Synchronization Signal Block Enhancement For Additional Numerologies

A method performed by a user equipment (UE) includes: determining to operate using a numerology comprising at least one item from a list consisting of: a subcarrier spacing of 60 kHz or greater, a cyclic prefix greater than 8 μs, and ten symbols per slot; and detecting and processing a first synchronization signal block (SSB), the first SSB associated with a burst set, wherein the burst set includes a plurality of SSBs having time domain (TD) locations fitting into 1 ms duration or 2 ms duration, the plurality of SSBs including 4, 5, 6, or 8 SSBs.

TECHNICAL FIELD

This application relates to wireless communication systems, and more particularly to techniques to enhance synchronization signal blocks (SSBs) for additional numerologies.

INTRODUCTION

NR technology may also make use of a variety of different base station and user equipment technologies to maintain communication at acceptable throughput rates. An example type of base station and user equipment technology includes air to ground (ATG) applications. An example of an ATG application includes a base station having antennas oriented generally upward communicating with an aircraft-based user equipment. ATG base stations may have large radio frequency (RF) footprints, e.g., a radius of hundreds of kilometers. By contrast, a typical terrestrial base station may have a footprint of only a few kilometers. Therefore, an ATG application may benefit from different numerologies than those traditionally used with terrestrial applications, but implementing different numerologies may create a need for addressing time domain and frequency domain characteristics of signals, such as synchronization signal blocks (SSBs).

BRIEF SUMMARY OF SOME EXAMPLES

For example, in an aspect of the disclosure, a method performed by a user equipment (UE), the method includes: determining to operate using a numerology comprising at least one item from a list consisting of: a subcarrier spacing of 60 kHz or greater, a cyclic prefix greater than 8 μs, and ten symbols per slot; and detecting and processing a first synchronization signal block (SSB), the first SSB associated with a burst set, wherein the burst set includes a plurality of SSBs having time domain (TD) locations fitting into 1 ms duration or 2 ms duration, the plurality of SSBs including 4, 5, 6, or 8 SSBs.

In another aspect, a UE includes: means for operating in a first mode, the first mode associated with air to ground (ATG) operation; and means for identifying a synchronization signal block (SSB) having a subcarrier spacing of 60 kHz or greater and a bandwidth of fewer than 20 resource blocks in accordance with the first mode.

In another aspect, a UE includes: a transceiver; and a processor configured to control the transceiver, the processor further configured to: operate using a numerology comprising at least one item from a list consisting of: a subcarrier spacing of 60 kHz or greater, a cyclic prefix greater than 8 μs, and ten symbols per slot; and detect and process a first synchronization signal block (SSB), the first SSB associated with a burst set, wherein the burst set includes a plurality of SSBs having time domain (TD) locations fitting into 1 ms duration or 2 ms duration, the plurality of SSBs including 4, 5, 6, or 8 SSBs.

In another aspect, a non-transitory computer-readable medium having program code recorded thereon includes: code for determining to operate in a first mode, the first mode associated with air to ground (ATG) operation; and code for identifying a synchronization signal block (SSB) having a subcarrier spacing of 60 kHz or greater and a bandwidth of fewer than 20 resource blocks in response to operating in the first mode.

DETAILED DESCRIPTION

As described in more detail below, various implementations include methods of wireless communication, apparatuses, and non-transitory computer-readable media that provide time domain and frequency domain enhancements for synchronization signal blocks (SSBs) for use with different numerologies, and which may be applicable to air to ground (ATG) applications. For instance, a piece of terrestrial user equipment (UE) may operate using a non-traditional numerology, such as a numerology with a subcarrier spacing of 60 kHz or greater and a cyclic prefix greater than about 8 μs. In doing so, the UE may look for SSBs that may have time domain locations fitting into 1 ms or 2 ms durations, including 4/5/6/8 SSBs for each synchronization signal (SSS) burst set. In one example, an aircraft UE may be preprogrammed to identify such SSBs during initial access. In another example, a UE may be preprogrammed to identify an SSB having a reduced bandwidth, such as fewer than 20 resource blocks.

The network100may support synchronous or asynchronous operation. For synchronous operation, the B Ss may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing, and transmissions from different BSs may not be aligned in time.

FIG.5provides other examples of BSs105and UEs115, and it is understood that those BSs105and UEs115operate the same as or similarly to those described with respect toFIG.1. For instance,FIG.5illustrates an ATG BS105gand three ATG UEs115l-n. These additional assets are described in more detail below.

In some aspects, a UE115attempting to access the network100may perform an initial cell search by detecting a PSS from a BS105. The PSS may enable synchronization of period timing and may indicate a physical layer identity value. The UE115may then receive a SSS. The SSS may enable radio frame synchronization, and may provide a cell identity value, which may be combined with the physical layer identity value to identify the cell. The PSS and the SSS may be located in a central portion of a carrier or any suitable frequencies within the carrier.

After receiving the PSS and SSS, the UE115may receive a MIB. The MIB may include system information for initial network access and scheduling information for RMSI and/or OSI. After decoding the MIB, the UE115may receive RMSI and/or OSI. The RMSI and/or OSI may include radio resource control (RRC) information related to random access channel (RACH) procedures, paging, control resource set (CORESET) for physical downlink control channel (PDCCH) monitoring, physical UL control channel (PUCCH), physical UL shared channel (PUSCH), power control, and SRS.

After obtaining the MIB, the RMSI and/or the OSI, the UE115can perform a random access procedure to establish a connection with the BS105. In some examples, the random access procedure may be a four-step random access procedure. For example, the UE115may transmit a random access preamble and the BS105may respond with a random access response. The random access response (RAR) may include a detected random access preamble identifier (ID) corresponding to the random access preamble, timing advance (TA) information, a UL grant, a temporary cell-radio network temporary identifier (C-RNTI), and/or a backoff indicator. Upon receiving the random access response, the UE115may transmit a connection request to the BS105and the BS105may respond with a connection response. The connection response may indicate a contention resolution. In some examples, the random access preamble, the RAR, the connection request, and the connection response can be referred to as message 1 (MSG1), message 2 (MSG2), message 3 (MSG3), and message 4 (MSG4), respectively. In some examples, the random access procedure may be a two-step random access procedure, where the UE115may transmit a random access preamble and a connection request in a single transmission and the BS105may respond by transmitting a random access response and a connection response in a single transmission.

After establishing a connection, the UE115and the BS105can enter a normal operation stage, where operational data may be exchanged. For example, the BS105may schedule the UE115for UL and/or DL communications. The BS105may transmit UL and/or DL scheduling grants to the UE115via a PDCCH. The scheduling grants may be transmitted in the form of DL control information (DCI). The BS105may transmit a DL communication signal (e.g., carrying data) to the UE115via a PDSCH according to a DL scheduling grant. The UE115may transmit a UL communication signal to the BS105via a PUSCH and/or PUCCH according to a UL scheduling grant.

In some aspects, the BS105may communicate with a UE115using hybrid automatic repeat request (HARQ) techniques to improve communication reliability, for example, to provide an ultra-reliable low-latency communication (URLLC) service. The BS105may schedule a UE115for a PDSCH communication by transmitting a DL grant in a PDCCH. The BS105may transmit a DL data packet to the UE115according to the schedule in the PDSCH. The DL data packet may be transmitted in the form of a transport block (TB). If the UE115receives the DL data packet successfully, the UE115may transmit a HARQ acknowledgement (ACK) to the BS105. Conversely, if the UE115fails to receive the DL transmission successfully, the UE115may transmit a HARQ negative-acknowledgement (NACK) to the BS105. Upon receiving a HARQ NACK from the UE115, the BS105may retransmit the DL data packet to the UE115. The retransmission may include the same coded version of DL data as the initial transmission. Alternatively, the retransmission may include a different coded version of the DL data than the initial transmission. The UE115may apply soft-combining to combine the encoded data received from the initial transmission and the retransmission for decoding. The BS105and the UE115may also apply HARQ for UL communications using substantially similar mechanisms as the DL HARQ.

In some aspects, the network100may operate over a system BW or a component carrier (CC) BW. The network100may partition the system BW into multiple bandwidth parts (BWPs) (e.g., portions). ABS105may dynamically assign a UE115to operate over a certain BWP (e.g., a certain portion of the system BW). The assigned BWP may be referred to as the active BWP. The UE115may monitor the active BWP for signaling information from the BS105. The BS105may schedule the UE115for UL or DL communications in the active BWP. In some aspects, a BS105may assign a pair of BWPs within the CC to a UE115for UL and DL communications. For example, the BWP pair may include one BWP for UL communications and one BWP for DL communications.

In some aspects, the network100may operate over a shared channel, which may include shared frequency bands or unlicensed frequency bands. For example, the network100may be an NR-unlicensed (NR-U) network. The BSs105and the UEs115may be operated by multiple network operating entities. To avoid collisions, the BSs105and the UEs115may employ a listen-before-talk (LBT) procedure to monitor for transmission opportunities (TXOPs) in the shared channel. For example, a transmitting node (e.g., a BS105or a UE115) may perform an LBT prior to transmitting in the channel. When the LBT passes, the transmitting node may proceed with the transmission. When the LBT fails, the transmitting node may refrain from transmitting in the channel. In an example, the LBT may be based on energy detection. For example, the LBT results in a pass when signal energy measured from the channel is below a threshold. Conversely, the LBT results in a failure when signal energy measured from the channel exceeds the threshold. In another example, the LBT may be based on signal detection. For example, the LBT results in a pass when a channel reservation signal (e.g., a predetermined preamble signal) is not detected in the channel.

In some aspects, the network100may operate over a high frequency band, for example, in a frequency range 1 (FR1) band or a frequency range 2 (FR2) band. FR1 may refer to frequencies in the sub-6 GHz range and FR2 may refer to frequencies in the mmWave range. To overcome the high path-loss at high frequency, the BSs105and the UEs115may communicate with each other using directional beams. For instance, a BS105may transmit SSBs by sweeping across a set of predefined beam directions and may repeat the SSB transmissions at a certain time interval in the set of beam directions to allow a UE115to perform initial network access. In the example of NTN resource105b, it may transmit SSBs on each of its beams at scheduled times, even if the beams do not steer. In some instances, each beam and its corresponding characteristics may be identified by a beam index. For instance, each SSB may include an indication of a beam index corresponding to the beam used for the SSB transmission. The UE115may determine signal measurements, such as reference signal received power (RSRP) and/or reference signal received quality (RSRQ), for the SSBs at the different beam directions and select a best DL beam. The UE115may indicate the selection by transmitting a physical random access channel (PRACH) signal (e.g., MSG1) using PRACH resources associated with the selected beam direction. For instance, the SSB transmitted in a particular beam direction or on a particular beam may indicate PRACH resources that may be used by a UE115to communicate with the BS105in that particular beam direction. After selecting the best DL beam, the UE115may complete the random access procedure (e.g., the 4-step random access or the 2-step random access) and proceed with network registration and normal operation data exchange with the BS105. In some instances, the initially selected beams may not be optimal or the channel condition may change, and thus the BS105and the UE115may perform a beam refinement procedure to refine a beam selection. For instance, BS105may transmit CSI-RSs by sweeping narrower beams over a narrower angular range and the UE115may report the best DL beam to the BS105. When the BS105uses a narrower beam for transmission, the BS105may apply a higher gain, and thus may provide a better performance (e.g., a higher signal-noise-ratio (SNR)). In some instances, the channel condition may degrade and/or the UE115may move out of a coverage of an initially selected beam, and thus the UE115may detect a beam failure condition. Upon detecting a beam failure, the UE115may perform beam handover.

In some aspects, the network100may be an IoT network and the UEs115may be IoT nodes, such as smart printers, monitors, gaming nodes, cameras, audio-video (AV) production equipment, industrial IoT devices, and/or the like. The transmission payload data size of an IoT node typically may be relatively small, for example, in the order of tens of bytes. In some aspects, the network100may be a massive IoT network serving tens of thousands of nodes (e.g., UEs115) over a high frequency band, such as a FR1 band or a FR2 band.

FIG.2is a timing diagram illustrating a radio frame structure200according to some aspects of the present disclosure. The radio frame structure200may be employed by BSs such as the BSs105and UEs such as the UEs115in a network such as the network100for communications. In particular, the BS may communicate with the UE using time-frequency resources configured as shown in the radio frame structure200. InFIG.2, the x-axes represent time in some arbitrary units and the y-axes represent frequency in some arbitrary units. The transmission frame structure200includes a radio frame201. The duration of the radio frame201may vary depending on the aspects. In an example, the radio frame201may have a duration of about ten milliseconds. The radio frame201includes M number of slots202, where M may be any suitable positive integer. In an example, M may be about 10.

Each slot202includes a number of subcarriers204in frequency and a number of symbols206in time. The number of subcarriers204and/or the number of symbols206in a slot202may vary depending on the aspects, for example, based on the channel bandwidth, the subcarrier spacing (SCS), and/or the cyclic prefix (CP). One subcarrier204in frequency and one symbol206in time forms one resource element (RE)212for transmission. A resource block (RB)210is formed from a number of consecutive subcarriers204in frequency and a number of consecutive symbols206in time.

In an example, a BS (e.g., BS105inFIG.1) may schedule a UE (e.g., UE115inFIG.1) for UL and/or DL communications at a time-granularity of slots202or mini-slots208. Each slot202may be time-partitioned into K number of mini-slots208. Each mini-slot208may include one or more symbols206. The mini-slots208in a slot202may have variable lengths. For example, when a slot202includes N number of symbols206, a mini-slot208may have a length between one symbol206and (N−1) symbols206. In some aspects, a mini-slot208may have a length of about two symbols206, about four symbols206, or about seven symbols206. In some examples, the BS may schedule UE at a frequency-granularity of a resource block (RB)210(e.g., including about 12 subcarriers204).

FIG.3illustrates a process of starting from an SSB to obtain the information about an initial downlink BWP and an initial uplink BWP part. In this implementation, the SSB includes a PBCH that carries MIB. A UE that receives the SSB decodes the SSB to acquire the MIB. The UE then parses the contents of the MIB, which point to a CORESET #0. The CORESET #0 includes a Physical Downlink Control Channel (PDCCH) and the PDCCH schedules system information block 1 (SIB1) on a PDSCH, and the SIB1 has information elements to identify an initial downlink BWP and an initial uplink BWP. The UE parses the contents of the SIB1, finds its initial downlink BWP and its initial uplink BWP and then uses the initial downlink BWP and uplink BWP to communicate with the BS for further configuration. For instance, the UE may communicate with the BS to be assigned a dedicated BWP on a particular beam for data transmission. Of course, some aspects of the disclosure may use a different MIB, a different CORESET #0, or a different SIB1. The SIB1 also identifies parameters relevant to numerology, such as subcarrier spacing and cyclic prefix.

FIG.4is a table illustrating a variety of example numerologies that may be applied in one or more implementations. In this example, each column provides a different numerology, where a numerology includes a set of parameters for communication between a UE and a base station. The first row designates a parameter or numerology (u), which may change among the different columns. For instance, the set of numerologies depicted in the table ofFIG.4assumes a formula where subcarrier spacing (SCS) is equal to 15*2uKHz. Thus, when u is equal to −1, then the SCS equals 7.5 kHz. Similarly, when u is equal to 0, then SCS equals 15 kHz, and when u is equal to 2, SCS equals 60 KHz.

The second and third rows display symbol duration and cyclic prefix (CP) in microseconds. The fourth row is total symbol duration in microseconds, and it equals the sum of the second and third rows. The fifth row provides a total number of OFDM symbols per slot. For example, the column corresponding to numerology −1 has seven OFDM symbols per slot, whereas the column corresponding to numerology −1B has 14 OFDM symbols per slot. Traditional LTE numerologies include 14 OFDM symbols per slot. However, with new uses for NR being pioneered, other numbers of OFDM symbols per slot are being considered, such as 7 (as in numerology −1), 12 (as in numerology 1 ECP), or 10 (as in numerology 2 e ECP).

It has been observed that in some ATG applications, propagation delay due to reflection off of tall buildings or mountains may be as high as 8.33 μs. Thus, the propagation delay of ATG applications may be significantly more than that expected from NTN applications or terrestrial applications. Some implementations described herein include a cyclic prefix that is equal to or greater than 8.33 μs to accommodate the propagation delay that might be expected in some ATG applications. Another issue in ATG applications might be Doppler effect. For instance, at 700 MHz, a maximum line of sight Doppler effect might be as large as 0.77 kHz. As center frequency increases, the line of sight Doppler effect might increase more than proportionally. For instance, at 3.5 GHz, the maximum line of sight Doppler effect might be around 3.89 kHz, and at 4.8 GHz, the maximum line of sight Doppler effect might be around 5.33 kHz. In some instances, a UE or a base station may have hardware and software capable of compensating for Doppler effect that is as high as about 10% of the SCS. Some UEs or base stations may include better or poorer capability, and this is just an example. Nevertheless, for implementations assuming compensation abilities exist for up to 10% of SCS, then in a numerology using 700 MHz, an SCS of 7.5 kHz or greater would be desirable. Similarly, in a numerology using a center frequency of 3.5 GHz, an SCS of 30 kHz or 60 kHz would be desirable, and in a numerology using 4.8 GHz as a center frequency, an SCS equal to or greater than 60 kHz would be desirable.

However, these concerns may also run into other constraints, such as available bandwidth on a center frequency or attenuation expected to affect a center frequency. Thus, while numerology −1 may have ample SCS and CP at 700 MHz, that center frequency may not provide a desired amount of bandwidth for an ATG UE that is built for 1 GHz or more bandwidth. Similarly, numerologies 3 and 4 may be best reserved for millimeter wave applications, though millimeter wave may experience attenuation that makes it unsuitable for the long distances covered by an ATG base station cell.

One possible solution might be to use numerology 1 ECP, which has an SCS of 30 kHz and a cyclic prefix of 8.33 μs. Numerology 1 ECP may be used with 3.5 GHz, thereby providing SCS of 60 kHz and CP of 8.33 μs. Those parameters may provide acceptable performance in an ATG application, considering propagation delay, Doppler effect, and expected attenuation. Similarly, numerology 2 eECP may be used with either 3.5 GHz or 4.8 GHz as a center frequency to provide SCS of 60 kHz and CP of 8.33 μs. Once again, these parameters may provide acceptable performance in an ATG application. The numerologies including “ECP” refer to an extended CP, which is accomplished by reducing a number of OFDM symbols per slot. Disadvantages associated with ECP numerologies include a reduction in efficiency due to the relative length of the CP versus the total symbol duration as well as mismatch with traditional numerologies having 14 symbols per OFDM slot. However, in some applications, the disadvantages of those numerologies may be outweighed by the advantages. In fact, for any given application, an engineer may pick a numerology for use based on a variety of factors. ATG applications present their own special considerations, propagation delay and Doppler effect being among them, which makes them different from other applications, such as a NTN and car-based terrestrial.

As noted above, traditional LTE numerologies include 14 OFDM symbols per slot. The number of OFDM symbols allow different emitters to coexist more easily. In the case of numerology −1, it has seven OFDM symbols per slot, but it aligns with traditional numerologies including 14 OFDM symbols per slot since 14 is a multiple of seven. However, the other numerologies in the table ofFIG.4may include 12 OFDM symbols per slot or 10 symbols per slot in order to accommodate a larger CP. Since neither 10 nor 12 are a multiple of seven, such numerologies create misalignment when coexisting with other applications using seven or 14 OFDM symbols per slot. Thus, ATG applications adopting a numerology using 10 or 12 (or some other number of OFDM symbols per slot) may cause incrementally more interference with terrestrial UEs.

FIG.5is an illustration of an example wireless communication network according to one implementation.FIG.5is offered to illustrate coexistence of an ATG BS105gwith a plurality of terrestrial BSs105d,105e. Terrestrial BS105dmay be substantially the same as the terrestrial BS105dofFIG.1. Also, the UEs115a,115bmay be the same as or similar to UEs115a,115bofFIG.1. Terrestrial BS105emay also be the same as or similar to any of the BSs105ofFIG.1, and UEs115o,115pmay also be the same as or similar to any of the BSs ofFIG.1. And although not shown inFIG.5, ATG BS105gmay have a backhaul connection with either one or both of the terrestrial BSs105d,105e.

ATG BS105gmay be implemented in any appropriate manner, although in one example it has antennas that are directed upward for better reception by the ATG UEs115l-n. The UEs115l-nmay include hardware mounted to a bottom of an aircraft to facilitate transmission and reception with the antennas of ATG BS105g. Further in this example, ATG BS105gmay communicate using greater power than would traditionally be used by any of the terrestrial BSs105d,105e. The greater power allows ATG BS105gto provide transmission and reception over a large cell501, which in this example is shown as extending up to 300 km. Of course, the scope of implementations includes any appropriate size of cell501, as 300 km is merely one example. The ATG BSs1151-nmay also transmit using a higher power than would traditionally be used with any of the terrestrial UEs115.

FIG.5shows that the terrestrial cells502,503may be encompassed by the large area of ATG cell501. In some implementations, ATG cell501may encompass more or fewer terrestrial cells, and some terrestrial cells may be partially within and partially without cell501. The two terrestrial cells502,503are shown encompassed by ATG cell501for ease of illustration, and it is understood that in some applications an example ATG cell501may encompass tens or even hundreds of terrestrial cells within a 200 km or 300 km radius.

An option for multiplexing ATG communications and terrestrial NR is frequency division multiplexing, although that may suffer from low spectral efficiency in some instances. Another more spectral-efficient way to allow a non-orthogonal use of radio frequencies among ATG assets and terrestrial assets is orthogonal time and frequency and space, which may cause other issues to arise. For instance, spectral efficiency may be low at higher frequencies (e.g., 4.8 GHz) due to larger Doppler effect and propagation delay.

Various implementations herein propose to use NR techniques with numerologies, such as that shown inFIG.4. Specifically, various implementations propose to use numerologies with the subcarrier spacing of 60 kHz and an extended CP for the reasons discussed above. However, no SSB structures are defined in current standards are in use for those numerologies. For instance, there is currently no defined time domain (TD) locations for SSBs with respect to those numerologies. Furthermore, reusing legacy SSB designs results in a bandwidth of 20 physical resource blocks (PRBs), or a bandwidth of about 14.4 MHz for single SSB. This may introduce limits on UE specific PDSCH scheduling, especially if multiple SSBs are frequency division multiplexed in a 100 MHz component carrier (CC). Therefore, various implementations propose usable and advantageous time domain locations as well as a reduced bandwidth SSB that may find use in applications with non-traditional numerologies, such as ATG applications.

FIG.6is an illustration of example TD locations for SSBs, according to various implementations. In the example ofFIG.6, the TD locations may be adopted in both FDD and TDD applications.

As noted above, for numerologies comprising a large subcarrier spacing (e.g., 60 kHz or greater) as well as a relatively large CP length (e.g., 8 μs or greater), new SSB TD locations and SSB structures are desirable. Accordingly, the TD locations ofFIG.6are new and may be appropriate to use with non-traditional numerologies, such as the one labeled 2 eECP inFIG.4. In the example ofFIG.6(and inFIG.7as well) there are 10 symbols per slot, and 40 symbols in 1 ms.

Each of the different rows601-606represents a different first set configuration. Looking at row601first, it has eight SSBs within 1 ms or 40 symbols. Each SSB spans four symbols, and in row601, the SSBs are located at symbol indexes 1-4, 6-9, 11-14, 16-19, 21-24, 26-29, 31-34, and 36-39. Row602can fit as many as four SSBs within 0.5 ms or 20 symbols. In the example of row602, the SSBs of the burst set are at symbol indexes 12-15, 16-19, 20-23, 24-27, 28-31, 32-35, and 36-39.

Row603includes eight SSBs within 2 ms or 80 symbols. The SSBs are found at the symbol indexes 6-9, 16-19, 26-29, and 36-39, and then repeating onto an additional group of 40 indexes (not shown). Row604includes four SSBs within 1 ms or 40 symbols. The SSBs are at symbol indexes 12-15, 16-19, 32-35, and 36-39.

Various implementations also include burst set having five or six SSBs, as in rows605-606. Looking at row605, the SSBs are shown at symbol indexes 4-7, 12-15, 20-23, 28-31, and 36-39 (five SSBs within 1 ms). Row606includes six SSBs within 1 ms at symbol indexes 2-5, 8-11, 14-17, 20-23, 26-29, and 32-35.

Of course, the specific TD locations ofFIG.6are for example, and it is understood that other implementations may locate SSBs at different symbol indexes.

FIG.7is an illustration of example TD locations for SSBs, according to various implementations. In the example ofFIG.7, the TD locations may be more adoptable for use in TDD applications than in FDD applications. Once again, the rows701and702include SSB burst set that may be used with a subcarrier spacing of 60 kHz, and extended prefix greater than 8 μs, and include a number of blocks such as 4/5/6/8.

In row701, a burst set may include either eight SSBs within 1 ms or 40 symbols are for SSBs within 0.5 ms or 20 symbols. The SSBs are shown at symbol indexes 1-4, 5-8, 11-14, 15-18, 21-24, 25-28, 31-34, and 35-38. Row702illustrates that a burst set may include eight SSBs within 2 ms (80 symbols) are for SSBs within 1 ms (40 symbols). In the case of eight SSBs, the SSBs would be located at symbol indexes 4-7, 14-17, 24-27, and 34-37 and repeat with in a subsequent group of 40 symbols (not shown). In the case of four SSBs in a burst set, they would be located at symbol indexes 4-7, 14-17, 24-27, and 34-37.

As shown inFIGS.6and7, if a burst set has 4, 5, or 6 SSBs, then it can be located within a 1 ms duration (40 symbols) if eight SSBs are in a burst set, they may be located within a 1 ms duration or a 2 ms duration (80 symbols). The inter-SSB interval in the time domain in the case of 2 ms duration can be greater than that of the case of the 1 ms duration. If only four SSBs are in a single burst set, they can be located within 0.5 ms duration (20 symbols).

In some TDD implementations, some symbol indexes may be left blank so that those indexes may be used for uplink opportunities. For instance, inFIG.7at row701, symbol index 9 is left blank, and in row702symbols 8-9 are left blank. Thus, in these implementations later symbols in the slot are left blank in TDD systems, where as they might be used in FDD systems. For instance, in row602ofFIG.6, the various SSBs may be contiguous, though in FDD systems other frequencies may be used for uplink opportunities. Additionally, some implementations spread the burst set out over 2 ms, which leaves a greater inter-SSB interval in the time domain, where uplink resources may be placed within the inter-SSB interval. Another feature of some implementations is that TD locations of SSBs may be different for TDD versus FDD. For instance, row603, as it represents a 2 ms burst set with eight SSBs or a 1 ms burst set having four SSBs, may be more appropriate for FDD applications because of the larger inter-symbol intervals.

An advantage of the TD locations shown inFIGS.6-7is that they provide flexibility for a designer to choose appropriate burst sets for different applications. For instance, some UEs may be preprogrammed to look for burst sets with the properties described above when operating in an ATG mode or otherwise using a non-traditional numerology. When TDD is preferred, a base station may use one of the example burst sets described above having smaller inter-symbol intervals and/or leaving later symbol indexes within a slot blank. By contrast, when FDD is preferred, base station may use other burst set with larger inter-symbol intervals. Similarly, a UE may be preprogrammed to look for such burst set based on whether FDD or TDD is preferred.

FIG.8is an illustration of example SSBs, some with reduced bandwidth, according to some implementations. SSB801is used with current standards. SSB801is transmitted on four symbols over 20 resource blocks (RBs). However, if SSB801was used with a numerology with 60 kHz subcarrier spacing, then it may be difficult to multiplex more SSBs within the same bandwidth in the frequency domain. It would be beneficial in some instances to reduce the bandwidth of the SSBs to allow for more frequency space between the SSBs as well as to allow for more flexibility in PDSCH scheduling.

SSBs802and803have reduced bandwidth compared to SSB801. Specifically, SSB802only spans 16 RBs, but it is increased in the time domain by occupying five symbols instead of four. As a result, the bandwidth is 11.52 MHz. Similarly, SSB803only spans 12 RBs, but it is increased in the time domain by occupying six symbols instead of four. The bandwidth is 8.64 MHz. In the example of SSB802, the bandwidth is reduced by locating the PBCH in four symbols, and in the example of SSB803, the bandwidth is reduced by locating the PBCH in five symbols. In either case, the time domain properties of the PSS and SSS may remain the same as in a traditional SSB.

Reducing the bandwidth of the SSB might cause larger transition band slopes, especially for the PSS portion. Accordingly, UEs may include increased filtering capabilities to properly handle the transition band slopes. Some implementations may include a base station informing the UE to increase its filtering in response to using reduced-bandwidth SSBs.

Some UEs may be pre-programmed to identify SSBs having the time domain and frequency domain characteristics ofFIG.8. For instance, when a UE accesses a frequency band having a non-traditional numerology (e.g., 60 kHz subcarrier spacing and CP greater than 8 μs), it may be programmed to then as a default attempt to identify reduced-bandwidth SSBs, such as802,803. Similarly, the decision to attempt to identify reduced-bandwidth SSBs may be based on knowledge of the type of UE itself (e.g., an ATG UE type) or identifying the base station as an ATG base station. Also, while the particular TD and FD characteristics of SSBs802,803are provided herein, it is understood that they are examples. The scope of implementations may include any appropriate reduced-bandwidth structure that reduces a number of RBs and SSB. Furthermore, the scope of embodiments may include any appropriate SSB structure that increases a number of symbols.

A possible advantage of the implementations of SSBs802and803is that the reduced bandwidth may allow for frequency division multiplexing more SSBs in one component carrier, and it may relax some frequency domain scheduling limitations on the downlink, such as for PDSCH.

FIG.9is an illustration of an example method900for handling SSBs. Method900may be performed by a UE, such as any of the UEs115ofFIGS.1and5. For instance, the UE may be a terrestrial UE or an ATG UE. The actions of method900are performed as the UE communicates with the BS, which may be any of the B Ss105ofFIGS.1and5.

At action901, the UE determines to operate using a numerology that is nontraditional. For instance, the numerology may include a subcarrier spacing of 60 kHz or greater, a cyclic prefix (CP) greater than 8 μs, and/or using 10 symbols per slot. An example of such a nontraditional numerology is 2eECP inFIG.4. However, the scope of embodiments may include any numerology having one or more of (but not necessarily all of) the following properties: a subcarrier spacing of 60 kHz or greater, a CP greater than 8 μs, and 10 symbols per slot.

The UE may determine to operate using that numerology based on any of a number of factors. For instance, the UE may be preprogrammed to operate in an air to ground (ATG) mode, where using a nontraditional numerology is a default. The determination to operate using the numerology may also be based at least in part on determining that a base station transmitting the SSB is an ATG base station. The determination that the UE is to operate in an ATG mode may be a static configuration of the UE. For example, the UE may be designated as such when the UE is initially configured and the UE may determine to run in an ATG mode by reading the configuration from memory. In other aspects, the determination that the UE is to run in an ATG mode may be determined more dynamically, for example based on a configuration from a BS, or a determination based on a characteristic such as a GPS reading. The UE may communicate with a BS to receive a message comprising information indicating that the UE is an aircraft UE and should operate in an ATG mode. The UE may, in some aspects, communicate with a GPS module of the UE to determine an altitude, and determine to operate in an ATG mode when the UE is above a threshold altitude. In some aspects, the determination to operate in an ATG mode for the purposes of the method may change over time, for example if the UE is on an aircraft, whether the UE operates in an ATG mode may change depending on whether the aircraft is on the ground or at a certain altitude.

At action902, the UE detects and processes a first SSB. In this example, the first SSB is associated with a burst set that includes a plurality of SSBs having TD locations fitting into a 1 ms duration or a 2 ms duration and including 4, 5, 6, or 8 SSBs. Examples of such TD locations are found atFIGS.6-7. In an example use case, the UE is pre-programmed to be able to detect and process a first SSB having any one or a combination of the following properties: the burst set being within a 1 ms duration ready to millisecond duration and 4, 5, 6, 8 SSBs in the burst set. For instance, the burst set may include eight SSBs per a 2 ms duration (80 symbols) are over a 1 ms duration (40 symbols), four SSBs over 20 symbols are over 40 symbols, or either five or six SSBs over 40 symbols.

Furthermore, the UE may be preprogrammed to operate in either a TDD mode or an FDD mode. In such case, some TD SSB locations may be associated with a TDD mode and other TD SSB locations may be associated with an FDD mode. For instance, when operating in an FDD mode, the UE may detect and process burst sets with larger inter-symbol intervals or may detect and process burst sets that avoid end symbols in the slots when operating in a TDD mode.

The scope of implementations is not limited to the specific actions described above. Rather, other embodiments may add, omit, rearrange, or modify any of the actions described above. For instance, method900may be performed at power up, during initial access, or during mobility operations. Method900may be repeated as appropriate.

FIG.10is an illustration of an example method1000for identifying and processing lower-bandwidth SSBs. Method1000may be performed by a UE, such as any of the UEs115ofFIGS.1and5. For instance, the UE may be a terrestrial UE or an ATG UE. The actions of method1000are performed as the UE communicates with the BS, which may be any of the BSs105ofFIGS.1and5.

At action1001, the UE determines to operate in a first mode. In this example, the first mode includes an air to ground mode. The UE may determine to operate in the air to ground mode based on any appropriate condition. In one example, the UE determines to operate in the air to ground mode based on its identity as an ATG UE, where it is preprogrammed to operate in an ATG mode as a default. Additionally, or alternatively, the UE may determine to operate in the air to ground mode based on determining that the base station is an ATG base station. Further in this example, the ATG mode may include operating according to a nontraditional numerology. Examples of nontraditional numerologies are given inFIG.4, with one specific example including a subcarrier spacing of 60 kHz and a CP greater than 8 μs.

The determination that the UE is to operate in an ATG mode may be a static configuration of the UE. For example the UE may be designated as such when the UE is initially configured and the UE may determine to run in an ATG mode by reading the configuration from memory. In other aspects, the determination that the UE is to run in an ATG mode may be determined more dynamically, for example based on a configuration from a BS, or a determination based on a characteristic such as a GPS reading. The UE may communicate with a BS to receive a message comprising information indicating that the UE is an aircraft UE and should operate in an ATG mode. The UE may, in some aspects, communicate with a GPS module of the UE to determine an altitude, and determine to operate in an ATG mode when the UE is above a threshold altitude. In some aspects, the determination to operate in an ATG mode for the purposes of the method may change over time, for example if the UE is on an aircraft, whether the UE operates in an ATG mode may change depending on whether the aircraft is on the ground or at a certain altitude.

At action1002, the UE identifies an SSB having a subcarrier spacing of 60 kHz or greater and a bandwidth of fewer than 20 resource blocks. Examples of such SSBs are found inFIG.8, which provides example SSBs802,803in which bandwidth is limited while a number of symbols is increased. In the example of SSB802, the bandwidth is reduced to 16 RBs, and in the example of SSB803, the bandwidth is reduced to 12 RBs. In SSB802, the PBCH is located over four symbols, and in SSB802, the PBCH is located over five symbols. Thus, a reduction in bandwidth is accompanied by an increase in the time domain footprint. Furthermore, in these examples, the PSS and SSS may remain the same as in traditional SSBs.

The scope of implementations is not limited to the particular examples provided at actions1001-1002, as other embodiments may add, omit, rearrange, or modify one or more the actions. For instance, method1000may be performed at power up, during initial access, and during mobility operations and may be repeated as appropriate.

Various implementations may include one or more advantages. For instance, some implementations may facilitate the use of non-traditional numerologies in ATG applications. ATG applications may benefit from the nontraditional numerologies because of Doppler effect in timing alignment issues, as discussed in more detail above. For instance, a numerology using CP greater than 8 μs may provide beneficial trade-offs in terms of timing alignment and Doppler robustness when compared to other traditional numerologies. Various implementations herein provide techniques to implement such numerologies within operating applications. For instance, the examples ofFIGS.6-7and will nine provide time domain locations for SSBs in burst sets, where those burst sets may accommodate a nontraditional numerology that, e.g., includes 10 symbols per slot. Additionally, the examples ofFIGS.8and10provide techniques that may be used to reduce a bandwidth of SSBs, which may be beneficial when a relatively large (e.g., 60 kHz) subcarrier spacing is used. The examples ofFIGS.8and10may allow for more SSBs to be multiplexed within the frequency domain and may also allow for more scheduling flexibility for the PDSCH due to a reduced usage of bandwidth by the SSBs.

FIG.11is a block diagram of an exemplary UE1100according to some aspects of the present disclosure. The UE1100may be a UE115discussed above inFIGS.1and5. As shown, the UE1100may include a processor1102, a memory1104, a transceiver1110including a modem subsystem1112and a radio frequency (RF) unit1114, and one or more antennas1116. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The memory1104may include a cache memory (e.g., a cache memory of the processor1102), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. For instance, memory1104may code that includes information indicating that that the UE is a ATG UE or that the UE should as a default operate in an ATG mode, including using a nontraditional numerology.

In an aspect, the memory1104includes a non-transitory computer-readable medium. The memory1104may store, or have recorded thereon, instructions1106. The instructions1106may include instructions that, when executed by the processor1102, cause the processor1102to perform the operations described herein with reference to the UEs115in connection with aspects of the present disclosure, for example, aspects ofFIGS.1-10. Instructions1106may also be referred to as program code. The program code may be for causing a wireless communication device to perform these operations, for example by causing one or more processors (such as processor1102) to control or command the wireless communication device to do so. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

As shown, the transceiver1110may include the modem subsystem1112and the RF unit1114. The transceiver1110can be configured to communicate bi-directionally with other devices, such as the BSs105. The modem subsystem1112may be configured to modulate and/or encode the data from the memory1104according to a modulation and coding scheme (MCS), e.g., a low-density parity check (LDPC) coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit1114may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data from the modem subsystem1112(on outbound transmissions) or of transmissions originating from another source such as a UE115or a BS105. The RF unit1114may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver1110, the modem subsystem1112and the RF unit1114may be separate devices that are coupled together at the UE115to enable the UE115to communicate with other devices.

The RF unit1114may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas1116for transmission to one or more other devices. The antennas1116may further receive data messages transmitted from other devices. The antennas1116may provide the received data messages for processing and/or demodulation at the transceiver1110. The transceiver1110may provide the demodulated and decoded data to the processor1102processing. The antennas1116may include multiple antennas of similar or different designs in order to sustain multiple transmission links. The RF unit1114may configure the antennas1116.

In an aspect, the UE1100can include multiple transceivers1110implementing different RATs (e.g., NR and LTE). In an aspect, the UE1100can include a single transceiver1110implementing multiple RATs (e.g., NR and LTE). In an aspect, the transceiver1110can include various components, where different combinations of components can implement different RATs.

FIG.12is a block diagram of an exemplary BS1200according to some aspects of the present disclosure. The BS1200may be a BS105in the network100as discussed above inFIGS.1and5. A shown, the BS1200may include a processor1202, a memory1204, a transceiver1210including a modem subsystem1212and a RF unit1214, and one or more antennas1216. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The memory1204may include a cache memory (e.g., a cache memory of the processor1202), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, a solid state memory device, one or more hard disk drives, memristor-based arrays, other forms of volatile and non-volatile memory, or a combination of different types of memory. In some aspects, the memory1204may include a non-transitory computer-readable medium. The memory1204may store instructions1206. The instructions1206may include instructions that, when executed by the processor1202, cause the processor1202to cause the other components of the base station1200to communicate with the UE1100, such as by transmitting SSBs, configurations, and the like, and actions described above with respect toFIGS.1-10. Instructions1206may also be referred to as code, which may be interpreted broadly to include any type of computer-readable statement(s) as discussed above with respect toFIG.11.

As shown, the transceiver1210may include the modem subsystem1212and the RF unit1214. The transceiver1210can be configured to communicate bi-directionally with other devices, such as the UEs115and/or another core network element. The modem subsystem1212may be configured to modulate and/or encode data according to a MCS, e.g., a LDPC coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit1214may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data (e.g., SSBs, RMSI, MIB, SIB, frame based equipment—FBE configuration, PRACH configuration PDCCH, PDSCH) from the modem subsystem1212(on outbound transmissions) or of transmissions originating from another source such as a UE115, the node315, and/or BS1200. The RF unit1214may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver1210, the modem subsystem1212and/or the RF unit1214may be separate devices that are coupled together at the BS105to enable the BS105to communicate with other devices.

The RF unit1214may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas1216for transmission to one or more other devices. The antennas1216may be similar to the antennas of the BS105discussed above. This may include, for example, transmission of information to complete attachment to a network and communication with a camped UE115according to some aspects of the present disclosure. The antennas1216may further receive data messages transmitted from other devices and provide the received data messages for processing and/or demodulation at the transceiver1210. The transceiver1210may provide the demodulated and decoded data (e.g., PUCCH control information, PRACH signals, PUSCH data) to the processor1202for processing. The antennas1216may include multiple antennas of similar or different designs in order to sustain multiple transmission links.

In an aspect, the BS1200can include multiple transceivers1210implementing different RATs (e.g., NR and LTE). In an aspect, the BS1200can include a single transceiver1210implementing multiple RATs (e.g., NR and LTE). In an aspect, the transceiver1210can include various components, where different combinations of components can implement different RATs.

Implementation examples are described in the following numbered clauses:1. A method performed by a user equipment (UE), the method comprising:determining to operate using a numerology comprising at least one item from a list consisting of: a subcarrier spacing of 60 kHz or greater, a cyclic prefix greater than 8 μs, and ten symbols per slot; anddetecting and processing a first synchronization signal block (SSB), the first SSB associated with a burst set, wherein the burst set includes a plurality of SSBs having time domain (TD) locations fitting into 1 ms duration or 2 ms duration, the plurality of SSBs including 4, 5, 6, or 8 SSBs.2. The method of clause 1, wherein the burst set spans a plurality of slots, further wherein the burst set avoids symbols at ends of each slot.3. The method of clauses 1-2, wherein the UE comprises an air to ground (ATG) UE.4. The method of clauses 1-3, wherein the burst set includes eight SSBs per a 2 ms duration.5. The method of clauses 1-3, wherein the burst set includes five SSBs per 1 ms.6. The method of clauses 1-3, wherein the burst set includes six SSBs per 1 ms.7. The method of clauses 1-6, wherein determining to operate using the numerology is based at least in part on determining to operate in an air to ground (ATG) mode.8. The method of clauses 1-7, wherein determining to operate using the numerology is based at least in part on determining that a base station transmitting the SSB is an air to ground (ATG) base station.9. A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:code for determining to operate in a first mode, the first mode associated with air to ground (ATG) operation; andcode for identifying a synchronization signal block (SSB) having a subcarrier spacing of 60 kHz or greater and a bandwidth of fewer than 20 resource blocks in response to operating in the first mode.10. The non-transitory computer-readable medium of clause 9, wherein each SSB includes fewer than 16 resource blocks (RBs).11. The non-transitory computer-readable medium of clauses 9-10, wherein each SSB includes no more than 12 resource blocks (RBs).12. The non-transitory computer-readable medium of clauses 9-11, wherein the SSB includes five symbols.13. The non-transitory computer-readable medium of clauses 9-12, wherein the SSB includes six symbols.14. The non-transitory computer-readable medium of clauses 9-13, further comprising:code for increasing filtering for transition band slopes in response to receiving an instruction from a base station transmitting the SSB.15. The non-transitory computer-readable medium of clauses 9-14, further comprising:code for increasing filtering for transition band slopes in response to determining that the SSB comprises a reduced-bandwidth SSB.16. The non-transitory computer-readable medium of clauses 9-15, wherein determining to operate in the first mode is based at least in part on determining that a base station transmitting the SSB is an air to ground (ATG) base station.17. The non-transitory computer-readable medium of clauses 9-16, wherein a physical broadcast channel (PBCH) of the SSB is located in four symbols.18. The non-transitory computer-readable medium of clauses 9-16, wherein a physical broadcast channel (PBCH) of the SSB is located in five symbols.19. The non-transitory computer-readable medium of clauses 9-18, wherein the first mode comprises using a numerology having 60 kHz subcarrier spacing and a cyclic prefix greater than 8 μs.20. A user equipment (UE) comprising:a transceiver; anda processor configured to control the transceiver, the processor further configured to:operate using a numerology comprising at least one item from a list consisting of: a subcarrier spacing of 60 kHz or greater, a cyclic prefix greater than 8 μs, and ten symbols per slot; anddetect and process a first synchronization signal block (SSB), the first SSB associated with a burst set, wherein the burst set includes a plurality of SSBs having time domain (TD) locations fitting into 1 ms duration or 2 ms duration, the plurality of SSBs including 4, 5, 6, or 8 SSBs.21. The UE of clause 20, wherein the UE comprises an air to ground (ATG) UE implemented in an aircraft.22. The UE of clauses 20-21, wherein the processor is further configured to determine to operate using the numerology based at least in part on determining that a base station transmitting the SSB is an air to ground (ATG) base station.23. The UE of clauses 20-22, wherein the processor is further configured to determine to operate using the numerology based at least in part on determining that the UE is operating in an air to ground (ATG) mode.24. The UE of clauses 20-23, wherein the processor is configured to detect and process the SSB within the burst set having eight SSBs per 80 symbols.25. The UE of clauses 20-23, wherein the processor is configured to detect and process the SSB within the burst set having five SSBs per 40 symbols.26. The UE of clauses 20-25, wherein the burst set spans a plurality of slots, further wherein the burst set avoids symbols at ends of each slot, and wherein the processor is configured to transmit uplink signals in the symbols at the ends of each slot.27. A user equipment (UE) comprising:means for operating in a first mode, the first mode associated with air to ground (ATG) operation; andmeans for identifying a synchronization signal block (SSB) having a subcarrier spacing of 60 kHz or greater and a bandwidth of fewer than 20 resource blocks in accordance with the first mode.

28. The UE of clause 27, further comprising:means for increasing filtering for transition band slopes in response to receiving an instruction from a base station transmitting the SSB.

29. The UE of clauses 27-28, further comprising:code for increasing filtering for transition band slopes in response to determining that the SSB comprises a reduced-bandwidth SSB.

30. The UE of clauses 27-29, further comprising:means for determining to operate in the first mode based at least in part on determining that a base station transmitting the SSB is an air to ground (ATG) base station.