Reference Signal Sequence Grouping for Inter-Cell Interference
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Solution Overview
Problem
The limited number of ZC sequences and the need to reuse sequences with the same sequence number in different cells leads to inter-cell interference and reduced accuracy in channel estimation due to limited transmission power and narrower bandwidths, especially in mobile communication systems.
Innovation Solution
Grouping R×M sequences specified by Zadoff-Chu sequence numbers and cyclic shift sequence numbers into sequence groups based on transmission bandwidths, and assigning these groups to cells to increase the number of available sequences and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ZC sequences are reused in different cells to increase sequence availability, then the number of assignable sequences increases, but inter-cell interference increases and channel estimation accuracy deteriorates
Solution Approach 1:
The invention segments the limited ZC sequences into multiple groups (first group and second group). Cells are divided into different cell groups, with each cell group assigned sequences from a specific group. This segmentation allows sequence reuse across different cell groups while preventing interference within the same cell group, thereby increasing the number of assignable sequences without sacrificing channel estimation accuracy.
2Area of stationary object
If transmission bandwidth is reduced to extend coverage, then coverage area increases, but the number of available ZC sequences decreases
Solution Approach 1:
By segmenting sequences into multiple groups and assigning different groups to different cell groups, the invention effectively multiplies the number of available sequences. This allows narrowband transmission (smaller bandwidth) to extend coverage area while maintaining sufficient sequence diversity through proper group assignment, preventing the degradation of sequence availability that would normally occur with reduced bandwidth.
3Reliability
If cyclic shift amount is increased to accommodate larger delay spread, then robustness to delay spread improves, but the number of usable cyclic shift sequences decreases
Solution Approach 1:
The invention segments sequences into multiple groups where each group can utilize a full set of cyclic shifts. By assigning different sequence groups to different cell groups, the system can afford to use larger cyclic shift amounts (reducing usable cyclic shifts per sequence) while still having sufficient total sequences available across all groups, thereby maintaining robustness to delay spread without sacrificing the number of usable sequences.
Data Source
AI summary
Provided is a sequence allocation method capable of reducing inter-cell interference of a reference signal when a ZC sequence is used as the reference signal in a mobile communication system. In the sequence allocation method, R×M sequences specified by a ZC sequence number r (r=1 to R) and a cyclic shift sequence number m (m=1 to M) are divided into a plurality of sequence groups X (X=1 to R) in accordance with the transmission band width of the reference signal, so that the ZC sequence is allocated to each cell in each sequence group unit. When it is assumed that R=9 and M=6, the number of sequences is 54. Each of the sequence groups is formed by two sequences. Accordingly, the number of sequence groups is 27. The 27 types of sequence groups are allocated to each cell.