MIMO-OFDM Pilot Symbol Mapping for Frequency Offset Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MIMO-OFDM systems lack effective methods for high accuracy frequency offset estimation, transmission path fluctuation estimation, and synchronization, leading to suboptimal performance in wireless LANs.
Innovation Solution
A MIMO-OFDM transmission apparatus that transmits OFDM-modulated data symbols from multiple antennas and employs pilot symbol mapping to assign orthogonal sequences to specific carriers, enabling accurate frequency offset and phase noise estimation without requiring channel estimation values, while minimizing transmission peak power and maintaining estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pilot symbols are transmitted from multiple antennas in MIMO-OFDM system, then frequency offset estimation accuracy is improved, but transmission peak power increases
Solution Approach 1:
The patent divides the pilot symbol transmission into two distinct phases: a first period where pilot symbols are transmitted from multiple antennas to enable frequency offset estimation, and a second period where only data symbols are transmitted. This temporal segmentation allows the system to achieve accurate frequency offset estimation during the first period without the peak power constraints of continuous multi-antenna transmission during data communication.
Solution Approach 2:
The patent implements periodic transmission of pilot symbols at specific time intervals (first period) rather than continuous transmission throughout the entire data transmission period. This periodic action enables frequency offset estimation to be performed at appropriate intervals while minimizing the overall transmission peak power consumption during data communication periods.
2Measurement precision
If pilot symbols are transmitted from all antennas simultaneously, then estimation accuracy is improved, but channel estimation complexity increases
Solution Approach 1:
The patent segments the transmission timeline into a first period for pilot symbol transmission and a second period for data symbol transmission. During the first period, pilot symbols are transmitted from multiple antennas to enable accurate frequency offset and transmission path fluctuation estimation. During the second period, only data symbols are transmitted, eliminating the need for complex channel estimation while maintaining estimation accuracy through the pilot period.
Solution Approach 2:
The patent performs frequency offset estimation and transmission path fluctuation estimation during the first period using pilot symbols before the second period data transmission begins. This preliminary action allows the receiver to acquire accurate channel state information and frequency offset values in advance, which are then used during data transmission without requiring complex real-time channel estimation, thereby reducing overall system complexity.
3Measurement precision
If orthogonal sequences are assigned to same carriers from multiple antennas, then frequency offset estimation accuracy is improved, but transmission peak power increases
Solution Approach 1:
The patent segments the transmission into a first period where pilot symbols with orthogonal sequences are transmitted from multiple antennas on the same carriers to enable accurate frequency offset estimation, and a second period where data symbols are transmitted without requiring such complex configurations. This segmentation achieves the desired estimation accuracy during the first period while avoiding the peak power increase that would occur if orthogonal sequences were continuously transmitted during data communication.
Solution Approach 2:
The patent implements periodic transmission of pilot symbols with orthogonal sequences at specific time intervals rather than continuous transmission. During the first period, orthogonal sequences are assigned to same carriers from multiple antennas to maximize frequency offset estimation accuracy. During the second period, this complex configuration is not required, allowing the system to maintain estimation accuracy through periodic sampling while minimizing transmission peak power during data communication periods.
Data Source
AI summary
A MIMO-OFDM transmission apparatus is provided which allows high accuracy estimation of frequency offset, high accuracy estimation of a transmission path fluctuation and high accuracy synchronization/signal detection.Pilot symbol mapping (1111) is provided for forming pilot carriers by assigning orthogonal sequences to corresponding subcarriers among OFDM signals which are transmitted at the same time from respective antennas in the time domain.Even when pilot symbols are multiplexed among a plurality of channels (antennas), this allows frequency offset/phase noise to be estimated with high accuracy.