Hybrid Beamforming for Millimeter Wave Random Access
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Solution Overview
Problem
In wireless communication systems, especially in millimeter wave bands, existing MIMO systems face challenges with synchronization, cost, and operation complexity due to the need for a large number of RF chains, which is exacerbated by path attenuation and the limitations of digital beamforming.
Innovation Solution
A hybrid beamforming method is employed, where a user equipment (UE) transmits uplink data using an optimal sub-array beam or analog beam, combining digital and analog beamforming to efficiently transmit random access responses and uplink data, allowing for beam combining and resource optimization by dividing frequency bands and using chase-combining or incremental redundancy schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of RF chains are used in digital beamforming to overcome path attenuation in millimeter wave bands, then communication reliability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent segments the beamforming function into two parts: digital beamforming for a limited number of RF chains and analog beamforming for the remaining antenna elements. This segmentation allows the system to achieve high reliability through digital processing while avoiding the complexity of having digital chains for all antennas, thus resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent merges digital beamforming and analog beamforming into a hybrid beamforming system. The digital beamforming handles a subset of antenna elements with full digital processing capability, while analog beamforming handles the remaining elements with lower complexity hardware. This combination achieves the reliability benefits of digital beamforming without requiring a large number of RF chains, thus reducing device complexity.
2Productivity
If the number of digital paths is increased to obtain greater diversity gain and multiplexing gain, then communication capacity is improved, but synchronization difficulty and operation complexity increase
Solution Approach 1:
The patent segments the MIMO communication function across different domains: spatial domain (multiple antenna elements), frequency domain (OFDM subcarriers), and time domain (multiple transmission layers). By distributing the communication capacity across these segmented domains rather than relying solely on increasing digital paths, the system achieves high communication capacity while maintaining manageable operation complexity.
Solution Approach 2:
The patent transitions from relying primarily on the digital domain (single dimension) to utilizing multiple dimensions including spatial (antenna elements), frequency (OFDM), and time (layers). This dimensional expansion allows the system to achieve greater communication capacity through hybrid beamforming and multi-layer transmission without proportionally increasing digital path complexity.
3Reliability
If random access response is transmitted separately for each beam to ensure reliable reception, then communication reliability is improved, but signaling overhead increases
Solution Approach 1:
The patent merges multiple random access responses intended for different UEs into a single combined transmission. By applying digital beamforming to steer the combined signal toward multiple target UEs simultaneously, the system ensures reliable reception for each UE while transmitting only one random access response message, thus dramatically reducing signaling overhead while maintaining communication reliability.
Solution Approach 2:
The patent makes a single random access response message serve multiple functions by using digital beamforming to direct the same message to multiple different UEs. This multi-functionality allows one message to fulfill the random access response requirement for multiple UEs simultaneously, reducing the quantity of signaling while ensuring each receiving UE gets reliable communication.
Data Source
AI summary
Provided is a method of transmitting, by a first user equipment, uplink data in a wireless communication. The method includes transmitting a random access preamble to a base station through an optimal beam of the first user equipment, receiving a first random access response and a second random access response wherein the first random access response is received together with downlink data of a second user equipment through an optimal beam of the second user equipment at a first point of time and the second random access response is received together with downlink data of a third user equipment through an optimal beam of the third user equipment at a second point of time, decoding a message which is generated by combining the first random access response with the second random access response, and transmitting the uplink data to the base station based on scheduling information included in the message.