Zadoff-Chu Sequence Randomization for Inter-Cell Interference Reduction
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Solution Overview
Problem
In future-generation multi-cell mobile communication systems, inter-cell interference occurs when control information from different users is transmitted using different Zadoff-Chu sequences, leading to interference between cells.
Innovation Solution
Applying a cell-specific or UE-specific random sequence to control information in a subframe by using a randomized Zadoff-Chu sequence with random phase or cyclic shift values, which are signaled to user equipment (UE) and Node B, to randomize the interference across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different Zadoff-Chu sequences are used for control information transmission from different users, then user identification and multiplexing capability are improved, but inter-cell interference between cells increases
Solution Approach 1:
The patent applies random phase rotation or cyclic shift to the Zadoff-Chu sequences used for control information transmission. By changing the phase or cyclic shift parameter randomly across different subframes or cells, the interference pattern between cells is randomized, transforming deterministic interference into random noise that can be averaged out over time, thus reducing the impact of inter-cell interference while maintaining user identification capability
Solution Approach 2:
The patent introduces dynamic randomization of the Zadoff-Chu sequence parameters (phase or cyclic shift) that changes over time (different subframes) or space (different cells). This dynamic adjustment allows the system to adapt to varying interference conditions and randomize the interference pattern, converting static interference into dynamic random interference that can be mitigated through averaging
2Reliability
If Zadoff-Chu sequences are used for control information transmission, then orthogonality among users is maintained, but interference randomization capability is reduced
Solution Approach 1:
The patent modifies the Zadoff-Chu sequence by applying random phase rotation or cyclic shift while preserving the fundamental orthogonality properties. The randomization is applied in a controlled manner that maintains the constant amplitude zero autocorrelation (CAZAC) property of Zadoff-Chu sequences, ensuring orthogonality is preserved while adding interference randomization capability
Solution Approach 2:
The patent creates a composite signal structure by combining the original Zadoff-Chu sequence with random phase or cyclic shift components. This composite approach merges the orthogonality benefits of Zadoff-Chu sequences with the interference randomization benefits of random modulation, achieving both objectives simultaneously
Data Source
AI summary
Methods and apparatuses are provided for transmitting and receiving information. A User Equipment (UE) identifies first information for a cyclic shift value, transmitted from a Node B. The UE identifies second information for the cyclic shift value, transmitted from the Node B. The UE obtains a sequence based on a Zadoff-Chu sequence and the cyclic shift value defined based on the first information and the second information. The UE transmits the sequence in a Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbol to the Node B. The SC-FDMA symbol is predefined among a plurality of SC-FDMA symbols in a slot of a subframe.