EP1391060A2 - Commande de gain intelligente dans un repeteur sur la meme frequence - Google Patents

Commande de gain intelligente dans un repeteur sur la meme frequence

Info

Publication number
EP1391060A2
EP1391060A2 EP02732268A EP02732268A EP1391060A2 EP 1391060 A2 EP1391060 A2 EP 1391060A2 EP 02732268 A EP02732268 A EP 02732268A EP 02732268 A EP02732268 A EP 02732268A EP 1391060 A2 EP1391060 A2 EP 1391060A2
Authority
EP
European Patent Office
Prior art keywords
gain
signal
signals
power level
controller
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02732268A
Other languages
German (de)
English (en)
Inventor
David Bongfeldt
Paul Simpson
Mike Roper
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Spotwave Wireless Inc
Original Assignee
Spotwave Wireless Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/865,466 external-priority patent/US6889033B2/en
Application filed by Spotwave Wireless Inc filed Critical Spotwave Wireless Inc
Publication of EP1391060A2 publication Critical patent/EP1391060A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/52—TPC using AGC [Automatic Gain Control] circuits or amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
    • H04B7/15535—Control of relay amplifier gain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15564—Relay station antennae loop interference reduction
    • H04B7/15578—Relay station antennae loop interference reduction by gain adjustment

Definitions

  • the present application relates to wireless access networks and, in particular, to a method and system for enabling Intelligent Gain Control (IGC) in an on-frequency repeater.
  • IGBC Intelligent Gain Control
  • wireless access networks are increasingly popular, as they enable subscribers to access communications services without being tied to a fixed, wireline communications device.
  • Conventional wireless access network infrastructure e.g., base stations
  • MSAs Metropolitan Service Areas
  • Cells overlapping coverage areas or “cells”.
  • MSAs Metropolitan Service Areas
  • the build-out, and corresponding wireless communications services subsequently migrates outward from the MSAs to areas of lower population/service densities (e.g., urban to suburban to rural, etc.).
  • the build-out slows and/or becomes spotty leaving many individual wireless subscribers with unreliable or non-existent service.
  • On-frequency repeaters are known in the art for improving wireless services within defined regions of a wireless network (e.g., within a building or a built-up area). Such on-frequency repeaters are typically provided by the wireless network provider in order to improve signal quality in high noise or attenuation environments, where signal levels would otherwise be too low for satisfactory quality of service. In some cases, a wireless network provider may install a repeater in order to improve service in an area lying at an edge of the coverage area serviced by a base station, thereby effectively extending the reach of the base-station.
  • Prior art repeaters are part of a network-centric view of the wireless network space, in that they are comparatively large systems provided by the network provider in order to improve wireless service to multiple subscribers within a defined area. As such, they form part of the network "build-out plan" of the network provider. These systems suffer the disadvantage in that an individual subscriber cannot benefit from the improved services afforded by the repeater unless they happen to be located within the coverage area of the repeater.
  • wireless subscribers may reside or work in areas where the coverage area of the wireless network is unreliable. Typical examples include mobile subscribers, and subscribers located in suburban and rural areas.
  • in-building coverage can be unreliable even within MSAs, depending on the size, location and construction of buildings and/or other obstacles. In such cases, it may be uneconomical for a network provider to build-out the network to provide adequate coverage area, thereby leaving those subscribers with inadequate wireless services.
  • Adaptive Personal Repeater transparently mediates signaling between a subscriber's wireless communications device (WCD) and a transceiver (base station) of a wireless communications network.
  • WCD wireless communications device
  • base station transceiver
  • the repeater includes a Directional Donor Unit (DDU) and a Subscriber Coverage Unit (SCU).
  • DDU maintains a network link with the base station of the wireless communications network.
  • the SCU maintains a local link with the WCD within a personal wireless space of the APR.
  • Total system gain is divided between and integrated with the DDU and the SCU, so that a separate gain and system control unit is not required. This division of system gain also enables high-performance on-frequency repeater functionality to be obtained without the use of high-cost components and building blocks.
  • the APR represents a subscriber-centric solution for improving wireless services as required by one or more subscribers, and in a manner that is transparent to the network.
  • the repeater in order to provide this functionality, it is necessary for the repeater to provide sufficient system gain in each of the uplink and downlink paths to compensate for propagation losses in these paths.
  • the gain in either the uplink or downlink paths
  • the repeater will radiate unnecessarily high signal powers to the subscriber's WCD and/or the base station.
  • radiation of excessive signal power in the downlink path can cause interference (in the form of multiple overlapping coverage areas) with other subscribers.
  • AGCs Automatic Gain Controllers capable of controlling signal gain are known in the art.
  • AGCs are implemented as analog RF or IF circuits, in which a (voltage controlled) variable gain amplifier (VGA) is used to amplify the analog signal.
  • VGA variable gain amplifier
  • the VGA is normally controlled by a voltage level of a control signal, which is usually generated (by a comparator) by comparing a measured parameter (e.g., a received signal power, or a bit error rate) to a predetermined threshold value.
  • AGCs of this type are capable of providing reliable operation within the range of linear operation of the VGA.
  • operation of the AGC becomes increasingly unreliable beyond the linear range of the VGA, and thus the performance of the AGC is typically limited by the linear range of the VGA.
  • it is anticipated that successful operation of the repeater will require that system gain be controllable through a range of up to about 120dB in both the uplink and downlink paths. This range of operation is well beyond the linear range of moderate-
  • a method and apparatus capable of automatically controlling gain throughout a wide operating range, in order to compensate for propagation losses and imperfect antenna isolation, at a moderate cost, remains highly desirable.
  • a main object of the present invention is to provide an apparatus that overcomes at least some of the above-noted deficiencies of the prior art.
  • An object of the present invention is to provide an apparatus for automatically controlling gain throughout a wide operating range.
  • an aspect of the present invention provides an intelligent gain controller (IGC) adapted to control a gain of first and second wideband signal paths.
  • the IGC comprises a respective automatic gain control (AGC) block and slaved Variable Gain Amplifier (VGA) disposed in each wideband signal path, a narrowband detector, and a micro controller.
  • AGC automatic gain control
  • VGA Variable Gain Amplifier
  • Each AGC is adapted to selectively amplify RF signals in the respective wideband signal path.
  • the narrowband detector is adapted to detect respective RF signals within each of the first and second wideband signal paths.
  • the micro controller operates to control each of the AGC blocks using the detected RF signals.
  • the slaved variable gain amplifier of one wideband signal path is arranged to selectively amplify RF signals in the respective wideband signal path based on a signal power of RF signals in the other wideband signal path.
  • Each wideband signal path preferably has a bandwidth corresponding to a respective network system bandwidth. For example, in North America, a bandwidth of 25 MHz may be suitably selected for each of the wideband signal paths.
  • each AGC block includes a respective AGC Variable Gain Amplifier (VGA) and an AGC feedback loop.
  • the AGC Variable Gain Amplifier (VGA) controllably amplifies RF signals in the respective wideband signal path in response to a gain control signal.
  • the AGC feed-back loop supplies a feedback signal to the VGA as the gain control signal.
  • RF signals in the respective wideband signal path are controlled by the VGA in accordance with the feedback signal supplied by the AGC feedback loop.
  • the AGC feed-back loop may include means for controlling a power level of the feedback signal supplied to the AGC VGA, using an AGC control set signal from the micro controller.
  • the means for controlling the power level of the feedback signal may include a Variable Logarithmic Amplifier (VLA) operatively coupled to receive the AGC control set signal from the micro controller.
  • VLA Variable Logarithmic Amplifier
  • the AGC feed-back loop also includes a coupler adapted to supply a sample of RF signals in the respective wideband signal path to the narrowband detector.
  • the narrowband detector includes: a synthesizer, means for channeling RF signals from a selected one of the wideband signal paths using the synthesizer signal; and a detector unit.
  • the synthesizer operates to generate a synthesizer signal having a selected frequency.
  • the means for channeling RF signals processes the selected RF signals such that RF signals above or below the synthesizer signal frequency are channeled within a narrow pass-band centered on an intermediate frequency (IF), and isolated.
  • IF intermediate frequency
  • the detector unit operates to detect a power level of the isolated RF signals at the intermediate frequency.
  • the synthesizer is designed to select the frequency of the synthesizer signal using a synthesizer control signal from the micro controller. This enables the micro controller to progressively change the frequency of the synthesizer signal, while simultaneously monitoring the detected power level of the isolated RF signals to scan the entire bandwidth of each wideband signal path.
  • the means for channeling RF signals includes: a switching input and a filter.
  • the switching unit operates to select RF signals from one of the first and second wideband signal paths, while the filter attenuates a portion of the selected RF signals lying outside the narrow pass-band centered on the intermediate frequency (IF).
  • IF intermediate frequency
  • the micro controller includes: a micro-processor operatively coupled to each of the AGCs and the narrowband detector; and software defining an Adaptive Control Algorithm for controlling operation of the micro-processor.
  • the software may include software code adapted to: monitor a power level of RF signals detected by the narrowband detector; compare the monitored power level to at least one threshold value; and determine an optimum gain in each one of the respective automatic gain control (AGC) blocks using the comparison result.
  • AGC automatic gain control
  • the software code for monitoring the power level of RF signals may also include software code designed to: monitor changes in the power level of the RF signals detected by the narrowband detector; and identify a signal format of the detected RF signals, using the monitored changes.
  • the identified signal format may be used by the software to select the threshold value from among a predetermined set of threshold values.
  • the software code for monitoring the power level of RF signals may also include software code designed to decorrelate desired RF signals from undesired leakage signals within each of the wideband signal paths.
  • This software code may be designed to: inject a predetermined unique code into a selected one of the wideband signal paths; detect a power level of the predetermined unique code in the monitored RF signal; and determine a proportion of leakage signals in the monitored RF signal using on the detected power level of the predetermined unique code in the monitored RF signal. The proportion of leakage signals in the monitored RF signals may then be used to adjust the optimum gain in each one of the respective automatic gain control (AGC) blocks.
  • AGC automatic gain control
  • Fig. 1 is a block diagram schematically illustrating principle elements of an exemplary Adaptive Personal Repeater in which the present invention may be deployed;
  • FIG. 2 is a block diagram schematically illustrating principle elements of an exemplary Intelligent Gain Controller (IGC) in accordance with an embodiment of the present invention
  • FIG. 3 is a block diagram schematically illustrating principle elements of an exemplary uplink AGC usable in the IGC of FIG. 2;
  • FIG. 4 is a block diagram schematically illustrating principle elements of an exemplary downlink AGC usable in the IGC of FIG. 2;
  • FIG. 5 is a block diagram schematically illustrating principal elements of exemplary down converter and micro controller modules usable in the IGC of FIG. 2.
  • the present invention provides an Intelligent Gain Controller (IGC) for use in an on-frequency repeater, such as, for example, an Adaptive Personal Repeater (APR) described in applicant's co-pending U.S. Patent Application No. 09/809,218.
  • an on-frequency repeater operates to mediate RF signal traffic between transceivers of the wireless communications network.
  • the APR creates a local wireless space encompassing one or more mobile transceivers (e.g., subscribers' wireless communications device(s)), and maintains a reliable fixed wireless link to a fixed transceiver (e.g., a base station) in order to "reach back" into the reliable coverage area of the wireless communications network to provide high quality wireless services in an otherwise poorly serviced area of the network.
  • a fixed transceiver e.g., a base station
  • FIG. 1 is a block diagram schematically illustrating principle elements of an exemplary repeater in which the IGC of the present invention may be deployed.
  • the repeater 2 is functionally positioned between a base station 4 of the wireless communications network (not shown) and the subscriber's Wireless Communications Device (WCD) 6.
  • the repeater 2 is an "on-frequency" repeater, in that uplink and downlink RF signals are conveyed through the repeater 2 without altering the respective channel frequencies.
  • the repeater 2 selectively receives and controls (i.e., amplifies and/or attenuates) RF signals, without performing any signal formatting or protocol conversion, thereby rendering the repeater 2 transparent to both the base station 4 and the WCD 6.
  • the subscriber's WCD 6 may take the form of any conventional wireless communications device, such as, for example, Personal Digital Assistants (PDA's), wireless telephone handsets, pagers, and one and two-way wireless messaging devices.
  • PDA's Personal Digital Assistants
  • the subscriber may possess multiple WCDs 6, and may use any one or more WCDs 6 simultaneously.
  • multiple subscribers may be located within the wireless space of a single repeater 2.
  • the illustrated embodiment includes a single WCD 6 within the wireless space defined by the repeater 2.
  • the repeater 2 comprises a Directional Donor Unit (DDU) 8 and a Subscriber Coverage Unit (SCU) 10.
  • the DDU 8 and SCU 10 maybe suitably coupled to each other, for example via a coaxial cable 12, as shown in FIG. 1.
  • the Directional Donor Unit (DDU) 8 operates to establish and maintain a network link 14 between the repeater 2 and the base station 4.
  • the DDU 8 is designed to receive downlink signals from the base station 4 at power levels as low as -120dBm, and transmit uplink signals to the base station 4 at an ERP of up to +37dBm.
  • This transmit and receive performance of the DDU 8 enables maintenance of the network link 14 with the base station 4, even when the DDU 8 is located well beyond the conventional cell and/or network coverage area boundary.
  • the DDU 8 is provided as a single port active antenna comprising a Directional Donor Antenna (DDA) 16 integrated with a Transceiver Diplexer (TRD) 18.
  • a bi-directional port 20 couples the DDU 8 to the SCU 10 via the coaxial cable 12.
  • the Subscriber Coverage Unit (SCU) 10 operates to maintain a local wireless link 22 between the repeater 2 and the subscriber's WCD 6, and define the wireless space (not shown) encompassing the WCD 6. It is anticipated that the coverage area of the wireless space will be very much smaller than a conventional cell of the wireless communications network. For example, in some embodiments, it is expected that the wireless space will extend 25m (or less) from the SCU 10. Other embodiments may provide a larger or smaller coverage area, as desired.
  • the Subscriber Coverage Unit (SCU) 10 is provided as a single port active antenna comprising a Subscriber Coverage Antenna (SCA) 24 integrated with a dual-directional processor (DDP) 26.
  • a bi-directional port 28 couples the SCU 10 to the DDU 8 via the coaxial cable 12.
  • the DDP 26 comprises an Intelligent Gain Controller (IGC) 30 connected between an SCA diplexer 32 and a port diplexer 34.
  • IGC Intelligent Gain Controller
  • the SCA diplexer 32 is coupled to the SCA 24, and the port diplexer 34 is coupled to the bi-directional port 28.
  • These diplexers 32 and 34 operate to separate uplink and downlink signal paths 36 and 38 at the SCA 24 and port 28, respectively.
  • the diplexers 32 and 34 also operate to define and limit the frequency band(s) over which the IGC 30 must maintain stability.
  • the IGC 30 is provided as a hybrid RF, analog and digital processing module capable of detecting and selectively controlling (i.e., amplifying and/or attenuating) RF signal traffic between the base station 4 and the WCD 6.
  • a hybrid processing module in this manner enables the IGC 30 to utilize mathematical (i.e., analog) signal conditioning and gain control techniques, in combination with knowledge-based (i.e., software) control of signal detection and system behaviour.
  • the IGC 30 includes a wide-band uplink signal path 36 and a wide-band downlink signal path 38 coupled between the diplexers 32 and 34, and an IF down-converter and narrow-band detector 40, all of which are controlled by a micro controller 42 in accordance with an Adaptive Control Algorithm (AC A).
  • AC A Adaptive Control Algorithm
  • Each of the uplink and downlink paths 36 and 38 are designed to control, condition and process RF signals within their respective wide-band uplink and downlink channels.
  • the bandwidth of the wideband signal paths 36, 38 will be determined by the communications network, typically in accordance with published standards.
  • the communications network typically in accordance with published standards.
  • publicly accessible cellular communications networks utilize 25MHz band-width uplink and downlink channels centered on 836.5MHz and 881.5MHz, respectively.
  • the uplink and downlink signal paths 36 and 38 can be suitably designed to process RF signals within corresponding 25MHz band-width channels.
  • different band-widths, and different center frequencies can be utilized, as desired.
  • RF signal traffic received by the SCU 10 from the subscriber's WCD 6 is detected by the narrowband down-converter and detector 40, and used by the micro controller 42 to adapt the repeater 2 to the RF characteristics of the WCD 6 by acquiring appropriate uplink and downlink channel frequencies. Thereafter, the IGC 30 selectively controls RF signals within these uplink and downlink channel frequencies.
  • the IGC 30 of the present invention operates to control uplink channel RF signals received from the WCD 6 with a widely varying received power (e.g., between 0 and -60 dBm) for transmission to the base station 4 with a substantially constant repeater uplink Effective Radiation Power (ERP).
  • the repeater uplink ERP can also be adjusted (by operation of the IGC 30) to a minimum value consistent with satisfactory link performance and prevention of system oscillation.
  • a repeater uplink ERP of between about -23dBm and about +37dBm (depending principally on the distance between the repeater 2 and the base station 4) will yield satisfactory performance for most installations.
  • the IGC 30 controls the downlink channel RF signals received from the base station 4 with a substantially constant received power for transmission to the WCD 6 with a varying repeater downlink ERP.
  • the power of downlink. RF signals received from the base station 4 will normally be determined during set-up of the network wireless link 14, and thereafter will not change significantly, at least within the duration of a communications session. It is anticipated that downlink RF signals received from the base station 4 will normally have a power of between about -120 and -60dBm, depending largely on the ERP of the base station 4 and the distance between the base station 4 and the repeater 2.
  • the repeater downlink ERP will be continuously adjusted (by the IGC 30) to a minimum value consistent with satisfactory performance of the local link 22, and so implement adaptive coverage breathing (ACB), as will be described in greater detail below. It is anticipated that an repeater downlink ERP of up to about -20dBm will yield satisfactory performance for most installations.
  • ACB adaptive coverage breathing
  • the uplink path 36 comprises a wide-band uplink Automatic Gain Controller (AGC) 44 and a slaved variable gain amplifier (VGA) 46.
  • AGC Automatic Gain Controller
  • VGA slaved variable gain amplifier
  • the uplink AGC 44 interfaces with the down-converter 40 and the micro controller 42, as will be described in greater detail below.
  • the uplink path 36 is designed to receive, process and transmit RF signals across the entire uplink RF operating band. This processing bandwidth is only limited by the network system bandwidth. For example, North American 800MHz cellular networks utilize an uplink frequency bandwidth of 25MHz centered at 836.5MHz.
  • the uplink path 36 preferably provides substantially constant output leveling over a wide input range.
  • the ERP of uplink RF signals transmitted to the base station 4 will be substantially independent of variations in the signal power of uplink signals received from the WCD 6.
  • the uplink AGC 44 is provided as an extremely fast, wide dynamic range, highly linear block including a single VGA stage 46, fixed gain amplifiers 48 a and 48b cascaded with band-pass filters 50, and a directional coupler 52. Inter-stage attenuators 54a - 54c may also be included to optimize performance.
  • the total gain of the uplink AGC 44 is controlled by the micro controller 42 in an inverse relationship to the received power of uplink RF signals. Thus the uplink AGC 44 gain is increased as the received uplink RF signal power decreases.
  • the VGA 46 preferably has approximately 60 dB of gain variation, and is cascaded with the fixed gain amplifiers 48 to enhance system linearity.
  • the BPFs 50 following the VGA 46 limit the VGA noise to the uplink band, thereby preventing out-of-band signals from capturing the uplink AGC 44 and saturating the uplink output amplifier 62.
  • the directional coupler 52 which may be a 17 dB directional coupler, samples the uplink RF signal downstream of the VGA 46.
  • the sample signal is supplied to a feedback path 56 comprising an RF Variable Log Amplifier (VLA) 58 and a feedback directional coupler 60 which samples the RF signal within the feedback path 56 and supplies the sample signal to the down-converter 40.
  • VLA Variable Log Amplifier
  • the RF VLA 58 is a variable detection amplifier controlled by the micro controller 42.
  • the output of the RF VLA 58 supplies a gain control signal to the uplink AGC VGA 46 and the downlink slaved VGA 68, and may also be supplied to the micro controller 42.
  • the feedback path 56 provides a 25 MHz bandwidth path which operates to ensure system stability by providing substantially instantaneous RF AGC feedback.
  • the feedback path 56 closes the uplink AGC loop, which in turn limits system oscillation by automatically adjusting gain of the VGA 46 in the event of inadequate isolation between the DDA 16 and the SCA 24.
  • the feedback path 56 also provides a means by which the gain of the uplink AGC 44 and the downlink slaved VGA 68 can be forced to a low level by the micro controller 42 to maintain stability during system setup, thereby ensuring the detection of weak desired signals in the downlink path 38 without the need for initial system isolation maximization and/or to disable the system in the event a maj or fault occurs .
  • the uplink slaved VGA 46 preferably has approximately 60dB of gain variation, and accepts a gain control input from the downlink AGC 66 to provide the hardware means to adaptively minimize the uplink channel output power, and thereby mitigate potential interference to other base stations 4. It can be appreciated that in other embodiments of the preferred invention the slaved VGA 46 may be controlled directly by the micro controller 40 to accomplish the same task.
  • the uplink path 36 may also include an output amplifier stage 62, along with one or more inter-stage filters 64a, 64b.
  • the uplink output amplifier 62 provides a fixed gain to compensate for losses in the coaxial cable 12, while the inter-stage filters 64a, 64b limit cascaded noise.
  • the downlink path 38 comprises a wide-band downlink automatic gain controller (AGC) 66, and a slaved variable gain amplifier (VGA) 68.
  • AGC automatic gain controller
  • VGA slaved variable gain amplifier
  • the downlink AGC 66 interfaces with the down-converter 40 and the micro controller 42, as will be described in greater detail below.
  • the downlink path 38 is designed to receive, process and transmit the entire downlink RF channel operating band.
  • North American 800MHz cellular network has a downlink frequency bandwidth of 25MHz centered at 881.5 MHz.
  • the downlink AGC 66 preferably provides substantially constant output leveling over a wide input range. As shown in FIG. 4, the downlink AGC 66 is preferably provided as an extremely fast, wide dynamic range, highly linear block comprising a single VGA stage 70, a fixed gain amplifier 72 cascaded with a pair of band-pass filters 74a and 74b, and a directional coupler 76. Inter-stage attenuators 78a-78c may also be included to optimize performance.
  • the downlink AGC VGA 70 preferably has approximately 60 dB of gain variation, and is cascaded with the fixed gain amplifier 72 to enhance system linearity while minimizing the cascaded noise figure.
  • the BPFs 74a and 74b operate to limit VGA noise to the 25 MHz downlink bandwidth, thereby preventing out-of-band signals from capturing the downlink AGC 66 and saturating the downlink path output amplifier 90.
  • the directional coupler 76 which may be a 17 dB directional coupler, samples the downlink RF signal downstream of the VGA 70.
  • the sample signal is supplied to a feedback path 80 which includes a cascaded RF amplifier 82 and log amplifier 84, and a feedback directional coupler 86 which samples the RF signal within the feedback path 80 and supplies the sample signal to the down-converter 40.
  • the RF log amplifier 84 is preferably a variable detection log amplifier controlled by the micro controller 42. The output of the RF log amplifier 84 supplies a gain control signal to the downlink AGC VGA 70 and the uplink path slaved VGA 46, and may also be supplied to the micro controller 42.
  • the feedback path 80 preferably provides a 25 MHz bandwidth path which operates to ensure system stability by providing substantially instantaneous RF AGC feedback.
  • the feedback path 80 closes the AGC loop, which in turn limits system oscillation by automatically adjusting gain of the VGA 70 in the event of inadequate isolation between the DDA 16 and SCA 24.
  • the feedback path 80 also provides a means by which the gain of the downlink AGC 66 can be forced to a low level by the micro controller 42 to disable the system in the event a major fault occurs.
  • the downlink slaved VGA 68 preferably has about 60dB of gain variation, and accepts a gain control input from the uplink path AGC 44 to provide a hardware means to adaptively minimize the downlink output power.
  • the downlink slaved VGA 68 operates to reduce gain in the downlink path 38, as the received power of uplink RF signals increases, thereby reducing the coverage area of the subscriber's personal wireless space. It can be appreciated that in other embodiments of the preferred invention the slaved VGA 68 may be controlled directly by the micro controller 42 to accomplish the same task.
  • the IGC downlink path 38 may also include a pre-amplifier 88, and an output amplifier stage 90. These elements can be cascaded with a band-pass filter (BPF) 92 and inter-stage attenuators 94a and 94b to reduce cascaded noise and optimize performance.
  • the pre-amplifier 88 operates to preserve the S/N ratio established by the DDU 8, and buffers the port diplexer 34 from BPF 92. This BPF 92, together with the port diplexer 34, limits the downlink bandwidth to 25 MHz, rejecting both image and frequency crossover noise and any out-of-band signals, including RF signals in the uplink path 36.
  • the output amplifier 90 provides a fixed gain to provide the necessary power output to the SCA 24.
  • the down-converter 40 comprises a switching input 96, an active mixer 98, a selectable band pass filter 100, a log amp detector 102, and a synthesizer 104 which can be selectively tuned by the micro controller 42.
  • the switching input 96 is controlled by the micro controller 42 to supply an RF signal from a selected one of the uplink and downlink AGCs 44 and 66 to the active mixer 98.
  • the synthesizer 104 is controlled by the micro controller 42 to supply an RF synthesized signal to the mixer 98.
  • the RF sample signal and the synthesizer signal are processed by the mixer 98, in a conventional manner, to generate an intermediate frequency (LF) signal.
  • LF intermediate frequency
  • This LF signal is used by the selectable BPF 100 to channel the RF sample signal by selectively attenuating portions of the RF sample signal lying outside a narrow pass-band (of, for example, about 30 KHz bandwidth) centered on the IF.
  • the output of the selectable BPF 100 is supplied to the detection log amplifier 102, which operates to detect the presence (and power level) of desired RF signals in each of the uplink and downlink channels (depending on the state of the switching input 96).
  • the output of the detection log amplifier 102 is supplied to the micro controller 42, and is used for decision making in accordance with the adaptive control algorithm (ACA).
  • ACA adaptive control algorithm
  • the selectable BPF 100 and detection log amplifier 102 operate to detect the power level and number of desired RF signals within the uplink channel 36, and this information can be used by the micro controller 42 to determine the signal format, set the appropriate power (i.e., gain) in the uplink path 36 and, for each detected desired RF signal, tune the synthesizer 104 to the corresponding downlink channel frequency (e.g., 45 MHz above the frequency of the detected signal), if necessary.
  • the selectable BPF 100 and detection log amplifier 102 operate to detect weak desired signals within the downlink channel 38, and this information can be used by the micro controller 42 to determine the downlink signal format, set the appropriate power (i.e., gain) in the downlink path 38 and, for each detected desired RF signal, tune the synthesizer 104 to the corresponding uplink channel frequency (e.g., 45 MHz below the frequency of the detected RF signal), if necessary.
  • the design of the down-converter 40 enables the micro controller 42 to detect any number of weak desired uplink and downlink RF signals that are below either high-level wanted signals and/or adjacent carrier signals, or the system noise floor within a respective 25 MHz bandwidth.
  • the micro controller 42 can provide a digital correction to each of the AGCs 44 and 66, thereby offsetting the respective leveled outputs to the weak desired signals.
  • This arrangement enables the IGC 30 (and thus the repeater 2) to mediate signal traffic between the base station 4 and any number of WCDs 6 within the wireless space of the repeater 2.
  • the micro controller 42 comprises a micro-processor 106 operating under the control of suitable software that implements an Adaptive Control Algorithm (ACA), one or more Digital-to-Analog converters (DACs) 108 and Analog-to-Digital Converters (ADCs) 110 which operate, in a manner well known in the art, to provide translation between digital and analog signal formats, and thereby enable interaction between the micro controller 42 and other elements of the IGC 30.
  • ACA Adaptive Control Algorithm
  • DACs Digital-to-Analog converters
  • ADCs Analog-to-Digital Converters
  • the adaptive control algorithm provides the necessary processing control for IGC operation without intervention after installation. It may also control operation during system set-up, in order to simplify installation of the repeater 2.
  • the micro controller 42 may also include a configuration switch 112 to enable the subscriber to control an operating configuration (or mode) of the micro controller 42.
  • the configuration switch 112 which may be provided as a conventional DIP switch, may have one or more settings allowing the subscriber to select an operating configuration (or mode) of the micro controller 42. Exemplary settings of the configuration switch may include:
  • the micro controller 42 may reduce AGC gain (and thus transmission power levels) to enable the subscriber to adjust the placement and positioning of the DDU 8 and SCU 10;
  • Carrier A/B band select setting which may be used by the subscriber to select a desired carrier.
  • Carrier A/B bands may be selected together or individually;
  • the micro-processor 106 operates under the control of suitable software that implements the Adaptive Control Algorithm (ACA).
  • ACA Adaptive Control Algorithm
  • the ACA provides knowledge-based control over the functionality of the IGC 30, thereby providing dramatically greater versatility than is possible with conventional (analog math-based) RF signal processing techniques.
  • the ACA enables the following functionality of the IGC 30:
  • the uplink and downlink paths 36 and 38 are wide bandwidth RF signal paths capable of controlling RF signals across the entire 25MHz bandwidth of the uplink and downlink channels.
  • the down-converter 40 is designed to detect individual desired RF signals within the wide bandwidth paths 36 and 38. h particular, the down-converter 40 operates to detect the presence (and power level) of an RF signal within a narrow pass-band (of, for example, about 30 KHz bandwidth) centered on the IF frequency generated by the mixing of the synthesizer signal and the RF signal. By tuning the synthesizer 104 to various frequencies in succession, the micro controller 42 can scan the entire 25 MHz bandwidth of each channel to detect weak desired RF signals.
  • the speed at which the micro-controller 42 can scan an entire channel (e.g. 25MHz band-width) will vary with the bandwidth of the selectable BPF 100.
  • a larger bandwidth of the selectable BPF 100 increases the scanning speed, and thus allows the micro-controller 42 to isolate the discrete RF signals faster. In most cases, this increased processing speed is obtained at a cost of reduced sensitivity to weak signals.
  • the selectable filter 100 by dynamically switching the selectable filter 100 from a wide to narrow bandwidth and thereby restricting the detection to a narrowband centered on the intermediate frequency (e.g. by reducing the bandwidth of the selectable BPF 100), the down-converter 40 and micro controller 42 can detect weak desired RF signals that are embedded in noise.
  • the down-converter 40 and micro controller 42 cooperate to implement a digital offset correction technique in which the gain of a wide-band AGC is set for RF signals that may not have captured the AGCs.
  • a wide-band AGC will normally level to the highest signal that captures the AGC within a defined bandwidth. If no signals are present, the AGC may level to the thermal and system noise of a given bandwidth.
  • the narrow-band detection capability of the down-converter 40 is used to detect the (weak) desired signals embedded in the noise. Detection of the desired uplink and downlink signals is then used by the micro controller 42 to offset the output to which the respective AGCs 44 and 66 level. This same technique can also be used to detect weak and moderate desired signals in the presence of high-level unwanted signals that would otherwise capture an AGC and limit the system gain for the desired signals.
  • the ACA can implement a variety of signal evaluation techniques, as desired. For example, by controlling the bandwidth of the selectable
  • the micro controller 42 can detect changes in the RF signals in each of the paths 36 and 38. These changes can be used to identify the format of the RF signals being used by the subscriber's WCD 6.
  • periodic pulse-like changes in the signal level in the uplink path 37 indicates that the WCD 6 is using a narrow-band pulsed (e.g., Time Division Multiple Access (TDMA)) signal format.
  • Changes in power level due to changes in the bandwidth of the selectable BPF 100 indicates that the WCD 6 is using a broad-band (e.g., Code Division Multiple Access (CDMA)) signal format. If neither of these types of changes are detected, then the WCD 6 is using a narrowband continuous (e.g.,
  • TDMA Time Division Multiple Access
  • AMPS Advanced Mobile Phone Service
  • Smart antenna technology has been used in a wide variety of applications to combat interference. This smart antenna technology can be effectively applied at the base station 4 to reduce the interference problem for both the downlink (interference to the WCD 6 from other base stations) and the uplink (interference to the base station 4 from other WCDs) communication paths.
  • smart antenna technology has generally not been used to mitigate interference occurring at the WCD end of the link. This is largely due to the size and power constraints of the WCD, and the requirement that the WCD's antenna must be omni-directional to successfully connect to, and communicate with, the base station 4.
  • the repeater 2 implements a technique of Adaptive Interference Mitigation, in which RF interference in the subscriber's personal wireless space is mitigated by a combination of one or more of: physical antenna separation; the use of a narrow beam network link 14 between the repeater 2 and the base station 4; and Adaptive Coverage Breathing (ACB).
  • Physical separation of the DDA 16 and SCA 24 reduces the possibility that that the WCD 6 will receive uplink RF signals transmitted by the DDA 16 toward the base station 4, and hence all but eliminates the possibility of the WCD receiver being overwhelmed by the DDA's ERP.
  • the DDA 16 Further isolation between the DDA 16 and the WCD 6 is achieved by the use of a directional antenna for the DDA 16, which results in a comparatively narrow beam propagation path of the network link 14.
  • the probability that the WCD 6 will pass into the narrow propagation path of the network link 14 can be reduced (to near zero) by suitable placement of the DDA 16.
  • interference within the subscriber's wireless space due to signals propagating from other base stations is dramatically reduced, because the DDA 16 will tend to only receive signals transmitted by base stations lying within the narrow propagation path of the network link 14.
  • signals emitted by base stations lying outside the network link 14 will not be amplified by the DDA 16 and transmitted into the subscriber's personal wireless space by the repeater 2.
  • the repeater 2 operates to selectively detect and amplify the desired signal(s) relative to the interference.
  • the IGC 30 amplifies and conditions the desired RF signals for transmission into the subscriber's personal wireless space such that the WCD 6 receives a substantially constant downlink signal power, independent of its location relative to the repeater 2.
  • the ACA implements a technique of Adaptive Coverage Breathing (ACB), such that the coverage area of the subscriber's personal wireless space is automatically adjusted in order to ensure: acceptable signal-to-noise ratio in both the uplink and downlink paths of the local link 22; the received downlink signal power is maintained substantially constant at the WCD 6; and transmission (i.e., uplink RF signal) power from the WCD 6 is minimized.
  • ACB Adaptive Coverage Breathing
  • Adaptive Coverage Breathing comprises a technique of RF power management that enables the coverage area of the subscriber's personal wireless space to "breathe”; adaptively expanding and contracting to the position of the subscriber's WCD 6 relative to the SCA 24. This allows both the WCD 6 and the SCA 24 to radiate only the necessary powers needed to maintain reliable signaling over the local link 22. As the WCD 6 moves relative to the SCA 24, the coverage area of the personal wireless space changes continuously to adapt to the movement.
  • the IGC 30 causes the coverage area to contract, so that the personal wireless space is limited to just encompass the WCD 6. This can be accomplished by monitoring the signal power of uplink RF signals received from the WCD 6, and then adjusting the gain of the downlink VGA 68 to control the transmission power (i.e., the ERP) of downlink RF signals accordingly. If two or more WCDs are being used simultaneously, then the IGC 30 can expand the coverage area to accommodate the WCD located furthest from the SCA 26 (or transmitting the weakest uplink RF signals). This can be achieved by measuring the power of uplink RF signals received from each of the wireless communications devices, and adjusting the downlink transmit power based on the measured signal power level of the weakest RF signal.
  • a minimum acceptable uplink channel RF signal power of the WCD 6 can be negotiated with the base station at a start of a communications session. This uplink channel RF signal power is then maintained substantially constant by the WCD 6 (during the communications session).
  • the IGC 30 adapts to changes in the position of the WCD 6 by accepting widely varying uplink channel RF signal powers from the WCD 6 and controlling the downlink channel ERP to hold the downlink RF signal power received by the WCD 6 substantially constant.
  • the variation in received uplink channel RF signal power may be as high as 50 to 60 dB, depending largely on the proximity of the WCD 6 to the SCA 24.
  • the received uplink channel RF signal power level can be measured by the down-converter 40, and used by the micro controller 42 to control the downlink channel RF ERP. For example, if the received power of the uplink RF signals is greater than a predetermined minimum threshold, then the downlink RF signal transmit power can be reduced (i.e., the coverage area of the subscriber's personal wireless space reduced) to improve spectrum efficiency, conserve energy, increase reliability and reduce system gain. Conversely, if the measured power of the received uplink RF signals drops below the predetermined minimum threshold, then the downlink RF signal ERP can be increased (i.e., the coverage area of the subscriber's personal wireless space 6 expanded)to improve the signal-to-noise ratio.
  • the ACA may select the value of the threshold, from among a set of predetermined threshold values. This selection may, for example, be based on a determination of the signal format as described above.
  • the IGC 30 implements Adaptive Coverage Breathing (ACB) and Coverage Area Signature (CAS) to prevent oscillations occurring due to system instability during installation and subsequent operation of the repeater 2.
  • ACB Adaptive Coverage Breathing
  • CAS Coverage Area Signature
  • Adaptive Coverage Breathing ensures that minimum power is transmitted in both the uplink and downlink paths to maintain reliable network and local links 14 and 22.
  • the system gain is only as high as it needs to be in both paths 36 and 38, resulting in greater system stability than would be the case if the system gain was fixed at a level high enough to provide satisfactory performance under most operating conditions.
  • leakage signals i.e., signals propagating between the DDA 16 and SCA 24
  • desired signals received from the base station 4 and WCD 6.
  • downlink RF signals are transmitted by both the base station 4 and the SCA 24 at the same frequency
  • imperfect isolation between the SCA 24 and the DDA 16 will result in the DDA 16 receiving signals from both the base station 4 and the SCA 24. Since these signals will be closely correlated (in time) it is difficult to determine what portion of the total signal received at the DDA 16 is the desired downlink RF signal from the base station 4, and what portion is the undesired leakage signal from the SCA 24.
  • the ACA implements a Coverage Area Signature (CAS) technique to de-correlate leakage signals from the desired received signals.
  • CAS Coverage Area Signature
  • the CAS technique involves transmitting a unique code (or signature) as a signal having a predetermined power, and then monitoring received signals to detect the transmitted code. Comparison of the signal power of the detected code to the known transmit power provides an indication of the power level of leakage signals, and thus the total system isolation. Based on this information, the micro controller 42 can control the gain in each of the paths 36 and 38 to limit the leakage signal power to a predetermined acceptable level.
  • the unique code may be provided as any signal pattern that can be reliably detected within the uplink and downlink RF signal traffic.
  • the unique code is transmitted as a form of RF modulation (either in amplitude and/or phase changes that instantaneously affect the entire system operating RF bandwidth), as this provides for a more accurate estimate of the degree of signal leakage at any frequency of interest.
  • the unique code is provided as a low level dither (or fade) imposed on the entire RF signal traffic within each path 36 and 38.
  • the micro controller 42 can control the downlink slaved VGA 68 to dither the downlink path gain, and thereby effect an "amplitude modulation" of downlink RF signals transmitted by the SCA 24.
  • the dither pattern (in time) defines the unique code, and may take the form of a periodic change in signal power or may encode data such as, for example, a predetermined sequence of bits. In either case, the modulation power can be kept low enough to avoid disrupting the WCD 6, and the variations in signal power will have no effect on the frequency modulated content of the downlink RF signals.
  • the micro controller 42 can monitor the detection signal generated by the downlink AGC 66 to detect changes in the received power of downlink RF signals received through the DDA 16. These detected changes can be correlated (in time) with the downlink path gain dither to detect the unique code within the received downlink RF signals. The micro controller 42 can then compare the modulation power of the detected unique code (within the received downlink RF signals) to the downlink path gain dither introduced by the downlink slaved VGA 68, to obtain an indication of the signal leakage between the SCA 24 and the DDA 16.
  • the micro controller 42 can control the uplink slaved VGA 46 to dither the uplink path gain, and thereby impose an "amplitude modulation" onto the uplink RF signals.
  • the modulation power can be kept low enough to avoid disrupting the base station 4, and the variations in signal power will have no effect on the frequency modulated content of the uplink RF signals.
  • the micro controller 42 can monitor the detection signal generated by the uplink AGC 44 to detect changes in the received power of uplink RF signals received through the SCA 24. These detected changes can be correlated (in time) with the uplink path gain dither to detect the unique code within the received uplink RF signals.
  • the micro controller 42 can then compare the modulation power of the detected unique code (within the received uplink RF signals) to the uplink path gain dither introduced by the uplink slaved VGA 46, to obtain an indication of the signal leakage between the DDA 16 and the SCA 24.
  • the micro controller 42 can control the uplink and downlink AGCs 44 and 66 and/or the slaved VGAs 46 and 68 as required to maintain the signal leakage at an acceptable level. For example, if the signal leakage in either path 36 and 38 is found to be above a predetermined threshold level, the micro controller 42 can control the respective uplink or downlink AGC 44 and 66 to reduce the path gain. This reduction will have the effect of reducing the coverage area of the subscriber's personal wireless space, but will not otherwise disrupt the performance of either of the network or local wireless links 14 and 22.
  • the predetermined threshold level of acceptable signal leakage can be suitably selected to provide a balance between system stability (i.e., resistance to oscillation) and performance of the network and local wireless links 14 and 22.
  • system stability i.e., resistance to oscillation
  • performance of the network and local wireless links 14 and 22 When taken in combination with other sources of isolation between the SCA 24 and the DDA 16 (e.g., front to back ratios of the DDA 16 and SCA 24; polarization loss and propagation losses), it is possible to set a threshold level which ensures unconditional system stability while preserving sufficient range of gain variation in the uplink and downlink paths 36 and 38 to deliver satisfactory performance of the network and local wireless links 14 and 22.
  • Prior art repeaters typically require 10-15 dB of isolation/gain margin.
  • the present invention provides an Intelligent gain controller capable of controlling the gain in each of the wideband uplink and downlink signal paths. Weak desired signals are detected using a narrowband down converter and detector, and these desired signals are monitored by the micro controller.
  • the micro controller operates, under control of suitable software implementing an Adaptive Control Algorithm, to adjust the gain in each of the uplink and downlink paths.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Relay Systems (AREA)
  • Circuits Of Receivers In General (AREA)

Abstract

L'invention concerne un dispositif de commande de gain qui fonctionne pour réguler le gain dans chacune des voies de signaux de liaison descendante et de liaison montante à large bande. On détecte des signaux souhaités faibles, à l'intérieur de chaque voie de signaux à large bande en utilisant un convertisseur abaisseur de bande étroite et un détecteur, ces signaux souhaités étant contrôlés par un micro-contrôleur. En fonction des signaux contrôlés, le micro-contrôleur fonctionne, sous la commande d'un logiciel approprié installant un algorithme de contrôle adaptatif, de manière à ajuster le gain dans chacune des voies montante et descendante en vue d'optimiser de façon dynamique la capacité .
EP02732268A 2001-05-29 2002-05-27 Commande de gain intelligente dans un repeteur sur la meme frequence Withdrawn EP1391060A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US09/865,466 US6889033B2 (en) 2000-10-18 2001-05-29 Intelligent gain control in an on-frequency repeater
US865466 2001-05-29
PCT/CA2002/000772 WO2002098014A2 (fr) 2001-05-29 2002-05-27 Commande de gain intelligente dans un repeteur sur la meme frequence

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EP1391060A2 true EP1391060A2 (fr) 2004-02-25

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EP (1) EP1391060A2 (fr)
CN (1) CN1471765A (fr)
AU (1) AU2002304917A1 (fr)
WO (1) WO2002098014A2 (fr)

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US8265546B2 (en) 2009-05-11 2012-09-11 Qualcomm Incorporated Gain adjustment stepping control in a wireless repeater
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EP3607671A1 (fr) * 2017-04-06 2020-02-12 Wilson Electronics, LLC Techniques pour configurer la puissance ou le gain d'un répéteur
CN114900221B (zh) * 2022-07-14 2022-10-04 深圳国人无线通信有限公司 一种自适应调整直放站上下行增益的方法和系统

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US10805026B2 (en) 2016-10-07 2020-10-13 Wilson Electronics, Llc Narrowband signal detection

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WO2002098014A2 (fr) 2002-12-05
CN1471765A (zh) 2004-01-28
AU2002304917A1 (en) 2002-12-09
WO2002098014A3 (fr) 2003-09-18

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