Network node with a narrowband transmitter

Abstract

Small amounts of downlink data are frequency-selectively beamformed and transmitted in a plurality of antenna beams by narrowband transmitters (22) to a plurality of UEs, simultaneously with large amounts of data that are digitally time domain beamformed and transmitted in a few antenna beams by wideband transmitters (16) to a few UEs. This approach allows for downlink transmissions to a large number of users requiring small amounts of data (e.g., HARQ ACKs, mobility data, etc.), which would be highly inefficient to transmit using a full wideband antenna beam of, e.g., 100MHz. The frequency domain beamforming does not overload the data transfer interface between a central processor (12) and digital front end circuits (14), and does not appreciably impair the wideband transmissions (16). Optionally, narrowband receivers (24) beamform receiver sensitivity to the small-data UEs, which transmit CSI that assists the DL narrowband beamforming (22).

Description

[0001] NETWORK NODE WITH A NARROWBAND TRANSMITTER

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to wireless communications, and in particular to performing beam-finding in Digital Front End (DFE) circuits of an Advanced Antenna System (AAS) by performing domain transforms on narrowband signals in the DFEs.

[0004] BACKGROUND

[0005] Wireless communication networks are ubiquitous in many parts of the world. These networks continue to grow in capacity and sophistication. To accommodate more users, different types of devices, and different use cases, the technical standards governing the operation of wireless communication networks continue to evolve. The fourth generation (4G) of network standards has been deployed, the fifth generation (5G) is in final development and is partially deployed, and the sixth generation (6G) is in design. With each generation, technological advances improve the capacity, spectral efficiency, and achieved bitrate of the wireless communication system, as well as introduce new use cases, such as Ultra Reliable and Low Latency Communications (URLLC) and Machine-to-Machine (M2) communications. As spectrum in lower frequencies fills up, higher frequency spectrum is taken into use.

[0006] 5G added a second frequency range, FR2. This provided significant new available spectrum in the range 24.25-52.6 GHz (FR1 spans 410 - 7125 MHz). At these high frequencies, wavelengths are small. Correspondingly, antenna elements are small, and each captures / radiates less energy. Accordingly, more antenna elements are required to cover the same area with the same link performance and the same inter-site distance. Advanced Antenna System (AAS) implementations contemplate hundreds, or even thousands, of antenna elements. This increases the number of data streams to be processed, increasing the system computational load. Another problem with Radio Frequency (RF) carriers at these high frequencies is that they suffer higher path loss, and hence have limited range, compared to conventional wireless telecom operating frequencies. Beamforming is one technique featured in 5G and 6G, to improve both coverage and capacity.

[0007] Beamforming refers to the use of antennas having increased and controllable directionality, whereby an RF transmission (or reception sensitivity) is narrowly focused, and is “aimed” in a specific direction. This is enabled by transmitting or receiving signals with controlled relative phase and gain in the antenna elements (or subarrays of antenna elements). The relative phases of, e.g., transmit signals sent to each antenna element are controlled to create constructive or destructive interference, thus amplifying the signal in some directions, and attenuating it in others, and hence controlling the direction in which the beam is transmitted. Similar phase manipulation of signals from antenna elements (or subarrays) in a receive antenna can also result in beamforming the sensitivity of an antenna array for receiving signals. FIG. 1 shows how a successively larger phase shift at each of adjacent antenna elements results in a directionally steered RF beam.

[0008] Because beamforming combines the outputs of multiple antenna elements (or subarrays), it increases beam gain, concentrating greater RF signal energy towards a receiver. This mitigates the inherent path loss of higher frequency carrier signals, and restores the rated equivalent isotropic radiated power (EIRP) rating of base stations operating in FR1 and FR2 to usable levels.

[0009] In addition to combatting path loss, another advantage to beamforming is that, particularly with large antenna arrays, multiple orthogonal beams can be formed and aimed in different directions, thus simultaneously addressing multiple wireless devices, also known as User Equipment (UE). For example, both a direct beam (line of sight) and a reflected beam may be targeted to a UE. Additionally, frequency-selective beamforming may be implemented, wherein subcarriers of the same Orthogonal Frequency Division Multiplexing (OFDM) symbol are assigned different weights, thus pointing beams in different directions as a function of frequency.

[0010] Beamforming may be implemented in several ways. Some basic methods are briefly reviewed.

[0011] One popular, low complexity option is analog beamforming. Here, the signals to / from the antennas are beamformed by phase shifters and variable gain amplifiers in the RF domain, close to the antenna. The rest of the signal chain is common to all or a portion of the antenna elements. In this scenario, all of the data is converted into a time domain stream early, before being sent to the RF integrated circuits (RFICs) and antennas. Since one set of beam weights is applied during the duration of one OFDM symbol, the beam is spatially fixed for all data.

[0012] Although it may have peaks in multiple directions, the data stream will be transmitted through one beam pattern, which obviously limits the possibility to simultaneously transmit data to multiple users. This technique is thus problematic when it would be advantageous to direct different data streams in many different directions, by frequency selective scheduling.

[0013] Additionally, it may be difficult for the base station to find the UEs for initial access. Present FR2 AAS systems use beam sweeping, or wider initial beams, to address this deficiency. However, this adds cost in terms of coverage, latency, and / or capacity.

[0014] The other extreme is full digital frequency selective beamforming, where each antenna element and each subcarrier of each symbol could have individual beam forming weights and support the possibility to simultaneously transmit data to multiple users as well as frequency selective beamforming. This requires inverse Fast Fourier Transform (iFFT) processing per antenna element, to transform complex OFDM symbols to time domain data streams, with each user accessing all antenna elements independently, which adds significant complexity. It also results in very high interface bitrates, which becomes particularly problematic when the number of antennas approaches 1000, and with channel bandwidths exceeding 1 GHz. The problem of high interface bitrates for digital beamforming with a large number of antennas may be mitigated by combining frequency and time domain beamforming. This retains the Frequency Division Multiplexing (FDM) and Spatial Division Multiplexing (SDM) advantages. However, there is no access to individual antenna elements independently from the central processor; hence beam sweeping is required in the uplink (UL) for UE directional finding. FIG. 2 shows the various beamforming options, and where they are implemented in the transceiver chain.

[0015] FIG. 3 depicts one architecture for implementing a variety of beamforming operations, shown roughly in actual layout relationship. RFICs are located under the antenna array, providing short interconnects between antenna elements (or subarrays of antenna elements) and RF signal processing paths. Although FIG. 3 depicts 16 RFICs, this number is not limiting (e.g., FIG. 5 depicts an aspect with 24 RFICs). Digital Front End (DFE) circuits are placed around the antenna array and RFICs. The DFEs contain digital signal processing circuitry. The number of four DFEs is not a limitation. A central processor, such as a baseband processor, performs beamforming calculations.

[0016] FIG. 4 depicts these architectural components in a data flow view, in which the DFEs are interposed between the RFICs / antenna elements and the central processor. Considering the data flow for the uplink (UL) - i.e., antennas to processor - the information rate is reduced in several steps.

[0017] Several antenna elements can be combined to form a subarray. The RFICs contain analog time domain beamforming (ATDBF) circuits (such as phase shifters and variable gain amplifiers). The DFEs include circuitry to perform digital time domain beamforming (DTDBF). ADC / DAC circuits transform signal between analog and digital domains, and may be located in RFICs or DFEs. Although RFICs and DFEs are depicted as separate integrated circuits (IC) in FIG. 4, those of skill in the art will readily recognize that the various circuits may be integrated together on one IC, or may be divided into interconnected ICs in a variety of configurations. DTDBF circuits process the antenna ports provided by the ATDBF, and can provide a number of independent beams to support single or multiple users within the analog beam created by the ATDBF. Like the ATDBF, the DTDBF is applied to the OFDM time domain symbols. The DTDBF is either calculated from UL signals, such as the UL Sounding Reference Signal (SRS), or fed back from the UE based on its downlink (DL) measurements on Channel State Information Reference Signal (CSI-RS) transmissions. Several DTDBF vectors can be applied to the same data stream, and by separating users in the frequency domain, different time domain (TD) beams can be used for different users. The cost is that several beamformed versions of the received TD data must be transformed for frequency domain (FD) processing. The RFICs and DFEs are depicted as separate entities to reflect functionality; in a given design, both RFIC and DFE circuitry - as well as ADC and DAC circuitry - may be integrated on a single die. Finally, digital frequency domain beamforming (DFDBF) is applied in the central processor, allowing frequency selective beamforming, within the beams created by the ATDBF and the DTDBF. This allows for Single-User (SU) and Multi-User (MU) Multiple Input Multiple Output (MIMO), as well as spatial multiplexity to a single UE where the user can be multiplexed, both spatially and in the frequency domain.

[0018] As mentioned above, one problem is how to locate and track UEs. The port expansion in the DTDBF is normally dominating; in many cases, ATDBF and DFDBF are very limited or even omitted. The ability to detect all UEs simultaneously would require access to all antenna ports entering the DTDBF circuitry, and forwarding this information to the central processor for joint processing; however, this is not feasible due to interface data rate limitations.

[0019] One approach to mitigate these problems with distributed digital beamforming is a parallel narrowband receiver (NBR), which extracts a small frequency portion from each antenna element and forwards that for digital processing. This architecture is depicted in FIG. 5. The received narrowband signals are sufficient for estimation of the main directions of the received signal. Since directions are more stable than the complex channel, a wideband receiver can then, in a second step, use the directions to perform wideband beamformed reception in the directions obtained from the narrowband receiver. Forthose directions, wideband reference signals from the UE can be used to determine the DFDBF. When all the beamformers are configured (ATDBF, DTDBF and DFDBF), the full bandwidth may be utilized for communications with a reduced complexity and interface load. This allows a wideband reception that retains a high signal to noise ratio (SNR), while reducing the number of data streams that must be interfaced for further combining - down to one for each direction. This approach is the subject of US Published Patent Application 2023 / 0170973 (the ‘973 publication). This approach provides a good solution for efficient reception across the full spatial domain within a narrow bandwidth. Bitrates on the interface to the central processor are reduced significantly, enhancing beamforming performance and enabling new use cases.

[0020] The NBR proposed in the ‘973 publication works very well for UL channel estimates and reception of small data packages, such as control information and small data payloads, in parallel with wideband reception of larger data packages. User data analysis reveals that also in the DL, there is a mix of data package sizes, which imposes inefficiencies in beam allocation and channel utilization.

[0021] The Background section of this document is provided to place aspects of the present disclosure in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Approaches described in the Background section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section. SUMMARY

[0022] The following presents a simplified summary of the disclosure in order to provide a basic understanding to those of skill in the art. This summary is not an extensive overview of the disclosure and is not intended to identify key / critical elements of aspects of the disclosure or to delineate the scope of the disclosure. The sole purpose of this summary is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

[0023] According to aspects of the present disclosure described and claimed herein, small amounts of downlink data are frequency-selectively beamformed and transmitted in a plurality of antenna beams by narrowband transmitters to a plurality of UEs, simultaneously with large amounts of data that are digitally time domain beamformed and transmitted in a few antenna beams by wideband transmitters to a few UEs. This approach allows for downlink transmissions to a large number of users requiring small amounts of data (e.g., HARQ ACKs, mobility data, etc.), which would be highly inefficient to transmit using a full wideband antenna beam of, e.g., 100MHz. The frequency domain beamforming does not overload the data transfer interface between a central processor and digital front end circuits, and does not appreciably impair the wideband transmissions. Optionally, narrowband receivers beamform to the small-data UEs. Centering a NBR at the same frequency range as the NBT allows the UE to transmit SRS at this frequency range, to assist the DL narrowband beamforming.

[0024] One aspect relates to communication circuitry in a network node operative in a wireless communication network and configured to transmit OFDM symbols via an AAS. Each symbol comprises a plurality of subcarriers. A wideband transmitter (WBT) comprises DTDBF circuitry configured to transmit first data packets to a first plurality of wireless devices using a first plurality of antenna beams. A narrowband transmitter (NBT) is configured to transmit second data packets to a second plurality of wireless devices using a second plurality of antenna beams. A central processor is configured to schedule first data packets to the WBT and second data packets to the NBT. An interface, having a maximum data bandwidth, connects the central processor to the WBT and the NBT in data transfer relationship. The NBT is configured to beamform subcarriers of an OFDM symbol. Each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets. The sum of a data bandwidth from the central processor to the WBT and a data bandwidth from the central processor to the NBT is less than or equal to the maximum data bandwidth of the interface.

[0025] Another aspect relates to a method, performed by a network node operative in a wireless communication network, of transmitting data to UEs in OFDM symbols from an AAS. Each OFDM symbol comprises a plurality of subcarriers. In a central processor, first data packets are scheduled to a WBT and second data packets are scheduled to an NBT. Data is transferred from the central processor to the WBT and the NBT over an interface having a maximum data bandwidth. DTDBF signals comprising first data packets are transmitted from the WBT to a first plurality of wireless devices using a first plurality of antenna beams. Subcarriers of an OFDM symbol are beamformed by the NBT. Narrowband signals comprising second data packets are transmitted from the NBT to a second plurality of wireless devices using a second plurality of antenna beams. Each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets. The sum of a data bandwidth from the central processor to the WBT and a data bandwidth from the central processor to the NBT is less than or equal to the maximum data bandwidth of the interface.

[0026] Yet another aspect relates to a base station operative in a wireless communication network. The base station includes communication circuitry as described above.

[0027] Still another aspect relates to a computer program product comprising machine readable instructions configured to, when executed on a central processor, cause communication circuitry described above to execute the method described above.

[0028] Still another aspect relates to a network node operative in a wireless communication network and configured to transmit OFDM symbols, each comprising a plurality of subcarriers, via an AAS The network node includes a WBT comprising a DTDBF, configured to transmit first data packets to a first plurality of wireless devices using a first plurality of antenna beams; an NBT configured to beamform subcarriers of an OFDM symbol and to transmit second data packets to a second plurality of wireless devices using a second plurality of antenna beams; and a narrowband receiver (NBR) configured to receive third data packets from the second plurality of wireless devices. A central processor is configured to schedule first data packets to the WBT and second data packets to the NBT, and further configured to use at least one data packet received by the NBR to derive channel state information of a channel between the network node and a first device of the second plurality of wireless devices. The NBT is configured to use the derived channel state information to adapt the beamforming of a signal transmitted to the first device of the second plurality of wireless devices.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which aspects of the disclosure are shown. However, this disclosure should not be construed as limited to the aspects set forth herein. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout.

[0031] FIG. 1 is a diagram showing the relationship between beam steering and phase shift. FIG. 2 is a diagram showing the functional and implementation views of various forms of beamforming along the transceiver chain.

[0032] FIG. 3 is hardware block diagram of RFICs under an antenna array, with DFEs and a central processor.

[0033] FIG. 4 is a data flow view of the hardware blocks of FIG. 3. FIG. 5 is an AAS receiver block diagram showing NBRs in each DFE.

[0034] FIG. 6 is a graph showing observed DL traffic patterns.

[0035] FIG. 7 is a block diagram of a communication circuitry including wideband transmitters (DTDBF), NBTs, and NBRs.

[0036] FIG. 8 is a block diagram showing upscaling of sampling, with optional bypassing of stages, in the NBTs.

[0037] FIG. 9 is a flow diagram of a method of transmitting data to UEs.

[0038] FIG. 10 is a hardware block diagram of a network node, such as a base station, in a wireless communication network.

[0039] FIG. 11 is a functional block diagram of a network node, such as a base station, in a wireless communication network.

[0040] DETAILED DESCRIPTION

[0041] For simplicity and illustrative purposes, the present disclosure is described by referring mainly to an exemplary aspect thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be readily apparent to one of ordinary skill in the art that the present disclosure may be practiced without limitation to these specific details. In this description, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure.

[0042] FIG. 6 shows one example of network data session sizes in the DL. Notably, half the sessions are <1 kB, whereas half the data traffic is generated by sessions >50MB. This translates to a mix of many small packages and fewer large ones. For example, a large number of users may engage in activities requiring only small download packet sizes, such as a HARQ acknowledgement, mobility control data, incremental data delivered to an app (traffic or weather update) and the like. Simultaneously, relatively few users may be streaming movies, downloading large apps or Operating System (OS) upgrades, or the like.

[0043] In this situation, the use of DTDBF (iFFT in the DFEs) consumes significant resources, since the minimum scheduling bandwidth is a single carrier. Using DFDBF (in the central processor) is more efficient for the smaller packages, since the scheduling granularity is one resource block (RB), about 100 times greater than that achievable with DTDBF. The typical carrier bandwidth in 5G is around 100 MHz. Since only one (or a few) beams can be scheduled per transmission time interval (TTI), it is not possible to fill up the carrier with data, due to the small packet sizes, and hence a large part of the carrier will be empty. This dramatically lowers efficiency of the system, wasting valuable air interface resources, as well as needlessly consuming power.

[0044] Additionally, control channels and some reference signals are inherently narrow band. Hence, transmitting one control channel would occupy only a tiny fraction of the full carrier bandwidth. If all resources must be beamformed in the same direction, it is unlikely that the narrow band control data to one user could be combined with wide band data transmission to another user, since the same beam must be used for both.

[0045] Accordingly, simultaneous use of a narrowband DFDBF and a wideband DTDBF is advantageous. The narrowband DFDBF is frequency selective (per subcarrier or group of subcarriers) and addresses numerous users with low data rate demands. The use of DTDBF for wideband efficiently transmits large amounts of data to one or a few users, while avoiding overloading the interface between the central processor and DFEs.

[0046] DTDBF can apply different beam weights for different portions of the spectrum.

[0047] However, this is not per sub-carrier, but for groups of sub-carriers, and the typical granularity is a full 5G carrier. The group of sub-carriers is first filtered out from the rest of the signal using digital filters in the TD, and then the beam weight is applied on the sub-set of the spectrum. Accordingly, DTDBF can support multiple UEs, on multiple beams.

[0048] FIG. 7 depicts one specific aspect of communication circuitry 10 of the present disclosure. Although the communication circuitry 10 is bidirectional, this disclosure focuses on the DL paths. In this aspect, a total carrier bandwidth (TCBW) is divided into a number of carriers, each having a lower bandwidth. Multiple data streams may be generated in a central processor 12, and transferred to the narrowband TD carriers, in a corresponding number of iFFTs. The same information is sent to each of four DFEs 14, across a high speed bus having a limited bandwidth. As one non-limiting example, the Common Public Radio Interface (CPRI) may be used. The number of signal streams transferred on each channel determines the number of different directions of wideband beamforming that can be supported.

[0049] Digital TD beamforming (DTDBF) is performed in wideband transmitters (WBT) 16 within the DFEs 14, to form outputs forwarded to the DFE-tiles 18. These are further expanded in RFICs 20 to feed the antenna array. Each data bus interface thus carries a TCBW of time domain data.

[0050] In parallel, additional iFFT capacity and interface bandwidth is required per DFE 14 to perform DFDBF. These data are provided to narrow band transmitters (NBT) 22, which can perform frequency selective beamforming to users having small data transfer needs.

[0051] For completeness, FIG. 7 shows a number of optional (as indicated by dashed lines) narrowband receivers (NBR) 24, each performing beamforming for received signals of low bandwidth, as discussed in the above-cited ‘973 publication.

[0052] The DFE-tiles 18 perform channel filtering, and include circuitry for performing up-sampling (LIPSA), down-sampling (DNSA), Crest Factor Reduction (CFR), Digital Predistortion (DPD), and Automatic Gain Control (AGC).

[0053] In another aspect of the present disclosure, DFDBF and DTDBF are employed for elevation port expansion, for example 1:4. In this case, a narrow frequency range is used, with full elevation coverage. This use case also has the benefit of reducing elevation sweeping. In another aspect, interface bandwidth is reduced by using a frequency domain interface. Using primarily low order modulation (e.g., control channels), the interface bandwidth is significantly reduced, such as by 2 to 4 times. Small, distributed iFFT circuits are efficient, as iFFT complexity scales with N*log2(N).

[0054] FIG. 8 depicts details of an NBT 22, according to one aspect. NBT data to be transmitted is received through the bus interface, filtered, and upsampled to the normal carrier rate. An IQ formatter (IQF) block 26 changes the data format from a floating format to integer. A memory 27 optionally stores precomputed sequences of data, such as may be useful in RADAR transmissions. As discussed above, these data may be loaded during UL slots of a TDD schedule. The data are then upsampled with programable up sampling, e.g., using a factor from 2 to 16, in steps of a factor of 2. After that, a frequency rotator using a Numerically Controlled Oscillator (NCO) 28 moves the narrow band information to the correct place inside the narrowband sub-band / carrier. At the end, a complex multiplication 30 is performed for compensation of amplitude and phase error in the analog part of the radio, and is also an opportunity to scale the signal level. The NBT 22 can either operate in streaming mode or read IQ data from memory. The memory can be loaded at a lower rate (to lower the peak rate), or contain predefined sequences (e.g., for radar transmission). Filtering is required in order to avoid interference between adjacent subcarriers. Half band (HB) filters are depicted, as they are an efficient structure in many applications; however, any type of digital filters can be used.

[0055] Although subcarriers are orthogonal, filtering is primarily needed to suppress quantization noise. The upsampling is variable (by optionally bypassing upsample blocks) to allow for varying the NBT 22 bandwidth. Finally, data is added onto one of the carriers in multiplexer 32.

[0056] Isolation is required between the wideband 16 transmission and NBT 22 transmission. One aspect of the present disclosure relies on beam isolation, by transmitting wideband data and narrowband data in different directions. In another aspect, the subcarriers used for NBT 22 are punctured, or not used, in the WBT 16. In either case, the NBT (22) and WBT (16) transmit on different subcarriers. The interface for WBT 16 adds some noise, but it is low and somewhat beamformed, and so it does not significantly impair NBT 22 transmissions.

[0057] The power level of the NBT 22 can be adjusted to either boost or attenuate the Power Spectral Density (PSD) of the NBT 22 subcarriers. In one aspect, to spatially multiplex many users, the signal is boosted to maintain a constant PSD / layer. The signal may also be boosted to improve Over The Air (OTA) link budget.

[0058] The combination of NBR 24 and NBT 22 yields the greatest benefit. Assuming the NBR 24 has equal or wider bandwidth than the NBT 22, the NBR 24 is used to receive narrowband SRS data from all active UEs. This gives detailed CSI from each UE, which can be used for efficient reciprocity-based spatial multiplexing of multiple UEs in the NBT 22.

[0059] As one example of the benefits of using NBTs 22, assume (as shown in FIG. 6) that there are many UEs with small DL data needs, which could be served using only a few RBs, and a smaller number of UEs streaming large amounts of data. Without any NBTs 22 and assuming that 4 Primary Component Carriers (PCC) and 4 layers are available, only 16 UEs can be simultaneously served, which is very inefficient. By utilizing NBTs 22 with, e.g., 8 RB (11.52MHz) bandwidth, and where 16 data streams can be spatially multiplexed, then 64 narrowband UEs can be served in parallel, while still utilizing almost the full bandwidth for WBT 16. In many real-world situations, many UEs only require infrequent mobility reference signals. By using NBTs 22 with local signal memory to store signals and possibly beam directions, the mobility reference signals can be sent periodically, while keeping most of the base station in sleep mode. The base station can then be awoken by a controlling distributed unit (DU) as needed.

[0060] FIG. 9 depicts the steps in a method 100, performed by a network node operative in a wireless communication network, of transmitting data to UEs in OFDM symbols from an AAS, wherein each OFDM symbol comprises a plurality of subcarriers. In a central processor 12, first data packets are scheduled to a wideband transmitter 16 and second data packets are scheduled to an NBT 22 (block 102). Data is transferred from the central processor 12 to the WBT 16 and the NBT 22 over an interface having a maximum data bandwidth (block 104). DTDBF signals comprising first data packets are transmitted from the WBT 16 to a first plurality of wireless devices using a first plurality of antenna beams (block 106). Subcarriers of an OFDM symbol are beamformed by the NBT 22 (block 108). Narrowband signals comprising second data packets are transmitted from the NBT 22 to a second plurality of wireless devices using a second plurality of antenna beams (block 110). Each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets. The sum of a data bandwidth from the central processor 12 to the WBT 16 and a data bandwidth from the central processor 12 to the NBT 22 is less than or equal to the maximum data bandwidth of the interface.

[0061] In one representative aspect, a data transfer bus between the central processor 12 and DFEs 14 is implemented as three instances of a 4-lane CPRI, with a capacity of 50G. The WBTs 16 transmit up to 16 DTDBF channels, each with a bandwidth of 100 MHz. The NBTs 24 transmit up to 48 frequency-selective beamformed channels, each with a bandwidth of 6.25 MHz. In other aspects, the NBT 24 bandwidth may be 12.5 or 25 MHz. Optionally, NBRs 24 receive up to 48 beamformed channels, each with a bandwidth of 25 MHz. In this aspect, the TCBWis 1600 MHz.

[0062] Apparatuses described herein may perform the method 100 herein and any other processing by implementing any functional means, modules, units, or circuitry. In one aspects of the disclosure, for example, the apparatuses comprise respective circuits or circuitry configured to perform the steps shown in the method FIGs. The circuits or circuitry in this regard may comprise circuits dedicated to performing certain functional processing and / or one or more microprocessors in conjunction with memory. For instance, the circuitry may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory may include program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein, in several aspects of the disclosure. In aspects of the disclosure that employ memory, the memory stores program code that, when executed by the one or more processors, carries out the techniques described herein.

[0063] FIG. 10 for example illustrates a hardware block diagram of a network node 40, such as a base station, operative in a wireless communication network. The base station 40 - known in various network implementations as a Radio Base Station (RBS), Base Transceiver Station (BTS), Node B (NB), enhanced Node B (eNB), Next Generation Node B (gNB), or the like - is a node of a wireless communication network that implements a Radio Access Network (RAN) in a defined geographic area called a cell, by providing radio transceivers to communicate wirelessly with a plurality of UEs.

[0064] The base station 40 includes the communication circuitry 10 described with reference to FIG. 7, which transmits and receives RF signals on an AAS 42. As indicated by the broken line, the antennas 42 may be located remotely from the base station 40, such as on a tower or building. The communication circuitry 10 includes the central processor 12, WBTs 16, NBTs 22, and optionally (as indicated by dashed lines) NBRs 24, as described herein. Other details from FIG. 7 are omitted for clarity. The communication circuitry 10 additionally provides one or more communication links to one or more other network nodes, propagating communications UE traffic, to other network nodes or other networks, such as telephony networks or the Internet. The central processor 12 may control substantially the entire functionality of the network node 40, or may be a “baseband processor” dedicated to signal processing of communication signals. Memory 44 is operatively connected to the central processor 12 and stores instructions operative to cause the central processor 12 to execute the method 100 described herein.

[0065] Although the memory 44 is depicted as being separate from central processor 12, those of skill in the art understand that the central processor 12 includes internal memory, such as a cache memory or register file. Those of skill in the art additionally understand that virtualization techniques allow some functions nominally executed by the central processor 12 to actually be executed by other hardware, perhaps remotely located (e.g., in the so-called “cloud”). The central processor 12 in this regard may implement certain functional means, units, or modules.

[0066] FIG. 11 illustrates a functional block diagram of a network node 50 in a wireless network according to still other aspects of the disclosure, in which the network node 50 may be configured and / or operates as a base station. As shown, the network node 50 implements various functional means, units, or modules, e.g., via the central processor 12 in FIG. 10 and / or via software code. These functional means, units, or modules, e.g., for implementing the method 100 herein, include: wideband transmitting unit 52; narrowband transmitting unit 54; scheduling unit 56; and data interface unit 58.

[0067] Wideband transmitting unit 52 is configured to transmit DTDBF signals comprising first data packets from a WBT 16 to a first plurality of wireless devices using a first plurality of antenna beams. Narrowband transmitting unit 54 is configured to transmit narrowband signals comprising second data packets from an NBT 22 to a second plurality of wireless devices using a second plurality of antenna beams. Scheduling unit 56 is configured to schedule, in a central processor 12, first data packets to the WBT 16 and second data packets to the NBT 22. Data interface unit 58 is configured to transfer data from the central processor 12 to the WBT 16 and the NBT 22 over an interface having a maximum data bandwidth. The narrowband transmitting unit 54 is further configured to beamform subcarriers of an OFDM symbol. Each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets. The sum of a data bandwidth from the central processor 12 to the WBT 16 and a data bandwidth from the central processor 12 to the NBT 22 is less than or equal to the maximum data bandwidth of the interface.

[0068] Those skilled in the art will also appreciate that aspects of the disclosure herein further include corresponding computer programs.

[0069] A computer program comprises instructions which, when executed on at least one processor of an apparatus, cause the apparatus to carry out any of the respective processing described above. A computer program in this regard may comprise one or more code modules corresponding to the means or units described above.

[0070] Aspects of the disclosure further include a carrier containing such a computer program. This carrier may comprise one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

[0071] In this regard, aspects of the disclosure herein also include a computer program product stored on a non-transitory computer readable (storage or recording) medium and comprising instructions that, when executed by a processor of an apparatus, cause the apparatus to perform as described above.

[0072] Aspects of the disclosure further include a computer program product comprising program code portions for performing the steps of any of the aspects of the disclosure herein when the computer program product is executed by a computing device. This computer program product may be stored on a computer readable recording medium.

[0073] Aspects of the present disclosure provide numerous advantages over the prior art, and may also provide one or more of the following technical advantage(s). By performing frequency selective beamforming in NBTs 22 having very narrow bandwidth (e.g., a few RBs), numerous UEs can be served small amounts of data simultaneously on separate antenna beams. This prevents the allocation of an entire 100 MHz channel to a UE for these small data transmissions, which would grossly waste valuable air interface resources. There is only a slight impact on the data-intensive interface between the central processor 12 and the wideband and narrowband transmitters 16, 22 and minimal impact on the transmitted wideband signals, which may be properly dedicated to UEs having heavy DL requirements. Particularly in combination with NBRs 24 that can supply CSI, the NBTs 22 dramatically improve efficiency in AAS systems.

[0074] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc., are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the aspects disclosed herein may be applied to any other aspect, wherever appropriate. Likewise, any advantage of any of the aspects may apply to any other aspects, and vice versa. Other objectives, features and advantages of the enclosed aspects will be apparent from the description.

[0075] The term “unit” may have conventional meaning in the field of electronics, electrical devices and / or electronic devices and may include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0076] As used herein, the term “configured to” means set up, organized, adapted, or arranged to operate in a particular way; the term is synonymous with “designed to,” or with respect to processing circuitry, “programmed to.”

[0077] Some of the aspects contemplated herein are described more fully with reference to the accompanying drawings. Other aspects, however, are contained within the scope of the subject matter disclosed herein. The disclosed subject matter should not be construed as limited to only the aspects set forth herein; rather, these aspects are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0078] The present disclosure may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the disclosure. The present aspects are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended aspects are intended to be embraced therein.

Claims

CLAIMSClaims:

1. A network node (40, 50) operative in a wireless communication network and configured to transmit Orthogonal Frequency Domain Modulation, OFDM, symbols, each comprising a plurality of subcarriers, via an Advanced Antenna System, AAS, the network node comprising:a wideband transmitter, WBT, (16) comprising a Digital Time Domain Beamformer, DTDBF, configured to transmit first data packets to a first plurality of wireless devices using a first plurality of antenna beams;a narrowband transmitter, NBT (22), comprising a Digital Frequency Domain Beamformer, DFDBF, configured to beamform subcarriers of an OFDM symbol and to transmit second data packets to a second plurality of wireless devices using a second plurality of antenna beams;a central processor (12) configured to schedule first data packets to the WBT (16) and second data packets to the NBT (22);an interface for data transfer, having a maximum data bandwidth, connecting the central processor (12) to the WBT (16) and the NBT (22);wherein each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets; andwherein a sum of a data bandwidth from the central processor (12) to the WBT (16) and a data bandwidth from the central processor (12) to the NBT (22) is less than or equal to the maximum data bandwidth of the interface.

2. The network node of claim 1, wherein a transmitted signal from the NBT (22) and a transmitted signal from the WBT (16) are combined, and the combined transmit signal is output to a plurality of antenna elements or groups of antenna elements.

3. The network node of any preceding claim, wherein the NBT (22) and WBT (16) transmit on different subcarriers.

4. The network node of any preceding claim, wherein a bandwidth of a transmitted signal from the NBT (22) is separate from a bandwidth of a transmitted signal from the WBT (16).

5. The network node of any preceding claim, further comprising a narrowband receiver, NBR (24), configured to receive third data packets from the second plurality of wireless devices, wherein the third data packets have a smaller maximum data size than the maximum data size of the first data packets.

6. The network node of claim 5, wherein at least one data packet received by the NBR (24) is used to derive channel state information of a channel between the network node and a first device of the second plurality of wireless devices.

7. The network node of claim 6, wherein the NBT (22) is configured to use the derived channel state information to adapt the beamforming of a signal transmitted to the first device of the second plurality of wireless devices.

8. The network node of any preceding claim, wherein the NBT (22) comprises one or more up-samplers and one or more multiplexers.

9. The network node of claim 8, wherein a number of up-samplers is based on a ratio between a carrier bandwidth and a sub-carrier bandwidth.

10. The network node of claim 9, wherein at least one of the up-samplers is configured to be by-passed, based on the ratio between a carrier bandwidth and a sub-carrier bandwidth.

11. The network node of any preceding claim, wherein the NBT (22) comprises a frequency rotator configured to assign a narrowband transmitted signal to a carrier.

12. The network node of claim 11 , wherein the NBT (22) further comprises a multiplier configured to perform a multiplication by an antenna code complex coefficient, wherein the antenna code complex coefficient corresponds to a Digital Frequency Domain Beam Former, DFDBF.

13. The network node of any preceding claim, wherein the NBT (22) further comprises memory configured to store data to be transmitted in a downlink slot of a time division duplex, TDD, schedule.

14. The network node of claim 13, wherein the central processor (12) is further configured to transfer data to the memory of the NBT (22) during an uplink slot of the TDD schedule.

15. The network node of claim 13, wherein the data stored in the memory of the NBT (22) relates to RADAR.

16. A method (100), performed by a network node (40, 50) operative in a wireless communication network, of transmitting data to User Equipment, UE, in Orthogonal FrequencyDomain Modulation, OFDM, symbols from an Advanced Antenna System, AAS, wherein each OFDM symbol comprises a plurality of subcarriers, characterized by:scheduling (102), in a central processor (12), first data packets to a wideband transmitter, WBT, (16) and second data packets to a narrowband transmitter, NBT (22);transferring (104) data from the central processor (12) to the WBT (16) and the NBT (22) over an interface having a maximum data bandwidth;transmitting (106) Digital Time Domain Beamformed, DTDBF, signals comprising first data packets from the WBT (16) to a first plurality of wireless devices using a first plurality of antenna beams;beamforming (108), by, the NBT (22), subcarriers of an OFDM symbol; and transmitting (110) narrowband signals comprising second data packets from the NBT (22), to a second plurality of wireless devices using a second plurality of antenna beams;wherein each of the second data packets has a smaller maximum data size than a maximum data size of the first data packets; andwherein a sum of a data bandwidth from the central processor (12) to the WBT (16) and a data bandwidth from the central processor (12) to the NBT (22) is less than or equal to the maximum data bandwidth of the interface.

17. The method (100) of claim 16, further characterized by combining a transmitted signal from the NBT (22) and a transmitted signal from the WBT (16), and outputting the combined transmit signal to a plurality of antenna elements or groups of antenna elements.

18. The method (100) of any of claims 16-17, wherein a bandwidth of a transmitted signal from the NBT (22) is separate from a bandwidth of a transmitted signal from the WBT (16).

19. The method (100) of claim 16 wherein the NBT (22) and WBT (16) transmit on different subcarriers.

20. The method (100) of any of claims 16-19, further comprising receiving, in a narrowband receiver, NBR (24), third data packets from the second plurality of wireless devices, wherein the third data packets have a smaller maximum data size than the maximum data size of the first data packets.

21. The method (100) of claim 20, further characterized by using at least one data packet received by the NBR (22) to derive channel state information of a channel between the network node and a first device of the second plurality of wireless devices.

22. The method (100) of claim 21, wherein the NBT (22) is configured to use the channel state information to adapt the beamforming of the signal transmitted to the first device of the second plurality of wireless devices.

23. The method (100) of any of claims 16-22, wherein the NBT (22) comprises one or more up-samplers and one or more multiplexers.

24. The method (100) of claim 23, wherein a number of up-samplers is based on a ratio between a carrier bandwidth and a sub-carrier bandwidth.

25. The method (100) of claim 24, wherein at least one of the up-samplers is configured to be by-passed, based on the ratio between a carrier bandwidth and a sub-carrier bandwidth.

26. The method (100) of any of claims 16-25, wherein the NBT (22) comprises a frequency rotator configured to assign a narrowband transmitted signal to a carrier.

27. The method (100) of claim 26, wherein the NBT (22) further comprises a multiplier configured to perform a multiplication by an antenna code complex coefficient, wherein the antenna code complex coefficient corresponds to a Digital Frequency Domain Beam Former, DFDBF.

28. A network node (40, 50) operative in a wireless communication network and configured to transmit Orthogonal Frequency Domain Modulation, OFDM, symbols, each comprising a plurality of subcarriers, via an Advanced Antenna System, AAS, the network node comprising:a wideband transmitter, WBT (16), comprising a Digital Time Domain Beamformer, DTDBF, configured to transmit first data packets to a first plurality of wireless devices using a first plurality of antenna beams;a narrowband transmitter, NBT (22), comprising a Digital Frequency Domain Beamformer, DFDBF, configured to beamform subcarriers of an OFDM symbol and to transmit second data packets to a second plurality of wireless devices using a second plurality of antenna beams;a narrowband receiver, NBR (24), configured to receive third data packets from the second plurality of wireless devices;wherein at least one data packet received by the NBR (24) is used to derive channel state information of a channel between the network node and a first device of the second plurality of wireless devices; andwherein the NBT (22) is configured to use the derived channel state information to adapt the beamforming of a signal transmitted to the first device of the second plurality of wireless devices.

29. A base station (40, 50) operative in a wireless communication network, comprising: the network node of any of claims 1-15 or 28.

30. A computer program product comprising machine readable instructions configured to, when executed on a central processor (10), cause the network node of any of claims 1-15 to execute the method (100) of any of claims 16-27.

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