OFDMA Hybrid Beamforming Channel Estimation via Orthogonal Training
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Solution Overview
Problem
In mmWave wireless communication systems, the increased propagation loss and hardware constraints limit the effectiveness of beamforming, making it challenging to achieve efficient user or system throughput and Signal to Noise Ratio (SNR) through conventional MIMO schemes, especially in OFDMA-based systems with hybrid beamforming architectures.
Innovation Solution
A beam training approach is developed for OFDMA-based hybrid beamforming (HBF) systems, involving the generation of orthogonal training beams for both transmitter and receiver, simultaneous transmission and reception of OFDMA preambles, and channel estimation based on feedback results to adjust analog beamformers and combiners, optimizing channel response and beamforming performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If analog beamforming is used in mmWave systems, then propagation loss is mitigated and beamforming gain is increased, but hardware complexity and cost increase due to requirements for multiple RF chains and analog/RF devices
Solution Approach 1:
The patent segments the beamforming function into digital beamforming (performed by microprocessors in the digital domain) and analog beamforming (performed by low-cost phase shifters in the analog domain). This segmentation allows the system to achieve beamforming gain through digital processing while using simpler, lower-cost hardware components for the analog portion, thereby mitigating propagation loss without proportionally increasing hardware complexity and cost.
2Reliability
If digital beamforming is used to increase beamforming gain, then SNR and reliability are improved, but implementation complexity and cost increase due to requirements for expensive DAC/ADC and multiple RF paths
Solution Approach 1:
The patent substitutes expensive analog hardware components (multiple RF chains, DACs, ADCs) with digital processing operations. By performing beamforming functions through digital signal processing in the baseband unit, the system achieves the required SNR and reliability improvements while avoiding the need for complex and costly analog hardware infrastructure.
3Ease of manufacture
If pure analog beamforming is used, then hardware cost is reduced, but effectiveness in efficient resource use and MIMO scheme performance is limited
Solution Approach 1:
The patent merges digital beamforming and analog beamforming into a hybrid architecture. The digital beamforming component enables efficient resource utilization and MIMO scheme performance through software-based processing, while the analog beamforming component maintains hardware cost-effectiveness. This combination allows the system to achieve high system throughput and effective resource use without the full hardware cost of pure digital beamforming.
Data Source
AI summary
The method is for channel estimation with transmitter (Tx) and receiver (Rx) beam training in an OFDMA HBF system wherein the transmitter and receiver communicate over a channel and each include a plurality of Radio Frequency (RF) chains and an antenna array of antenna elements corresponding to each RF chain, and wherein the transmitter includes an analog beamformer and the receiver includes an analog combiner. The method includes generating a set of orthogonal Tx training beams for the transmitter based upon a number of antenna elements in the transmitter antenna array, and generating a set of orthogonal Rx training beams for the receiver based upon a number of antenna elements in the receiver antenna array. The method includes probing the channel by simultaneously transmitting OFDMA preambles with each RF chain using a different one of the orthogonal Tx training beams and receiving the OFDMA preambles with each of the orthogonal Rx training beams in a scheduling sequence that includes a pairing of each orthogonal Tx training beam with each orthogonal Rx training beam, and performing channel estimation based upon probing feedback results including a channel response between different pairs of the orthogonal Tx training beams and the orthogonal Rx training beams.