Zadoff-Chu Sequence Selection for CoMP Terminal Interference Reduction
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Solution Overview
Problem
In LTE-Advanced systems, the orthogonality of Walsh sequences between CoMP and non-CoMP terminals collapses with temporal channel changes, leading to intersymbol interference and degraded reception performance in MU-MIMO communication.
Innovation Solution
A radio communication terminal apparatus and method that selects a base station other than the serving cell to generate and transmit a Zadoff-Chu reference signal, reducing interference by using a ZC sequence assigned to the selected base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Walsh sequence is used for DM-RS in MU-MIMO between CoMP and non-CoMP terminals, then orthogonality between terminals is achieved, but orthogonality collapses with temporal channel changes causing intersymbol interference
Solution Approach 1:
The patent changes the sequence type parameter from Walsh sequence to Zadoff-Chu sequence. ZC sequences have different autocorrelation and cross-correlation properties that maintain orthogonality even when channel conditions change temporally, thus resolving the orthogonality collapse issue while maintaining MU-MIMO performance
Solution Approach 2:
The patent employs sequence groups with specific ZC sequence numbers that are assigned differently to CoMP and non-CoMP terminals. By using disposable-like sequence assignments where each terminal type gets dedicated sequence numbers, the system avoids interference without requiring complex adaptive mechanisms
2Object-affected harmful factors
If different sequence groups are assigned to neighboring cells to reduce intercell interference, then intercell interference is reduced, but orthogonality between CoMP and non-CoMP terminals in the same cell is compromised
Solution Approach 1:
The patent applies different sequence assignment strategies to different terminal types within the same cell. CoMP terminals are assigned one set of ZC sequence numbers while non-CoMP terminals are assigned another set, creating local differentiation that maintains orthogonality between terminal types while allowing neighboring cells to use different sequence groups for intercell interference reduction
3Ease of operation
If the same ZC sequence number is used for DM-RS in CoMP terminal, then signal reception at multiple cells is simplified, but interference with non-CoMP terminals occurs due to non-orthogonal sequences
Solution Approach 1:
The patent segments the sequence number space into different sets for different terminal types. One set of ZC sequence numbers is reserved for CoMP terminals while another set is reserved for non-CoMP terminals. This segmentation ensures that terminals of different types use orthogonal sequences, eliminating interference while maintaining simplified reception processing at CoMP cells
Data Source
AI summary
Provided are a radio communication terminal apparatus and a radio transmission method by which intersymbol interference of DM-RS of a CoMP terminal and a Non-CoMP terminal can be reduced. A CoMP set setting unit (102) sets the cell IDs of all cells in the CoMP set in a cell selection unit (104), and a serving cell setting unit (103) sets the cell ID of the serving cell in the cell selection unit (104). The cell selection unit (104) selects the cell ID having a number closest to the cell ID of the serving cell from the cells in the CoMP set. A sequence information calculation unit (106) derives a sequence group number from the selected cell ID, and the sequence information calculation unit (106) calculates a sequence number from the derived sequence group number and a transmission bandwidth of the DM-RS.