High efficiency, remotely reconfigurable remote radio head unit system and method for wireless communications

• US 8,824,595 B2
• Filed: 09/06/2013
• Issued: 09/02/2014
• Est. Priority Date: 12/21/2009
• Status: Active Grant

• Current Assignee: Dali Systems Co., Ltd.
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Kim, Wan-Jong, Cho, Kyoung-Joon, Stapleton, Shawn Patrick, Xiao, Ying
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US14/020,425
• Publication Number:
  US 20140079153A1
• Time in Patent Office: 361 Days
• US Class Current: 375/297
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H04B 1/0064 with separate antennas for the more than one band H04B1/0053 takes precedence
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 84/047 using dedicated repeater stations
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/085 Access point devices with remote components
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A remote radio head unit (RRU) system is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier inside the RRU. The power amplifier characteristics such as variation of linearity and asymmetric distortion of the amplifier output signal are monitored by a wideband feedback path and controlled by the adaptation algorithm in a digital module. Therefore, embodiments of the present invention can compensate for the nonlinearities as well as memory effects of the power amplifier systems and also improve performance, in terms of power added efficiency, adjacent channel leakage ratio and peak-to-average power ratio. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers, multi-frequency bands and multi-channels. Consequentially, the remote radio head system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems.

Claims

1. A multiple-channel remote radio head unit for wireless communications comprising:

a plurality of power amplifiers, each receiving an input signal and each providing as an output an amplified representation of the received input signal;

a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers;

digital logic for processing signals, wherein the at least two power amplifiers are coupled to the digital logic using a bias control path, wherein the processing includes;

determining, for a power amplifier of the plurality of power amplifiers, a value for a power-related variable associated with the power amplifier; and

determining a predistortion to apply based on the determined value; and

a feedback switch for selecting one of the feedback signals for connection to the digital logic to enable the digital logic to generate a predistortion compensation signal based on the determined predistortion.

2. The multiple-channel remote radio head unit of claim 1, wherein the power-related variable includes a peak-to-average power ratio.

3. The multiple-channel remote radio head unit of claim 1, wherein the power-related variable includes an average power.

4. The multiple-channel remote radio head unit of claim 1, wherein the power-related variable includes an error vector magnitude or adjacent channel power ratio.

5. The multiple-channel remote radio head unit of claim 1, wherein the power-related variable is one indicative of a memory effect.

6. The multiple-channel remote radio head unit of claim 1, wherein the digital logic determines, for each power amplifier of the plurality of power amplifiers, a value for the power-related variable associated with the power amplifier, and wherein the predistortion is determined based on the determined values.

7. The multiple-channel remote radio head unit of claim 1, further comprising an RF input and a baseband input coupled to the digital logic.

8. The multiple-channel remote radio head unit of claim 1, wherein the digital logic further applies crest factor reduction to one of the input signals.

9. A method comprising:

receiving, at each of a plurality of power amplifiers, an input signal;

amplifying, at each of a plurality of power amplifiers, the input signal to produce an output that includes an amplified representation of the received input signal;

determining, by digital logic and for a power amplifier of the plurality of power amplifiers, a value of a power-related variable associated with the power amplifier, wherein the at least two power amplifiers are coupled to the digital logic using a bias control path;

determining, by the digital logic a predistortion to apply based on the determined value;

providing a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers; and

selecting one of the feedback signals for connection to the digital logic to enable generation of a predistortion compensation signal based on the determined predistortion.

10. The method of claim 9, wherein the power characteristic includes a peak-to-average power ratio.

11. The method of claim 9, wherein the power characteristic includes an average power.

12. The method of claim 9, wherein the power characteristic includes an error vector magnitude or adjacent channel power ratio.

13. The method of claim 9, wherein the power characteristic is one indicative of a memory effect.

14. The method of claim 9, further comprising:

determining, for each power amplifier of the plurality of power amplifiers, a value for the power-related variable associated with the power amplifier, wherein the predistortion is determined based on the determined values.

15. The method of claim 9, further comprising:

applying crest factor reduction to one of the input signals.

16. A multiple-channel remote radio head unit for wireless communications comprising:

an optical to electrical interface to receive an optical signal;

a plurality of power amplifiers, each receiving an input signal corresponding to the optical signal and each providing as an output an amplified representation of the received input signal;

a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers;

digital logic for processing signals, wherein the digital logic is coupled to the optical to electrical interface, and wherein the processing includes;

determining, for a power amplifier of the plurality of power amplifiers, a value for a power-related variable associated with the power amplifier; and

determining a predistortion to apply based on the determined value; and

a feedback switch for selecting one of the feedback signals for connection to the digital logic to enable the digital logic to generate a predistortion compensation signal based on the determined predistortion.

17. The multiple-channel remote radio head unit of claim 16, wherein the power-related variable includes a peak-to-average power ratio.

18. The multiple-channel remote radio head unit of claim 16, wherein the power-related variable includes an average power.

19. The multiple-channel remote radio head unit of claim 16, wherein the power-related variable includes an error vector magnitude or adjacent channel power ratio.

20. The multiple-channel remote radio head unit of claim 16, wherein the power-related variable is one indicative of a memory effect.

21. The multiple-channel remote radio head unit of claim 16, wherein the digital logic determines, for each power amplifier of the plurality of power amplifiers, a value for the power-related variable associated with the power amplifier, and wherein the predistortion is determined based on the determined values.

22. The multiple-channel remote radio head unit of claim 16, further comprising a duplexer coupled to the at least two power amplifiers.

23. The multiple-channel remote radio head unit of claim 16, wherein the digital logic further applies crest factor reduction to one of the input signals.

24. A method comprising:

receiving, at an optical to electrical interface, an optical signal;

receiving, at each of a plurality of power amplifiers, an input signal corresponding to the optical signal;

amplifying, at each of a plurality of power amplifiers, the input signal to produce an output that includes an amplified representation of the received input signal;

determining, by digital logic and for a power amplifier of the plurality of power amplifiers, a value of a power-related variable associated with the power amplifier, wherein the digital logic is coupled to the optical to electrical interface;

determining, by the digital logic, a predistortion to apply based on the determined value;

providing a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers; and

selecting one of the feedback signals for connection to the digital logic to enable generation of a predistortion compensation signal based on the determined predistortion.

25. The method of claim 24, wherein the power characteristic includes a peak-to-average power ratio.

26. The method of claim 24, wherein the power characteristic includes an average power.

27. The method of claim 24, wherein the power characteristic includes an error vector magnitude or adjacent channel power ratio.

28. The method of claim 24, wherein the power characteristic is one indicative of a memory effect.

29. The method of claim 24, further comprising:

determining, for each power amplifier of the plurality of power amplifiers, a value for the power-related variable associated with the power amplifier, wherein the predistortion is determined based on the determined values.

30. The method of claim 24, further comprising:

applying crest factor reduction to one of the input signals.