Cell-Specific Reference Signal Format Switching for Overhead Reduction
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Solution Overview
Problem
Existing wireless networks face challenges in accurately transmitting cell-specific reference signals across multiple antenna ports due to overhead restrictions, leading to less accurate channel quality measurements and potential inappropriate demodulation codes in wireless devices.
Innovation Solution
The system dynamically switches the format of cell-specific reference signals between antenna ports, either periodically or based on measured coherence, to ensure sufficient resource elements are used for transmission, balancing the density of reference signals and avoiding interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are transmitted using a dense format in every subframe for all antenna ports, then measurement precision is improved, but overhead restrictions are violated and device complexity increases
Solution Approach 1:
The patent applies periodic action by transmitting reference signals in a dense format only in specific subframes (e.g., every other subframe or based on coherence time conditions) rather than in every subframe. This periodic transmission pattern maintains adequate measurement precision while reducing the overall overhead and device complexity associated with continuous dense reference signal transmission across all antenna ports.
Solution Approach 2:
The patent implements dynamics by adaptively switching between dense and sparse reference signal formats based on measured channel coherence time. When coherence time is high, sparse formats are used to reduce overhead; when coherence time is low, dense formats are used to maintain measurement precision. This dynamic adaptation resolves the contradiction by making the reference signal density flexible rather than fixed.
2Device complexity
If reference signals are transmitted using a sparse format to reduce overhead, then device complexity is reduced, but measurement precision deteriorates leading to inappropriate demodulation codes
Solution Approach 1:
The patent uses dynamics by continuously monitoring channel coherence time and adaptively adjusting the reference signal format density. When the channel exhibits high coherence (stable conditions), sparse formats suffice for maintaining acceptable measurement precision while reducing overhead. When coherence decreases (rapidly changing conditions), the system switches to dense formats to ensure accurate measurements, thus dynamically resolving the contradiction between overhead reduction and measurement precision.
Solution Approach 2:
The patent applies parameter changes by modifying the density parameter of reference signals based on channel coherence time measurements. The system changes the reference signal format parameter (from sparse to dense or vice versa) according to measured channel conditions, ensuring that measurement precision is maintained only when necessary while reducing overhead during stable channel conditions.
3Adaptability or versatility
If different antenna ports use different reference signal formats simultaneously, then adaptability is improved, but interference increases and reliability deteriorates
Solution Approach 1:
The patent applies periodic action by coordinating the transmission of different reference signal formats across antenna ports in a time-division manner. Different antenna ports transmit dense and sparse formats in alternating subframes or according to a coordinated pattern, which maintains adaptability while reducing simultaneous interference and improving the reliability of channel state information through periodic full-density measurements.
Data Source
AI summary
Transmitting downlink reference signals includes transmitting a first plurality of subframes comprising a first reference signal associated with a first antenna port, the first reference signal having a first format within the first plurality of subframes, transmitting a second plurality of subframes comprising a second reference signal associated with a second antenna port, the second reference signal having a second format within the second plurality of subframes, and switching a format of each of the first and second reference signals, such that a third plurality of subframes is transmitted with the first reference signal in the second format, and a fourth plurality of subframes is transmitted with the second reference signal in the first format.