Reference Signal Sequence Grouping for LTE Inter-Cell Interference
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Solution Overview
Problem
In the 3GPP LTE system, interference from neighboring cells due to reference signals of different lengths transmitted over the same frequency band is significant, leading to cross-correlation issues that affect signal distinction and synchronization.
Innovation Solution
A method for generating reference signal sequences by grouping sequences of varying lengths corresponding to multiples of a resource block size, using Zadoff-Chu sequences with cyclic shifts, to minimize interference by ensuring high cross-correlation values within each group, allowing for the use of variable length sequences as reference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reference signals of different lengths are transmitted in multi-cell environments, then signal flexibility and resource block adaptation are improved, but inter-cell interference increases due to insufficient cross-correlation distinction
Solution Approach 1:
The patent segments reference signals into groups based on their cross-correlation properties. Sequences are divided into multiple groups where each group contains sequences with similar cross-correlation characteristics. This segmentation allows the system to select appropriate sequence groups for different cells, thereby managing inter-cell interference while maintaining signal flexibility for various resource block configurations.
Solution Approach 2:
The patent changes the parameter of sequence length to create reference signals adapted to different resource block sizes. By varying the sequence length parameter while maintaining high cross-correlation within groups, the system achieves flexibility in signal adaptation without sacrificing interference management capabilities.
2Productivity
If sequences of variable lengths are used for different resource block sizes, then resource utilization efficiency is improved, but sequence design complexity increases
Solution Approach 1:
The patent creates a universal sequence design framework where a finite set of base sequences can serve multiple functions. These sequences are designed to work across different resource block sizes and cell configurations through cyclic shifts and group selections. This multi-functionality allows the same sequence set to adapt to various scenarios, improving resource utilization while avoiding the need for completely different sequence designs for each case.
Solution Approach 2:
The patent manages sequence design complexity by systematically varying parameters such as sequence length, cyclic shift values, and group indices. Instead of designing entirely new sequences for each scenario, the system reuses base sequences with modified parameters, thereby achieving resource block adaptation with controlled design complexity.
3Measurement precision
If high cross-correlation sequences are grouped together, then signal distinction capability is improved, but the number of available sequences for multiplexing decreases
Solution Approach 1:
The patent segments the sequence space into multiple groups, where each group contains sequences with high cross-correlation properties. By distributing different groups to different cells, the system maintains signal distinction capability within each cell while providing multiple groups overall to support sequence multiplexing across the network. This segmentation resolves the contradiction by organizing sequences hierarchically.
Solution Approach 2:
The patent introduces additional dimensions for sequence identification beyond just the sequence content itself. By using group indices and cyclic shift values as additional dimensions, the system can distinguish between sequences even when they belong to the same high cross-correlation group. This dimensional expansion increases the effective number of available sequences for multiplexing while maintaining signal distinction capability.
Data Source
AI summary
Method for generating reference signal sequence using grouping is explained. In this method, base sequences are grouped such that each group contains at least one base sequence of each length, so UE(s) can use various length sequences as a reference signal. And in this method, inter cell interference caused by using various length sequence as a reference signal sequence can be minimized by grouping sequences having the high cross correlation relation.