DMRS Sequence Optimization for NB-IoT Inter-Cell Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication systems face challenges in efficiently configuring and transmitting demodulation reference signals (DMRS) in Narrowband IoT (NB-IoT) systems, particularly in single tone and multi-tone transmissions, which affect uplink channel estimation and inter-cell interference.
Innovation Solution
The method involves configuring a narrowband DMRS in the NB-IoT system by generating and mapping DMRS sequences using gold sequences with the lowest cross-correlation value and excluding sequences with high Cubic Metric (CM) values, and mapping DMRS sequences to the time domain for single tone transmission to reduce inter-cell interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DMRS sequences are transmitted in NB-IoT systems using conventional methods, then the system can support basic uplink transmission, but the uplink channel estimation accuracy is insufficient and inter-cell interference is high
Solution Approach 1:
The patent changes the parameters of DMRS sequences by selecting gold sequences with the lowest cross-correlation values and excluding sequences with high Cubic Metric values. This parameter optimization reduces inter-cell interference and improves channel estimation accuracy by ensuring better orthogonality between sequences from different cells.
Solution Approach 2:
The patent maps DMRS sequences to the time domain for single tone transmission instead of using conventional frequency domain mapping. This dimensional change in signal mapping reduces inter-cell interference by exploiting time domain orthogonality and improves channel estimation performance in NB-IoT uplink transmissions.
2Productivity
If multiple DMRS sequences are used in contiguous cells, then the system can support multiple users, but cross-correlation between sequences increases causing interference
Solution Approach 1:
The patent optimizes the selection of gold sequence parameters by choosing sequences with the lowest cross-correlation values. This parameter optimization allows multiple users to be supported while maintaining low interference levels, as the selected sequences have minimal cross-correlation even when transmitted from contiguous cells.
3Adaptability or versatility
If all available sequences are used for DMRS transmission, then the system can provide sequence diversity, but sequences with high Cubic Metric values degrade overall DMRS performance
Solution Approach 1:
The patent extracts and excludes sequences with high Cubic Metric values from the set of available DMRS sequences. This extraction process removes harmful elements that would degrade performance, while retaining sequences with low CM values that provide adequate diversity for supporting multiple users without compromising overall system performance.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
This specification discloses a method for transmitting a demodulation reference signal (DMRS) in a wireless communication system supporting NB (Narrow-Band)-IoT (Internet of Things), the method performed by a User Equipment (UE) including generating a reference signal sequence used for demodulation; mapping the reference signal sequence to at least one symbol; and transmitting the demodulation reference signal (DMRS) to a base station through a single subcarrier in the at least one symbol.