POWER AMPLIFIER PROTECTION USING A CYCLIC REDUNDANCY CHECK ON THE DIGITAL TRANSPORT OF DATA
A method of conditioning payload data includes providing a processor and receiving a packet comprising payload data, a first error code, and a second error code. The method also includes computing, using the processor, a first recalculated error code and determining a difference between the first error code and the first recalculated error code. The method further includes modifying the payload data in response to determining the difference.
Latest Dali Systems Co. Ltd. Patents:
- Redundant distributed antenna system (DAS) with failover capability
- Method and system for aligning signals widely spaced in frequency for wideband digital predistortion in wireless communication systems
- Redundancy in a public safety distributed antenna system
- Wide bandwidth digital predistortion system with reduced sampling rate
- System and method for performance optimization in and through a distributed antenna system
This application is a continuation of U.S. patent application Ser. No. 14/095,706, filed on Dec. 3, 2013; which claims priority to U.S. Provisional Patent Application No. 61/733,324, filed on Dec. 4, 2012. Each of these references is hereby incorporated by reference in its entirety for all purposes.
BACKGROUND OF THE INVENTIONWireless and mobile network operators face the continuing challenge of building networks that effectively manage high data-traffic growth rates. Mobility and an increased level of multimedia content for end users requires end-to-end network adaptations that support both new services and the increased demand for broadband and flat-rate Internet access. One of the most difficult challenges faced by network operators is maximizing the capacity of their DAS networks while ensuring cost-effective DAS deployments and at the same time providing a very high degree of DAS remote unit availability.
Despite the progress made in DAS networks, there is a need in the art for improved methods and systems related to DAS networks.
SUMMARY OF THE INVENTIONThe present invention generally relates to communication systems using complex modulation techniques. More specially, the present invention relates to power amplifier systems that contain a microprocessor or other digital components, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC). Power amplifiers are very sensitive to rapid changes in the signals passing through them. Unplugging the communications media (Fiber Optic Cable, Ethernet, Microwave Link, etc.) or abruptly cutting the cable can create unwanted spikes in the complex signals. These spikes can be delivered to the power amplifier and subsequently damage the internal devices. Embodiments of the present invention provide an efficient and effective method of protecting power amplifiers in a remote unit to which data has been transported over a digital link from a host unit to the remote unit.
Embodiments of the present invention provide systems and techniques that are based on performing a Cyclic Redundancy Check (CRC) on the transmitted data at the Host unit and then again on the received data at the remote unit, which contains the power amplifier. Any discrepancy between the two CRC codes will imply that the data has been corrupted with errors.
As described herein, embodiments of the present invention provide protection for power amplifiers utilized in transmission systems. By modifying payload data (e.g., reducing the amplitude of I/Q payload data) in response to the detection of errors or corruption of the payload data, embodiments of the present invention provide protection for power amplifiers not available using conventional techniques.
The present invention is applicable to any communication system with a power amplifier. A communication link can be established between a local host unit and a remote unit that contains a power amplifier. A Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC) that incorporates a processor, such as a Power PC or Microblaze, controls the data flow to and from the Remote Unit.
A distributed antenna system (DAS) provides an efficient means of utilization of base station resources. The base station or base stations associated with a DAS can be located in a central location and/or facility commonly known as a base station hotel. The DAS network comprises one or more digital access units (DAUs) that function as the interface between the base stations and the digital remote units (DRUs). The DAUs can be collocated with the base stations. The DRUs can be daisy chained together and/or placed in a star configuration and provide coverage for a given geographical area. The DRUs are typically connected with the DAUs by employing a high-speed optical fiber link. This approach facilitates transport of the RF signals from the base stations to a remote location or area served by the DRUs.
An embodiment shown in
As illustrated in
Although embodiments of the present invention utilize the high byte and the low byte from the payload data, this is not required by the present invention and other portions of the payload can be utilized to generate the CRC data. Moreover, although a high byte and a low byte are illustrated in
In addition, the De-Framer 601 uses the payload I & Q data (payloadDRU) received at the DRU and generates a high side byte (H-byteDRU) and a low side byte (L-byteDRU). Referring to
If an error had occurred during the transportation of the payload I/Q data then the CRC16H 602 and/or CRC16L 603 could be used to detect the error. However, there is a finite possibility that an error may have occurred in the regenerated CRC16HDRU and CRC16LDRU data. Under this condition, the payload I/Q data may be deemed to be correct despite the occurrence of an error. This scenario may give rise to allowing an error in the payload I/Q data to be transmitted to the power amplifier 318. Large fluctuations in the payload I/Q data have the potential of damaging the power amplifier in the DRU.
In order to further reduce the possibility of an error propagating to the power amplifier, a recalculation of the CRC codes is performed on the received payload I/Q data at CRC16H 602 and CRC16L 603. Referring to
On the other hand, if there is a disagreement between the received and recalculated values, then this implies that the payload data is corrupted. In this case, the payload I/Q data is all set to zero in some embodiments. In these embodiments, the payload output at 607 will be a null value. Setting the payload data to zero or other suitable small value insures that no large fluctuations occur in the payload I/Q data when an error is detected.
Using the payload, the first error code, and the second error code, a first recalculated error code and a second recalculated error code are computed (712). The first error code is compared to the first recalculated error code (e.g., CRC16 HDRU and CRC16 HH) and the second error code is compared to the second recalculated error code (e.g., CRC16 LDRU and CRC16 LL) (714). If both sets of values are equal, the payload is passed on as the payload output (718). If there is a discrepancy between the sets of values, which indicates corruption of the payload during transmission, then the payload is modified in order to protect the power amplifier (716). In the embodiment illustrated in
Additionally, in addition to abrupt changes in the payload data values, a time average or a moving average of previous payload data values could be stored and then used to modify the payload data when corruption is detected. As will be evident to one of skill in the art, the modification of the payload data can be various ways of altering and/or reducing the amplitude of the I/Q data. As an example, the values can be decreased exponentially over time, averaged with previous data, or the like. For instance, previous data could be retransmitted, with subsequent data reduced in amplitude either instantly, linearly, with an exponential decay (for example, with an exponential decay time constant of a fraction of the length of the payload data), combinations thereof, or the like. Thus, various methods can be used to modify the payload data to produce modified data with an I/Q amplitude less than the previously transmitted payload data.
It should be appreciated that the specific steps illustrated in
It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
Appendix I is a glossary of terms used herein, including acronyms.
APPENDIX I Glossary of Terms
- ACLR Adjacent Channel Leakage Ratio
- ACPR Adjacent Channel Power Ratio
- ADC Analog to Digital Converter
- AQDM Analog Quadrature Demodulator
- AQM Analog Quadrature Modulator
- AQDMC Analog Quadrature Demodulator Corrector
- AQMC Analog Quadrature Modulator Corrector
- BPF Bandpass Filter
- CDMA Code Division Multiple Access
- CFR Crest Factor Reduction
- DAC Digital to Analog Converter
- DET Detector
- DHMPA Digital Hybrid Mode Power Amplifier
- DDC Digital Down Converter
- DNC Down Converter
- DPA Doherty Power Amplifier
- DQDM Digital Quadrature Demodulator
- DQM Digital Quadrature Modulator
- DSP Digital Signal Processing
- DUC Digital Up Converter
- EER Envelope Elimination and Restoration
- EF Envelope Following
- ET Envelope Tracking
- EVM Error Vector Magnitude
- FFLPA Feedforward Linear Power Amplifier
- FIR Finite Impulse Response
- FPGA Field-Programmable Gate Array
- GSM Global System for Mobile communications
- I-Q In-phase/Quadrature
- IF Intermediate Frequency
- LINC Linear Amplification using Nonlinear Components
- LO Local Oscillator
- LPF Low Pass Filter
- MCPA Multi-Carrier Power Amplifier
- MDS Multi-Directional Search
- OFDM Orthogonal Frequency Division Multiplexing
- PA Power Amplifier
- PAPR Peak-to-Average Power Ratio
- PD Digital Baseband Predistortion
- PLL Phase Locked Loop
- QAM Quadrature Amplitude Modulation
- QPSK Quadrature Phase Shift Keying
- RF Radio Frequency
- RRH Remote Radio Head
- RRU Remote Radio Head Unit
- SAW Surface Acoustic Wave Filter
- UMTS Universal Mobile Telecommunications System
- UPC Up Converter
- WCDMA Wideband Code Division Multiple Access
- WLAN Wireless Local Area Network
Claims
1-16. (canceled)
17. A method for receiving and amplifying a signal, comprising:
- receiving a data frame containing a digital payload of baseband I/Q data;
- detecting errors in the digital payload;
- modifying the digital payload in response to the detected errors;
- converting the digital payload from digital to analog to create an analog payload;
- upconverting the analog payload to create an upconverted analog payload;
- providing the upconverted analog payload to a power amplifier.
18. The method of claim 17 wherein modifying the digital payload in response to the detected errors comprises modifying the digital payload by nulling the digital payload.
19. The method of claim 17 wherein modifying the digital payload in response to the detected errors comprises altering the digital payload by adjusting a gain of the digital payload.
20. The method of claim 17 wherein modifying the digital payload in response to the detected errors comprises attenuating the digital payload to a reduced value.
21. The method of claim 17 wherein modifying the digital payload in response to the detected errors comprises altering the digital payload by altering the amplitude of the baseband I/Q data.
22. The method of claim 17 wherein modifying the digital payload in response to the detected errors comprises maintaining an average of previous digital payload values and modifying the digital payload in response to the average of previous digital payload values.
23. A digital remote unit, comprising:
- an input path operable to receive a data frame containing a digital payload of baseband I/Q data;
- an FPGA loaded with executable code operable to detect errors in the digital payload and modify the digital payload in response to the detected errors;
- a digital-to-analog converter operable to convert the digital payload from digital to analog to create an analog payload;
- an upconverter operable to upconvert the analog payload to create an upconverted analog payload;
- a power amplifier operable to receive and amplify the upconverted analog payload.
24. The remote unit of claim 23 wherein the FPGA is loaded with executable code operable to modify the digital payload by nulling the digital payload.
25. The remote unit of claim 23 wherein the FPGA is loaded with executable code operable to alter the digital payload by adjusting a gain of the digital payload.
26. The remote unit of claim 23 wherein the FPGA is loaded with executable code operable to attenuate the digital payload to a reduced value.
27. The remote unit of claim 23 wherein the FPGA is loaded with executable code operable to alter the amplitude of the baseband I/Q data.
28. The remote unit of claim 23 wherein the FPGA is loaded with executable code operable to modify the digital payload in response to the average of previous digital payload values.
29. A system for transporting data, comprising:
- a host unit;
- a plurality of remote units, each remote unit communicatively coupled to the at least one host unit;
- wherein the host unit is operable to send and receive digital signals from each of the plurality of remote units;
- wherein each of the plurality of remote units includes an error detecting function and an algorithm operable to alter a payload signal when errors are detected.
30. The system of claim 29 wherein the algorithm operable to alter a payload signal when errors are detected is operable to null the digital payload.
31. The system of claim 29 wherein the algorithm operable to alter a payload signal when errors are detected is operable to adjust a gain of the digital payload.
32. The system of claim 29 wherein the algorithm operable to alter a payload signal when errors are detected is operable to attenuate the digital payload to a reduced value.
33. The system of claim 29 wherein the payload signal comprises baseband I/Q data and the algorithm operable to alter a payload signal when errors are detected is operable to alter the amplitude of the baseband I/Q data.
34. The system of claim 29 wherein the algorithm operable to alter a payload signal when errors are detected is operable to modify the digital payload in response to the average of previous digital payload values.
35. The system of claim 29 wherein the plurality of remote units are connected in a daisy chain configuration.
36. The system of claim 29 wherein the host unit is operable to receive, from a signal source, signals representative of wireless RF communications.
Type: Application
Filed: Dec 15, 2016
Publication Date: Aug 10, 2017
Applicant: Dali Systems Co. Ltd. (Grand Cayman)
Inventors: Qianqi Zhuang (Richmond), Shawn Patrick Stapleton (Vancouver)
Application Number: 15/380,686