Patent Description:
This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, after the main part of the detailed description section.

In LTE, there has been a constant progression in "generations". The fourth generation (<NUM>) offered much improved uplink and downlink speeds over previous generations. The base station for <NUM> is referred to as an eNB. The fifth generation (<NUM>) is being implemented now and offers further advancements, e.g., in improved uplink and downlink speeds over <NUM>. The base station for <NUM> is referred to as a gNB. Technologies for <NUM> are often referred to as "New Radio" (NR), as NR is a study item in the 3GPP radio access network (RAN) working group and will be an enabler for <NUM> cellular networks.

For <NUM> receivers in a NR, there will likely be more challenges for NR reception.

<CIT> uses a single FFT for the two different numerologies, but this is paired with repetition of one bandwidth part for the lower subcarrier spacing and <CIT> uses two separate FFT chains for the reception of different subcarrier spacing in a same bandwidth.

The invention is as defined in the independent claim <NUM>.

The exemplary embodiments herein describe techniques and apparatus concerning frequency-domain receivers, which adapt to different subcarrier spacing configurations. Transmitters that provide signals with different subcarrier spacing configurations are also described. Additional description of these techniques is presented after a system into which the exemplary embodiments may be used is described.

The receivers described herein are applicable both at a gNB (e.g., for decoding uplink) and at a UE (e.g., for decoding downlink). Primary reference herein is made to a gNB, but the base stations may be an eNB or other base station.

Turning to <FIG>, this figure shows a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced. In <FIG>, a user equipment (UE) <NUM> is in wireless communication with a wireless network <NUM>. A UE is a wireless, typically mobile device that can access a wireless network. The UE <NUM> includes one or more processors <NUM>, one or more memories <NUM>, and one or more transceivers <NUM> interconnected through one or more buses <NUM>. The one or more buses <NUM> maybe address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like.

The examples herein involve the receiver <NUM>. The UE <NUM> further includes an Rx control module (CM) <NUM>, comprising one of or both parts <NUM>-<NUM> and/or <NUM>-<NUM>, which may be implemented in a number of ways, and which may implement some or all of the techniques presented herein for receiver <NUM>. The Rx CM <NUM> may be implemented in hardware as Rx CM <NUM>-<NUM>, such as being implemented as part of the one or more processors <NUM>. The Rx CM <NUM>-<NUM> may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the Rx control module <NUM> may be implemented as Rx CM <NUM>-<NUM>, which is implemented as computer program code <NUM> and is executed by the one or more processors <NUM>. The UE <NUM> communicates with gNB <NUM> via a wireless link <NUM>.

The gNB <NUM> is a base station (e.g., for NR) that provides access by wireless devices such as the UE <NUM> to the wireless network <NUM>. The gNB <NUM> includes one or more processors <NUM>, one or more memories <NUM>, one or more network interfaces (N/W I/F(s)) <NUM>, and one or more transceivers <NUM> interconnected through one or more buses <NUM>.

The examples herein involve the receiver <NUM>. The gNB <NUM> includes an Rx control module (CM) <NUM>, comprising one of or both parts <NUM>-<NUM> and/or <NUM>-<NUM>. The Rx CM <NUM> may perform the examples provided herein for the receiver <NUM>, for part or all of the receiver <NUM>. The Rx CM <NUM> maybe implemented in a number of ways. The Rx CM <NUM> may be implemented in hardware as Rx CM <NUM>-<NUM>, such as being implemented as part of the one or more processors <NUM>. The Rx CM <NUM>-<NUM> may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the Rx CM <NUM> may be implemented as Rx CM <NUM>-<NUM>, which is implemented as computer program code <NUM> and is executed by the one or more processors <NUM>. For instance, the one or more memories <NUM> and the computer program code <NUM> may be configured to, with the one or more processors <NUM>, cause the gNB <NUM> to perform one or more of the operations as described herein. Two or more gNBs <NUM> communicate using, e.g., link <NUM>. The link <NUM> may be wired or wireless or both and may implement, e.g., an X2 interface.

The one or more buses <NUM> maybe address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers <NUM> maybe implemented as a remote radio head (RRH) <NUM>, with the other elements of the gNB <NUM> being physically in a different location from the RRH, and the one or more buses <NUM> could be implemented in part as fiber optic cable to connect the other elements of the gNB <NUM> to the RRH <NUM>.

One additional possible implementation for receivers <NUM> or <NUM> (or both) is also illustrated by <FIG>. In this example, the receiver <NUM>/<NUM> is implemented in part or completely via one or more of an FPGA, a DSP, or an ASIC (or other integrated circuit, such as system on a chip, SoC), illustrated by reference <NUM>. The Rx control module (CM) <NUM>-<NUM> (for receiver <NUM> of the UE <NUM>) or <NUM>-<NUM> (for receiver <NUM> of gNB) can contain the entire functionality described herein, or some part of the functionality and the other part of the functionality may be implemented in one or both of Rx control modules <NUM>-<NUM>/<NUM>-<NUM> or <NUM>-<NUM>/<NUM>-<NUM>. Additionally, the FFT(s) <NUM> for the receivers <NUM>/<NUM> or the IFFT(s) <NUM> for the transmitters <NUM>/<NUM> may be implemented in hardware in the FPGA, a DSP, or an ASIC (or other integrated circuit, such as system on a chip, SoC) <NUM> or in the Rx CM <NUM>-<NUM>/<NUM>-<NUM>, <NUM>-<NUM>/<NUM>-<NUM> or in the Tx CM <NUM>-<NUM>/<NUM>-<NUM>, <NUM>-<NUM>/<NUM>-<NUM>.

Furthermore, although the examples herein primarily emphasize reception, the transmitters <NUM> and/or <NUM> would also transmit signals with at least two different subcarrier spacings, e.g., where the subcarrier spacing of the broadcast control is greater than that of the subcarrier spacing of the data. There can therefore be a Tx control module (CM) <NUM>-<NUM> as hardware associated with the processor(s) <NUM>, Tx CM <NUM>-<NUM> as software executable by the processor(s) <NUM>, and/or Tx CM <NUM>-<NUM> implemented as an FPGA, DSP, ASIC, and/or SoC <NUM>. Similarly, a Tx control module (CM) <NUM>-<NUM> maybe implemented as hardware associated with the processor(s) <NUM>, Tx CM <NUM>-<NUM> as software executable by the processor(s) <NUM>, and/or Tx CM <NUM>-<NUM> implemented as an FPGA, DSP, ASIC, and/or SoC <NUM>.

The wireless network <NUM> may include a network control element (NCE) <NUM> that may include MME (Mobility Management Entity)/SGW (Serving Gateway) functionality, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (e.g., the Internet). The gNB <NUM> is coupled via a link <NUM> to the NCE <NUM>. The link <NUM> maybe implemented as, e.g., an S1 interface. The NCE <NUM> includes one or more processors <NUM>, one or more memories <NUM>, and one or more network interfaces (N/W IIF(s)) <NUM>, interconnected through one or more buses <NUM>. The one or more memories <NUM> and the computer program code <NUM> are configured to, with the one or more processors <NUM>, cause the NCE <NUM> to perform one or more operations.

The computer readable memories <NUM>, <NUM>, and <NUM> maybe of any type suitable to the local technical environment and maybe implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories <NUM>, <NUM>, and <NUM> may be means for performing storage functions. The processors <NUM>, <NUM>, and <NUM> may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processors <NUM>, <NUM>, and <NUM> may be means for performing functions, such as controlling the UE <NUM>, gNB <NUM>, and other functions as described herein.

Having thus introduced one suitable but non-limiting technical context for the practice of the exemplary embodiments of this invention, the exemplary embodiments will now be described with greater specificity.

The exemplary embodiments herein involve, for instance, design of a flexible frequency-domain receiver chain, which can support different subcarrier spacing configurations on a per-symbol block (e.g., an OFDM symbol or a block of CP-SC symbol) basis. This kind of flexibility is desirable for <NUM> systems, since it allows different symbol durations for the reception of broadcast and data channels. One example use would be to define a shorter symbol block duration (and in turn a larger subcarrier spacing) for broadcast channels carrying beamforming reference signals (BRSs). The shorter duration would enable more beams to be trained during the same time period as occupied by regular data symbols. The data symbols would continue to have a longer symbol duration, resulting in tighter subcarrier spacing and increased spectral efficiency.

As an example, if the subcarrier spacing of the broadcast control is four times that of the data, then four broadcast control symbol blocks would fit in the same time space as the single data symbol block (note that for regular CP waveforms like OFDM, an exact fitting of the four smaller symbol blocks into one larger symbol block would require different CP sizes for the broadcast control as the data as will be described later). A receiver might have to be able to adapt to the different subcarrier spacing configurations on a per-symbol basis.

To illustrate this concept, the table (referred to as "Table <NUM>" herein) in <FIG> introduces some example numerologies for data and broadcast control subcarrier spacing configurations for an OFDM system. In this example, the numerology for data symbols is in the 'Base' column, while two possible broadcast control channel numerologies are given in the '<NUM>' and '<NUM>' columns. In both cases, the occupied bandwidth as well as the sampling rate stay constant, while the varying factors are the subcarrier spacing and the symbol duration.

LTE uses different FFT sizes and different sampling rates for different bandwidths. See 3GPP TS <NUM>. However, the subcarrier spacing remains constant and hence the broadcast control channels use the same subcarrier spacing as the data channels for the same FFT size (system bandwidth). It is also noted that IEEE <NUM>. 11d and <NUM>. 11ad are similar to LTE, where the subcarrier spacing is not switched between broadcast control and data.

One exemplary difference between these and the techniques provided herein is that with the techniques herein, the broadcast control channels use a larger subcarrier spacing than the data channels for the same FFT size (e.g., as defined by system bandwidth). To support different subcarrier spacing configurations, a flexible receiver structure is needed and examples of such structures are described herein.

More specifically, flexible frequency-domain receivers are described, which can adapt to different subcarrier spacing configurations for broadcast control and data channels. The techniques may be used with at least the following waveforms: OFDM, discrete Fourier transform (DFT) spread OFDM (DFT-S-OFDM), zero-tail DFT-S-OFDM (ZT-DFT-S-OFDM), CP-SC, NCP-SC, and training-prefix single carrier (TP-SC). It should be noted that primary emphasis is placed herein on receiver chains, but the same techniques can be used for transmitter chains. That is, transmission of data and broadcast control information may use the same techniques as those described for the receive chains, although the transmission would use IFFT(s) <NUM> while the reception would use FFT(s) <NUM>, as is known.

For the sake of illustration, say we have an OFDM system and that the subcarrier spacing for data symbol blocks is, as in Table <NUM> of <FIG>, <NUM> and the subcarrier spacing for broadcast control OFDM symbols is <NUM>. Since the occupied bandwidth in both cases remains the same, doubling the subcarrier spacing for the broadcast control symbols means that half the number of time-domain samples have to be processed. In other words, where a <NUM>-point FFT would have to be computed for the data channel, only a <NUM>-point FFT is needed for the broadcast control channels due to the shorter symbol duration. This smaller FFT can be implemented in the following two exemplary ways, depending on hardware constraints:.

Option a) is exemplified by <FIG> and <FIG>, described below, and option b) is exemplified by <FIG>, described below. Each of these options is appealing for different reasons. For instance, option b) is appealing since the same FFT can be used on both the data and control/BRS portions, which means a more efficient hardware design, as multiple FFTs do not need to be implemented (and hence hardware resources are saved).

As further examples of these, let Nbe the FFT size of the tightest subcarrier spacing configuration (e.g., the FFT size used for the data channels). Let the corresponding subcarrier spacing be Δf. More particularly, a subcarrier spacing of a portion of a time-frequency space containing the control channels may be B times (e.g., two times or some power of two) as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels. To adapt the transmitter chain to support a subcarrier spacing of <NUM>kΔf, an FFT of size N/<NUM>k must be computed for each of the <NUM>k broadcast control symbols received.

With option a), the receiver would choose between different receive chains <NUM> similar to the ones illustrated in <FIG>, each chain <NUM>-<NUM> and <NUM>-<NUM> using a different FFT block. In <FIG>, the receive chains <NUM>-<NUM>,<NUM>-<NUM> (e.g., implemented as part of a receiver <NUM>/<NUM>) take input data <NUM> and produce output data <NUM>. One receive chain <NUM>-<NUM> or <NUM>-<NUM> would be enabled at a time (e.g., by a corresponding Rx control module <NUM>, <NUM>), as per time-division multiplexing. Not also that the broadcast control channels are usually transmitted intermittently. Each receive chain <NUM>-<NUM>, <NUM>-<NUM> comprises a discard CP function <NUM>-<NUM> or <NUM>-<NUM>, a serial-to-parallel converter <NUM>-<NUM> or <NUM>-<NUM>, an FFT <NUM>-<NUM> or <NUM>-<NUM> (as FFT(s) <NUM>), a parallel-to-serial converter <NUM>-<NUM> or <NUM>-<NUM>, and a demodulate function <NUM>-<NUM> or <NUM>-<NUM>. In the example case mentioned above, a <NUM>-point FFT block <NUM>-<NUM> would compute the regular data frequency- domain symbols and a distinct <NUM>-point FFT block <NUM>-<NUM> would compute the broadcast control frequency-domain symbols.

A further example for option a) is now presented, in reference to <FIG>, which illustrates an exemplary Rx configuration for OFDM with two receiver chains. Say we have an N-sized FFT on the data, and for the BRS and other control information we want to send and receive four sub-blocks of size N/<NUM>. Note that <FIG> does not show the N-sized FFT that is used on the data, and instead only shows the part of the receiver dedicated to broadcast control processing. Further say that the first sub-block is the BRS (illustrated in <FIG> as BRS) and the second through fourth sub-blocks are control information (control blocks <NUM>, <NUM> and <NUM>, illustrated as C<NUM>, C<NUM>, and C<NUM>, respectively, in <FIG>). These control sub-blocks C could contain broadcast control information and the BRS and control C blocks are repeated on multiple beams at the Tx (e.g., Tx <NUM> or <NUM> at the UE <NUM> or base station <NUM>). Then the receiver structure for an OFDM system using option a) is given in <FIG> where it is assumed there are two Rx chains <NUM>-<NUM>, <NUM>-<NUM> with orthogonal polarizations (e.g., in a mmWave system each of these chains could be the baseband units behind radio-frequency arrays). Here the N samples <NUM>-<NUM>, <NUM>-<NUM> for each polarization <NUM>, <NUM> (creating N×<NUM> sample vectors <NUM>-<NUM>, <NUM>-<NUM>) are first broken up into the four sub-blocks BRS, C<NUM>, C<NUM>, and C<NUM> in element <NUM>-<NUM>, <NUM>-<NUM> (which separates the control pilots from control data elements). Then N/<NUM> FFTs <NUM> (as FFT(s) <NUM>) of each sub-block are performed. This example has the receiver chain <NUM>-<NUM> performing N/<NUM>-sized FFTs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for the sub-blocks BRS, C<NUM>, C<NUM>, and C<NUM>, respectively. Similarly, receiver chain <NUM>-<NUM> performs N/<NUM>-sized FFTs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for the sub-blocks C<NUM>, C<NUM>, C<NUM>, and BRS, respectively. The BRS portion is used as pilots to compute the channel estimate (using channel estimators <NUM>-<NUM>, <NUM>-<NUM>) which is then fed into an equalizer block <NUM> to decode the control messages as decoded control bits <NUM>. The equalizer block <NUM> joins the two Rx chains <NUM>-<NUM>, <NUM>-<NUM>. The BRS could also be used to determine the best beam that the transmitter should use for the receiver.

As a more specific example for <FIG>, assume subcarrier spacing of a portion of a time-frequency space containing the control channels is B times (e.g., two times or some power of two) as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels. A typical processing (such as performed in <FIG>) has the N time samples received during a control transmission by a receive chain separated into B time-domain sub-blocks. In this example, though, instead of the B time-domain sub-blocks, the N time samples are subdivided into D time-domain sub-blocks (the BRS, C<NUM>, C<NUM>, and C<NUM> in the example of <FIG>), where D≥B (D>B in this specific example) and D is an integer. If N=<NUM> and B=<NUM>, then there would be <NUM> time-domain sub-blocks (each with <NUM>/<NUM>=<NUM> samples), which would normally be processed. In <FIG>, however, the N time samples are divided by elements <NUM> into D time-domain sub-blocks (where D=<NUM>) blocks of <NUM> samples (N/<NUM> = <NUM>/<NUM> = <NUM>) for application to the N/<NUM>-sized FFTs <NUM>.

Regarding option b), examples of which are illustrated in <FIG> and <FIG> for OFDM, only one FFT block of size N is used. To compute the N/<NUM>k-point frequency domain coefficients using the N-point FFT block, the broadcast data stream has to be processed before and/or after the FFT is computed. A simple scheme is given in <FIG>, in which a receive chain <NUM> operates on input data <NUM> to create output data <NUM>, and which comprises a discard CP function <NUM>, a serial-to-parallel converter <NUM>, a repeat N/<NUM>K times function <NUM>, an N-point FFT <NUM> (as an FFT <NUM>), a down-sample by <NUM>K function <NUM>, a parallel-to-serial converter <NUM> and a demodulate function <NUM>.

<FIG> illustrates a more complex scheme, in which it is illustrated an exemplary Rx configuration (referred to as "option b)") for OFDM with two receiver chains <NUM>-<NUM>, <NUM>-<NUM>. Each chain <NUM>-<NUM>, <NUM>-<NUM> operates onN samples <NUM>-<NUM>, <NUM>-<NUM> for polarizations <NUM>, <NUM>, and forms N×<NUM> sample vectors <NUM>-<NUM>, <NUM>-<NUM>. The vectors <NUM>-<NUM>, <NUM>-<NUM> are input into elements <NUM>-<NUM>, <NUM>-<NUM>, which separate control pilots from control data and get the sub-blocks BRS, C<NUM>, C<NUM>, and C<NUM>, discussed above. Using the terminology described above, these are D time-domain sub-blocks, where D≥B and an integer (and D = <NUM> in this example). Then N-sized FFTs <NUM>-<NUM>, <NUM>-<NUM> (as FFT(s) <NUM>) operate on the sub-blocks to produce Nx1 vectors, which are processed in a block <NUM>-<NUM>, <NUM>-<NUM> in order to separate pilots and control data for a second time. The outputs of blocks <NUM>-<NUM>, <NUM>-<NUM> are the sub-blocks BRS, C<NUM>, C<NUM>, and C<NUM> (e.g., into D frequency-domain sub-blocks) and each of these is operated on by a corresponding N/<NUM>-sized FFT <NUM> (as FFT(s) <NUM>). This example has the receiver chain <NUM>-<NUM> performing N/<NUM>-sized FFTs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for the sub-blocks BRS, C<NUM>, C<NUM>, and C<NUM>, respectively. Similarly, receiver chain <NUM>-<NUM> performs N/<NUM>-sized FFTs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for the sub-blocks C<NUM>, C<NUM>, C<NUM>, and BRS, respectively. The BRS portion is used as pilots to compute the channel estimate (using channel estimators <NUM>-<NUM>, <NUM>-<NUM>) which is then fed into an equalizer block <NUM> to decode the control messages as decoded control bits <NUM>. The equalizer block <NUM> joins the two Rx chains <NUM>-<NUM>, <NUM>-<NUM>.

Returning to <FIG>, the desired FFT for one OFDM symbol is computed by repeating in block <NUM> by <NUM>k times the received data stream of length N/<NUM>k samples after removing the CP. The desired frequency domain symbols are then obtained by down-sampling (in block <NUM>) the output of the N-point FFT block to N/<NUM>k samples. Between blocks <NUM> and <NUM> and between blocks <NUM> and <NUM>, N samples are used. Repeating the samples <NUM>K times in block <NUM> then down-sampling by <NUM>K in block <NUM> allows a single N-point FFT to be used for control information. The blocks <NUM> and <NUM> would not be used for data information.

This approach can be extended to compute all <NUM>k broadcast data blocks using the N point FFT block at the same time. Instead of repeating the received data stream of length N/<NUM>k, the <NUM>k broadcast data blocks can be linearly combined first and then the N-point FFT computed. The desired frequency-domain broadcast data are interleaved in the subcarriers and each can be obtained via down-sampling.

To illustrate, recall the example introduced in Table <NUM> (see <FIG>), with a subcarrier spacing of <NUM> for the broadcast control channel, and with a subcarrier spacing <NUM> for the data channel. This illustrates that a subcarrier spacing of a portion of a time-frequency space containing the control channels may be B times (e.g., two times in this example) as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels. Doubling the subcarrier spacing means that one can accommodate twice the number of symbols in the same time-slot. As an example, if <NUM> symbols are used with <NUM> subcarrier spacing with a time-slot of <NUM> micro-second, one can accommodate <NUM> symbols in <NUM> micro-second with <NUM> subcarrier spacing. This is because if one doubles the sub-carrier spacing, the OFDM symbol duration is reduced by half. The frequency-domain broadcast control data can be computed, as explained above, as follows:.

Repeating once the <NUM> time-domain samples of the broadcast channel and then taking a <NUM>-point FFT, followed by discarding the even subcarriers follows the Rx chain implementation shown in <FIG>. Alternatively, two successive broadcast channel time domain data blocks of length <NUM> each can be used to generate time-domain data of length <NUM>, which can be passed to the <NUM>-point FFT block to compute the frequency-domain data symbols for two blocks. This procedure is illustrated in <FIG>. In this figure, a time-frequency space <NUM> is illustrated with multiple symbols <NUM>, <NUM> that are aligned in frequency but separated in time. In this case, the receiver first applies a frequency shift operation (operation <NUM>) to the second data block before combining the time-domain samples of the two blocks. The frequency shift operation (operation <NUM>) effectively shifts the symbols <NUM> to obtain an interleaved subcarrier spacing, illustrated by time-frequency space <NUM>. In operation <NUM>, the data blocks are combined in the time domain, using, e.g., a 2x2 DFT matrix. Here, for two data blocks, the first half is obtained by summing the two blocks and the second by taking the difference of the two. Then the <NUM>-point FFT in operation <NUM>, computed using the combined blocks, provides the desired frequency domain symbols with the first data block occupying the odd subcarriers and the second occupying the even subcarriers. This is illustrated by operation <NUM>, where the frequency-domain data is collected from even (block <NUM>) and odd (block <NUM>) subcarriers, and is further illustrated by frequency space <NUM>. As can be seen in frequency space <NUM>, the symbols <NUM>, <NUM> are interleaved in frequency.

An alternative version of option b) is to perform minimal processing in the time domain but then undo the frequency-domain overlap via processing in the frequency domain as is shown in <FIG>. This example is illustrated by again returning to the example of four sub-blocks containing BRS, three control portions, and also assuming there are two receiver chains <NUM>-<NUM>, <NUM>-<NUM> with orthogonal polarizations <NUM>, <NUM>. On each Rx chain <NUM>-<NUM>, <NUM>-<NUM>, the four N/<NUM> time-domain sub-blocks are separated (blocks <NUM>-<NUM>, <NUM>-<NUM>) and then are mapped to time-domain samples to input to the N-point FFT as follows: the BRS are mapped (blocks <NUM>-<NUM>, <NUM>-<NUM>) to every fourth-time sample starting from time sample <NUM> (zero), the first control portion is mapped to every fourth-time sample starting from time sample <NUM>, the second control portion is mapped to every fourth-time sample starting from time sample <NUM>, and the third control portion is mapped to every fourth-time sample starting from time sample <NUM>. This type of mapping to time samples can be referred to as a "comb structure". Then an A'-point FFT <NUM>-<NUM>, <NUM>-<NUM> is taken on each receive chain <NUM>-<NUM>, <NUM>-<NUM> of all sub-blocks together, providing N frequency-domain samples for receive branch n, Zn(<NUM>) through Zn(N-<NUM>). These frequency-domain samples contain a combination of all four sub-blocks and hence need to be processed (blocks <NUM>-<NUM>, <NUM>-<NUM>) to separate out the frequency-domain sub-blocks.

Hence the frequency-domain sub-blocks need to be separated (blocks <NUM>-<NUM>, <NUM>-<NUM>) which is performed as follows. Say Rn,<NUM>(k) are the N/<NUM> frequency-domain samples for the BRS on receiver n, and Rn,<NUM>(k) through Rn,<NUM>(k) are the N/<NUM> frequency-domain samples for control sub-blocks <NUM>-<NUM> respectively on receiver n. Then Rn,m(k), (<NUM> ≤ m ≤ <NUM>}, can be found as: <MAT> where Fe{m,/} is the (m,l)th element of Fe which is: <MAT>.

Note that the phase shift is needed to undo the effect of starting at different time samples at the input to the FFT. In the example of <FIG>, the block <NUM> implements the multiplication by the Fe{m,l} to produce the Rn,m(k).

The implementation described in option a) has a complexity of <MAT> due to the FFT block of size N/<NUM>k that may be invoked <NUM>k times to process the time domain broadcast data stream of size N/<NUM>k to fit in the same subframe duration. The data channel continues to be processed using the Appoint FFT block and hence entails a complexity of Nlog(N). The combined complexity for both data and broadcast channels is clearly reduced, with the less complex broadcast channel Rx chain contributing to the reduction, in the proposed techniques. In the current implementation with inflexible subcarrier spacing, both data and broadcast channels' FFT operations have a complexity of Nlog(N).

An advantage of using the implementation described in option b) is that a single FFT block of size N can be used for both the broadcast and data channels while achieving different subcarrier spacing configurations for the two. This advantage is particularly helpful as additional hardware real estate is not needed for the N/<NUM>k FFT sizes. The additional complexity needed for the broadcast channel with larger subcarrier spacing is incurred by the pre-processing and/or the post-processing blocks, that, however, is of complexity order (<NUM>k) << N.

Turning to <FIG>, this figure is a logic flow diagram for performing reception with different subcarrier spacing configurations. This figure illustrates the operation of an exemplary method, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments. The operations in <FIG> are assumed to be performed by a receiver <NUM> or <NUM>, e.g., under control at least in part by an Rx control module <NUM> or <NUM> in a corresponding one of the UE <NUM> or gNB <NUM>, respectively.

In block <NUM>, a frequency-domain receiver <NUM>/<NUM> performs the operation of receiving signals using at least two different subcarrier spacings, one for data channels and another one for control channels. The subcarrier spacing of a portion of a time-frequency space containing the control channels is B times as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels. The number B is an integer larger than one. The receiving comprises receiving N time samples during a data transmission and N time samples during a control transmission. In block <NUM>, the receiver <NUM>/<NUM> separates the N samples received during the control transmission into B sub-blocks. The receiver <NUM>/<NUM> in block <NUM> performs the operation of processing the N samples in the B sub-blocks to create B N/B-sized frequency-domain sub-blocks.

In block <NUM>, the receiver <NUM>/<NUM> performs the operation of processing the B N/B-sized frequency-domain sub-blocks to determine decoded control bits. The receiver <NUM>/<NUM> in block <NUM> performs outputting the decoded control bits. In block <NUM> the receiver <NUM>/<NUM> could perform one or more actions using the decoded control bits. This may include actions concerning the beamforming reference signals (BRSs), such as modifying beamforming (e.g., as gNB <NUM>) or reporting feedback based on the BRSs (e.g., as UE <NUM>), or performing operations based on other control signals.

Each of the B N/B-sized frequency sub-blocks could be equal in size to a size of an N/B-sized FFT of a respective time-domain sub-block portion.

The B time-domain sub-blocks may be mapped to different time samples of an N-point FFT in a comb structure, where an N-point FFT is used to create the B N/B-sized frequency-domain sub-blocks.

Additionally, some frequency-domain processing may be applied to the frequency-domain samples of an N-point FFT of the N time samples during a control transmission to separate out the frequency domain samples for each of the sub-blocks.

The number of sub-blocks may be a power of <NUM> (i.e., <NUM>k).

Some time-domain processing of the B time-domain sub-blocks may be performed prior to use of an N-point FFT that creates the B N/B-sized frequency-domain sub-blocks.

Blocks <NUM>-<NUM> of <FIG> describe one possible set of operations for performing reception with different subcarrier spacing configurations. As noted above, however (see, e.g., <FIG> and <FIG>), the operations are not limited to processing the N samples in the B sub-blocks to create B N/B-sized frequency-domain sub-blocks. As illustrated by <FIG>, for instance, instead of the B time-domain sub-blocks, the N time samples are subdivided into D time-domain sub-blocks (the BRS, C<NUM>, C<NUM>, and C<NUM> in the example of <FIG>), where D>B (D>B in this specific example) and D is an integer. Thus, block <NUM> of <FIG>, the receiver <NUM>/<NUM> performs the operation of separating the N samples received during the control transmission into a number of time-domain sub-blocks that is greater than or equal to B. In block <NUM>, the receiver <NUM>/<NUM> performs the operation of processing the N samples in the number of time-domain sub-blocks to create a same number frequency-domain sub-blocks, wherein the frequency-domain sub-blocks have a size of N divided by the number. The receiver <NUM>/<NUM> performs, in block <NUM>, the operation of processing the number of frequency-domain sub-blocks to determine decoded control bits.

The above examples mainly concern reception. <FIG>, meanwhile, is a logic flow diagram for performing transmission with different subcarrier spacing configurations. <FIG> illustrates the operation of an exemplary method, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments. The operations in <FIG> are assumed to be performed by a transmitter <NUM> or <NUM>, e.g., under control at least in part by a Tx control module <NUM> or <NUM> in a corresponding one of the UE <NUM> or gNB <NUM>, respectively.

In block <NUM>, the transmitter <NUM>/<NUM> performs the operation of transmitting signals using at least two different subcarrier spacings, one for data channels and another one for control channels. The subcarrier spacing of a portion of a time-frequency space containing the control channels is B times as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels, wherein B is an integer greater than one. The transmitting in block <NUM> comprises blocks <NUM> and <NUM>. The transmitter <NUM>/<NUM> in block <NUM> performs transmitting N time samples for data channels during a data transmission, using a first one of the two different subcarrier spacings. In block <NUM>, the transmitter <NUM>/<NUM> performs transmitting N time samples for control channels during a control transmission, using a second, different one of the two different subcarrier spacings. The second, different subcarrier spacing for the control channels is B times as large as the subcarrier spacing used for the data channels.

In block <NUM>, the transmitter <NUM>/<NUM> performs the operation of performing one or more actions based on information that was transmitted in the control channels. The actions may include actions concerning the beamforming reference signals (BRSs), such as modifying beamforming or receiving reported feedback based on the BRSs, or performing operations based on other control signals.

<FIG> also illustrates other possible examples. In particular, blocks <NUM> and <NUM> may be implemented via of one of blocks <NUM> or <NUM>. In block <NUM>, the transmitter <NUM>/<NUM> performs the operation of transmitting using two transmitter chains, a first transmitter chain operating on data from the data channels and comprising a first inverse fast Fourier transform (IFFT) having a first size corresponding to a first subcarrier spacing for the data channels, and a second transmitter chain operating on data from the control channels and comprising a second IFFT having a second size corresponding to a second subcarrier spacing for the control channels. The first and second sizes of the first and second IFFTs are different sizes. Block <NUM> illustrates another possibility for block <NUM>, where the transmitter <NUM>/<NUM> performs the operation of processing D time-domain sub-blocks using D N/D-sized inverse fast Fourier transforms (IFFTs), where D ≥B and an integer, and is configured to combine D frequency-domain sub-blocks from the D N/D-sized IFFTs into the N time samples for control channels.

In block <NUM>, the transmitter <NUM>/<NUM> performs the operation of transmitting using a single transmitter chain comprising a first fast inverse Fourier transform (IFFT) having a first size corresponding to a first subcarrier spacing for the data channels, and computing, by using the first IFFT, a second IFFT having a second size corresponding to a second subcarrier spacing for the control channels. The first and second sizes of the first and second IFFTs are different sizes.

It is noted that the circuitry (including implementing these by software) for blocks <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be determined by those skilled in the art. The same can be said for blocks <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; for locks <NUM>, <NUM>, <NUM>, and <NUM>; for blocks <NUM>, <NUM>, <NUM>, and <NUM>; for the blocks/operations for <FIG>; and for FFT(s) <NUM> and IFFT(s) <NUM>.

The techniques herein would be useful in 3GPP NR for ><NUM>, since the higher bandwidths will mean the subcarrier spacing will already need to be large and will result in a fairly large FFT size. For example, in the FX-AMPLE project, a <NUM> bandwidth results in an FFT size of <NUM> and a subcarrier spacing of <NUM>. Going with a smaller subcarrier spacing/FFT size results in an inefficient system, as the CP length becomes large relative to the symbol block length. However, control and BRS can tolerate more inter-block interference and hence can utilize a larger subcarrier spacing, thus enabling more beams to be scanned in the same period of time. So for FX-AMPLE, the control and BRS will use a subcarrier spacing of <NUM>, meaning four control/BRS sub-blocks will fit in the space of a single data symbol block. The techniques disclosed herein are therefore valuable, e.g., if 3GPP accepts a design which includes multiple subcarrier spacings for a given bandwidth.

Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is provide frequency-domain receivers which adapt to different subcarrier spacing configurations.

Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, an instruction set) is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in <FIG>. A computer-readable medium may comprise a computer-readable storage medium (e.g., memories <NUM>, <NUM>, and <NUM>, or other device) that may be any media or means that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable storage medium does not comprise propagating signals.

It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense.

Claim 1:
An apparatus, comprising:
a frequency-domain receiver comprising circuitry which operates with at least two different subcarrier spacings, one for data channels and another one for control channels, where subcarrier spacing of a portion of a time-frequency space containing the control channels is B times as large as the subcarrier spacing of a portion of the time-frequency space containing the data channels, wherein B is an integer greater than one, and wherein the circuitry is configured to perform operations comprising:
receiving N time samples during a data transmission and N time samples during a control transmission,
separating the N samples received during the control transmission into a number of time-domain sub-blocks that is greater than or equal to B,
processing the N samples in the number of time-domain sub-blocks to create a same number frequency-domain sub-blocks, wherein the frequency-domain sub-blocks have a size of N divided by the number;
processing the number of frequency-domain sub-blocks to determine decoded control bits; and
outputting the decoded control bits,
wherein the circuitry comprises a single receive chain comprising a first fast Fourier transform (FFT) having a first size corresponding to a first subcarrier spacing for the data channels, and the circuitry is configured to compute, by using the first FFT, a second FFT having a second size corresponding to a second subcarrier spacing for the control channels, wherein the first and second sizes of the first and second FFTs are different sizes, wherein the first FFT is an N-point fast Fourier transform (FFT) and the number of time-domain sub-blocks is B, and wherein the circuitry is configured to perform an operation of mapping the number of time-domain sub-blocks to different time samples of the N-point FFT in a comb structure, where the N-point FFT is used to create the number of N/B-sized frequency-domain sub-blocks, wherein mapping comprises performing an operation of shifting a first block of symbols, which are initially aligned in frequency in a time-frequency space with a second block of symbols, to be interleaved with the second block of symbols and combining a resultant number of time-domain sub-blocks to create data applied to the N-point FFT.