Efficient PRACH Scheduling

Abstract

Systems and methods for efficiently scheduling random access channel (RACH) opportunities in a cellular communication system are provided. In one embodiment, a method performed by a base station includes transmitting a synchronization signal block (SSB) on a respective transmit beam according to a beam scanning scheme. The SSB is mapped to one or more RACH opportunities according to an N-to-1 mapping scheme, where N is greater than 1. The method further includes, for each RACH opportunity, processing received signals from at least a subset of antenna elements in an antenna array of the base station using a respective narrowband receiver to provide narrowband received signals; and performing random access preamble detection for a plurality of beam directions corresponding to at least a subset of transmit beams that transmitted at least a subset of the SSBs to which the RACH opportunity is mapped, based on the narrowband received signals.

Description

Technical Field

[0001] The present disclosure relates to random access in a cellular communication system. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) 5th Generation (5G) network is enabled by a new technology called millimeter wave (mmW). The term mmW generally refers to a specific radio spectrum portion between 24 gigahertz (GHz) and 100 GHz. Compared with the low frequency band, the radio waves in this spectrum portion have very short wavelengths and significant atmospheric attenuation. The reason why mmW is attractive for 5G networks is that most of this spectrum is unused. This means that the amount of available bandwidth for the network can be greatly increased compared with traditional networks. To cope with the high attenuation loss, 5G relies on massive multiple-input multiple-output (MIMO) and beamforming to direct the transmit beam and receive beam and improve the coverage. However, the combination of the massive antenna arrays required for massive MIMO and beamforming and the large bandwidth poses huge requirements on the interface between the radio unit of the base station (referred to as a new radio (NR) base station (gNB) in 5G NR) and the baseband unit of the base station. Such an interface is usually unaffordable. Therefore, the interface limitation poses a constraint on the beamforming of mmW. One common implementation of mmW is that the gNB transmits or receives only in one direction at a time over the entire frequency carrier.

[0003] For initial access to mmW, the gNB transmits a synchronization signal block (SSB), which includes synchronization signals (i.e., a primary synchronization signal (PSS) and a secondary synchronization signal (SSS)) and a physical broadcast channel (PBCH). More specifically, the SSB is usually beamformed and swept over multiple beam directions to cover the entire cell area. Compared with the low frequency band, multi-SSB beam scanning is very important for mmW to ensure reasonable cell coverage. By detecting the SSB, the user equipment (UE) can obtain the physical cell identifier (PCI), achieve downlink synchronization in the time domain and frequency domain, and acquire the timing of the PBCH. By detecting the PBCH, the UE can obtain the basic system information. After detecting the SSB, the UE transmits a random access preamble on the physical random access channel (PRACH) to indicate a random access attempt to the gNB. Since there are multiple SSB beams sweeping over the cell, the gNB usually listens in corresponding multiple beam directions sequentially during the corresponding random access channel (RACH) time / frequency occasion to detect whether any UE is performing a random access attempt in a specific beam direction. In other words, the gNB usually needs to schedule multiple consecutive RACH time / frequency occasions.

[0004] Figure 1Shows an exemplary association from SSB to PRACH occasion. In this example, one SSB is mapped to one PRACH occasion, and several PRACH occasions are time / frequency multiplexed. In the shown example, the gNB transmits the first SSB in the first beam direction during the first time period, the second SSB in the second beam direction during the second time period, the third SSB in the third beam direction during the third time period, and the fourth SSB in the fourth beam direction during the fourth time period. The first SSB is mapped to the first PRACH occasion, the second SSB is mapped to the second PRACH occasion, the third SSB is mapped to the third PRACH occasion, and the fourth SSB is mapped to the fourth PRACH occasion. In this example, PRACH occasions are multiplexed in frequency and time. It should be noted that in mmW, PRACH occasions usually cannot be frequency multiplexed as Figure 1 shown, because the gNB can usually only receive in one direction on the entire frequency carrier at a time. However, the 3GPP specification allows frequency multiplexing of PRACH occasions.

[0005] As mentioned above, in mmW, one SSB is usually mapped to one PRACH occasion, and PRACH occasions are time division multiplexed, as Figure 2A and Figure 2B shown in the examples. In Figure 2A and Figure 2B 's example, there are four downlink time slots and one uplink time slot. Therefore, the downlink to uplink ratio is 4:1. In addition, in this example, twenty-four SSBs are mapped to twenty-four PRACH occasions, or twelve SSBs are mapped to twelve PRACH occasions. The problems with the one-to-one mapping of SSB and PRACH are: long waiting time for the random access process and low frequency utilization efficiency.

[0006] Figures 3A to 3C Shows a scheduling example of the time division duplex (TDD) 4:1 mode. In this example, there are twelve SSB bursts on twelve beams scheduled in time slots 1, 6, 11, 16, 21, and 26. The corresponding RACH occasions are in time slots 9, 19, 29,..., 119. Therefore, after transmitting twelve SSBs in twelve corresponding beam directions, the gNB must listen for random access preambles from the UE during twelve RACH occasions, and the last of these twelve RACH occasions is in time slot 119. If there are more SSBs / beam directions, listening for random access preambles after the beam sweeps through the SSBs will take even longer time and / or consume even more time-frequency resources.

[0007] In a Physical Random Access Channel (PRACH) occasion, since the receiving beam is in a direction corresponding to a specific SSB beam direction, traffic data (i.e., Physical Uplink Shared Channel (PUSCH) transmission) cannot be received to serve another UE in a different direction, which results in a huge loss of frequency resource utilization. If the carrier bandwidth is 100 megahertz (MHz), which corresponds to 66 Physical Resource Blocks (PRBs), then in this example, 12 * 6 symbols * 66 PRB time / frequency resources are reserved for the PRACH. This huge loss makes it impractical to adopt the long format PRACH because the long format PRACH occupies more symbols, which will further lead to a greater underutilization of frequency resources. However, in some cases, the long format PRACH is necessary because it provides a greater coverage range compared to the short format PRACH.

[0008] Therefore, systems and methods are needed to mitigate the huge loss of frequency utilization caused by the 1-to-1 SSB to PRACH resource mapping. Summary of the Invention

[0009] Systems and methods for efficiently scheduling Random Access Channel (RACH) occasions in a cellular communication system are provided. In one embodiment, a method for random access in a cellular communication system performed by a base station includes transmitting a plurality of Synchronization Signal Blocks (SSBs) on a corresponding plurality of transmit beams according to a beam scanning scheme. According to an N-to-1 mapping scheme, the plurality of SSBs are mapped to one or more RACH occasions, where N is greater than 1. The method further includes: for each RACH occasion among the one or more RACH occasions, using a corresponding plurality of narrowband receivers to process a plurality of received signals from at least one subset of a plurality of antenna elements in an antenna array of the base station, thereby providing a plurality of narrowband received signals, and based on the plurality of narrowband received signals, performing random access preamble detection for a plurality of beam directions corresponding to at least one subset of the plurality of transmit beams that transmitted at least one subset of the plurality of SSBs to which the RACH occasion is mapped. In this way, the N-to-1 SSB to RACH occasion mapping is enabled. Therefore, compared to the conventional 1-to-1 SSB to RACH occasion mapping, both the random access waiting time and the frequency resource overhead are greatly reduced.

[0010] In one embodiment, the one or more RACH occasions include a single RACH occasion, and all the plurality of SSBs are mapped to the single RACH occasion.

[0011] In one embodiment, one or more RACH opportunities include a first RACH opportunity and a second RACH opportunity, and a plurality of SSBs include a first set of SSBs mapped to the first RACH opportunity and a second set of SSBs mapped to the second RACH opportunity. In one embodiment, the first set of SSBs and the second set of SSBs are mutually exclusive. In one embodiment, the first set of SSBs is a first subset of the plurality of SSBs transmitted on a first subset of a plurality of transmit beams having beam directions that are adjacent to each other in space, and the second set of SSBs is a second subset of the plurality of SSBs transmitted on a second subset of a plurality of transmit beams having beam directions that are adjacent to each other in space.

[0012] In one embodiment, the bandwidth of each of the plurality of narrowband receivers is equal to or greater than the bandwidth of each of one or more RACH opportunities.

[0013] In one embodiment, the bandwidth of each of the plurality of narrowband receivers is less than the bandwidth of the wideband receiver of the base station.

[0014] In one embodiment, the plurality of narrowband received signals correspond to orthogonal frequency division multiplexing (OFDM) symbols or accumulated OFDM symbols.

[0015] A corresponding base station embodiment is also provided. In one embodiment, a base station for random access in a cellular communication system is adapted to transmit a plurality of SSBs on a corresponding plurality of transmit beams according to a beam scanning scheme, wherein the plurality of SSBs are mapped to one or more RACH opportunities according to an N-to-1 mapping scheme, where N is greater than 1. The base station is further adapted to: for each RACH opportunity among the one or more RACH opportunities, use a corresponding plurality of narrowband receivers to process a plurality of received signals from at least one subset of a plurality of antenna elements in an antenna array of the base station, thereby providing a plurality of narrowband received signals, and based on the plurality of narrowband received signals, perform random access preamble detection for a plurality of beam directions corresponding to at least one subset of a plurality of transmit beams that transmitted at least one subset of the plurality of SSBs to which the RACH opportunity is mapped.

[0016] In one embodiment, one or more RACH opportunities include a single RACH opportunity, and all of the plurality of SSBs are mapped to the single RACH opportunity.

[0017] In one embodiment, one or more RACH opportunities include a first RACH opportunity and a second RACH opportunity, and a plurality of SSBs include a first set of SSBs mapped to the first RACH opportunity and a second set of SSBs mapped to the second RACH opportunity. In one embodiment, the first set of SSBs and the second set of SSBs are mutually exclusive. In one embodiment, the first set of SSBs is a first subset of the plurality of SSBs transmitted on a first subset of a plurality of transmission beams having beam directions that are spatially adjacent to each other, and the second set of SSBs is a second subset of the plurality of SSBs transmitted on a second subset of a plurality of transmission beams having beam directions that are spatially adjacent to each other.

[0018] In one embodiment, the bandwidth of each of the plurality of narrowband receivers is equal to or greater than the bandwidth of each of one or more RACH opportunities.

[0019] In one embodiment, the bandwidth of each of the plurality of narrowband receivers is less than the bandwidth of the broadband receiver of the base station.

[0020] In one embodiment, the plurality of narrowband received signals correspond to OFDM symbols or accumulated OFDM symbols.

[0021] In another embodiment, a base station for random access in a cellular communication system includes: an antenna array including a plurality of antenna elements; a radio unit; and a baseband unit. The radio unit includes a broadband transmitter coupled to the plurality of antenna elements and a plurality of narrowband receivers respectively coupled to at least one subset of the plurality of antenna elements. The baseband unit is configured to: transmit a plurality of SSBs on respective ones of the plurality of transmission beams via the broadband transmitter of the radio unit according to a beam scanning scheme, wherein the plurality of SSBs are mapped to one or more RACH opportunities according to an N-to-1 mapping scheme, where N is greater than 1. The baseband unit is further configured to: for each RACH opportunity among the one or more RACH opportunities, receive a plurality of narrowband received signals via the plurality of narrowband receivers, and perform preamble detection for random access based on the plurality of narrowband received signals for a plurality of beam directions corresponding to at least one subset of the plurality of transmission beams that transmit at least one subset of the plurality of SSBs to which the RACH opportunity is mapped. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings incorporated and forming a part of this specification illustrate several aspects of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0023] Figure 1 Illustrates an exemplary association from a Synchronization Signal Block (SSB) to a Physical Random Access Channel (PRACH) opportunity;

[0024] Figure 2A and Figure 2BShows a mapping of an SSB to a PRACH occasion, where the PRACH occasions are time-division multiplexed in a conventional manner;

[0025] Figures 3A to 3C Shows an example of scheduling with a time-division duplex (TDD) 4:1 pattern;

[0026] Figure 4 Shows an example of a cellular communication network in which embodiments of the present disclosure may be implemented;

[0027] Figure 5 Shows a base station according to an embodiment of the present disclosure;

[0028] Figure 6 Shows an example of mapping multiple SSBs to a single PRACH occasion according to an embodiment of the present disclosure;

[0029] Figure 7 and Figure 8 Shows Figure 5 An exemplary embodiment of a narrowband receiver, an optional accumulator, and PRACH processing and detection circuitry;

[0030] Figure 9 Is a flowchart showing the operation of a base station according to an embodiment of the present disclosure;

[0031] Figure 10 Is a schematic block diagram of a radio access node according to some embodiments of the present disclosure;

[0032] Figure 11 Is a schematic block diagram showing a virtualized embodiment of a radio access node according to some embodiments of the present disclosure; and Figure 10

[0033] Figure 12 Is a schematic block diagram of a radio access node according to some other embodiments of the present disclosure; Figure 10 DETAILED DESCRIPTION

[0034] The embodiments set forth below represent information enabling those skilled in the art to implement these embodiments and show the best mode of implementing these embodiments. After reading the following description with reference to the drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically set forth herein. It should be understood that these concepts and applications fall within the scope of the present disclosure.

[0035] Radio Node: As used herein, "radio node" is a radio access node or a wireless communication device.

[0036] Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a radio access network (RAN) of a cellular communication network that operates to wirelessly transmit and / or receive signals. Some examples of radio access nodes include, but are not limited to, base stations (e.g., a new radio (NR) base station (gNB) in a 3rd Generation Partnership Project (3GPP) 5th Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), high-power or macro base stations, low-power base stations (e.g., micro base stations, pico base stations, home eNBs, etc.), relay nodes, network nodes that implement some functions of a base station, or network nodes that implement a gNB distributed unit (gNB-DU), or network nodes that implement some functions of some other type of radio access node.

[0037] Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements core network functions. Some examples of core network nodes include, for example, a mobility management entity (MME), a packet data network gateway (P-GW), a service capability exposure function (SCEF), a home subscriber server (HSS), etc. Some other examples of core network nodes include nodes that implement an access and mobility function (AMF), a user plane function (UPF), a session management function (SMF), an authentication server function (AUSF), a network slice selection function (NSSF), a network exposure function (NEF), a network function (NF) repository function (NRF), a policy control function (PCF), a unified data management (UDM), etc.

[0038] Communication Device: As used herein, a "communication device" is any type of device that can access an access network. Some examples of communication devices include, but are not limited to: mobile phones, smart phones, sensor devices, meters, vehicles, home appliances, medical devices, media players, cameras, or any type of consumer electronics, such as, but not limited to, televisions, radios, lighting devices, tablets, laptop computers, or personal computers (PCs). A communication device can be a portable, handheld, computer-including, or vehicle-mounted mobile device capable of transmitting voice and / or data via a wireless or wired connection.

[0039] Wireless communication device: One type of communication device is a wireless communication device, which can be any type of wireless device capable of accessing a wireless network (e.g., a cellular network) (i.e., being served by it). Some examples of wireless communication devices include, but are not limited to: user equipment devices (UE) in a 3GPP network, machine type communication (MTC) devices, and Internet of Things (IoT) devices. Such wireless communication devices can be or can be integrated into mobile phones, smart phones, sensor devices, meters, vehicles, household appliances, medical devices, media players, cameras, or any type of consumer electronics, such as, but not limited to, televisions, radios, lighting devices, tablets, laptops, or PCs. A wireless communication device can be a portable, handheld, computer-including, or vehicle-mounted mobile device capable of transmitting voice and / or data via a wireless connection.

[0040] Network node: As used herein, a "network node" is any node that is part of the RAN or core network of a cellular communication network / system.

[0041] It should be noted that the descriptions given herein focus on 3GPP cellular communication systems, and thus, 3GPP terms or terms similar to 3GPP terms are often used. However, the concepts disclosed herein are not limited to 3GPP systems.

[0042] It should be noted that in the descriptions herein, the term "cell" may be referred to; however, especially with respect to the 5G NR concept, beams can be used instead of cells, and thus, it is important to note that the concepts described herein apply equally to cells and beams.

[0043] Systems and methods for avoiding a 1-to-1 mapping of SSB to physical random access channel (PRACH) are disclosed herein. In other words, the systems and methods disclosed herein implement an N-to-1 mapping of SSB to PRACH, where N is an integer greater than 1. More specifically, in one embodiment, a radio access node (e.g., a base station such as a gNB) includes a narrowband receiver (NBR), which enables the radio access node to simultaneously receive signals from multiple wireless communication devices (e.g., UEs) in various beam directions. In one embodiment, the NBR is a digital receiver that receives (i.e., listens) simultaneously in multiple directions (e.g., all directions) but only on a portion of the entire system bandwidth.

[0044] In one embodiment, the radio access node is an NR radio access node, and for a PRACH with a preamble format having a short sequence (e.g., L = 139), 12 physical resource blocks (PRBs) are sufficient to handle the PRACH. Thus, the bandwidth of the NBR is equal to 12 PRBs. In one embodiment, the NBR is an omni-directional receiver, and all synchronization signal blocks (SSBs) are mapped to one PRACH occasion. In another embodiment, the NBR is a multi-directional receiver, and multiple SSBs are mapped to one PRACH occasion.

[0045] It should be noted that herein, the NBR is described as a receiver that processes a limited set of the total system bandwidth. By doing so, the amount of information that needs to be transmitted through the interface between the radio unit of the radio access node and the baseband unit of the radio access node is significantly reduced. This overcomes the interface limitation described above. In this way, the NBR can receive simultaneously in multiple (e.g., all) beam directions without imposing extreme requirements on the interface between the radio unit and the baseband unit. This enables the N-to-1 mapping of SSBs to PRACH occasions described herein. Other ways of limiting the requirements for the required interface bandwidth can also be envisioned. For example, only a limited set of available orthogonal frequency division multiplexing (OFDM) symbols can be processed. Another alternative would be to only process a subset of the available spatial dimensions, such as a subset of available antennas or beams. These alternatives can be used as alternatives to the NBR or in combination with the NBR to reduce the bandwidth requirements for the interface between the radio unit and the baseband unit, which in turn enables the N-to-1 mapping of SSBs to PRACH occasions.

[0046] The proposed solution avoids the need for a one-to-one mapping of SSBs to PRACH occasions. Thus, both the random access waiting time and the frequency resource overhead are significantly reduced. In addition, at each PRACH occasion, the PRBs outside the bandwidth of the NBR can be scheduled for PUSCH transmission from another UE. For example, a 100 megahertz (MHz) carrier has 66 PRBs. If the NBR processes 12 PRBs, the remaining 54 PRBs can be scheduled for another beam, direction, or UE.

[0047] Furthermore, the significantly reduced frequency resource overhead provided by the embodiments of the proposed solution means that long format PRACH can be employed when necessary to improve cell coverage. In addition, more SSB beams can be configured because with the embodiments of the proposed solution, the PRACH waiting time and overhead are significantly reduced. Many narrow SSB beams will increase the gain of each beam, thus improving the coverage of the SSB.

[0048] In addition, after a radio access node (e.g., gNB) receives a random access preamble via NBR, the radio access node can determine a more accurate beam direction with a higher beamforming gain based on the received random access preamble. The newly determined beam direction can be directly applied to the random access response and the signaling after the random access response. This can significantly improve the link budget for such signaling, which is typically challenging for existing solutions.

[0049] In summary, the proposed solution will significantly improve system performance. All of these can be achieved through the current interface constraints of the network.

[0050] At this point, Figure 4 An example of a cellular communication system 400 in which embodiments of the present disclosure may be implemented is shown. In the embodiments described herein, the cellular communication system 400 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) that includes gNBs utilizing NR radio access technology (RAT), and optionally Next Generation eNBs (ng-eNBs) (i.e., LTE base stations connected to a 5G Core (5GC)). In this example, the RAN includes base stations 402-1 and 402-2, which are referred to as gNBs in 5G NR and control corresponding (macro) cells 404-1 and 404-2. Base stations 402-1 and 402-2 are generally referred to as base stations 402 herein and are referred to as base station 402, respectively. Similarly, (macro) cells 404-1 and 404-2 are generally referred to as (macro) cells 404 herein and are referred to as (macro) cell 404, respectively. The RAN may also include a plurality of low-power nodes 406-1 to 406-4 that control corresponding small cells 408-1 to 408-4. The low-power nodes 406-1 to 406-4 may be small base stations (e.g., pico base stations or femto base stations) or remote radio heads (RRHs), etc. It is noted that although not shown, one or more of the small cells 408-1 to 408-4 may alternatively be provided by the base stations 402. The low-power nodes 406-1 to 406-4 are generally referred to as low-power nodes 406 herein and are referred to as low-power node 406, respectively. Similarly, the small cells 408-1 to 408-4 are generally referred to as small cells 408 herein and are referred to as small cell 408, respectively. The cellular communication system 400 further includes a core network 410, which is referred to as a 5GC in the 5GS. The base stations 402 (and optionally the low-power nodes 406) are connected to the core network 410.

[0051] Base station 402 and low-power node 406 provide services to wireless communication devices 412-1 to 412-5 in corresponding cells 404 and 408. Wireless communication devices 412-1 to 412-5 are generally referred to as wireless communication devices 412 herein and are respectively referred to as wireless communication devices 412. In the following description, wireless communication device 412 is generally a UE, but the present disclosure is not limited thereto.

[0052] Figure 5 A base station 402 according to an embodiment of the present disclosure is shown. It should be noted that this discussion also applies to base station 406. It should be noted that optional components are represented by dashed boxes. As shown, base station 402 includes an antenna array 500, which includes a plurality of antenna elements 502-1 to 502-N A , where N A is an integer value greater than or equal to 2, but preferably substantially greater than 2 (e.g., 8, 16, 32, 64, etc.). It should be noted that each antenna element 502 can be a single antenna element or a group of antenna elements connected to a common feeder port.

[0053] In this example, base station 402 further includes a radio unit 504 and a baseband unit 506. The radio unit can be implemented as an application-specific integrated circuit (ASIC), which is represented as "radio ASIC" herein, and the baseband unit can be implemented as another ASIC, which is represented as "baseband ASIC" herein. Radio unit 504 includes a broadband receiver 508, which is coupled to antenna elements 502-1 to 502-N of antenna array 500 A . Broadband receiver 508 particularly includes an uplink beamforming component 510 (e.g., an amplifier or gain circuit and a phase adjustment circuit), and the uplink beamforming component operates to provide receive beamforming for signals received via antenna elements 502-1 to 502-N of antenna array 500 A . Radio unit 504 further includes a broadband transmitter 512, which is also coupled to antenna elements 502-1 to 502-N of antenna array 500 A . Broadband transmitter 512 particularly includes a downlink beamforming component 514 (e.g., a gain circuit and a phase adjustment circuit), and the downlink beamforming component operates to provide transmit beamforming for signals (e.g., SSB) transmitted via antenna elements 502-1 to 502-N of antenna array 500 A . It should be noted that uplink and / or downlink beamforming can alternatively be at least partially performed in baseband unit 506 (e.g., a part of the uplink (i.e., receive) beamforming is performed in radio unit 504 to compress the data volume, and then the second part of the uplink beamforming is completed in the baseband).

[0054] According to an embodiment of the present disclosure, the radio unit 504 further includes a narrowband receiver 516, which is coupled to the antenna elements 502-1 to 502-N of the antenna array 500 A or at least one subset of the antenna elements 502-1 to 502-N of the antenna array 500 A Optionally, the radio unit 504 may include an accumulator 518, which operates to accumulate the output of the narrowband receiver 516. For example, as described in the commonly owned and assigned International Patent Application Publication No. WO2019 / 219810A1, titled "COST EFFICIENT PRACH DETECTION", published on November 21, 2019. The accumulation results in averaging the signals output by the narrowband receiver 516 over multiple symbols, which is beneficial for reducing the amount of information transmitted to the baseband unit 506 for random access channel (RACH) detection in the case of using a PRACH preamble format with symbol repetition.

[0055] The baseband unit 506 includes PRACH processing and detection circuitry 520, which operates to process the output of the narrowband receiver 516 or the accumulator 518 (if present), and perform PRACH detection based on the processing result. In addition, the baseband unit 506 includes functions 522, which include a scheduler, a link adaptation function, coding and modulation functions, etc., as understood by those of ordinary skill in the art.

[0056] The narrowband receiver 516 in the radio unit 504 operates to process signals received from at least one subset of the antenna elements 502-1 to 502-N of the antenna array 500 A to output corresponding narrowband received signals. In one embodiment, the narrowband receiver 516 processes signals received from all the antenna elements 502-1 to 502-N of the antenna array 500 with a limited bandwidth A to provide corresponding narrowband received signals for all the antenna elements 502-1 to 502-N of the antenna array 500 A This limited bandwidth corresponds to a part of the full system bandwidth, which includes frequency resources (e.g., PRBs) that can be used by the UE 412 to transmit random access preambles (i.e., the part of the full system bandwidth where the RACH opportunity mapped to the transmitted SSB is located). In another embodiment, the narrowband receiver 516 processes received signals from only a subset of the antenna elements 502-1 to 502-N of the antenna array 500 over a limited bandwidth A to provide corresponding narrowband received signals for the antenna elements 502-1 to 502-N of the antenna array 500 AThe corresponding narrowband received signal of that subset.

[0057] In addition, in some embodiments, the narrowband receiver 516 outputs a narrowband received signal during a limited time period (e.g., a limited number of symbols). This limited time period includes time resources on which the UE 412 can transmit a random access preamble (e.g., the OFDM symbols in which the RACH opportunity mapped to the transmitted SSB is located). There may be a trade-off regarding the number of antenna elements N A The number, the processing bandwidth (i.e., the bandwidth of the narrowband receiver 516), and the number of symbols (i.e., the limited time period during which the narrowband receiver 516 outputs a narrowband received signal). This trade-off can make the output data suitable for the available interface capabilities.

[0058] In one embodiment, the narrowband receiver 516 receives signals in all directions (e.g., all beam directions). As described below, this enables a 1-to-N SSB to PRACH opportunity mapping. Thus, when performing PRACH preamble reception and detection, the narrowband receiver 516 will process the received signals from all antenna elements 502-1 to 502-N A The received signals, for example, only the received signals on 12 PRBs out of the available 66 PRBs (in the case of a 100 MHz carrier) and on dedicated symbols scheduled for PRACH.

[0059] If the narrowband receiver 516 receives signals in all directions for PRACH preamble detection, the scheduler 522 of the baseband unit 506 only needs to schedule one PRACH opportunity after all SSB beams have been scanned. Using Figures 3A to 3C The TDD 4:1 scheduling example shown in, only one PRACH opportunity needs to be scheduled instead of twelve PRACH opportunities. Figure 6 Shows an example of scheduling this single PRACH opportunity in slot 29. Compared with the existing solution that requires 12 PRACH opportunities and the last PRACH opportunity is scheduled in slot 119 (see Figures 3A to 3C ) Figure 6 The example of the proposed solution shown in shortens the RACH waiting time by 90 slots. In addition, the resources in slots 9, 19, 39,..., 119 can now be used for physical uplink shared channel (PUSCH) transmission. This gives the Figure 6 The proposed scheduling pattern shown in. In slot 29, during the symbols in which the PRACH opportunity is scheduled, the PUSCH from another UE can be frequency multiplexed with the PRACH preamble transmission (i.e., in PRBs outside the limited bandwidth of the narrowband receiver 516) and processed by the wideband receiver 508.

[0060] In the above example, the time / frequency resources reserved for PRACH preamble reception and detection at base station 40 are only 1 * 6 symbols * 12 PRBs. This is in contrast to the case where the proposed solution is not used, in which 12 * 6 symbols * 66 PRBs need to be allocated to PRACH (see Figures 3A to 3C ).

[0061] It should be noted that in the 15th version of the 3GPP specification, for FR2, the minimum number of RACH opportunities in each subframe (10 ms) is two RACH opportunities. Therefore, within 20 ms, there must be four RACH opportunities, occurring in time slots 39, 79, 119, and 159. Therefore, the 15th version of the 3GPP specification does not support the RACH configuration as shown in Figure 6 . However, even though four RACH opportunities are required within 20 ms, a significant reduction in frequency-time resource overhead can be achieved by, for example, mapping all 12 SSBs to one of these RACH opportunities in a manner similar to that shown in the example of Figure 6 . In the above example, the time / frequency resources reserved for PRACH preamble reception and detection at base station 402 are only 4 * 6 symbols * 12 PRBs. This is in contrast to the case where the proposed solution is not used, in which 12 * 6 symbols * 66 PRBs need to be allocated to PRACH (see Figures 3A to 3C ).

[0062] In another embodiment, the narrowband receiver 516 receives signals in multiple directions, which may be all directions or a subset of all directions. In this case, if the narrowband receiver 516 receives signals in multiple but not all directions, more than one PRACH opportunity can be used to support the reception of random access preambles in all directions (for example, the first PRACH opportunity is for the first subset of all directions, and the second PRACH opportunity is for the second subset of all directions, where the narrowband receiver 516 can be used to receive signals in the first direction subset and the second direction subset during different time periods corresponding to the first PRACH opportunity and the second PRACH opportunity, respectively). It should be noted that in this case, the radio unit 504 also includes a beamforming (BF) function 517, which performs spatial filtering on the narrowband received signals received from the narrowband receiver 516. Alternatively, this spatial filtering is done in the baseband unit 506. As another exemplary alternative, there may be a BF function 517 between the NBR 516 and the antenna 502-N A , where beamforming is done in the analog domain, and then the NBR 516 compresses the resulting beamformed signal in the frequency domain.

[0063] In an implementation where interface / hardware limitations require further reducing the amount of data transmitted from the narrowband receiver 516 to the baseband unit 506, it may be beneficial to receive signals only in a subset of directions for PRACH preamble detection. This means that the narrowband receiver 516 listens to only a subset of the spatial domain at a time. For example, the narrowband receiver 516 can listen to the spatial domain covered by four SSB beams at a time. In this case, in the previous example, three PRACH opportunities can be scheduled, for example, in time slots 9, 19, and 29 respectively. There is still a 90-time-slot waiting time reduction and a significant overhead reduction. It should be noted that if the 15th version of the 3GPP specification is used, the PRACH opportunity can be scheduled in time slots 39, 79, or 119. Different from the case where all 12 SSBs are mapped to 1 RACH opportunity, time slot 159 can be scheduled for PUSCH. In this case, the time-frequency resource overhead is reduced.

[0064] If it is desired to use a long-format PRACH (e.g., to increase cell coverage), the same solution can be applied. For example, in an embodiment where the narrowband receiver 516 receives in all directions, 12 symbols instead of 6 symbols in time slot 29 can be reserved for PRACH, again referring to Figure 6 . It should be noted that if the 15th version of the 3GPP specification is used, the symbols in time slots 39, 79, 119, and 159 can be reserved for PRACH.

[0065] At the base station 402, the output of the narrowband receiver 516 or the accumulator 518 (if any) is sent to the baseband unit 506 through an interface. In the baseband unit 506, the received signal is transformed from the time domain to the frequency domain, for example, by a fast Fourier transform (FFT), in order to extract the signal portion in the time-frequency resources to be processed for PRACH preamble detection. The resulting extracted frequency-domain signal can be further processed to ensure a sufficient signal-to-interference-plus-noise ratio (SINR) level so that the PRACH preamble (if any) can be successfully detected. As an example, the beamforming weights corresponding to the beam directions of each previously transmitted SSB can be applied to the extracted frequency-domain signal. After that, a PRACH detector or receiver processes the resulting beamformed signal for PRACH preamble detection.

[0066] In Figure 7 and Figure 8 an exemplary embodiment of the narrowband receiver 516, the optional accumulator 518, and the PRACH processing and detection circuit 520 is shown. Optional components are represented by dashed lines. As shown, the antenna array 500 includes a plurality (N A pieces) of antenna elements 502-1 to 502-N A , which are labeled AE1 to Within radio unit 504, narrowband receiver 516 includes antenna elements 502-1 through 502-N coupled to the antenna elements 502-1 through 502-N, respectively. A Narrowband receivers 516-1 to 516-N A , and the accumulation circuit 518 includes accumulation circuits 518-1 to 518-N A In operation, narrowband receivers 516-1 through 516-N A From antenna elements 502-1 to 502-N respectively A Receive signal r1 to And process the signal r1 to To output a narrowband received signal in the time domain, which in this example is used for antenna elements 502-1 to 502-N A The narrowband received signal corresponds to a time domain representation of multiple OFDM symbols, which is limited to the narrowband receivers 516-1 to 516-N. A The bandwidth is limited to the OFDM symbols in which the PRACH preamble may be present in this example. Optionally, the accumulation circuit 518-1 accumulates multiple (N) OFDM symbols received via antenna element 502-1 to output an average symbol for antenna element 502-1. Similarly, the accumulation circuit 518-2 accumulates multiple (N) OFDM symbols received via antenna element 502-2 to output an average symbol for antenna element 502-2, and so on. The average symbol is Figure 7 In the expression a1 to As described above, the radio unit 504 transmits the narrowband received signal or, alternatively, the average symbol a1 to Passed to the baseband unit 506.

[0067] In some embodiments, the accumulator circuits 518-1 to 518-N A The number of symbols accumulated (N) is a fraction of the total number of OFDM symbols used for the PRACH preamble. In this case, the radio unit 504 averages the symbols a1 to a1 generated by the first accumulation period (i.e., the period corresponding to the first N OFDM symbols). The baseband unit 506 then transmits the average symbol a1 generated by the second accumulation period (i.e., the period corresponding to the next N OFDM symbols) to the baseband unit 506. is transmitted to the baseband unit 506 separately, and so on. Therefore, the radio unit 504 outputs a set of average symbols a1 to a1 for each accumulation period. Each of these averaged PRACH symbol groups is then processed by PRACH processing and detection circuitry 520 of baseband unit 506 as described below.

[0068] At the PRACH processing and detection circuit 520 of the baseband unit 506, the narrowband received signals (i.e., non-averaged OFDM symbols) from the narrowband receivers 516-1 to 516-N A or, alternatively, the averaged symbols from the accumulation circuits 518-1 to 518-N A are processed by the FFTs 700-1 to 700-N A and the frequency-to-beam domain transformation circuit 702. The FFTs 700-1 to 700-N A and the frequency-to-beam domain transformation circuit 702 operate as follows. The following discussion assumes the existence of the accumulation circuits 518. If the accumulation circuits 518 exist and there are multiple sets of averaged OFDM symbols, the process is repeated for each set of averaged OFDM symbols. However, it should be noted that if the accumulation circuits 518 do not exist, the described processing is applied to the narrowband received signals (i.e., non-averaged OFDM symbols) output by the narrowband receivers 516.

[0069] FFT 700-1 transforms the averaged symbol a1 from the time domain to the frequency domain, thereby providing a frequency domain representation of the averaged PRACH symbol a1. This frequency domain representation includes the outputs for each subcarrier of the PRACH (i.e., each subcarrier of the RACH opportunity for which the PRACH preamble detection is being performed). These outputs are represented as c Figure 7 in 1，1 to where for c x，y , x is the index of the corresponding antenna element, y is the index of the corresponding subcarrier, and N SC is the total number of subcarriers in the PRACH. Similarly, FFT 700-2 operates to transform the averaged PRACH symbol a2 from the time domain to the frequency domain, thereby providing a frequency domain representation of the averaged PRACH symbol a2, and so on.

[0070] Although not shown, additional processing may be performed, such as, after the FFTs 700, extracting only those (averaged) OFDM symbols corresponding to the PRACH opportunities for which each ongoing detection is being performed.

[0071] The frequency-to-beam domain transformation circuit 702 transforms all of the outputs of the FFTs 700-1 to 700-N A from the antenna domain to the beam domain, thereby providing beam domain outputs for each subcarrier of each receive beam for which the PRACH preamble is to be searched. In Figure 7 , the beam domain outputs are represented as b x，y , where here x is the index of the corresponding beam, and y is the index of the corresponding subcarrier, N SC is the total number of subcarriers in the PRACH, and N Bis the total number of receive beams. Thus, as an example, the beam domain output b i，1 to is the frequency domain representation of the average symbol received on the i-th receive beam. It should be noted that the frequency-beam transformation can be performed by applying beamforming weights corresponding to the transmit beam of the SSB transmission mapped to the RACH occasion for which the PRACH preamble detection being performed is targeted.

[0072] For each set of averaged PRACH symbols, the corresponding beam domain output generated by the frequency-to-beam domain transformation circuit 702 is passed to the PRACH detector 704. Figure 8 Details of an exemplary embodiment of the PRACH detector 704 are shown in. As Figure 8 shown in, for each i-th receive beam (for i = 1,..., N B ), the PRACH detector 704 includes matched filters 800-i(1) to 800-i(N SC ), which perform matched filtering on the beam domain output b i，1 to of the i-th receive beam based on the frequency domain representation of the PRACH preamble (also referred to herein as the PRACH sequence) for which the detection being performed is targeted. This matched filtering can be repeated for each of a plurality of possible PRACH sequences.

[0073] For each i-th receive beam (for i = 1,..., N B ), the outputs of the matched filters 800-i(1) to 800-i(N SC ) of the i-th receive beam are transformed from the frequency domain to the time domain by the corresponding inverse FFT (IFFT) 804-i. The time domain output of the IFFT 804-i is recalculated by the corresponding magnitude squared calculation circuit 806-i. The magnitude squared value of the i-th receive beam is passed to the non-coherent combining circuit 808-i for the i-th beam. The non-coherent combining circuit 808-i is optional and operates to non-coherently combine the magnitude squared values of the outputs of the IFFT 804-i obtained from averaged PRACH symbols with the magnitude squared values of the outputs of the IFFT 804-i obtained from additional averaged PRACH symbols. This is the case if the number of accumulated PRACH symbols (N) is part of the total number of PRACH symbols of the PRACH preamble.

[0074] The non-coherent combining circuits 808-1 to 808-N BThe output is provided to the PRACH detection circuit 810. For each i-th received beam, the PRACH detection circuit 810 determines whether a PRACH preamble is detected for the received beam based on the output of the corresponding non-coherent combining circuit 808-i, as would be understood by one of ordinary skill in the art.

[0075] It should be noted that when the scheduler of the base station 402 decides which physical channels to schedule, the scheduler sends a control command to the radio unit 504 such that the narrowband receiver 516 is configured to select the appropriate frequency carrier and frequency (and optionally, time) resources for the PRACH occasion for which the PRACH preamble detection is to be performed. It should also be noted that the scheduler also decides how to utilize the PRBs outside the bandwidth of the narrowband receiver 516 on the same symbol. The signals / physical channels scheduled on those PRBs will be received by the wideband receiver 508.

[0076] Figure 9 is a flowchart showing the operation of the base station 402 according to an embodiment of the present disclosure. As shown, the base station 402 transmits a plurality of SSBs on a plurality of corresponding beams according to a beam scanning scheme (step 900). According to an N-to-1 mapping scheme, the plurality of SSBs are mapped to one or more RACH occasions, where N>1. In one embodiment, as described above, all the SSBs are mapped to a single PRACH occasion.

[0077] In another embodiment, the beam directions of the beams transmitting the SSBs are divided into two or more groups of directions, thereby dividing the SSBs into two or more groups of SSBs. As described above, the two or more groups of SSBs are mapped to two or more corresponding PRACH occasions. It should be noted that the groups of directions are mutually exclusive, whereby the groups of SSBs are mutually exclusive, such that each beam direction / SSB is only in one group. In addition, each group of directions includes those beam directions that are adjacent to each other (i.e., adjacent or close to each other in space). For example, consider a simplified scenario where the beam directions form a two-dimensional (2D) circle. Then, as an example, the beam directions from 0 degrees to 180 degrees around the origin of the 2D circle can be in the first group of directions, while the beam directions from 180 degrees to 360 degrees around the origin of the 2D circle can be in the second group of directions. In this way, the narrowband receiver 516 at the base station 402 can be used to perform PRACH preamble reception and detection for each group of directions during the corresponding PRACH occasion.

[0078] For each PRACH occasion among one or more PRACH occasions mapped to an SSB, the base station 402 (more specifically, the narrowband receiver 516 and the PRACH processing and detection circuitry 520 at the base station 402) performs PRACH preamble reception and detection as follows. For each PRACH occasion, the base station 402 processes the received signals from at least one subset of antenna elements 502-1 to 502-N A using the narrowband receiver 516 to provide a narrowband received signal, as described above (step 902). The narrowband received signal is also referred to herein as an OFDM symbol. Optionally, as described above, the processing includes accumulation or averaging of OFDM symbols.

[0079] As described above, based on the narrowband received signal (or optionally, the accumulated OFDM symbols), the base station 402 (more specifically, the PRACH processing and detection circuitry 520) performs PRACH preamble detection for a plurality of beam directions (step 904), where the plurality of beam directions are the beam directions for transmitting the SSB mapped to the PRACH occasion in step 900. Importantly, as described above, by using the narrowband receiver 516 to listen for PRACH preambles simultaneously in multiple directions during a single PRACH occasion, the amount of time required to perform PRACH preamble detection after scanning the SSB beam is significantly reduced, and the frequency resource utilization is significantly improved. It should be noted that Figure 7 and Figure 8 shows an example of the processing of step 904; however, the present disclosure is not limited thereto. Those skilled in the art will understand that the processes for PRACH processing and detection can vary. Thus, any suitable PRACH processing and detection process can be used. Once a PRACH preamble is detected, the base station 402 can continue the random access procedure in a conventional manner, for example, as would be understood by those of ordinary skill in the art. In one embodiment, the base station 402 can further process the received PRACH signal to determine a more accurate beam direction with a higher beamforming gain (step 906). The newly determined beam direction can be directly applied to the random access response and / or the signaling after the random access response. This can significantly improve the link budget.

[0080] Figure 10is a schematic block diagram of a radio access node 1000 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node 1000 can be, for example, a base station 402 or a network node that implements all or part of the functions of the base station 402 described herein. As shown, the radio access node 1000 includes a control system 1002, which includes one or more processors 1004 (e.g., a central processing unit (CPU), an ASIC, a field-programmable gate array (FPGA), etc.), a memory 1006, and a network interface 1008. The one or more processors 1004 are also referred to herein as processing circuitry. In addition, the radio access node 1000 includes one or more radio units 1010, each radio unit including one or more transmitters 1012 and one or more receivers 1014 coupled to one or more antennas 1016. The radio units 1010 can be referred to as radio interface circuitry or a part thereof. In some embodiments, the radio units 1010 are external to the control system 1002 and are connected to the control system 1002 via, for example, a wired connection (e.g., an optical cable). However, in some other embodiments, the radio units 1010 and possibly the antennas 1016 are integrated with the control system 1002. The one or more processors 1004 operate to provide one or more functions of the radio access node 1000 as described herein (e.g., one or more functions of the base station 402 described herein). For example, in one embodiment, the one or more processors 1004 implement the functions of the baseband unit 506 described above. In addition, in some embodiments, the functions of the radio unit 504 described above are implemented in the radio units 1010.

[0081] Figure 11 is a schematic block diagram showing a virtualized embodiment of a radio access node 1000 according to some embodiments of the present disclosure. This discussion equally applies to other types of network nodes. In addition, other types of network nodes can have a similar virtualized architecture. Again, optional features are represented by dashed boxes.

[0082] As used herein, a "virtualized" radio access node is an implementation of radio access node 1000, where at least a portion of the functionality of radio access node 1000 is implemented as virtual components (e.g., implemented via virtual machines executing on physical processing nodes in the network). As shown, in this example, as described above, radio access node 1000 may include control system 1002 and / or one or more radio units 1010. Control system 1002 may be connected to radio unit 1010 via, for example, an optical cable or the like. Radio access node 1000 includes one or more processing nodes 1100, which are coupled to network 1102 or are included as part of network 1102. If present, control system 1002 or the radio unit is connected to processing node 1100 via network 1102. Each processing node 1100 includes one or more processors 1104 (e.g., CPU, ASIC, FPGA, etc.), memory 1106, and network interface 1108.

[0083] In this example, the functionality 1110 of radio access node 1000 described herein (e.g., some or all of the functionality of baseband unit 506 of base station 402) is implemented at one or more processing nodes 1100, or distributed in any desired manner across one or more processing nodes 1100 and control system 1002 and / or radio unit 1010. In some particular embodiments, some or all of the functionality 1110 of radio access node 1000 described herein is implemented as virtual components executed by one or more virtual machines implemented in a virtual environment hosted by processing nodes 1100. As will be understood by those of ordinary skill in the art, additional signaling or communication between processing nodes 1100 and control system 1002 is used in order to perform at least some of the desired functionality 1110. It is noted that in some embodiments, control system 1002 may not be included, in which case radio unit 1010 communicates directly with processing node 1100 via an appropriate network interface.

[0084] In some embodiments, a computer program including instructions is provided, which when executed by at least one processor causes the at least one processor to perform the functionality of radio access node 1000 according to any of the embodiments described herein or a node (e.g., processing node 1100) that implements one or more of the functionality 1110 of radio access node 1000 in a virtual environment. In some embodiments, a carrier including the aforementioned computer program product is provided. The carrier is one of an electrical signal, an optical signal, a radio signal, or a computer-readable storage medium (e.g., a non-transitory computer-readable medium such as a memory).

[0085] Figure 12FIG. 0 is a schematic block diagram of a radio access node 1000 according to some other embodiments of the present disclosure. The radio access node 1000 includes one or more modules 1200, each implemented in software. The modules 1200 provide the functionality of the radio access node 1000 described herein (e.g., one or more functions of the base station 402). This discussion applies equally to Figure 11 processing node 1100, where the modules 1200 may be implemented at one of the processing nodes 1100 or distributed across multiple processing nodes 1100 and / or distributed across the processing nodes 1100 and the control system 1002.

[0086] Any suitable steps, methods, features, functions, or benefits disclosed herein may be performed by one or more functional units or modules of one or more virtual devices. Each virtual device may include a plurality of such functional units. These functional units may be implemented via a processing circuit, which may include one or more microprocessors or microcontrollers and other digital hardware, which may include a digital signal processor (DSP), dedicated digital logic, etc. The processing circuit may be configured to execute program code stored in a memory, which may include one or several types of memories, such as read-only memory (ROM), random access memory (RAM), cache memory, flash memory devices, optical storage devices, etc. The program code stored in the memory includes program instructions for executing one or more telecommunication and / or data communication protocols, and instructions for executing one or more techniques described herein. In some implementations, according to one or more embodiments of the present disclosure, the processing circuit may be used to cause the corresponding functional unit to perform the corresponding function.

[0087] Although the processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that this order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0088] At least some of the following abbreviations may be used in the present disclosure. If there is an inconsistency between the abbreviations, the usage above shall prevail. If listed multiple times below, the first listing shall prevail over any subsequent listings.

[0089] · 2D Two-dimensional

[0090] · 3GPP Third Generation Partnership Project

[0091] · 5G Fifth Generation

[0092] · 5GC Fifth Generation Core

[0093] · 5GS Fifth Generation System

[0094] ·AMF Access and Mobility Functionality

[0095] ·ASIC Application Specific Integrated Circuit

[0096] ·AUSF Authentication Server Function

[0097] ·CPU Central Processing Unit

[0098] ·DSP Digital Signal Processor

[0099] ·eNB Enhanced or Evolved Node B

[0100] ·FFT Fast Fourier Transform

[0101] ·FPGA Field Programmable Gate Array

[0102] ·GHz Gigahertz

[0103] ·gNB New Radio Base Station

[0104] ·gNB-DU New Radio Base Station Distributed Unit

[0105] ·HSS Home Subscriber Server

[0106] ·IFFT Inverse Fast Fourier Transform

[0107] ·IoT Internet of Things

[0108] ·LTE Long Term Evolution

[0109] ·MHz Megahertz

[0110] ·MIMO Multiple-Input Multiple-Output

[0111] ·MME Mobility Management Entity

[0112] ·mmW Millimeter Wave

[0113] ·MTC Machine Type Communication

[0114] ·NBR Narrowband Receiver

[0115] ·NEF Network Exposure Function

[0116] ·NF Network Function

[0117] ·ng-eNB Next Generation Enhanced or Evolved Node B

[0118] ·NG-RAN Next Generation Radio Access Network

[0119] ·NR New Radio

[0120] · NRF Network Function Repository Function

[0121] · NSSF Network Slice Selection Function

[0122] · OFDM Orthogonal Frequency Division Multiplexing

[0123] · PBCH Physical Broadcast Channel

[0124] · PC Personal Computer

[0125] · PCF Policy Control Function

[0126] · PCI Physical Cell Identifier

[0127] · P-GW Packet Data Network Gateway

[0128] · PRACH Physical Random Access Channel

[0129] · PRB Physical Resource Block

[0130] · PSS Primary Synchronization Signal

[0131] · PUSCH Physical Uplink Shared Channel

[0132] · RACH Random Access Channel

[0133] · RAM Random Access Memory

[0134] · RAN Radio Access Network

[0135] · RAT Radio Access Technology

[0136] · ROM Read Only Memory

[0137] · RRH Remote Radio Head

[0138] · SCEF Service Capability Exposure Function

[0139] · SINR Signal-to-Interference-plus-Noise Ratio

[0140] · SMF Session Management Function

[0141] · SSB Synchronization Signal Block

[0142] · SSS Secondary Synchronization Signal

[0143] · TDD Time Division Duplexing

[0144] · UDM Unified Data Management

[0145] · UE User Equipment

[0146] · UPF User Plane Function

[0147] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered to fall within the scope of the concepts disclosed herein.

Claims

1. A method for random access in a cellular communication system (400) performed by a base station (402), the method comprising: Transmitting (900) a plurality of synchronization signal blocks SSBs on respective ones of a plurality of transmit beams according to a beam scanning scheme, wherein according to an N-to-1 mapping scheme, the plurality of SSBs are mapped to one or more random access channel RACH opportunities, where N is greater than 1; and For each of the one or more RACH opportunities: Process (902) multiple received signals from at least one subset of a plurality of antenna elements (502-1 to 502-N) in an antenna array (500) of the base station (402) using a corresponding plurality of narrowband receivers (516-1 to 516-N A ), thereby providing a plurality of narrowband received signals, wherein the bandwidth of each of the plurality of narrowband receivers (516-1 to 516-N A ) is less than the bandwidth of a wideband receiver (508) of the base station (402); A ​ Performing (904) random access preamble detection on a plurality of beam directions corresponding to at least one subset of the plurality of transmit beams that transmitted at least one subset of the plurality of SSBs mapped to the RACH opportunity, based on the plurality of narrowband received signals; And Processing, by the wideband receiver, a PUSCH transmission received using physical resource blocks PRBs outside the bandwidth of the narrowband receiver during the RACH opportunity.

2. The method according to claim 1, wherein the one or more RACH opportunities include a single RACH opportunity, and all of the plurality of SSBs are mapped to the single RACH opportunity.

3. The method according to claim 1, wherein the one or more RACH opportunities include a first RACH opportunity and a second RACH opportunity, and the plurality of SSBs include a first set of SSBs mapped to the first RACH opportunity and a second set of SSBs mapped to the second RACH opportunity.

4. The method according to claim 3, wherein the first set of SSBs and the second set of SSBs are mutually exclusive.

5. The method according to claim 3 or 4, wherein the first set of SSBs is a first subset of the plurality of SSBs transmitted on a first subset of the plurality of transmit beams having beam directions that are spatially adjacent to each other, and the second set of SSBs is a second subset of the plurality of SSBs transmitted on a second subset of the plurality of transmit beams having beam directions that are spatially adjacent to each other.

6. The method according to any one of claims 1 to 4, wherein the bandwidth of each of the plurality of narrowband receivers (516-1 to 516-N A ) is equal to or greater than the bandwidth of each of the one or more RACH opportunities.

7. The method according to any one of claims 1 to 4, wherein the plurality of narrowband received signals correspond to orthogonal frequency division multiplexing OFDM symbols or accumulated OFDM symbols.

8. The method according to any one of claims 1 to 4, wherein performing (904) random access preamble detection includes detecting a random access preamble on one of the plurality of beam directions, and the method further comprises: Determining (906) a beam direction based on the detected random access preamble; And Transmitting a random access response and / or performing signaling after the random access response using (906) the determined beam direction.

9. A base station (402) for random access in a cellular communication system (400), the base station (402) comprising: A processor, and A memory storing a computer program that, when executed by the processor, causes the base station (402) to: Transmit (900) a plurality of synchronization signal blocks SSBs on corresponding multiple transmit beams according to a beam scanning scheme, wherein according to an N-to-1 mapping scheme, map the plurality of SSBs to one or more random access channel RACH opportunities, where N is greater than 1; and For each of the one or more RACH opportunities: Process (902) multiple received signals from at least one subset of multiple antenna elements (502-1 to 502-N) in an antenna array (500) of the base station (402) using a corresponding plurality of narrowband receivers (516-1 to 516-N A ), thereby providing a plurality of narrowband received signals, wherein the bandwidth of each of the plurality of narrowband receivers (516-1 to 516-N A ) is less than the bandwidth of a wideband receiver (508) of the base station (402); A ​ Based on the plurality of narrowband received signals, perform (904) random access preamble detection for a plurality of beam directions corresponding to at least one subset of the plurality of transmit beams that transmitted at least one subset of the plurality of SSBs mapped to this RACH opportunity; And Have the wideband receiver process PUSCH transmissions received using physical resource blocks PRBs outside the bandwidth of the narrowband receiver during this RACH opportunity.

10. The base station (402) according to claim 9, wherein the one or more RACH opportunities include a single RACH opportunity, and all of the plurality of SSBs are mapped to the single RACH opportunity.

11. The base station (402) according to claim 9, wherein the one or more RACH opportunities include a first RACH opportunity and a second RACH opportunity, and the plurality of SSBs include a first group of SSBs mapped to the first RACH opportunity and a second group of SSBs mapped to the second RACH opportunity.

12. The base station (402) according to claim 11, wherein the first group of SSBs and the second group of SSBs are mutually exclusive.

13. The base station (402) according to claim 11 or 12, wherein the first group of SSBs is a first subset of the plurality of SSBs transmitted on a first subset of the plurality of transmit beams having beam directions that are spatially adjacent to each other, and the second group of SSBs is a second subset of the plurality of SSBs transmitted on a second subset of the plurality of transmit beams having beam directions that are spatially adjacent to each other.

14. The base station (402) according to any one of claims 9 to 12, wherein the bandwidth of each of the plurality of narrowband receivers (516-1 to 516-N A ) is equal to or greater than the bandwidth of each of the one or more RACH opportunities.

15. The base station (402) according to any one of claims 9 to 12, wherein the plurality of narrowband received signals correspond to orthogonal frequency division multiplexing OFDM symbols or accumulated OFDM symbols.

16. The base station (402) according to any one of claims 9 to 12, wherein performing (904) random access preamble detection includes detecting a random access preamble on one of the plurality of beam directions, and the base station (402) is further adapted to: Determine (906) the beam direction based on the detected random access preamble; and Use (906) the determined beam direction for transmission of a random access response and / or for signaling after the random access response.

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