Pilot Sequence Generation Using Walsh and Mask Permutations
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Solution Overview
Problem
Next-generation wireless communication systems face challenges in supporting a large number of users with deep coverage and efficient spectral use, as existing pilot sequences struggle with interference suppression due to limited orthogonal sequences, especially with short PN code sequences exhibiting suboptimal cross-correlation statistics.
Innovation Solution
The method involves generating pilot sequences by determining mask sequences through permutations of values 1, −1, i, and −i, and combining them with Walsh sequences using indices to achieve better cross-correlation statistics, allowing for a larger number of orthogonal or substantially orthogonal sequences, which are then used for channel estimation and interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing pilot sequences are used, then the system can support basic communication, but the number of orthogonal sequences is limited and interference suppression is insufficient
Solution Approach 1:
The patent segments the pilot sequence generation into two independent components: mask sequences (generated via permutations of QPSK symbols) and Walsh sequences (from Hadamard matrices). This segmentation allows each component to be optimized separately and combined to achieve a larger total set of orthogonal sequences, resolving the limitation of using single-type sequences alone.
Solution Approach 2:
The patent creates a composite pilot sequence by combining mask sequences and Walsh sequences through element-wise multiplication. This composite approach leverages the properties of both sequence types to generate a larger number of orthogonal pilot sequences with improved interference suppression characteristics.
2Length of moving object
If short PN code sequences are used, then the sequence length is reduced, but cross-correlation statistics become suboptimal
Solution Approach 1:
By combining mask sequences with Walsh sequences, the patent creates composite pilot sequences that maintain short length while achieving optimal cross-correlation statistics. The Walsh component provides the mathematical structure needed for good correlation properties even at shorter lengths.
Solution Approach 2:
The patent changes the structural parameters of the pilot sequence by introducing the mask sequence component with specific permutation patterns. This parameter change allows the sequence to maintain short length while improving cross-correlation statistics through the structured variation introduced by the mask component.
3Productivity
If more users are supported with deep coverage, then network capacity increases, but interference suppression becomes more difficult
Solution Approach 1:
The patent segments the orthogonal sequence space into multiple groups using different mask sequences, allowing users to be distributed across these groups. This segmentation enables support for more users while maintaining interference suppression within each group through the use of Walsh sequences.
Solution Approach 2:
The patent adds a new dimension to the pilot sequence design by introducing mask sequences as a separate layer above the traditional Walsh sequences. This dimensional expansion creates a two-level structure that increases the total number of available orthogonal sequences, enabling support for more users while maintaining interference suppression capabilities.
Data Source
AI summary
Methods, systems, and devices are disclosed for digital wireless communication, and more specifically, for the use of pilot sequences that improves performance of channel estimation. In one exemplary aspect, a method of wireless communication performed by a communication node is disclosed. The method includes determining, using a first index, a mask sequence from a plurality of pre-determined mask sequences, wherein the plurality of pre-determined mask sequences is determined based on permutations of values 1, −1, i, and −i or permutations of values 1+i, or 1−i, or −1+i, or −1−i; determining a Walsh sequence using a second index, wherein the Wash sequence has a same length as the mask sequence; generating a pilot sequence by combining the mask sequence and the Walsh sequence; and performing a wireless transmission using the pilot sequence.