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Title:
PHYSICAL RANDOM ACCESS CHANNEL ARRANGEMENT FOR NEW RADIO UNLICENSED
Document Type and Number:
WIPO Patent Application WO/2019/215670
Kind Code:
A1
Abstract:
Systems, methods, apparatuses, and computer program products for physical random access channel (PRACH) transmission in a new radio unlicensed (NR-U) band scenario are provided.

Inventors:
HOOLI KARI (FI)
TIIROLA ESA (FI)
LUNTTILA TIMO (FI)
HAKOLA SAMI (FI)
Application Number:
PCT/IB2019/053839
Publication Date:
November 14, 2019
Filing Date:
May 09, 2019
Export Citation:
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Assignee:
NOKIA TECHNOLOGIES OY (FI)
International Classes:
H04W74/08
Foreign References:
US20160323915A12016-11-03
US20170303303A12017-10-19
Other References:
HUAWEI ET AL: "Random access in NR unlicensed", vol. RAN WG1, no. Sanya, China; 20180416 - 20180420, 15 April 2018 (2018-04-15), XP051425978, Retrieved from the Internet [retrieved on 20180415]
Download PDF:
Claims:
WE CLAIM:

1. A method, comprising:

determining, at a user equipment, an ongoing channel occupancy time; determining whether the ongoing channel occupancy time is shared with the user equipment;

selecting a physical random access channel type to be transmitted based on the determining of the ongoing channel occupancy time;

performing listen before talk associated with the selected physical random access channel type; and

transmitting at least one random access channel signal on a physical random access channel, in case of successful listen before talk.

2. A method of claim 1, wherein the shared ongoing channel occupancy time is shared with the user equipment from a network node.

3. A method of claim 1 or 2, wherein the determining whether the ongoing channel occupancy time being shared with the user equipment is based on at least one of blind decoding of group common physical downlink control channel or detection of reference signal associated with a target cell.

4. A method of any one of claims 1 through 3, further comprising: based at least on the selected physical random access channel type, blind decoding physical downlink control channel for random access response identified by random access radio network temporary identifier.

5. A method of any one of claims 1 through 4, further comprising transmitting on a first type of physical random access channel, when there is ongoing shared channel occupancy time.

6. A method according to claim 5, wherein the first type of physical random access channel comprises PRACH Type 1.

7. A method of claim 6, wherein the PRACH Type 1 comprises resource continuous in frequency with bandwidth being at least a minimum bandwidth but less than required to meet an occupied channel bandwidth limit.

8. A method of claim 5, wherein the first type of physical random access channel comprises resources continuous in frequency with a bandwidth being at least a minimum bandwidth but less than the bandwidth required to meet an occupied channel bandwidth limit.

9. A method of any one of claims 1 through 4, further comprising transmitting on a second type of physical random access channel, when there is no ongoing shared channel occupancy time.

10. A method of claim 9, wherein the second type of physical random access channel comprises PRACH Type 2.

11. A method of claim 10, wherein the PRACH Type 2 comprises resource continuous in frequency with bandwidth that meets an occupied channel bandwidth limit.

12. A method of claim 11, wherein the PRACH Type 2 comprises resource with bandwidth being constant over a duration of physical random access channel.

13. A method of claim 9, wherein the second type of physical random access channel comprises resource continuous in frequency with bandwidth that meets an occupied channel bandwidth limit.

14. A method of claim 13, wherein the second type of physical random access channel comprises resource with bandwidth being constant over a duration of physical random access channel.

15. A method of claim 12 or 14, wherein the bandwidth comprises a wider portion meeting the occupied channel bandwidth limit and a narrower portion not meeting the occupied channel bandwidth limit but is at least a minimum bandwidth.

16. An apparatus, comprising:

at least one processor; and

at least one memory comprising computer program code;

the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to

determine, at a user equipment, an ongoing channel occupancy time;

determine whether the ongoing channel occupancy time is shared with the user equipment;

select a physical random access channel type to be transmitted based on the determining of the ongoing channel occupancy time;

perform listen before talk associated with the selected physical random access channel type; and

transmit at least one random access channel signal on a physical random access channel, in case of successful listen before talk.

17. An apparatus of claim 16, wherein the shared ongoing channel occupancy time is shared with the user equipment from a network node.

18. An apparatus of claim 16 or 17, wherein the determining whether the ongoing channel occupancy time being shared with at least one user equipment is based on at least one of blind decoding of group common physical downlink control channel or detection of reference signal associated with a target cell.

19. An apparatus of any one of claims 16 through 18, wherein the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus to blind decode physical downlink control channel for random access response identified by random access radio network temporary identifier, based at least on the selected physical random access channel type.

20. An apparatus of any one of claims 16 through 19, wherein the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus to transmit on a first type of physical random access channel, when there is ongoing shared channel occupancy time.

21. An apparatus of claim 20, wherein the first type of physical random access channel comprises PRACH Type 1.

22. An apparatus of claim 21, wherein the PRACH Type 1 comprises resource continuous in frequency with bandwidth being at least a minimum bandwidth but less than required to meet an occupied channel bandwidth limit.

23. An apparatus of claim 20, wherein the first type of physical random access channel comprises resources continuous in frequency with a bandwidth being at least a minimum bandwidth but less than the bandwidth required to meet an occupied channel bandwidth limit.

24. An apparatus of any one of claims 16 through 19, wherein the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus to transmit on a second type of physical random access channel, when there is no ongoing shared channel occupancy time.

25. An apparatus of claim 24, wherein the second type of physical random access channel comprises PRACH Type 2.

26. An apparatus of claim 25, wherein the PRACH Type 2 comprises resource continuous in frequency with bandwidth that meets an occupied channel bandwidth limit.

27. An apparatus of claim 26, wherein the PRACH Type 2 comprises resource with bandwidth being constant over a duration of physical random access channel.

28. An apparatus of claim 24, wherein the second type of physical random access channel comprises resource continuous in frequency with bandwidth that meets an occupied channel bandwidth limit.

29. An apparatus of claim 28, wherein the second type of physical random access channel comprises resource with bandwidth being constant over a duration of physical random access channel.

30. An apparatus of claim 27 or 29, wherein the bandwidth comprises a wider portion meeting the occupied channel bandwidth limit and a narrower portion not meeting the occupied channel bandwidth limit but is at least a minimum bandwidth.

31. An apparatus, comprising:

means for determining an ongoing channel occupancy time;

means for determining whether the ongoing channel occupancy time is shared with at least one user equipment;

means for selecting a physical random access channel type to be transmitted based on the determining of the ongoing channel occupancy time;

means for performing listen before talk associated with the selected physical random access channel type; and

means for transmitting at least one random access channel signal on a physical random access channel, in case of successful listen before talk.

32. An apparatus comprising means for performing a method according to any one of claims 1 through 15.

33. A method, comprising:

determining, at a network node, whether there is a need to share at least one of channel occupancy time or transmission burst with one or more user

equipments;

when it is determined that there is the need to share at least one of channel occupancy time or transmission burst, performing listen before talk; in case of successful listen before talk, starting transmission of the at least one of channel occupancy time or transmission burst;

selecting a physical random access channel type to be detected;

detecting a physical random access channel with the selected physical random access channel type; and

transmitting random access response identified by random access radio network temporary identifier depending at least on the selected physical random access channel type.

34. A method of claim 33, further comprising transmitting at least one indicator on at least one of presence or structure of the shared at least one of channel occupancy time or transmission burst.

35. A method of claim 33 or 34, further comprising transmitting scheduling information to the one or more user equipments and causing the one or more user equipments to transmit a predefined reference signal at one or more predefined symbols with respect to physical random access channel occasion.

36. An apparatus, comprising:

at least one processor; and

at least one memory comprising computer program code;

the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to

determine, at a network node, whether there is a need to share at least one of channel occupancy time or transmission burst with one or more user

equipments;

when it is determined that there is the need to start the at least one of shared channel occupancy time or transmission burst, perform listen before talk;

in case of successful listen before talk, start transmission of the at least one of channel occupancy time or transmission burst;

select a physical random access channel type to be detected;

detect a physical random access channel with the selected physical random access channel type; and

transmit random access response identified by random access radio network temporary identifier depending at least on the selected physical random access channel type.

37. An apparatus of claim 36, wherein the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus to transmit at least one indicator on at least one of presence or structure of the shared at least one of channel occupancy time or transmission burst.

38. An apparatus of claim 36 or 37, wherein the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus to transmit scheduling information to the one or more user equipments and cause the one or more user equipments to transmit a predefined reference signal at one or more predefined symbol with respect to physical random access channel occasion.

39. An apparatus, comprising:

means for determining whether there is a need to share at least one of channel occupancy time or transmission burst with one or more user equipments; means for performing listen before talk, when it is determined that there is the need to share at least one of channel occupancy time or transmission burst; means for starting transmission of the at least one of channel occupancy time or transmission burst, in case of successful listen before talk;

means for selecting a physical random access channel type to be detected; means for detecting a physical random access channel with the selected physical random access channel type; and

means for transmitting random access response identified by random access radio network temporary identifier depending at least on the selected physical random access channel type.

40. An apparatus comprising means for performing a method according to any one of claims 33 through 35.

41. A non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a method according to any of claims 1 through 15 or perform a method according to any of claims 33 through 35.

42. A computer program product encoded with instructions for performing a method according to any of claims 1 through 15 or performing a method according to any of claims 33 through 35.

Description:
PHYSICAL RANDOM ACCESS CHANNEL ARRANGEMENT FOR NEW RADIO

UNLICENSED

FIELD:

[0001] Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE) or fifth generation (5G) radio access technology or new radio (NR) access technology. For example, certain embodiments may relate to physical random access channel (PRACH) transmission in such communication systems.

BACKGROUND:

[0002] Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE- Advanced (LTE-A), MulteFire, LTE-A Pro, and/or fifth generation (5G) radio access technology or new radio (NR) access technology. Fifth generation (5G) or new radio (NR) wireless systems refer to the next generation (NG) of radio systems and network architecture. It is estimated that NR will provide bitrates on the order of 10-20 Gbit/s or higher, and will support at least enhanced mobile broadband (eMBB) and ultra-reliable low-latency-communication (URLLC). NR is expected to deliver extreme broadband and ultra-robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and machine -to-machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. It is noted that, in 5G or NR, the nodes that can provide radio access functionality to a user equipment (i.e., similar to Node B in E- UTRAN or eNB in LTE) may be referred to as a next generation or 5G Node B (gNB).

BRIEF DESCRIPTION OF THE DRAWINGS:

[0003] For proper understanding of example embodiments, reference should be made to the accompanying drawings, wherein:

[0004] Fig. 1 illustrates PRACH preamble formats Al and A2/B2 within a slot together with two different starting symbols: #0 and #2, according to certain examples;

[0005] Fig. 2 illustrates an example of the determination of ongoing shared COT and corresponding PRACH type, according to an embodiment; [0006] Fig. 3a illustrates an example of PRACH Type 2, with PRACH Type 2A-8, according to an embodiment;

[0007] Fig. 3b illustrates an example of PRACH type 2B, according to one embodiment;

[0008] Fig. 4 illustrates an example of time domain relations of PUSCH, PRACH Type 1 and PRACH Type 2 within a slot, according to one embodiment;

[0009] Fig. 5 illustrates an example FDM of PUSCH and PRACH Type 1, according to an embodiment;

[0010] Fig. 6a illustrates an example flow diagram of a method, according to an embodiment;

[0011] Fig. 6b illustrates an example flow diagram of a method, according to another embodiment;

[0012] Fig. 7a illustrates an example block diagram of an apparatus, according to one embodiment; and

[0013] Fig. 7b illustrates an example block diagram of an apparatus, according to another embodiment.

DETAILED DESCRIPTION:

[0014] It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for PRACH transmission, for example in a NR unlicensed (NR-U) band scenario, is not intended to limit the scope of certain embodiments but is representative of selected example embodiments.

[0015] The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases“certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases“in certain embodiments,”“in some embodiments,”“in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments.

[0016] Additionally, if desired, the different functions or steps discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or steps may be optional or may be combined. As such, the following description should be considered as merely illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof.

[0017] The third generation partnership project (3GPP) has approved a study item related to NR-based access to unlicensed spectrum (RP-170828). Some example embodiments consider the case where a UE performs random access via unlicensed band. As a result, certain embodiments may be relevant at least for NR-Unlicensed stand-alone and Dual Connectivity (with LTE or NR anchor cell on licensed band) scenarios where PRACH transmission via unlicensed band may be needed.

[0018] In LTE licensed assisted access (LAA), two channel access (e.g., listen before talk (LBT)) procedures are defined, Type 1 (a variant of category 4 energy detection LBT procedure) and Type 2 (a variant of category 2 energy detection LBT procedure).

[0019] In Type 1 LBT, a node (such as gNB or UE) generates a random number N uniformly distributed over a contention window (where the size of contention window depends on the channel access priority class of the traffic). Once the node has measured the channel to be vacant for N times, it may occupy the channel with transmission. To align the transmission with the LTE subframe boundary, the node may need to resort to self-deferral, i.e., delay the start of the transmission, during the LBT procedure.

[0020] In Type 2 LBT, a node performs a single channel measurement in time interval of 25 us before transmission. For physical uplink shared channel (PUSCF1), this type of LBT may be performed when an eNB shares its channel occupancy time (COT) with the UE. In other words, the eNB has contended for the channel and once the eNB has obtained access to the channel, it allows UEs to use a portion of its channel occupancy time for UL transmissions.

[0021] For NR-unlicensed scenarios, it may be attractive to also support UL transmission with Type 2 LBT within a gNB acquired COT, as it efficiently supports scheduled UL as well as UL frequency division multiple access (FDMA). A UE may also skip the LBT procedure for UL control signalling within base station acquired COT if UL transmission starts within 16 us after the end of downlink (DL) transmission. This approach is being used in MulteFire.

[0022] NR Release- 15 (Rel-15) supports both long and short sequence based PRACH preambles. Sequence length for long sequence based is 839, and for short sequence based is 139. Preamble formats using long sequence are targeted to macro, extended coverage and long-range deployments to support up to 100 km cell radius. Short sequences are introduced to support efficient small cell deployments and beam sweeping required especially at above 6 GHz. In addition, short sequence based PRACH preamble formats have the same subcarrier spacing options (namely 15 and 30 kHz at below 6 GHz, and 60 and 120 kHz at above 6 GHz) as other uplink channels, such as NR-PUCCH and NR- PUSCH, allowing a gNB receiver to use the same fast Fourier transform (FFT) to receive simultaneously PRACH and other uplink signals multiplexed in frequency domain.

[0023] A short sequence based preamble format may be defined as follows: preamble format includes one or multiple random access preamble(s), a random access preamble includes one preamble sequence and a cyclic prefix (CP), and a preamble sequence includes one or multiple PRACH OFDM symbol(s). RACH occasion (RO) is defined as the time -frequency resources on which PRACH preamble is transmitted using the configured PRACH preamble format.

[0024] Table 1 shows an example of the base formats for short sequence based PRACH preambles. There are nine base formats as shown in Table 1. Given the base formats, ten different formats can be configured: Al, A2, A3, Bl, B4, CO, C2, Al/Bl, A2/B2 and A3/B3. In Ax/Bx formats all but last preamble use Ax format and the last preamble in a slot uses format Bx. There are multiple configuration options per each format (one configuration can be active at a time in a cell) to support different starting symbol options within a slot and thus different number of RACH occasions within the slot for the certain preamble format. As an example, Fig. 1 illustrates PRACH preamble formats Al and A2/B2 within a slot together with two different starting symbols: #0 and #2.

TABLE 1

[0025] At least two regulatory requirements should be considered in the context of NR-unlicensed PRACH design. These requirements include a limit for maximum PSD, e.g. 10 dBm/MHz, and occupied channel bandwidth (OCB), requiring for example that transmission bandwidth (BW) is at least 80% of nominal channel BW, which typically is assumed to be 20 MHz (e.g. when operating at 2.4 GHz or 5 GHz carrier frequency bands). The former easily limits the maximum transmission power, while the latter means that a transmission with 16 MHz BW (for the typical 20 MHz nominal BW, corresponding to the bandwidth of, e.g., Wi-Fi channel) is needed. However, regulations allow transmission BW to be temporarily less than the 80% of the nominal BW but at least 2 MHz within a channel occupancy time (COT). It is noted that ETSI EN 301893 is a European standard that provides the definition and limits of the nominal channel bandwidth and occupied channel bandwidth, respectively.

[0026] Due to at least these requirements, it is challenging to design a PRACH that facilitates robust detection and timing estimation, supporting sufficient coverage for NR unlicensed, has sufficient multiplexing capacity of preambles, uses radio resources efficiently, can be flexibly placed within UL burst, and has synergy with licensed carrier PRACH detection.

[0027] Some example embodiments can provide a PRACH solution that facilitates robust detection and timing estimation. In addition, certain example embodiments can be flexibly multiplexed on the UL portion of COT in parallel with PUSCH, and meet OCB requirements when needed.

[0028] One embodiment may include that the PRACH type depends on whether it is transmitted within a gNB acquired COT / transmission burst or as an UE acquired COT / Tx burst. It is noted that gNB or UE acquired COT means that the gNB or UE, respectively, has performed the necessary channel contention, acquired access to the channel, and started COT. Also, COT may be understood as a transmission burst, which in case that COT is shared between a gNB and UE(s), contains transmissions both from the gNB and UE(s).

[0029] In an embodiment, a UE may determine whether or not there is an ongoing shared COT acquired by the target gNB, that the gNB is sharing with the UE. Based on that determination, the UE may further determine the PRACH type that it uses in the PRACH transmission.

[0030] According to certain embodiments, for the determination of ongoing shared COT, a UE may determine the presence of ongoing COT (and whether the COT is shared with UEs, i.e., includes an UL part) acquired by the gNB based on blind decoding of group common physical downlink control channel (GC-PDCCH) and/or based on the detection of a reference signal (e.g., PDCCH demodulation reference signal (DMRS), Channel State Information Reference Signal (CSI-RS), a wake-up signal, or UL sounding reference signal (SRS)) associated with the target cell. In an example embodiment, the determination of ongoing COT may relate to detection of DL portion of the COT only. In another example embodiment, the determination of ongoing COT may also cover detection of the UL portion of the COT. This can be based on predefined reference signal (RS), such as SRS, located at predefined symbol(s) with respect to PRACH opportunity.

[0031] In some example embodiments, if there is an ongoing shared COT, a UE may transmit a first PRACH type, for example PRACH of Type 1. For instance, the Type 1 PRACH may have characteristics including that it is continuous in frequency and has a bandwidth (BW) that is at least the minimum bandwidth (e.g., 2 MHz) but is less than required to meet the OCB limit (e.g., 16 MHz). As one example embodiment, PRACH of Type 1 may be similar to a Rel-15 NR PRACH structure.

[0032] In other example embodiments, if there is no ongoing shared COT, a UE may transmit a second PRACH type, for example PRACH of Type 2. For example, the Type 2 PRACH may have characteristics including that it is continuous in frequency and has a bandwidth that meets the OCB limit (e.g., 16 MHz). According to one example, the bandwidth may be constant over the duration of PRACH, or it may have a wider portion meeting the OCB limit and a narrower portion not meeting the OCB limit but is at least the minimum bandwidth (e.g., 2 MHz).

[0033] In another example, a first subset of the second PRACH type, for example Type 2A PRACH, may have continuously wide BW. According to some examples, the preamble may be similar to a Rel-l5 NR PRACH structure with a longer sequence and wider BW, or the preamble may be composed of multiple Rel-l5 NR short sequence PRACH preambles stacked in frequency to form a single wide BW PRACH preamble. Stacking may involve also predefined selection of the cyclic shifts and/or base sequences for different portions of the stacked preamble. This allows to keep the cubic metric (CM) and peak-to-average power ratio (PAPR) of the preamble sequence at a reasonable level. Additionally, the PRACH Type 2 A may have shorter duration and may be transmitted on higher power than the PRACH of Type 1 (wide BW provides increased transmit (Tx) power under conditions where transmission power is limited by the maximum PSD and also increased processing gain when longer sequence is used).

[0034] In yet another example, in a second subset of the second PRACH type, for example Type 2B PRACH, a UE may transmit a wideband signal meeting the OCB (e.g., containing SRS or other reference signal and possibly related data like CSI or UE buffer status report, RRC connection request message, and/or UE identity) either before or after a narrower Rel-l5 NR PRACH preamble or PRACH of Type 1. Additionally, in one example, the PRACH starting time for Type 2B PRACH may be somewhat (e.g., a symbol) later than with the PRACH Type 1.

[0035] An example embodiment is based on the realization that when PRACH is transmitted as part of gNB acquired shared COT, the OCB may be seen to be fulfilled by a preceding DL or UL transmission and the bandwidth of PRACH may temporarily be less than the OCB requirement. This allows for PRACH preamble continuous in frequency (hence supporting simple and reliable timing estimation and use of the same receiver structure as for PRACH in licensed NR), while PRACH preamble is narrow enough to support FDMA with PUSCH as it does not occupy an unnecessarily large number of physical resource blocks (PRBs). On the other hand, when PRACH is transmitted outside of gNB acquired shared COT, it needs to meet the OCB requirement. However, if there are no other ongoing scheduled transmissions, occupying a wide continuous resource in frequency domain does not pose any problems.

[0036] As discussed in the foregoing, a UE may determine the presence of an ongoing shared COT, for example, based on blind decoding of GC-PDCCH and/or detection of reference signal(s) associated with a target cell. In one embodiment, the determination of the ongoing shared COT may relate to just the detection of DL portion of the COT. In this embodiment, the reference signal may be part of a DL preamble (e.g., using PSS or SSS signals) or wake-up signal or it may be DMRS (e.g., PDCCH DMRS), TRS or CSI-RS. The reference signal may be transmitted at the beginning of COT or periodically within the COT. In one example, the UE may determine the COT by detecting predefined RS(s) associated to the target cell. If the RS is detected, the UE may additionally decode GC- PDCCH. Based on the GC-PDCCH, the UE can determine whether the COT acquired by the gNB is shared with UEs, and in which slot(s) PRACH Type 1 transmission is allowed. A benefit of this approach is that COT detection can be based on existing signals (considered for NR-U). On the other hand, the UE should already be awake during DL portion of the COT in order to determine the presence of the COT and its structure . In certain embodiments, a COT structure may include, for example, COT duration or presence of UL portion within the COT, indicating that the COT is a shared COT.

[0037] In another embodiment, the determination of the presence of an ongoing COT covers detection of both DL and UL portions of the COT. According to this embodiment, a time -offset based approach can be used in the cases when COT detection also covers the UL portion of the COT. As an example, the UE may test the presence of DL CSI-RS (or other predefined DL RS/signal) and/or predetermined UL SRS at predetermined symbols in a slot preceding PRACH resource. A benefit of this approach is that a UE can wake-up just a slot or two before PRACH. On the other hand, this requires that UE(s) transmitting within UL portion of the COT are transmitting the predetermined SRS during the predefined symbols. Additionally, UE(s) may not transmit the predetermined SRS during the predefined symbols preceding a periodic PRACH occasion when the UE itself has acquired and started the COT (with Type 1 LBT). Lig. 2 illustrates an example of the determination of ongoing shared COT and corresponding PRACH type, according to an embodiment.

[0038] According to an embodiment, periodical time domain resources for PRACH Type 1 and Type 2 can be configured by means of higher layer signalling such as SIB1 or dedicated higher layer signalling. Lor PRACH Type 1, group-common PDCCH can be used to dynamically schedule additional (opportunistic) PRACH resources within the COT. hollowing this option, opportunistic PRACH resources can be located, for example, on predefined symbols with respect to indicated UL portion start of the COT. Lor instance, there may be a set of possible RACH resource configurations defined for the UL portion of the COT and group-common PDCCH provides an index to the configuration to be applied within the COT. [0039] In one embodiment, PRACH Type 1 may follow NR Rel-l5 PRACH formats. Examples of such formats are tabulated in Table 2 together with Tx bandwidth as well as maximum Tx power allowed under 10 dBm/MHz limit.

TABLE 2

5 [0040] Examples for PRACH Type 2 A are shown in Table 3. Formats 2A-1, 2A-2,

2A-3 are based on use of higher SCS value to reach a bandwidth meeting the OCB requirement. Formats 2A-4, 2A-5, 2A-6 use longer sequence to widen the Tx bandwidth. In formats 2A-7, 2A-8, 2A-9, Rel-l5 NR PRACH may be duplicated and stacked in frequency to create a wide bandwidth PRACH. Fig. 3a illustrates an example of PRACH 10 Type 2, with PRACH Type 2A-8, according to an embodiment. It is noted that this kind of stacked preamble structure may typically have increased PAPR/CM and UE Tx power may become limited before the maximum Tx power based on PSD limit. Furthermore, as discussed in the foregoing, there may be means available to reduce PAPR/CM related to the stacked preamble structure. Formats 2A-1 to 2A-6 do not have this issue. The

15 examples in Tables 2 and 3 use NR Rel-l5 sequence length of 139 as based, but formats based on the NR Rel-l5 sequence length of 839 (or other sequence lengths) may also be created according to other embodiments.

TABLE 3 [0041] It should be noted that a rather high Tx power, e.g., 22 dBm, may be allowed for PRACH Type 2A examples in Table 3, while 3 dB or 6 dB lower Tx power may be allowed for PRACH Type 1 examples in Table 2 when PSD limit of 10 dBm/MHz is followed. The power difference may be compensated for by using a PRACH Type 1 5 format that is 2x or 4x longer than the used PRACH Type 2A format. Examples of such pairings are shown in Table 4.

[0042] Correspondingly, there may be a Tx power offset between Types 1 and 2A (i.e., not only in case of maximum allowed Tx power). Tx power offset may be predetermined, may be configured by RRC (though cell specific), or may be determined 10 by UE based on the ratio of Type 1 and 2A preamble durations.

[0043] In an embodiment, the LBT type that the UE applies before the PRACH transmission may depend on the selected PRACH type, or vice versa. For example, if PRACH Type 1 is selected, the UE may apply (LTE LA A) Type 2 LBT or even skip the LBT, if the gNB indicates that the gap between transmissions is less than 16 us. The CP 15 length may be adjusted to support 16 us or 25 us gap while keeping the preamble starting time relative to the DL CP-OFDM symbol boundary fixed. As another example, if PRACH Type 2 is selected, the UE may apply (LTE LA A) Type 1 LBT or Type 2 LBT predetermined in specifications.

20 [0044] According to an embodiment, in PRACH Type 2B, a UE may transmit a wideband signal that meets the OCB requirement either before or after a PRACH of Type 1. The wideband signal may be, for example, SRS with interlaced (or block-IFDMA) structure, or with IFDMA structure or with a combined structure of block-IFDMA and IFDMA. Fig. 3b illustrates an example of PRACH type 2B, according to one embodiment. [0045] According to an example embodiment, PRACH Type 2 may be transmitted somewhat later, for example a PUSCH OFDM symbol later, than PRACH with Type 1. This reduces the error cases when a UE does not detect the ongoing COT and intends to transmit with PRACH Type 2. Due to the starting time difference, possible PRACH transmissions with Type 1 or PUSCH transmissions from other UEs may block LBT and prevent PRACH Type 2 transmission. As the PRACH Type 2 duration is shorter than with PRACH Type 1, PRACH Type 2 does not exceed the PRACH Type 1 resources in time even when delayed a symbol. Fig. 4 illustrates an example of time domain relations of PUSCH, PRACH Type 1 and PRACH Type 2 within a slot, according to one embodiment.

[0046] In one embodiment, to avoid error propagation in random access procedure (due to PRACH transmission with wrong structure), non-overlapping RA-RNTI sets are associated with PRACH types A and B. For example, the carrier indication in Rel-15 NR RA-RNTI may be used to indicate the PRACH type that gNB detected. According to an example embodiment, RA-RNTI may be given by:

RA-RNTI= 1 + s_id + 14 x t_id + 14 x 80 x f_id + 14 x 80 x 8 x PRACH_structure_id, where s_id is the index of the first OFDM symbol of the specified PRACH (0 < s_id < 14), t_id is the index of the first slot of the specified PRACH in a system frame (0 < t_id < 80), f_id is the index of the specified PRACH in the frequency domain (0 < f_id < 8), and PRACH_structure_id is the PRACH type used for Msgl detection (0 for PRACH Type 1, and 1 for PRACH Type 2).

[0047] It may be advantageous that periodic PRACH can occur anywhere within the UL portion of gNB acquired COT, as it allows for added flexibility in DL/UL partitioning. For that, it should be possible to FDM PRACH with PUSCH. If just TDM is supported between PRACH and PUSCH, and when there is no PRACH transmission, there is a considerable gap in the transmission burst, causing a risk of losing channel to another equipment contending for channel access during the empty PRACH.

[0048] It is noted that a simple and robust timing estimation requires sufficient continuous frequency allocation of a few MHz. A normal block-IFDMA PRACH design, supporting timing estimation and meeting OCB with a single PRACH type would mean interlaced structure with cluster bandwidth of 1-4 MHz. This kind of interlace structure would easily use excessive amount of resources. Further, such interlace structure would be inefficient for PUSCH, meaning that PRACH and PUSCH would use different and incompatible interlace structures. FDMA of PUSCH and PRACH (with incompatible interlaces) would lead to cumbersome and easily inefficient multiplexing. PUSCH FDMA with PRACH Type 2 A would be limited as there is roughly 2 MHz left after PRACH - this is sufficient only for 1 PUSCH. On the other hand, PRACH Type 2A may be short, meaning that 20 MHz of PUSCH resources until next LBT gap, e.g., end of slot are allocated to a single UE. In case of PUSCH FDMA with PRACH Type 2B, wideband SRS should be multiplexed with parallel PUSCHs. This is possible, for example, with IFDMA structure, but may be somewhat wasteful in the radio resource usage.

[0049] Fig. 5 illustrates an example FDM of PUSCH and PRACH Type 1, according to an embodiment. The multiplexing can support both localized and interlaced PUSCH allocations. PUSCH interlaces may be temporally truncated in frequency and mini slot/shortened PUSCH allocations may be used to multiplex PUSCH and PRACH within a slot in time.

[0050] Certain example embodiments may introduce a new error case, where a UE transmits PRACH with a wrong structure. However, as discussed below, that will not cause significant errors. Under an error case A, the UE fails to detect ongoing COT and transmits PRACH Type 2. In several cases, the PRACH EBT will fail and prevent erroneous transmission as parallel UE transmissions start earlier. If PRACH LBT succeeds, transmission may overlap with PUSCH and PRACH. This will cause interference to the detection and increase possibility of retransmissions. In this case, the gNB will not detect PRACH transmission, causing PRACH to be transmitted again. Under an error case B, the UE may detect ongoing COT although there is none. This is a highly unlikely error (especially when using CRC -protected GC-PDCCH for determining the ongoing COT). In this case, the UE may transmit PRACH with wrong format. It will block or interfere other potential PRACH transmissions, possibly causing them to be transmitted again. Also, the UE may need to transmit PRACH again.

[0051] Fig. 6a illustrates an example flow diagram of a method 600, according to an embodiment. In one embodiment, the method 600 may include a method for selecting and transmitting a PRACH structure type in NR-U, according to one embodiment. In certain embodiments, the method of Fig. 6 may be performed by a UE, mobile station, mobile equipment, IoT device, or the like, for example. As illustrated in the example of Fig. 6, the method 600 may include, at 610, determining that there is an ongoing COT acquired by the gNB, for example, based on blind decoding of GC-PDCCH and/or based on the detection of reference signal(s), such as DL RS and/or UL RS, associated with the target cell. In an embodiment, the method may also include, at 620, determining whether the gNB-acquired COT is shared with one or more UE(s), i.e., has an UL part. For instance, the determining 620 may include detecting or attempting to detect an UL RS. In one example, the detection of GC-PDCCH may also provide additional opportunistic resources available for PRACH. According to certain example embodiments, the determining 620 of whether the gNB-acquired COT is shared with UE(s) may include, for example: getting an indication of the shared UL slots, e.g., from the GC-PDCCH, and/or receiving a RRC configuration indicating that every gNB acquired COT (or a predefined subset of all gNB acquired COTs) is shared with UE(s), such that there is at least a short UL part for transmission of PRACH and possibly other signals.

[0052] Based on the determination of the presence of ongoing COT acquired by the gNB, the method 600 may also include, at 630, selecting the PRACH type to be transmitted. In an embodiment, the PRACH types may have differences in bandwidth, duration, timing, transmission power and, possibly, in the LBT applied before the transmission. In certain embodiments, the method 600 may also include, at 640, performing the LBT associated with the selected PRACH type and, in case of successful LBT (channel is vacant), transmitting the PRACH. In some examples, if there is an ongoing shared COT, PRACH of Type 1 may be transmitted. In other examples, if there is no ongoing shared COT, PRACH of Type 2 may be transmitted. According to one embodiment, the method 600 may further include, at 650, blind decoding PDCCH for RAR identified by RA-RNTI depending (among other aspects), for example, at least on the selected PRACH type.

[0053] Pig. 6b illustrates an example flow diagram of a method 601, according to an embodiment. In one embodiment, the method 601 may include a method for selecting and detecting a PRACH structure type in NR-U. In certain embodiments, the method of Pig. 6b may be performed by a network node, such as a base station, gNB, or the like, for example. As illustrated in the example of Pig. 6b, the method 601 may include, at 660, determining whether there is a need to start a COT / transmission burst shared with one or more UE(s), i.e., having an UL part. The determining 660 may be based, for example, on a presence of DL data or control information to be transmitted, and/or on knowledge that UEs have UL data or control information to transmit. In an embodiment, the determining 660 may further include determining that the shared COT / transmission burst contains a random access opportunity. Based on the determination that there is the need to start the shared COT / transmission burst, the method may then include, at 670, performing the LBT and, in case of successful LBT (channel is vacant), starting the transmission of COT / transmission burst. In an embodiment, the method may also include, at 675, transmitting indicator(s) on the presence and/or structure of the shared COT/ transmission burst, for example, by transmitting reference signal(s), preamble, or wakeup signal associated with the target cell. The indicators may be transmitted also, for instance, as part of GC-PDCCH or RRC configuration indicating that every gNB acquired COT (or a predefined subset of all gNB acquired COTs) is shared with UE(s), such that there is at least a short UL part for transmission of PRACH and possibly other signals. In some examples, the method may additionally or alternatively include, at 675, transmitting scheduling information to one or more UE(s) to transmit a predefined reference signal (RS), e.g. a predefined SRS, at predefined symbol(s) with respect to PRACH occasion.

[0054] In certain embodiments, the method may also include, at 680, selecting the PRACH type to be detected and, at 685, detecting PRACH with the selected PRACH type. The method may then include, at 690, transmitting RAR identified by RA-RNTI depending at least on the selected PRACH type. It is noted that, in some embodiments described herein, COT may refer to transmission burst or a duration of transmission (as channel occupancy time).

[0055] Fig. 7a illustrates an example of an apparatus 10 according to an embodiment. In an embodiment, apparatus 10 may be a node, host, or server in a communications network or serving such a network. For example, apparatus 10 may be a base station, a Node B, an evolved Node B (eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB), WLAN access point, mobility management entity (MME), and/or subscription server associated with a radio access network, such as a GSM network, LTE network, 5G or NR.

[0056] It should be understood that, in some example embodiments, apparatus 10 may be comprised of an edge cloud server as a distributed computing system where the server and the radio node may be stand-alone apparatuses communicating with each other via a radio path or via a wired connection, or they may be located in a same entity communicating via a wired connection. For instance, in certain example embodiments where apparatus 10 represents a gNB, it may be configured in a central unit (CU) and distributed unit (DU) architecture that divides the gNB functionality. In such an architecture, the CU may be a logical node that includes gNB functions such as transfer of user data, mobility control, radio access network sharing, positioning, and/or session management, etc. The CU may control the operation of DU(s) over a front-haul interface. The DU may be a logical node that includes a subset of the gNB functions, depending on the functional split option. It should be noted that one of ordinary skill in the art would understand that apparatus 10 may include components or features not shown in Fig. 7a.

[0057] As illustrated in the example of Fig. 7a, apparatus 10 may include a processor 12 for processing information and executing instructions or operations. Processor 12 may be any type of general or specific purpose processor. In fact, processor 12 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application- specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 12 is shown in Fig. 7a, multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain embodiments, apparatus 10 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 12 may represent a multiprocessor) that may support multiprocessing. In certain embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

[0058] Processor 12 may perform functions associated with the operation of apparatus 10, which may include, for example, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes related to management of communication resources.

[0059] Apparatus 10 may further include or be coupled to a memory 14 (internal or external), which may be coupled to processor 12, for storing information and instructions that may be executed by processor 12. Memory 14 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semi conductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 14 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (F1DD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 may include program instructions or computer program code that, when executed by processor 12, enable the apparatus 10 to perform tasks as described herein.

[0060] In an embodiment, apparatus 10 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 12 and/or apparatus 10.

[0061] In some embodiments, apparatus 10 may also include or be coupled to one or more antennas 15 for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 may further include or be coupled to a transceiver 18 configured to transmit and receive information. The transceiver 18 may include, for example, a plurality of radio interfaces that may be coupled to the antenna(s) 15. The radio interfaces may correspond to a plurality of radio access technologies including one or more of GSM, NB- IoT, LTE, 5G, WLAN, Bluetooth, BT-LE, NFC, radio frequency identifier (RFID), ultrawideband (UWB), MulteFire, and the like. The radio interface may include components, such as filters, converters (for example, digital-to-analog converters and the like), mappers, a Fast Fourier Transform (FFT) module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols (for example, via an uplink).

[0062] As such, transceiver 18 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 15 and demodulate information received via the antenna(s) 15 for further processing by other elements of apparatus 10. In other embodiments, transceiver 18 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 10 may include an input and/or output device (I/O device).

[0063] In an embodiment, memory 14 may store software modules that provide functionality when executed by processor 12. The modules may include, for example, an operating system that provides operating system functionality for apparatus 10. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 10. The components of apparatus 10 may be implemented in hardware, or as any suitable combination of hardware and software.

[0064] According to some embodiments, processor 12 and memory 14 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 18 may be included in or may form a part of transceiving circuitry.

[0065] As used herein, the term“circuitry” may refer to hardware -only circuitry implementations (e.g., analog and/or digital circuitry), combinations of hardware circuits and software, combinations of analog and/or digital hardware circuits with software/firmware, any portions of hardware processor(s) with software (including digital signal processors) that work together to case an apparatus (e.g., apparatus 10) to perform various functions, and/or hardware circuit(s) and/or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation. As a further example, as used herein, the term“circuitry” may also cover an implementation of merely a hardware circuit or processor (or multiple processors), or portion of a hardware circuit or processor, and its accompanying software and/or firmware. The term circuitry may also cover, for example, a baseband integrated circuit in a server, cellular network node or device, or other computing or network device.

[0066] As introduced above, in certain embodiments, apparatus 10 may be a network node or RAN node, such as a base station, access point, Node B, eNB, gNB, WLAN access point, or the like. According to certain embodiments, apparatus 10 may be controlled by memory 14 and processor 12 to perform the functions associated with any of the embodiments described herein. For example, in some embodiments, apparatus 10 may be configured to perform one or more of the processes depicted in any of the flow charts or signaling diagrams described herein, such as the flow diagrams illustrated in Figs. 6a or 6b. In certain embodiments, apparatus 10 may be configured to perform a procedure for selecting and detecting a PRACH structure type, for example, in NR-U.

[0067] In one embodiment, apparatus 10 may be controlled by memory 14 and processor 12 to determine whether there is a need to start a COT / transmission burst shared with one or more UE(s), i.e., having an UL part. The determination of the need to start a COT / transmission burst may be based, for example, on a presence of DL data or control information to be transmitted, and/or on knowledge that UEs have UL data or control information to transmit. In an embodiment, apparatus 10 may be further controlled by memory 14 and processor 12 to determine that the shared COT / transmission burst contains a random access opportunity. Based on the determination that there is the need to start the shared COT / transmission burst, apparatus 10 may be controlled by memory 14 and processor 12 to perform the LBT and, in case of successful LBT (channel is vacant), start the transmission of COT / transmission burst.

[0068] In an embodiment, apparatus 10 may be controlled by memory 14 and processor 12 to transmit indicator(s) on the presence and/or structure of the shared COT/ transmission burst, for example, by transmitting reference signal(s), preamble, or wakeup signal associated with the target cell. The indicators may be transmitted also, for example, as part of GC-PDCCH or RRC configuration indicating that every gNB acquired COT (or a predefined subset of all gNB acquired COTs) is shared with UE(s), such that there is at least a short UL part for transmission of PRACH and possibly other signals. In some examples, apparatus 10 may be controlled by memory 14 and processor 12 to additionally or alternatively transmit scheduling information to one or more UE(s) to transmit a predefined reference signal (RS), e.g., a predefined SRS, at predefined symbol(s) with respect to PRACH occasion. In certain embodiments, apparatus 10 may also be controlled by memory 14 and processor 12 to select the PRACH type to be detected and to detect PRACH with the selected PRACH type. According to one embodiment, apparatus 10 may be further controlled by memory 14 and processor 12 to transmit RAR identified by RA- RNTI depending at least on the selected PRACH type.

[0069] Fig. 7b illustrates an example of an apparatus 20 according to another embodiment. In an embodiment, apparatus 20 may be a node or element in a communications network or associated with such a network, such as a UE, mobile equipment (ME), mobile station, mobile device, stationary device, IoT device, or other device. As described herein, UE may alternatively be referred to as, for example, a mobile station, mobile equipment, mobile unit, mobile device, user device, subscriber station, wireless terminal, tablet, smart phone, IoT device or NB-IoT device, or the like. As one example, apparatus 20 may be implemented in, for instance, a wireless handheld device, a wireless plug-in accessory, or the like.

[0070] In some example embodiments, apparatus 20 may include one or more processors, one or more computer-readable storage medium (for example, memory, storage, or the like), one or more radio access components (for example, a modem, a transceiver, or the like), and/or a user interface. In some embodiments, apparatus 20 may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and/or any other radio access technologies. It should be noted that one of ordinary skill in the art would understand that apparatus 20 may include components or features not shown in Fig. 7b.

[0071] As illustrated in the example of Fig. 7b, apparatus 20 may include or be coupled to a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. In fact, processor 22 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 22 is shown in Fig. 7b, multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain embodiments, apparatus 20 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 22 may represent a multiprocessor) that may support multiprocessing. In certain embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

[0072] Processor 22 may perform functions associated with the operation of apparatus 20 including, as some examples, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 20, including processes related to management of communication resources.

[0073] Apparatus 20 may further include or be coupled to a memory 24 (internal or external), which may be coupled to processor 22, for storing information and instructions that may be executed by processor 22. Memory 24 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semi conductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 24 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (F1DD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 24 may include program instructions or computer program code that, when executed by processor 22, enable the apparatus 20 to perform tasks as described herein.

[0074] In an embodiment, apparatus 20 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 22 and/or apparatus 20.

[0075] In some embodiments, apparatus 20 may also include or be coupled to one or more antennas 25 for receiving a downlink signal and for transmitting via an uplink from apparatus 20. Apparatus 20 may further include a transceiver 28 configured to transmit and receive information. The transceiver 28 may also include a radio interface (e.g., a modem) coupled to the antenna 25. The radio interface may correspond to a plurality of radio access technologies including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, and the like. The radio interface may include other components, such as filters, converters (for example, digital-to-analog converters and the like), symbol demappers, signal shaping components, an Inverse Fast Fourier Transform (IFFT) module, and the like, to process symbols, such as OFDMA symbols, carried by a downlink or an uplink.

[0076] For instance, transceiver 28 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 25 and demodulate information received via the antenna(s) 25 for further processing by other elements of apparatus 20. In other embodiments, transceiver 28 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 10 may include an input and/or output device (I/O device). In certain embodiments, apparatus 20 may further include a user interface, such as a graphical user interface or touchscreen.

[0077] In an embodiment, memory 24 stores software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for apparatus 20. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 20. The components of apparatus 20 may be implemented in hardware, or as any suitable combination of hardware and software. According to an example embodiment, apparatus 20 may optionally be configured to communicate with apparatus 10, which may represent one or more access nodes or base stations, such as an eNB or gNB, via a wireless or wired communications link 70 according to any radio access technology, such as 5G or NR.

[0078] According to some embodiments, processor 22 and memory 24 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 28 may be included in or may form a part of transceiving circuitry.

[0079] As used herein, the term“circuitry” may refer to hardware -only circuitry implementations (e.g., analog and/or digital circuitry), combinations of hardware circuits and software, combinations of analog and/or digital hardware circuits with software/firmware, any portions of hardware processor(s) with software (including digital signal processors) that work together to case an apparatus (e.g., apparatus 10) to perform various functions, and/or hardware circuit(s) and/or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation. As a further example, as used herein, the term“circuitry” may also cover an implementation of merely a hardware circuit or processor (or multiple processors), or portion of a hardware circuit or processor, and its accompanying software and/or firmware. The term circuitry may also cover, for example, a baseband integrated circuit in a server, cellular network node or device, or other computing or network device.

[0080] As discussed above, according to some embodiments, apparatus 20 may be a UE, mobile device, mobile station, ME, IoT device and/or NB-IoT device, for example. According to certain embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to perform the functions associated with example embodiments described herein. For example, in some embodiments, apparatus 20 may be configured to perform one or more of the processes depicted in any of the flow charts or signaling diagrams described herein, such as the flow diagrams illustrated in Figs. 6a or 6b.

[0081] According to some embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to determine the presence of ongoing COT acquired by a gNB based on blind decoding of GC-PDCCH and/or based on the detection of reference signal(s), such as DL RS or UL RS, associated with a target cell. In an embodiment, apparatus 20 may also be controlled by memory 24 and processor 22 to determine whether the gNB- acquired COT is shared with UE(s), i.e., has an UL part. In one example, the detection of GC-PDCCH may also provide additional opportunistic resources available for PRACH. According to some example embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to determine whether the gNB -acquired COT is shared with UE(s), for example, by: receiving an indication of the shared UL slot, e.g., from the GC-PDCCH, and/or receiving a RRC configuration indicating that every gNB acquired COT (or a predefined subset of all gNB acquired COTs) is shared with UE(s), such that there is at least a short UL part for transmission of PRACH and possibly other signals.

[0082] Based on the determination of the presence of ongoing COT acquired by the gNB, apparatus 20 may be controlled by memory 24 and processor 22 to select the PRACH type to be transmitted. In an embodiment, the structures may have differences in BW, duration, timing, transmission power and, possibly, in the LBT applied before the transmission. In certain embodiments, apparatus 20 may be further controlled by memory 24 and processor 22 to perform the LBT associated with the selected PRACH type and, in case of successful LBT (channel is vacant), to transmit the PRACH. In certain examples, if there is an ongoing shared COT, PRACH of Type 1 may be transmitted. For instance, the Type 1 may have characteristics that it is continuous in frequency and has BW that is at least the minimum BW (e.g., 2 MHz) but is less than required to meet OCB limit (e.g. 16 MHz). In other examples, if there is no ongoing shared COT, PRACH of Type 2 may be transmitted. For example, the Type 2 has characteristics that it is continuous in frequency and has BW that meets the OCB limit (e.g., 16 MHz). According to one example, the BW may be constant over the duration of PRACH (e.g., Type 2A discussed in detail above), or it may have a wider portion meeting the OCB limit and narrower portion not meeting OCB limit but is at least the minimum BW (e.g., Type 2B discussed in detail above).

[0083] According to one embodiment, apparatus 20 may also be controlled by memory 24 and processor 22 to blind decode PDCCH for RAR identified by RA-RNTI depending at least on the selected PRACH type.

[0084] Therefore, certain example embodiments provide several technical improvements, enhancements, and/or advantages. Various example embodiments can, for example, provide PRACH type(s) for NR-U. Some example embodiments can facilitate robust detection and timing estimation due to sufficient continuous frequency allocation, supporting sufficient coverage for NR unlicensed. An embodiment has synergy PRACH detection with licensed carrier. Additionally, when transmitted on gNB acquired shared COT, embodiments can be flexibly FDM with PUSCH. This prevents long transmission gaps due to absence of any PRACH transmission on PRACH resources. This also allows for more flexible UL/DL partitioning of transmission burst. Also, some embodiments have sufficient multiplexing capacity of preambles and use radio resources efficiently. Consequently, certain example embodiments can reduce overhead and improve the reliability and speed of networks. As such, example embodiments can improve performance, latency, and/or throughput of networks and network nodes including, for example, access points, base stations/eNBs/gNBs, and mobile devices or UEs. Accordingly, the use of certain example embodiments results in improved functioning of communications networks and their nodes.

[0085] In some example embodiments, the functionality of any of the methods, processes, signaling diagrams, algorithms or flow charts described herein may be implemented by software and/or computer program code or portions of code stored in memory or other computer readable or tangible media, and executed by a processor.

[0086] In some example embodiments, an apparatus may be included or be associated with at least one software application, module, unit or entity configured as arithmetic operation(s), or as a program or portions of it (including an added or updated software routine), executed by at least one operation processor. Programs, also called program products or computer programs, including software routines, applets and macros, may be stored in any apparatus-readable data storage medium and include program instructions to perform particular tasks.

[0087] A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out some example embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of an example embodiment may be performed as routine(s), which may be implemented as added or updated software routine(s). Software routine(s) may be downloaded into the apparatus.

[0088] As an example, software or a computer program code or portions of it may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium.

[0089] In other example embodiments, the functionality may be performed by hardware or circuitry included in an apparatus (e.g., apparatus 10 or apparatus 20), for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functionality may be implemented as a signal, a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

[0090] According to an example embodiment, an apparatus, such as a node, device, or a corresponding component, may be configured as circuitry, a computer or a microprocessor, such as single -chip computer element, or as a chipset, including at least a memory for providing storage capacity used for arithmetic operation and an operation processor for executing the arithmetic operation. [0091] One embodiment may be directed to a method that may include determining an ongoing channel occupancy time (COT) acquired by a network node based on at least one of blind decoding of group common physical downlink control channel (GC-PDCCH) or the detection of reference signal(s) associated with a target cell. The network node may be at least one of a base station, a gNB, an eNB, or an access node, etc. The method may also include determining whether the COT acquired by the network node is shared with UE(s). Based on the determining of the COT acquired by the network node, the method may also include selecting a physical random access channel (PRACH) type to be transmitted. The method may also include performing listen before talk (LBT) associated with a selected PRACH type and, in case of successful LBT, transmitting the PRACH. The method may further include blind decoding PDCCH for random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type. In an embodiment, when there is ongoing shared COT, the method may include transmitting a first type of PRACH. In another embodiment, when there is no ongoing shared COT, the method may include transmitting a second type of PRACH. The first type of PRACH may include PRACH Type 1 ; and, the second type of PRACH may include PRACH Type 2. The PRACH Type 1 may have resource continuous in frequency with bandwidth being at least the minimum bandwidth but less than required to meet an occupied channel bandwidth (OCB) limit. The PRACH Type 2 may have resource continuous in frequency with bandwidth that meets the OCB limit. The PRACH Type 2 may have resource with bandwidth being constant over the duration of PRACH. The bandwidth may have a wider portion meeting the OCB limit and narrower portion not meeting OCB limit but is at least the minimum bandwidth.

[0092] Another embodiment may be directed to an apparatus that may include at least one processor and at least one memory comprising computer program code. The at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to determine an ongoing channel occupancy time (COT) acquired by a network node based on at least one of blind decoding of group common physical downlink control channel (GC-PDCCH) or detection of reference signal(s) associated with a target cell. The network node may be at least one of a base station, a gNB, an eNB, or an access node, etc. The at least one memory and computer program code may also be configured, with the at least one processor, to cause the apparatus at least to determine whether the COT acquired by the network node is shared with UE(s). Based on the determining of the COT acquired by the network node, the at least one memory and computer program code may be further configured, with the at least one processor, to cause the apparatus at least to select a physical random access channel (PRACH) type to be transmitted. The at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to perform listen before talk (LBT) associated with a selected PRACH type and, in case of successful LBT, to transmit the PRACH. The at least one memory and computer program code may also be configured, with the at least one processor, to cause the apparatus at least to blind decode PDCCH for random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type. In an embodiment, when there is ongoing shared COT, the at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit a first type of PRACH. In another embodiment, when there is no ongoing shared COT, the at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit a second type of PRACH. The first type of PRACH may include PRACH Type 1 ; and, the second type of PRACH may include PRACH Type 2. The PRACH Type 1 may have resource continuous in frequency with bandwidth being at least the minimum bandwidth but less than required to meet occupied channel bandwidth (OCB) limit. The PRACH Type 2 may have resource continuous in frequency with bandwidth that meets the OCB limit. The PRACH Type 2 may have resource with bandwidth being constant over the duration of PRACH. The bandwidth may have a wider portion meeting the OCB limit and narrower portion not meeting OCB limit but is at least the minimum bandwidth.

[0093] Another embodiment may be directed to an apparatus that may include determining means for determining an ongoing channel occupancy time (COT) acquired by a network node based on at least one of blind decoding of group common physical downlink control channel (GC-PDCCH) or the detection of reference signal(s) associated with a target cell. The network node may be at least one of a base station, a gNB, an eNB, or an access node, etc. The apparatus may also include determining means for determining whether the COT acquired by the network node is shared with UE(s). Based on the determining of the COT acquired by the network node, the apparatus may also include selecting means for selecting a physical random access channel (PRACH) type to be transmitted. The apparatus may also include performing means for performing listen before talk (LBT) associated with a selected PRACH type and, in case of successful LBT, transmitting means for transmitting the PRACH. The apparatus may further include decoding means for blind decoding PDCCH for random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type. In an embodiment, when there is ongoing shared COT, the apparatus may include means for transmitting a first type of PRACH. In another embodiment, when there is no ongoing shared COT, the apparatus may include transmitting means for transmitting a second type of PRACH. The first type of PRACH may include PRACH Type 1 ; and, the second type of PRACH may include PRACH Type 2. The PRACH Type 1 may have resource continuous in frequency with bandwidth being at least the minimum bandwidth but less than required to meet occupied channel bandwidth (OCB) limit. The PRACH Type 2 may have resource continuous in frequency with bandwidth that meets the OCB limit. The PRACH Type 2 may have resource with bandwidth being constant over the duration of PRACH. The bandwidth may have a wider portion meeting the OCB limit and narrower portion not meeting OCB limit but is at least the minimum bandwidth.

[0094] Another embodiment may be directed to a method that includes determining whether there is a need to start a channel occupancy time (COT) / transmission burst shared with one or more UE(s). When it is determined that there is the need to start the shared COT / transmission burst, the method may then include performing listen before talk (LBT) and, in case of successful LBT, starting the transmission of COT / transmission burst. In an embodiment, the method may also include transmitting indicator(s) on the presence and/or structure of the shared COT/ transmission burst and/or transmitting scheduling information to one or more UE(s) to transmit a predefined reference signal (RS) at predefined symbol(s) with respect to physical random access channel (PRACH) occasion. In certain embodiments, the method may also include selecting the PRACH type to be detected, detecting PRACH with the selected PRACH type, and transmitting random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type.

[0095] Another embodiment may be directed to an apparatus that may include at least one processor and at least one memory comprising computer program code. The at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to determine whether there is a need to start a channel occupancy time (COT) / transmission burst shared with one or more UE(s). When it is determined that there is the need to start the shared COT / transmission burst, the at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to perform listen before talk (LBT) and, in case of successful LBT, start the transmission of COT / transmission burst. In an embodiment, the at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit indicator(s) on the presence and/or structure of the shared COT/ transmission burst and/or transmit scheduling information to one or more UE(s) to transmit a predefined reference signal (RS) at predefined symbol(s) with respect to physical random access channel (PRACH) occasion. In certain embodiments, the at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to select the PRACH type to be detected, detect PRACH with the selected PRACH type, and transmit random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type.

[0096] Another embodiment may be directed to an apparatus that includes determining means for determining whether there is a need to start a channel occupancy time (COT) / transmission burst shared with one or more UE(s). When the determining means determines that there is the need to start the shared COT / transmission burst, the apparatus may then include performing means for performing listen before talk (LBT) and, in case of successful LBT, transmitting means for starting the transmission of COT / transmission burst. In an embodiment, the apparatus may also include transmitting means for transmitting indicator(s) on the presence and/or structure of the shared COT/ transmission burst and/or transmitting scheduling information to one or more UE(s) to transmit a predefined reference signal (RS) at predefined symbol(s) with respect to physical random access channel (PRACH) occasion. In certain embodiments, the apparatus may also include selecting means for selecting the PRACH type to be detected, detecting means for detecting PRACH with the selected PRACH type, and transmitting means for transmitting random access response (RAR) identified by random access radio network temporary identifier (RA-RNTI) depending at least on the selected PRACH type.

[0097] One having ordinary skill in the art will readily understand that the example embodiments as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although some embodiments have been described based upon these example preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments. [0098] PARTIAL GLOSSARY:

[0099] BW Bandwidth

[0100] CP Cyclic Prefix

[0101] GC-PDCCH Group Common PDCCH

[0102] COT Channel occupancy time

[0103] CSI-RS Channel state information reference signal

[0104] DCI Downlink control information

[0105] DL Downlink

[0106] DMRS Demodulation reference signal

[0107] eLAA enhanced licensed assisted access

[0108] eNB enhanced Node B (LTE base station)

[0109] FDMA Frequency division multiple access

[0110] FFT Fast Fourier Transformation

[0111] gNB NR base station

[0112] IFDMA Interleaved frequency division multiple access

[0113] LAA Licensed assisted access

[0114] LBT Listen Before Talk

[0115] LTE Long term evolution

[0116] NR New Radio

[0117] NR-U New Radio Unlicensed

[0118] OCB Occupied channel bandwidth

[0119] OFDM Orthogonal frequency domain multiplexing

[0120] PDCCH Physical downlink control channel

[0121] PDSCH Physical downlink shared channel

[0122] PRACH Physical random access channel

[0123] PRB Physical Resource Block

[0124] PSD Power spectral density

[0125] PSS Primary Synchronization Signal

[0126] PUCCH Physical uplink control channel

[0127] PUSCH Physical uplink shared channel

[0128] RAR Random Access Response

[0129] RA-RNTI Random access radio network temporary identifier [0130] RO RACH occasion

[0131] RRC Radio resource control

[0132] SCS Subcarrier spacing

[0133] SRS Sounding reference signal

[0134] SSB Secondary synchronization signal

[0135] TDMA Time division multiple access

[0136] TRS Tracking reference signal

[0137] Tx Transmission

[0138] UE User equipment

[0139] UL Uplink.