US20160173149A1

US20160173149A1 - Automatic Twist and Sway Compensation in a Microwave Backhaul Transceiver

Info

Publication number: US20160173149A1
Application number: US14/249,014
Authority: US
Inventors: Curtis Ling
Original assignee: MaxLinear Inc
Current assignee: MaxLinear Inc
Priority date: 2013-04-09
Filing date: 2014-04-09
Publication date: 2016-06-16
Also published as: US20160255510A1; US20140347222A1; US9642020B2; US20170215091A1; US9338661B2; US10111110B2; US20170118657A1; US10531312B2; US20190014486A1; US20140370936A1; US10412598B2; US9572043B2

Abstract

A first microwave backhaul transceiver may comprise an antenna array and circuitry. The circuitry may determine misalignment of the first microwave backhaul transceiver, and electronically adjust a radiation pattern of the antenna array to compensate for the determined misalignment of the microwave backhaul transceiver. The circuitry may perform the adjustment of the radiation pattern in real time to compensate for effects of wind on the microwave backhaul transceiver. The circuitry may detect movement of the microwave backhaul transceiver and translate the detected movement into angular misalignment of the radiation pattern of the antenna array. The adjustment of the radiation pattern of the antenna array may comprise an adjustment of a polarization orientation of the antenna array.

Description

PRIORITY CLAIM

This application claims priority to and the benefit of the following application(s), each of which is hereby incorporated herein by reference:
U.S. provisional patent application 61/809,935 titled “Microwave Backhaul” filed on Apr. 9, 2013;
U.S. provisional patent application 61/881,016 titled “Microwave Backhaul Methods and Systems” filed on Sep. 23, 2013; and
U.S. provisional patent application 61/884,765 titled “Microwave Backhaul Methods and Systems” filed on Sep. 23, 2013.

INCORPORATION BY REFERENCE

The entirety of each of the following applications is hereby incorporated herein by reference:
U.S. patent application Ser. No. 13/933,865 titled “Method And System For Improved Cross Polarization Rejection And Tolerating Coupling Between Satellite Signals” filed on Jul. 2, 2013.

BACKGROUND

Limitations and disadvantages of conventional approaches to microwave backhaul will become apparent to one of skill in the art, through comparison of such approaches with some aspects of the present method and system set forth in the remainder of this disclosure with reference to the drawings.

BRIEF SUMMARY

Methods and systems are provided for automatic twist and sway compensation in a microwave backhaul transceiver, substantially as illustrated by and/or described in connection with at least one of the figures, as set forth more completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example microwave backhaul link between a first microwave backhaul transceiver and a second microwave backhaul transceiver.

FIG. 2 shows an example implementation of a steerable microwave backhaul transceiver.

FIG. 3 shows an example implementation of the subassembly of FIG. 2.

FIG. 4A shows a first example implementation of the circuitry of FIG. 3.

FIG. 4B shows a second example implementation of the circuitry of FIG. 3.

FIG. 5A shows an example configuration of the beamforming circuitry of FIG. 4A.

FIG. 5B shows an example configuration of beamforming components of the digital signal processing circuitry of FIG. 4B.

FIG. 6A illustrates effects of sway (e.g., due to wind) on a microwave backhaul link between link partners.

FIG. 6B illustrates effects of twist (e.g., due to wind) on a microwave backhaul link between link partners.

FIG. 6C illustrates effects of tower sway (e.g., due to wind) on polarizations of a microwave backhaul link between link partners.

FIG. 7 is a flowchart illustrating an example process for misalignment compensation in a microwave backhaul transceiver.

DETAILED DESCRIPTION

As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code and may comprise a second “circuit” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the terms “e.g.,” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled, or not enabled, by some user-configurable setting. As used herein, “microwave” frequencies range from approximately 300 MHz to 300 GHz and “millimeter wave” frequencies range from approximately 30 GHz to 300 GHz. Thus, the “microwave” band includes the “millimeter wave” band.
FIG. 1 depicts an example microwave backhaul link between a first microwave backhaul transceiver and a second microwave backhaul transceiver. Shown are a tower 108 to which access network antennas 112 and remote radio head (RRH) 110 are attached, a baseband unit 104, a tower 122 a to which microwave backhaul transceiver 120 a (comprising subassembly 114 a and reflector 116 a) is attached, and a tower 122 b to which microwave backhaul transceiver 120 b (comprising subassembly 114 b and reflector 116 b) is attached. At any particular time, there may be one or more active (i.e., carrying traffic or synchronized and ready to carry traffic after a link setup time that is below a determined threshold) links 106 (shown as wireless, but may be wired or optical) between the RRH 110 and the BBU 104. At any particular time, there may be one or more active backhaul links 118 between the pair of backhaul transceivers 120 a and 120 b and/or between one of the transceivers 120 a and another one or more backhaul transceivers not shown.
The antennas 112 are configured for radiating and capturing signals of an access network (e.g., 3G, 4G LTE, etc. signals to/from mobile handsets). Although the example pair of microwave transceivers 120 a and 120 b are used for backhauling cellular traffic, this is just one example type of traffic which may be backhauled by microwave transceivers, such as 120 a and 120 b, that implement aspects of this disclosure.
For an uplink from a mobile handset to the core network 102, the antennas 112 receive signals from the handset and convey them to the RRH 110. The RRH 110 processes (e.g., amplifies, downconverts, digitizes, filters, and/or the like) the signals received from the antennas 112 and transmits the resulting signals (e.g., downconverted I/Q signals) to the baseband unit (BBU) 104 via link(s) 106. The BBU 104 processes, as necessary, (e.g., demodulates, packetizes, modulates, and/or the like) the signals received via link(s) 106 for conveyance to the microwave backhaul transceiver 120 a via link 113 a (shown as wired or optical, but may be wireless). The microwave backhaul transceiver 120 a processes, as necessary (e.g., upconverts, filters, beamforms, and/or the like), the signals from BBU 104 for transmission via the subassembly 114 a and reflector 116 a over microwave backhaul link(s) 118. The microwave transceiver 120 b receives the microwave signals over microwave backhaul link(s) 118 via the subassembly 114 b and reflector 116 b, processes the signals as necessary (e.g., downconverts, filters, beamforms, and/or the like) for conveyance to the cellular service provider core network 102 via link 113 b.
For a downlink from the core network 102 to the mobile handset, data from the core network 102 is conveyed to microwave backhaul transceiver 120 b via link 113 b. The transceiver 120 b processes, as necessary (e.g., upconverts, filters, beamforms, and/or the like), the signals from the core network 102 for transmission via the subassembly 114 b and reflector 116 b over link(s) 118. Microwave transceiver 120 a receives the microwave signals over the microwave backhaul link(s) 118 via the subassembly 114 a and reflector 116 a, and processes the signals as necessary (e.g., downconverts, filters, beamforms, and/or the like) for conveyance to the BBU 104 via link 113 a. The BBU 104 processes the signal from transceiver 120 a as necessary (e.g., demodulates, packetizes, modulates, and/or the like) for conveyance to RRH 110 via link(s) 106. The RRH 110 processes, as necessary (e.g., upconverts, filters, amplifies, and/or the like), signals received via link 106 for transmission via an antenna 112.
FIG. 2 shows an example implementation of a steerable microwave backhaul transceiver. The depicted transceiver 120 represents each of the transceivers 120 a and 120 b described above with reference to FIG. 1. The example transceiver 120 comprises the subassembly 114 mounted to a support structure 204 (which may, in turn, mount the assembly to the mast/tower 122, building, or other structure, not shown in FIG. 2), and a link 113 which represents each of the links 113 a and 113 b. The subassembly 114 comprises an antenna array 202 which in turn comprises a plurality of antenna elements. The subassembly 114 may be mounted such that the antenna elements are positioned at or near a focal plane of the reflector 116. The subassembly 114 may comprise, for example, one or more semiconductor dies (“chips”) arranged on one or more printed circuit boards. The antenna elements may be, for example, horns and/or microstrip patches. In the example implementation depicted, the antenna elements capture signals reflected by reflector 116 for reception and bounce signals off the reflector 116 for transmission. The radiation pattern 208 of the antenna array 202 corresponds to a radiation pattern 206 after reflection off the reflector 116. Although the radiation patterns may comprise multiple lobes, only a main lobe is shown for simplicity of illustration. In another implementation, the antenna elements may directly receive backhaul signals, or receive them through a lens, for example.
FIG. 3 shows an example implementation of the subassembly of FIG. 2. The example subassembly 114 comprises four feed horns 306 ₁-306 ₄, and circuitry (e.g., a chip or chipset) 302. The circuitry 302 drives signals to the horns 306 ₁-306 ₄via one or more of feed lines 304 ₁-304 ₈for transmission, and receives signals from the horns 306 ₁-306 ₄via feed lines 304 ₁-304 ₈for reception. The circuitry 302 is operable to control the phases and/or amplitudes of signals output to the feed lines 304 ₁-304 ₈so as to achieve desired transmit radiation patterns. Similarly, the circuitry 302 is operable to control the phases and/or amplitudes of signals received from the feed lines 304 ₁-304 ₈so as to achieve desired receive radiation patterns.
The feed lines 304 ₁-304 ₄correspond to a first polarization and the feed lines 304 ₅-304 ₈correspond to a second polarization. Accordingly, the subassembly 114 may be operable to concurrently receive two different signals on the same frequency but having different polarizations, concurrently transmit two different signals on the same frequency but having different polarizations, and/or concurrently transmit a first signal having a first polarization and receive a second signal having a second polarization. Furthermore, the radiation pattern for the two polarizations may be controlled independently of one another. That is two independent sets of amplitude and phase beamforming coefficients may be maintained by circuitry 302 as, for example, described below with reference to FIGS. 5A-5B.
FIG. 4A show a first example implementation of the circuitry of FIG. 3. In the example implementation shown, the circuitry 302 comprises analog front-ends 402 ₁-402 ₈, a beamforming circuit 404, analog-to-digital converter (ADC) 406, one or more sensors 414, digital circuitry 408, and a digital-to-analog converter (DAC) 440. The circuitry 302 outputs received data onto link 113 (e.g., coaxial cable) and receives to-be-transmitted data via link 113.
The sensor(s) 114 may be operable to determine movement, orientation, geographic position, and/or other physical characteristics of the transceiver 120. Accordingly, the sensor(s) 414 may comprise, for example, a gyroscope, an accelerometer, a compass, a GPS receiver, a laser diode, a laser detector, and/or the like. Additionally or alternatively, the sensor(s) 114 may be operable to determine atmospheric conditions and/or other physical obstructions between the transceiver 120 and potential microwave backhaul link partners (e.g., the sensor(s) 114 may comprise, for example, a hygrometer, a psychrometer, and/or a radiometer). The sensor(s) 414 may output readings/measurements as signal 415.
For receive operations, each front-end circuit 402 _n(1≦n≦N, where N=8 in the example implementation depicted) is operable to receive a microwave signal via feed line 304 _n. The front-end circuit 402 _nprocesses the signal on feed line 304 _nby, for example, amplifying it via low noise amplifier LNA 420 _n, filtering it via filter 426 _n, and/or downconverting it via mixer 424 _nto an intermediate frequency or to baseband. The local oscillator signal 431 _nfor the downconverting may be generated by the circuit 404, as described below. The result of the processing performed by each front-end circuit 402 _nis a signal 403 _n.
The ADC 406 is operable to digitize signal 405 to generate signal 407. The bandwidth of the ADC 406 may be sufficient such that it can concurrently digitize entire microwave backhaul bands comprising a plurality of channels or sub-bands (e.g., the ADC 406 may have a bandwidth of 1 GHz or more).
The DAC 440 is operable to convert digital signal 439 (e.g., a digital baseband signal) to an analog signal 441.
For receive, the digital circuitry 408 is operable to process the digital signals 407 for output to link 113. The processing may include, for example, symbol-to-bits demapping, FEC decoding, deinterleaving, equalizing, and/or the like. The processing may include, for example, performing an interference (e.g., cross-polarization interference) cancellation process such as is described in, for example, the above-incorporated U.S. patent application Ser. No. 13/933,865. The processing may include, for example, channelization to select, for output to the link 113, sub-bands or channels of the signal 407. The processing may include, for example, band stacking, channel stacking, band translation, and/or channel translation to increase utilization of the available bandwidth on the link 113.
For transmit, the digital circuitry 408 is operable to perform digital baseband processing for preparing data received via link 113 to be transmitted via the microwave backhaul link(s) 118. Such processing may include, for example, processing of packets received via the link 113 to recover the payload data from such packets, and then packetization, modulation, etc. to generate a microwave backhaul digital baseband signal 439 carrying the payload data. Parameters used by the digital circuit 408 for processing the digital signals 407 may be adjusted based on SNR and/or some other performance metric of the microwave backhaul link(s) 118. Thus, rather than having fixed parameters (packet size, bandwidth, modulation order, FEC code word length, and/or the like) designed to handle worst-case conditions, microwave backhaul transceivers in accordance with this disclosure may be operable to take advantage of the fact that most of the time worst-case conditions are not present and, therefore, parameters may be adjusted to increase range, increase throughput, decrease latency, decrease power consumption, and/or the like during non-worst-case conditions.
The beamforming circuit 404 comprises local oscillator synthesizer 428 operable to generate a reference local oscillator signal 429, and comprises phase shift circuits 430 ₁-430 _Noperable to generate N phase shifted versions of signal 429, which are output as signals 431 ₁-431 _N. The amount of phase shift introduced by each of the circuits 430 ₁-430 _Nmay be determined by a corresponding one of a plurality phase coefficients. The plurality of phase coefficients may be controlled to achieve a desired radiation pattern of the antenna elements 306 ₁-306 ₄(e.g., to compensate for misalignment as described with reference to FIGS. 6A-7 below). In another example implementation, additional front-end circuits 402 and phase shifters 430 may be present to enable concurrent reception of additional signals via the antenna elements 306 ₁-306 _N.
The beamforming circuit 404 also comprises a circuit 432 which is operable to perform weighting of the signals 403 ₁-403 ₈by their respective amplitude coefficients determined for the desired radiation pattern (e.g., to compensate for misalignment as described with reference to FIGS. 6A-7 below). For reception, the circuit 432 is operable to combine the weighted signals prior to outputting them on signal 405.
In an example implementation, the phase and/or amplitude coefficients may be controlled/provided by the digital circuitry 408 via signal 416. The phase and amplitude coefficients may be adjusted dynamically. That is, the coefficients may be adjusted while maintaining one or more active backhaul links. For example, the phase and amplitude coefficients may be adjusted in real time to compensate for twist and sway as it is occurring.
In an example implementation, the phase and/or amplitude beamforming coefficients may be controlled based on data retrieved from a local and/or networked database. Such data may include, for example, data indicating geographical locations of one or more other microwave backhaul transceivers with which the transceiver 120 may desire to establish a microwave backhaul link. Such data may, for example, be used in combination with the transceiver's own location for determining a direction and distance to the other transceiver.
The implementation of circuitry 302 shown in FIG. 4A may be realized on any combination of one or more semiconductor (e.g., Silicon, GaAs) dies and/or one or more printed circuit board. For example, each front-end circuit 402 _nmay comprise one or more first semiconductor dies located as close as possible to (e.g., a few centimeters from) its respective antenna element 306 _N, the circuits 404 and 406 may comprise one or more second semiconductor dies on the same PCB as the first die(s), the circuits 408 and 440 may reside on one or more third semiconductor dies on the same PCB, and the sensor(s) 414 may be discrete components connected to the PCB via wires or wirelessly.
FIG. 4B depicts a second example implementation of the circuitry 302. In this example implementation, the application of beamforming amplitude and phase coefficients is performed in the digital domain in digital circuitry 408. That is, in addition to other functions performed by digital circuitry 408 (such as those described above), the digital circuitry may also perform phase and amplitude weighting and combining of the signals 413 ₁-413 ₈.
Each of the circuits 450 ₁-450 ₈is operable to perform digital-to-analog conversion (when used for transmission) and/or analog-to-digital conversion (when used for reception). In this regard, for reception, the signals 413 ₁-413 ₈are the result of digitization of the signals 403 ₁-403 ₈output by the front-ends 402 ₁-402 ₈. For transmission, the signals 413 ₁-413 ₈are the result of digital circuitry 408 performing phase and amplitude weighting and combining of one or more digital baseband signals (the weighting and combining may be as described in FIG. 5B, for example).
The implementation of circuitry 302 shown in FIG. 4B may be realized on any combination of one or more semiconductor (e.g., Silicon, GaAs) dies and/or one or more printed circuit board. For example, each pair of 402 _nand 450 _nmay comprise an instance of a first semiconductor die and may be located as close as possible to (e.g., a few centimeters from) its respect antenna element 306 _n, the digital circuitry 408 may comprise an instance of a second semiconductor die on the same PCB as the first dies, and the sensor(s) 414 may be discrete components connected to the PCB via wires or wirelessly.
Referring now to FIG. 5A, there is shown an example implementation of the circuit 232 that supports spatial routing of a full-duplex microwave backhaul link. In the example implementation shown, the signals 403 ₁-403 ₄correspond to a received signal having a first polarization (e.g., horizontal) and the signals 403 ₅-403 ₈correspond to a signal to be transmitted with a second polarization (e.g., vertical).
In the receive direction, each of the signals 403 ₁-403 ₄has been received via a respective one of antenna elements 306 ₁-306 ₄, and had its phase shifted, during downconversion by a respective one of mixers 402 ₁-402 ₄, by a respective phase coefficient of a selected first set of coefficients. In circuit 232, the amplitude of each of signals 403 ₁-403 ₄is scaled by a respective amplitude coefficient of the selected first set of coefficients. The weighted signals are summed resulting in signal 405. The signal 405 thus corresponds to a received signal using a radiation pattern corresponding to the selected first set of phase and amplitude coefficients.
In the transmit direction, the signal 441 is split into four signals, each of which has its amplitude scaled by a respective amplitude coefficient of a selected second set of coefficients. The result of the amplitude scaling is signals 403 ₅-403 ₈. The signals 403 ₅-403 ₈are conveyed to front-ends 402 ₅-402 ₈where, during upconversion to microwave frequency, each is phase shifted by a respective phase coefficient of the selected second set of coefficients. The upconverted signals are then conveyed, via feed lines 304 ₅-304 ₈, to antenna elements 306 ₁-306 ₄for transmission.
For both transmitting and receiving with the same link partner on the same frequency, the first set of phase and amplitude coefficients is the same as second set of phase and amplitude coefficients. This may be achieved by storing a single set of coefficients and providing the same set to both scaling circuits 502 ₁-502 ₄and 502 ₅-502 ₈.
For transmitting to a first link partner while receiving from a second link partner on the same frequency, the first set of phase and amplitude coefficients is the different than the second set of phase and amplitude coefficients. This may be achieved by storing two sets of coefficients and providing the first set to circuits 502 ₁-502 ₄and the second set to circuits 502 ₅-502 ₈. This enables independently adjusting the two sets of coefficients which corresponds to independently steering the transmit and receive radiation patterns (e.g., for steering the transmit radiation pattern to track misalignment with a first link partner to which the transceiver transmits and for steering the radiation pattern to track misalignment with a second link partner from which the transceiver receives).
Referring now to FIG. 5B, there is shown an example implementation digital circuitry that supports spatial routing of a full-duplex microwave backhaul link. In the example implementation shown, the signals 413 ₁-413 ₄correspond to a received signal having a first polarization (e.g., horizontal) and the signals 413 ₅-413 ₈correspond to a signal to be transmitted with a second polarization (e.g., vertical).
In the receive direction, each of the signals 413 ₁-413 ₄has been received via a respective one of antenna elements 306 ₁-306 ₄, downconverted by a respective one of mixers 402 ₁-402 ₄, and digitized by a respective one of circuits 450 ₁-4504. The circuits 504 ₁-504 ₄scale the amplitudes of the signals 403 ₁-403 ₄by respective amplitude coefficients of a selected first set of coefficients. The circuits 504 ₁-504 ₄also phase shift the signals 403 ₁-403 ₄by respective phase coefficients of the selected first set of coefficients. The resulting phase-shifted and amplitude-scaled signals are then combined to generate signal 508. The signal 508 thus corresponds to a received signal using a radiation pattern corresponding to the selected first set of phase and amplitude coefficients.
In the transmit direction, the signal 510 is split into four signals. Each of the circuits 504 ₅-504 ₈scales a respective one of the signal 413 ₅-413 ₈by a respective amplitude coefficient of a selected second set of coefficients. Each of the circuits 504 ₅-504 ₈shifts a phase of a respective one of the signal 413 ₅-413 ₈by a respective phase coefficient of the selected second set of coefficients. The result of the amplitude scaling is signals 403 ₅-403 ₈. The signals 403 ₅-403 ₈are conveyed to circuits 450 ₅-450 ₈where they are converted to analog signals 403 ₅-403 ₈. The signals 403 ₅-403 ₈are then upconverted by front-ends 402 ₅-402 ₈and then conveyed, via feed lines 304 ₅-304 ₈, to antenna elements 306 ₁-306 ₄for transmission.
For both transmitting and receiving with the same link partner on the same frequency, the first set of phase and amplitude coefficients may be the same as second set of phase and amplitude coefficients. This may be achieved by storing a single set of coefficients and providing the same set to both scaling circuits 504 ₁-504 ₄and 504 ₅-504 ₈.
For transmitting to a first link partner while receiving from a second link partner on the same frequency, the first set of phase and amplitude coefficients may be different than the second set of phase and amplitude coefficients. This may be achieved by storing two sets of coefficients and providing the first set to circuits 504 ₁-504 ₄and the second set to circuits 504 ₅-504 ₈. This enables independently adjusting the two sets of coefficients which corresponds to independently steering the transmit and receive radiation patterns (e.g., for steering the transmit radiation pattern to track misalignment with a first link partner to which the transceiver transmits and for steering the radiation pattern to track misalignment with a second link partner from which the transceiver receives).
Although the example implementations in FIGS. 5A and 5B use different polarizations to enable concurrent transmission and reception on the same frequencies, other implementations may use different frequencies for transmit and receive (where the antenna elements 306 ₁-306 ₄are sufficiently broadband to cover the different frequencies). In such implementations, different sets of coefficients for transmit and receive may be needed to achieve transmit and receive radiation patterns having substantially similar directivity.
FIG. 6A illustrates effects of tower sway (e.g., due to wind) on a microwave backhaul link between link partners. For reference, a coordinate system comprising angles θ and φ is shown, with the angle θ sweeping along the plane of the page and θ sweeping perpendicular to the page. Shown are the transceivers 120 a and 120 b mounted to towers 122 a and 122 b, respectively. The towers 122 a and 122 b and transceivers 120 a and 120 b in their nominal positions are shown by solid lines and result in beams 602 and 604. The sway in the negative θ direction, and the resulting beams 602 ^−θ and 604 ^−θ, are shown by dashed lines. Sway in the positive θ direction, and the resulting beams 602 ^+θ and 604 ^+θ, are shown by dotted lines. The amount of angular deflection of beam 602 between its nominal position and its position shown as 602 ^−θ is indicated by arc 606. The amount of angular deflection of beam 602 between its nominal position and its position shown as 602 ^+θ is indicated by arc 608. The amount of angular deflection of beam 604 between its nominal position and its position shown as 604 ^−θ is indicated by arc 612. The amount of angular deflection of beam 604 between its nominal position and its position shown as 604 ^+θ is indicated by arc 610. In an example implementation, an angular deflection of 1.7° could result in 10 dB of loss for a two meter diameter dish communicating in a frequency band centered around 18 GHz.
In an example implementation, the materials, dimensions, etc., of the towers 122 a and 122 b and transceivers 120 a and 120 b may be chosen based on a maximum amount of sway that is to be tolerated under maximum wind conditions that are to be tolerated (e.g., designed to sway less than 1.7° in winds of 60 mph or less). Similarly, given the known maximum angular deviation, the transceivers 120 a and 120 b may be designed to be capable of compensating for the maximum angular deviations. For example, the number and size of antenna elements 306 and the size of reflectors 116 may be selected for each of the transceivers 120 a and 120 b such that the transceivers 120 a and 120 b are capable of sufficiently steering their respective radiation patterns to maintain at least a threshold SNR (and/or some other metric) even when both beams 602 and 604 are at a maximum deflection (in the +θ direction, for example).
FIG. 6B illustrates effects of tower twist (e.g., due to wind) on a microwave backhaul link between link partners. For reference, a coordinate system comprising angles θ and φ is shown, with the angle φ sweeping along the plane of the page and θ sweeping perpendicular to the page. Shown are the transceivers 120 a and 120 b mounted to towers 122 a and 122 b, respectively. The transceivers 120 a and 120 b in their nominal positions are shown by solid lines and result in beams 602 and 604. Twist in the negative φ direction, and the resulting beams 602 ^−φ and 604 ^−φ, are shown by dashed lines. Twist in the positive φ direction, and the resulting beams 602 ^+φ and 604 ^+φ, are shown by dotted lines. The amount of angular deflection of beam 602 between its nominal position and its position shown as 602 ^−φ is indicated by arc 614. The amount of angular deflection of beam 602 between its nominal position and its position shown as 602 ^+φ is indicated by arc 616. The amount of angular deflection of beam 604 between its nominal position and its position shown as 604 ^−φ is indicated by arc 620. The amount of angular deflection of beam 604 between its nominal position and its position shown as 604 ^+φ is indicated by arc 618. In an example implementation, an angular deflection of 1.7° could result in 10 dB of loss for a two meter diameter dish communicating in a frequency band centered around 18 GHz.
In an example implementation, the materials, dimensions, etc. of the towers 122 a and 122 b and transceivers 120 a and 120 b may be chosen based on a maximum amount of twist that is to be tolerated under maximum wind conditions that are to be tolerated (e.g., designed to twist less than 1.7° in winds of 60 mph or less). Similarly, given the known maximum angular deviation, the transceivers 120 a and 120 b may be designed to be capable of compensating for the maximum angular deviations. For example, the number and size of antenna elements 306 and the size of reflectors 116 may be selected for each of the transceivers 120 a and 120 b such that the transceivers 120 a and 120 b are capable of sufficiently steering their respective radiation patterns to maintain at least a threshold SNR (and/or some other metric) even when both beams 602 and 604 are at a maximum deflection (in the +φ direction, for example).
FIG. 6C illustrates effects of tower sway (e.g., due to wind) on polarization orientation of a microwave backhaul link between link partners. For reference, a coordinate system comprising angle γ is shown, with the angle γ sweeping along the plane of the page. Shown are the transceivers 120 a and 120 b mounted to towers 122 a and 122 b, respectively.
The tower 122 a and transceiver 120 a (comprising 116 a and 114 a) in its nominal positions is shown by solid lines. The nominal horizontal polarization for transceiver 120 a is shown as solid line 656, and the nominal vertical polarization for transceiver 120 a is shown as solid line 654. Sway of the tower 122 a and transceiver 120 a in the positive γ direction is shown as dashed lines (with 122 a ^+γ, 116 a ^+γ, and 114 a ^+γ called out) results in horizontal polarization 656 ^+γ and vertical polarization 654 ^+γ. Sway of the tower 122 a and transceiver 120 a in the negative γ is shown as dotted lines (with 122 a ^−γ, 116 a ^−γ, and 114 a ^−γ called out) and results in horizontal polarization 656 ^−γ and vertical polarization 654 ^−γ. Absent aspects of this disclosure, the angular deviation of the polarization orientations may result in increased cross-polarization interference between a signal being transmitted or received on the vertical polarization and a signal being transmitted or received on the horizontal polarization. In an exemplary implementation, however, the transceivers 120 a may be operable to determine the angular deviation of the polarization orientations and adjust the radiation patterns based on the determined angular deviation and/or implement a cross-polarization interference cancellation process that adapts based on the determined angular deviation.
The tower 122 b and transceiver 120 b (comprising 116 b and 114 b) in its nominal positions is shown by solid lines. The nominal horizontal polarization for transceiver 120 a is shown as solid line 652, and the nominal vertical polarization for transceiver 120 a is shown as solid line 650. Sway of the tower 122 b and transceiver 120 b in the positive γ direction is shown as dashed lines (with 122 b ^+γ, 116 b ^+γ, and 114 b ^+γ called out) and results in horizontal polarization 652 ^+γ and vertical polarization 650 ^+γ. Sway of the tower 122 b and transceiver 120 b in the negative γ is shown as dotted lines (with 122 b ^−γ, 116 b ^−γ, and 114 b ^−γ called out) and results in horizontal polarization 652 ^−γ and vertical polarization 650 ^−γ. In an exemplary implementation, however, the transceiver 120 b may be operable to determine the angular deviation of the polarization orientations and adjust the radiation patterns based on the determined angular deviation and/or implement a cross-polarization interference cancellation process that adapts based on the determined angular deviation.
FIG. 7 is a flowchart illustrating an example process for misalignment compensation in a microwave backhaul transceiver. The process begins with block 702.
In block 702, the microwave backhaul transceiver 120 a is installed on mast 122 a. Installation may comprise initial alignment of the transceiver 120 a within determined tolerances. The initial alignment may, for example, be based on readings of the sensors 414 and/or instruments (levels, compasses, etc.) in use by the installation technician. The initial alignment may, for example, be based on one or more signals to and/or from one or more intended link partners of the transceiver 120 a (e.g., to and/or from transceiver 120 b). Such signals may be, for example, signals specifically generated for alignment (e.g., four signals for monopulse tracking in azimuth and elevation).
The installation may comprise calibrating the sensor(s) 414. For example, after initial alignment, readings form sensor(s) 414 may be monitored over a period of time and then averaged (to compensate for wind, vibrations, etc. during installation) to determine sensor readings that correspond to the initial alignment. The initial alignment may result in an initial set of beamforming coefficients and initial parameters used by the cross-polarization interface cancellation process performed by digital circuitry 408.
In block 704, one or more active microwave backhaul links 118 are established between transceiver 120 a and link partner 120 b. The link may be established using the nominal radiation pattern(s) and cross-polarization interference cancellation parameters determined in block 704. In an example implementation, the transceivers 120 a and 120 b may initially use signaling parameters that enable successfully establishing the link(s) 118 even in the presence of poor signal-to-noise ratio (e.g., due to residual misalignment within the tolerances of the initial alignment). Then, after the SNR improves (e.g., as a result of alignment compensation performed in blocks 706 and 708) the signaling parameters may be changed to improve the performance (e.g., measured in terms of throughput, reliability, and/or the like) of the link(s) 118.
In block 706, the transceiver 120 a determines its own absolute misalignment, absolute misalignment of its link partner(s), and/or misalignment relative to its link partner(s).
In an example implementation, the transceiver 120 a may determine its own absolute misalignment based on, for example, readings output by its sensor(s) 414. Deviations of the sensor readings from the nominal sensor readings determined in block 702 may be interpreted as movement of the transceiver 120 a. The digital circuitry 408 may then translate the deviations of the sensor readings to angular deflection of directivity and/or polarization orientation of the radiation pattern(s) of the transceiver 120 a. The determined angular deflection may then be used by digital circuitry 408 to adjust the beamforming coefficients and/or adjust parameters used by the cross-polarization interference process.
In an example implementation, the transceiver 120 a may determine its own absolute misalignment based on, for example, monopulse tracking of a fixed target (e.g., a target on a building). The digital circuitry 408 may translate the reflections of the monopulse tracking signals to angular deflection of directivity and/or polarization orientation of the radiation pattern(s) of the transceiver 120 a. The angular deflection of antenna directivity and/or polarization orientation may then be used by digital circuitry 408 to adjust the beamforming coefficients and/or adjust parameters used by the cross-polarization interference process.
In an example implementation, the transceiver 120 a may determine relative misalignment between it and one or more link partners based on, for example, monopulse tracking of the link partner(s). The digital circuitry 408 may translate the reflections of the monopulse tracking signals to relative angular deflection of directivity and/or polarization orientation between the radiation patterns of the transceivers 120 a and 120 b. The relative angular deflection may then be used by digital circuitry 408 to adjust the beamforming coefficients and/or adjust parameters used by cross-polarization interference process.
In an example implementation, the transceiver 120 a may determine relative misalignment between it and one or more link partners based on, for example, an amount of cross-polarization interference measured by the digital circuitry 408. For example, an average amount of cross-polarization interference over a time interval of determined length may be at a minimum for optimal alignment and may increase as relative rotational angular deviation increases.
In an example implementation, the transceiver 120 a may determine absolute misalignment of its link partner(s) based on absolute misalignment data (e.g., raw sensor readings, raw monopulse signal reflection levels, values of measured performance metrics, and/or angular deviation in radians or degrees) received from the link partner(s) via the backhaul link(s) 118 (e.g., sent via the backhaul link(s) 118 on a high-reliability control channel that ensures delivery even with very low SNR) and/or via an alternate link (e.g., via a low-latency, low-bandwidth wired link, optical fiber link, and/or wireless link operating at a cellular frequency or other lower-than-microwave frequency that is not as dependent on line-of-sight.) In this regard, the link partner(s) may determine their own misalignment and send the determined misalignment to transceiver 120 a. Similarly, the transceiver 120 a may send its determined misalignment to its link partner(s).
In an example implementation, where each link partner knows its own misalignment, each may attempt to adjust its radiation pattern(s) and/or cross-polarization interference cancellation parameters to compensate for its own misalignment. In another example implementation, where one or both of the link partners only knows relative misalignment, one or more protocols may be implemented to prevent over-compensation. As an example, each link partner may attempt to compensate for only half of the relative misalignment. As another example, it may be predetermined (e.g., during link establishment in block 702) that a particular one of the link partners will attempt to compensate for relative misalignment up to a threshold and the other link partner will attempt to compensate only for relative misalignment above the threshold. As another example, it may be predetermined (e.g., during link establishment in block 702) that a particular one of the link partners will attempt to compensate only for certain types of misalignment (e.g., directional or polarization orientation) and the other link partner will attempt to compensate only for other types of misalignment. As another example, the link partners may coordinate compensation through real-time data delivered over a control channel of the link 118 and/or over an alternate link.
In block 708, the digital circuitry 408 of the transceiver 120 a attempts to compensate for the misalignment determined in block 706.
In an example implementation, where the misalignment is directional, the digital circuitry 408 may adjust beamforming coefficients to steer the radiation pattern in the opposite direction of the misalignment (e.g., if the misalignment is in the +θ and −φ directions, the beamforming coefficients may be adjusted to steer the radiation pattern in the −θ and +φ directions).
In an example implementation, where the misalignment is rotational, the digital circuitry 408 may adjust beamforming coefficients to rotate the polarization orientation of its radiation pattern in the opposite direction of the misalignment (e.g., if the misalignment is in the +γ direction, the beamforming coefficients may be adjusted to rotate the polarization orientation in the −γ).
In an example implementation, where the misalignment is rotational, the digital circuitry 408 may adjust parameters used by the cross-polarization interference cancellation process.
In accordance with an example implementation of this disclosure, a first microwave backhaul transceiver (e.g., 120 a) may comprises an antenna array (e.g., 202) and circuitry (e.g., 302). The circuitry is operable to determine misalignment of the first microwave backhaul transceiver, and electronically adjust a radiation pattern of the antenna array to compensate for the determined misalignment of the microwave backhaul transceiver. The circuitry may be operable to perform the adjustment of the radiation pattern in real time to compensate for effects of wind on the microwave backhaul transceiver. The circuitry may be operable to detect movement of the microwave backhaul transceiver, and translate the detected movement into angular misalignment of the radiation pattern of the antenna array. The circuitry may comprise one or both of: an accelerometer and a gyroscope, and may be operable to perform the detection of the movement based on readings from one or both of the accelerometer and the gyroscope. The adjustment of the radiation pattern of the antenna array may comprise an adjustment of a polarization orientation (e.g., measured as an angle γ in FIG. 6C) of the antenna array. The circuitry may be operable to perform monopulse tracking for the determination of the misalignment. The circuitry may be operable to concurrently receive a first signal having a first polarization and a second signal having a second polarization. The circuitry may be operable to perform a cross-polarization interference cancellation process for mitigating the impact of interference between the first signal and the second signal. The circuitry may be operable to adjust parameters used by the cross-polarization interference cancellation process based on the detected misalignment of the first microwave backhaul transceiver. The circuitry may be operable to concurrently transmit a first signal having a first polarization and receive a second signal having a second polarization. The circuitry may be operable to perform a cross-polarization interference cancellation process for mitigating the impact of interference between the first signal and the second signal. The circuitry may be operable to adjust parameters used by the cross-polarization interference cancellation process based on the detected misalignment of the first microwave backhaul transceiver. The circuitry may be operable to establish a microwave backhaul link with a second microwave backhaul transceiver. The circuitry may be operable to receive, from the second microwave backhaul transceiver, data indicating misalignment of the second microwave backhaul transceiver, and adjust the radiation pattern of the antenna array based on the data. The circuitry may be operable to track a position of the second microwave backhaul transceiver using monopulse tracking, and adjust the radiation pattern of the antenna array based on the tracked position of the second microwave backhaul transceiver.
The present method and/or system may be realized in hardware, software, or a combination of hardware and software. The present methods and/or systems may be realized in a centralized fashion in at least one computing system, or in a distributed fashion where different elements are spread across several interconnected computing systems. Any kind of computing system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computing system with a program or other code that, when being loaded and executed, controls the computing system such that it carries out the methods described herein. Another typical implementation may comprise an application specific integrated circuit or chip. Some implementations may comprise a non-transitory machine-readable (e.g., computer readable) medium (e.g., FLASH drive, optical disk, magnetic storage disk, or the like) having stored thereon one or more lines of code executable by a machine, thereby causing the machine to perform processes as described herein.
While the present method and/or system has been described with reference to certain implementations, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present method and/or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, it is intended that the present method and/or system not be limited to the particular implementations disclosed, but that the present method and/or system will include all implementations falling within the scope of the appended claims.

Claims

What is claimed is:

1. A system comprising:

a first microwave backhaul transceiver that comprises an antenna array and circuitry operable to:

determine misalignment of said first microwave backhaul transceiver; and

electronically adjust a radiation pattern of said antenna array to compensate for said determined misalignment of said microwave backhaul transceiver.

2. The system of claim 1, wherein said circuitry is operable to perform said adjustment of said radiation pattern in real time to compensate for effects of wind on said microwave backhaul transceiver.

3. The system of claim 1, wherein said circuitry is operable to:

detect movement of said microwave backhaul transceiver; and

translate said detected movement into angular misalignment of said radiation pattern of said antenna array.

4. The system of claim 3, wherein:

said circuitry comprises one or both of: an accelerometer and a gyroscope;

said circuitry is operable to perform said detection of said movement based on readings from one or both of said accelerometer and said gyroscope.

5. The system of claim 1, wherein said adjustment of said radiation pattern of said antenna array comprises an adjustment of a polarization orientation of said antenna array.

6. The system of claim 1, wherein said circuitry is operable to perform monopulse tracking for said determination of said misalignment.

7. The system of claim 1, wherein said circuitry is operable to:

concurrently receive a first signal having a first polarization and a second signal having a second polarization;

perform a cross-polarization interference cancellation process for mitigating the impact of interference between said first signal and said second signal;

adjust parameters used by said cross-polarization interference cancellation process based on said detected misalignment of said first microwave backhaul transceiver.

8. The system of claim 1, wherein said circuitry is operable to:

concurrently transmit a first signal having a first polarization and receive a second signal having a second polarization;

9. The system of claim 1, wherein said circuitry is operable to:

establish a microwave backhaul link with a second microwave backhaul transceiver;

receive, from said second microwave backhaul transceiver, data indicating misalignment of said second microwave backhaul transceiver; and

adjust said radiation pattern of said antenna array based on said data.

10. The system of claim 1, wherein said circuitry is operable to:

track a position of said second microwave backhaul transceiver using monopulse tracking; and

adjust said radiation pattern of said antenna array based on said tracked position of said second microwave backhaul transceiver.

11. A method comprising:

in a first microwave backhaul transceiver that comprises an antenna array:

determining misalignment of said first microwave backhaul transceiver; and

adjusting a radiation pattern of said antenna array to compensate for said determined misalignment of said microwave backhaul transceiver.

12. The method of claim 11, comprising adjusting said radiation pattern in real time to compensate for effects of wind on said microwave backhaul transceiver.

13. The method of claim 11, comprising:

detecting movement of said microwave backhaul transceiver; and

translating said detected movement into angular misalignment of said radiation pattern of said antenna array.

14. The method of claim 13, comprising detecting said movement based on readings from one or both of an accelerometer and a gyroscope of said first microwave backhaul transceiver.

15. The method of claim 11, wherein said adjusting of said radiation pattern of said antenna array comprises adjusting a polarization orientation of said antenna array.

16. The method of claim 1, comprising performing monopulse tracking for said determining of said misalignment.

17. The method of claim 1, comprising:

concurrently receiving a first signal having a first polarization and a second signal having a second polarization;

performing a cross-polarization interference cancellation process for mitigating the impact of interference between said first signal and said second signal;

adjusting parameters used by said cross-polarization interference cancellation process based on said detected misalignment of said first microwave backhaul transceiver.

18. The method of claim 11, comprising:

concurrently transmitting a first signal having a first polarization and receive a second signal having a second polarization;

adjusting parameters use by said cross-polarization interference cancellation process based on said detected misalignment of said first microwave backhaul transceiver.

19. The method of claim 1, comprising:

establishing a microwave backhaul link with a second microwave backhaul transceiver;

receiving, from said second microwave backhaul transceiver, data indicating misalignment of said second microwave backhaul transceiver; and

adjusting said radiation pattern of said antenna array based on said data.

20. The method of claim 11, comprising:

tracking a position of said second microwave backhaul transceiver using monopulse tracking; and

adjusting said radiation pattern of said antenna array based on said tracked position of said second microwave backhaul transceiver.