Variable Bandwidth OFDMA System With Fixed Sampling Rate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-carrier communication systems face challenges in adapting to varying channel bandwidths, leading to increased system complexity, control issues, and unacceptable jitter in applications like voice over IP, due to changes in sampling rate and time-domain structure.
Innovation Solution
A variable bandwidth OFDMA system is implemented by maintaining a constant ratio between sampling frequency and FFT/IFFT length, adjusting the number of usable subcarriers, and using a core-band for essential radio control signals, with preambles designed to operate within a specific frequency segment, allowing for automatic bandwidth recognition and multi-mode operation across a wide range of bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sampling rate is varied to adapt to different channel bandwidths, then the system can operate across diverse bandwidths, but the symbol length and frame structure change causing increased system complexity and control issues
Solution Approach 1:
The patent changes the parameter of subcarrier spacing instead of sampling rate to adapt to different bandwidths. By adjusting subcarrier spacing while maintaining a fixed sampling rate, the system achieves bandwidth adaptability without changing symbol length or frame structure, thus avoiding increased system complexity
Solution Approach 2:
The patent segments the frequency spectrum into multiple subcarriers with adjustable spacing. This segmentation allows the system to accommodate different bandwidths by changing the number and spacing of subcarriers while keeping the overall time-domain structure intact
2Adaptability or versatility
If the sampling rate is varied to adapt to different channel bandwidths, then the system can operate across diverse bandwidths, but control and signaling problems arise
Solution Approach 1:
The patent changes subcarrier spacing rather than sampling rate, which maintains consistent symbol length and frame structure. This approach ensures that control and signaling mechanisms remain stable across different bandwidths, as the time-domain parameters remain unchanged
3Adaptability or versatility
If the frame structure is changed to adapt to different channel bandwidths, then the system can operate across diverse bandwidths, but unacceptable jitters occur in applications such as voice over IP
Solution Approach 1:
The patent maintains a fixed frame structure and sampling rate while adapting to different bandwidths by adjusting subcarrier spacing. This approach ensures that time-domain parameters remain constant, eliminating jitter issues in real-time applications like voice over IP while still providing bandwidth adaptability
Data Source
AI summary
Methods and apparatus for multi-carrier communication with variable channel bandwidth are disclosed, where the time frame structure and the OFDM symbol structure are invariant and the frequency-domain signal structure is flexible. In one embodiment, a mobile station, upon entering a geographic area, uses a core-band to initiate communication and obtain essential information and subsequently switches to full operating bandwidth of the area for the remainder of the communication. If the mobile station operates in a wide range of bandwidths, the mobile station divides the full range into sub-ranges and adjusts its sampling frequency and its FFT size in each sub-range.