OFDM Pilot Sequence Generation for Sub-1 GHz M2M Systems
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Solution Overview
Problem
The existing IEEE 802.11 standards face challenges in generating pilot sequences for the sub 1 GHz band, particularly in M2M communication systems, which require efficient battery usage and automatic recovery functions, and struggle with spectral lines and memory requirements.
Innovation Solution
A method and apparatus for generating pilot sequences using orthogonal frequency division multiplexing (OFDM) symbols, where pilot values are determined by specific mathematical formulas and mapped in a pilot value table, allowing for BPSK modulation and transmission over multiple spatial streams, optimizing bandwidth and reducing memory needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pilot sequence generation methods are used in sub 1 GHz band, then existing IEEE 802.11 standards can be maintained, but spectral lines are generated and memory requirements increase
Solution Approach 1:
The patent changes the parameter of pilot sequence generation by using mathematical formulas (Pnk = -7 = Ψ(n mod 2) + 2, Pnk = 7 = Ψ((n+1) mod 2) + 2) instead of traditional methods, which eliminates spectral lines while maintaining communication reliability in sub 1 GHz band
Solution Approach 2:
The patent uses a pilot value mapping table that copies and maps pilot values for different bandwidths (1MHz, 2MHz, 4MHz, 8MHz) in a nested structure, allowing efficient memory usage and preventing spectral lines across multiple frequency bands
2Reliability
If traditional pilot sequence generation methods are used, then existing standards are maintained, but memory requirements increase
Solution Approach 1:
The patent implements a nested pilot value mapping table structure where pilot values for different bandwidths (1MHz, 2MHz, 4MHz, 8MHz) are organized in a hierarchical manner, allowing efficient memory usage and reducing memory requirements while maintaining communication reliability
Solution Approach 2:
The patent changes the parameter of pilot sequence generation by using mathematical formulas (Pnk = -7 = Ψ(n mod 2) + 2, Pnk = 7 = Ψ((n+1) mod 2) + 2) instead of traditional methods, which reduces memory requirements while maintaining communication reliability in sub 1 GHz band
3Reliability
If pilot sequences are transmitted over multiple OFDM symbols, then communication reliability is improved, but transmission time increases
Solution Approach 1:
The patent uses periodic action by transmitting pilots over N OFDM symbols with repeating patterns (Ψ(n mod 2) and Ψ((n+1) mod 2)), which improves communication reliability through multiple transmissions while the periodic nature allows efficient time management
Solution Approach 2:
The patent ensures continuity of useful action by maintaining pilot transmission across multiple OFDM symbols with consistent mathematical formulas, ensuring reliable communication while optimizing the continuous transmission process
Data Source
AI summary
A method of transmitting pilots id disclosed. The method of transmitting pilots includes transmitting pilots over N orthogonal frequency division multiplexing (OFDM) symbols, wherein a pilot at subcarrier k for OFDM symbol n is determined to have time varying characteristic, thereby to prevent the cause of spectral lines.