Mixed Analog Digital Beamforming Weights for 60 GHz Link Budget
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Solution Overview
Problem
The high path loss and low output power of CMOS power amplifiers at 60 GHz in wireless networks result in a poor link budget, making it difficult to support high data rates with omnidirectional antennas, and existing beamforming solutions are impractical due to high cost and power consumption, especially in frequency selective channels.
Innovation Solution
A method for computing jointly transmit-receive mixed analog and digital beamforming weights to maximize the average received signal-to-noise ratio (SNR) using a joint TX-RX mixed analog/digital beamforming algorithm, which reduces hardware complexity by applying linear transformations in the analog RF domain and optimizing beamforming weights through Singular Value Decomposition (SVD).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital beamforming is used at 60 GHz with more than eight antenna elements, then beamforming performance is improved, but hardware cost and power consumption increase significantly due to ADC and DAC requirements
Solution Approach 1:
The patent segments the beamforming process into two distinct domains: analog beamforming for spatial processing in the RF domain, and digital beamforming for signal processing in the baseband domain. This segmentation allows the system to use fewer ADC/DAC chains by performing initial beamforming in the analog domain, thereby reducing hardware complexity while maintaining beamforming performance at 60 GHz
Solution Approach 2:
The patent introduces an intermediate analog beamforming stage that acts as a mediator between the antenna array and the digital processing chain. This intermediate analog processing reduces the dimensionality of signals before digitization, serving as an intermediary that bridges the gap between full digital beamforming (high performance, high complexity) and simple analog beamforming (low complexity, reduced performance)
2Reliability
If digital beamforming is used at 60 GHz with more than eight antenna elements, then beamforming performance is improved, but power consumption increases due to ADC and DAC running at several gigasamples per second
Solution Approach 1:
The patent segments the beamforming process into analog and digital domains, performing computationally intensive spatial processing in the analog domain before digitization. This segmentation reduces the sampling rate and data volume requiring digital processing, thereby significantly reducing power consumption of ADC/DAC while preserving beamforming performance
Solution Approach 2:
The patent applies partial digital beamforming instead of full digital beamforming. By performing only essential digital processing after analog pre-processing, the system achieves adequate beamforming performance with reduced computational load and lower power consumption compared to complete digital beamforming at high sampling rates
3Device complexity
If antenna selection is used to reduce the number of AFE chains, then hardware complexity is reduced, but beamforming gain is lost and performance degrades in fading channels
Solution Approach 1:
The patent merges analog beamforming and digital beamforming into a hybrid architecture where both techniques work together synergistically. The analog beamforming provides spatial processing and beamforming gain, while digital beamforming handles signal processing, combining the advantages of both approaches to maintain performance in fading channels while reducing hardware complexity compared to full digital beamforming
4Reliability
If antenna subarray formation is used to exploit signals on all antennas, then beamforming gain is achieved, but the solution is limited to frequency flat channels while 60 GHz systems experience frequency selective fading
Solution Approach 1:
The patent implements a dynamic hybrid beamforming architecture that adapts to frequency selective channels by combining time-domain analog beamforming with frequency-domain digital beamforming. This dynamic approach allows the system to maintain beamforming gain while adapting to frequency selective fading conditions, overcoming the limitation of static antenna subarray formation methods designed for frequency flat channels
Data Source
Figure 1(a)~1(b)
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AI summary
The present invention is related to a method for mixed analog/digital beamforming in a wireless communication system having a plurality of transmit antennas and receive antennas and a plurality of analog front-ends connected to the plurality of transmit and receive antennas, at least two analog front-ends being connected to either the transmit antennas or the receive antennas. The method comprises the steps of determining transmit and receive analog beamforming coefficients and transmit and receive digital beamforming coefficients by - determining information representative of communication channels formed between a transmit antenna and a receive antenna of the plurality of antennas, - defining a set of coefficients representing the transmit analog beamforming coefficients and the receive analog beamforming coefficients, - determining a beamforming cost function using the information and the set of coefficients, the beamforming cost function taking into account the plurality of analog front-ends, - computing an optimized set of coefficients by exploiting the beamforming cost function, the optimized set of coefficients comprising optimized transmit analog beamforming coefficients and optimized receive analog beamforming coefficients - deriving an estimate of the frequency responses of the communication channels using the information determined in the first step - deriving for each communication channel transmit digital beamforming coefficients and receive digital beamforming coefficients using the estimated frequency responses and the optimized transmit and receive analog beamforming coefficients.