OFDMA Preamble Sequence Generation for Spatial Channel Distinction
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Solution Overview
Problem
Current IEEE 802.16e communication systems lack distinct AAS preamble sequences for spatial channels, preventing accurate channel estimation and beam generation for multiple mobile subscriber stations, which hinders the implementation of the SDMA scheme.
Innovation Solution
Generating preamble sequences by phase-shifting or cyclically shifting predetermined sequences in the frequency or time domain, and using Walsh codes based on beam indices to distinguish between spatial channels, ensuring each mobile subscriber station receives a unique preamble sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distinct AAS preamble sequences are not provided for spatial channels, then the system structure remains simple, but accurate channel estimation and beam generation for multiple MSS cannot be achieved
Solution Approach 1:
The patent applies parameter changes by modifying the preamble sequence through phase-shifting or cyclic-shifting operations. Specifically, distinct preamble sequences are generated by applying different phase shift amounts or cyclic shift amounts to a base preamble sequence, allowing multiple spatial channels to be distinguished without fundamentally changing the preamble structure
Solution Approach 2:
The patent implements local quality by making specific portions of the preamble sequence distinctive through phase or cyclic shifts. Rather than completely differentiating entire preamble sequences, only specific parameters (phase shift amounts, cyclic shift amounts) are varied to provide the necessary distinction for spatial channel identification
2Productivity
If the SDMA scheme is not implemented, then the system is easier to operate, but cell capacity cannot be increased through spatial channel separation
Solution Approach 1:
The patent applies segmentation by dividing the spatial channel space into multiple distinct channels, each identified by a unique phase or cyclic shift pattern. This allows the base station to separately process and manage multiple spatial channels, effectively segmenting the overall communication space to increase cell capacity
3Productivity
If frequency and time resources are not reused across spatial channels, then interference between channels is minimized, but resource utilization efficiency decreases
Solution Approach 1:
The patent applies copying by using the same base preamble sequence for all spatial channels and then creating variations through phase or cyclic shifts. This allows frequency and time resources to be reused across spatial channels while maintaining distinguishability through the shifted versions of the copied preamble sequence
Data Source
AI summary
Disclosed is a method and an apparatus for generating a preamble sequence for an adaptive antenna system supporting a space division multiple access in an OFDMA communication system. Particularly, disclosed is a method for forming a preamble sequence identifying each of a plurality of mobile subscriber stations located within a cell or a sector of a communication system which includes a plurality of sub-channels assigned to the mobile subscriber stations, each of the sub-channels including a plurality of bins each of which includes n number of contiguous subcarriers in a frequency domain, the preamble sequence being transmitted before each of the sub-channels is transmitted, the method including the step of generating a preamble sequence by phase-shifting a predetermined sequence according to a predetermined phase shift sequence in the frequency domain.