Antenna Selection for Uplink Signals in a Wireless Communication System

Abstract

An aggregation unit includes a transceiver configured to transmit unique signals to a plurality of transmission reception points (TRxPs) for transmission by the plurality of TRxPs, and to receive uplink signals received by the plurality of TRxPs from user equipment. The aggregation unit further includes a processor configured to generate a sum of the uplink signals from a subset of the plurality of TRxPs. The subset is determined based on measurements of the unique signals performed by the UE. In some cases, the subset is determined by a baseband unit that receives a measurement report including the measurements performed by the UE. The transceiver is configured to transmit the sum of the uplink signals to the baseband unit via a fronthaul link.

Description

Background Art

[0001] Wireless communication systems such as single-frequency networks (SFNs) and distributed antenna systems (DASs) are typically deployed in areas with relatively low user density distributed over a large or complex area. For example, SFN and DAS systems distribute multiple remote radio units (RRUs) to provide coverage within different rooms or floors of a building, thereby reducing the signal blocking effect of walls, floors, or other obstacles. RRUs are also referred to herein as transmission and reception points (TRxPs). Each TRxP includes one or more antennas for transmitting a downlink signal provided to the TRxP by a baseband unit (BBU) in a base station to a user equipment and receiving an uplink signal transmitted by the user equipment to the base station. In areas with low user density, each TRxP can serve a small number of users, and it is uneconomical to allocate a separate BBU to each TRxP. Instead, a single BBU is connected to multiple geographically separated TRxPs, such that there is a one-to-many relationship between the BBU and the TRxPs. A fronthaul link connects one or more ports in the BBU to corresponding ports in an aggregation unit, and the aggregation unit distributes the signal to the TRxPs. The baseband unit sends a downlink signal to the aggregation unit via the fronthaul link, and the aggregation unit forwards a copy of the downlink signal to the TRxPs. Thus, the same downlink signal is transmitted from the TRxPs simultaneously or concurrently in the same frequency band. The aggregation unit also aggregates the uplink signals received from the TRxPs, and the aggregated uplink signals are transmitted to the baseband unit via the fronthaul link. However, the bandwidth of the fronthaul link is the same (or similar) to the bandwidth of a single connection to a TRxP. Therefore, the aggregated uplink signal is generated by summing or adding the uplink signals from the TRxPs to generate a single aggregated uplink signal for transmission via the fronthaul link. Summary of the Invention

[0002] To provide a basic understanding of some aspects of the disclosed subject matter, a simplified summary of the disclosed subject matter is presented below. This summary is not an exhaustive overview of the disclosed subject matter. It is not intended to identify key or essential elements of the disclosed subject matter or to delineate the scope of the disclosed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to a more detailed description discussed later.

[0003] In some embodiments, a device is provided. Some embodiments of the device include a transceiver configured to transmit a unique signal to a plurality of transmission reception points (TRxPs) for transmission by the plurality of TRxPs, and to receive uplink signals received by the plurality of TRxPs from a user equipment. The device further includes a processor configured to generate a sum of the uplink signals from a subset of the plurality of TRxPs. The subset is determined based on measurements of the unique signal performed by the UE, and the transceiver is configured to transmit the sum of the uplink signals to a baseband unit via a fronthaul link.

[0004] In some embodiments, the unique signal includes a first synchronization signal block (SSB) transmitted by each of the plurality of TRxPs and a plurality of second SSBs selectively transmitted by different ones of the plurality of TRxPs.

[0005] Some embodiments of the transceiver are configured to transmit the first SSB to the plurality of TRxPs and different second SSBs of the plurality of second SSBs to each of the plurality of TRxPs.

[0006] Some embodiments of the transceiver are configured to transmit the first SSB to the plurality of TRxPs, transmit different second SSBs of the plurality of second SSBs to each TRxP in a first subset of the plurality of TRxPs during a first time interval, and transmit different second SSBs of the plurality of second SSBs to each TRxP in a second subset of the TRxPs during a second time interval.

[0007] Some embodiments of the transceiver are configured to transmit the first SSB to the plurality of TRxPs and transmit different combinations of the plurality of second SSBs to encode the identities of the plurality of TRxPs.

[0008] Some embodiments of the processor are configured to generate the unique signal by performing a fast Fourier transform (FFT) on a time domain signal received from the baseband unit to generate a frequency domain signal including subcarriers for the first SSB and the plurality of second SSBs, removing subcarriers associated with a subset of the second SSBs from the frequency domain signal, performing an inverse FFT (IFFT) on the frequency domain signal to form a modified time domain signal, and adding a cyclic prefix to the modified time domain signal.

[0009] Some embodiments of the processor are configured to generate the unique signal by removing unwanted subcarriers associated with the second SSBs from the frequency domain signal received from the baseband unit, performing an inverse FFT (IFFT) on the frequency domain signal to form a modified time domain signal, and adding a cyclic prefix to the modified time domain signal.

[0010] In some embodiments, the unique signal includes a channel state information reference signal (CSI-RS) transmitted by a plurality of TRxPs.

[0011] Some embodiments of the processor are configured to generate a unique signal by generating a second SSB in response to instructions received from the baseband unit.

[0012] Some embodiments of the processor are configured to generate a mask indicating a subset of the plurality of TRxPs.

[0013] Some embodiments of the processor are configured to filter the uplink signals received from the plurality of TRxPs using the mask and generate a sum by summing the filtered uplink signals.

[0014] In some embodiments, a baseband unit is provided. The baseband unit includes a transceiver configured to transmit a common signal to a plurality of transmit receive points (TRxPs) and receive a measurement report from a user equipment. The plurality of TRxPs generate unique signals based on the common signal. The measurement report indicates the signal strength of the unique signals received by the user equipment from the plurality of TRxPs. The baseband unit further includes a processor configured to select a subset of the plurality of TRxPs based on the measurement report, the subset to be used for selective summation of uplink signals subsequently received from the user equipment.

[0015] Some embodiments of the processor are configured to select a subset of the plurality of TRxPs by comparing the signal strength in the measurement report with a threshold signal strength.

[0016] Some embodiments of the processor are configured to include a TRxP in the subset in response to the corresponding signal strength exceeding the threshold signal strength.

[0017] Some embodiments of the processor are configured to generate a summation instruction. Some embodiments of the transceiver are configured to transmit the summation instruction to an aggregation unit, and the aggregation unit uses the summation instruction to configure the aggregation unit to selectively sum the uplink signals received from a subset of the set of TRxPs.

[0018] Some embodiments of the transceiver are configured to receive an aggregated uplink signal, the aggregated uplink signal being equal to the sum of the uplink signals received from a subset of the set of TRxPs.

[0019] Some embodiments of the common signal include a first synchronization signal block (SSB) and a plurality of second SSBs modified by the aggregation unit to uniquely indicate each of the plurality of TRxPs.

[0020] Some embodiments of the common signal include instructions for generating at least one of a first synchronization signal block (SSB) and a plurality of second SSBs at an aggregation unit to uniquely indicate each of a plurality of TRxPs.

[0021] In some embodiments, a method is provided. Some embodiments of the method include transmitting a unique signal to a plurality of transmit receive points (TRxPs) for the plurality of TRxPs to transmit, and receiving an uplink signal received by the plurality of TRxPs from a user equipment. The method further includes generating a sum of the uplink signals from a subset of the plurality of TRxPs. The subset is determined based on measurements of the unique signal performed by the UE. The method further includes transmitting the sum of the uplink signals to a baseband unit via a fronthaul link.

[0022] In some embodiments, the unique signal includes a first synchronization signal block (SSB) transmitted by the plurality of TRxPs and a plurality of second SSBs selectively transmitted by different TRxPs among the plurality of TRxPs.

[0023] In some embodiments, transmitting the unique signal includes transmitting a first SSB to the plurality of TRxPs and transmitting a different second SSB among the plurality of second SSBs to each of the plurality of TRxPs.

[0024] In some embodiments, transmitting the unique signal includes transmitting a first SSB to the plurality of TRxPs, and transmitting a different second SSB among the plurality of second SSBs to each TRxP in a first subset of the plurality of TRxPs in a first time interval, and transmitting a different second SSB among the plurality of second SSBs to each TRxP in a second subset of the TRxPs in a second time interval.

[0025] In some embodiments, transmitting the unique signal includes transmitting a first SSB to the plurality of TRxPs, and transmitting different combinations of the plurality of second SSBs to encode the identities of the plurality of TRxPs.

[0026] In some embodiments, generating the unique signal includes performing a fast Fourier transform (FFT) on a time domain signal received from a baseband unit to generate a frequency domain signal including subcarriers for the first SSB and the plurality of second SSBs, removing unwanted subcarriers associated with the second SSBs from the frequency domain signal, performing an inverse FFT (IFFT) on the frequency domain signal to form a modified time domain signal, and adding a cyclic prefix to the modified time domain signal.

[0027] In some embodiments, generating the unique signal includes removing unwanted subcarriers associated with the second SSBs from a frequency domain signal received from a baseband unit, performing an inverse FFT (IFFT) on the frequency domain signal to form a modified time domain signal, and adding a cyclic prefix to the modified time domain signal.

[0028] Some embodiments of the method include generating a mask indicating a subset of a plurality of TRxPs.

[0029] Some embodiments of the method include filtering an uplink signal received from a plurality of TRxPs using the mask; and generating a sum by summing the filtered uplink signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present disclosure can be better understood by reference to the accompanying drawings, and its numerous features and advantages will be apparent to those of ordinary skill in the art. Like reference numerals refer to like or identical items in the different drawings.

[0031] Figure 1 is a block diagram of a communication system implementing antenna selection for uplink signals according to some embodiments.

[0032] Figure 2 is a block diagram of a measurement report generated by a user equipment and a mask created based on the measurement report according to some embodiments.

[0033] Figure 3 is a block diagram showing a part of a wireless communication system including an aggregation unit and a fronthaul link according to some embodiments.

[0034] Figure 4 is a block diagram of a measurement report generated by a user equipment and transmitted to a base station according to some embodiments.

[0035] Figure 5 is a block diagram showing a set of synchronization signal blocks (SSBs) transmitted by a set of transmission reception points (TRxPs) according to some embodiments.

[0036] Figure 6 is a flowchart of a method for generating a unique signal for transmission by a TRxP according to some embodiments.

[0037] Figure 7 is a block diagram of a message passing sequence representing a measurement phase according to some embodiments.

[0038] Figure 8 is a block diagram of a message passing sequence representing a selective summation phase according to some embodiments.

[0039] Figure 9 is a block diagram of a communication system supporting selective summation of uplink signals from a set of TRxPs according to some embodiments. DETAILED DESCRIPTION

[0040] Since the signal, noise, and interference levels received at the TRxP of a single user equipment are different, summing all the uplink signals received from a group of TRxPs at the aggregation unit degrades the quality of the aggregated uplink signals. For example, the quality of the signal received from a user equipment is represented by the signal-to-noise ratio (SNR) or the signal-to-interference-and-noise ratio (SINR). A first user equipment (UE-A) is close to a first RRU (RRU-A), and the signal power of UE-A received at RRU-A is 5. UE-A is far from a second RRU (RRU-B), and the signal power of UE-A received at RRU-B is 2. In this example, noise is ubiquitous, and the noise power at both RRU-A and RRU-B is 1. Thus, the SNR of UE-A at RRU-A is 5 / 1 = 5, while the SNR of UE-A at RRU-B is 2 / 1 = 2. If the signals received at RRU-A and RRU-B are summed, the UE-A signal level = 5 + 2 = 7, and the combined noise level is 1 + 1 = 2. Therefore, the SNR of the combined signal is 7 / 2 = 3.5, which is lower than the SNR of the signal of UE-A received by RRU-A. As another example, if there is another user equipment (UE-B) exchanging signals with a third RRU-C belonging to an adjacent cell near RRU-B, in addition to the noise power of 1 and the UE-A signal power of 2, RRU-B also receives other signals from UE-B. If the signal power of UE-B received at RRU-B is 1, the signal strength of the combined signal of UE-A from RRU-A and RRU-B is 5 + 2 = 7 and its noise plus interference is 1 + 1 + 1 = 3, which results in a SINR of 7 / 3 = 2.3, while the SINR of the UE_A signal received at RRU-A is 5. Thus, the interference generated by UE-B and received at RRU-B further degrades the quality of the summed signal of UE-A. The degradation of the signal quality affects both the uplink (e.g., the physical uplink shared channel (PUSCH)) and the downlink. For example, because the physical uplink control channel (PUCCH) used to transmit downlink control information (e.g., an acknowledgement or a negative acknowledgement message) degrades or the sounding reference signal (SRS) transmitted by the user equipment degrades.

[0041] Figure 1 To FIG. Figure 9Embodiments of techniques for improving the quality of aggregated uplink signals transmitted over a fronthaul link between a baseband unit and an aggregation unit for a set of TRxPs by selectively summing uplink signals received from a subset of the set of TRxPs based on measurements performed by a user equipment on unique signals transmitted by a set of TRxPs associated with a base station are shown. The TRxPs in the set transmit different subsets of a first synchronization signal block (SSB) and a plurality of second SSBs within a corresponding geographical area. In some embodiments, each TRxP transmits a different second SSB among the first SSB and the plurality of second SSBs such that reception of one of the second SSBs indicates the transmitting TRxP. For example, the aggregation unit may perform a fast Fourier transform (FFT) on the time-domain signals received from the baseband unit to recover frequency-domain subcarriers and remove subcarriers of unwanted second SSBs before performing an inverse FFT (IFFT) and adding a cyclic prefix to the new time-domain signal for transmission by the TRxPs. As another example, the aggregation unit removes subcarriers of unwanted second SSBs from the frequency-domain signals received from the baseband unit before performing the IFFT and cyclic prefix addition. Some embodiments of the base station re-partition the functions between the baseband unit and the aggregation unit by moving the SSB signal generation function to the aggregation unit. In such a case, the aggregation unit generates the first SSB and the second SSB signals unique to the TRxPs based on instructions from the baseband unit. For example, the baseband unit may insert instructions for generating the first SSB and the second SSB signals unique to the TRxPs into a common downlink signal transmitted from the baseband unit to the aggregation unit.

[0042] The base station instructs the user equipment to send a measurement report indicating the signal strength of the measured second SSB. Based on the measurement report, the base station identifies a subset of TRxPs associated with the relatively stronger measured SSB signal strength, and then configures the aggregation unit to sum the uplink signals received from the user equipment through this subset. For example, the base station can set a threshold signal strength and instruct the aggregation unit to sum the uplink signals received from the user equipment through the TRxPs with signal strength (indicated in the measurement report) higher than the threshold signal strength. The uplink signals with signal strength lower than the threshold signal strength will be filtered or discarded. In some embodiments, in addition to (or instead of) measuring the signal strength of the second SSB, the base station also determines a subset of TRxPs based on the measurement of the signal strength of other signals. For example, the user equipment can measure the signal strength of the second SSB and the signal strength of the channel state information reference signal (CSI-RS) used by the user equipment to estimate the channel, and report the channel quality information (CQI) to the base station. The transmission TRxP is identified by a combination of information in the second SSB and CSI-RS, which increases the number of TRxPs uniquely identified by the transmission signal in the set. In some embodiments, the second SSB is "rotated" to different TRxPs at different time intervals to expand the number of TRxPs identified by the second SSB. In some embodiments, a combination of second SSBs is used to encode the identification of the TRxP transmitting the combination.

[0043] Figure 1 is a block diagram of a communication system 100 that implements antenna selection for uplink signals according to some embodiments. The communication system 100 implements a single-frequency network (SFN), a distributed antenna system (DAS), or other broadcast networks that support multiple geographically separated remote radio units (RRUs), which are referred to herein as transmission and reception points (TRxPs) 101, 102, 103, 104 or collectively as TRxPs 101-104. Each of the TRxPs 101-104 includes one or more antennas that support an air interface to one or more user equipment 105 via wireless connections 111, 112, 113, 114 (for clarity in Figure 1Uplink and downlink communications (only one is shown in the figure) are carried out. The wireless connections 111, 112, 113, 114 are collectively referred to as "wireless connections 111 - 114" herein. The TRxPs 101 - 104 are connected to the aggregation unit 110 via a wired connection, a wireless connection, or a combination thereof. The aggregation unit 110 is connected to the baseband unit (BBU) 115 via the fronthaul link 120, and the fronthaul link 120 supports the same (or similar) bandwidth as that supported between the aggregation unit 110 and one of the TRxPs 101 - 104. In some embodiments, the TRxPs 101 - 104, the aggregation unit 110, and the BBU 115 are collectively referred to as "base stations".

[0044] The BBU 115 provides downlink signals to the aggregation unit 110 for distribution to the TRxPs 101 - 104. Some embodiments of the BBU 115 include one or more ports 125, and the ports 125 are connected to corresponding ports in the aggregation unit 110 via the fronthaul link 120. Thus, the downlink signals are transmitted to the aggregation unit 110 via one or more ports 125. The downlink signals include frequency-domain signals that transmit symbols in one or more subcarriers at different frequencies, or time-domain signals that represent one or more symbols. The time-domain signals are converted into frequency-domain signals by using techniques such as the fast Fourier transform (FFT), and the frequency-domain signals are converted into time-domain signals by using inverse techniques such as the inverse FFT (IFFT). The aggregation unit 110 distributes the signals to the TRxPs 101 - 104, and the TRxPs 101 - 104 transmit the signals to the user equipment 105 simultaneously or concurrently via the air interface. For example, if the aggregation unit 110 transmits a frequency-domain signal having subcarriers within a frequency band, each of the TRxPs 101 - 104 transmits the same frequency-domain signal in the same frequency band simultaneously or concurrently.

[0045] The uplink signals from user equipment 105 are transmitted to the corresponding TRxPs 101-104 via wireless connections 111-114. The signals received by TRxPs 101-104 include the desired uplink signals from user equipment 105, ambient noise, and interference from other transmission entities such as other user equipment in the vicinity of one or more of TRxPs 101-104. The received signals are transmitted to aggregation unit 110, which sums the received signals from TRxPs 101-104 to form a sum signal that is transmitted to baseband unit 115 via fronthaul link 120. However, as discussed herein, due to the differences in the signal, noise, and interference levels received from user equipment 105 at TRxPs 101-104, summing the uplink signals received from all TRxPs 101-104 degrades the quality of the sum uplink signal. Thus, instead of summing all the signals received from TRxPs 101-104, aggregation unit 110 selectively sums the uplink signals received from a subset of TRxPs 101-104 that have a relatively high-quality communication link with user equipment 105.

[0046] The subset of TRxPs 101-104 is selected based on information in a measurement report generated by user equipment 105 and provided to the base station. The measurement report is generated based on measurements of unique signals transmitted by TRxPs 101-104, and the unique signals uniquely identify the TRxPs 101-104 that transmitted the unique signals. In some embodiments, a common signal is generated at BBU 115 and provided to aggregation unit 110, which generates unique signals for TRxPs 101-104 and distributes the unique signals to the corresponding TRxPs 101-104. For example, aggregation unit 110 generates a unique signal identifying TRxP 101 from the common downlink signal received from BBU 115. Aggregation unit 110 also performs other operations to customize the common downlink signal, such as removing unwanted SSBs, performing FFT / IFFT operations, and so on. Aggregation unit 110 then transmits the unique signal to TRxP 101. Aggregation unit 110 does not transmit the unique signal to TRxPs 102-104, but generates a different unique signal for each of TRxPs 102-104.

[0047] Some embodiments of the BBU 115 transmit synchronization signal blocks (SSBs), including a first SSB and one or more second SSBs, to the aggregation unit 110 via the fronthaul 120. The aggregation unit 110 distributes the first SSB to all TRxPs 101 - 104. The aggregation unit 110 also modifies one or more second SSBs to generate a set of second SSBs that uniquely identify the TRxPs 101 - 104. The (common) first SSB and the (unique, TRxP - specific) second SSBs are transmitted from the aggregation unit 110 to the TRxPs 101 - 104. In the illustrated embodiment, the aggregation unit 110 transmits the first SSB to all TRxPs 101 - 104 and different second SSBs among the second SSBs to different TRxPs 101 - 104. For example, the aggregation unit 110 transmits a signal 131 including the first SSB and the first second SSB among the second SSBs to the TRxP 101. The aggregation unit 110 also transmits a signal 132 including the first SSB and the second second SSB among the second SSBs to the TRxP 102, a signal 133 including the first SSB and the third second SSB among the second SSBs to the TRxP 103, and a signal 134 including the first SSB and the fourth second SSB among the second SSBs to the TRxP 104. The TRxPs 101 - 104 then transmit the corresponding signals 131 - 134 to the user equipment 105 via the corresponding communication links 111 - 114.

[0048] In some embodiments, the baseband unit 115 does not generate the first SSB and the second SSB. Instead, the baseband unit 115 generates instructions that are transmitted to the aggregation unit 110, and the aggregation unit 110 generates the first SSB that is common to all TRxPs 101 - 104 and unique second SSBs that identify each of the TRxPs 101 - 104, as discussed herein. Then, the first SSB is provided to all TRxPs 101 - 104, and the unique second SSBs are provided to the corresponding TRxPs 101 - 104.

[0049] The user equipment 105 receives signals 131 - 134 and identifies the corresponding TRxPs 101 - 104 based on the received signals 131 - 134. For example, the user equipment 105 receives signal 131 and identifies TRxP 101 based on the first and second SSBs received in signal 131. The user equipment 105 also performs measurements on the received signals 131 - 134. The measurements include measurements of signal strength or signal quality, such as received signal strength indicator (RSSI), reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-noise ratio (SNR), signal-to-interference-plus-noise ratio (SINR), etc. The user equipment 105 then compiles or combines the measurement results into a measurement report 135, which includes information representing the results of the measurements performed on the unique signals received from TRxPs 101 - 104. The user equipment 105 forwards the measurement report 135 to the base station. Signals 131 - 134 are transmitted, and the measurement report 135 is generated periodically, at predetermined time intervals, or in response to a triggering event.

[0050] The base station selects a subset of TRxPs 101 - 104 based on the measurement report 135 received from the user equipment 105. The selection is performed at the aggregation unit 110, the BBU 115, or another entity within the base station. In some embodiments, the base station compares the values indicating the signal strength or quality of different TRxPs 101 - 104 with a threshold. The TRxPs 101 - 104 with signal strength / quality values higher than the threshold are added to the subset, and the TRxPs 101 - 104 with signal strength / quality values lower than the threshold are not included in the subset. The threshold corresponds to the threshold proximity or path loss among TRxPs 101 - 104. The TRxPs 101 - 104 with signal strength / quality values higher than the threshold are within the proximity distance or path loss, indicating that the signals received from the user equipment 105 at the TRxPs in the subset have a relatively high SNR or SINR and should thus be summed to form a summed signal transmitted from the aggregation unit 110 to the BBU 115.

[0051] In some embodiments, the number of TRxPs 101-104 is greater than the number of available second SSBs. Therefore, additional information is used to uniquely identify the TRxPs 101-104. For example, a beam refinement signal formed using a channel state information reference signal (CSI-RS) can be combined with the second SSB to uniquely identify a larger number of TRxPs 101-104. In this case, the base station combines the measurements based on the SSB with the CSI-RS basic measurements to determine whether one of the TRxPs 101-104 should be added to the subset for selective summation. As another example, the second SSB can rotate among the TRxPs 101-104 at different time intervals. Thus, different TRxPs are identified by the same second SSB transmitted at different time intervals, such as the second SSB transmitted by TRxP 101 in the first time interval and the same second SSB transmitted by TRxP 102 in the second time interval. For yet another example, a subset of the second SSBs can be used to encode the identification of the TRxPs 101-104. Then different TRxPs are identified by different combinations of the second SSBs. For example, TRxP 101 is uniquely identified based on receiving the first second SSB and the second second SSB among the second SSBs, and TRxP 102 is uniquely identified based on receiving the third second SSB and the fourth second SSB among the second SSBs.

[0052] The information indicating the selected subset of the TRxPs 101-104 is then transmitted to the aggregation unit 110, and the aggregation unit 110 uses this information to generate a mask or otherwise filter the uplink signals associated with the user equipment 105 received from the TRxPs 101-104. The mask or filter is implemented in the aggregation unit 110 or other entities connected to the aggregation unit 110. Based on the mask, the aggregation unit 110 sums the uplink signals received from the selected subset of the TRxPs 101-104. For example, if the mask indicates that TRxP 101 and TRxP 103 are in the selected subset, the aggregation unit 110 generates a sum signal by summing the uplink signals received from TRxP 101 and TRxP 103, while ignoring, discarding, or filtering the uplink signals received from TRxP 102 and TRxP 104. The aggregation unit 110 then transmits the sum signal to the BBU 115 via the fronthaul link 120.

[0053] Figure 2 is a block diagram of a measurement report 205 generated by a user equipment and a mask 210 created based on the measurement report 205 according to some embodiments. The measurement report 205 is generated by Figure 1 some embodiments of the user equipment 105 shown, and the mask is created by Figure 1 some embodiments of the aggregation unit 110 shown.

[0054] The measurement report 205 includes information indicating values of signal strength or quality indicators determined based on measurements of signals received (and uniquely identified) from a set of TRxPs. In the illustrated embodiment, the value 211 represents the signal strength / quality of the first SSB transmitted by all TRxPs in the set. The values 212, 213, 214, 215, 216, 217, 218 (collectively referred to herein as "values 212-218") represent the signal strength or quality of the second SSB received from the corresponding TRxP. Each of the second SSBs uniquely identifies one of the TRxPs. Thus, up to seven TRxPs are uniquely identified by the second SSBs that are measured to generate the values 212-218. In some embodiments, the number of TRxPs uniquely identified by the signals received at the user equipment is increased by using additional signals (such as CSI-RS), transmitting the second SSB in multiple time intervals, or encoding the identification of the TRxP using different combinations of the second SSB.

[0055] The baseband unit in the base station compares the values 212-218 with a threshold 220. The TRxPs associated with values 212-218 that are greater than the threshold 220 are added to the subset, and the TRxPs associated with values 212-218 that are less than the threshold 220 are not added to the subset. In the illustrated embodiment, the TRxPs associated with the values 212, 214, 215 are added to the subset. The information indicating the subset is then transmitted to an aggregation unit (such as Figure 1 the illustrated aggregation unit 110), and the aggregation unit uses this information to define a mask 210 to select uplink signals from the corresponding TRxPs. In the illustrated embodiment, the mask 210 includes seven elements corresponding to the seven TRxPs associated with the values 212-218. The elements 221, 222, 223 are "enabled" to indicate that the uplink signals received from the corresponding TRxPs are summed to create a summed uplink signal that is transmitted from the aggregation unit to the baseband unit. The remaining elements are crosshatched to indicate that the uplink signals received from the corresponding TRxPs are not summed to create a summed uplink signal.

[0056] Figure 3 is a block diagram showing a portion 300 of a wireless communication system including an aggregation unit 305 and a fronthaul link 310 according to some embodiments. The aggregation unit 305 is used to implement Figure 1 some embodiments of the illustrated aggregation unit 110, and the fronthaul link 310 is used to implement Figure 1 some embodiments of the illustrated fronthaul link 120.

[0057] The aggregation unit 305 receives a set of uplink signals 315 from a corresponding set of TRxPs. The set of uplink signals 315 is filtered by using a mask 320, such as Figure 2 some embodiments of the mask 210 as shown. The elements 321, 322, 323 of the mask 320 are enabled to indicate a subset of the set of uplink signals 315 that will be summed to create a summed uplink signal for transmission to the baseband unit, such as Figure 1 the baseband unit 115 as shown. The aggregation unit 305 thus filters the set of uplink signals 315 to generate a subset including uplink signals 325, 326, 327, which are collectively referred to herein as "subset 325-327". The aggregation unit 305 then sums the subset 325-327 to form a summed uplink signal 330, which is provided to the fronthaul link 310 for transmission to the baseband unit.

[0058] Figure 4 is a block diagram of a measurement report 400 generated by a user equipment and transmitted to a base station according to some embodiments. The measurement report 400 represents Figure 2 some embodiments of the measurement report 205 as shown. The measurement report 400 is generated by the user equipment based on measurements performed on unique signals received from a set of TRxPs (such as the measurements performed by the user equipment 105 on Figure 1 the TRxPs 101-104 as shown). The measurement report 400 includes entries for the set of TRxPs detected by the user equipment. The first column in the entries includes information indicating the identity of the TRxP, which is generated based on the information carried by the unique signal transmitted by the TRxP. For example, the measurement report 400 includes entries for TRxP-1, TRxP-2, TRxP-3, TRxP-4, and TRxP-N. The second column in the entries includes information indicating the measured signal strength of one or more signals received from the TRxP, such as one or more SSBs, CSI-RS, etc. For example, the measurement report 400 includes values indicating that the signal strength of the unique signal transmitted by TRxP-1 is 4, the signal strength of the unique signal transmitted by TRxP-2 is 8, the signal strength of the unique signal transmitted by TRxP-3 is 10, the signal strength of the unique signal transmitted by TRxP-4 is 2, and the signal strength of the unique signal transmitted by TRxP-N is 3.

[0059] Figure 5FIG. is a block diagram showing a set 500 of synchronization signal blocks (SSBs) transmitted by a set of TRxPs according to some embodiments. The set 500 includes a first SSB 501 transmitted by all the TRxPs in the set and second SSBs 502, 503, 504, 505, 506, 507, 508 that are transmitted to uniquely identify the TRxPs in the set. The first SSB 501 and the second SSBs 502, 503, 504, 505, 506, 507, 508 are collectively referred to herein as "SSB 501-508". Different SSBs in the SSB 501-508 include different information. As discussed herein, in some embodiments, each of the second SSBs 502-508 includes information (such as coding or pattern) for uniquely identifying one of the TRxPs in the set of TRxPs. Alternatively, the second SSBs 502-508 may rotate among a subset of the set of TRxPs to uniquely identify the TRxPs in the subset at different time intervals. The combination of the second SSBs 502-508 may also be used to encode the identification of the TRxPs.

[0060] The SSB 501-508 are transmitted from a baseband unit (such as Figure 1 the baseband unit 115 shown) to an aggregation unit (such as Figure 1 the aggregation unit 110 shown) during a time slot 510 of an SSB burst 515. Some embodiments of the aggregation unit modify the second SSBs 502-508 to uniquely identify the corresponding TRxPs. In some embodiments, the SSB burst 515 occupies a portion of a half-frame 520, and its duration may be 5 ms. The SSB burst 515 repeats after a predetermined time interval or periodically 525 (such as periodically every 20 ms). In the illustrated embodiment, the first SSB 501 is a primary SSB that covers the entire coverage area of the base station (e.g., the coverage area of an SFN or DAS). Although Figure 5 the illustrated SSB 501-508 have equal transmission power, in some embodiments, the SSB 501-508 have different transmission powers. For example, the SSBs 502-508 may optionally have a lower transmission power than the SSB 501 to avoid potential beam selection. Thus, the user equipment does not use one of the SSBs 502-508 for uplink random access or RACH transmission. The base station that generates the SSB 501-508 instructs the user equipment to perform measurements on the SSB 501-508 during an SSB scanning period (e.g., in the SSB burst 515 of the half-frame 520).

[0061] The maximum number of SSBs 501-508 transmitted during a period 525 is typically fixed at a predetermined number, such as four, eight, or 64, depending on factors including subcarrier spacing and carrier frequency range. The number of uniquely identified TRxPs is extended beyond the maximum number using one or more of the following techniques.

[0062] In some embodiments, CSI-RS signals, such as tracking reference signals, are combined with SSBs to generate additional unique signals for a large number of TRxPs. For example, if the maximum number of SSBs is 8, then 7 secondary SSBs can be used to uniquely identify TRxPs. If the base station uses additional physical resource blocks to transmit two sets of CSI-RS at different frequency-time resource locations, combining the CSI-RS with the SSBs generates 14 unique signals for uniquely identifying 14 TRxPs. Some embodiments of the aggregation unit modify the CSI-RS and the secondary SSBs 502-508 to form unique signals. The user equipment then provides a measurement report that includes information indicating values of measurements performed on the SSB and CSI-RS signals. As discussed herein, the base station uses the measurement report to determine whether an uplink signal received from a TRxP should be included in the summed uplink signal.

[0063] In some embodiments, the secondary SSBs are rotated across a set of TRxPs in different time intervals. For example, if there are seven available secondary SSBs 502-508 and fourteen TRxPs, a first subset of seven TRxPs transmits the seven secondary SSBs 502-508 in a first time interval, while a second subset of the other seven TRxPs transmits the seven secondary SSBs 502-508 in a second time interval. The user equipment generates different measurement reports for different time intervals, and the base station combines the measurement reports to determine the TRxPs included in the subset for uplink signal summation.

[0064] In some embodiments, different combinations of the second SSBs 502 - 508 are used to encode the identification of the TRxPs. For example, the first TRxP transmits the first second SSB among the second SSBs 502 - 508 and the fifth second SSB among the second SSBs 502 - 508, while the second TRxP transmits the first second SSB among the second SSBs 502 - 508 and the sixth second SSB among the second SSBs 502 - 508. Thus, a user equipment reporting strong signal strength (or quality) on the first second SSB among the second SSBs 502 - 508 and the sixth second SSB among the second SSBs 502 - 508 may be close to the second TRxP. If combinations of two second SSBs are used to identify the TRxPs, the encoded representation provides 7! / (2! 5!) = 21 unique combinations to identify different TRxPs. The base station combines multiple SSB measurements and uses the result to decode the identification of the TRxP and select a subset of the TRxPs for uplink signal summation. The above description of SSB 501 as the first SSB and SSB 502 - 508 as the second SSBs is intended as a non - limiting example. Those of ordinary skill in the art should understand that in other embodiments, the first SSB is selected from any subset of SSB501 - 508, and the second SSB is selected from the remaining subset of SSB 501 - 508.

[0065] Figure 6 is a flowchart of a method 600 for generating unique signals for TRxP transmission according to some embodiments. Method 600 is implemented in some embodiments of the TRxPs 101 - 104 shown in Figure 1 As discussed herein, the baseband unit transmits a common signal to the aggregation unit, and the aggregation unit uses the common signal to generate unique signals to be transmitted by a group of TRxPs. In the illustrated embodiment, the baseband unit transmits a time - domain signal including symbols representing the common signal.

[0066] In block 605, the aggregation unit receives the time - domain signal transmitted by the baseband unit and generates unique signals from the received time - domain signal. The time - domain signal includes symbols representing the common signal generated by the baseband unit. However, as discussed herein, different subsets of the unique signals are transmitted to uniquely identify the corresponding TRxPs. In some embodiments, the time - domain signal includes symbols representing the first SSB and the second SSB for transmission on sub - carriers at different frequencies. The TRxPs are identified by transmitting different second SSBs or different combinations of second SSBs. The aggregation unit thus extracts the signals to be transmitted by the TRxPs and masks out the signals that will not be required to be transmitted by the TRxPs.

[0067] In block 610, the aggregation unit performs an FFT to convert the time - domain signal into a frequency - domain signal including multiple sub - carriers. The FFT is performed on a per - symbol basis to recover the frequency - domain sub - carriers of each symbol.

[0068] At block 615, the aggregation unit removes or masks out unwanted subcarriers from the frequency-domain signal. In some embodiments, masking out unwanted subcarriers is performed by setting the subcarriers to zero. Different masks are used to remove different sets of unwanted second SSBs to generate a unique signal for transmission to different TRxPs. For example, if the aggregation unit is generating a unique signal for transmission by a first TRxP identified by a first second SSB in a second SSB transmitted by a first subcarrier, the aggregation unit masks out the other subcarriers such that only the first subcarrier remains in the frequency-domain signal. As discussed herein, the subcarriers associated with the first SSB are also included in the frequency-domain signal because the first SSB is transmitted by all TRxPs.

[0069] At block 620, the aggregation unit performs an IFFT to convert the frequency-domain signal into a time-domain signal. Thus, the time-domain signal generated by the aggregation unit includes only information representing the unique signals transmitted by the TRxPs.

[0070] At block 625, the aggregation unit appends a cyclic prefix to the time-domain signal.

[0071] At block 630, the aggregation unit transmits the time-domain signal with the appended cyclic prefix to the corresponding TRxP, which uses the time-domain signal to generate a unique signal for transmission to the user equipment.

[0072] In some embodiments, the baseband unit transmits the frequency-domain signal directly to the aggregation unit, or the aggregation unit generates a frequency-domain signal in which all first SSBs and second SSBs are enabled based on information received from the baseband unit. In this case, the aggregation unit generates a unique signal by removing (or masking out) the subcarriers of the symbols associated with the unwanted second SSBs, e.g., by setting these subcarriers to zero, as at block 615. Different masks are used to remove different sets of unwanted second SSBs to generate a unique signal for transmission to different TRxPs. The aggregation unit then continues method 600 by performing an IFFT on the filtered frequency-domain signal (at block 620), appending a cyclic prefix (at block 625), and transmitting the time-domain signal to the TRxP (at block 630).

[0073] Figure 7 is a block diagram representing a messaging sequence 700 of a measurement phase according to some embodiments. The messaging sequence 700 includes messages exchanged by a baseband unit (BBU) and an aggregation unit (AU), a set of TRxPs, and a user equipment (UE). Thus, the messaging sequence 700 is implemented in some embodiments of the communication system 100 shown in Figure 1 FIG.

[0074] The BBU transmission (at arrow 705) represents information of the downlink signal for transmission by the set of TRxPs. As discussed herein, the information includes a frequency-domain signal or a time-domain signal representing the symbols.

[0075] At block 710, the AU generates a TRxP-specific downlink signal that uniquely identifies the corresponding TRxP. In some embodiments, the AU uses Figure 6 some embodiments of the method 600 shown to generate the TRxP-specific downlink signal. The AU transmits the TRxP-specific downlink signal to the corresponding TRxP at arrow 715.

[0076] At block 720, each of the TRxPs transmits its corresponding TRxP-specific downlink signal to the UE, as shown by arrow 725. The user equipment performs signal strength or quality measurements on the received TRxP-specific downlink signals and generates a measurement report at block 730. The measurement report is then transmitted to the set of TRxPs, as shown by arrow 735.

[0077] As shown by arrow 740, each of the TRxPs forwards the received uplink signal including the measurement report from the UE to the AU. The AU then performs a complete summation on all the received uplink signals from all the TRxPs to form a summed uplink signal including the measurement report. As shown by arrow 750, the summed uplink signal is transmitted to the BBU, and the BBU determines (at block 755) a subset of TRxPs that will be used to selectively sum the subsequently received signals from the UE.

[0078] Figure 8 is a block diagram of a message passing sequence 800 representing a selective summation phase according to some embodiments. The message passing sequence 800 includes messages exchanged by a baseband unit (BBU) and an aggregation unit (AU), a set of TRxPs, and a user equipment (UE). Thus, the message passing sequence 800 is implemented in Figure 1 some embodiments of the communication system 100 shown. Some embodiments of the message passing sequence 800 are performed after Figure 7 the message passing sequence 700 shown.

[0079] At block 805, the BBU generates a summation instruction that is used to configure the AU to selectively sum the uplink signals received from a subset of the set of TRxPs, the subset being previously determined by the BBU based on the measurement report, e.g., Figure 7 in block 755 of the message passing sequence 700 shown. The summation instruction is transmitted to the AU, as shown by arrow 810, and the AU uses the summation instruction to configure a mask, such as Figure 2 the mask 210 shown. At this time, as shown by the dashed line 815, the AU selectively sums the uplink signals received from the UE based on the mask.

[0080] At block 820, the UE generates an uplink signal for transmission to a base station including a BBU and an AU. The UE transmits the uplink signal to the set of TRxPs, as shown by arrow 825.

[0081] As shown by arrow 830, each of the TRxPs transmits a signal representing the uplink signal 825 received from the UE to the AU. The AU then selectively sums (at block 835) the uplink signals received from a subset of the TRxPs, which are indicated in the summation instruction received in message 810. Some embodiments of the AU perform selective summation, as discussed with respect to Figure 3 . The AU uses the selective summation of the uplink signals received from the TRxP subset to form a summation signal and provides the summation signal to the BBU, as shown by arrow 840.

[0082] Figure 9 is a block diagram of a communication system 900 that supports selective summation of uplink signals from a set of TRxPs according to some embodiments. The communication system 900 includes a baseband unit 905, an aggregation unit 910, and a UE 915. Thus, the communication system 900 represents Figure 1 some embodiments of the communication system 100 shown. The baseband unit 905 is connected to the aggregation unit 910 via a fronthaul link 920, and the aggregation unit 910 distributes / merges signals for a set of TRxPs 921, 922, 923 (collectively referred to herein as "the set of TRxPs 921-923").

[0083] The baseband unit 905 includes a transceiver 925 that is used to transmit and receive signals with the aggregation unit 910 via the fronthaul link 920. The transceiver 925 can be implemented as a single integrated circuit (e.g., using a single ASIC or FPGA) or as a system-on-chip (SOC) including different modules for implementing the functions of the transceiver 925. The baseband unit 905 also includes a processor 930 and a memory 935. The processor 930 can be used to execute instructions stored in the memory 935 and store information in the memory 935, such as the results of the executed instructions. The baseband unit 905 is thus capable of performing Figure 6 the method 600 shown as well as Figure 7 and Figure 8 some embodiments of the corresponding messaging sequences 700 and 800 shown.

[0084] The aggregation unit 910 includes a transceiver 940, which is used to transmit and receive signals with the baseband unit 905 via the fronthaul link 920 and the TRxPs 921 - 923. The transceiver 940 can be implemented as a single integrated circuit (e.g., using a single ASIC or FPGA) or as a system-on-chip (SOC) including different modules for implementing the functions of the transceiver 940. The aggregation unit 910 also includes a processor 945 and a memory 950. The processor 940 can be used to execute instructions stored in the memory 950 and store information in the memory 950, such as the results of the executed instructions. The aggregation unit 910 is thus capable of executing Figure 6 the method 600 shown as well as Figure 7 and Figure 8 some embodiments of the corresponding messaging sequences 700 and 800 shown as well.

[0085] The user equipment 915 includes a transceiver 955, which is used to exchange signals with the set of TRxPs 921 - 923 via the air interface. The transceiver 955 can be implemented as a single integrated circuit (e.g., using a single ASIC or FPGA) or as a system-on-chip (SOC) including different modules for implementing the functions of the transceiver 955. The user equipment 915 also includes a processor 960 and a memory 965. The processor 960 can be used to execute instructions stored in the memory 965 and store information in the memory 965, such as the results of the executed instructions. The user equipment 915 is thus capable of executing Figure 6 the method 600 shown as well as Figure 7 and Figure 8 some embodiments of the corresponding messaging sequences 700 and 800 shown as well.

[0086] In some embodiments, certain aspects of the above technologies can be implemented by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer-readable storage medium. The software can include instructions and certain data, which, when executed by one or more processors, manipulate the one or more processors to perform one or more aspects of the above technologies. The non-transitory computer-readable storage medium can include, for example, disk or optical storage devices, solid-state storage devices (such as flash memory, cache, random access memory (RAM), or other non-volatile memory devices), etc. The executable instructions stored on the non-transitory computer-readable storage medium can be source code, assembly language code, object code, or other instruction formats that can be interpreted or otherwise executed by one or more processors.

[0087] A computer-readable storage medium can include any storage medium or combination of storage media that can be accessed by a computer system during use to provide instructions and / or data to the computer system. Such storage media can include, but are not limited to, optical media (e.g., compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs), magnetic media (e.g., floppy disks, magnetic tapes, or hard magnetic drives), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer-readable storage medium can be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., magnetic hard drive), removably attached to the computing system (e.g., optical disc- or universal serial bus (USB)-based flash memory), or coupled to the computer system via a wired or wireless network (e.g., network-attached storage (NAS)).

[0088] As used herein, the term "circuitry" can refer to one or more or all of the following:

[0089] (a) only hardware circuit implementations (such as only implementing analog and / or digital circuitry), and

[0090] (b) a combination of hardware circuits and software, such as (where applicable):

[0091] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0092] (ii) any portion of a hardware processor with software (including a digital signal processor, software, and memory, which work together to cause a device such as a mobile phone or server to perform various functions), and

[0093] (c) hardware circuits and / or processors, such as a microprocessor or a portion of a microprocessor, that require software (e.g., firmware) to operate but the software can be absent when not needed for operation.

[0094] The definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also encompasses implementations of only hardware circuits or processors (or multiple processors) or portions of hardware circuits or processors and their (or their) accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also encompasses a baseband integrated circuit or a processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0095] Note that not all activities or elements described in the above general description are required, that a particular activity or device part may not be needed, and that one or more other activities may be performed or other elements may be included, in addition to those described. Also, the order in which the listed activities are presented is not necessarily the order in which they are to be performed. Further, these concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the following claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0096] Benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, a benefit, an advantage, a solution to a problem, or any feature that may cause any benefit, advantage, or solution to occur or become more apparent is not to be construed as a critical, required, or essential feature of any or all the claims. Further, the specific embodiments disclosed above are illustrative only and not restrictive, since the disclosed subject matter may be modified and practiced in different but equivalent manners by those of ordinary skill in the art who benefit from the teachings herein. The details of the construction or design shown herein are not intended to be limiting other than as set forth in the following claims. It is, therefore, evident that the specific embodiments disclosed above may be altered or modified and all such variations are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the following claims.

Claims

1. A device for communication, comprising: a transceiver configured to transmit a unique signal to a plurality of transmission reception points (TRxPs) for transmission by the plurality of TRxPs, and to receive an uplink signal received by the plurality of TRxPs from a user equipment; and a processor configured to generate a sum of the uplink signals from a subset of the plurality of TRxPs, wherein the subset is determined based on measurements of the unique signal performed by the user equipment, and wherein the transceiver is configured to transmit the sum of the uplink signals to a baseband unit via a fronthaul link, wherein the unique signal includes a first synchronization signal block (SSB) and a plurality of second SSBs, the first SSB being transmitted by each of the plurality of TRxPs, and the plurality of second SSBs being selectively transmitted by different ones of the plurality of TRxPs; wherein the transceiver is configured to transmit the first SSB to the plurality of TRxPs, and wherein the transceiver is configured to transmit different combinations of the plurality of second SSBs to encode the identities of the plurality of TRxPs.

2. The device according to claim 1, wherein the transceiver is configured to transmit the first SSB to the plurality of TRxPs and different second SSBs among the plurality of second SSBs to each of the plurality of TRxPs.

3. The device according to claim 1, wherein the transceiver is configured to transmit the first SSB to the plurality of TRxPs, and wherein the transceiver is configured to transmit different second SSBs among the plurality of second SSBs to each TRxP in a first subset of the plurality of TRxPs in a first time interval, and to transmit the different second SSBs among the plurality of second SSBs to each TRxP in a second subset of the TRxPs in a second time interval.

4. The device according to claim 1, wherein the processor is configured to generate the unique signal by: performing a fast Fourier transform (FFT) on a time-domain signal received from the baseband unit to generate a frequency-domain signal, the frequency-domain signal including subcarriers for the first SSB and the plurality of second SSBs, removing subcarriers associated with a subset of the second SSBs from the frequency-domain signal, performing an inverse FFT (IFFT) on the frequency-domain signal to form a modified time-domain signal, and adding a cyclic prefix to the modified time-domain signal.

5. The device according to claim 1, wherein the processor is configured to generate the unique signal by: removing unwanted subcarriers associated with second SSBs from a frequency-domain signal received from the baseband unit, performing an inverse FFT (IFFT) on the frequency-domain signal to form a modified time-domain signal, and adding a cyclic prefix to the modified time-domain signal.

6. The device according to claim 1, wherein the unique signal includes a channel state information reference signal (CSI-RS) transmitted by the plurality of TRxPs.

7. The apparatus according to claim 1, wherein the processor is configured to generate the unique signal by generating the second SSB in response to an instruction received from the baseband unit.

8. The apparatus according to claim 1, wherein the processor is configured to generate a mask indicating the subset of the plurality of TRxPs.

9. The apparatus according to claim 8, wherein the processor is configured to filter an uplink signal received from the plurality of TRxPs using the mask, and generate the sum by summing the filtered uplink signal.

10. A baseband unit, comprising: a transceiver configured to transmit a common signal to a plurality of transmission reception points TRxPs and receive a measurement report from a user equipment, wherein the plurality of TRxPs generate a unique signal based on the common signal, and wherein the measurement report indicates a signal strength of the unique signal received by the user equipment from the plurality of TRxPs; and a processor configured to select a subset of the plurality of TRxPs based on the measurement report, the subset to be used for selective summation of uplink signals subsequently received from the user equipment; wherein the common signal includes an instruction for generating at least one synchronization signal block SSB and a plurality of second SSBs at an aggregation unit to uniquely indicate each of the plurality of TRxPs; wherein the first SSB is transmitted to the plurality of TRxPs, and different combinations of the plurality of second SSBs are transmitted to encode the identities of the plurality of TRxPs.

11. The baseband unit according to claim 10, wherein the processor is configured to select the subset of the plurality of TRxPs by comparing the signal strength in the measurement report with a threshold signal strength.

12. The baseband unit according to claim 11, wherein the processor is configured to include a TRxP in the subset in response to a corresponding signal strength exceeding the threshold signal strength.

13. The baseband unit according to claim 11, wherein the processor is configured to generate a summation instruction, and wherein the transceiver is configured to transmit the summation instruction to an aggregation unit, and the aggregation unit uses the summation instruction to configure the aggregation unit to selectively sum uplink signals received from the subset of the set of TRxPs.

14. The baseband unit according to claim 13, wherein the transceiver is configured to receive an aggregated uplink signal, the aggregated uplink signal being equal to the sum of the uplink signals received from the subset of the set of TRxPs.

15. The baseband unit according to claim 10, wherein the common signal includes a first synchronization signal block SSB and a plurality of second SSBs, and the plurality of second SSBs are modified by the aggregation unit to uniquely indicate each of the plurality of TRxPs.

16. A communication method, comprising: transmitting a unique signal to a plurality of transmission reception points TRxPs for the plurality of TRxPs to transmit; Receive uplink signals received from the user equipment by the plurality of TRxPs; Generate a sum of the uplink signals from a subset of the plurality of TRxPs, wherein the subset is determined based on measurements of the unique signals performed by the user equipment; and Transmit the sum of the uplink signals to a baseband unit via a fronthaul link; Wherein the unique signals include a first synchronization signal block SSB and a plurality of second SSBs, the first SSB is transmitted by the plurality of TRxPs, and the plurality of second SSBs are selectively transmitted by different TRxPs among the plurality of TRxPs; Wherein transmitting the unique signals includes: Transmit the first SSB to the plurality of TRxPs; And Transmit different combinations of the plurality of second SSBs to encode the identities of the plurality of TRxPs.

17. The method according to claim 16, wherein transmitting the unique signals includes transmitting the first SSB to the plurality of TRxPs and transmitting different second SSBs among the plurality of second SSBs to each of the plurality of TRxPs.

18. The method according to claim 16, wherein transmitting the unique signals Includes: Transmit the first SSB to the plurality of TRxPs; And Transmit different second SSBs among the plurality of second SSBs to each TRxP in a first subset of the plurality of TRxPs in a first time interval, and transmit the different second SSBs among the plurality of second SSBs to each TRxP in a second subset of the TRxPs in a second time interval.

19. The method according to claim 16, wherein generating the unique signals Includes: Perform a fast Fourier transform FFT on a time-domain signal received from the baseband unit to generate a frequency-domain signal, the frequency-domain signal including subcarriers for the first SSB and the plurality of second SSBs; Remove unwanted subcarriers associated with the second SSBs from the frequency-domain signal; Perform an inverse FFT (IFFT) on the frequency-domain signal to form a modified time-domain signal; And Add a cyclic prefix to the modified time-domain signal.

20. The method according to claim 16, wherein generating the unique signals Includes: Remove unwanted subcarriers associated with second SSBs from a frequency-domain signal received from the baseband unit; Perform an inverse FFT (IFFT) on the frequency-domain signal to form a modified time-domain signal; And Add a cyclic prefix to the modified time-domain signal.

21. The method according to claim 16, further Includes: Generate a mask indicating the subset of the plurality of TRxPs.

22. The method according to claim 21, further Includes: Filter the uplink signals received from the plurality of TRxPs using the mask; And Generate the sum by summing the filtered uplink signals.

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