Full duplex backhaul radio with transmit beamforming

• US 9,408,215 B2
• Filed: 01/05/2016
• Issued: 08/02/2016
• Est. Priority Date: 08/17/2011
• Status: Active Grant

• Current Assignee: COMS IP Holdings LLC
• Original Assignee: CBF Networks, Inc. (COMSovereign Holding Corp.)
• Inventors: Negus, Kevin J.
• Primary Examiner(s): Phillips, Hassan
• Assistant Examiner(s): Sharma, Gautam
• Application Number:
  US14/988,578
• Publication Number:
  US 20160135192A1
• Time in Patent Office: 210 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 25/005 providing two patterns of opposite direction; back to back antennas H01Q25/004 takes precedence
• CPC Class Codes: H01Q 5/50 Feeding or matching arrangements for broad-band or multi-band operation
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 2001/0408 with power amplifiers
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/2678 using cyclostationarities, e.g. cyclic prefix or postfix
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04W 24/02 : Arrangements for optimising operational condition
• CPC Class Codes: H04W 52/52 : using AGC [Automatic Gain Control] circuits or amplifiers
• CPC Class Codes: H04W 72/04 : Wireless resource allocation
• CPC Class Codes: H04W 72/0453 : Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 76/27 : Transitions between radio resource control [RRC] states
• CPC Class Codes: H04W 84/12 : WLAN [Wireless Local Area Networks]

Abstract

A intelligent backhaul radio is disclosed that is compact, light and low power for street level mounting, operates at 100 Mb/s or higher at ranges of 300 m or longer in obstructed LOS conditions with low latencies of 5 ms or less, can support PTP and PMP topologies, uses radio spectrum resources efficiently and does not require precise physical antenna alignment.

Claims

1. A backhaul radio for exchanging one or more data interface streams with one or more other backhaul radios, said backhaul radio comprising:

a plurality of receive radio frequency (RF) chains, wherein each receive RF chain is configured to convert from a respective one of a plurality of receive RF signals within a receive frequency band to a respective one of a plurality of receive chain output signals;

one or more modulator cores, wherein each modulator core is configured to modulate one or more transmit data interface streams to produce one or more of a plurality of transmit symbol streams, and wherein each transmit symbol stream comprises at least a plurality of blocks of symbols;

a plurality of transmit radio frequency (RF) chains, wherein each transmit RF chain is configured to convert from a respective one of a plurality of transmit chain input signals to a respective one of a plurality of transmit RF signals within a transmit frequency band;

a non-frequency selective transmit path channel multiplexer, interposed between the one or more modulator cores and at least the plurality of transmit RF chains, wherein the non-frequency selective transmit path channel multiplexer is configured to generate the plurality of transmit chain input signals from at least the plurality of transmit symbol streams;

a plurality of directive gain antenna elements, wherein each directive gain antenna element is configured to operate over at least both of the transmit frequency band and the receive frequency band; and

a plurality of duplexer filters, wherein each duplexer filter comprises at least a receive band-select filter configured to selectively pass RF signals within the receive frequency band and a transmit band-select filter configured to selectively pass RF signals within the transmit frequency band, wherein each duplexer filter is couplable or coupled to at least one of the plurality of directive gain antenna elements, wherein the receive band-select filter of each duplexer filter is couplable or coupled to at least one of the plurality of receive RF chains, and wherein the transmit band-select filter of each duplexer filter is couplable or coupled to at least one of the plurality of transmit RF chains;

wherein a first number of the plurality of transmit chain input signals exceeds a second number of the plurality of transmit symbol streams; and

wherein the non-frequency selective transmit path channel multiplexer is configured to apply respective sets of stream-specific and chain-specific transmit beamforming weights to at least one or more blocks of the plurality of blocks of symbols from the plurality of transmit symbol streams when generating a respective one of the plurality of transmit chain input signals, and wherein a particular one of said stream-specific and chain-specific transmit beamforming weights is invariant with respect to a relative symbol position within said at least one or more blocks of the plurality of blocks of symbols.

2. The backhaul radio of claim 1, further comprising:

one or more demodulator cores, wherein each demodulator core is configured to demodulate one or more of a plurality of receive symbol streams to produce one or more receive data interface streams; and

a frequency selective receive path channel multiplexer, interposed between the one or more demodulator cores and at least the plurality of receive RF chains, wherein the frequency selective receive path channel multiplexer is configured to generate the plurality of receive symbol streams from at least the plurality of receive chain output signals.

3. The backhaul radio of claim 2, wherein each one of the one or more demodulator cores comprises at least a decoder and a soft decision symbol demapper;

and wherein each one of the plurality of receive RF chains comprises at least a vector demodulator and two analog to digital converters that are configured to produce the respective one of the plurality of receive chain output signals, each said respective one of the plurality of receive chain output signals comprised of digital baseband quadrature signals.

4. The backhaul radio of claim 1, wherein each one of the one or more modulator cores comprises at least an encoder and a symbol mapper;

and wherein each one of the plurality of transmit RF chains comprises at least a vector modulator and two digital to analog converters that are configured to produce the respective one of the plurality of transmit RF signals, each said respective one of the plurality of transmit chain input signals comprised of digital baseband quadrature signals.

5. The backhaul radio of claim 2, wherein each one of the one or more demodulator cores comprises at least one of a descrambler or a deinterleaver;

and wherein each one of the one or more modulator cores comprises at least one of a scrambler or an interleaver.

6. The backhaul radio of claim 1, further comprising:

one or more selectable RF connections that are configured to selectively couple certain of the plurality of directive gain antenna elements to either or both of certain of the plurality of receive RF chains or certain of the plurality of transmit RF chains;

wherein the number of directive gain antenna elements that are configured to be selectively coupled to receive RF chains exceeds the number of receive RF chains that are configured to accept receive RF signals from the one or more selectable RF connections;

or

wherein the number of directive gain antenna elements that are configured to be selectively coupled to transmit RF chains exceeds the number of transmit RF chains that are configured to provide transmit RF signals to the one or more selectable RF connections.

7. The backhaul radio of claim 6, wherein at least one of the one or more selectable RF connections comprises at least one RF switch.

8. The backhaul radio of claim 6, wherein the set of receive RF chains that is configured to accept receive RF signals from the one or more selectable RF connections is divided between a first subset that is configured to accept receive RF signals from directive gain antenna elements with a first polarization and a second subset that is configured to accept receive RF signals from directive gain antenna elements with a second polarization;

or wherein the set of transmit RF chains that is configured to provide transmit RF signals to the one or more selectable RF connections is divided between a third subset that is configured to provide transmit RF signals to directive gain antenna elements with a first polarization and a fourth subset that is configured to provide transmit RF signals to directive gain antenna elements with a second polarization.

9. The backhaul radio of claim 1, wherein the directive gain antenna elements are arranged on a plurality of facets with one or more directive gain antenna elements per facet, and wherein each facet is oriented at a different azimuth angle relative to at least one other facet.

10. The backhaul radio of claim 1, further comprising:

a plurality of power amplifiers, wherein each power amplifier is configured to amplify at least one of the transmit RF signals, and wherein each power amplifier is couplable or coupled to at least one of the plurality of transmit RF chains and to at least one transmit band-select filter of the plurality of duplexer filters; and

a plurality of low noise amplifiers, wherein each low noise amplifier is configured to amplify at least one of the receive RF signals, and wherein each low noise amplifier is couplable or coupled to at least one of the plurality of receive RF chains and to at least one receive band-select filter of the plurality of duplexer filters.

11. The backhaul radio of claim 1, wherein both of the transmit frequency band and the receive frequency band are within a frequency range of between 2 GHz and 6 GHz.

12. The backhaul radio of claim 1, wherein both of the transmit frequency band and the receive frequency band are within a frequency range of above 10 GHz.

13. The backhaul radio of claim 2, wherein the frequency selective receive path channel multiplexer comprises at least one of a Space Division Multiple Access (SDMA) combiner or equalizer, a maximal ratio combining (MRC) combiner or equalizer, a minimum mean squared error (MMSE) combiner or equalizer, an Eigen Beam Forming (EBF) combiner or equalizer, a receive beam forming (BF) combiner or equalizer, a Zero Forcing (ZF) combiner or equalizer, a channel estimator, a Maximal Likelihood (DL) detector, an Interference Canceller (IC), a VBLAST combiner or equalizer, a Discrete Fourier Transformer (DFT), a Fast Fourier Transformer (FFT), or an Inverse Fast Fourier Transformer (IFFT).

14. The backhaul radio of claim 2, wherein the frequency selective receive path channel multiplexer comprises:

a plurality of cyclic prefix removers, wherein each cyclic prefix remover is configured to discard a fraction of an overall number of samples within one or more blocks of a plurality of blocks of samples from a respective one of the plurality of receive chain output signals to produce a respective cyclic prefix removed one or more blocks of samples, said fraction corresponding to a known cyclic prefix length for a plurality of second transmit symbol streams expected to be comprised within the plurality of receive chain output signals;

a plurality of respective complex Discrete Fourier Transformers coupled to each respective cyclic prefix remover, wherein each complex Discrete Fourier Transformer is configured to decompose the respective cyclic prefix removed one or more blocks of samples into a respective set of receive chain frequency domain subchannel samples; and

a plurality of receive channel equalizers coupled to the plurality of respective complex Discrete Fourier Transformers, wherein each receive channel equalizer is configured to produce a set of channel-equalized frequency domain estimates representative of a respective one of the plurality of second transmit symbol streams by applying respective stream-specific and chain-specific receive weights to the respective sets of receive chain frequency domain subchannel samples;

wherein said respective stream-specific and chain-specific receive weights applied to the respective sets of receive chain frequency domain subchannel samples vary with relative frequency domain subchannel position within such sets.

15. The backhaul radio of claim 14, further comprising:

a channel equalizer coefficients generator, wherein the channel equalizer coefficients generator is configured to determine the respective stream-specific and chain-specific receive weights based at least upon comparison of certain sets of receive chain frequency domain subchannel samples with certain expected blocks of known frequency domain subchannel samples expected to be present at certain times within the plurality of receive chain output signals.

16. The backhaul radio of claim 14, further comprising:

a plurality of complex Inverse Discrete Fourier Transformers, wherein each complex Inverse Discrete Fourier Transformer is configured to compose a respective one of the plurality of receive symbol streams from respective sets of channel-equalized frequency domain estimates representative of the respective one of the plurality of second transmit symbol streams.

17. The backhaul radio of claim 16, wherein each of the plurality of complex Inverse Discrete Fourier Transformers is implemented by a structure executing a complex Inverse Fast Fourier Transform (IFFT), and wherein each of the plurality of complex Discrete Fourier Transformers is implemented by a structure executing a complex Fast Fourier Transform (FFT).

18. The backhaul radio of claim 14, wherein each of the plurality of receive channel equalizers comprises a number of complex multipliers corresponding to a number of the plurality of receive chain output signals, and a combiner.

19. The backhaul radio of claim 14, wherein a receive path modulation format is based upon Orthogonal Frequency Division Multiplexing (OFDM).

20. The backhaul radio of claim 16, wherein a receive path modulation format is based upon Single-Carrier Frequency Domain Equalization (SC-FDE).

21. The backhaul radio of claim 1, wherein the non-frequency selective transmit path channel multiplexer comprises:

a plurality of cyclic prefix adders, wherein each cyclic prefix adder is configured to add a fraction of an overall number of samples within one or more blocks of a plurality of blocks of samples corresponding to a respective one of the plurality of transmit chain input signals, said fraction corresponding to a pre-determined cyclic prefix length; and

a plurality of transmit channel equalizers, wherein each transmit channel equalizer is configured to produce one or more blocks of non-frequency selective, channel-equalized samples corresponding to a respective one of the plurality of transmit chain input signals by applying respective sets of the stream-specific and chain-specific transmit beamforming weights to corresponding blocks of symbols from the plurality of transmit symbol streams;

wherein a number of the plurality of cyclic prefix adders and of the plurality of transmit channel equalizers corresponds to the first number.

22. The backhaul radio of claim 21, further comprising:

a plurality of complex Inverse Discrete Fourier Transformers, wherein each complex Inverse Discrete Fourier Transformer is configured to compose a respective one of the plurality of transmit chain input signals from respective ones of non-frequency selective, channel-equalized samples corresponding to respective ones of the plurality of transmit chain input signals.

23. The backhaul radio of claim 21, wherein an output from each respective one of the plurality of transmit channel equalizers is coupled to an input of a respective one of the plurality of cyclic prefix adders.

24. The backhaul radio of claim 21, wherein each of the plurality of transmit channel equalizers comprises a number of complex multipliers corresponding to the second number, and a combiner.

25. The backhaul radio of claim 21, wherein the stream-specific and chain-specific transmit beamforming weights are determined at a receiver comprised within at least one of the backhaul radio or the one or more other backhaul radios.

26. The backhaul radio of claim 25, wherein the receiver that determines the stream-specific and chain-specific transmit beamforming weights further comprises:

a channel equalizer coefficients generator, wherein the channel equalizer coefficients generator is configured to determine the respective stream-specific and chain-specific transmit beamforming weights based at least upon comparison of certain signals at the receiver with certain expected signals expected to be present at certain times.

27. The backhaul radio of claim 21, wherein the stream-specific and chain-specific transmit beamforming weights are determined in order to improve either a signal to interference and noise ratio (SINR) or a signal to noise ratio (SNR).

28. The backhaul radio of claim 24, wherein each of the stream-specific and chain-specific transmit beamforming weights comprises at least a real branch component and an imaginary branch component.

29. The backhaul radio of claim 21, wherein each of the stream-specific and chain-specific transmit beamforming weights comprises at least one of an amplitude component or a phase component.

30. The backhaul radio of claim 21, wherein a transmit path modulation format is based upon Single-Carrier Frequency Domain Equalization (SC-FDE).

31. The backhaul radio of claim 22, wherein a transmit path modulation format is based upon Orthogonal Frequency Division Multiplexing (OFDM).