Patent Description:
As carrier frequency increases, severe path loss can be experienced and may limit coverage. Transmission in millimeter wave systems may also suffer from non-line-of-sight losses such as diffraction loss, penetration loss, oxygen absorption loss, foliage loss or the like. During initial access, a base station and wireless transmit/receive units (WTRUs) may need to overcome these high path losses and discover each other. Further prior art can be found in:.

Methods and an apparatus for performing synchronization in New Radio (NR) systems are disclosed. Independent claim <NUM> defines a UE, independent claim <NUM> defines a corresponding method, independent claim <NUM> defines a corresponding gNB and independent claim <NUM> defines a corresponding method for the gNB.

The full duplex radio may include an interference management unit <NUM> to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor <NUM>). 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 downlink (e.g., for reception)).

In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated MultiPoint (CoMP) technology.

In view of <FIG>, and the corresponding description of <FIG>, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME <NUM>, SGW <NUM>, PGW <NUM>, gNB 180a-c, AMF 182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and/or any other device(s) described herein, may be performed by one or more emulation devices (not shown).

LTE initial synchronization utilizes a cell search procedure where a WTRU acquires time and frequency synchronization with a cell and detects the Cell ID of that cell. The LTE synchronization signals are transmitted in the <NUM>th and <NUM>th subframes of every radio frame and are used for time and frequency synchronization during initialization. A WTRU may synchronize sequentially to the OFDM symbol, slot, subframe, half-frame, and radio frame based on the synchronization signals. The two synchronization signals are the Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS). The PSS may be used to obtain slot, subframe and half-frame boundary. It may also provide physical layer cell identity (PCI) within the cell identity group. The SSS may be used to obtain the radio frame boundary. It also enables the UE to determine the cell identity group, which may range from <NUM> to <NUM>. Following a successful synchronization and PCI acquisition, the WTRU may decode the Physical Broadcast Channel (PBCH) with the help of cell specific reference signals (CRS) and acquire the master information block (MIB) information regarding system bandwidth, System Frame Number (SFN) and PHICH configuration. LTE synchronization signals and PBCH may be transmitted continuously according to a standardized periodicity.

In an LTE system, a single beam is used for initial access. In a New Radio (NR) system, a synchronization signal burst (SS burst) may be used when multiple beams are used for initial access and where the SS burst may be transmitted periodically such as, for example, approximately every <NUM>, and each SS burst may include one or more SSB. One or more SSBs in a SS burst may be associated with one or more beams and the number of SSBs in a SS burst may be determined by a gNB based on the number of beams used at the gNB. As an example, if N beams are used at a gNB, N SSBs may be used or transmitted in a SS burst. Each SSB may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a PBCH (physical broadcasting channel). <FIG> shows an example of synchronization signal (SS) burst with x ms cycle and multiple SSBs in SS bursts <NUM>. As shown in <FIG>, each SS burst <NUM> may include SSBs <NUM> labled <NUM> through N which may be cycled every x ms and may each comprise a PSS <NUM>, a SS <NUM>, and a PCBH <NUM> component. As shown, the X axis indicates time and the Y axis indicated frequency.

In NR systems, synchronization signals (SS) may be used to achieve time synchronization between a gNB and a wireless transmit/receive unit (WTRU). More particularly, a WTRU may need to know the SSB information including a block index time indication to be used to decode such block information and for time synchronization. Further, some SSBs may be used to transmit synchronization signals while other SSBs may not be used to transmit synchronization signals. This may be partly due to antenna and beam configurations at gNB or Tx/RX points (TRP). Accordingly, techniques to obtain SSB index time indication and to reuse or use the unused SSBs are needed. Additionally, used SSBs may serve as reference points for a WTRU to perform more precise measurement. Access to unused SSB information may allow a WTRU to obtain or determine used SSB information. Accordingly, a WTRU may use the known reference timing points for measurement purposes.

In accordance with the subject matter disclosed herein, a WTRU may know SSB information including time indication to acquire time synchronization between gNB/TRP and the WTRU. Further, SSBs may carry an index, which may be used for time indication for a WTRU to acquire time synchronization. The index may be indicated to the WTRU to support more precise measurement as well as to increase system efficiency and throughput. In accordance with the subject matter disclosed herein, the proposed solutions may also be used for acquiring time synchronization or SSB information between devices such as, for example, gNBs, between TRPs and between gNB and TRP.

Efficient techniques for determining SSB presence, SSB index, and half radio frame (HRF) timing are shown in <FIG>. These techniques may be employed by any applicable component such as, for example, a processor internal or external to a WTRU. At <NUM>, a WTRU configuration may be detected and, at <NUM>, a determination may be made regarding whether the frequency band associated with the WTRU configuration detected at <NUM> is equal to, greater than or less than a threshold frequency band. As a non-limiting example, the threshold frequency band may be <NUM> and a determination regarding whether the frequency band for a detected SSB is greater than (or equal to) or less than <NUM> may be made at <NUM>.

If the frequency band for an SSB is determined to be below the threshold frequency band, as shown at <NUM>, an SSB index may be determined implicitly from a PBCH demodulation reference signal (DMRS) sequence. Alternatively, if the frequency band for an SSB is determined to be above or equal to a threshold frequency band, as shown at <NUM>, a portion of an SSB index may be determined implicitly from a PBCH DMRS sequence and the rest of the SSB index may be determined explicitly from a PBCH payload. An SSB index determined implicitly may be determined based on the energy levels or correlation levels of a signal such that bits in the SSB index may correspond to energy levels or correlation levels of a signal exceeding an energy or correlation threshold. A correlator may be employed to determine the energy level or correlation level. It will be understood that other techniques or thresholds may be used to detect the bits in an SSB index.

As shown at <NUM>, HRF timing may be determined based on either the implicit SSB index determination of <NUM> or the partial implicit and partial explicit determination of the SSB index of <NUM>.

At <NUM>, a configuration of transmitted SSBs may be received via any applicable manner such as via a multi-level two stage compressed indication. In a multi-level two stage compressed indication, as shown at <NUM>, the configuration may include a first indicator which may contain information to enable a determination of which SSB groups are transmitted. The first indicator at <NUM> may be a coarse indicator that provides a Group-Bitmap to enable determination of which SSB groups are transmitted. As shown at <NUM>, the configuration may include a second indicator that may contain information to enable a determination of SS/PBCH blocks are transmitted within an SS group. The second indicator at <NUM> may be a fine indicator that provides a Bitmap in Group to enable determination of which SS/PBCH blocks are transmitted within an SSB group, e.g., within a transmitted SSB group.

At <NUM>, one or more actually transmitted SSBs may be monitored. The one or more actually transmitted SSBs may correspond to the SSBs for which the configuration is received at <NUM>.

<FIG> shows an example diagram for determining SSB presence, index, and HRF for a SSB with a frequency band that is greater than or equal to a threshold frequency band, as disclosed herein. As noted in <FIG>, a portion of the SSB block may be determined implicitly and a portion may be determined explicitly for SSBs with a frequency band greater than a threshold frequency band. As shown in <FIG>, a signal with a PBCH may be received at <NUM> and a determination may be made that a characteristic of the signal, such as a frequency band, is greater than or equal to a threshold, such as a frequency threshold. Based on the determination, a hybrid technique for SSB index indication may be applied such that, at <NUM> an implicit determination is made and at <NUM> an explicit determination is made. At <NUM>, a portion <NUM> of the SSB index may be indicated based on PBCH DMRS detection. Additionally, a half radio frame indicator <NUM> may also be indicated based on PBCH DMRS detection. At <NUM>, a portion <NUM> of the SSB index may be indicated based on PBCH payload decoding. Additionally, a half radio frame indicator <NUM> may also be indicated based on PBCH payload decoding.

At <NUM>, the half radio frame indicator <NUM> indicated via the explicit PBCH decoding at <NUM> may be compared to the half radio frame indicator <NUM> indicated via the implicit PBCH DMRS detection at <NUM>. A match of the two half radio frame indicators <NUM> and <NUM> may result in the determination and/or confirmation of the half radio frame indicator h0 <NUM>.

The portion <NUM> of the SSB index indicated via the explicit PBCH decoding at <NUM> may be combined with the portion <NUM> of the SSB index indicated via the implicit PBCH DMRS detection at <NUM> at <NUM>. The combining may provide the SSB timing index indicator <NUM> that includes, for example, bits indicated via the PBCH decoding <NUM> and the PBCH DMRS detection <NUM>. Additionally, the PBCH channel and payload may be decoded to obtain other timing information <NUM> such as a system frame numbers.

As disclosed herein, SSB index time indications may be based on frequency bands. A value L may vary based on frequency bands and may denote a maximum number of SSBs in a SS burst set. Higher frequency bands may employ larger number of beams while lower frequency bands may employ smaller number of beams. Accordingly, as an example, a larger L may correspond to a higher frequency band and a smaller L may correspond to a lower frequency band. Further, SSB index time indications, SSB index frequency indications, or combination of SSB index time and frequency indications may be based on frequency bands. It will be understood that the solutions disclosed herein for SSB index indication may be applied to SSB index time and/or frequency indication. As a non-limiting example, an SSB index time and/or frequency indication may be received via a multi-level two stage compressed indication.

According to an embodiment, an SSB index time indication technique may be determined based on a threshold value such that an SSB with a characteristic lower than the threshold value may result in indicating a SSB index using an first method and a characteristic higher than the threshold value may result in indicating n SSB index using a second different method. The threshold value may be a threshold L value and may be an integer value such as, for example, <NUM>. For a given SSB if L < threshold L value, such as L = <NUM>, <NUM> or <NUM>, an SSB index may be indicated using a first method. The first method may include implicit methods which may employ, for example, CRC masking, sequence-based indications, indication using DMRS, scrambling, or the like. According to such implicit methods, L CRC masks or L sequences, L hypotheses, L hypotheses using DMRS, scrambling, etc. may be used. If L > threshold L value, such as L = <NUM>, SSB index may be indicated using another method. For example, an SSB index may be carried in NR-PBCH using explicit methods, implicit methods or combination of explicit and implicit methods such as a hybrid method. It will be understood that an L value may be determined based on the configuration of a WTRU such that, for a given configuration such as a frequency band associated with the WTRU, a corresponding L value may be determined.

SSB index indication may be based on L in a hybrid method such that an implicit SSB index indication is used if L<T where T=<NUM>, L=<NUM> and <NUM> and an explicit SSB index indication is used if L>=T where T=<NUM> and L=<NUM>. SSB index indications may be based on L in another hybrid method such that an implicit SSB index indication is used if L<T where, for example, T=<NUM>, L=<NUM> and <NUM>, and a combination of implicit and explicit SSB index indication is used if L>=T where, for example, T=<NUM> and L=<NUM>.

According to another hybrid method, LSBs for SSB index may be indicated using CRC masking or sequence-based indication, indication using DMRS, scrambling, etc., whereas MSBs for SSB index may be indicated in a payload or signal. For example, K1 bits for LSB may be indicated using PBCH CRC masking or sequence-based indication, indication using DMRS, scrambling, etc., and K2 bits for MSB may be indicated in a PBCH payload or PBCH signal.

A unified hybrid method across different frequency bands for SSB index may be implemented such that a WTRU or any applicable device may perform any one or a combination of receiving a PBCH signal and decoding a PBCH channel, performing CRC demasking or sequence-based detection, detection using DMRS, descrambling, etc., obtaining K1 bits from CRC demasking or sequence-based detection, detection using DMRS, descrambling, etc., and mapping, and/or outputting K1 bits as an SSB index time indication. For higher frequency bands, a WTRU or other applicable device may continue to perform any one or a combination of obtaining K2 bits from control field of the decoded PBCH channel and outputting both K1 and K2 bits as SSB index time indication bits. Here, K1 may be the LSBs for SSB index time indication and K2 may be the MSBs for SSB index time indication.

<FIG> shows an example SSB index time indication employing hybrid CRC masking and control field. As shown, at <NUM>, a PBCH signal is received. At <NUM>, a PBCH channel is decoded and a CRC is demasked at <NUM>. As a result of the CRC demasking at <NUM>, K1 bits may be obtained from the CRC masking mapping at <NUM>. At <NUM>, a determination whether the frequency meets a frequency band threshold is made. The determination may be made based on whether the frequency is greater than, equal to, or less than a threshold frequency. If the frequency is below the threshold frequency, K1 bits are output as a SSB index time indication at <NUM>. If the frequency is above the threshold frequency, K2 bits are obtained from a control filed in the PBCH channel at <NUM> and K1 + K2 bits are output as a SSB index time indication at <NUM>.

Table <NUM> shows an example CRC masking table for an SSB index time indication where of L = <NUM>. As shown, the CRC masking #<NUM> may correspond to SSB index time indication bits <NUM> and CRC masking #<NUM> may correspond to SSB index time indication bits <NUM>.

According to another hybrid method, scrambling processing may be used for to indicate SSB indexes and LSBs for SSB index and MSBs for SSB indexes may be indicated in payloads or signals. For example, K1 bits for LSBs of an SSB index may be indicated using PBCH scrambling and K2 bits for MSBs of SSB index may be indicated in PBCH payload or PBCH signal.

For lower frequency bands, a WTRU or other applicable device may perform one or more of receiving a PBCH signal and descrambling a PBCH channel, decoding a PBCH channel, performing CRC verification, obtaining K1 bits from scrambling mapping and CRC verification, and outputting K1 bits as SSB index time indication. For higher frequency bands, a WTRU or other applicable device may additionally perform one or more of obtaining K2 bits from control field of decoded a PBCH channel, and outputting both K1 and K2 bits as SSB index time indication bits. K1 may be the LSBs for SSB index time indication and K2 may be the MSBs for SSB index time indication.

<FIG> shows an example SSB index time indication employing a hybrid scrambling code and control field. As shown, at <NUM>, a PBCH signal is received. At <NUM>, a PBCH signal is descrambled a PBCH channel is decoded at <NUM>. At <NUM> a CRC check is conducted and K1 bits are obtained from applicable scramble code or scramble code mapping at <NUM>. For example, scramble code or scramble code mapping may be performed for a PBCH, such as PBCH DMRS and/or PBCH payload. At <NUM>, a determination whether the frequency meets a frequency band threshold is made. The determination may be made based on whether the frequency is greater than, equal to, or less than a threshold frequency. If the frequency is below the threshold frequency, K1 bits are output as a SSB index time indication at <NUM>. If the frequency is above the threshold frequency, K2 bits are obtained from a control filed in the PBCH channel at <NUM> and K1 + K2 bits are output as a SSB index time indication at <NUM>.

According to another hybrid method, SSB index indication may be based on partitioning. Here, SSB index indication may be implicit for least significant bits (LSBs) such as, for example, K1 bits, and explicit for most significant bits (MSBs) such as, for example, K2 bits. The L threshold value used in such a solution may be, for example, <NUM> or <NUM>. Alternatively or in addition, the SSB index may be partitioned into two parts including SSB index within an SS burst (SSB group) and SS burst index (SSB group index) within a SS burst set. An SS burst may be a SSB group or the like. An SS burst index may be SSB group index or the like. The SSB index indication may be implicit for SSB index within an SS burst, for example, for K1 bits, and explicit for SS burst index within an SS burst set, for example, for K2 bits. The L threshold value used in such a solution may be, for example, <NUM> or <NUM>. Alternatively or in addition, the SSB index bits may be partitioned into two parts based on K1 bits and K2 bits. The SSB indication may be explicit for SSB index, such as, for example, for K1 bits if only K1 bits are present and may be implicit for SSB index based on K2 if total bits exceed K1 bits.

SSB index indication for one partition may be explicit such that part of an SSB index may correspond to part of a payload on NR-PBCH. For example, K2 bits may be carried in a PBCH payload. The K2 bits may be coded, rate-matched and interleaved along with other bits of a NR-PBCH and transmitted on data resource elements (RE). An explicit transmission may suffer from delay in decoding such that, for example, an SSB index may not be determined until decoding of the NR-PBCH at a receiver. Accordingly, for coherently detecting the NR-PBCH, a self-contained DMRS may be added. Although the DMRS may comprise one or more sequences known to a receiver, different sequences and shifts may be applied to implicitly indicate a part of an SSB index such as the part that is not explicitly indicated. As an example, K1 bits may be indicated implicitly using a DMRS and a receiver may detect which hypothesis of a DMRS variation is mostly likely transmitted to implicitly decode the SSB index. Accordingly, the receiver may not wait for an entire PBCH to be decoded to determine the SSB index.

A DMRS may comprise a gold sequence such that two M sequences may be generated and two different cyclic shifts m0 and m1 for the two M sequences may undergo an XOR operation with each other. The resulting sequence may be binary phase shift keying (BPSK) modulated and then may be repeated or truncated to fill the DMRS. A WTRU or other applicable device may use a combination function of m0 and m1 to indicate SSB index. Table <NUM> shows an example number of bits and number of m combinations (m0, m1) that correspond to L, a number of SSBs.

As an example, for L=<NUM>, the m0 and m1 combinations of Table <NUM> may be applied. As shown, a <NUM> SSB index may correspond to a (m0 m1) combination of (<NUM><NUM>).

A DMRS may comprise one M sequence where m0 may be used to indicate SSB index. Table <NUM> shows an example number of bits and number of m0 values that correspond to L, a number of SSBs. As shown, as an example, <NUM> SSBs may correspond to <NUM> bits and <NUM> m0 m sequences.

As an example, for L=<NUM>, the m0 values of Table <NUM> may be applicable. As shown, a <NUM> SSB index may correspond to a <NUM> m0 value.

A DMRS may comprise multiple M sequences where sequence IDs and shift m0 may be used to indicate SSB index.

A DMRS may comprise a Zadoff-Chu (ZC) sequence. ZC sequences may be used to indicate an SSB index such that CS may be used to indicate the SSB index, a root index of ZC may be used to indicate the SSB index, or a combination of CS and root index may be used to indicate SSB index. Table <NUM> shows an example number of bits and number of CS values that correspond to L, a number of SSBs.

As an example, for L=<NUM>, the CS ZC values of Table <NUM> may be applicable. As shown, a <NUM> SSB index may correspond to a <NUM> CS value and a <NUM> SSB index may correspond to a <NUM> CS value.

A DMRS may comprise a ZC sequence with a cover code and the cover code may be another sequence such as an m sequence. The ZC and the cover code may be multiplied or XORed with each other and m0 may be used to indicate SSB indexes. Table <NUM> shows an example number of bits and number of m0 values that are ZC multiplied or XORed with a cover code and that correspond to L, a number of SSBs.

Alternatively, a combination of CS (ZC) and m0 (M) may be used to indicate SSB indexes where a DMRS comprises a ZC sequence with a cover code and the cover code is another sequence such as an m sequence. The ZC and the cover code may be multiplied or XORed with each other. Table <NUM> shows an example number of bits and number of CS (ZC) and m0 (M sequence) combination values that correspond to L, a number of SSBs.

As an example, for L=<NUM>, the CS (ZC) and m0 (M sequence) combinations (CS, m0) shown in Table <NUM> may be applicable. As shown, a <NUM> SSB index may correspond to a (<NUM>,<NUM>) CS (ZC) and m0 (M sequence) combination (CS, m0) and a <NUM> SSB index may correspond to a (<NUM>, <NUM>) CS (ZC) and m0 (M sequence) combination (CS, m0).

According to a method, DMRS positions or locations may be used to indicate SSB indexes. Table <NUM> shows an example number of bits and number of DMRS positions that correspond to L, a number of SSBs.

As an example, for L=<NUM>, the DMRS positions shown in Table <NUM> may be applicable. As shown, a <NUM> SSB index may correspond to a position X and a <NUM> SSB index may correspond to a position W.

According to a method, a combination of DMRS positions/locations and sequences may be used to indicate SSB indexes. A subset of bits, or example, one or two bits, may be indicated via the DMRS location. Bits not indicated by the DMRS location may be indicated via one or more sequences. A combination of CS and/or m0/m1 and/or positions may be used to indicate SSB indexes. Table <NUM> shows an example number of bits and number of CS (ZC), m0 (m sequence) and position combination that correspond to L, a number of SSBs.

According to a method, DMRS phase rotation of OFDM symbols may be used to indicate SSB indexes. A subset of bits may be indicated via phase rotations and another subset or the rest of the bits may be indicated via sequences. For example, for multiple OFDM symbols, phase rotation may be applied on the second or remaining N-<NUM> PBCH OFDM symbols with respect to the first PBCH OFDM symbol for total N PBCH OFDM symbols. Alternatively, some bits may be indicated via the phase rotations for some resource blocks (RBs) while other bits may be indicated via the phase rotations for other RBs.

According to a method, different scrambling codes may be used for PBCH OFDM symbols to indicate SSB indexes. Table <NUM> shows an example number of bits and number of scrambling code combinations that correspond to L, a number of SSBs.

Gold sequences or m sequences may be generated using polynomials. For example, if the length of the M sequences is <NUM>, which may be repeated, a combination of the following polynomials may be used: <MAT> <MAT> <MAT>.

As another example, if the length of M Sequences is <NUM>, such as for higher density DMRS, a combination of the following polynomials may be used: <MAT> <MAT> <MAT>.

It will be understood that other polynomials such as irreducible primitive polynomials may also be used. Further, Cyclic Shifts in two sequences may be defined using following the equations: <MAT> <MAT> where the s1, s2 correspond to two m sequences of length L. Additionally, m0 and m1 may correspond to two cyclic shifts, and the value of n may range from <NUM> to L-<NUM>.

It will be understood that any one or a combination of the methods described herein may be used for SSB index indication.

It will also be understood that in addition or as an alternative to DMRS indication, implicit solutions for hybrid indication may also use scrambling, CRC, and/or Redundancy Version (RV).

A <NUM>-bit for Repetition Indication may also be used. Such <NUM>-bit for Repetition Indication may use DMRS, scrambling, CRC, and/or RV for SSB index indication. Such <NUM>-bit for Repetition Indication may also be carried in a PBCH payload. Additionally, an additional <NUM>-bit for half radio frame indication may also be used. Such <NUM>-bit for half radio frame indication may utilize DMRS, scrambling, CRC, RV for indication. Such <NUM>-bit for half radio frame indication may also be carried in PBCH payload. For example, such <NUM>-bit for half radio frame indication may be indicated or carried in scrambling and PBCH payload.

Methods for performing SSB transmission such as with timing information indication are described herein.

According to an implementation, an implicit indication method for SSB transmission is used if a characteristic, such as a frequency, is lower than a threshold. For example, an implicit indication technique for SSB transmission is used if the frequency is lower than a threshold frequency of <NUM>. As a specific example of an implicit indication technique, a sequence based indication method may be used. A number of bits, such as X bits, may be encoded implicitly using a sequence such as a reference sequence. The SSB index may be encoded in a scrambling sequence such as, for example, a PN code. A DMRS may be used to encode the SSB index indication such that, for example, a scrambling sequence or PN code may be used for a DMRS to indicate SSB index. Alternatively, an SSB index may be encoded in CRC, scrambling for payload or using other implicit methods. Scrambling may be a function of SSB index. Scrambling, whethersame or different, may be used for DMRS and/or payload in PBCH.

A hybrid indication method for SSB transmission may be used of a characteristic, such as a frequency, is higher than a threshold. For example, if the frequency is equal to or higher than <NUM>, then a hybrid indication method may be used. A hybrid indication method may employ both implicit and explicit indication techniques such as, for example, a combination of DMRS and PBCH payload may be used. A number of bits, such as X bits, of an SSB index may be encoded in PBCH DMRS sequences and another number or the remaining bits, such as Y bits, of an SSB index may be encoded in PBCH payload. To facilitate A PBCH payload may reserve X+Y bits for the SSB index to facilitate the encoding. Additionally, if the frequency is lower than the threshold, such as lower than <NUM> in this example, then Y bits may be reserved or Y bits or a subset of Y bits may be reused for other purposes such as assisting the indication of the location of cell-defining SSB or for supporting additional system operations such as assisting the indication of presence/absence of cell-defining SSB.

<FIG> shows an illustrative example of a SSB transmission method. At <NUM>, an SSB is transmitted via a downlink. An SSB transmission may be carrier frequency dependent or frequency band dependent. For example, at <NUM> a determination may be made whether a carrier frequency fc is high such that it is higher than or equal to a certain predefined carrier frequency fc1 where fc >= fc1. If fc is determined to be greater than or equal to fc1, then the SSB index bits may be partitioned into two parts at <NUM>. A first part of the SSB index may be assigned X bits and a second part SSB index may be assigned Y bits at <NUM> where the total SSB index bits are Nt bits which is equal to X+Y bits. The first part of the SSB index, such as the assigned X bits may be encoded via a DMRS at <NUM>. The second part of the SSB index, such as the assigned Y bits, may be encoded in PBCH payload such as the data channel and may be encoded in the PBCH data channel using encoding operation of Polar codes.

As shown at <NUM>, a determination that carrier frequency fc is high but not higher than a certain predefined carrier frequency fc1 such that fc < fc1, but higher than another predefined carrier frequency fc2 such that fc > fc2, and fc2 < fc1 may be made. If, fc > fc2, and fc2 < fc1 then the SSB index may be partitioned into two parts at <NUM>. It will be understood that the determinations <NUM> and <NUM> may occur at the same time or simultaneously and may be made inherently based on the frequency fc and without a determination being made. If partitioned, at <NUM>, a first part of the SSB index may be assigned X bits and a second part of the SSB index may be assigned Y bits. Alternatively, if partitioned, a second part of the SSB index may not be assigned any bit. If partitioned and if the second part SSB index is assigned Y bits, the total SSB index bits may be Nt, which equals X+Y bits. If the second part SSB index is not assigned any bit, the total SSB index bits may be Nt = X bits. At <NUM>, the first part SSB index may be encoded in DMRS such that X bits for the first part of the SSB index may be encoded using a DMRS sequence. If the second part SSB index is assigned bits, then, at <NUM>, Y bits for the second part SSB index may be encoded in the PBCH data channel using, for example, an encoding operation of Polar codes. Alternatively, Y bits for the second part SSB index may be ignored or discarded. Alternatively, Y bits for the second part SSB index may be reused for other system information or control information purposes.

As shown at <NUM>, a determination that carrier frequency fc is high but not higher than a certain predefined carrier frequency fc1 such that fc < fc1, but higher than another predefined carrier frequency fc2 such that fc > fc2, and fc2 < fc1 may be made. If fc > fc2, and fc2 < fc1 then the SSB index may not be partitioned into parts at <NUM>. It will be understood that the determinations <NUM> and <NUM> may occur at the same time or simultaneously and may be made inherently based on the frequency fc and without a determination being made. At <NUM>, the entire SSB index may be assigned X bits. The total SSB index bits may be designated by Nt which equals X bits. At <NUM>, the SSB index may be encoded in DMRS such that X bits for the SSB index may be encoded using the DMRS sequence.

As shown at <NUM>, a determination carrier frequency fc is low and lower than a predefined carrier frequency fc2 such that fc < fc2 may be made. If fc < fc2 then the SSB index may not be partitioned into parts. It will be understood that the determinations <NUM>, <NUM>, and <NUM> may occur at the same time or simultaneously and may be made inherently based on the frequency fc and without a determination being made. The SSB index may be assigned Z bits. The total SSB index bits are Nt = Z bits. The SSB index may be encoded in DMRS. Z bits for the SSB index may be encoded using DMRS sequence.

A PBCH data channel and reference signal, such as a DMRS, may be received. It will be understood that the PBCH data channel and reference signal may be received separately or may be received together. A portion of SSB time index bits may be obtained by detecting the PBCH reference signal. Additionally, the PBCH data channel may be descrambled and decoded using a channel-coding scheme such as via Polar codes. Another portion of the SSB time index bits may be obtained by decoding the PBCH channel and payload. A complete set of bits for the SSB time index bits may be obtained by combining the portion of the SSB time index obtained via the PBCH reference signal, such as the DMRS, and the portion of the SSB time index obtained via the decoded PBCH data channel. Additionally, the PBCH channel and payload may be decoded to obtain other timing information such as a system frame number and/or half radio frame number.

<FIG> shows an example SSB timing information indication method. At <NUM>, a WTRU may receive a PBCH reference signal and data channel. At <NUM>, the WTRU may detect a DMRS via the reference signal and may obtain a part of the SSB time index bits by detecting the DMRS reference signal. As shown at <NUM>, bits b2, b1, and b0 for part of a SSB time index may be received. At <NUM>, the WTRU may receive the PBCH data channel and may descramble and decode the PBCH channel using a channel coding scheme such as via Polar codes. The WTRU may obtain another part of the SSB time index by descrambling and/or decoding the PBCH channel such as bits b5, b5, and b3 as shown at <NUM>. A complete set of bits b0, b1, b2, b3, b4, and b5 for the SSB time index bits may be obtained at <NUM> by combining the portion of the SSB time index obtained via the PBCH reference signal, such as the DMRS, at <NUM> and the portion of the SSB time index obtained via the decoded PBCH data channel at <NUM>. Additionally, the PBCH channel and payload may be decoded to obtain other timing information such as a system frame number indicator <NUM> and/or half radio frame number <NUM>.

Methods for performing sequence based SSB transmissions are disclosed herein. According to a first method, an SSB index may be encoded in a sequence such as DMRS for SSB transmission. According to a method, multiple sequences may be generated where a Sequence A, or sequence type A, may be a function of a cell ID and a Sequence B, or sequence type B, may be a function of cell ID and an SSB index. Sequences, such as sequence A and B, may be generated using initialization, cyclic shifts, frequency shifts, etc. The initialization of sequence A may be a function of cell ID and the initialization of sequence B may be a function of cell ID and SSB index. Cyclic shifts and/or frequency shifts of sequence A may be a function of cell ID and cyclic shifts and/or frequency shifts of sequence B may be a function of cell ID and SSB index. Sequences may be multiplied with phase rotations based on the SSB index and may have the same or different lengths.

A DMRS sequence may be mapped to DMRS REs. A DMRS sequence A may be mapped to DMRS REs within a first set of PBCH OFDM symbols. A DMRS sequence B may be mapped to DMRS REs within a second set of PBCH OFDM symbols. A set of PBCH OFDM symbols may contain one or more OFDM symbols. For each PBCH OFDM symbol, DMRS sequences to DMRS REs may be mapped for lower frequency index, subcarrier index or RE index and higher frequency index, subcarrier index or RE index separately and/or at different times. The lower frequency index, subcarrier index, or RE index may be mapped before the higher frequency index, subcarrier index or RE index.

According to another method, multiple sequences where a sequence A, or sequence type A, is a function of cell ID and a sequence B, or sequence type B, is a function of cell ID and a SSB index. Sequences such as sequences A and B may be generated using initialization, cyclic shifts, frequency shifts, etc. Sequences may be multiplied with phase rotations based on a SSB index and may have the same or different lengths. DMRS sequence length may be a function of an RE mapping method such that if a DMRS is mapped to the REs overlapping with SSS bandwidth, then the DMRS may have a length L1. If a DMRS is mapped to the REs not overlapping with SSS bandwidth, then the DMRS may have length L2. Length L1 may not equal length L2 such that, for example, length L1 may be equal or less than length L2.

A DMRS sequence may be mapped to DMRS REs using any one or a combination of methods.

According to a DMRS sequence mapping method, a DMRS sequence A of length L1 may be mapped to DMRS REs within a first set of PBCH OFDM symbols and a DMRS sequence B, of length L2, may be mapped to DMRS REs within a second set of PBCH OFDM symbols. Length L1 may be equal to length L2. When mapping a DMRS sequence to DMRS REs, REs may be mapped in frequency first separately from being mapped in time. The Res may be mapped in frequency first and then may be mapped in time. For example, mapping DMRS sequence to DMRS REs may start with a lower frequency index, subcarrier index or RE index and then a higher frequency index, subcarrier index or RE index later. The mapping may then continue for a subsequent time such as, for a OFDM symbol index, slot index, non-slot index or mini-slot index.

According to another DMRS sequence mapping method, a DMRS sequence A of length L1 may be mapped to DMRS REs in DMRS REs overlapping with SSS bandwidth within a first set of PBCH OFDM symbols. A DMRS sequence B of length L2 may be mapped to DMRS REs in DMRS REs overlapping with SSS bandwidth within a first set of PBCH OFDM symbols and all DMRS REs within a second set of PBCH OFDM symbols. Length L1 may be different from length L2. For example, length L2 may be equal or greater than length L1. When mapping a DMRS sequence to DMRS REs, the REs may be mapped in frequency separately than in time such as being mapped in frequency first then being mapped in time. For example, mapping a DMRS sequence to DMRS REs may start with a lower frequency index, subcarrier index or RE index than a higher frequency index, subcarrier index or RE index later. The mapping may continue for a subsequent time such as, for example OFDM symbol index, slot index, non-slot index or mini-slot index.

According to another DMRS sequence mapping method, DMRS sequence A of length L1 may be mapped to DMRS REs in DMRS REs overlapping with SSS bandwidth within a first and second set of PBCH OFDM symbols. A DMRS sequence B of length L2 may be mapped to DMRS REs in DMRS REs overlapping with SSS bandwidth within the first and second set of PBCH OFDM symbols. Length L1 may be different from length L2. For example, length L2 may be equal or greater than length L1. When mapping a DMRS sequence to DMRS REs, the REs may be mapped in frequency separately than in time such as being mapped in frequency first then being mapped in time. For example, mapping a DMRS sequence to DMRS REs may start with a lower OFDM symbol index, slot index or mini-slot index than a higher lower OFDM symbol index, slot index or mini-slot index later. The mapping may continue for a subsequent time such as, for example OFDM symbol index, slot index, non-slot index or mini-slot index.

DMRS RE positions may be fixed or may be a function of cell ID. A DMRS RE position may be a function of a shift, which may be a function of cell ID. A DMRS RE position offset may be a function of a shift, which may be a function of cell ID. A DMRS RE position and/or offset may be fixed or employ a fixed offset.

Indications of used or unused SS blocks may be provided based on techniques disclosed herein. Reusing unused SSBs for transmission may allow system resources to be more efficiently utilized and system throughput to be enhanced. Unused SSB may be indicated by one or more methods including, but not limited to, simple bitmap, star point with duration and/or number of used SSBs, hybrid starting point with segment-wise bitmap, or the like.

In accordance with a simple bitmap method, an L-bit indicator may be used to indicate unused SSBs. The L-bit indicator may employ a simple bitmap such as, for example, for Nunused SSBs, L bits with Nunused bit locations, being marked as unused, may be used. A value, such as "<NUM>", may be used to mark unused SSBs and a different value, such as "<NUM>" may be used to mark used SSBs. For L = <NUM> SSBs, <NUM> bits signaling overhead may be required.

In accordance with a start point with duration and/or number of used SSBs method, two indicators may be used such that one indicator may indicate the starting point of used or unused SSBs, and the other indicator may be used to indicate the number of used or unused SSBs. As an example, a Nstart starting points indicator may be used such that log<NUM>(Nstart) bits may be needed. In addition, log<NUM>(Nunused) bits may be needed to indicate unused SSBs. Accordingly, a total of log<NUM>(Nstart) + log<NUM>(Nunused) bits may be needed. As an example, for Nstart = <NUM> and Nunused = <NUM>, a maximum of <NUM> overhead bits may be required. Using this method may result in a significant reduction in signaling overhead, compared to using the simple bitmap method.

In accordance with a hybrid method such as a hybrid starting point with segment-wise bitmap, two indicators may be used such that one indicator may indicate the starting point and the other indicator may indicate the used or unused SSBs associated with the indicated starting point. As an example, for Nstart = <NUM> and NSS_block,i = <NUM>, where i=<NUM>,<NUM>,<NUM>,<NUM>, maximum <NUM>+<NUM> bits overhead may be required. This may indicate a starting point and NSS_block,i associated with the i-th starting point. If extended to indicate two starting points, then 2x(<NUM>+<NUM>)=<NUM> bits signaling overhead may be required.

<FIG> shows an example diagram for an SSB indication employing a hybrid starting point with segment-wise bitmap method. As shown, SSB groups starting points are indicated by <NUM> and contain N SSBs <NUM> in each group. A bit <NUM> may correspond to each SSB <NUM> within a SSB group. As shown, the total number of SSBs is represented by L.

According to another method, SSB groupings may be used to indicate used and unused SSBs. SSBs may be grouped such that each group may have NSS_grp,i SSBs for a group i. The grouping may include equal size or unequal size grouping. After the grouping, the resulting number of SS groups may be denoted as LSS_group where LSS_group ≤ L. A group-bitmap may be used to indicate the LSS_group SSB group and LSS_group bits may be used for the group-bitmap. For equal sized grouping, the number of SS groups may be determined by <MAT>.

As an example, for L = <NUM> and NSS_grp,i = <NUM> for all i, LSS_group = <NUM>. Therefore, a total of <NUM> bits for signaling overhead may be required. SSB grouping may employ localized groupings or distributed groupings.

<FIG> shows SSB indications via SSB grouping and reduced bitmap where the groupings are equal sized. SS bulk groups are indicated by <NUM> and contain N SSBs <NUM> in each group. A total of K SS bulk groups <NUM> are provided. As shown, the total number of SSBs is represented by L. Each of the bits <NUM> correspond to a group such that the first group <NUM> is represented by b0 and the last group <NUM> is represented by b(K-<NUM>).

According to another method, multi-level indexing may be used to indicate used and unused SSBs. An SS burst index and SSB index may be used. Two bitmap indicators may be used such that a first bitmap indicator (Group-Bitmap) may correspond to an SS burst index (e.g., an SSB group index) and a second bitmap indicator (Bitmap-in-Group) may correspond to an SSB index. The first bitmap indicator may be used to indicate the used SS bursts and the second bitmap indicator may be used to indicate the used or unused SSBs in the SS bursts that are indicated as used. An SS burst may be a SSB group, or the like. The first bitmap indicator may be used as coarse indicator and the second bitmap indicator may be used as fine indicator, as disclosed herein.

According to another method, an OFDM symbol index may be used to indicate the inactive OFDM symbols within an SSB. The OFDM symbol index may be used to indicate inactive OFDM symbols across all SSBs. The used or unused OFDM symbols may be the same for every SSB. Alternatively, the OFDM symbol index may be used to indicate inactive OFDM symbols for a part of the used SSBs. The number of OFDM symbols per slot or subframe may be different depending on, for example, frequency bands and/or subcarrier spacing (SCS). For example, for a SCS of <NUM>, <NUM> OFDM symbols per <NUM>-slot (or <NUM> OFDM symbols per slot) may be present. For a SCS of <NUM>, <NUM> OFDM symbols per <NUM>-slot (or <NUM> OFDM symbols per slot) may be present. For a SCS of <NUM>: <NUM> OFDM symbols per <NUM>-slot (or <NUM> OFDM symbols per slot) may be present. For a SCS of <NUM>, <NUM> OFDM symbols per <NUM>-slot (or <NUM> OFDM symbols per slot) may be present.

An indication of SSB measurement time window and duration may be provided such that used SSBs may be utilized for measurement purpose. A time location of a used SSB may be provided and may facilitate the measurement for serving cells as well as neighbor cells. For example, a WTRU may receive the time location of used SSBs and may facilitate the measurement for serving cell and neighbor cells. Additionally, unused SSB may also be utilized for measurement purpose. For example, a WTRU may be receive the time location of unused SSBs and may use the time location of the unused SSBs to facilitate measurements such as, for example, interference measurements or signal strengths from neighbor cells.

A WTRU or other applicable device may receive a set of parameters for used and/or unused SSBs. The parameters may include, but are not limited to one or more measurement windows, timing parameters, duration parameters, offset and/or periodicity. The parameters may be provided via one or more indicators.

In an idle mode, a set of parameters for used and/or unused SSBs may be received or provided via NR-PBCH, via remaining minimum system information, and/or via other system information.

In a radio resource control (RRC) connected mode, a set of parameters for used and/or unused SSBs may be signaled via RRC signaling, MAC or MAC CE, and/or physical layer signaling such as NR-PDCCH or NR-ePDCCH.

According to methods disclosed herein, SSBs may be reused. As disclosed herein, SSBs can be used for transmitting synchronization signals and channels. To more efficiently utilize SSBs, other signals or channels may reuse a subset of SSBs to improve system throughput, reduce overhead and enhance spectrum efficiency. SSBs may be reused for other signals or channel transmissions such as, for example, for control and/or data transmission and reception, for CSI-RS transmission such as that performed using TDM, FDM, or hybrid methods, and/or for paging downlink control information (DCI).

Additionally, SSBs may be reused for control channel transmissions. For example, SSBs may be reused for control signaling to enable URLLC transmission, NR-PDCCH, NR-ePDCCH, paging signal or paging DCI, control channel for URLLC, NR-PUCCH, and/or scheduling requests (SR).

Additionally, SSBs may be reused for data channel transmission. For example, SSBs may be reused for URLLC transmission or mini-slot transmission such as for paging channels, paging PDSCH, and/or URLLC data channel.

Additionally, SSBs may be reused for reference signal transmission. For example, SSBs may be reused for CSI-RS transmission such as for channel state information reference signals (CSI-RS), and/or sound reference signals (SRS).

Unused SSBs may allow for the resources reserved for SSBs to be reused for other signal or channel transmissions, as described herein. Additionally or alternatively, a set or subset of SSBs may be transmitted but may not be used for initial access or synchronization purposes. Such set or subset of SSBs may be transmitted to support other procedures such as, for example, beam management. For DL beam management SSBs may be used to enable P-<NUM>, P-<NUM> and P-<NUM> procedures.

Further, in idle mode, used and/or unused SSBs may be signaled. The SSBs may be signaled via, for example, NR-PBCH where bits representing unused SSBs may be carried in a NR-PBCH payload. Alternatively or in addition, the SSBs may be signaled via remaining minimum system information where bits representing unused SSBs may be carried in remaining minimum system information that can be scheduled by NR-PBCH. Alternatively or in addition, SSBs may be signaled via other system information where bits representing unused SSBs may be carried in other system information that can be scheduled by the remaining minimum system information.

In RRC connected mode, used and/or unused SSBs may be signaled via, for example, RRC signaling, MAC or MAC CE, and/or physical layer signaling such as NR-PDCCH or NR-ePDCCH.

Claim 1:
A user equipment, UE, (<NUM>) comprising:
means configured to receive one or more synchronization signal blocks, SSBs;
means configured to determine an operational frequency band;
means configured to determine a value L corresponding to the operational frequency band, the value L indicating a maximum number of SSBs in a synchronization signal, SS, burst;
means configured to, on a condition that the value L is <NUM> or <NUM>, determine an SSB index based on a physical broadcast channel, PBCH, demodulation reference signal, DMRS, sequence; and
means configured to, on a condition that the value L is <NUM>, determine the SSB index using both of the PBCH DMRS sequence and a PBCH payload,
wherein, on the condition that the value L is <NUM>, the SSB index consists of least significant bits, LSBs, and most significant bits, MSBs,
wherein the LSBs for the SSB index is determined based on the PBCH DMRS sequence, and
wherein the MSBs for the SSB index is determined based on the PBCH payload.