Patent Publication Number: US-2022224400-A1

Title: Repeater system for use with 5g new radio base station

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 63/137,044, filed Jan. 13, 2021, and titled “REPEATER SYSTEM FOR USE WITH 5G NEW RADIO BASE STATION,” and U.S. Provisional Application Ser. No. 63/137,641, filed Jan. 14, 2021, and titled “REPEATER SYSTEM FOR USE WITH 5G NEW RADIO BASE STATION,” which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     A repeater system (such as a distributed antenna system (DAS) or a single-node repeater) is typically used to improve the wireless radio frequency (RF) coverage provided by one or more base stations. A repeater system does this by receiving, amplifying, and re-transmitting one or more RF carriers output by one or more base stations for transmission to user equipment (in the downlink direction) and output by user equipment for transmission to one or more base stations (in the uplink direction). 
     Repeater systems are typically designed to work at the RF layer. Although some repeater systems digitally process the repeated RF signals, such digital processing typically does not implement any of the processing necessary to implement the physical or higher layers of the relevant wireless air interface. 
     Repeater systems can be used, for example, in sport stadiums, buildings (hotels, malls, or trade centers), metro stations and airports, trains, and tunnels. Each base station can be coupled to the repeater system via one or more cables or via a wireless connection, for example, using one or more donor antennas. Repeater systems can be used in other applications. 
     Existing repeater systems have been designed for use with existing wireless air interface standards (such as GSM, UMTS, and LTE) and may not be suitable for use with newer wireless air interface standards, such as the Fifth Generation (5G) New Radio (5G NR) standards. 
     SUMMARY 
     One embodiment is directed to a repeater system for use with a Fifth Generation (5G) New Radio (NR) base station that implements a 5G NR wireless interface and serves a 5G NR cell. The repeater system includes at least one antenna connector to couple at least one external antenna to the repeater system. The repeater system further includes repeater circuitry communicatively coupled to the at least one antenna connector. The repeater circuitry is configured to receive a downlink signal output by the 5G NR base station for wireless transmission to 5G NR user equipment, generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system. The repeater circuitry is also configured to receive an uplink signal wirelessly transmitted by the 5G NR user equipment, generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station. The repeater system is configured to implement: a predetermined output power specification; a predetermined frequency stability specification; a predetermined out-of-band gain specification; a predetermined unwanted emissions specification; a predetermined Error Vector Magnitude specification; a predetermined input intermodulation specification; a predetermined output intermodulation specification; and a predetermined Adjacent Channel Rejection Ratio specification. In some examples, the repeater system is further configured to implement a predetermined Adjacent Channel Leakage Ratio specification and a predetermined noise figure equivalent specification. 
     Another embodiment is directed to a repeater system for use with a Fifth Generation (5G) New Radio (NR) base station that implements a 5G NR wireless interface and serves a 5G NR cell. The repeater system includes one or more internal antennas. The repeater system further includes repeater circuitry communicatively coupled to the one or more internal antennas. The repeater circuitry is configured to receive a downlink signal output by the 5G NR base station for wireless transmission to 5G NR user equipment, generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system. The repeater circuitry is also configured to receive an uplink signal wirelessly transmitted by the 5G NR user equipment, generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station. The repeater system is configured to implement: a predetermined over-the-air output power specification; a predetermined over-the-air frequency stability specification; a predetermined over-the-air out-of-band gain specification; a predetermined over-the-air unwanted emissions specification; a predetermined over-the-air Error Vector Magnitude specification; a predetermined over-the-air input intermodulation specification; a predetermined over-the-air output intermodulation specification; and a predetermined over-the-air Adjacent Channel Rejection Ratio specification. In some examples, the repeater system is further configured to implement a predetermined over-the-air Adjacent Channel Leakage Ratio specification and a predetermined over-the-air noise figure equivalent specification. 
     The details of various embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims. 
    
    
     
       DRAWINGS 
         FIG. 1  is a block diagram illustrating an embodiment of a repeater system in which the techniques described here can be used where the repeater system is implemented as a single-node repeater. 
         FIG. 2  is a block diagram illustrating an embodiment of a repeater system in which the techniques described here can be used where the repeater system is implemented as a distributed antenna system (DAS). 
         FIGS. 3-5  are high-level flow diagrams of exemplary embodiments of methods for a 5G NR repeater system to determine the timing of the 5G NR time-division duplexing used by the 5G NR base station to serve the 5G NR cell. 
         FIG. 6  is a block diagram illustrating and embodiment of a repeater system where the repeater system is implemented as a single-node repeater. 
         FIG. 7  is a block diagram illustrating and embodiment of a repeater system where the repeater system is implemented as a distributed antenna system (DAS). 
         FIG. 8  is a block diagram illustrating and embodiment of a repeater system where the repeater system is implemented as a single-node repeater. 
         FIG. 9  is a block diagram illustrating and embodiment of a repeater system where the repeater system is implemented as a distributed antenna system (DAS). 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate embodiments of repeater systems  100  and  200 , respectively, in which the techniques described here can be used.  FIG. 1  illustrates an embodiment where the repeater system comprises a single-node repeater  100 , and  FIG. 2  illustrates an embodiment where the repeater system comprises a distributed antenna system (DAS)  200 . 
     In both embodiments, the repeater system is configured to be used with at least one Fifth Generation (5G) New Radio (NR) base station  102  that implements a 5G NR wireless interface and serves a 5G NR cell using 5G NR time-division duplexing (TDD). Each 5G NR base station  102  can also be referred to as a “Next Generation NodeB”  102 , a “gNodeB”  102 , or just a “gNB”  102 . The 5G NR base station  102  can be communicatively coupled to the repeater system via one or more cables (as shown in  FIG. 2 ) or via a wireless connection, for example, using a donor antenna  104  (shown in  FIG. 1 ). 
     Each repeater system comprises repeater circuitry  106  that is configured so that it can repeat 5G NR downlink and uplink signals using time-division duplexing (TDD). To do this, the repeater circuitry  106  (and the repeater system more generally) is configured to switch between operating in a downlink mode and an uplink mode. 
     When operating in the downlink mode, the repeater circuitry  106  is configured to receive a downlink signal that was output by the 5G NR base station  102  for wireless transmission to 5G NR user equipment (UE)  108 , generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system via one or more coverage antennas  110  associated with the repeater system. 
     When operating in the uplink mode, the repeater circuitry  106  is configured to receive an uplink signal that was wirelessly transmitted by the 5G NR user equipment  108 , generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station  102 . 
     Typically, the downlink signal received from, and the amplified version of the uplink signal communicated to, the 5G NR base station  102  are received and communicated as analog radio frequency signals, though in some embodiments one or more of the downlink and uplink signals are communicated from and to the 5G NR base station  102  in digital form (for example, in a digital form complying with, for example, the Common Public Radio Interface (“CPRI”) protocol, the Enhanced CPRI (“eCPRI”) protocol, the Open Radio Access Network (“O-RAN”) protocol, the Open Radio Equipment Interface (“ORI”) protocol, the Open Base Station Standard Initiative (“OBSAI”) protocol, or other protocol). Also, the amplified version of the downlink signal wirelessly transmitted to, and the uplink signal wirelessly received from, the 5G NR user equipment  108  are wirelessly transmitted and received as analog radio frequency signals. 
     Moreover, the downlink signal includes one or more radio frequency channels used for communicating in the downlink direction with the 5G NR user equipment  108  over the relevant 5G NR wireless air interface. Likewise, the uplink signal includes one or more radio frequency channels used for communicating in the uplink direction with the 5G NR base station  102  over the relevant 5G NR wireless air interfaces. 
     In one implementation, the 5G NR base station  102  is coupled to the repeater system (and the repeater circuitry  106  thereof) using a circulator. The circulator comprises a first (common) port that is coupled to the 5G NR base station  102  (either directly via a cable or wirelessly via a donor antenna  104 ). The circulator also comprises a second (transmit) port that is coupled to a downlink signal path of the repeater system (and the repeater circuitry  106  thereof). The circulator also comprises a third (receive) port that is coupled to an uplink signal path of the repeater system (and the repeater circuitry  106  thereof). The circulator, when configured in this way, separates the downlink signal from the uplink signal. A circulator can also be used to couple the repeater circuitry  106  to the coverage antenna  110 , where a first (transmit) port of the circulator is coupled to a downlink signal path of the repeater circuitry  106 , a second (common) port of the circulator is coupled to the coverage antenna  110 , and a third (receive port) port of the circulator is coupled to an uplink signal path of the repeater circuitry  106 . 
     The repeater circuitry  106  (and the various features thereof) can be implemented in analog circuitry, digital circuitry, or combinations of analog circuitry and digital circuitry. The repeater circuitry  106  can comprise one or more appropriate connectors, attenuators, combiners, splitters, amplifiers, filters, duplexers, analog-to-digital converters, digital-to-analog converters, electrical-to-optical converters, optical-to-electrical converters, mixers, field-programmable gate arrays (FPGAs), microprocessors, transceivers, framers, etc., to implement the various features described here. 
     In general, when 5G NR time-division duplexing is used by the 5G NR base station  102  to serve the 5G NR cell, the repeater system (for example, the single-node repeater  100  of  FIG. 1  or the DAS  200  of  FIG. 2 ) needs to determine the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell). The timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell determines the transition times when the 5G NR base station  102  switches from transmitting in the downlink direction to receiving in the uplink direction and determines the transition times when the 5G NR base station  102  switches from receiving in the uplink direction to transmitting in the downlink direction. This 5G NR TDD timing is then used by the repeater system (and the repeater circuitry  106 ) in determining when the repeater system itself should switch between being operated in the downlink mode and being operated in the uplink mode. 
     Moreover, an offset can be applied to the transition times determined from the TDD timing for the 5G NR cell in order to account for propagation delays through the repeater system and, in some embodiments, to enable the repeater system to confirm the accuracy of a determined transition time. 
     In general, the repeater circuitry  106  can be configured to switch between the downlink mode and the uplink mode by switching the state of any RF switches used in the repeater system (for example, by switching a RF switch between a downlink state in which the downlink signal is received from the 5G NR base station  102  and an uplink state in which the amplified version of the uplink signal is communicated to the 5G NR base station  102  and/or by switching a RF switch between a downlink state in which the amplified version of the downlink signal is wirelessly transmitted to the 5G NR user equipment  108  and an uplink state in which the uplink signal is received from the 5G NR user equipment  108 ), configuring a power amplifier (PA) used to generate the amplified version of the downlink signal (for example, by turning the PA on or off or by ramping the output power up or down), configuring a downlink automatic gain control (AGC) function used to generate the amplified version of the downlink signal (for example, by turning the AGC on or off or by ramping the gain up or down), configuring a low noise amplifier (LNA) used to receive the uplink signal (for example, by unmuting or muting the LNA or by ramping the gain up or down), and/or configuring an uplink AGC function used to generate the amplified version of the uplink signal (for example, by unmuting or muting the AGC or by ramping the gain up or down). 
     In some examples, multiple TDD channels can utilize a common device (for example, common PA) in a common signal path that is switched or reconfigured by the repeater circuitry  106  in order to switch between the downlink mode and the uplink mode. In some such examples, the TDD timing derived (for example, using the techniques discussed herein) from multiple TDD channels utilizing the common device can be used in combination to derive a switching signal for the common device. The particular mechanism for combining the TDD timing derived from multiple TDD channels is application specific and may depend, for example, on the type of common device, the number of TDD channels, etc. 
       FIG. 3  is a high-level flow diagram of one exemplary embodiment of a method  300  for a 5G NR repeater system to determine the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell (and then use the 5G NR TDD timing to determine when the repeater system itself should switch between operating in the downlink mode and the uplink mode). This method  300  is suitable for implementation in a digital repeater system (for example, in a digital single-node repeater or a digital DAS). In a digital repeater system, the repeater circuitry  106  is configured to generate one or more streams of downlink digital baseband data from the downlink signal received from the 5G NR base station  102 . In one implementation, these streams of downlink baseband data comprise digital in-phase and quadrature (IQ) baseband data. The repeater circuitry  106 , in such a digital repeater system, further comprises one or more processing devices (such as a field programmable gate array (FPGA)) that process the downlink digital baseband data in order to implement the features and functions described below. More specifically, the processing device can implement at least a part of the 5G NR cell search procedures and the waveform correlation function described below. 
     With the approach shown in  FIG. 3 , the repeater circuitry  106  is configured to determine basic TDD parameters for the 5G NR cell served by the 5G NR base station  102  (block  302 ). These basic TDD parameters for the 5G NR cell can include a reference subcarrier spacing, a number of downlink slots, a number of downlink symbols, a number of uplink slots, a number of uplink symbols, and/or a periodicity. In some examples, there can be more than one TDD pattern, so these basic TDD parameters could be respectively determined for each TDD pattern. In some examples, the parameters can also include a frequency band of operation, a downlink channel bandwidth, an uplink channel bandwidth, a downlink center frequency, and/or an uplink center frequency. 
     The repeater circuitry  106  can be configured to determine at least some of the basic TDD parameters for the 5G NR cell served by the 5G NR base station  102  by implementing (for example, in an FPGA) at least a part of the 5G NR cell search procedures in order to receive, demodulate, and decode such basic TDD parameters from the downlink signals transmitted from the 5G NR base station  102  (for example, on the Public Broadcast Channel (PBCH), Primary Synchronization Signal (PSS), and Secondary Synchronization Signal (SSS)). 
     The repeater circuitry  106  can also be configured to determine at least some of the basic TDD parameters by receiving at least some of the basic TDD parameters for the 5G NR cell as manually entered parameters (for example, as parameters that are manually entered at a separate management system and communicated to the repeater system and/or as parameters that are manually entered using a management interface implemented by the repeater system itself (using, for example, a web-based or command-line management interface implemented by software executing on the repeater system). 
     The repeater circuitry  106  can be configured to determine the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell based at least in part on correlating a waveform of the downlink signal received by the repeater circuitry  106  with one or more of: a known 5G NR PSS expected to be in the downlink signal as indicated by at least some of the basic TDD parameters for the 5G NR cell and a known 5G NR SSS expected to be in the downlink signal as indicated by at least some of the basic TDD parameters for the 5G NR cell (block  304 ). This can be done during an initial synchronization phase in which the repeater circuitry  106  determines the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell. The repeater circuitry  106  can be configured to switch between operating the repeater circuitry in the downlink mode and operating the repeater circuitry in the uplink mode using the timing of the 5G NR time-division duplexing of the 5G NR cell (block  306 ). After the timing of the 5G NR time-division duplexing of the 5G NR cell has been determined, a normal operating phase can begin in which the determined TDD timing is used to determine when the repeater system itself should switch between being operated in the downlink mode and being operated in the uplink mode. As noted above, an offset can be applied to the transition times determined from the TDD timing for the 5G NR cell in order to account for propagation delays through the repeater system and, in some embodiments, to enable the repeater system to confirm the accuracy of a determined transition time. Also, while in the normal operating phase, the 5G NR TDD timing for the cell can be re-determined and the repeater circuitry  106  can be re-synchronized in the manner described above (by correlating the waveform in the received downlink signal with the known 5G NR PSS and/or SSS expected to be in the downlink signal) in order to ensure proper synchronization with the 5G NR TDD timing used by the 5G NR base station  102  to serve the 5G NR cell. This can be done periodically and/or in response to an error condition. 
     As a part of determining the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell, the repeater circuitry  106  can be configured to determine PSS and SSS parameters for use in determining the known 5G NR PSS and SSS expected to be in the downlink signal so that they can be correlated with the waveform of the downlink signal received by the repeater circuitry  106 . The PSS and SSS parameters can comprise a starting frequency, a cell identifier (ID) for the 5G NR cell, and a burst periodicity. The repeater circuitry  106  can be configured to determine at least some of the PSS and SSS parameters, at least in part, using the 5G NR cell search procedures and/or by receiving at least some of the PSS and SSS parameters as manually entered parameters (for example, as parameters that are manually entered at a separate management system and communicated to the repeater system and/or as parameters that are manually entered using a management interface implemented by the repeater system itself (using, for example, a web-based or command-line management interface implemented by software executing on the repeater system). 
     In some examples, the repeater operates using multiple-input-multiple-output (MIMO) signals. In some such examples, it may be the case that the one or more MIMO signals do not include the information needed to determine the timing of 5G NR time-division duplexing. For example, it may be the case that only two MIMO signals in a 4×4 MIMO set include a Synchronization Signal Block (SSB), which includes the PSS and the SSS, and the other two MIMO signals in a 4×4 MIMO set do not include the SSB. In such examples, the repeater can use the determined 5G NR time-division duplexing timing from one of the MIMO signals that includes the SSB in order to control the switching applied to the MIMO signals that do not include the SSB. 
       FIG. 4  is a high-level flow diagram of another exemplary embodiment of a method  400  for a 5G NR repeater system to determine the timing of the 5G NR time-division duplexing used by the 5G NR base station  102  to serve the 5G NR cell (and then use the TDD timing to determine when the repeater system itself should switch between operating in the downlink mode and the uplink mode). This method  400  is suitable for implementation in any type of repeater system (for example, in an analog or digital single-node repeater or an analog or digital DAS). 
     With the approach to determining the timing of the time-division duplexing used in the cell shown in  FIG. 4 , the repeater circuitry  106  includes a power detector (PD)  112  that is coupled to the downlink signal received from the 5G NR base station  102 . The power level of the downlink signal can be detected by the power detector  112  (block  402 ). The repeater circuitry  106  can be configured to switch between operating in the downlink mode and the uplink mode based on when the power level first passes above or below one or more thresholds (block  404 ). For example, the repeater circuitry  106  can be configured to use the power level of the downlink signal detected by the power detector  112  to determine when to switch from operating in the uplink mode to operating in the downlink mode. This switch can be done when the cell (and the base station  102 ) has transitioned from transmitting in the uplink direction to transmitting in the downlink direction and can be done by detecting when the power level of the downlink signal first crosses above a first threshold (referred to here as the “downlink threshold”). That the cell (and the base station  102 ) has transitioned from transmitting in the uplink direction to transmitting in the downlink direction can be confirmed by waiting to see that the power level of the downlink signal remains above the downlink threshold for a predetermined amount of time. This can be done to ensure the accuracy of such a TDD transition determination by filtering out situations where a transient condition causes the power level of the downlink signal to temporarily spike above the downlink threshold but not remain above the downlink threshold for the entire predetermined amount of time. 
     Likewise, the repeater circuitry  106  can be configured to use the power level of the downlink signal detected by the power detector  112  to determine when to switch from operating in the downlink mode to operating in the uplink mode. This switch can be done when the cell (and the base station  102 ) has transitioned from transmitting in the downlink direction to transmitting in the uplink direction by detecting when the power level of the downlink signal first crosses below a second threshold (referred to here as the “uplink threshold”). That the cell (and the base station  102 ) has transitioned from transmitting in the downlink direction to transmitting in the uplink direction can be confirmed by waiting to see that the power level of the downlink signal remains below the uplink threshold for a predetermined amount of time. This is done to ensure the accuracy of such a TDD transition determination by filtering out situations where a transient condition causes the power level of the downlink signal to temporarily dip below the uplink threshold but not remain below the uplink threshold for the entire predetermined amount of time. 
     In one implementation, the downlink and uplink thresholds are different from each other, with the downlink threshold being greater than the uplink threshold in order to implement a degree of hysteresis. However, it is to be understood that the downlink threshold and uplink threshold can be implemented in other ways (for example, the downlink threshold and uplink threshold can be set to the same value). 
     As noted above, an offset can be applied to the transition times determined from the 5G NR TDD timing for the 5G NR cell in order to account for propagation delays through the repeater system. The offset can also be extended by an additional amount of time (beyond what is needed to account for propagation delays through the repeater system) in order provide additional time for the confirmation steps described above to be performed in order to enable the repeater system to confirm the accuracy of a TDD transition indicated by first crossing of a downlink or uplink threshold. This additional amount of time can be used to perform other confirmation steps. 
     It is also possible that two or more TDD channels will be received from one or more base stations  102  with different delay. In some examples, the repeater can apply a different amount of offset to the signals received for respective TDD channels in order to synchronize the switching pattern of the signals when signals of the TDD channels are transmitted by the repeater. For example, the repeater can add a delay to the signals on a TDD channel that arrive earlier than the signals on other TDD channels that arrive later. 
     In one implementation of this second approach (method  400 ), the process of detecting when the power level of the downlink signal crosses above (and, in some embodiments, remains above) the downlink threshold and detecting when the power level of the downlink signal crosses below (and, in some embodiments, remains below) the uplink threshold is performed on a frame-by-frame, slot-by-slot, or symbol-by-symbol basis during normal operation of the repeater system in order to determine when the repeater system should switch between operating in the downlink mode and operating the uplink mode. However, other implementations can be implemented in other ways. 
     Moreover, this second approach (method  400 ) can be used as a confirmation step with the first approach (method  300 ) described above. That is, during the initial synchronization phase in which the repeater circuitry  106  determines the timing of the 5G NR time-division duplexing of the 5G NR cell by correlating the waveform in the received downlink signal with the known 5G NR PSS and/or SSS expected to be in the downlink signal, additional confirmation of each TDD transition time for the cell can be confirmed using the second approach by detecting when the power level of the downlink signal crosses above (and, in some embodiments, remains above) the downlink threshold and detecting when the power level of the downlink signal crosses below (and, in some embodiments, remains below) the uplink threshold. 
     The two approaches (methods  300  and  400 ) for a 5G NR repeater system to determine the TDD timing used by a 5G NR base station to serve a 5G NR cell described above involve a standalone 5G NR deployment where the 5G NR base station  102  is used for both control-plane and user-plane communications.  FIG. 5  is a high-level flow diagram of another exemplary embodiment of a method  500  for a 5G NR repeater system to determine the TDD timing used by a 5G NR base station  102  to serve a 5G NR cell. This method  500  is suitable for use in non-standalone 5G NR deployments where the 5G NR base station  102  is used for user-plane communications with the 5G NR user equipment  108  but an LTE base station  103  is used for control-plane communications with the 5G NR user equipment  108 . In such non-standalone 5G NR deployments, the LTE control-plane communications are used to establish the TDD timing for both the LTE control-plane communications and the 5G NR user-plane communications. With the approach shown in  FIG. 5 , the repeater circuitry  106  in the 5G NR repeater system is configured to determine the TDD timing from the LTE control-plane communications (block  502 ) and then use the determined TDD timing to switch between being operated in the downlink mode and being operated in the uplink mode for both the LTE control-plane communications and the 5G NR user-plane communications (block  504 ). The repeater circuitry  106  can be configured to determine the TDD timing from the LTE control-plane communications, for example, using conventional LTE TDD timing determination techniques of the type used in conventional LTE repeaters. Also, the repeater circuitry  106  can be configured to determine the TDD timing from the LTE control-plane communications using one or more of the first two approaches described above, modified appropriately to use LTE control-plane communications. 
     In some examples, the repeater circuitry  106  is configured to receive separate LTE and 5G NR channels and the switching for the LTE and 5G NR channels is synchronized. In some such examples, the TDD timing derived from the LTE signals (for example, LTE TDD timing determination techniques of the type used in conventional LTE repeaters) can be applied to the LTE channel(s) and the NR channel(s). In other such examples, the TDD timing derived from the NR signals (for example, using methods  300  and  400  discussed above) can be applied to the LTE channel(s) and the NR channel(s). 
     The techniques described above can be implemented in single-node repeater  100 , a DAS  200 , and combinations thereof (for example, where a single-node repeater  100  is used to couple a DAS  200  to a remotely located base station  102  using a wireless link). 
     In the embodiment shown in  FIG. 1 , the repeater system comprises a single-node repeater  100 . In the single-node repeater  100 , the repeater circuitry  106  and the features described above as being implemented by the repeater circuitry  106  (and the repeater system more generally) are all implemented in the single-node repeater  100 . 
     In general, the single-node repeater  100  is configured to receive a downlink signal from the 5G NR base station  102 . The downlink signal includes one or more radio frequency channels used for communicating in the downlink direction with 5G NR user equipment  108  over the 5G NR wireless air interface. The repeater circuitry is configured to amplify the downlink signals received at the single-node repeater  100  and re-radiate the amplified downlink signals via the coverage antenna  110 . As a part of doing this, the repeater circuitry  106  can be configured to filter the downlink signals to separate out the individual channels, individually amplify each filtered downlink channel signal, combine the individually amplified downlink channel signals, and re-radiate the resulting combined signal. 
     Similar processing is performed in the uplink. The single-node repeater  100  is configured to receive one or more uplink signals from 5G NR user equipment  108 . Each uplink signal includes one or more radio frequency channels used for communicating in the uplink direction with the 5G NR base station  102  over the 5G NR wireless air interfaces. The repeater circuitry  106  can be configured to amplify the uplink signals received at the single-node repeater  100  and re-radiate the amplified uplink signals via the donor antenna  104 . As a part of doing this, the repeater circuitry  106  can be configured to filter the uplink signal to separate out the individual channels, individually amplify each filtered uplink channel signal, combine the individually amplified uplink channel signals, and re-radiate the resulting combined signal. 
     In the embodiment shown in  FIG. 2 , the repeater system comprises a DAS  200 . 
     The DAS  200  includes at least one main unit  202  (for example, a master unit) that is communicatively coupled to a plurality of remote antenna units  204 . Each remote antenna unit  204  can be coupled directly to the main unit  202  or indirectly via one or more other remote antenna units  204  and/or via one or more intermediary or expansion units  206 . 
     In the embodiment shown in  FIG. 2 , the repeater circuitry  106  and the features described above as being implemented by the repeater circuitry  106  (and the repeater system more generally) are distributed across the main unit  202 , the remote antenna units  204 , and/or any intermediary units  206 . 
     In general, each main unit  202  is configured to receive the downlink signal from the 5G NR base station  102  and generate one or more downlink transport signals derived from the received downlink signal. The main unit  202  transmits the one or more downlink transport signals to one or more of the remote antenna units  204 . Each remote antenna unit  204  receives the downlink transport signals transmitted to it and uses the received downlink transport signals to generate an amplified version of the downlink signal. The amplified version of the downlink signal is radiated from one or more coverage antennas  110  associated with that remote antenna unit  204 . The amplified version of the downlink signal is radiated for reception by the 5G NR user equipment  108 . Typically, this downlink processing involves, among other things, simulcasting the downlink signal received from the 5G NR base station  102  from multiple remote antenna units  204 . In this way, the DAS  200  can increase the coverage area for the downlink capacity provided by the 5G NR base station  102 . 
     Likewise, each remote antenna unit  204  receives an uplink signal transmitted from the 5G NR user equipment  108 . Each remote antenna unit  204  generates an uplink transport signal derived from the uplink frequency signal and transmits the uplink transport signal to the main unit  202 . The main unit  202  receives the respective uplink transport signals transmitted to it from one or more remote antenna units  204  and uses the received uplink transport signals to generate an amplified version of the uplink signals received at the various remote antenna units  204 . The amplified version of the uplink signals received at the various remote antenna units  204  is provided to the 5G NR base station  102 . Typically, this uplink processing involves, among other things, combining or summing uplink signals received from multiple remote antenna units  204  in order to produce the amplified version of the uplink signals received at the various remote antenna units  204  that is provided to the 5G NR base station  102 . In this way, the DAS  200  can increase the coverage area for the uplink capacity associated with the 5G NR base station  102 . 
     The DAS  200  can use either digital transport, analog transport, or combinations of digital and analog transport for generating and communicating the transport signals between the main units  202  and the remote antenna units  204  (and any intermediary units  206 ). 
       FIGS. 6 and 7  illustrate embodiments of repeater systems  600  and  700 , respectively, in which the techniques described here can be used.  FIG. 6  illustrates an embodiment where the repeater system comprises a single-node repeater  600 , and  FIG. 7  illustrates an embodiment where the repeater system comprises a distributed antenna system (DAS)  700 . 
     In both embodiments, the repeater system is configured to be used with at least one Fifth Generation (5G) New Radio (NR) base station  602  that implements a 5G NR wireless interface and serves a 5G NR cell. In some examples, the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR time-division duplexing (TDD). In some examples, the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR frequency-division duplexing (FDD). Each 5G NR base station  602  can also be referred to as a “Next Generation NodeB”  602 , a “gNodeB”  602 , or just a “gNB”  602 . The 5G NR base station  602  can be communicatively coupled to the repeater system via one or more cables or via a wireless connection, for example, using one or more donor antennas  604  (shown in  FIG. 6 ). In the example shown in  FIG. 6 , the single-node repeater  600  includes one or more antenna connectors  605  that are configured to be coupled to the one or more external donor antennas  604 . 
     Each repeater system comprises repeater circuitry  606  that is configured so that it can repeat 5G NR downlink and uplink signals. In the examples where the 5G NR wireless interface is implemented using 5G NR TDD, the repeater circuitry  606  (and the repeater system more generally) is configured to switch between operating in a downlink mode and an uplink mode. 
     The repeater circuitry  606  is configured to receive a downlink signal that was output by the 5G NR base station  602  for wireless transmission to 5G NR user equipment (UE)  608 , generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system via one or more coverage antennas  610  associated with the repeater system. In the example shown in  FIG. 6 , the single-node repeater  600  includes one or more antenna connectors  611  that are configured to be coupled to the one or more external coverage antennas  610 . 
     The repeater circuitry  606  is configured to receive an uplink signal that was wirelessly transmitted by the 5G NR user equipment  608 , generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station  602 . 
     Typically, the downlink signal received from, and the amplified version of the uplink signal communicated to, the 5G NR base station  602  are received and communicated as analog radio frequency signals, though in some embodiments one or more of the downlink and uplink signals are communicated from and to the 5G NR base station  602  in digital form (for example, in a digital form complying with, for example, the Common Public Radio Interface (“CPRI”) protocol, the Enhanced CPRI (“eCPRI”) protocol, the Open Radio Access Network (“O-RAN”) protocol, the Open Radio Equipment Interface (“ORI”) protocol, the Open Base Station Standard Initiative (“OBSAI”) protocol, or other protocol). Also, the amplified version of the downlink signal wirelessly transmitted to, and the uplink signal wirelessly received from, the 5G NR user equipment  608  are wirelessly transmitted and received as analog radio frequency signals. 
     Moreover, the downlink signal includes one or more radio frequency channels used for communicating in the downlink direction with the 5G NR user equipment  608  over the relevant 5G NR wireless air interface. Likewise, the uplink signal includes one or more radio frequency channels used for communicating in the uplink direction with the 5G NR base station  602  over the relevant 5G NR wireless air interfaces. 
     In one implementation, the 5G NR base station  602  is coupled to the repeater system (and the repeater circuitry  606  thereof) using a circulator. The circulator comprises a first (common) port that is coupled to the 5G NR base station  602  (either directly via a cable or wirelessly via an antenna connector  605  and donor antenna  604 ). The circulator also comprises a second (transmit) port that is coupled to a downlink signal path of the repeater system (and the repeater circuitry  606  thereof). The circulator also comprises a third (receive) port that is coupled to an uplink signal path of the repeater system (and the repeater circuitry  606  thereof). The circulator, when configured in this way, separates the downlink signal from the uplink signal. A circulator can also be used to couple the repeater circuitry  606  to the antenna connector  611  and coverage antenna  610 , where a first (transmit) port of the circulator is coupled to a downlink signal path of the repeater circuitry  606 , a second (common) port of the circulator is coupled to the antenna connector  611  and the coverage antenna  610 , and a third (receive port) port of the circulator is coupled to an uplink signal path of the repeater circuitry  606 . 
     The repeater circuitry  606  (and the various features thereof) can be implemented in analog circuitry, digital circuitry, or combinations of analog circuitry and digital circuitry. The repeater circuitry  606  can comprise one or more appropriate connectors, attenuators, combiners, splitters, amplifiers, filters, duplexers, analog-to-digital converters, digital-to-analog converters, electrical-to-optical converters, optical-to-electrical converters, mixers, field-programmable gate arrays (FPGAs), microprocessors, transceivers, framers, etc., to implement the various features described here. 
     In the example shown in  FIG. 6 , the repeater system is configured to implement a plurality of specifications. In some examples, the repeater system is configured to implement a predetermined output power specification, a predetermined frequency stability specification, a predetermined out-of-band gain specification, a predetermined unwanted emissions specification, a predetermined Error Vector Magnitude specification, a predetermined input intermodulation specification, a predetermined output intermodulation specification, and a predetermined Adjacent Channel Rejection Ratio specification. In some examples, the repeater system is also configured to implement a predetermined Adjacent Channel Leakage Ratio specification and a predetermined noise figure equivalent specification. In some such examples, at least one of the specifications includes a predetermined value, a predetermined range of predetermined values, or a predetermined threshold. In some examples, at least one of the specifications is specified in a 3GPP specification. In some examples, at least one of the specifications is related to a corresponding specification for the base station as specified in 3GPP TS38.104 and tested for 3GPP TS38.141-1. 
     In some examples, the repeater system is configured to implement a predetermined transmitter ON/OFF power specification. In some such examples, the transmitter OFF power is −85 dBm/1 MHz. In some examples, the predetermined transmitter ON/OFF power specification is specified in a 3GPP specification. 
     In some examples, the repeater system is configured to implement a predetermined transmitter transient period specification. In some such examples, the transmitter transient period is less than 10 microseconds. In some examples, the predetermined transmitter transient period specification is specified in a 3GPP specification. 
     In some examples, the repeater system is configured to operate in the FR1 frequency range. In some examples, the repeater system is configured to operate in the FR2 frequency range. In some examples, the repeater system is configured to operate in both the FR1 and FR2 frequency ranges. 
     In the embodiment shown in  FIG. 7 , the repeater system comprises a DAS  700 . 
     The DAS  700  includes at least one main unit  702  (for example, a master unit) that is communicatively coupled to a plurality of remote antenna units  704 . Each remote antenna unit  704  can be coupled directly to the main unit  702  or indirectly via one or more other remote antenna units  704  and/or via one or more intermediary or expansion units  706 . 
     In the embodiment shown in  FIG. 7 , the repeater circuitry  606  and the features described above as being implemented by the repeater circuitry  606  (and the repeater system more generally) are distributed across the main unit  702 , the remote antenna units  704 , and/or any intermediary units  706 . 
     In general, each main unit  702  is configured to receive the downlink signal from the 5G NR base station  602  and generate one or more downlink transport signals derived from the received downlink signal. The main unit  702  transmits the one or more downlink transport signals to one or more of the remote antenna units  704 . Each remote antenna unit  704  receives the downlink transport signals transmitted to it and uses the received downlink transport signals to generate an amplified version of the downlink signal. The amplified version of the downlink signal is radiated from one or more coverage antennas  610  associated with that remote antenna unit  704 . In the example shown in  FIG. 7 , the remote antenna unit  704  includes an antenna connector  711  configured to be coupled to the one or more external coverage antennas  610 . The amplified version of the downlink signal is radiated for reception by the 5G NR user equipment  608 . Typically, this downlink processing involves, among other things, simulcasting the downlink signal received from the 5G NR base station  602  from multiple remote antenna units  704 . In this way, the DAS  700  can increase the coverage area for the downlink capacity provided by the 5G NR base station  602 . 
     Likewise, each remote antenna unit  704  receives an uplink signal transmitted from the 5G NR user equipment  608 . Each remote antenna unit  704  generates an uplink transport signal derived from the uplink frequency signal and transmits the uplink transport signal to the main unit  702 . The main unit  702  receives the respective uplink transport signals transmitted to it from one or more remote antenna units  704  and uses the received uplink transport signals to generate an amplified version of the uplink signals received at the various remote antenna units  704 . The amplified version of the uplink signals received at the various remote antenna units  704  is provided to the 5G NR base station  602 . Typically, this uplink processing involves, among other things, combining or summing uplink signals received from multiple remote antenna units  704  in order to produce the amplified version of the uplink signals received at the various remote antenna units  704  that is provided to the 5G NR base station  602 . In this way, the DAS  700  can increase the coverage area for the uplink capacity associated with the 5G NR base station  602 . 
     The DAS  700  can use either digital transport, analog transport, or combinations of digital and analog transport for generating and communicating the transport signals between the main units  702  and the remote antenna units  704  (and any intermediary units  706 ). 
       FIGS. 8 and 9  illustrate embodiments of repeater systems  800  and  900 , respectively, in which the techniques described here can be used.  FIG. 8  illustrates an embodiment where the repeater system comprises a single-node repeater  800 , and  FIG. 9  illustrates an embodiment where the repeater system comprises a distributed antenna system (DAS)  900 . 
     In both embodiments, the repeater system is configured to be used with at least one Fifth Generation (5G) New Radio (NR) base station  802  that implements a 5G NR wireless interface and serves a 5G NR cell. In some examples, the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR time-division duplexing (TDD). In some examples, the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR frequency-division duplexing (FDD). Each 5G NR base station  802  can also be referred to as a “Next Generation NodeB”  802 , a “gNodeB”  802 , or just a “gNB”  802 . The 5G NR base station  802  can be communicatively coupled to the repeater system via one or more cables or via a wireless connection, for example, using one or more internal antennas  810  (shown in  FIG. 8 ). In some examples, at least one of the one or more internal antennas  810  is configured to operate as a donor antenna. 
     Each repeater system comprises repeater circuitry  806  that is configured so that it can repeat 5G NR downlink and uplink signals. In the examples where the 5G NR wireless interface is implemented using 5G NR TDD, the repeater circuitry  806  (and the repeater system more generally) is configured to switch between operating in a downlink mode and an uplink mode. 
     The repeater circuitry  806  is configured to receive a downlink signal that was output by the 5G NR base station  802  for wireless transmission to 5G NR user equipment (UE)  808 , generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system via one or more internal antennas  810  associated with the repeater system. In the example shown in  FIG. 8 , at least one of the one or more internal antennas  810  is configured to operate as a coverage antenna. 
     The repeater circuitry  806  is configured to receive an uplink signal that was wirelessly transmitted by the 5G NR user equipment  808 , generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station  802 . 
     Typically, the downlink signal received from, and the amplified version of the uplink signal communicated to, the 5G NR base station  802  are received and communicated as analog radio frequency signals, though in some embodiments one or more of the downlink and uplink signals are communicated from and to the 5G NR base station  802  in digital form (for example, in a digital form complying with, for example, the Common Public Radio Interface (“CPRI”) protocol, the Enhanced CPRI (“eCPRI”) protocol, the Open Radio Access Network (“O-RAN”) protocol, the Open Radio Equipment Interface (“ORI”) protocol, the Open Base Station Standard Initiative (“OBSAI”) protocol, or other protocol). Also, the amplified version of the downlink signal wirelessly transmitted to, and the uplink signal wirelessly received from, the 5G NR user equipment  808  are wirelessly transmitted and received as analog radio frequency signals. 
     Moreover, the downlink signal includes one or more radio frequency channels used for communicating in the downlink direction with the 5G NR user equipment  808  over the relevant 5G NR wireless air interface. Likewise, the uplink signal includes one or more radio frequency channels used for communicating in the uplink direction with the 5G NR base station  802  over the relevant 5G NR wireless air interfaces. 
     In one implementation, the 5G NR base station  802  is coupled to the repeater system (and the repeater circuitry  806  thereof) using a circulator. The circulator comprises a first (common) port that is coupled to the 5G NR base station  802  (either directly via a cable or wirelessly via an internal antenna  810 ). The circulator also comprises a second (transmit) port that is coupled to a downlink signal path of the repeater system (and the repeater circuitry  806  thereof). The circulator also comprises a third (receive) port that is coupled to an uplink signal path of the repeater system (and the repeater circuitry  806  thereof). The circulator, when configured in this way, separates the downlink signal from the uplink signal. A circulator can also be used to couple the repeater circuitry  806  to an internal antenna  810 , where a first (transmit) port of the circulator is coupled to a downlink signal path of the repeater circuitry  806 , a second (common) port of the circulator is coupled to an internal antenna  810 , and a third (receive port) port of the circulator is coupled to an uplink signal path of the repeater circuitry  806 . 
     The repeater circuitry  806  (and the various features thereof) can be implemented in analog circuitry, digital circuitry, or combinations of analog circuitry and digital circuitry. The repeater circuitry  806  can comprise one or more appropriate connectors, attenuators, combiners, splitters, amplifiers, filters, duplexers, analog-to-digital converters, digital-to-analog converters, electrical-to-optical converters, optical-to-electrical converters, mixers, field-programmable gate arrays (FPGAs), microprocessors, transceivers, framers, etc., to implement the various features described here. 
     In the example shown in  FIG. 8 , the repeater system is configured to implement a plurality of specifications. In some examples, the repeater system is configured to implement a predetermined over-the-air output power specification, a predetermined over-the-air frequency stability specification, a predetermined over-the-air out-of-band gain specification, a predetermined over-the-air unwanted emissions specification, a predetermined over-the-air Error Vector Magnitude specification, a predetermined over-the-air input intermodulation specification, a predetermined over-the-air output intermodulation specification, and a predetermined over-the-air Adjacent Channel Rejection Ratio specification. In some examples, the repeater system is also configured to implement a predetermined over-the-air Adjacent Channel Leakage Ratio specification and a predetermined over-the-air noise figure equivalent specification. In some such examples, at least one of the specifications includes a predetermined value, a predetermined range of predetermined values, or a predetermined threshold. In some examples, at least one of the specifications is specified in a 3GPP specification. In some examples, at least one of the specifications is related to a corresponding specification for the base station as specified in 3GPP TS38.104 and tested for 3GPP TS38.141-2. 
     In some examples, the repeater system is configured to implement a predetermined transmitter ON/OFF power specification. In some such examples, the transmitter OFF power is −85 dBm/1 MHz. In some examples, the predetermined transmitter ON/OFF power specification is specified in a 3GPP specification. 
     In some examples, the repeater system is configured to implement a predetermined transmitter transient period specification. In some such examples, the transmitter transient period is less than 10 microseconds. In some examples, the predetermined transmitter transient period specification is specified in a 3GPP specification. 
     In some examples, the repeater system is configured to operate in the FR1 frequency range. 
     In the embodiment shown in  FIG. 9 , the repeater system comprises a DAS  900 . 
     The DAS  900  includes at least one main unit  902  (for example, a master unit) that is communicatively coupled to a plurality of remote antenna units  904 . Each remote antenna unit  904  can be coupled directly to the main unit  902  or indirectly via one or more other remote antenna units  904  and/or via one or more intermediary or expansion units  906 . 
     In the embodiment shown in  FIG. 9 , the repeater circuitry  806  and the features described above as being implemented by the repeater circuitry  806  (and the repeater system more generally) are distributed across the main unit  902 , the remote antenna units  904 , and/or any intermediary units  906 . 
     In general, each main unit  902  is configured to receive the downlink signal from the 5G NR base station  802  via one or more internal antennas  804  and generate one or more downlink transport signals derived from the received downlink signal. The main unit  902  transmits the one or more downlink transport signals to one or more of the remote antenna units  904 . Each remote antenna unit  904  receives the downlink transport signals transmitted to it and uses the received downlink transport signals to generate an amplified version of the downlink signal. The amplified version of the downlink signal is radiated from one or more internal antennas  810  included in that remote antenna unit  904 . The amplified version of the downlink signal is radiated for reception by the 5G NR user equipment  808 . Typically, this downlink processing involves, among other things, simulcasting the downlink signal received from the 5G NR base station  802  from multiple remote antenna units  904 . In this way, the DAS  900  can increase the coverage area for the downlink capacity provided by the 5G NR base station  802 . 
     Likewise, each remote antenna unit  904  receives an uplink signal transmitted from the 5G NR user equipment  808 . Each remote antenna unit  904  generates an uplink transport signal derived from the uplink frequency signal and transmits the uplink transport signal to the main unit  902 . The main unit  902  receives the respective uplink transport signals transmitted to it from one or more remote antenna units  904  and uses the received uplink transport signals to generate an amplified version of the uplink signals received at the various remote antenna units  904 . The amplified version of the uplink signals received at the various remote antenna units  904  is provided to the 5G NR base station  802  via the one or more internal antennas  804 . Typically, this uplink processing involves, among other things, combining or summing uplink signals received from multiple remote antenna units  904  in order to produce the amplified version of the uplink signals received at the various remote antenna units  904  that is provided to the 5G NR base station  802 . In this way, the DAS  900  can increase the coverage area for the uplink capacity associated with the 5G NR base station  802 . 
     The DAS  900  can use either digital transport, analog transport, or combinations of digital and analog transport for generating and communicating the transport signals between the main units  902  and the remote antenna units  904  (and any intermediary units  906 ). 
     While the examples described herein refer particularly to 5G NR base stations and 5G NR user equipment, it should be understood that the repeater systems described herein could also be used for 5G evolution, 6G, and further generations of standards for mobile broadband that include similar requirements as for 5G NR. 
     The methods and techniques described here may be implemented in digital electronic circuitry, or with a programmable processor (for example, a special-purpose processor or a general-purpose processor such as a computer) firmware, software, or in combinations of them. Apparatus embodying these techniques may include appropriate input and output devices, a programmable processor, and a storage medium tangibly embodying program instructions for execution by the programmable processor. A process embodying these techniques may be performed by a programmable processor executing a program of instructions to perform desired functions by operating on input data and generating appropriate output. The techniques may advantageously be implemented in one or more programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Generally, a processor will receive instructions and data from a read-only memory and/or a random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and DVD disks. Any of the foregoing may be supplemented by, or incorporated in, specially-designed application-specific integrated circuits (ASICs). 
     EXAMPLE EMBODIMENTS 
     Example 1 includes a repeater system for use with a Fifth Generation (5G) New Radio (NR) base station that implements a 5G NR wireless interface and serves a 5G NR cell, the repeater system comprising: at least one antenna connector to couple at least one external antenna to the repeater system; repeater circuitry communicatively coupled to the at least one antenna connector, wherein the repeater circuitry is configured to: receive a downlink signal output by the 5G NR base station for wireless transmission to 5G NR user equipment, generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system; and receive an uplink signal wirelessly transmitted by the 5G NR user equipment, generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station; wherein the repeater system is configured to implement: a predetermined output power specification; a predetermined frequency stability specification; a predetermined out-of-band gain specification; a predetermined unwanted emissions specification; a predetermined Error Vector Magnitude specification; a predetermined input intermodulation specification; a predetermined output intermodulation specification; and a predetermined Adjacent Channel Rejection Ratio specification. 
     Example 2 includes the repeater system of Example 1, wherein at least one of the predetermined output power specification, the predetermined frequency stability specification, the predetermined out-of-band gain specification, the predetermined unwanted emissions specification, the predetermined Error Vector Magnitude specification, the predetermined input intermodulation specification, the predetermined output intermodulation specification, and the predetermined Adjacent Channel Rejection Ratio specification comprises a predetermined value, a predetermined range of predetermined values, or a predetermined threshold. 
     Example 3 includes the repeater system of any of Examples 1-2, wherein at least one of the predetermined output power specification, the predetermined frequency stability specification, the predetermined out-of-band gain specification, the predetermined unwanted emissions specification, the predetermined Error Vector Magnitude specification, the predetermined input intermodulation specification, the predetermined output intermodulation specification, and the predetermined Adjacent Channel Rejection Ratio specification is specified in a 3GPP specification. 
     Example 4 includes the repeater system of any of Examples 1-3, wherein the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR time-division duplexing (TDD). 
     Example 5 includes the repeater system of any of Examples 1-4, wherein the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR frequency-division duplexing (FDD). 
     Example 6 includes the repeater system of any of Examples 1-5, wherein the repeater system is configured to operate in a FR1 frequency range. 
     Example 7 includes the repeater system of any of Examples 1-6, wherein the repeater system is configured to implement a predetermined transmitter ON/OFF power specification. 
     Example 8 includes the repeater system of Example 7, wherein a transmitter OFF power is −85 dBm/1 MHz. 
     Example 9 includes the repeater system of any of Examples 1-8, wherein the repeater system is configured to implement a predetermined transmitter transient period specification. 
     Example 10 includes the repeater system of Example 9, wherein the predetermined transmitter transient period is less than 10 microseconds. 
     Example 11 includes the repeater system of any of Examples 1-10, wherein at least one of the predetermined output power specification, the predetermined frequency stability specification, the predetermined out-of-band gain specification, the predetermined unwanted emissions specification, the predetermined Error Vector Magnitude specification, the predetermined input intermodulation specification, the predetermined output intermodulation specification, and the predetermined Adjacent Channel Rejection Ratio specification is related to a corresponding specification for the 5G NR base station as specified in 3GPP TS38.104 and tested for 3GPP TS38.141-1. 
     Example 12 includes the repeater system of any of Examples 1-11, wherein the repeater system comprises a distributed antenna system (DAS), wherein the repeater circuitry is distributed across a main unit and a plurality of remote antenna units. 
     Example 13 includes the repeater system of any of Examples 1-12, wherein the repeater system comprises at least one of a digital DAS, an analog DAS, and a hybrid digital-analog DAS. 
     Example 14 includes the repeater system of any of Examples 1-13, wherein the repeater system comprises a single-node repeater. 
     Example 15 includes the repeater system of any of Examples, 1-14, wherein the repeater system is further configured to implement a predetermined Adjacent Channel Leakage Ratio specification and a predetermined noise figure equivalent specification. 
     Example 16 includes a repeater system for use with a Fifth Generation (5G) New Radio (NR) base station that implements a 5G NR wireless interface and serves a 5G NR cell, the repeater system comprising: one or more internal antennas; and repeater circuitry communicatively coupled to the one or more internal antennas, wherein the repeater circuitry is configured to: receive a downlink signal output by the 5G NR base station for wireless transmission to 5G NR user equipment, generate an amplified version of the downlink signal, and wirelessly transmit the amplified version of the downlink signal into a coverage area associated with the repeater system; and receive an uplink signal wirelessly transmitted by the 5G NR user equipment, generate an amplified version of the uplink signal, and communicate the amplified version of the uplink signal to the 5G NR base station; wherein the repeater system is configured to implement: a predetermined over-the-air output power specification; a predetermined over-the-air frequency stability specification; a predetermined over-the-air out-of-band gain specification; a predetermined over-the-air unwanted emissions specification; a predetermined over-the-air Error Vector Magnitude specification; a predetermined over-the-air input intermodulation specification; a predetermined over-the-air output intermodulation specification; and a predetermined over-the-air Adjacent Channel Rejection Ratio specification. 
     Example 17 includes the repeater system of Example 16, wherein at least one of the predetermined over-the-air output power specification, the predetermined over-the-air frequency stability specification, the predetermined over-the-air out-of-band gain specification, the predetermined over-the-air unwanted emissions specification, the predetermined over-the-air Error Vector Magnitude specification, the predetermined over-the-air input intermodulation specification, the predetermined over-the-air output intermodulation specification, and the predetermined over-the-air Adjacent Channel Rejection Ratio specification comprises a predetermined value, a predetermined range of predetermined values, or a predetermined threshold. 
     Example 18 includes the repeater system of Example 17, wherein at least one of the predetermined over-the-air output power specification, the predetermined over-the-air frequency stability specification, the predetermined over-the-air out-of-band gain specification, the predetermined over-the-air unwanted emissions specification, the predetermined over-the-air Error Vector Magnitude specification, the predetermined over-the-air input intermodulation specification, the predetermined over-the-air output intermodulation specification, and the predetermined over-the-air Adjacent Channel Rejection Ratio specification is specified in a 3GPP specification. 
     Example 19 includes the repeater system of any of Examples 16-18, wherein the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR time-division duplexing (TDD). 
     Example 20 includes the repeater system of any of Examples 16-19, wherein the 5G NR wireless interface is implemented and the 5G NR cell is served using 5G NR frequency-division duplexing (FDD). 
     Example 21 includes the repeater system of any of Examples 16-20, wherein the repeater system is configured to operate in a FR1 frequency range. 
     Example 22 includes the repeater system of any of Examples 16-20, wherein the repeater system is configured to operate in a FR2 frequency range. 
     Example 23 includes the repeater system of any of Examples 16-20, wherein the repeater system is configured to operate in a FR1 frequency range and a FR2 frequency range. 
     Example 24 includes the repeater system of any of Examples 16-23, wherein the repeater system is configured to implement a predetermined transmitter ON/OFF power specification. 
     Example 25 includes the repeater system of Example 24, wherein a transmitter OFF power is −85 dBm/1 MHz. 
     Example 26 includes the repeater system of any of Examples 16-25, wherein the repeater system is configured to implement a predetermined transmitter transient period specification. 
     Example 27 includes the repeater system of Example 26, wherein the predetermined transmitter transient period is less than 10 microseconds. 
     Example 28 includes the repeater system of any of Examples 16-27, wherein at least one of the predetermined over-the-air output power specification, the predetermined over-the-air frequency stability specification, the predetermined over-the-air out-of-band gain specification, the predetermined over-the-air unwanted emissions specification, the predetermined over-the-air Error Vector Magnitude specification, the predetermined over-the-air input intermodulation specification, the predetermined over-the-air output intermodulation specification, and the predetermined over-the-air Adjacent Channel Rejection Ratio specification is related to a corresponding specification for the base station as specified in 3GPP TS38.104 and tested for 3GPP TS38.141-2. 
     Example 29 includes the repeater system of any of Examples 16-28, wherein the repeater system comprises a distributed antenna system (DAS), wherein the repeater circuitry is distributed across a main unit and a plurality of remote antenna units. 
     Example 30 includes the repeater system of any of Examples 16-29, wherein the repeater system comprises at least one of a digital DAS, an analog DAS, and a hybrid digital-analog DAS. 
     Example 31 includes the repeater system of any of Examples 16-30, wherein the repeater system comprises a single-node repeater. 
     Example 32 includes the repeater system of any of Examples 16-31, wherein the repeater system is further configured to implement a predetermined over-the-air Adjacent Channel Leakage Ratio specification and a predetermined over-the-air noise figure equivalent specification. 
     A number of embodiments of the invention defined by the following claims have been described. Nevertheless, it will be understood that various modifications to the described embodiments may be made without departing from the spirit and scope of the claimed invention. Accordingly, other embodiments are within the scope of the following claims.