Patent Description:
Based on the general requirements set out by the International Telecommunication Union Radiocommunication Sector (ITU-R), the Next Generation Mobile Networks (NGMN) Alliance, and the 3rd Generation Partnership Project (3GPP), a broad classification of use cases for emerging Fifth Generation (<NUM>) New Radio (NR) systems may include Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and Ultra Reliable and Low latency Communications (URLLC). Different use cases may focus on different requirements such as higher data rate, higher spectrum efficiency, low power and higher energy efficiency, lower latency and higher reliability. A wide range of spectrum bands ranging from <NUM> to <NUM> are being considered for a variety of deployment scenarios.

3GPP contribution paper R1-<NUM> relates to issues for NR initial access, synchronization signals and primary broadcast channel, and proposes that a high-level initial access procedure for NR follows that for LTE. 3GPP contribution paper R1-<NUM> relates to initial access in NR and proposes that the signals for initial access in NR can be divided into two types, signal(s) with fixed time-frequency resource allocation and signal(s) with dynamic time-frequency resource allocation. Patent application <CIT> relates to transmission and reception of common channel information using multi-antenna-based beamforming. 3GPP contribution paper R1-<NUM> relates to NR Coding Candidates for low-rate applications, and proposes that Turbo code shall be de-prioritized for NR low-rate applications. 3GPP contribution paper R1-<NUM> relates to initial access design, and makes several observations in relation to e.g. overhead and support for multiple numerologies.

Embodiments are set out in the dependent claims.

The embodiments in relationship with <FIG>, <FIG> and <FIG> are examples not covered by the scope of the claims, but useful for understanding the invention.

For example, the communications systems <NUM> may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

As shown in <FIG>, the communications system <NUM> may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) <NUM>, a core network (CN) <NUM>, a public switched telephone network (PSTN) <NUM>, the Internet <NUM>, and other networks <NUM>, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and/or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like.

Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN <NUM>, the Internet <NUM>, and/or the other networks <NUM>. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, a transmission/reception point (TRP), and the like.

In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access , which may establish the air interface <NUM> using NR.

The WTRU <NUM> may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and DL (e.g., for reception) may be concurrent and/or simultaneous. In an embodiment, the WTRU <NUM> may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the DL (e.g., for reception)).

The AP may have access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. 11e DLS or an <NUM>.

The primary channel may be a fixed width (e.g., <NUM> wide bandwidth) or a dynamically set width. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may be implemented, for example in <NUM> systems.

11af and <NUM>. 11af and <NUM>. 11n, and <NUM>. 11af supports <NUM>, <NUM>, and <NUM> bandwidths in the TV White Space (TVWS) spectrum, and <NUM>. 11ah may support Meter Type Control/Machine-Type Communications (MTC), such as MTC devices in a macro coverage area.

11n, <NUM>. 11ac, <NUM>. 11af, and <NUM>. If the primary channel is busy, for example, due to a STA (which supports only a <NUM> operating mode) transmitting to the AP, all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTls) of various or scalable lengths (e.g., containing a varying number of OFDM symbols and/or lasting varying lengths of absolute time).

The CN <NUM> shown in <FIG> may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b.

For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, and the like. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, and the like. The AMF 182a, 182b may provide a control plane function for switching between the RAN <NUM> and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP access technologies such as WiFi.

As carrier frequency increases, path loss may become severe and may limit coverage area. Transmission in millimeter wave (mmW) systems may additionally suffer from non-line-of-sight losses (for example, diffraction loss, penetration loss, oxygen absorption loss, foliage loss, etc.). During initial access, the base station and WTRU may need to overcome these high path losses and be able to discover each other. Utilizing dozens or even hundreds of antenna elements to generate a beam formed signal may be an effective way to compensate for severe path loss by providing significant beam forming gain. Beamforming techniques may include digital, analog, and hybrid beamforming.

Cell search is a procedure by which a WTRU acquires time and frequency synchronization with a cell and detects the cell ID of that cell. LTE synchronization signals may be transmitted in the <NUM>th and <NUM>th subframes of a radio frame and may be used for time and frequency synchronization during initialization. As part of the system acquisition process, a WTRU may synchronize sequentially to an orthogonal frequency-division multiplexing (OFDM) symbol, slot, subframe, half-frame, and/or radio frame based on the synchronization signals. Synchronization signals include a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS). The PSS may be used to obtain slot, subframe and half-frame boundaries. The PSS may also provide physical layer cell identity (PCI) within the cell identity group. The SSS may be used to obtain the radio frame boundary. The SSS may also enable the WTRU to determine the cell identity group, which may range from <NUM> to <NUM>.

Following a successful synchronization and PCI acquisition, the WTRU may decode a Physical Broadcast Channel (PBCH) with the help of a Cell Specific Reference Signal (CRS) and acquire the Master Information Block (MIB) information regarding system bandwidth, System Frame Number (SFN) and Physical Hybrid-ARQ Indicator Channel (PHICH) configuration. It should be noted that the LTE synchronization signals and PBCH may be transmitted according to the standardized periodicity.

The embodiments described herein address the several problems associated with the PBCH in beamforming systems:.

In New Radio (NR), it may be desirable to reduce beam sweep overhead and save energy or power for the PBCH. In NR, it may also be desirable to efficiently transmit system information using the PBCH. In NR, it may be desirable to enhance PBCH performance because information bits carried by PBCH may be critical.

PBCH transmissions may use a beam hopping transmission scheme to achieve energy efficiency. Beam hopping transmissions may be performed based on predefined beam hopping patterns. Alternatively, beam hopping transmission schemes may be performed based on a WTRU beam-location profile.

While, the methods described herein address problems associated with the PBCH in beamforming systems, the methods described herein may apply to other channels including but not limited to the paging channel.

<FIG> is a diagram of a non-claimed example PBCH beam hopping transmission based on beam hopping patterns <NUM>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. Beam hopping transmissions for PBCH may be performed based on predefined beam hopping patterns. Several hopping patterns for beams may be used. For example, even and odd beams may be used as the beam hopping pattern. For each beam sweeping cycle, a TRP or base station may perform beam sweeping on the even beams or odd beams. The even and odd beams may be swept alternately in time or frequency during different beam sweeping cycles. Beams may also be partitioned into multiple subsets of beams. Each subset of beams may be swept in different time or different beam sweeping bursts.

Each subset of beams may be assigned a sweeping frequency that may determine how often beam sweeping is performed. Depending on the directional distribution of the WTRU, if known, some subsets of beams may be assigned a higher frequency of beam sweeping than other subsets of beams that may be assigned a lower beam sweeping frequency. High density WTRU directions may be assigned a higher beam sweeping frequency and low density WTRU directions may be assigned a lower beam sweeping frequency. When the directional distribution of the WTRU is not known, subsets of beams may be assigned with the same frequency of beam sweeping. In this case, beams may be swept with equal probability. There may be Ns subsets of beams, Ωn where n = <NUM>,<NUM>,<NUM>,. A beam sweeping frequency, fn, may be assigned to beam subset Ωn, for n = <NUM>,<NUM>,<NUM>,. For beam subset Ωi with higher frequency, fi, beams may be swept more frequently than the beam subset Ωj with lower frequency, fj, for fi > fj.

Referring to <FIG>, a TRP may obtain a beam hopping pattern <NUM>. A PBCH beam hopping transmission may then be performed <NUM> based on the determined beam hopping pattern. PBCH beam hopping transmission may continue with the same beam hopping pattern <NUM>.

<FIG> is a diagram of a non-claimed example PBCH beam hopping transmission with a distribution based beam hopping pattern <NUM>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. The beam hopping pattern may be obtained <NUM>, and the PBCH beam hopping transmission may then be performed <NUM> based on the determined beam hopping pattern. The PBCH beam hopping transmission may continue with the selected beam hopping pattern <NUM>. The WTRU direction distribution may be obtained <NUM>. The beam hopping pattern may be changed as a function of the WTRU direction distribution <NUM>. The PBCH beam hopping transmission may continue with different beam hopping pattern and/or different beam sweep frequencies as a function of the WTRU direction distribution <NUM>.

The beam hopping transmission used in the examples described herein may be performed based on a WTRU beam-location profile that may be acquired by a TRP or base station. For example, an ACK-to-PBCH scheme may be used to acquire the WTRU beam-location profile. In the ACK-to-PBCH scheme, a WTRU may detect a PBCH signal for a particular beam, and it may send back an ACK to respond to that beam. The TRP or base station may obtain the beam-location profile of the WTRU according to the reported ACKs for PBCH beams.

<FIG> is a diagram of a non-claimed example PBCH beam hopping transmission based on a beam-location profile <NUM>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. In the example of <FIG>, the TRP may first obtain the beam-location profile of WTRUs for the TRP or cell by using the ACK-to-PBCH scheme <NUM>. The TRP may perform a PBCH beam hopping transmission <NUM> based on the obtained beam-location profile of the WTRUs. The TRP may continue PBCH transmission using beam hopping scheme with inverse-HARQ processes to achieve efficiency.

The TRP or base station may transmit a PBCH signal in different directions using beam sweeping. When the WTRU decodes the PBCH signal for a particular beam, the WTRU may send back an ACK to respond to that beam. The TRP or base station may receive the ACK of the beam and may learn the beam-location profile of the WTRU.

Each WTRU may send an ACK as long as it detects a PBCH signal in that beam. A cyclic redundancy check (CRC) - based ACK scheme may be used. For example, when the WTRU detects a PBCH signal and decodes it successfully (i.e., it passes the CRC test for a particular beam), a beam-specific ACK may be generated and reported by the WTRU with respect to that beam. The base station may mark the beam that has been ACK-ed when the base station receives the ACK. The base station may maintain a list of beams that have been ACK-ed. The next time the base station transmits PBCH, it may perform beam sweep on those beams which have been ACK-ed. Those ACK-ed beams may imply that there are WTRUs residing in those beams. Therefore, the ACK-to-PBCH scheme may provide the beam-location profile of WTRUs. The ACK-to-PBCH scheme may be used to implement PBCH beam hopping for PBCH transmissions. The PBCH beam hopping transmission may be energy efficient due to fewer beams participating in the beam sweep. It may also reduce the interference in a cell or to other cells due to the reduced broadcasting signal. The PBCH beam hopping transmission may also reduce latency due to potential shorter beam sweep. A short beam sweeping burst may be used to enable beam hopping to achieve low latency.

When a WTRU is stationary or WTRU mobility is low, a beam-location profile may not change. When WTRU mobility increases, the beam-location profile may change with time. Therefore, a continuing update of beam-location profile may be beneficial. Inverse HARQ processes may be used to update and refine the beam-location profile of WTRUs. However, over time the beam-location profile may be updated. This may be done by a full beam sweep. A TRP or base station may perform a full beam sweep after N TTls. The variable N may be configurable by the TRP or base station. In between two cycles of a full beam sweep, beam hopping may be used. A full beam sweep may be used to reset and update the beam-location profile of WTRUs and ensure the WTRUs receive the PBCH signal in beams of one or more of the directions. A hybrid PBCH transmission method using full beam sweeping and beam hopping sweeping may be used.

<FIG> is a diagram of a non-claimed example hybrid PBCH transmission burst using a both full beam sweep to reset and a beam hopping sweep <NUM>. Full beam sweep <NUM> for PBCH transmission may be first performed, followed by one or multiple beam hopping sweeping <NUM>, <NUM>, <NUM>. Full beam sweeping <NUM> may be performed after Nfull TTIs while beam hopping sweep <NUM>, <NUM>, <NUM> may be performed after Nhop TTls and Nhop ≤ Nfull.

If a WTRU does not receive a PBCH signal in a particular beam, the WTRU may perform the following actions. First, the WTRU may wait until next full beam sweeping to receive the PBCH signal again. Alternatively, for a preset timer, if the WTRU still does not receive PBCH signal, the WTRU may initiate an UL SYNC signal to request a PBCH signal.

Beam hopping as described in the example herein may be used for energy conservation. An energy efficiency mode using beam hopping sweeping and regular mode using full beam sweeping may be defined for PBCH transmission as follows. An energy saving mode may include PBCH transmissions using beam hopping sweeping. A regular mode may include PBCH transmissions using full beam sweeping.

Depending on the WTRU population, the base station may switch between energy saving mode and regular mode for PBCH transmission. When the WTRU population becomes large and is uniformly distributed, the TRP or base station may switch to regular mode for PBCH transmission. When the WTRU population becomes small, the TRP or base station may switch to power saving mode for PBCH transmission. That is, the TRP or base station may not transmit PBCH in one or more directions or in one or more beams. Instead the TRP or base station may transmit PBCH in certain directions or beams based on the obtained beam-location profile. When the WTRU population is large but is concentrated in certain beams or directions, the TRP or base station may also switch to power saving mode for PBCH transmission. When the TRP or base station switches to power saving mode, the TRP or base station may signal to the WTRU to report ACK again. When the TRP or base station switches to regular mode, the TRP or base station may signal to the WTRU to stop reporting ACK or continue reporting ACK but with a longer reporting period.

<FIG> is a diagram of a non-claimed example of a full beam sweep burst process for PBCH <NUM>. PBCH beams may be cycled through <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. This PBCH transmission burst may have high power and large latency.

<FIG> is a diagram of an example beam hopping sweeping process using full beam sweep bursts for the PBCH <NUM>. PBCH beams may be cycled through on certain beams <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. For example, beam <NUM><NUM>, beam <NUM><NUM>, and beam M-<NUM><NUM> may be swept through and other beams may not be swept through, although the burst may accommodate one or more M beams. This PBCH transmission method may have low power and large latency.

<FIG> is a diagram of a non-claimed example beam hopping sweeping process using short beam hopping sweep bursts for the PBCH <NUM>. A short beam sweeping burst may be used to enable beam hopping to achieve low latency. Since the beam hopping sweep burst may be shorter than a full beam sweep burst, it may reduce the latency for the WTRU to acquire PBCH signal. For TRPs or base stations that deploy M beams, a full beam sweep may include sweeping through one or more M beams, while beam hopping sweep may include sweeping through K beams and K << M. In the example of <FIG>, PBCH beams may be cycled through on certain beams. For example, beam x <NUM>, beam y <NUM>, and beam z <NUM> may be swept through. Beam x <NUM>, beam y <NUM>, and beam z <NUM> may be beam <NUM><NUM>, beam <NUM><NUM>, and beam M-<NUM><NUM> as shown in <FIG>. This PBCH transmission method may have low power and small latency.

As described above, the TRP or base station may switch between an energy saving mode and a regular mode for PBCH transmission. When the WTRU population becomes large and is uniformly distributed, the TRP or base station may switch to regular mode for PBCH transmission. When the WTRU population becomes small or the WTRU population is large but concentrates in certain beams or directions, the TRP or base station may switch to power saving mode for PBCH transmission. That is, the TRP or base station may not transmit the PBCH in one or more directions or in one or more beams. Instead the TRP or base station may transmit the PBCH in certain directions or beams based on the obtained beam-location profile.

<FIG> is a diagram of a non-claimed example of a power saving method of PBCH transmission <NUM>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. In the example of <FIG>, when the TRP or base station switches to power saving mode, it may signal to the WTRU to indicate the power saving mode. The WTRU may receive this signal from the TRP indicating the power saving operation mode <NUM>. The TRP or base station may use L1/<NUM> control, semi-static signaling, RRC signaling or a combination of them to signal to the WTRU the indication of the power saving mode and regular mode.

When the TRP or base station has switched to power saving mode <NUM>, the TRP or base station may perform PBCH transmission using a beam hopping based beam sweep (e.g., in certain directions or beams) <NUM>, and the WTRU may start to report ACKs <NUM>.

When the TRP or base station switches to regular mode <NUM>, the TRP or base station may perform PBCH transmission using a full beam sweep (e.g., in one or more directions or in one or more beams) <NUM>, and the WTRU may stop reporting ACK or continue reporting ACK but with a longer reporting period <NUM>.

When a TRP or base station receives ACK, it may imply that there is at least one WTRU attached with this beam. Thus, the TRP or base station may continue to transmit PBCH next time after a certain time window. It is unlike HARQ, where the transmitter receives ACK and the transmitter may stop transmission.

When the TRP or base station does not receive an ACK, receives a NACK, or detects DTX, it may imply that there is no WTRU attached with this beam. Thus, the TRP or base station may stop PBCH transmission or wait for certain amount of time to retransmit due to the reset cycle. Such a time window may be configurable. It is unlike HARQ, where the transmitter receives a NACK or detects DTX and the transmitter may continue the retransmission. Since it is the inverse of regular HARQ, it may be referred to as "inverse-HARQ processes". The TRP or base station may transmit the PBCH the next time if it is requested by the WTRU.

<FIG> is a diagram of a non-claimed example of a beam-centric PBCH transmission <NUM>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. The TRP may transmit the PBCH first in all beams <NUM> to ensure the full coverage of service areas. An ACK-to-PBCH beam scheme may be performed and the WTRU beam-location profile may be obtained <NUM>. Based on the WTRU beam-location profile, the TRP may perform PBCH beam hopping transmission <NUM>. The PBCH may be transmitted in the beams directed to the WTRU according to WTRU beam-location profile. The TRP may then perform inverse HARQ processing <NUM>. The TRP may then retransmit the PBCH beam in response to reception of ACK <NUM>. The same PBCH payload or a different PBCH payload may be transmitted. The TRP may also receive a request from the WTRU for PBCH transmission <NUM> when its beam is idle. In addition, the TRP may receive an ACK-to-request from the WTRU <NUM> in the next PBCH transmission in an active beam. After N transmission cycles, the PBCH may be transmitted again in all beams to ensure the full coverage of service areas for all WTRUs. The entire procedure may then be repeated.

<FIG> is a diagram of a non-claimed example of a first synchronous inverse HARQ method for PBCH transmission <NUM>. A TRP may transmit the PBCH in one or more directions and in one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam <NUM><NUM>, and beam M <NUM>. When WTRUs are present in one or more directions and in one or more beams, the TRP may receive an ACK in those directions, such as for example, <NUM>, <NUM>, <NUM>, <NUM>. In the next PBCH transmission time, the PBCH may be transmitted again in the one or more directions and the one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam <NUM><NUM>, beam M <NUM> to cover the WTRUs from which a response was received indicating their presence for beams. The TRP may also receive an ACK in those directions <NUM>, <NUM>, <NUM>, <NUM>.

<FIG> is a diagram of a non-claimed example of a second synchronous inverse HARQ method for PBCH transmission <NUM>. A TRP may transmit the PBCH in one or more directions and in one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam <NUM><NUM>, and beam M <NUM>. When WTRUs are present in one or more directions and in one or more beams, the TRP may receive an ACK in those directions, such as for example, <NUM>, <NUM>, <NUM>. In the next PBCH transmission time, the PBCH may be transmitted again in the one or more directions and the one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam M <NUM> to cover the WTRUs from which a response was received indicating their presence for beams. The TRP may also receive an ACK in those directions <NUM>, <NUM>, <NUM>. If there is no WTRU present in beam <NUM><NUM>, the TRP may receive DTX <NUM>. In the next PBCH transmission time, the PBCH may not be transmitted in beam <NUM> due to no WTRU response to PBCH transmission in beam <NUM>.

<FIG> is a diagram of a non-claimed example of a third synchronous inverse HARQ method for PBCH transmission <NUM>. A TRP may transmit the PBCH in one or more directions and in one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam <NUM><NUM>, and beam M <NUM>. When WTRUs are present in one or more directions and in one or more beams, the TRP may receive an ACK in those directions, such as for example, <NUM> and <NUM>. In the next PBCH transmission time, the PBCH may be transmitted again in the one or more directions and the one or more beams: beam <NUM><NUM> and beam M <NUM> to cover the WTRUs from which a response was received indicating their presence for beams. The TRP may also receive an ACK in those directions <NUM> and <NUM>. When no WTRU is present in beam <NUM><NUM> and beam <NUM><NUM>, the TRP may receive DTX for beam <NUM><NUM> and DTX for beam <NUM><NUM>. In the next PBCH transmission time, the PBCH may not be transmitted in beams <NUM> and <NUM> due to no WTRU response to PBCH transmission in those beams. When the WTRU detects transmission PBCH, it may report an ACK to respond to PBCH transmission for the corresponding beam as shown in the example of <FIG>, however, the WTRU may not report ACK to respond to each PBCH transmission for the corresponding beam. For example, depending on ACK periodicity, the WTRU may report an ACK for a Kth PBCH transmission, where K ≥ <NUM> for the beam it resides.

<FIG> is a diagram of a non-claimed first example PBCH ACK transmission with a short periodicity K=<NUM> following PBCH transmissions using beam hopping <NUM>. As shown in the example of <FIG>, for a given WTRU, an ACK <NUM>, <NUM>, <NUM> may be reported for each PBCH transmission <NUM>, <NUM>, <NUM> (i.e., K=<NUM>).

<FIG> is a diagram of a non-claimed second example PBCH ACK transmission with a longer periodicity K=<NUM> following PBCH transmissions using beam hopping <NUM>. As shown in the example of <FIG>, an ACK <NUM>, <NUM> may be reported for alternating PBCH transmissions <NUM>, <NUM>, <NUM> (i.e., K=<NUM>). When the WTRU does not detect a PBCH transmission, it may enter DTX or report a NACK to indicate that the WTRU is not present in this beam-location and/or the PBCH may not need to be transmitted in this beam for this particular WTRU.

A common resource for reporting ACKs across multiple WTRUs may be used. It may occur that more than one WTRU detects a PBCH signal in the same beam. Two or more WTRUs may send ACKs to respond to that beam. Since the TRP or base station may not need to distinguish between WTRUs, a common resource may be sufficient. The ACK resource may use preamble, sequence, time, frequency, and/or payload resources. Other alternatives may also be used, such as a fixed resource in time, frequency, code, sequence, or a preamble. In another example, an energy ON/OFF indication may be used, which may be SR-like or use signal modulation (e.g., BPSK-like or QPSK-like).

The PBCH may be used to indicate the timing index, symbol index, or beam index in a multi-beam based system. This may be implemented using a one or more bits which may be inserted into the PBCH payload or using one or more bits which may be obtained from the reserved bits of the PBCH payload. In an embodiment, an implicit method may be used to indicate the timing index, symbol index, or beam index in a multi-beam based system. A CRC with different masks in the PBCH signal may be used to indicate a particular timing index, symbol index, or beam index in a multi-beam based systems.

<FIG> is a non-claimed example method for indicating the timing index, symbol index, or beam index using a CRC mask via the PBCH <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. Depending on the number of timing, symbol indices or beam indices, a corresponding number of CRC masks may be used. A TRP may generate a PBCH payload <NUM> and then may generate a CRC <NUM>. The TRP may mask the generated CRC with a sequence that is a function of the timing index, symbol index, or beam index <NUM>. The TRP may then concatenate the PBCH payload and the masked CRC with the embedded timing index, symbol index, or beam index <NUM>. In order to indicate N timing, symbol indices, or beam indices, one or more N sequences may be used for CRC masking. For example, a number of sequences (e.g., <NUM> sequences) may be used for CRC masking in a multi-beam system with multiple beams (e.g., <NUM> beams) participating in the beam sweep.

<FIG> is a diagram of a non-claimed example method for a WTRU to obtain a timing index, symbol index, or beam index in a multi-beam system <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a WTRU for exemplary purposes, but it may also be performed by any node operating in a wireless communications system. A WTRU may receive a PBCH signal <NUM>. The WTRU may then decode the PBCH payload including the CRC <NUM>. The WTRU may then de-mask the CRC by a sequence that is a function of timing, symbol index, or beam index <NUM>. After the CRC de-masking, the WTRU may check the CRC and determine a sequence <NUM>. The WTRU may then determine the timing index, symbol index, or beam index from the subframe or the frame boundary based on the determined sequence <NUM>. The WTRU may also determine one or more of a subframe, frame boundary, or timing based on the determined timing index, symbol index, or beam index <NUM>.

<FIG> is a diagram of a non-claimed example method of obtaining preamble configuration information for uplink feedback <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a WTRU for exemplary purposes, but it may also be performed by any node operating in a wireless communications system. A WTRU may receive a PBCH signal that includes encoded preamble configuration information <NUM>. The WTRU may then decode the received PBCH signal <NUM>. The WTRU may then obtain the preamble configuration information from the received and decoded PBCH signal <NUM>. The WTRU may use the configured preambles to transmit ACKs to the TRPs to respond the beam and PBCH transmission <NUM> to enable the TRP to perform beam hopping for subsequent PBCH transmission based on reception of ACK reported from the WTRU <NUM>.

If a WTRU is sedentary for a prolonged period of time, its last location may be known to the TRP or base station, but its precise location may not be known. The TRP or base station may trigger a conditional beam sweep to enable the WTRU to receive the PBCH within a confined sector of its original location. A conditional beam sweep may be used to identify the location of more than one WTRU, or group of WTRUs, within a sector.

<FIG> is a diagram of a non-claimed example of a geographic conditional beam sweep <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. The beam sweep may be confined to a sector which may contain hundreds of beams. In the example of <FIG>, sector <NUM><NUM>, sector <NUM><NUM>, and sector <NUM><NUM> are shown. Within these sectors are beams <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. During an initial acquisition, a conditional beam sweep may be defined by a starting and ending beam index, beam ID, and/or sector identification. A conditional beam sweep, using a quasi-omni composite antenna pattern, may locate a WTRU <NUM> or plurality of WTRUs within specific beams. The conditional beam sweep may be following by a beam hopping procedure as described herein wherein the hops are determined by the previously identified location of the WTRUs. A schedule for a conditional beam sweep and a beam hopping procedure may be defined. A conditional beam sweep may be scheduled semi-periodically. A beam hopping procedure may be initiated by either a full, or a conditional beam sweep procedure.

An ACK may carry additional information in addition to just acknowledging the beam-location of the WTRU. The ACK may indicate or carry information including but not limited to the following: WTRU beam-location; whether PBCH may be transmitted next time based on WTRU request via ACK; and how long PBCH may be transmitted next time.

A next PBCH transmission may be requested after L time intervals of PBCH transmission for a given beam. A BPSK modulated ACK may carry <NUM> bit to indicate L time intervals of PBCH transmissions. For example, L may be L = {<NUM>, <NUM>} or L = {<NUM>, <NUM>}. Other value sets for L may be possible. A QPSK modulated ACK may carry <NUM> bits to indicate L time intervals of PBCH transmission. For example, L may be L = {<NUM>, <NUM>, <NUM>, <NUM>} or L = {<NUM>, <NUM>, <NUM>, <NUM>}. Other value sets for L may be possible.

<FIG> is a diagram of a non-claimed example for using an ACK to request PBCH transmission <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. In this example, an ACK may be used to request the next PBCH transmission during inverse HARQ processing. A TRP may transmit the PBCH in one or more directions and in one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam <NUM><NUM>, and beam M <NUM>. When WTRUs are present in one or more directions and in one or more beams, the TRP may receive an ACK in those directions, such as for example, <NUM>, <NUM>, <NUM>. In the next PBCH transmission time, the PBCH may be transmitted again in the one or more directions and the one or more beams: beam <NUM><NUM>, beam <NUM><NUM>, beam M <NUM> to cover the WTRUs from which a response was received indicating their presence for beams. The TRP may also receive an ACK in those directions <NUM>, <NUM>, <NUM>. If there is no WTRU present in beam <NUM><NUM>, the TRP may not transmit the PBCH in beam <NUM> in the next PBCH transmission time because no WTRU response to PBCH transmission in beam <NUM> was received in the previous transmission time interval.

The efficient new radio physical broadcasting channel (NR-PBCH) may be used to transmit system information for NR. After detecting a synchronization signal, a WTRU may need to obtain certain system information to access the cell or carrier. For example, the WTRU may need to acquire the system information which may be needed to carry out the random access procedure in order to gain access to the network or system.

The system information may be provided using a broadcast channel or multi-cast channel. In LTE, a MIB is transmitted on the PBCH and a system information block (SIB) is transmitted on the Physical Downlink Shared Channel (PDSCH) scheduled by the Physical Downlink Control Channel (PDCCH). On a standalone NR carrier, system information used for standalone initial access may be transmitted in a MIB and possibly SIB1 as an always-on signal. Other system information such as SIB2 and beyond may be provided on-demand or based on the request by WTRUs during or after random access.

The system information may contain a small portion of the total amount of system information that the WTRU may need. The remaining system information may be provided to the WTRU once it has accessed the network or system by other ways. For example, the remaining system information may be provided to the WTRU by dedicated signaling or WTRU-specific signaling. It may be beneficial to deploy multi-beam based operation for standalone NR carriers to enhance the performance. On the other hand, efficient multi-beam based operation may reduce the overhead due to MIB and/or SIB transmission that employs beam sweeping.

The synchronization signal and the system information for performing a random access procedure may be "always-on" signals in the system or network. These signals may be transmitted whether there is any WTRU in the cell or if not.

System information such as a MIB may be decodable based on one or more predefined identity parameters that are used for generation of a synchronization signal. The one or more predefined identity parameters used for generation of a synchronization signal may include a time or frequency resource index in addition to a sequence or a code index. Furthermore, the one or more predefined identity parameters used for generation of synchronization signal may also include a spatial or beam resource index. For example, the synchronization signal and/or MIB may be allocated in frequency location within a NR carrier bandwidth and the WTRU may identify the resource location of the MIB based on the resource location of the detected synchronization signal. The identity parameter or parameters for the synchronization signal and/or MIB may include but are not limited to broadcast ID, synchronization ID, MIB ID, SYNC ID, cell ID, sector ID, or beam ID. Identity parameter or parameters that are used for synchronization signal generation and PBCH signal transmission may not limit deployment flexibility for NR.

The transmission of always-on signals may be minimized. The synchronization signals for initial access may be an always-on signal. In order to provide forward compatibility and reduce energy consumption, the synchronization signal period in NR may be designed to be significantly larger than the periodicity of PSS/SSS in LTE or LTE-A. For example, a larger periodicity (e.g., <NUM>) may be used. This may be similar to the periodicity of discovery reference signals that were introduced in LTE Rel-<NUM>. A WTRU may need to search longer on each frequency due to increased periodicity. By reducing the number of frequencies that the WTRU may search for, the total complexity and search times may be maintained similar or the same. Initial access may be performed by the WTRU with some prior knowledge of available carriers.

System information may include the information used for initial access, such as configuration of random access preamble, signal, resource, beam or the like. System information may be broadcast to an entire cell using different methods. System information transmission may be scheduled by dynamic signaling (e.g., using a L1/<NUM> control channel) or by semi-static signaling (e.g., by the first SIB). System information may be transmitted alone, without associated signaling, or based on a predefined association. System information may be split into several parts with separate optimized transmissions. Different transmission methods may be designed and used for each part of system information. Dynamic TDD operation may be considered for system information delivery. The MIB may be transmitted on predetermined DL resources together with synchronization signal for a standalone NR carrier.

Performance enhancements may be provided by a NR PBCH transmission structure that employs a polar encoding scheme of the system information on the PBCH. When the payload size is small, a polar encoding scheme provides better gain. The dB gain from polar encoding may accommodate additional bits. These additional bits may be used for additional random access (RACH) configuration or system information delivery (e.g., indication of TX/RX reciprocity, indication of beam operation modes such as single/multi-beam operation, etc.). Polarization may be optimized for PBCH transmission.

The contents of at least part of the SFN and CRC bits may be encoded together with other configuration information for the NR PBCH. These messages may be encoded by a polar code with a very low code rate. Instead of using repetition on top of a mother code rate of <NUM>/<NUM> TBCC code as in LTE, a mother code rate of, for example, a <NUM>/<NUM> polar code may be applied. This direct design of a low code rate polar code may achieve better performance as the codeword length is larger.

<FIG> is a diagram of an example method of incorporating system information into the PBCH using polar encoding <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. In the example of <FIG>, performance gains may be achieved when transmitting system information using polar encoding. As described above, a PBCH transport block with essential system information <NUM> may be attached with CRC bits <NUM>. The PBCH payload and CRC may then be encoded using a polar encoder <NUM>. A rate match (RM) <NUM> may be performed for the coded bits which are scrambled <NUM> by a scramble code and then modulated <NUM>. Antenna mapping, beamforming and virtualization <NUM> may then be performed. De-multiplexing and subframe mapping <NUM> may then be performed to generate essential system information coded bits <NUM>.

<FIG> is a diagram of an example method of incorporating system information into the PBCH using joint polar transformation encoding and rate matching <NUM> in accordance with one example, which may be used in combination with any of the examples described herein. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> may be performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. A PBCH transport block with essential system information <NUM> may be attached with CRC bits <NUM>. The PBCH payload and CRC bits may then be encoded using a joint polar encoder and rate matching <NUM>. The coded bits after joint coding/RM may be scrambled <NUM> by a scramble code and then modulated <NUM>. Antenna mapping, beamforming and virtualization <NUM> may then be performed. De-multiplexing and subframe mapping may then be performed <NUM> to generate essential system information coded bits <NUM>.

Extra performance gains may be achieved as illustrated in the examples described above, and as a result it may be possible to insert more bits into the payload of PBCH while still maintaining similar performance as a traditional PBCH at the same code rate. For example, a slightly higher code rate may be used for the proposed polar code based PBCH to accommodate an additional two bits. The original PBCH may have <NUM> bits. With attachment of a <NUM>-bit CRC, the payload size of the PBCH may be <NUM> bits in total.

In another example, an additional one or two bits may be included to make the payload <NUM> or <NUM> bits, which may include some additional reserved bits. For example, the information bit size may be <NUM> or <NUM> bits. A <NUM>-bit CRC may also still be used. Since the code rate may be increased, <NUM> or <NUM> bits, plus some reserved bits, may still be accommodated by the same resources of the PBCH without sacrificing performance due to extra gain achieved by using polar encoding. The additional <NUM> or <NUM> bits in this example may be used to indicate the beam sweeping configurations.

Various beam sweep configurations may be used. In a first configuration, base station RX beams may be swept first for each given WTRU TX beam i, for i=<NUM>,<NUM>,. Nbase_station_RX.

In a second configuration, WTRU TX beams may be swept first for each given base station RX beam j, for j=<NUM>,<NUM>,.

The control field may be defined as "beam sweep indicator" or Beam_Sweep_IND. If Beam_Sweep_IND = <NUM>, the first configuration may be indicated. If Beam_Sweep_IND = <NUM>, the second configuration may be indicated. If the beam mode is not found in SYNC, or a single beam is used for SYNC while multi-beam mode is used after SYNC, the PBCH may need to indicate such information to the WTRU.

<FIG> is a diagram of an example LTE PBCH coding procedure <NUM>. The contents of the MIB may include but are not limited to the following: <NUM>-bit system bandwidth information <NUM>, <NUM>-bit PHICH configuration information <NUM>, and an <NUM>-bit SFN <NUM>. These <NUM> source bits, together with <NUM> reserved bits <NUM> may be concatenated to <NUM> bits <NUM>, which may be appended by the <NUM>-bit CRC <NUM>. The resulting <NUM> bits may be encoded by rate <NUM>/<NUM> tail-biting convolutional coding (TBCC) <NUM>. The output of the TBCC (<NUM> bits) may then be rate matched to <NUM> bits via repetition <NUM>. These <NUM> bits may then be segmented to <NUM> equal-sized individually self-decodable units <NUM>, each unit assigned to the PBCH channel of a radio frame.

<FIG> is a diagram of an NR PBCH coding method <NUM> in accordance with the invention. Because polar codes may demonstrate performance advantages over TBCC codes, the example of <FIG> uses polar codes to encode the MIB message. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> is performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. As shown in <FIG>, a TRP generates a concatenated MIB transport block that includes information bits associated with extended content comprising SFN <NUM> and which might comprise information such as system bandwidth information <NUM>, timing information <NUM>, beam sweeping configuration <NUM>, and control resource set (CORESET) and other system information <NUM>. There may be reserved bits <NUM> in the concatenated MIB as well. The TRP attaches CRC bits, such as at least <NUM> CRC bits <NUM> to the concatenated MIB <NUM>. The CRC bits <NUM> may be generated by cyclic generator polynomials, for example: <MAT> Other cyclic generator polynomials may also be used. The CRC bits <NUM> may be appended to the information bits (system bandwidth information <NUM>, timing information <NUM>, SFN <NUM>, beam sweeping configuration <NUM>, and control resource set (CORESET) and other system information <NUM>), or they may be put in different relative locations to the information bits.

As described above, the number of CRC bits <NUM> may be more than <NUM> bits. Some of the CRC bits may be used for data detection, while the additional CRC bits may be used for error correction such as in a CRC-aided successive cancellation list (CA-SCL) or CRC-aided successive cancellation stack (CA-SCS) decoding schemes or decoders. Furthermore, the additional CRC bits may be added jointly to the original CRC or separately for error detection. If a parity check (PC) polar code is used to encode the NR-PBCH payload, the number of CRC bits <NUM> may be equal to <NUM> bits.

The TRP prioritizes the concatenated MIB <NUM> and the at least <NUM> CRC bits <NUM> based on their content <NUM> such that bits associated with more important information are placed at the beginning of the concatenated MIB <NUM> and CRC bits <NUM> and bits associated with less important information are placed at the end of MIB <NUM> and CRC bits <NUM>. This process is aimed to make use of the polarization feature of polar codes so that the more important bits are sent through more reliable bit channels.

For example, when performing content-based prioritization, timing information may be critical and therefore more important than other information in the MIB. As a result, timing information <NUM> may be placed at the beginning of the concatenated MIB <NUM> and CRC bits <NUM>.

The TRP may then perform channel coding of the prioritized concatenated MIB and the at least <NUM> CRC bits using a polar encoder with a very low coding rate <NUM>. According to the invention, a rate less than <NUM>/<NUM> is used. Since polar codes are flexible on their information input bits, the coding rate of polar code may not be restricted to certain values. Unlike a TBCC code, which may have a fixed rate of <NUM>/<NUM>, a lower coding rate may be used when performing channel coding of the prioritized bits. Furthermore, this may be done at no additional cost. In LTE, rate <NUM>/<NUM> TBCC code may be used followed by repetition to achieve an effectively low coding rate. However, in NR a polar code may be directly used with a much lower coding rate while avoiding the repetition operations. The direct usage of a low coding rate polar code may provide an improved coding gain. The codeword length of the polar code may be a power of <NUM>.

The generator matrix of the polar code may be expressed by, for example: <MAT> where BN is the bit-reversal permutation matrix, F⊗n denotes the n-th Kronecker power of matrix F and <MAT>.

Polar encoding may be written as:
where XN is coded bits, and uN is the input bits. Both may be N-bits sequences. It should be noted that the information bits plus the CRC bits may be K<N bits. The mapping of the K bits to N bits may follow different ways, and the remaining N - K bits in uN may be frozen bits, which are constant (either <NUM> or <NUM>).

The polar code may also be configured without the bit reversing at the encoder: <MAT>.

In this configuration, the order of input may be changed when it is compared with the inclusion of the bit reversing matrix.

The TRP then performs rate matching on the polar coded bits <NUM> such as for example via repetition. The output bits of the rate matching block are assigned to the PBCH of a radio frame for transmission, and the same PBCH data may also be transmitted in the PBCHs of consecutively transmitted radio frames <NUM>.

<FIG> is a diagram of an NR PBCH coding method <NUM> in accordance with another example, which may be used in combination with any of the examples described herein. As in the above example, polar codes are also used to encode the MIB message in the example of <FIG>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> is performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. In the example of <FIG>, a TRP may generate a concatenated MIB transport block that includes information bits associated with extended content comprising SFN <NUM>, and which might comprise information such as system bandwidth information <NUM>, PHICH configuration information <NUM>, beam sweeping configuration <NUM>, and RACH configuration and other system information <NUM>. There may be reserved bits <NUM> in the MIB as well. The TRP may then attach at least <NUM> CRC bits <NUM> to concatenated MIB <NUM>. The CRC bits <NUM> may be generated by cyclic generator polynomials using, for example, Equation (<NUM>) above. Other cyclic generator polynomials may also be used. The CRC bits <NUM> may be appended to the information bits (system bandwidth information <NUM>, PHICH configuration information <NUM>, SFN <NUM>, beam sweeping configuration <NUM>, and RACH configuration and other system information <NUM>), or they may be put in different relative locations to the information bits.

As described above, for polar encoding of the NR-PBCH payload, the number of CRC bits <NUM> may be more than <NUM> bits. Furthermore, if a PC polar code is used to encode the NR-PBCH payload, the number of CRC bits <NUM> may be equal to <NUM> bits.

The TRP prioritizes <NUM> the concatenated MIB <NUM> and the at least <NUM> CRC bits <NUM> based on various criteria such as content as described above, which results in the bits associated with more important information are placed at the beginning of the concatenated MIB <NUM> and CRC bits <NUM> and bits associated with less important information are placed at the end of MIB <NUM> and CRC bits <NUM>. This process is aimed to make use of the polarization feature of polar codes so that the more important bits are sent through more reliable bit channels.

The TRP may then perform channel coding of the prioritized concatenated MIB and the at least <NUM> CRC bits using a polar encoder with a very low coding rate <NUM>. As described above, polar codes are flexible on their information input bits, the coding rate of polar code may not be restricted to certain values and a much lower coding rate may be used for polar codes. The codeword length of the polar code may be a power of <NUM>. The generator matrix of the polar code may be expressed by Equation (<NUM>) above. Polar encoding may be expressed by Equation (<NUM>) above. The polar code may also be configured without the bit reversing at the encoder as expressed by Equation (<NUM>) above. In this configuration, the order of input may be changed when it is compared with the inclusion of the bit reversing matrix.

The TRP may then perform a puncturing <NUM> operation on the coded bits to fit the given resource blocks for the PBCH. The output of the puncturing block may be a bit sequence of arbitrary length. The TRP may then fit the output of the puncturing block in the PBCH of a radio frame for transmission, and same PBCH data may also be transmitted in the PBCHs of consecutively transmitted radio frames <NUM>.

<FIG> is a diagram an example NR PBCH coding procedure <NUM> in accordance with yet another example, which may be used in combination with any of the examples described herein. As in the above examples, polar codes are also used to encode the MIB message in the example of <FIG>. While each step of the method <NUM> in <FIG> is shown and described separately, multiple steps may be executed in a different order than what is shown, in parallel with each other, or concurrently with each other. The method of <FIG> is performed by a TRP for exemplary purposes, but it may also be performed by any node operating in a wireless communications system such as base stations 114a or 114b as defined above. It should be noted that deep puncturing may severely degrade the performance of polar codes. To improve the coding performance, the example of <FIG> uses an alternative rate matching scheme.

Referring to <FIG>, a TRP may generate a concatenated MIB transport block that includes information bits associated with extended content such as system bandwidth information <NUM>, PHICH configuration information <NUM>, SFN <NUM>, beam sweeping configuration <NUM>, and RACH configuration and other system information <NUM>. There may be reserved bits <NUM> in the MIB as well. The TRP may then attach at least CRC bits <NUM> to concatenated MIB <NUM>. The CRC bits <NUM> may be generated by cyclic generator polynomials using, for example, Equation (<NUM>) above. Other cyclic generator polynomials may also be used. The CRC bits <NUM> may be appended to the information bits (system bandwidth information <NUM>, PHICH configuration information <NUM>, SFN <NUM>, beam sweeping configuration <NUM>, and RACH configuration and other system information <NUM>), or they may be put in different relative locations to the information bits.

In the example of <FIG>, instead of using a single polar code as in previous examples, the TRP may use multiple polar codes with different lengths. The TRP may prioritize the concatenated MIB <NUM> and CRC bits <NUM> to the multiple polar code blocks <NUM> based on various criteria such as content as described in the previous examples above. For example, L polar codes by polar encoders <NUM>, <NUM>, and <NUM> may be used, and the i-th polar code may have a codeword length <NUM>ni, <NUM> ≤ i ≤ L. The selection of L and n<NUM>,. , nL may depend on the coded block length of the PBCH in each radio frame. For example, X resource elements may be allocated for the PBCH in each radio frame and QPSK modulation may be used. The coded block length of the PBCH may be 2X bits. In a conventional LTE system, the coded block length of PBCH may be <NUM> bits. Hence, <NUM> polar codes may be selected with respective codeword lengths of <NUM> bits, <NUM> bits, <NUM> bits and <NUM> bits.

The prioritized mapping to multiple polar code blocks <NUM> may be considered as a matrix production operation. For example, the input to this block may be a vector A of t bits. The output of this block may be <MAT>, which may match the L polar codes of lengths n<NUM>,. Here, the design of this block may be a matrix W of size <MAT>. The output may be calculated as A · W in a GF(<NUM>) field. The design of the matrix W may also consider the importance of the input bits. The first n<NUM> bits of the outputs may be encoded by polar code <NUM> with length n<NUM>, the next n<NUM> bits of the outputs may be encoded by polar code <NUM> with length n<NUM>, etc..

The outputs of these L polar codes may be concatenated <NUM>. These concatenated bits may be further scrambled and modulated to fit in a PBCH of a radio frame for transmission, and the same PBCH data may also be transmitted in the PBCHs of consecutively transmitted radio frames <NUM>.

<FIG> is a diagram of an example of PBCH polar encoding with an implicit synchronization signal (SS) block index <NUM> in accordance with an example, which may be used in combination with any of the examples described herein. The NR-PBCH may be transmitted and multiplexed together with PSS and SSS signals within a SS block. The SS block index may be contained in NR-PBCH. When using polar codes, the SS block index may be implicitly indicated by NR-PBCH, via operations on the polar codes. Referring to <FIG>, the SS block index may be implicitly encoded via polar codes by putting the SS block index <NUM> as frozen bits in polar codes. For example, there may be four SS block indices, denoted by two bits, <NUM>, <NUM>, <NUM>, or <NUM>. These two bits may be placed in the locations of the two most reliable frozen bits. A TRP may encode the NR PBCH payload together with the SS block index bits and CRC bits as information bits. This may imply that the SS block index is explicitly contained in NR-PBCH.

Alternatively, the SS block index may be placed in the locations of frozen bits which may not be encoded as information bits. Instead, The WTRU may perform the blind detection using the four possible values of <NUM>, <NUM>, <NUM>, or <NUM> for frozen bits. The WTRU may perform the polar decoding using four possible fixed frozen bit values of <NUM>, <NUM>, <NUM>, or <NUM>. Only the proper values on the frozen bits may result in the correct decoding at the WTRU side. The SS block index may be implicitly detected together with the NR PBCH message. The SS block index may also be XOR-ed or scrambled by a cell ID, or part of a cell ID, to reduce the false alarm rate.

The example of <FIG> shows that the NR-PBCH may also include another frozen set of all zero <NUM> before the SS block index <NUM> frozen set and PBCH payload and CRC <NUM>.

A similar approach may be used on PC polar codes. Here, the SS block index may be placed in the locations of a frozen set or PC-frozen sets. <FIG> is a diagram of PBCH PC polar encoding with an implicit SS block index in frozen bits <NUM> in accordance with an example, which may be used in combination with any of the examples described herein. The example of <FIG> shows that the NR-PBCH may also include another frozen set of all zero <NUM> before the SS block index <NUM> frozen set, PC frozen sets <NUM>, and PBCH payload and CRC <NUM>.

<FIG> is a diagram of an example of PBCH PC polar encoding with a SS block index in PC frozen bits <NUM> in accordance with an example, which may be used in combination with any of the examples described herein. The example of <FIG> shows that the NR-PBCH may also include another frozen set of all zero <NUM> before the PC frozen set XOR-ed with the SS Block index <NUM> and PBCH payload and CRC <NUM>.

<FIG> is a non-claimed example of WTRU communication with two TRPs <NUM>. TRP1 <NUM> may be, for example, a macro cell or gNB. TRP2 <NUM> may be, for example, a small cell that may be within the coverage area of TRP1 <NUM>. There may be an ideal backhaul (e.g., zero delay communication) or a non-ideal backhaul <NUM> between the TRP1 <NUM> and TRP2 <NUM>. TRP1 <NUM> may be used to assist WTRU <NUM> with one or more procedures, such as cell search, TRP selection, and/or beam selection, with or for a TRP2 <NUM>. Assistance information, data, and/or parameters that a TRP may provide to a WTRU and/or that may be used by a WTRU may be referred to as WTRU-assistance data. Assistance information, data and/or parameters that a TRP may provide to another TRP and/or that may be used by another TRP may be referred to as TRP-assistance data.

TRP1 <NUM> may be considered a primary TRP, or an anchor TRP. TRP2 <NUM> may be considered a secondary TRP, or a non-anchor TRP. Communication with the TRP1 <NUM> and TRP2 <NUM> may be with the same or different radio access technology (RAT). TRP1 <NUM> and TRP2 <NUM> may also be co-located, or a gNB and TRP2 may be co-located and the gNB may be an anchor cell. TRP1 <NUM> may or may also provide assistance to TRP2 <NUM>, for example, to enable TRP2 <NUM> to transmit at least some of its signals (e.g., sync, reference, etc.) more efficiently.

WTRU <NUM> may be in communication with the TRP1 <NUM>, which may transmit assistance data to WTRU <NUM> for one or more other TRPs. WTRU <NUM> may receive assistance information from TRP1 <NUM>. The assistance data may enable WTRU <NUM> to synchronize with and/or receive one or more signals, channels, and/or data from TRP2 <NUM>. The one or more signals may include a synchronization signal, broadcast signal, reference signal, or the like. The one or more channels may include a control channel, a data channel, and/or a broadcast channel. Data may be user data or system information. It should be noted that the terms information and data may be used interchangeably herein.

A first synchronization step may comprise at least synchronization with NR-PSS. A second synchronization step may comprise at least synchronization with NR-SSS. Assistance data may refer to WTRU-assistance data and/or TRP-assistance data.

The assistance data, for example from a first TRP, may include at least one of the following parameters for a second TRP:.

At least some assistance data may be provided to both a WTRU and TRP2 so that TRP2 and the WTRU may have common knowledge. Beam sweep information may be for a sync signal, a reference signal, a broadcast channel, a control channel, and/or a random access channel, among others.

A WTRU may use the assistance data from TRP1 to do at least one of the following actions:.

Numerology may include at least one of subcarrier spacing, cyclic prefix, and/or a symbol duration.

A second TRP that receives TRP-assistance data from a first TRP may transmit one or more signals (e.g., synchronization signals, reference signals, control channels, and/or data channels) in accordance with the TRP-assistance data. A second TRP that receives TRP-assistance data from a first TRP may use a beam sweeping procedure indicated by the first TRP.

A WTRU may measure a RS that may be associated with a beam. The WTRU may measure, for example for TRP2, a set of RS where each RS may be associated with an ID, an index, and/or a beam. The WTRU may determine a best or preferred RS, index, and/or beam, for example for TRP2. It should be noted that the terms beam, index, Id, and RS may be substituted for each other in the examples and embodiments described herein and still be consistent.

A WTRU may determine, transmit and/or report (e.g., transmit a report containing) information regarding TRP2 (e.g., TRP2-information) to TRP1. The TRP2-information may comprise at least one of the following:.

The TRP2-information may be associated with a common channel or a WTRU-specific channel. A common channel may be a sync channel, a broadcast channel, and/or a control channel. A WTRU-specific channel may be a data channel. The WTRU may send a report indicating a first RS or a first beam that may correspond to a preferred beam for a common channel. The WTRU may send a report indicating a second RS or a second beam that may correspond to a preferred beam for a WTRU-specific channel. The first and second RS or beam may be the same or different.

TRP1 may determine WTRU-assistance data and/or TRP-assistance data based on TRP2-information it receives from the WTRU. The WTRU-assistance data and/or TRP-assistance data may include at least a subset of TRP2-information.

TRP1 may indicate to a WTRU to receive a channel from TRP2. This may be based on the TRP2-information and/or based on the WTRU-assistance data it provides to the WTRU. TRP1 may indicate a beam on which to receive a channel from TRP2. The beam may be different from a preferred one indicated by the WTRU in TRP2-information.

The WTRU may receive a channel from TRP2 based on the TRP2-information it determined and/or transmitted. The WTRU may receive a channel from TRP2 based on information (e.g., revised TRP2-information) received from TRP1. The WTRU may receive a channel from TRP2 based on the WTRU-assistance data received from TRP1.

The WTRU may transmit TRP2-information to TRP1 in at least one of the following ways: RRC signaling, MAC signaling, such as in a MAC Control element (MAC-CE), or in the physical layer.

The WTRU may provide TRP-<NUM> information in UL control information (UCI) or via an UL control channel. The UCI format or control channel may be such that the resources used may indicate a beam or set of beams. The UCI or control channel may be such that one or more bits may be used to represent a beam or set of beams.

TRP1 may trigger the WTRU to perform an UL procedure with TRP2, such as a random access procedure or a beam pairing procedure. TRP1 may indicate to the WTRU on which set of beams it is to transmit and the timing associated with the beams (e.g., each of the beams in the set).

TRP1 may indicate a set of reference signals that the WTRU may transmit where an RS may be associated with a beam. TRP1 may indicate the timing and/or resources for transmission of an RS. The trigger may be provided via a DL control channel or DCI that may be provided by TRP1 and/or received by the WTRU. In response to the trigger, the WTRU may transmit to TRP2 on resources associated with one or more beams. The WTRU may transmit an indicated reference signal that may be associated with a beam according to the timing associated with the RS or beam. The association may be configured, for example, by TRP1.

<FIG> is a non-claimed example of an initial access procedure with a combination of hierarchical synchronization and beam-centric designs <NUM>. The hierarchical beam-based initial synchronization procedure may include multiple steps, where subsequent steps may use different beams or a different beam sweep method or procedure. Procedures that may be used include forward hierarchical beam sweeping using successively narrower beams, or backward hierarchical beam sweeping using successively wider beams. An initial synchronization step may include at least one of: synchronization, receiving and/or measuring a reference signal (e.g., beam reference signal (BRS)), receiving a channel such as a broadcast channel (e.g., PBCH) and/or a control channel, and/or reporting at least one measurement or a beam (e.g., a preferred beam or set of beams).

Referring to <FIG>, TRP1 may send WTRU-assistance data and/or trigger the WTRU to perform a hierarchical beam-based initial synchronization procedure with TRP2 <NUM>. The WTRU-assistance data may be for one or more of the synchronization steps, such as the first synchronization step. The WTRU may receive the WTRU-assistance data and/or trigger from TRP1 for the first synchronization step with TRP2 (e.g. with wide beams) <NUM>. The WTRU may perform the synchronization step with TRP2 based on the WTRU-assistance data <NUM>. The WTRU may then send a report to TRP1, which may include for example measurements or a best beam <NUM>. TRP1 may then receive the report <NUM>, and then may provide TRP-assistance data to TRP2 and/or determine WTRU-assistance data for the second synchronization step <NUM>, which may for example be based on the report. The TRP-assistance data may include one or more parameters that may enable TRP2 to perform a beam sweep (e.g., an efficient beam sweep) for the transmission and/or reception of cell-specific, beam-specific, and/or WTRU-specific signals.

TRP1 may then send WTRU-assistance data and/or trigger the WTRU to perform a second synchronization step with TRP2 <NUM>. The WTRU may receive the WTRU-assistance data and/or trigger from TRP1 for the second synchronization step with TRP2 (e.g. with narrower beams) <NUM>. The WTRU may then send a report to TRP1, which may include for example measurements or a best beam <NUM>. TRP1 may then receive the report <NUM>, and then may provide TRP-assistance data to TRP2 and/or determine WTRU-assistance data for a random access procedure <NUM>, which may for example be based on the report. TRP1 may then send WTRU-assistance data and/or trigger the WTRU to perform a random access procedure with TRP2 <NUM>. The WTRU may receive the WTRU-assistance data and/or trigger from TRP1 for the random access procedure with TRP2 <NUM>. The WTRU may then perform the random access procedure with TRP2 based on the WTRU-assistance data <NUM>.

<FIG> is a non-claimed example of an initial access procedure with joint designs for hierarchical SS (1st step NR-PSS and 2nd step NR-SSS) and hierarchical beam-centric designs (1st stage and 2nd stage) <NUM>. TRP1 may send assistance data and/or trigger the WTRU to perform a cell search first step with TRP2 <NUM>. The WTRU may receive the assistance data and/or trigger from TRP1 for the cell search first step with TRP2 (e.g. with wide beams) <NUM>. The WTRU may perform the first step (e.g., NR-PSS) with TRP2 based on the assistance data <NUM>. The WTRU may then send a report to TRP1, which may include for example measurements or a best beam <NUM>. TRP1 may then receive the report <NUM>, and then may provide report information to TRP2 and/or determine assistance data for the second step <NUM>. TRP1 may then send assistance data and/or trigger the WTRU to perform a cell search second step with TRP2 <NUM>. The WTRU may receive the assistance data and/or trigger from TRP1 for the cell search second step with TRP2 (e.g. with narrower beams) <NUM>. The WTRU may then send a report to TRP1, which may include for example measurements or a best beam <NUM>. TRP1 may then receive the report <NUM>, and then may provide report information to TRP2 and/or determine assistance data for a random access procedure <NUM>. TRP1 may then send assistance data and/or trigger the WTRU for broadcast channel or random access with TRP2 <NUM>. The WTRU may receive the assistance data and/or trigger from TRP1 for the random access procedure with TRP2 <NUM>. The WTRU may then perform the random access procedure with TRP2 based on the assistance data <NUM>.

Claim 1:
A method for use in a base station, the method comprising:
performing channel coding of a plurality of bits to produce coded bits using polar encoding, wherein the polar encoding provides the plurality of bits to bit channels based on content of each of the plurality of bits and based on a reliability of the bit channels, wherein the plurality of bits at least includes bits of a master information block, MIB, transport block and cyclic redundancy check, CRC, bits, wherein the MIB transport block comprises system information bits and indicates a system frame number, SFN, wherein more important bits of the MIB transport block and the CRC bits are provided to more reliable bit channels, and wherein a coding rate associated with the channel coding is less than <NUM>/<NUM>;
performing rate matching on the coded bits; and
sending the rate matched coded bits in a physical broadcast channel, PBCH, transmission.