Dynamic Reference Signal Subframe Allocation for Interference Mitigation
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Solution Overview
Problem
The existing 3GPP LTE wireless communication systems face challenges in minimizing the overhead of downlink reference signal (DLRS) transmission and mitigating multiple access interference (MAI) between adjacent Node-Bs, which degrades performance.
Innovation Solution
Each four-antenna Node-B dynamically adjusts the number and location of subframes for transmitting reference symbols based on changing network conditions, using predefined patterns to optimize DLRS transmission and reduce MAI by varying the frequency and location of subframes in response to the number of 4-TX terminals and interference levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downlink reference signal transmission is performed frequently and in fixed locations, then channel estimation accuracy is improved, but overhead increases and multiple access interference from adjacent Node-Bs worsens
Solution Approach 1:
The patent applies dynamics by making the reference signal transmission pattern configurable and adaptable. Different subframe patterns (first pattern with reference signals in all subframes, second pattern with reference signals in every other subframe, third pattern with reference signals in specific subframes) can be selected based on network conditions, terminal mobility, and interference levels, transforming a static transmission scheme into a dynamic one that optimizes between accuracy and interference
Solution Approach 2:
The patent changes the parameter of reference signal transmission density and location by introducing multiple configurable patterns. The network can adjust which subframes contain reference signals (all subframes, every other subframe, or specific subframes based on pattern configuration), thereby changing the temporal distribution parameter to balance channel estimation accuracy against overhead and interference
2Productivity
If downlink reference signal overhead is minimized, then spectral efficiency is improved, but channel estimation accuracy and interference mitigation capability deteriorate
Solution Approach 1:
The patent applies partial action by transmitting reference signals only when necessary. Instead of continuous transmission in all subframes, the system can select patterns where reference signals are transmitted in every other subframe or only in specific subframes, providing sufficient channel estimation capability while reducing overall overhead and improving spectral efficiency for data transmission
Solution Approach 2:
The patent implements periodic action through the second subframe pattern where reference signals are transmitted in every other subframe. This periodic transmission provides regular channel estimation opportunities while reducing the total number of reference signal transmissions compared to continuous transmission, thereby improving spectral efficiency
3Ease of operation
If all Node-Bs transmit reference signals in the same subframes, then terminal implementation is simplified, but multiple access interference from adjacent Node-Bs increases
Solution Approach 1:
The patent applies asymmetry by allowing different Node-Bs to use different reference signal transmission patterns. Adjacent Node-Bs can be configured with different patterns (e.g., one uses pattern 1 with all subframes, another uses pattern 2 with every other subframe, or different third patterns), creating asymmetric transmission schedules that reduce simultaneous transmissions and thereby reduce multiple access interference
Data Source
AI summary
A method and system optimizes the transmission of a downlink reference signal (DLRS) in a wireless communication system that uses orthogonal division multiple access (OFDMA) for the downlink. Each Node-B (base station) is capable of transmitting the DLRS reference symbols in different subframes of the OFDM radio frame and changing both the number and location of the subframes in response to changing network conditions. The network conditions include the number of terminals being served by the Node-B and multiple access interference (MAI) from adjacent Node-Bs.