WO 2020/176035
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`PCT/SG2019/050582
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`COMMUNICATION APPARATUS AND COMMUNICATION METHODFORINITIAL
`ACCESS
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`1. TECHNICAL FIELD
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`BACKGROUND
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`[0001]
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`The present disclosure generally relates
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`to a communication apparatus
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`and
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`communication method for initial access, and more particularly relates to establishing the initial
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`access of electronic devices in radio access technology.
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`2. DESCRIPTION OF RELATED ART
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`[0002]
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`In the standardization of 5G, a new radio access technology (NR: New Radio) not
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`necessarily having backward compatibility with LTE (Long Term Evolution)/LTE-Advanced has
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`been discussed in the 3GPP (3rd generation partnership project).
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`[0003]
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`In NR, as with LTE-LAA(License-Assisted Access), an operation in unlicensed bands
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`is expected. In addition,
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`in order to implement NR stand-alone (operable by NR alone) in
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`unlicensed bands, introducing the initial access procedure, which has not been introduced into
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`LTE-LAA,into unlicensed bands will be advantageous.
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`SUMMARY
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`[0004] One non-limiting and exemplary embodiment facilitates initial access of electronic
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`devices into unlicensed bandsin radio access technology (RAT).
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`[0005]
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`In one example embodiment, a technique disclosed here features a terminal
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`that
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`establishes initial access. The terminal comprises a receiver, which in operation, receives one or
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`more discovery reference signal (DRS) transmitted by a base station within a channel occupancy
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`time (COT) starting at a possible starting position that is not aligned with half a slot boundary;
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`and circuitry, which in operation, determines frame timing in response to receiving the one or
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`more DRS.
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`[0006]
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`It should be noted that general or specific embodiments may be implemented as a
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`system, a method,an integrated circuit, a computer program, a storage medium,or anyselective
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`combination thereof.
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`[0007] Additional benefits and advantages of the disclosed embodiments will become apparent
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`from the specification and drawings. The benefits and/or advantages may be individually
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`obtained by the various embodiments and features of the specification and drawings, which need
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`not all be provided in order to obtain one or more of such benefits and/or advantages.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0008]
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`The accompanying figures, where like reference numerals refer
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`to identical or
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`functionally similar elements throughout the separate views and which together with the detailed
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`description below are incorporated in and form part of the specification, serve to illustrate
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`various embodiments and to explain various principles and advantages in accordance with
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`present embodiments.
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`[0009]
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`Figures 1A and 1B show how possible starting positions are configured for DRS
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`transmission in accordance with an example embodiment.
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`[0010]
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`Figures 1C-1F show a DRS transmission in accordance with a first example
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`embodiment.
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`[0011]
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`Figure 2 shows a method of DRStransmission from a base station in accordance with
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`the first example embodiment.
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`[0012]
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`Figure 3 shows a method of performing an initial access procedure by a terminal in
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`accordance with the first example embodiment.
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`[0013]
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`Figures 4A and 4B show a DRStransmission in accordance with a second example
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`embodiment.
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`[0014]
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`Figure 5 shows a method of DRS transmission from a base station in accordance with
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`the second example embodiment.
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`[0015]
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`Figure 6 shows a method of performing an initial access procedure by a terminal in
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`accordance with the second example embodiment.
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`[0016]
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`Figures 7A and 7B show a DRStransmission in accordance with a third example
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`embodiment.
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`[0017]
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`Figure 8 shows a method of DRStransmission from a base station in accordance with
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`the third example embodiment.
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`[0018]
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`Figure 9 shows a method of performing an initial access procedure in accordance with
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`the third example embodiment.
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`[0019]
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`Figure 10 shows an electronic device in accordance with an example embodiment.
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`[0020]
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`Figure 11 shows another electronic device in accordance with an example embodiment.
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`[0021]
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`Figure 12 showsanotherelectronic device in accordance with an example embodiment.
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`[0022]
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`Skilled artisans will appreciate that elements in the figures are illustrated for simplicity
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`and clarity and have not necessarily been depicted to scale.
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`DETAILED DESCRIPTION
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`[0023]
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`In 5G NR unlicensed (NR-U) operation, an initial access procedure at least can be split
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`into the following three steps: a first step is cell search which is the procedure for user equipment
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`(UE) to acquire time and frequency synchronization with a cell and to detect the physical layer
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`cell identity (ID) of the cell. NR cell search is based on synchronization signal blocks (SSBs)
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`located on the synchronization raster. A SSB comprises a primary synchronization signal, a
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`secondary synchronization signal, a physical broadcast channel (PBCH) and a demodulation
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`reference signal (DMRS) for demodulating the PBCH. A secondstep is reception of minimum
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`system information that includes essential cell configuration parameters. A third step is random
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`access.
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`[0024] One or more discovery reference signal (DRS) is periodically transmitted by the base
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`station (gNodeB or gNB) to assist UEsin the cell search and the reception of minimum system
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`information. A DRS is transmitted within half a slot and includes at least a SSB, a control
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`resource set (CORESET) for remaining minimum system information (RMSI) associated with
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`the SSB, and a physical downlink shared channel (PDSCH)carrying the RMSI.
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`[0025]
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`In multi-beam operation, more than one DRS is transmitted in different beams
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`consecutively within a DRS transmission window. The DRStransmission window is especially
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`configured by the base station to accommodate DRS transmission. One or more parameters
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`associated with the DRS transmission window are determined by the base station and informed
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`to the UEs via a DRS measurement timing configuration (DMTC).
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`[0026]
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`In some instances, a LBT (listen before talk) mechanism is implemented for NR
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`channelaccess in unlicensed bands, depending on the country, frequency, and conditions.
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`[0027] One problem is that DRS transmission opportunities may be reduced due to LBTfailure.
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`[0028] Example embodiments solve this and other technical problems that occur with
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`providing UEsinitial access in radio access networks. Solutions include, but are not limited to,
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`providing a DRS transmission window with multiple possible starting positions per half a slot.
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`[0029] Example embodiments include apparatus and methods that provide UEsinitial access in
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`wireless networks, such as 5G NR stand-alone networks operating in unlicensed band or other
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`networks. For example, a terminal comprises a receiver, which in operation, receives one or
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`more discovery reference signal (DRS) transmitted by a base station within a channel occupancy
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`time (COT) starting at a possible starting position that is not aligned with half a slot boundary;
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`and circuitry, which in operation, determines frame timing in response to receiving the one or
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`more DRS.
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`[0030]
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`Figures
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`1LA-1B show how possible starting positions are configured for DRS
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`transmission in accordance with an example embodiment. A plurality of possible starting
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`positions are shown at 1O0A and 100B. Half a slots 110A and 110B are shown along the
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`candidate SSB position index.
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`[0031] As shown in Figure 1A, the DRS transmission window has a duration of 5 ms, SSB
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`subcarrier spacing (SCS) = 15 kHz, X = 4 (with X being the maximum numberof transmitted
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`SSBs within a DRS transmission window), Y = 10 (with Y being the maximum number of
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`candidate SSB positions within a DRS transmission window), Neg = 2 (with Neg being the
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`number of shift granularities per half a slot or possible starting positions per half a slot), Ly = 3,
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`and L» = 4 (with an i-th shift granularity having a duration of L; OFDM symbols). The half a slot
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`110A includesa first shift granularity and a second shift granularity. The half a slot also includes
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`a first possible starting position 120A and a second possible starting position 130A.
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`[0032]
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`SCS used for SSB transmissionis not fixed but can scale according to 2“ x 15 kHz (e.g.,
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`the SCSs of 15 and 30 kHz corresponding to 4 = O and 1, respectively). Further, as the
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`numerology 4 increases, a number of slots in a subframe increases such that slot length scales
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`according to the SCS (slot length = 1/2” ms). For example, each frame is 10 ms, and each
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`subframe is
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`1 ms with 10 subframes per
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`frame and 14 orthogonal
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`frequency division
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`multiplexing (OFDM) symbols per slot Ge. 7 OFDM symbols per half a slot). Each subframe
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`can be divided in to multiple OFDM symbols depending on the selected numerology 4. For SCS
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`= 15 kHz (i.e. 42= 0), a subframe contains a slot and thus half a slot has a duration of 0.5 ms. For
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`SCS = 30 kHz Ge. 42 = 1), a subframe contains two slots and thus half a slot has a duration of
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`0.25 ms. Further, each OFDM symbolin a slot can be uplink (U), downlink (D), or flexible CX).
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`[0033] As shown in Figure 1B, the DRS transmission window has a duration of 5 ms, SSB
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`SCS = 15 kHz, X =4, Y = 10, Ng = 3, Li = 2, Lo = 2, and Ls = 3. The figure shows the half a
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`slot L10B with a first shift granularity, a second shift granularity, and a third shift granularity.
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`The half a slot includes a first possible starting position 120B, a second possible starting position
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`130B, and a third possible starting position 140B.
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`[0034] As shown in Figures 1A and 1B, more than one shift granularities may be configured
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`per half a slot. As such, multiple possible starting positions may be configured per half a slot
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`within a DRS transmission window.
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`[0035] As shown in Figures 1A and 1B, the i-th shift granularity (1 <i < Ncg) has a duration of
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`L; symbols subject to the following:
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`viet Li = 7,
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`where N,, is the numberof shift granularities configured per half a slot.
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`[0036]
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`For Figure 1A, Ny, = 2, L; = 3 and L2 = 4. For Figure 1B, N,g = 3, Ly = 2, Lg = 2,
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`and L3; = 3. The numberof possible starting positions per half a slot is equal to Ng. These
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`configurations have the effect of improving the transmission opportunities of SSBs.
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`[0037]
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`In an example embodiment, for a SSB SCS, the possible starting positions per half a
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`slot are established or decided in advance (e.g., programmed and stored in memory). Further, the
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`number of possible starting positions per half a slot may vary for different SSB SCSs. For
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`example, the number of possible starting positions per half a slot for a smaller SSB SCS (e.g. 15
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`kHz) may be greater than that for a larger SSB SCS (e.g. 30 kHz). This has the effect of
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`providing similar transmission opportunities of SSBs for both the SSB SCSs.
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`[0038]
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`Figures 1C-1F show a DRS transmission in accordance with a first example
`
`embodiment.
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`[0039] As shown in Figure 1C, the DRS transmission window has a duration of 5 ms, SSB
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`SCS = 15 kHz, X = 4, Y = 10, Nog = 2, L = 3, and L, = 4. The figure showsthe half a slot 110C
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`with a first possible starting position 120C and a second possible starting position 130C. LBT
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`failed and the channel was busy as shown at 150C. A channel occupancy time (COT) obtained
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`by a base station and starting at a possible starting position whichis not aligned with half a slot
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`boundary is shown at 160C. A set of Y candidate positions 170C with the candidate position
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`indexes of 0 to 9 correspondto first possible starting positions. A set of Y-1 additional candidate
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`positions 180C with the candidate position indexes of 12 to 20 correspond to second possible
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`starting positions. Since the additional candidate positions are corresponding to the second
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`possible starting positions and cannot be outside the DRS transmission window, the number of
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`additional candidate positions is Y-1. The indexes of the additional candidate positions and the
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`indexes of the candidate positions may not be consecutive.
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`[0040] A COTis the time during which a base station or a terminal may transmit on a given
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`channel without re-evaluating the availability of the channel.
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`[0041] According to the first example embodiment, if the COT starts at a possible starting
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`position that is aligned with half a slot boundary (e.g., 151C), the time-domain positions of the
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`actually transmitted SSBs are selected from the set of Y candidate positions. If the COTstarts at
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`a possible starting position that is not aligned with half a slot boundary (e.g., 152C), the time-
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`domain positions of the actually transmitted SSBs are selected from the set of Y -1 additional
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`candidate positions corresponding to the possible starting position.
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`[0042] According to a conventional mechanism, the SSBs (e.g. 161C and 162C) dropped due
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`to LBT failure are cyclically wrapped aroundto the end of the SSB burst set transmission.
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`[0043] According to a conventional mechanism, either the SSB index issp or the candidate
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`position index 7 is indicated to UEs in the corresponding SSB for help UEs’ determination of
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`frame timing. If the SSB index i;5, is indicated to UEs in the corresponding SSB, the timing
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`offset Ossg = [i/X]| also need to be indicated to the UEsin the corresponding SSB for help UEs’
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`determination of frame timing.
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`[0044] According to a conventional mechanism, the mapping between candidate SSB position
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`index i to the SSB index issz is given by isse =i mod X. SSBs with the same issg are assumed to
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`be transmitted with the same beam. That is, antenna ports used for transmitting SSBs with the
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`same issgp are assumed to be quasi-co-located (QCLed). Two antennal ports are QCLed when
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`properties of the channel over which a symbol on one antennal port is conveyed can be inferred
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`from the channel over which a symbol on the other antennaport is conveyed.
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`[0045] According to the first example embodiment,
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`the starting index for the additional
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`candidate positions is set to an integer multiple of X. As a result, the SSB index issg for the
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`starting additional candidate position is 0, which is the same as that for the starting candidate
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`position. Referring to Figure 1C, the starting index for the additional candidate positions is 12
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`(multiple of X) as represented by 112C and the SSB index issg for the starting additional
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`candidate position is 0 as represented as 111C.
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`[0046]
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`Inthe example of Figure 1C, X = 4, Y = 10, and both the SSB index issz and the timing
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`offset Ossp are indicated to UEs in the corresponding SSB for help UEs’ determination of frame
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`timing. As mentioned in the above, the timing offset ossp is represented by |i/X] and thus the
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`timing offset ogsg can be O, | or 2 for the set of Y candidate positions and can be 3, 4 or 5 for the
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`set of Y-1 additional candidate positions. In the example of Figure 1C,
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`the number of bits
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`required for the timing offset Os, is increased from 2 to 3 due to the introduction of additional
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`candidate positions.
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`[0047]
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`Figure 1C shows a SSB with issg = 2 and Ossg = 3 is transmitted at an additional
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`candidate position with the candidate position index of 14, a SSB with isszg = 3 and Osspz = 3 is
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`transmitted at an additional candidate position with the candidate position index of 15, a SSB
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`with issg = O and Ossg = 4 is transmitted at an additional candidate position with the candidate
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`position index of 16, and a SSB with issg = 1 and Ossg = 4 is transmitted at an additional
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`candidate position with the candidate position index of 17.
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`[0048]
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`In the example of Figure 1C, if a detected SSB has the ogsg value larger than 2, then
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`UEs know the SSBis transmitted from an additional candidate position and then can properly
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`determine the frame timing based on the values of the SSB index iss, and the timing offset ossp
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`of the detected SSB.
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`[0049] As shown in Figure 1D, the DRS transmission window has a duration of 5 ms, SSB
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`SCS = 15 kHz, X =4, Y = 10, Nog = 2, Li = 3, and Ly = 4. The figure shows the half a slot 110D
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`with a first possible starting position 120D and a second possible starting position 130D. LBT
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`failed and the channel was busy as shown at 150D. A COT obtained by a base station and
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`starting at a possible starting position whichis not aligned with half a slot boundary is shown at
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`160D. A set of Y candidate positions 170D with the candidate position indexes of 0 to 9
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`correspond to first possible starting positions. A set of Y-1 additional candidate positions 180D
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`with the candidate position indexes of 12 to 20 correspond to second possible starting positions.
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`[0050]
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`In the example of Figure 1D, the candidate position index iis indicated to UEs in the
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`corresponding SSB for help UEs’ determination of frame timing. The numberofbits required for
`
`the candidate position index i is increased from 4 to 5 due to the introduction of the additional
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`candidate positions.
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`[0051]
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`Figure 1D shows a SSB with i = 14 is transmitted at an additional candidate position
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`with the candidate position index of 14, a SSB with i = 15 is transmitted at an additional
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`candidate position with the candidate position index of 15, a SSB with 7 = 16 is transmitted at an
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`additional candidate position with the candidate position index of 16, and a SSB with i = 17 is
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`transmitted at an additional candidate position with the candidate position index of 17.
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`[0052]
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`In this example of Figure 1D, Y = 10 and thus the candidate position index i is up to 9
`
`for the candidate positions. If a detected SSB has the candidate position index i of 12 to 20, then
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`UEs know the SSB is transmitted from an additional candidate position and then can properly
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`determine the frame timing based on the candidate position index of the detected SSB.
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`[0053] As shown in Figure 1E, the DRS transmission window has a duration of 5 ms, SSB
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`SCS = 15 kHz, X = 4, Y = 10, Neg = 3, Li = 2, Lo = 2, and Lz = 3. The figure showsthe half a
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`slot 110E with a first possible starting position 120E, a second possible starting position 130E,
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`and a third possible starting position 140E. LBT failed and the channel was busy as shown at
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`150E. A COTobtained by a base station and starting at a possible starting position which is not
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`aligned with half a slot boundary is shown at 160E. A set of Y candidate positions 170E with the
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`candidate position indexes of 0 to 9 correspond to first possible starting positions. A set of Y-1
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`additional candidate positions 180E with the candidate position indexes of 12 to 20 correspond to
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`second possible starting positions. A set of Y-1 additional candidate positions 190E with the
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`candidate position indexes of 24 to 32 correspondto third possible starting positions.
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`[0054]
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`In the example of Figure 1E, X = 4, Y = 10, and both the SSB index issz and the timing
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`offset Oggp are indicated to UEs in the corresponding SSB for help UEs’ determination of frame
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`timing. As mentioned in the above, the timing offset ossp is represented by |i/X] and thus the
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`timing offset Ossg can be O,
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`1 or 2 for the set of Y candidate positions, and can be 3, 4 or 5 for
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`the set of Y-1 additional candidate positions corresponding to the second possible starting
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`positions, and can be 6, 7 or 8 for the set of Y-1 additional candidate positions corresponding to
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`the third possible starting positions.
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`[0055]
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`In the example of Figure 1E, if a detected SSB has the os¢p value of 3 to 5, then UEs
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`know the SSBis transmitted from an additional candidate position corresponding to the second
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`possible starting positions. If a detected SSB has the ogsz value of 6 to 8, then UEs know the
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`SSB is transmitted from an additional candidate position corresponding to the third possible
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`starting positions. So the UEs can properly determine the frame timing based on the values of the
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`SSB index igsp and the timing offset Ogs5 of the detected SSB.
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`[0056] As shown in Figure 1F, the DRS transmission window has a duration of 5 ms, SSB
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`SCS = 15 kHz, X = 4, Y = 10, Ngg = 3, Li = 2, Lo = 2, and L3 = 3. The figure showsthe half a
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`slot 110F with a first possible starting position 120F, a second possible starting position 130F,
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`and a third possible starting position 140F. LBT failed and the channel was busy as shown at
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`150F. A COT obtained by a base station andstarting at a possible starting position which is not
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`aligned with half a slot boundary is shown at 160F. A set of Y candidate positions 170F with the
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`candidate position indexes of 0 to 9 correspond to first possible starting positions. A set of Y-1
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`additional candidate positions 180F with the candidate position indexes of 12 to 20 correspond to
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`second possible starting positions. A set of Y-1 additional candidate positions 190F with the
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`candidate position indexes of 24 to 32 correspondto third possible starting positions.
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`[0057]
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`In the example of Figure 1F, the candidate position index iis indicated to UEs in the
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`corresponding SSB for help UEs’ determination of frame timing. Compared with the example of
`
`Figure 1D, the numberof bits required for the candidate position index i is further increased to 6
`
`due to the introduction of the additional candidate SSB positions corresponding to the third
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`possible starting positions.
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`[0058]
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`In this example of Figure 1F, Y = 10 and thusthe candidate position index i is up to 9
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`for normal candidate positions. If a detected SSB has the candidate position index 7 of 12 to 20,
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`then UEs knowthe SSB is transmitted from an additional candidate position corresponding to the
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`second possible starting position. If a detected SSB has the candidate position index 7 of 24 to 32,
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`then UEs know the SSB is transmitted from an additional candidate position corresponding to the
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`third possible starting position. So the UEs can properly determine the frame timing based on the
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`candidate position index value of the detected SSB.
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`[0059] According to the first example embodiment (e.g. as shown in Figures 1C—1F), a COT
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`obtained by a base station may start from a possible starting position that is not aligned with half
`
`a slot boundary. One or more DRSis transmitted from the beginning of a COT obtained by a
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`base station, regardless of whether the COTis aligned with half a slot boundary.
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`[0060] According to the first example embodiment, if the COT starts at a possible starting
`
`position that is aligned with half a slot boundary,
`
`the time-domain positions of the actually
`
`transmitted SSBs are selected from a set of Y candidate positions.
`
`[0061]
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`If the COT starts at a possible starting position that is not aligned with half a slot
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`boundary (e.g., as shown in Figure 1C—1F), the time domain positions of the actually transmitted
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`SSBs are selected from a set of Y-1 additional candidate positions corresponding to the possible
`
`starting position. The starting index for the set of Y-1 additional candidate SSB positions is an
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`integer multiple of X.
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`[0062] These examples as
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`illustrated in Figure 1C—1F show an advantage in that
`
`the
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`conventional mechanism for determining frame timing can be reused with the introduction of
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`additional candidate positions.
`
`[0063]
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`Figure 2 shows a method 200 of DRStransmission from a base station according to the
`
`first example embodiment. At step 210 the base station determines a SSB SCS for a frequency
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`band in which the cell is operating. At step 220 the base station determines possible starting
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`positions per half a slot within a DRS transmission window for the SSB SCS. At step 230 the
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`base station obtains a COTat a possible starting position based on LBT outcome, which may not
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`be aligned with half a slot boundary. At step 240 the base station transmits one or more DRSs
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`from the beginning of the COT regardless of whether the COT is aligned with half a slot
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`boundary.
`
`[0064]
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`Figure 3 shows a method 300 of performing an initial access procedure by a terminal.
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`At step 310 the terminal determines a SSB SCS for a frequency band in which the cell is
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`operating. At step 320 the terminal detects an appropriate SSB within a DRS transmission
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`window. At step 330 the terminal determines the physical layer cell ID of the cell from the
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`detected SSB. At step 340 the terminal determines frame timing based on the values of the SSB
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`index (issg) and the timing offset (Ossg) of the detected SSB or the value of the candidate position
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`index (i) of the detected SSB as well as the possible starting positions per half a slot for the SSB
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`SCS. At step 350 the terminal obtains the essential cell configuration information from the
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`detected SSB and the remaining minimum system information (RMSI) associated with the
`
`detected SSB. At step 360, the terminal initiates a random access procedure with the basestation.
`
`[0065]
`
`Figures 4A and 4B show a DRStransmission 400 in accordance with a second example
`
`embodiment. The DRS transmission 400 showsa plurality of possibly starting positions. Half a
`
`slots are shown along the candidate position index. In the examples of Figure 4A and 4B, DRS
`
`transmission window hasa duration of 5 ms, SSB SCS = 15 kHz, X =4, Y = 10, Nsg = 2, L; = 3,
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`and Lz = 4. The figure showsthe half a slot 410 with a first possible starting position 420 and a
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`second possible starting position 430. The channel was busy at 440. LBT succeeded and the
`
`channel was idle at 450, and a COT obtained by a base station and starting a possible starting
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`position which is not aligned with half a slot boundary is shown at 460.
`
`[0066]
`
`In the example of Figure 4A, in addition to the SSB index issp and the timing offset
`
`Ossp, an extra signaling (e.g. starting position index (SPI) is indicated to UEs in the
`
`corresponding SSB to aid the UEs in determining frame timing. The SPIis set to 0 to indicate the
`
`COTstarts at the first possible starting position 420, set to 1 to indicate the COTstarts at the
`
`second possible starting position 430, and so on. The UEs can properly determine the frame
`
`timing based onthe values of the SSB index issz, the timing offset os5g and the SPI of a detected
`
`SSB.
`
`[0067]
`
`The SPI may be combined with other signaling (e.g., the timing offset Ossg) to reduce
`
`the bit width. For example, assume five possible starting positions and Ossg = 0,
`
`1 or 2. For
`
`separate signaling, three bits are used to indicate SPI and two bits are used to indicate Ossg. For
`
`combined signaling, only four bits are used to jointly indicate SPI and Ogspz.
`
`[0068]
`
`In the example of Figure 4B, in addition to the candidate SSB position index i, an extra
`
`signaling (e.g. SPI) is indicated to UEs in the corresponding SSB to aid the UEs in determining
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`frame timing. The UEs can properly determine the frame timing based on the candidate position
`
`index value and the SPI value of a detected SSB.
`
`[0069]
`
`Figure 5 shows a method 500 of DRStransmission from a base station in accordance
`
`with the second example embodiment. At step 510, the base station determines a SSB SCS for a
`
`frequency band in which thecell is operating. At step 520, the base station determines possible
`
`starting positions per half a slot for the SSB SCS. At step 530 the base station obtains a COTat
`
`a possible starting position based on LBT outcome. The possible starting position may not be
`
`aligned with half a slot boundary. At step 540 the base station transmits one or more DRS from
`
`the beginning of the COT where each SSB contains a SPI.
`
`[0070]
`
`Figure 6 is a method 600 for performing an initial access procedure by a terminal
`
`according to the second example embodiment. At step 610 the terminal determines a SSB SCS
`
`for a frequency band in which the cell
`
`is operating. At step 620 the terminal detects an
`
`appropriate SSB within a DRS transmission window. At step 630 the terminal determines the
`
`physical layer cell ID of the cell from the detected SSB. At step 640 the terminal determines
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`frame timing based on the SSB index issg, timing offset Ossg, and SPI values of the detected SSB
`
`or the candidate SSB position index i and SPI values of the detected SSB as well as the possible
`
`starting positions per half a slot for the SSB SCS. At step 650 the terminal obtains the essential
`
`cell configuration information from the detected SSB and the RMSI associated with the detected
`
`SSB. At step 660 the terminal initiates a random access procedure with the base station.
`
`[0071]
`
`Figures 7A and 7B show a DRStransmission 700 in accordance with a third example
`
`embodiment. The DRS transmission 700 showsa plurality of possibly starting positions. Half a
`
`slots are shown along the candidate position index. In this example, DRS transmission window
`
`has a duration of 5 ms, SSB SCS = 15 kHz, X = 4, Y = 10, Nog = 2, Li = 3, and Ly = 4. The
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`figures show the half a slot 710 with a first possible starting position 720 and a second possible
`
`starting position 730. The channel was busy at 740. LBT succeeded and the channel was idle at
`
`750, and a COT obtained by a basestation at a possible starting position that is not aligned with
`
`half a slot boundary is shown at 760. For Figure 7A, the SSB index issp and the timing offset
`
`Ossp are indicated to the UEs in the corresponding SSB for help frame timing determination.
`
`Figure 7A shows a SSB with issp = 3 and Osspg = O is transmitted at a candidate position with the
`
`candidate position index of 3, a SSB with issg = 0 and Ossg = | is transmitted at a candidate
`
`position with the candidate position index of 4, a SSB with issg = 1 and Ossg = 1 is transmitted at
`
`a candidate position with the candidate position index of 5, and a SSB with issp = 2 and Ossp = 1
`
`is transmitted at a candidate position with the candidate position index of 6. For Figure 7B, the
`
`candidate SSB position index i is indicated to the UEs in the corresponding SSB to help frame
`
`timing determination.
`
`[0072] As shownin thesefigures, if a COT obtained by a basestation is not aligned with half a
`
`slot boundary, the base station transmits a reservation signal 770 till next half a slot boundary
`
`before DRS transmission. Otherwise the base station just transmits one or more DRS from the
`
`beginning of the COT.
`
`[0073]
`
`The reservation signal 770 is used to prevent other neighboring system from hijacking
`
`the COT. The conventional mechanism for determining frame timing can be reused. However,
`
`channelefficiency may be reduced due to the reservation signal transmission.
`
`[0074]
`
`Figure 8 shows a method 800 of DRStransmission from a base station according to the
`
`third example embodiment. At step 810 the base station determines a SSB SCSfor a frequency
`
`band in which the cell is operating. At step 820 the base station determines possible starting
`
`positions per half a slot for the SSB SCS. At step 830 the base station obtains a COT at a
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`possible starting position based on LBT outcome. At step 840 the base station makes a
`
`determination as to whether the COT is aligned with half a slot boundary. If the answerto this
`
`determination is “yes” flow proceeds to step 850 that transmits one or more DRS from the
`
`beginning of the COT. If the answerto this determination 1s “no” flow proceeds to step 860 that
`
`transmits a reservation signal till the next half a slot boundary. At step 870 the base station
`
`transmits one or more DRSfromthe next half a slot boundary.
`
`[0075]
`
`Figure 9 is a method 900 for performing an initial access procedure by a terminal
`
`according to the third example embodiment. At step 910 the terminal determines a SSB SCSfor
`
`a frequency band in whichthe cell is operating. At step 920 the terminal detects an appropriate
`
`SSB within a DRS transmission window. At step 930 the terminal determines the physical layer
`
`cell ID of the cell from the detected SSB. At step 940 the terminal determines frame timing
`
`based on the SSB index (issg) and timing offset (Ossg) values of the detected SSB or the
`
`candidate SSB index (i) value of the detected SSB. At step 950 the terminal obtains the essential
`
`cell configuration information from the detected SSB and the RMS] associated with the detected
`
`SSB. At step 960 the terminal initiates a random access procedure with the base station.
`
`[0076]
`
`Figure 10 showsan electronic device 1000 in accordance with an example embodiment.
`
`The electronic device 1000 i