OFDM Reference Symbol Transmission for Millimeter Wave Beamforming
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Solution Overview
Problem
Current millimeter wave communication systems face challenges in commercial mobile communication due to high cost, complexity, and power consumption, particularly in RFIC design, which limits their applicability for longer distances and larger coverage areas.
Innovation Solution
The proposed solution involves a base station and subscriber station equipped with multiple antenna arrays and RF processing chains, utilizing beamforming techniques to transmit and receive spatial beams, and employing OFDM symbols with reduced duration and cyclic prefix to efficiently transmit reference symbols for channel state information estimation, optimizing the use of millimeter wave spectrum for improved data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If millimeter wave communication systems use more RF processing chains to support more spatial beams, then beamforming capability and data transfer rates are improved, but device complexity, cost, and power consumption increase
Solution Approach 1:
The patent divides the transmission of N spatial beams across NRF RF chains into multiple OFDM symbol periods. Each OFDM symbol carries reference symbols for a subset of spatial beams, segmenting the overall transmission task into manageable time-based segments that reduce per-symbol complexity while maintaining total beam coverage.
Solution Approach 2:
The patent employs periodic transmission of reference symbols across different OFDM symbols, where each symbol period transmits reference symbols for specific spatial beams in a repeating pattern. This periodic action allows the system to cover all N spatial beams over multiple periods while using only NRF RF chains, reducing hardware requirements.
2Productivity
If the duration of OFDM symbols and cyclic prefix is reduced to efficiently transmit reference symbols, then transmission efficiency and data transfer rates are improved, but measurement precision for channel state information may deteriorate
Solution Approach 1:
The patent transmits reference symbols in advance within reduced-duration OFDM symbols before actual data transmission begins. This preliminary transmission of known reference patterns allows the receiver to pre-estimate channel state information, compensating for the shorter symbol duration and maintaining measurement precision while improving overall transmission efficiency.
Data Source
AI summary
A base station is capable of communicating with a plurality of subscriber stations using a beamforming scheme that varies beams over different time instances. The base station includes a plurality of antenna arrays configured to transmit N spatial beams and carry a reference symbols corresponding to specific spatial beams. The base station also includes NRF number of radio frequency (RF) processing chains coupled to respective ones of the plurality of antenna arrays, wherein N>>NRF. The subscriber station includes MRF processing receive paths configured to receive M number of beams from the base station.