OFDM Pilot Code Pattern for Base Station Identification
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Solution Overview
Problem
Conventional OFDMA-CDM communication systems face challenges in identifying a large number of base stations due to limited pilot patterns, which degrades channel estimation performance and increases complexity in multiplexing data and pilot signals.
Innovation Solution
The system employs a pilot code pattern generator to produce a set of spreading codes based on a base station's ID, spreading pilot symbols with a higher signal level than data symbols, and using these codes to identify base stations through a combination of pilot hopping patterns and orthogonal codes across time-frequency cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional pilot patterns are used for base station identification, then the system can identify base stations, but the number of identifiable base stations is limited due to limited pilot patterns
Solution Approach 1:
The patent segments the pilot identification mechanism into two independent components: pilot hopping patterns (time-domain) and orthogonal spreading codes (code-domain). This segmentation allows the system to identify base stations using combinations of these components, exponentially increasing the number of identifiable base stations without proportionally increasing overall system complexity.
Solution Approach 2:
The patent transitions from a single-dimension pilot pattern approach to a multi-dimensional identification scheme by introducing both time-domain hopping patterns and code-domain orthogonal codes. This dimensional expansion allows the system to differentiate base stations across multiple independent dimensions, significantly increasing identification capacity.
2Measurement precision
If pilot channel signals are transmitted for channel estimation, then channel estimation performance improves, but system complexity increases due to multiplexing requirements
Solution Approach 1:
The patent separates pilot signal processing from data signal processing by assigning dedicated orthogonal spreading codes to pilot channels. This segmentation allows independent optimization of channel estimation without interfering with data transmission, simplifying the overall multiplexing structure while maintaining estimation precision.
Solution Approach 2:
The patent changes the signal parameter domain by applying orthogonal codes in the code-domain rather than relying solely on time-frequency multiplexing. This parameter transformation simplifies the multiplexing process while preserving channel estimation performance, as orthogonal codes provide automatic interference rejection.
3Ease of manufacture
If spreading codes are applied to both pilot and data signals, then transmitter implementation is simplified, but signal level management becomes more complex
Solution Approach 1:
The patent applies different signal levels locally: pilot signals are transmitted at a higher signal level than data signals. This local quality differentiation ensures that pilot signals used for channel estimation have sufficient strength and reliability, while data signals can be transmitted at lower levels, simplifying overall power management.
Solution Approach 2:
The patent achieves equipotentiality in the code-domain by applying the same spreading code structure to both pilot and data signals. This unified approach simplifies transmitter implementation, as the same spreading code generation and application logic can be used for both signal types, reducing implementation complexity despite different signal levels.
Data Source
AI summary
Provided are an apparatus and method for transmitting/receiving a pilot code pattern used to identify a base station. In the base station, a pilot code pattern determiner determines a code set that includes a number of spreading codes based on a specific ID of the base station. A first spreader spreads a pilot symbol mapped onto an FC with a corresponding spreading code according to the determined code set, and controls gain so as to transmit the pilot symbol at a higher signal level than data. A second spreader spreads data symbols mapped onto the FC with spreading codes of the code set except for the spreading code used for the pilot spreading. A mapper groups a spread signal from the first spreader and spread signals from the second spreader on a TFC basis, and outputs signals that constitute each TFC to points of sub-carriers. An IFFT unit performs an IFFT operation on signals output from the mapper. Because the pilot as well as the data is spread, it is easy to implement the base station. Also, it is possible to identify base stations according to the pilot spreading codes as well as a pilot hopping pattern.