Flexible Reference Signal Structure for Wireless Systems
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently transmitting reference signals due to limited radio resources and rapid channel condition changes, leading to inaccurate channel estimation and increased inter-cell interference.
Innovation Solution
A method for designing a flexible reference signal structure using time-frequency resources, allowing for arbitrary user accommodation and improved channel estimation by allocating radio resources effectively in both downlink and uplink directions, employing techniques such as DFT-based spreading codes and resource splitting/hopping to mitigate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed spreading code is used in time-frequency domain for reference signal transmission, then orthogonality between reference signals is maintained, but channel estimation accuracy deteriorates when channel conditions change rapidly and inter-cell interference increases
Solution Approach 1:
The patent applies dynamics by making the reference signal structure adaptable to changing channel conditions. The system dynamically selects between different reference signal configurations (e.g., normal CP vs. extended CP, different cyclic shifts) based on current channel characteristics, allowing the reference signal to flexibly respond to rapid channel variations while maintaining orthogonality through controlled resource allocation.
Solution Approach 2:
The patent changes key parameters of the reference signal including cyclic shift values, resource element allocations, and spreading code configurations. By adjusting these parameters based on channel conditions and interference levels, the system maintains orthogonality while adapting to different scenarios, thereby improving channel estimation accuracy without sacrificing the orthogonality benefit.
2Adaptability or versatility
If the number of orthogonal codes is increased to accommodate more users, then user accommodation capability is improved, but radio resource consumption increases and system capacity is limited
Solution Approach 1:
The patent extends the orthogonal code space by utilizing multiple dimensions: different cyclic shifts in the time domain, different resource element allocations in the frequency domain, and different reference signal configurations. This multi-dimensional approach effectively increases the number of available orthogonal codes without proportionally increasing radio resource consumption, as the same physical resources are reused across different dimensions.
Solution Approach 2:
The patent segments the reference signal resources into multiple orthogonal domains including time (different slots), frequency (different subcarriers), and code (different cyclic shifts). This segmentation allows multiple users to be accommodated by allocating different segments to different users, effectively increasing user capacity while maintaining efficient resource utilization through structured orthogonal allocation.
3Reliability
If reference signals are allocated flexibly to adapt to channel conditions, then channel estimation reliability is improved, but orthogonality between reference signals may be impaired causing increased interference
Solution Approach 1:
The patent applies local quality by allocating reference signals with different properties to different users based on their specific channel conditions and interference environments. Users experiencing high interference may be allocated reference signals with larger cyclic shifts or different resource patterns, while users in better conditions use more resource-efficient configurations. This localized optimization maintains orthogonality while adapting to local channel characteristics.
Data Source
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AI summary
A method of transmitting a reference signal in a wireless communication system includes generating a frequency-domain reference signal by performing discrete Fourier transform (DFT) on a time-domain reference signal, generating a transmit signal by performing inverse fast Fourier transform (IFFT) on the frequency-domain reference signal and transmitting the transmit signal.