Method and apparatus for performing contention-based random access in a carrier frequency

Abstract

The present invention relates to a method and apparatus for performing contention-based random access in a carrier frequency. A method and a user equipment include receiving an indication from a network entity whether a cell in a carrier frequency supports a 2-step random access procedure. When the 2-step random access procedure is supported in the cell, a random access procedure is selected between the 2-step random access procedure and the 4-step random access procedure, wherein each of the 2-step random access procedure and the 4-step random access procedure includes one or more preambles, which are configured in the cell to be associated with one of the 2-step random access procedure or the 4-step random access procedure. A preamble is randomly selected and sent from one or more preambles associated with the selected random access procedure, wherein a time-frequency resource is determined based on the sent preamble. A physical random access channel carrying data including a demodulation reference signal and one or more data symbols is sent on the determined time-frequency resource.

Description

[0001] This application is a divisional application of the Chinese invention patent application "Method and device for performing contention-based random access in a carrier frequency" with PCT application number PCT / US2018 / 013912, international application date January 16, 2018, and Chinese application number 201880006410.3, which entered the Chinese national phase on July 10, 2019. Technical Field

[0002] The present disclosure relates to methods and apparatus for performing contention-based random access in a carrier frequency of a communication network, and more particularly, to contention-based random access with a reduced number of steps in supporting lower latency communications. Background Art

[0003] Currently, user equipment such as wireless communication devices communicate with other communication devices using wireless signals such as in a network environment that may include one or more cells, within which various communication connections with the network and other devices operating within the network may be supported. The network environment typically involves one or more sets of standards, each set of standards defining various aspects of any communication connection made when a corresponding standard is used in the network environment. Examples of developing and / or existing standards include new radio access technology (NR), long term evolution (LTE), universal mobile telecommunications service (UMTS), global system for mobile communications (GSM), and / or enhanced data GSM environment (EDGE).

[0004] When operating within a network, the standards will define the manner in which a user device communicates with the network, including initiating a new connection or refreshing an existing connection that has become stale, such as in the case of a loss of synchronization between the user device and the network access point. At least some developing and / or existing standards use a random access procedure to support establishing a new connection or refreshing an already existing connection. Contention-based random access can facilitate the possibility that multiple communication devices may be interested in attempting to access the network through a random access procedure at the same or similar point in time. Once access is established and / or confirmed, the network can assign network resources to a particular user device to support uplink communications with the network.

[0005] However, the random access procedure, which is a preamble step to make network resources available to user equipment by the network, represents a signaling overhead to support uplink communications, which can also affect the delay associated with any particular communication. Typically, the process is supported by a four-step interaction, which can better accommodate the assumed worst case scenario. The inventors have recognized that in some cases, a two-step process may be sufficient. Therefore, the inventors further recognize that it may be beneficial to support both the two-step and four-step processes, whereby situations and conditions associated with the selective beneficial application of the two-step and four-step processes can be identified and encoded as part of the process accordingly. Such a process can improve communication delays where possible, and also continue to provide a more robust process based on the determined current situation associated with the specific communication requested. Summary of the invention

[0006] Currently, user equipment such as wireless communication devices use wireless signals to communicate with other communication devices. According to a possible embodiment, a method in a user equipment is provided. The method includes receiving an indication that a cell in a carrier frequency supports a 2-step random access procedure. A physical random access channel preamble is sent on a first time-frequency resource. A physical uplink channel carrying data is sent, wherein the physical uplink channel carrying the data is associated with the sent physical random access channel preamble. In response to the sent physical random access channel preamble and the sent physical uplink channel carrying the data, a user equipment specific channel is received within a random access response window. The data includes a user equipment identification.

[0007] According to another possible embodiment, a user equipment is provided. The user equipment includes a controller. The user equipment further includes a transceiver, which receives an indication that a cell in a carrier frequency supports a 2-step random access process and sends a physical random access channel preamble on a first time-frequency resource. A physical uplink channel carrying data is sent by the transceiver, wherein the physical uplink channel carrying the data is associated with the sent physical random access channel preamble. In response to the sent physical random access channel preamble and the sent physical uplink channel carrying the data, a user equipment specific channel is received within a random access response window. The data includes a user equipment identifier.

[0008] These and other objects, features and advantages of the present application will be apparent from the following description of one or more preferred embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a block diagram of an exemplary network environment suitable for operation of the present invention;

[0010] Figure 2is an overview of a plurality of communication zones in an exemplary cellular communication system;

[0011] Figure 3 is an example timing relationship for asynchronous multi-user uplink transmission;

[0012] Figure 4 is a graph of the block error rate performance of a physical random access channel carrying data for various receive timing offsets;

[0013] Figure 5A and 5B is an exemplary physical channel structure of a 2-step random access channel, which includes Figure 5A Example resource allocation of a physical random access channel carrying a preamble and a physical random access channel carrying data in Figure 5B Example symbol structure of a physical random access channel carrying data in;

[0014] Figure 6 is a flow chart of a user equipment performing contention-based random access in a carrier frequency according to a possible embodiment;

[0015] Figure 7 is a flow chart of a network entity performing contention-based random access in a carrier frequency according to a possible embodiment;

[0016] Figure 8 is an example block diagram of an apparatus according to a possible embodiment. DETAILED DESCRIPTION

[0017] While the present disclosure may be susceptible of various forms of embodiment, there is shown in the drawings and will be described below a presently preferred embodiment, it being understood that this disclosure is to be considered as exemplification of the invention and is not intended to limit the invention to the particular embodiment shown.

[0018] The embodiments provide a method and apparatus for performing contention-based random access in a carrier frequency.

[0019] Figure 1 is an example block diagram of a system 100 according to a possible embodiment. The system 100 may include a wireless communication device 110 such as a user equipment (UE), a base station 120 such as an enhanced Node B (eNB) or a next generation Node B (gNB), and a network 130. The wireless communication device 110 may be a wireless terminal, a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a personal digital assistant, a personal computer, a selective call receiver, a tablet computer, a laptop computer, or any other device capable of sending and receiving communication signals over a wireless network.

[0020] The network 130 may include any type of network capable of sending and receiving wireless communication signals. For example, the network 130 may include a wireless communication network, a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, a long term evolution (LTE) network, a fifth generation (5G) network, a 3rd generation partnership project (3GPP)-based network, a satellite communication network, a high altitude platform network, the Internet, and / or other communication networks.

[0021] In at least some cases, a network will provide coverage across a geographic area, where in at least some cases the coverage area will be divided into multiple regions, at least sometimes referred to as cells. Figure 2 2 is an overview of multiple communication zones 202 in an exemplary cellular communication system 200. In many cellular communication networks, each of the multiple communication zones is typically associated with a specific base station 204, which is intended to communicate with compatible user equipment 206 located within the associated communication zone 202 and serves as an access point to the communication network. In some cases, more than one base station may support a specific communication zone, such as in an edge region where zones may overlap. In some cases, a specific base station may support one or more communication zones. In the illustrated embodiment, each specific base station 204 may support at least three zones 202, with the base station located at a shared vertex in each of the three zones.

[0022] The user equipment 206 will typically communicate wirelessly with the base station 204 using radio frequency signaling. Depending on the location within the communication area 202, the radio frequency signaling received between the base station 204 and the user equipment 206 will experience varying degrees of delay and attenuation, which needs to be managed as part of the user equipment's attempt to communicate with the base station 204. The degree of delay and attenuation will typically depend on the distance between the user equipment and the base station, where user equipment that is closer relative to the base station will typically experience less delay and attenuation, and user equipment that is farther away will typically experience more delay and attenuation. Other factors, such as the presence and nature of any obstacles in the communication path between the user equipment and the base station may also have an impact on the degree of delay and attenuation. For example, the wireless signaling between user equipment 1 and the base station may have an associated first propagation delay Tp1, and the wireless signaling between user equipment 2 and the base station may have an associated second propagation delay Tp2. Accordingly, the relative propagation delays between all user equipment that intend to communicate with a particular base station will have an associated delay spread, which corresponds to the difference between the various amounts of delay currently experienced relative to the associated wireless signaling transmissions.

[0023] In LTE, the Random Access Channel (RACH) is used for uplink synchronization or scheduling requests. The contention-based random access procedure of the user equipment (UE) previously typically includes four steps; preamble transmission, reception of a random access response (RAR) message, layer 2 / 3 message transmission, and reception of a contention resolution message. A contention-free random access procedure for situations where downlink (DL) data arrives or during handover can reduce delays in random access because the UE performs two steps, namely sending an assigned preamble and receiving a RAR message, instead of four steps.

[0024] In fifth generation (5G) radio access technology (RAT) or new RAT (NR), a contention-based 2-step RACH procedure may be considered to reduce the signaling overhead and delay associated with RACH. This may be the case for small data transmission and / or operation in unlicensed bands. In the present disclosure, a physical layer design supporting a contention-based 2-step RACH procedure is proposed.

[0025] For the contention-based 2-step RACH procedure, two approaches have been considered:

[0026] (1) The case where the message is embedded in a random access preamble; and

[0027] (2) The case where the message and preamble are sent separately.

[0028] For the contention-based 2-step RACH procedure, the message 1 (Msg1) may include at least a UE identity (ID) and some radio resource control (RRC) messages and a preamble, wherein the payload size may be up to, for example, 100 to 150 bits. However, the first method involving embedding the message in the RACH preamble may not be suitable for accommodating the corresponding Msg1 size within the range of 100 to 150 bits.

[0029] In the case where the message and preamble are transmitted separately, detailed design aspects of the physical channel carrying Msg1, such as how to indicate the modulation and coding scheme (MCS) and the channel structure, are generally not previously disclosed.

[0030] According to a possible embodiment, the contention based 2-step RACH procedure may be more suitable for small cells, eg up to 2 km cell radius, since a larger cell size may increase the potential timing offset at the receiver, which depends on the propagation delay. Figure 3 1 shows example timing relationships for asynchronous multi-user uplink transmissions. More specifically, Figure 3It is shown that a UE with a large propagation delay, such as UE1, can have a timing offset close to the data symbol duration "Ts". "Tp1" corresponds to the propagation delay of user equipment 1 relative to the base station gNB. "Tp2" corresponds to the propagation delay of user equipment 2 relative to the base station gNB. "To" corresponds to the processing and switching time of the base station gNB. Timing offsets that are much larger than the cyclic prefix (CP) length in orthogonal frequency division multiplexing (OFDM) and / or involving discrete Fourier transform spread OFDM (DFT-S-OFDM) symbols may significantly degrade the demodulation performance of the physical random access channel (PRACH-D) carrying data, such as Figure 4 shown. Figure 4 A graph showing the Block Error Rate (BLER) performance of PRACH-D for various receive timing offsets, assuming perfect detection of the preamble and timing offset, and more specifically, a graph showing the Block Error Rate as a function of the Signal-to-Noise Ratio measured in decibels for 100 information bits included in 3 symbols across 36 subcarriers, where the information bits are encoded using Quadrature Phase Shift Keying. Thus, a network entity (NE) is able to determine and accordingly indicate whether a given cell is configured to support contention-based 2-step RACH via system information or a dedicated higher layer message such as a Radio Resource Control message. Hereinafter, the 2-step RACH procedure refers to the contention-based 2-step RACH procedure.

[0031] UE RACH process selection and SR resource configuration

[0032] For a given cell, a network entity (NE) may configure common time / frequency radio resources for a physical random access channel (PRACH-P) carrying preambles, but configure two mutually exclusive subsets of preambles for 2-step RACH and 4-step RACH procedures, respectively. A user equipment (UE) may select one of the RACH procedures, such as the 2-step RACH procedure or the 4-step RACH procedure, based on path loss estimation or reference signal received power (RSRP) measurement, and may send a PRACH preamble randomly selected from the corresponding subset of the selected RACH procedure. For example, out of 64 preambles configured for a cell, 16 preambles may be assigned for the 2-step RACH procedure, and 48 preambles may be assigned for the 4-step RACH procedure. If the reference signal received power (RSRP) value is greater than the configured RSRP threshold, the UE may select the 2-step RACH procedure.

[0033] In addition, the network entity (NE) can semi-statically change the number of preambles assigned for the 2-step RACH procedure and the 4-step RACH procedure based on RSRP measurement reports received from UEs in a radio resource control (RRC) connected state and / or an RRC inactive state. For example, if the NE observes an increase in RRC-connected UEs with RSRP values ​​above a threshold, it can assign a larger number of preambles for the 2-step RACH procedure. In addition, the NE can utilize scheduling request (SR) resources to configure UEs whose RSRP values ​​are below a threshold so that they can avoid longer 4-step RACH procedures for SR resources and can perform low-latency uplink transmissions. For UEs with higher RSRP values ​​that can potentially perform a 2-step RACH procedure, the NE can choose not to configure dedicated SR resources to reduce system overhead.

[0034] DM in Message 1 Data Transmission of 2-Step RACH Procedure RS

[0035] A network entity (NE) may configure a set of time-frequency radio resources for PRACH-D in a cell, each of which is associated with a given PRACH preamble sequence. If the NE employs advanced receivers such as parallel or serial interference cancellation, two or more PRACH preambles may be associated with one PRACH-D time-frequency radio resource. A user equipment (UE) performing a 2-step RACH procedure transmits a PRACH preamble and a PRACH-D in the resources associated with the transmitted preamble.

[0036] Once the NE detects a specific preamble and obtains the timing and frequency information of the UE that sent the detected preamble, it can perform demodulation and decoding of the corresponding PRACH-D. The received PRACH-D may have a timing offset of up to the maximum round-trip propagation delay relative to the reference receive timing of the physical uplink shared channel (PUSCH). Note that the PUSCH is sent with an appropriate timing advance (TA) value and is received with a timing aligned with the reference receive timing. For a given subcarrier spacing, if the CP length of the PRACH-D is set to the same as the CP length of the PUSCH, the NE receiver can compensate for the frequency offset and apply a fast Fourier transform (FFT) based on the acquired frequency and timing information. The receiver may have to perform multiple FFT operations with different receive timings for multiple detected preambles without increasing the CP overhead. If the number of subcarriers allocated to each PRACH-D resource is small, such as 12 subcarriers, the FFT complexity can be reduced, for example, from an FFT size of 1024 to an FFT size of 16 by time domain frequency shifting, downsampling, and anti-aliasing filtering. Alternatively, the CP length and subcarrier spacing of PRACH-D can be the same as those of PRACH-P, potentially with a CP length that is much longer than that of PUSCH.

[0037] In one embodiment, PRACH-D carries a demodulation reference signal (DM RS), and the DM RS of PRACH-D is transmitted with a longer CP length (longer than the CP length of the PRACH-D data symbol) and a guard time (GT) attached to the DM RS symbol. The CP length of the DM RS of PRACH-D is determined based on the maximum round trip delay and the maximum delay spread of the UE that selects the 2-step RACH process in the cell. The guard time (GT) of the DM RS of PRACH-D is also determined based on the maximum round trip delay of the UE that performs the 2-step RACH process in the cell. The PRACH-D data symbol can use the same CP length as the PUSCH and does not include the GT. If the cell is large, for example, a 5km cell radius, and if the UE within the 2km radius is expected to perform the 2-step RACH process based on the RSRP (or path loss) threshold setting, the CP length of the DM RS of PRACH-D is longer than the CP length of the PRACH-D data symbol, but less than the CP length of the PRACH preamble. In another embodiment, the DM RS of PRACH-D has a longer CP, but no GT is attached. Figure 5A and 5B An exemplary physical channel structure showing a 2-step RACH procedure is shown, comprising Figure 5A Example resource allocation for PRACH-P and PRACH-D in Figure 5B Example symbol structure for PRACH-D in FIG.

[0038] An example symbol structure for PRACH-D includes a demodulation reference signal (DM RS) 502 preceded by a cyclic prefix (CP) 504 and followed by groups of data symbols 506, each of which is preceded by a cyclic prefix 508. In the illustrated embodiment, the cyclic prefix 508 preceding each group of data symbols 506 is shorter than the cyclic prefix 504 preceding the demodulation reference signal 502.

[0039] A longer CP length will help facilitate synchronous reception of DM RS, which allows DM RS to be received without severe inter-carrier interference caused by a timing offset greater than the CP length. When the operating signal-to-interference-plus-noise ratio (SINR) range is low due to a small payload, channel estimation performance may be important for overall demodulation performance. Therefore, low inter-carrier interference (ICI) or ICI-free reception of DM RS is conducive to achieving good demodulation performance of PRACH-D. In addition, when two or more PRACH preambles are associated with the same time-frequency resources of PRACH-D, and multiple orthogonal DM RSs of multiple PRACH-Ds are multiplexed in the same time-frequency resources, the longer CP of DM RS can maintain the orthogonality of multiple orthogonal DM RSs, such as Zadoff-Chu (ZC) sequences and their cyclic shifts. In one embodiment, the DM RS sequence of PRACH-D is determined by the preamble index or according to the order of the preamble indexes of the preambles associated with the same time-frequency resources of PRACH-D.

[0040] In another embodiment, the user equipment (UE) can indicate the modulation order and payload size of PRACH-D by selecting an appropriate DM RS sequence for PRACH-D. Since PRACH-D carries data of typically limited size, such as UE ID, buffer status report (BSR), and small-size user data, modulation can be limited to one or two low-order modulation schemes, such as binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK), and only a few payload sizes may need to be supported. In one example, 6 selections of combinations of modulation and payload size are supported in PRACH-D, and 6 different DM RS sequences are used to indicate the selected modulation and payload size. In addition, PRACH-D is allocated 12 subcarriers per symbol, two PRACH preambles such as preamble 1 and preamble 2 are associated with a given PRACH-D resource, and the DMRS occupies all subcarriers within the DM RS symbol. If 12 cyclic shifts of the root Zadoff-Chu (ZC) sequence are available for DMRS, the first 6 cyclic shifts of the root ZC sequence are used for DM RS of PRACH-D associated with preamble 1, and the last 6 cyclic shifts are used for DM RS-D associated with preamble 2.

[0041] In another embodiment, the channel bits (coded and rate matched bits) of PRACH-D are scrambled by a scrambling sequence, which can be based on the cell / TRP (transmit and receive point) ID and the preamble sequence index. When two or more preambles are associated with a given PRACH-D time / frequency resource, preamble sequence specific scrambling will be beneficial to combat co-channel interference.

[0042] Random Access Response (RAR) message

[0043] In one embodiment, if the UE is in an RRC connected state or in an RRC inactive state, for example, the UE has a valid UE ID assigned by the cell, such as a cell-radio network temporary identifier (C-RNTI), the UE may receive a RAR message as downlink control information (DCI) in a UE-specific search space. If the network entity (NE) detects the preamble and successfully decodes the corresponding data, the random access response (RAR) message may be UE-specific. That is, the RAR message may be sent in a UE-specific channel and may be addressed by the C-RNTI (i.e., the additional cyclic redundancy check (CRC) bits are scrambled by the C-RNTI), where the NE may obtain the C-RNTI from decoding the PRACH-D. When there are no SR resources configured for the UE or the uplink (UL) timing information is not up to date, the connected mode UE performs a contention-based RACH procedure. Therefore, according to a special UL downlink control information (DCI) format, a RAR message carrying UL transmit timing advance (TA) information and UL scheduling grant for subsequent UL data transmission may be sent in a UE-specific physical downlink control channel (PDCCH). In addition to typical UL scheduling grant related information, the special UL DCI format also includes a bit field for timing advance (TA) information.

[0044] If the NE detects the preamble but fails to successfully decode the corresponding data, the NE sends a RAR message in a common physical downlink shared channel (PDSCH), and the DCI carrying the scheduling information for the RAR transmission is addressed by a random access-radio network temporary identifier (RA-RNTI), such as the CRC bits attached to the DCI are scrambled by the RA-RNTI. The RA-RNTI can be determined by the time and frequency resources used for PRACH-P.

[0045] An RRC-connected or RRC-inactive UE performs blind decoding of PDCCH in both UE-specific search space and common search space. During the RACH response window, the UE additionally performs blind decoding of a special UL DCI format to receive a RAR message.

[0046] Figure 6 An exemplary flow chart 600 is shown of a user equipment performing contention-based random access in a carrier frequency according to a possible embodiment. The flow chart illustrates the operation of a wireless communication device, such as the user equipment 110, according to at least one possible embodiment. At 602, an indication is received from a network entity, which identifies whether a cell in the carrier frequency supports a 2-step random access procedure. When the 2-step random access procedure is supported in the cell 604, the user equipment selects 606 a random access procedure between a 2-step random access procedure and a 4-step random access procedure. Each of the 2-step random access procedure and the 4-step random access procedure includes one or more associated preambles. A preamble is then randomly selected and sent 608 from the one or more preambles associated with the selected random access procedure. The 2-step random access procedure includes a physical random access channel carrying a preamble and a physical random access channel carrying data. The 4-step random access procedure includes a physical random access channel carrying a preamble. Based on the sent preamble, a time-frequency resource for the physical random access channel carrying data in the 2-step random access procedure is determined. A physical random access channel carrying data including a demodulation reference signal and one or more data symbols is sent on the determined time-frequency resource 610 .

[0047] In at least some embodiments, flow chart 600 may be extended to include selection by the user equipment of one of a 2-step random access procedure or a 4-step random access procedure. In some cases, the selection will be based on a path loss estimate, wherein if the path loss estimate is less than a predetermined path loss estimate threshold, the 2-step random access procedure is selected, and if the path loss estimate is greater than a predetermined path loss estimate threshold, the 4-step random access procedure is selected. In other cases, the selection may be based on a reference signal received power measurement, wherein if the reference signal received power measurement is greater than a predetermined reference signal received power measurement threshold, the 2-step random access procedure is selected, and if the reference signal received power measurement is less than a predetermined reference signal received power measurement threshold, the 4-step random access procedure is selected.

[0048] In some cases, when the user equipment selects the 4-step random access procedure, the user equipment may be configured with scheduling request resources by the network entity.

[0049] The same or other situations may allow that, when one or more preambles are associated with each of a 2-step random access procedure or a 4-step random access procedure, the preambles used in the cell may be configured as two mutually exclusive subsets of preambles, which are associated with the corresponding random access procedures in the 2-step random access procedure and the 4-step random access procedure, respectively. Based on one or more reference signal received power measurement reports received from one or more user equipments in the cell, the network entity may semi-statically change the number of preambles in each of the two mutually exclusive subsets of preambles. In addition, the number of preambles in each of the two mutually exclusive subsets of preambles may be based on a ratio of the number of reference signal received power measurements included in the reference signal received power measurement reports received from the one or more user equipments in the cell that are greater than a predetermined reference signal received power measurement threshold to the number of reference signal received power measurements included in the reference signal received power measurement reports received from the one or more user equipments in the cell that are less than the predetermined reference signal received power measurement threshold.

[0050] In some cases, the demodulation reference signal sequence may be determined based on at least one of a modulation order of a physical random access channel carrying data, a payload size of a physical random access channel carrying data, or a preamble sequence index of a transmitted preamble.

[0051] In some cases, a demodulation reference signal symbol of a physical random access channel carrying data may have a longer cyclic prefix than one or more data symbols of the physical random access channel carrying data. In some of these cases, the cyclic prefix length of the demodulation reference signal symbol of the physical random access channel carrying data may be determined based on the maximum round trip delay of a user equipment performing a 2-step random access procedure in the cell. The demodulation reference signal symbol of the physical random access channel carrying data may also have a protection time based on the maximum round trip delay of a user equipment performing a 2-step random access procedure in the cell. The cyclic prefix length of the demodulation reference signal symbol of the physical random access channel carrying data may also and / or alternatively be determined based on the maximum delay spread of all user equipment selecting a 2-step random access procedure in the cell.

[0052] In some cases, channel bits of a physical random access channel carrying data may be scrambled by a scrambling sequence. In some of these cases, the scrambling sequence may be based on a network entity identity and a preamble index.

[0053] In some cases, when the user equipment has a valid user equipment identity assigned by the cell, the user equipment may include the valid user equipment identity in a physical random access channel carrying data, and may receive a random access response message as downlink control information in a user equipment specific search space. In some of these cases, the valid user equipment identity may be a cell-radio network temporary identifier, and the user equipment specific search space in which the random access response message is sent may include a user equipment specific physical downlink control channel, wherein the additional cyclic redundancy check bits may be scrambled by the cell-radio network temporary identifier. It is also possible that the downlink control information of the random access response message may include a field for an uplink timing advance value. It is further possible that the physical downlink control channel may be monitored for both the user equipment specific search space and the common search space for receiving the random access response message, wherein monitoring the physical downlink control channel may include attempting to decode the physical downlink control channel, assuming a first payload size of the user equipment specific search space and assuming a second payload size of the common search space, wherein the additional cyclic redundancy check bits in the physical downlink control channel of the common search space are scrambled by the random access-radio network temporary identifier.

[0054] Figure 7 An exemplary flow chart 700 is shown of a network entity performing contention-based random access in a carrier frequency according to a possible embodiment. The flow chart illustrates operations in a network entity according to at least one possible embodiment, which network entity may include a base station 120 and / or other elements from a network 130. At 702, one or more preambles are configured to be associated with each supported random access procedure including a 2-step random access procedure and a 4-step random access procedure for a cell in a carrier frequency. An indication of whether a cell in a carrier frequency supports a 2-step random access procedure in addition to a 4-step random access procedure and the corresponding associated one or more preambles is provided 704 to a user equipment. When a 2-step random access procedure is supported in a cell, a selected preamble is received 708 from a user equipment, the preamble being randomly selected from one or more preambles configured to be associated with a selected one of a 2-step random access procedure and a 4-step random access procedure. The 2-step random access procedure includes a physical random access channel carrying a preamble and a physical random access channel carrying data. The 4-step random access procedure includes a physical random access channel carrying a preamble. Based on the received preamble, the time-frequency resources of the physical random access channel carrying data in the 2-step random access process are determined. Then, the physical random access channel carrying data including a demodulation reference signal and one or more data symbols is received on the determined time-frequency resources 710.

[0055] It should be understood that, despite the specific steps shown in the figures, various additional or different steps may be performed, depending on the embodiment, and one or more specific steps may be rearranged, repeated, or completely eliminated, depending on the embodiment. Moreover, some steps that have been performed may be repeated on a continuous or consecutive basis while other steps are performed. Furthermore, different steps may be performed by different elements or in a single element of the disclosed embodiments.

[0056] Figure 8 8 is an example block diagram of an apparatus 800, such as a wireless communication device 110, according to a possible embodiment. The apparatus 800 may include a housing 810, a controller 820 within the housing 810, an audio input and output circuit 830 coupled to the controller 820, a display 840 coupled to the controller 820, a transceiver 850 coupled to the controller 820, an antenna 855 coupled to the transceiver 850, a user interface 860 coupled to the controller 820, a memory 870 coupled to the controller 820, and a network interface 880 coupled to the controller 820. The apparatus 800 may perform the methods described in all embodiments.

[0057] The display 840 may be a viewfinder, a liquid crystal display (LCD), a light emitting diode (LED) display, a plasma display, a projection display, a touch screen, or any other device that displays information. The transceiver 850 may include a transmitter and / or a receiver. The audio input and output circuit 830 may include a microphone, a speaker, a transducer, or any other audio input and output circuit. The user interface 860 may include a keypad, a keyboard, a button, a touch pad, a joystick, a touch screen display, another additional display, or any other device for providing an interface between a user and an electronic device. The network interface 880 may be a universal serial bus (USB) port, an Ethernet port, an infrared transmitter / receiver, an IEEE 1394 port, a WLAN transceiver, or any other interface that can connect the device to a network, a device, or a computer and can send and receive data communication signals. The memory 870 may include a random access memory, a read-only memory, an optical memory, a solid-state memory, a flash memory, a removable memory, a hard drive, a cache, or any other memory that can be coupled to the device.

[0058] The device 800 or the controller 820 may implement any operating system, such as Microsoft or Android TM or any other operating system. The device operating software can be written in any programming language, such as C, C++, Java, or Visual Basic. The device software can also run on an application framework, such as frame, Framework or any other application framework. The software and / or operating system may be stored in the memory 870 or elsewhere on the device 800. The device 800 or the controller 820 may also use hardware to implement the disclosed operations. For example, the controller 820 may be any programmable processor. The disclosed embodiments may also be implemented on a general or special purpose computer, a programmed microprocessor or microprocessors, peripheral integrated circuit elements, application specific integrated circuits or other integrated circuits, hardware / electronic logic circuits such as discrete component circuits, programmable logic devices such as programmable logic arrays, field programmable gate arrays, etc. In general, the controller 820 may be any controller or processor device or device capable of operating the device and implementing the disclosed embodiments. Some or all of the additional elements of the device 800 may also perform some or all of the operations of the disclosed embodiments.

[0059] The method of the present disclosure can be implemented on a programmed processor. However, the controller, flow chart, and modules can also be implemented on a general or special purpose computer, a programmed microprocessor or microcontroller, and peripheral integrated circuit components, integrated circuits, hardware electronic or logic circuits such as discrete component circuits, programmable logic devices, etc. In general, any device on which a finite state machine capable of implementing the flow chart shown in the figure resides can be used to implement the processor functions of the present disclosure.

[0060] Although the present disclosure has been described with its specific embodiments, it is apparent that many alternatives, modifications and variations are apparent to those skilled in the art. For example, in other embodiments, various components of the embodiments may be interchanged, added or replaced. Moreover, all elements of each of the accompanying drawings are not necessary for the operation of the disclosed embodiments. For example, by simply adopting the elements of the independent claims, a person of ordinary skill in the field of the disclosed embodiments will be able to make and use the teachings of the present disclosure. Therefore, the embodiments of the present disclosure as described herein are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0061] In this article, relational terms such as "first", "second", etc. can be used only to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between these entities or actions. The phrase "at least one", "selected from at least one of the group of ..." or "selected from at least one of ..." followed by a list is defined as an element, some elements or all, but not necessarily all elements in the list. The term "comprise", "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also can include other elements that are not explicitly listed or inherent to such processes, methods, articles or devices. In the absence of more restrictions, the elements of "a (a)", "an (an)", etc. in front of the element do not exclude the presence of other identical elements in the process, method, article or device including the element. Moreover, the term "another" is defined as at least the second or more. The terms "including (including)", "having" etc. used herein are defined as "comprising (comprising)". In addition, the background technology section is written as the inventor's own understanding of the background of certain embodiments when filing the application, and includes the inventor's own recognition of any problems with the prior art and / or any problems experienced in the inventor's own work.

Claims

1. A method performed by a user equipment (UE), the method comprising: The receiving cell supports an indication of a 2-step random access procedure in addition to the 4-step random access procedure; receiving information on a reference signal receiving power threshold, selecting a 2-step random access procedure or a 4-step random access procedure, wherein the 2-step random access procedure or the 4-step random access procedure is selected based on a reference signal received power (RSRP) measurement value, wherein the 2-step random access procedure is selected based on the RSRP measurement value being greater than the RSRP threshold, and wherein the 4-step random access procedure is selected based on the RSRP measurement value being equal to or less than the RSRP threshold; Sending a physical random access channel (PRACH) preamble on a first time-frequency resource; transmitting a physical uplink shared channel (PUSCH) carrying data, wherein the PUSCH is associated with the PRACH preamble, wherein the data includes a UE identity; In response to the transmitted PRACH preamble and the transmitted PUSCH carrying the data, a physical downlink channel is received within a random access response window.

2. The method according to claim 1, wherein: The physical downlink channel includes cyclic redundancy check (CRC) bits scrambled by the UE identification.

3. The method according to claim 1, wherein: The UE identity comprises a Cell-Radio Network Temporary Identifier (C-RNTI).

4. The method according to claim 1, wherein: The PUSCH is sent on a second time-frequency resource, and wherein the second time-frequency resource is determined based on the sent PRACH preamble on the first time-frequency resource.

5. The method according to claim 1, further comprising: sending a demodulation reference signal (DMRS) associated with the PUSCH, wherein: A DMRS sequence of the DMRS is determined based on the transmitted PRACH preamble.

6. The method according to claim 1, wherein: The channel bits of the PUSCH are scrambled by a scrambling sequence, The scrambling code sequence is based on a preamble index of the PRACH preamble; and The preamble index is determined based on an order of the PRACH preamble among a plurality of preambles.

7. The method according to claim 6, wherein: The scrambling sequence is further based on the preamble index and a cell identity of the PRACH preamble.

8. The method according to claim 1, wherein: The multiple preambles associated with the first time-frequency resource include two mutually exclusive subsets of preambles, and the subsets are respectively associated with a corresponding one of the 2-step random access procedure and the 4-step random access procedure.

9. The method according to claim 1, wherein: The PRACH preamble is randomly selected from at least one preamble associated with the 2-step random access procedure.

10. The method according to claim 1, wherein: The physical downlink channel includes information of an uplink timing advance (TA) value.

11. The method according to claim 1, wherein: The physical downlink channel includes an uplink grant.

12. A user equipment (UE), comprising: Controller; and a transceiver coupled to the controller, wherein the controller is configured to cause the UE to: The receiving cell supports an indication of a 2-step random access procedure in addition to the 4-step random access procedure; receiving information on a reference signal receiving power threshold, selecting a 2-step random access procedure or a 4-step random access procedure, wherein the 2-step random access procedure or the 4-step random access procedure is selected based on a reference signal received power (RSRP) measurement value, wherein the 2-step random access procedure is selected based on the RSRP measurement value being greater than the RSRP threshold, and wherein the 4-step random access procedure is selected based on the RSRP measurement value being equal to or less than the RSRP threshold; Sending a physical random access channel (PRACH) preamble on a first time-frequency resource; transmitting a physical uplink shared channel (PUSCH) carrying data, wherein the PUSCH is associated with the transmitted PRACH preamble, wherein the data includes a UE identity; A physical downlink channel is received within a random access response window in response to the transmitted PRACH preamble and the transmitted PUSCH.

13. The UE according to claim 12, wherein: The PUSCH is sent on a second time-frequency resource, and wherein the second time-frequency resource is determined based on the sent PRACH preamble on the first time-frequency resource.

14. The UE according to claim 12, wherein: The channel bits of the PUSCH are scrambled by a scrambling sequence, The scrambling code sequence is based on a preamble index of the PRACH preamble; determining the preamble index based on an order of the PRACH preamble among a plurality of preambles; and The scrambling sequence is further based on the preamble index and a cell identity of the PRACH preamble.

15. The UE according to claim 12, wherein: The multiple preambles associated with the first time-frequency resource include two mutually exclusive subsets of preambles, and the subsets are respectively associated with a corresponding one of the 2-step random access procedure and the 4-step random access procedure.

16. A method performed by a base station, the method comprising: sending an indication that the base station supports a 2-step random access procedure in addition to a 4-step random access procedure; transmitting information of a reference signal received power threshold, wherein the 2-step random access procedure or the 4-step random access procedure is selected based on a reference signal received power (RSRP) measurement value, wherein the 2-step random access procedure is selected based on the RSRP measurement value being greater than the RSRP threshold, and wherein the 4-step random access procedure is selected based on the RSRP measurement value being equal to or less than the RSRP threshold; receiving a physical random access channel (PRACH) preamble on a first time-frequency resource; receiving a physical uplink shared channel (PUSCH) carrying data, wherein the PUSCH is associated with the PRACH preamble, wherein the data includes a user equipment (UE) identity; In response to the received PRACH preamble and the received PUSCH carrying the data, a physical downlink channel is sent within a random access response window.

17. A base station, comprising: Controller; and a transceiver coupled to the controller, wherein the controller is configured to cause the base station to: sending an indication that the base station supports a 2-step random access procedure in addition to a 4-step random access procedure; transmitting information of a reference signal received power threshold, wherein the 2-step random access procedure or the 4-step random access procedure is selected based on a reference signal received power (RSRP) measurement value, wherein the 2-step random access procedure is selected based on the RSRP measurement value being greater than the RSRP threshold, and wherein the 4-step random access procedure is selected based on the RSRP measurement value being equal to or less than the RSRP threshold; receiving a physical random access channel (PRACH) preamble on a first time-frequency resource; receiving a physical uplink shared channel (PUSCH) carrying data, wherein the PUSCH is associated with the PRACH preamble, wherein the data includes a user equipment (UE) identity; In response to the received PRACH preamble and the received PUSCH carrying the data, a physical downlink channel is sent within a random access response window.

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