which is 48 bits long. For data transmission in the RRC CONNECTED state, the ID can be the C-RNTI MAC CE, which is 16 bits long + MAC subheader; o RRC connection/resume request (which includes the Unique ID above); o BSR/PHR; o Data payload. According to WID: “UP data transmission in RRC CONNECTED mode as in Rel-15 NR is supported” .

[0041] The presence and the size of each field depends on the use case as well as on the available size of the PUSCH carrying MsgA. Hence, the total size of MsgA could vary depending of the use case and available resources. For instance, the required minimum MsgA size could differ for RRC CONNECTED UE compared to RRC IDLE/ INACTIVE UE . "

[ 0042 ] Uplink Control Information (UCI) in LTE/NR is carried by PUCCH or PUSCH and carries mainly the following information elements: SR (Scheduling Request), HARQ ACK/NACK, and CQI . The UE transmits a certain combination of these information elements depending on the situation. When UE transmits the user data, it has to use PUSCH to send UCI. Likewise, when there is no user data to be transmitted, PUCCH is transmitted carrying UCI in it. This is as per 3GPP TS 38.213 or 3GPP TS 36.213 section 10.1.

[ 0043 ] Fig. 6 shows a diagram that illustrates an example signaling between the UE and the base RAN node. As illustrated by 602, initially the UE is in RRC Inactive state with stored UE AS Inactive context, including Resume ID (such as I-RNTI for example) . As illustrated by 604, at step 1, data appears in the UE buffer with size S. The UE determines use of eRA based on the size S, for example based upon TBS_MsgA<S<TBS_Msg3' · Enhanced Random Access (eRA) may comprises features such as disclosed in U.S. patent publication Nos. 2019/0116610, 2017/0279584, 2010/0296464 and 2006/0248437 for example which are hereby incorporated by reference in their entireties. As illustrated by 606, at step 2 the UE 110 may transmit MsgA to the RAN Node 170 (gNB in this example), where MsgA comprises: Preamble & Data (Resume ID, BSR, CSI*) . CSI* represents an extra field that allows the UE to report its observed CSI (i.e. the Channel State Information) . As illustrated by 608, at step 3 the Network may decode the Preamble & Data, and may schedule TBS/MCS based on received the BSR/CSI* & DMRS (sent with the Data) . As illustrated by 610, at step 4 the gNB 170 may transmit MsgB comprising: RA Response & Resume ID, UL Grant_Bs_R- As illustrated by 612, at step 5 the UE 110 may prepare the transport block size (TBS) accordingly. As illustrated by 614, at step 6 the UE 110 may transmit MsgAl comprising: UP UL data (carrying S bytes) & the Resume ID. As illustrated by 616, at step 7 the Network may the decode the received UP UL data correctly. As illustrated by 618, at step 8 the gNB 170 may transmit MsgB2 comprising: RRC Connection Suspend.

[ 0044 ] Features as described herein may be used in a method to provide a dedicated Uplink Control Information (UCI) format for a User Equipment (UE) in a Radio Resource Control (RRC) inactive state to carry Random Access (RA) Preamble associated control information as part of the Physical Uplink Shared Channel (PUSCH) in MsgA in a 2-Step RA. The control information carried in it may be configured to convey the scheduling assisting information to the network for User Plane (UP) data transmission. The transmission of the control information and the UP data in MsgA may be done on the basis of specific rules, and on the basis of which PUSCH resources are assigned. The UCI-SAI format may be based on the network configured thresholds (such as maxTBSMsgA and maxTBSMsg3 for example) . When new data arrives in the buffer of the UE, while the UE is in the RRC Inactive state, the UE may select the required RA procedure (such as 4-Step or 2-Step RACH, 2-Step Small Data Transmission (SDT) or 2-Step SDT based UCI-SAI PUSCH) along with corresponding PUSCH format/resources by comparing the buffer size S of the UE to the network-provided thresholds (such as maxTBSMsgA and maxTBSMsg3 for example) . If buffer size S is less than a first predetermined threshold (maxTBSMsgA for example) , then a default RRC Inactive UP PUSCH format may be selected. If the first predetermined threshold (maxTBSMsgA for example) is less than S and S is less than a second predetermined threshold (maxTBSMsg3 for example) , then UCI-SAI with or without data may be selected. In all other situations, 4-Step or 2-step Preamble only format may be used. These data-size-based thresholds may be signaled by the network to the UE via SIB or using RRC signaling for example. The UE may then accordingly create the UCI-SAI format as a new MAC Control PDU format (including information elements to carry at least the Buffer Status Report (BSR) and Channel State Information (CSI)), and may then send it as part of MsgA using an intended preamble. The network may detect the RA mode on the basis of selected preamble or the absence of UCI-SAI format. Further, 5G Node B (network) can also be configured to determine the need for additional grants based on the presence or the absence of the BSR. The network may then transmit MsgB or Msg2; including the UL grant in addition to the RA response.

[ 0045 ] Features as described herein introduce a new dedicated Uplink Control Information (UCI) format for UEs in RRC Inactive to carry control information as part of the PUSCH associated to a random access preamble, which is sent as part of MsgA in 2-step RACH. Such format is denoted to herein as "RRC Inactive UCI-Scheduling Assisting Information (SAI) format" or simply "UCI-SAI format". The information carried as part of this format is intended for a UE, in RRC Inactive state, to convey scheduling assisting information to the network with the aim to enable a more efficient subsequent scheduling of the user plane (UP) data; resulting in an overall UP latency reduction and more spectral efficient transmissions. This format may be realized, for instance, as a new UCI PUSCH format or a new MAC Control PDU format. Specific rules could determine whether it may be transmitted together with UP data in MsgA or not. The corresponding PUSCH resources to be used by RRC Inactive UEs in MsgA (e.g. in terms of amount of physical Resource Blocks, RBs, and MCS) may then be assigned accordingly; accounting for whether UCI-SAI-only or UCI-SAI+UP data is to be transmitted for example.

[ 0046 ] The use of such "UCI-SAI format" may be based on at least two network configured thresholds:

• maxTBS_MsgA, i.e. the maximum UP TBS that can be carried in MsgA of 2- step RACH using SDT, and

• maxTBS_Msgr, i.e. the maximum UP TBS for which the UE should use this new format rather than initiating a 2-step or 4-step RACH (without SDT).

[ 0047 ] Also, the scheduling assisting information may comprise :

• An indication of the buffer size, such as a Buffer Status Report (BSR), e.g. to indicate the amount of data remaining in the UE buffer after the transmission of MsgA, and

• Channel State Information (CSI) such as, for example, an average wideband SINR/RSRP/RSRQ/CQI level. This information may have the form of an index to a pre-configured table to reduce the signaling overhead. CSI is particularly useful in a TDD setting.

[ 0048 ] With features as described herein, a new UCI PUSCH format may be provided for MsgA including at least the BSR, and potentially the BSR+CSI to guide the assignment of a subsequent grant. With features as described herein, a new UE behavior may be provided to select among the following enhanced Random Access (eRA) modes based on multiple network-controlled thresholds: o RA mode 1 : 4-step RACH; o RA mode 2: 2-step RACH with fallback to 4-step without SDT ; o RA mode 3: 2-step SDT; o RA mode 4: 2-step SDT with consequent grant(s) based on the UCI-SAI PUSCH transmitted in MsgA including:

^■ 2-step MsgA only containing new UCI PUSCH (no data), or

^■ 2-step MsgA containing new UCI PUSCH + data.

[ 0049 ] With features as described herein, a new RAN node or network operation may be provided to determine the eRA mode selected by the UE and the action to take: o In one example implementation, a gNB may determine the eRA mode (and thus, whether the UE needs an additional grant) based on the selected RA resources (e.g. selected RO/preamble, where at least one set of RA resources are configured per RA mode); o In another example implementation, a gNB may determine the eRA mode (and thus, whether the UE needs an additional grant) on the presence or absence of the new UCI-SAI format in MsgA (at least to distinguish between RA mode 1 and 3, assuming they use the same pool of RA resources). o After the first additional grant is provided, the gNB may be configured to determine the need for additional grants based on the presence or the absence of the BSR in each of the scheduled transmissions.

[ 0050 ] With reference to Fig. 6, steps may include the following : 1. UE selection of the proposed“RRC Inactive UCI-S AI format” and corresponding PUSCH format/resources

2. Creation of MsgA with“UCI-S AI format” at the UE 3 a. Detection of the random access mode

3b. Network allocation of tailored UL grant to the UE

4. Network transmission of MsgB’/Msg2’ including the UL grant in addition to e.g. the RA response.

5. The UE prepares the UL TBS and physical uplink transmission.

6. The UE sends the transmission, without B SR to indicate“no need for further UL transmission”. The UE may empty/flush its buffer.

7. The network may then decode the data.

8. The network may then send an RRC Connection Suspend message to the UE to instruct it to continue being in RRC Inactive. The message acts also as an indirect ACK for the data.

Additionally, the gNB may determine the need for additional grants based on the presence/absence of BSR in each of the scheduled transmissions.

[ 0051 ] Features as described herein allow a faster and more efficient delivery of small data for UEs in the RRC Inactive state, whose payload will not fit in a regular MsgA of 2-step RACH. This results in lower latency, reduced power consumption for the UE, and reduced signaling for the network .

[ 0052 ] While Fig. 6 illustrates the signaling and steps between the UE and the RAN Node, Fig. 7 shows the corresponding flow chart from the UE perspective. With particular reference to the left side of Fig. 7, where the boxes numbered 1, 2, 4-6 and 8 correspond to the same numbered steps in Fig. 6, the UE selection of the proposed "RRC Inactive UCI-SAI format" and corresponding PUSCH format/resources may comprise, when new data arrives in the buffer of the UE in the RRC Inactive state as illustrated by 700, the UE selects the RA procedure and the associated PUSCH format/resources by comparing its buffer size S to the network-provided thresholds maxTBSMsgA and maxTBSMsg3' as follows:

As illustrated by 704, if max T BSMsgA S<max T BSMsg3’ then

UE selects to transmit in PUSCH of MsgA with the proposed“UCI- SAI format” via either:

• 2-step MsgA containing only new UCI-SAI PUSCH (no data)

• 2-step MsgA containing new UCI-SAI PUSCH + data

Else, as illustrated by 702, if S<maxTBSMsgA then

UE selects to transmit in PUSCH of MsgA with the default“(RRC Inactive) UP PUSCH format;”

Else, as illustrated by 706, if S>maxTBSMsg3’ then

UE uses 4-step RACH and sends PRACH preamble only.

Alternatively, the UE could use 2-step procedure with no SDT support in MsgA.

End

[ 0053 ] The data-size-based thresholds can be signaled by the network to the UE via SIB or using RRC signaling (before or along with the RRC Connection Suspend message) . In the latter case, the configuration provided using RRC signaling overrides the one signaled in SIB (in case they are different) .

[ 0054 ] A further remark is that the UE may compute S as it would do when calculating a legacy BSR, or it may restrict S to comprise only one or more Logical Channel (LCHs) intended for MsgA. Both modes could be permitted and one of them used according to a network indication, or either mode could be specified in the specifications.

[0055] In one type of alternate example, the transmission of the UCI-SAI may be provided in Msg3 of the 4-step procedure. This may be with data or without data for example .

[0056] In one type of example, the gNB may determine the RA mode selected by the UE based on the random access resources used for the transmission of Msgl or the preamble part of MsgA, and/or by the presence (or absence) of UCI- SAI in Msg3 or MsgA.

[0057] An example method may be provide comprising: determining a size of data in a buffer of a user equipment; selecting a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer; and transmitting a message from the user equipment to a node based, at least partially, upon the selected random access mode .

[0058] The selecting of the random access mode may be based upon at least two network configured thresholds. The selecting of the random access mode may be based upon comparing the size of the data in the buffer to the at least two network configured thresholds. The selecting may comprise: selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold. The selecting may comprise: selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds. The selected random access mode may comprise a RRC inactive uplink control information scheduling assisting information format. The selected random access mode may comprise at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) . One of the RA modes may consist of transmitting assisting information and possibly UP data in the data part of MsgA of 2-step procedure. The other RA modes (2-step RACH with transmission of UP data in data part of MsgA, and 2/4-step RACH with UP data transmission after MsgB/Msg4) are also ok to be captured.

[ 0059 ] An example embodiment may be provide with an apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: determine a size of data in a buffer of the apparatus; select a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer; and transmit a message from the apparatus to a node based, at least partially, upon the selected random access mode .

[ 0060 ] The apparatus may be configured to select the random access mode based upon at least two network configured thresholds. The apparatus may be configured to select the random access mode based upon comparing the size of the data in the buffer to the at least two network configured thresholds. The apparatus may be configured to: select a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; select a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold. The apparatus may be configured to: select a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds. The selected random access mode may comprise a RRC inactive uplink control information scheduling assisting information format. The apparatus may be configured such that the selected random access mode comprises at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

[0061] An example embodiment may be provide with a non- transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: determining a size of data in a buffer of a user equipment; selecting a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer; and transmitting a message from the user equipment to a node based, at least partially, upon the selected random access mode. The selecting of the random access mode may be based upon at least two network configured thresholds. The selecting of the random access mode may be based upon comparing the size of the data in the buffer to the at least two network configured thresholds. The selecting may comprise: selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold. The selecting may comprise: selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds. The selected random access mode may comprise a RRC inactive uplink control information scheduling assisting information format. The selected random access mode may comprise at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

[ 0062 ] An example embodiment may be provided with an apparatus comprising: means for determining a size of data in a buffer of the apparatus; means for selecting a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer; and means for transmitting a message from the apparatus to a node based, at least partially, upon the selected random access mode. [ 0063 ] The means for selecting of the random access mode may be based upon at least two network configured thresholds. The means for selecting of the random access mode may be based upon comparing the size of the data in the buffer to the at least two network configured thresholds. The means for selecting of the random access mode may comprise: means for selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; means for selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold. The means for selecting may comprise: means for selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds. The selected random access mode may comprise a RRC inactive uplink control information scheduling assisting information format. The selected random access mode may comprise at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

[ 0064 ] An example embodiment may be provided with an apparatus comprising: circuitry configured to determine a size of data in a buffer of the apparatus; circuitry configured to select a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer; and circuitry configured to transmit a message from the apparatus to a node based, at least partially, upon the selected random access mode.

[ 0065 ] An example method may be provide comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[ 0066 ] The received message may comprise information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) . The determining of the random access mode selected by the user equipment may comprise determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message. However, the determination of the RA mode may be based on the selected RACH resources; not only 2-step versus 4-step resources such as, for example, by selecting a specific preamble, the UE may indicate "2-step small data transmission (SDT) based on UCI-SAI PUSCH" RA mode (as compared to e.g. "2-step RA with UP data transmission after MsgB" RA mode) . The method may further comprise determining whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message. An implementation may be provide where the gNB may determine the RA mode (e.g. "2-step small data transmission (SDT) based on UCI-SAI PUSCH" vs. "2-step SDT") based on the presence or absence of BSR in the received message.

[0067] An example embodiment may be provided with an apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: receive a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determine a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[0068] The received message may comprise information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) . The determining of the random access mode selected by the user equipment may comprise determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message. The apparatus may be configured to determine whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.

[0069] An example embodiment may be provided with a non- transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[0070] An example embodiment may be provide in an apparatus comprising: means for receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; means for determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[0071] An example embodiment may be provide in an apparatus comprising: circuitry configured to receive a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; circuitry configured to determine a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

[0072] The received message may comprise information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) . The apparatus may be configured such that the determining of the random access mode selected by the user equipment comprises determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message. The apparatus may further comprise means for determining whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.

[0073] With features as described herein, a dedicated UCI format may be provided for a UE in RRC inactive to carry RA Preamble associated control information PUSCH in MsgA in 2-Step RA along with Information Element (IE) at least BSR, and potentially BSR+CSI to guide the assignment of a subsequent grant.

[0074] With features as described herein, the UCI-SAI format may be based on the network configured thresholds, such as maxTBSMsgA and maxTBSMsg3 for example.

[0075] With features as described herein, the UE may be configured to select among Random Access (RA) modes (such as 4-Step or 2-Step RACH, 2-Step Small Data Transmission ( SDT ) or 2-Step SDT based UCI-SAI PUSCH) based on two NW- controlled thresholds.

[0076] With features as described herein, a gNB may be configured to determine the RA mode selected by the UE on the basis of a selected preamble or the absence of a UCI- SAI format, and also determine the need for additional grants based on the presence or the absence of a buffer status report (BSR) .

[0077] Features may be used with small data transmission with a reduced power consumption in scenarios such as URLLC, mMTC, Industrial Automation, MIoT and eMBB for example .

[0078] An example method may comprise determining a size of data in a buffer of a user equipment; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

[0079] The message may comprise at least scheduling assisting information. The scheduling assisting information may comprise data including at least one of a Buffer status report or an observed channel state information. The message may comprise message-A of a 2- step Random Access mode or message-3 of a 4-step Random Access mode.

[0080] An example embodiment may be provided in an apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: determine a size of data in a buffer of the apparatus; select, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmit a message from the apparatus to a node as part of the random access procedure according to the selected random access mode. The scheduling assisting information may comprise at least one of a buffer status report or an observed channel state information

[0081] An example embodiment may be provide in a non- transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: determining a size of data in a buffer of a user equipment; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode .

[0082] An example embodiment may be provide with an apparatus comprising: means for determining a size of data in a buffer of the apparatus; means for selecting, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and means for transmitting a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

[0083] An example embodiment may be provide with an apparatus comprising: circuitry configured to determine a size of data in a buffer of the apparatus; circuitry configured to select, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and circuitry configured to transmit a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

[0084] It should be understood that the foregoing description is only illustrative. Various alternatives and modifications can be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination ( s ) . In addition, features from different embodiments described above could be selectively combined into a new embodiment. Accordingly, the description is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims .

Claims

CLAIMS What is claimed is:

1. A method comprising: determining a size of data in a buffer of a user equipment ; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

2. A method as in claim 1 where the message comprises at least scheduling assisting information.

3. A method as in claim 2 where the scheduling assisting information comprises data including at least one of a Buffer status report or an observed channel state information .

4. A method as in claim 1 where the message comprises message-A of a 2-step Random Access mode or message-3 of a 4-step Random Access mode.

5. A method as in claim 1 where the selecting of the random access mode is based upon comparing the size of the data in the buffer to the at least two network configured thresholds .

6. A method as in claim 5 where the selecting comprises: selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold.

7. A method as in claim 6 where the selecting comprises: selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds.

8. A method as in any one of claims 1-7 where the selected random access mode comprises a RRC inactive uplink control information scheduling assisting information format.

9. A method as in any one of claims 1-7 where the selected random access mode comprises at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

10. An apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: determine a size of data in a buffer of the apparatus ; select, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmit a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

11. The apparatus as in claim 10 where the message comprises at least scheduling assisting information, where the scheduling assisting information comprises at least one of a buffer status report or an observed channel state information .

12. The apparatus as in claim 10 where the apparatus is configured to select the random access mode based upon comparing the size of the data in the buffer to the at least two network configured thresholds.

13. The apparatus as in claim 12 where the apparatus is configured to: select a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; select a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold.

14. The apparatus as in claim 13 where the apparatus is configured to: select a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds.

15. The apparatus as in any one of claims 10-14 where the selected random access mode comprises a RRC inactive uplink control information scheduling assisting information format .

16. The apparatus as in any one of claims 10-14 where the selected random access mode comprises at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

17. A non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: determining a size of data in a buffer of a user equipment ; selecting, for a random access procedure, a random access mode by the user equipment, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and transmitting a message from the user equipment to a node as part of the random access procedure according to the selected random access mode.

18. The non-transitory program storage device as in claim

17 where the message comprises at least scheduling assisting information, where the scheduling assisting information comprises at least one of a buffer status report or an observed channel state information.

19. The non-transitory program storage device as in claim

18 where the selecting of the random access mode is based upon comparing the size of the data in the buffer to the at least two network configured thresholds.

20. The non-transitory program storage device as in claim

19 where the selecting comprises: selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold.

21. The non-transitory program storage device as in claim 20 where the selecting comprises: selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds.

22. The non-transitory program storage device as in any one of claims 17-21 where the selected random access mode comprises a RRC inactive uplink control information scheduling assisting information format.

23. The non-transitory program storage device as in any one of claims 17-21 where the selected random access mode comprises at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

24. An apparatus comprising: means for determining a size of data in a buffer of the apparatus; means for selecting, for a random access procedure, a random access mode by the apparatus, where the random access mode is selected based at least partially upon the determined size of the data in the buffer and at least two network configured thresholds; and means for transmitting a message from the apparatus to a node as part of the random access procedure according to the selected random access mode.

25. The apparatus as in claim 24 where the message comprises at least scheduling assisting information, where the scheduling assisting information comprises at least one of a buffer status report or an observed channel state information .

26. The apparatus as in claim 25 where the means for selecting the random access mode is based upon comparing the size of the data in the buffer to the at least two network configured thresholds.

27. The apparatus as in claim 26 where the means for selecting comprises: means for selecting a first one of the random access modes when the size of the data in the buffer is less than a first one of the network configured thresholds; means for selecting a second one of the random access modes when the size of the data in the buffer is greater than the first network configured threshold.

28. The apparatus as in claim 27 where the means for selecting comprises: means for selecting a third one of the random access modes when the size of the data in the buffer is greater than a second one of the network configured thresholds .

29. The apparatus as in any one of claims 24-28 where the selected random access mode comprises a RRC inactive uplink control information scheduling assisting information format .

30. The apparatus as in any one of claims 24-28 where the selected random access mode comprises at least one of: a 4-Step Random Access Channel or a 2-Step Random Access Channel, or a 2-Step Small Data Transmission (SDT) , or a 2-Step small data transmission (SDT) based uplink control information scheduling assisting information (UCI-SAI) Physical uplink Shared Channel (PUSCH) .

31. A method comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message .

32. A method as in claim 31 where the received message comprises information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) .

33. A method as in any one of claims 31-32 where the determining of the random access mode selected by the user equipment comprises determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message.

34. A method as in any one of claims 31-33 further comprising determining whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.

35. An apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: receive a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determine a random access mode selected by the user equipment based upon the message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message .

36. The apparatus as in claim 35 where the received message comprises information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) .

37. The apparatus as in any one of claims 35-36 where the determining of the random access mode selected by the user equipment comprises determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message.

38. The apparatus as in any one of claims 35-37 where the apparatus is configured to determine whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.

39. A non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message .

40. The non-transitory program storage device as in claim 39 where the received message comprises information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) .

41. The non-transitory program storage device as in any one of claims 39-40 where the determining of the random access mode selected by the user equipment comprises determining: whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message.

42. The non-transitory program storage device as in any one of claims 39-41 where the operations further comprise determining whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.

43. An apparatus comprising: means for receiving a message from a user equipment while the user equipment is in a Radio Resource Control inactive state, where the message comprises a preamble and data; means for determining a random access mode selected by the user equipment based upon the received message including a format of a medium access control (MAC) control protocol data unit (PDU) format in the received message.

44. The apparatus as in claim 43 where the received message comprises information elements carrying a Buffer Status Report (BSR) and Channel State Information (CSI) .

45. The apparatus as in any one of claims 43-44 where the apparatus is configured such that the determining of the random access mode selected by the user equipment comprises determining : whether the message received from the user equipment was transmitted with 4-step random access resources, or whether the message received from the user equipment was transmitted with 2-step random access resources, and content in the message.

46. The apparatus as in any one of claims 43-45 where the apparatus further comprises means for determining whether there is a need for additional grants based on a presence or an absence of a Buffer Status Report (BSR) in the received message.