Short Pilot Symbols for Virtual MIMO Channel Estimation
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Solution Overview
Problem
The high cost and complexity of implementing multiple antennas and transmission paths in user elements for MIMO-based communications, making it economically unfeasible for consumers to access the full benefits of MIMO communications, despite existing infrastructure capable of facilitating such communications at base stations.
Innovation Solution
A pilot scheme for frequency division multiple access (FDM) communication systems that allows for MIMO communications between base stations and user elements with or without multiple antennas, using short pilot symbols and orthogonal sub-carriers to maintain orthogonality and efficiency, enabling virtual MIMO capabilities even with single-antenna user elements by encoding and modulating pilot information onto common sub-carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple antennas and transmission paths are implemented in user elements for MIMO communications, then channel capacity and data rates are improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent uses pilot symbols as copies of reference signals to enable channel estimation at the receiver. By transmitting known pilot sequences from each antenna and correlating received signals with these pilots, the system can estimate channel responses without requiring the receiver to have multiple antennas, thus achieving MIMO capacity with single-antenna user elements
Solution Approach 2:
The patent changes the parameter of pilot symbol length from full-length to short-length, and uses orthogonal codes with different lengths (e.g., length-4 and length-8 orthogonal codes) to maintain orthogonality while reducing overhead. This parameter optimization enables efficient channel estimation for MIMO systems with reduced complexity
2Productivity
If multiple antennas and transmission paths are implemented in user elements for MIMO communications, then channel capacity and data rates are improved, but cost increases significantly
Solution Approach 1:
The patent employs pilot symbols as reference copies that enable channel estimation without requiring expensive multiple antenna hardware at the user element. The base station transmits pilot symbols through multiple antennas, and single-antenna user elements can estimate the channel by correlating received pilots with known sequences, achieving MIMO capacity at lower cost
Solution Approach 2:
The patent creates a universal pilot scheme that works for both single-antenna and multiple-antenna user elements. The same pilot structure and orthogonal coding approach serves different device configurations, allowing cost-effective deployment where user elements can participate in MIMO communications regardless of their antenna count
3Productivity
If short pilot symbols are used with reduced Fourier transform length, then pilot overhead is reduced and efficiency is improved, but measurement precision for channel estimation may be affected
Solution Approach 1:
The patent merges multiple pilot symbols with the same orthogonal code across different time instances to form a combined pilot sequence. By correlating received signals with this merged sequence, the effective processing length is increased, maintaining channel estimation precision while using shorter individual pilot symbols that reduce overhead
Solution Approach 2:
The patent transitions from time-domain short pilots to frequency-domain processing by using orthogonal codes of different lengths (e.g., length-4 and length-8). This dimensional transformation allows short time-domain pilots to provide sufficient frequency-domain resolution for accurate channel estimation through proper correlation processing
Data Source
AI summary
The present invention employs a pilot scheme for frequency division multiple access (FDM) communication systems, such as single carrier FDM communication systems. A given transmit time interval will include numerous traffic symbols and two or more short pilot symbols, which are spaced apart from one another by at least one traffic symbol and will have a Fourier transform length that is less than the Fourier transform length of any given traffic symbol. Multiple transmitters will generate pilot information and modulate the pilot information onto sub-carriers of the short pilot symbols in an orthogonal manner. Each transmitter may use different sub-carriers within the time and frequency domain, which is encompassed by the short pilot symbols within the transmit time interval. Alternatively, each transmitter may uniquely encode the pilot information using a unique code division multiplexed code and modulate the encoded pilot information onto common sub-carriers of the short pilot symbols.