Frequency Offset Compensation via Terminal Grouping and Pilot Estimation
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Solution Overview
Problem
The existing WiMAX frequency offset compensation methods in the WiMAX protocol result in significant processing delays and slow responses to frequency offset changes due to the need for message delivery over the downlink air interface, which occupies bandwidth and requires scheduler allocation.
Innovation Solution
The method involves estimating frequency offsets for terminals, grouping them based on similar offsets, and scheduling these groups to occupy time-frequency resources in different segments, allowing for immediate compensation without using downlink air interface resources and eliminating the need for message delivery and demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency offset compensation is implemented through message delivery over downlink air interface, then frequency offset can be compensated, but processing delay increases and response speed decreases
Solution Approach 1:
The base station performs frequency offset estimation and calculates compensation values in advance based on uplink pilot signals, before the terminal needs to transmit data. This preliminary calculation eliminates the need for real-time message delivery and demodulation, significantly reducing processing delay while maintaining compensation accuracy.
Solution Approach 2:
The patent extracts the frequency offset compensation function from the standard message delivery process. Instead of delivering compensation values through downlink messages that require scheduling and demodulation, the system directly applies pre-calculated compensation values to terminal signals, removing the time-consuming message delivery and processing steps.
2Reliability
If frequency offset compensation messages are delivered through downlink air interface, then compensation can be provided, but downlink air interface bandwidth is occupied
Solution Approach 1:
The patent removes the frequency offset compensation information from the downlink air interface message stream. By pre-calculating compensation values based on uplink pilot signals and directly applying them to terminal transmissions, the system eliminates the need to allocate downlink bandwidth for compensation messages, freeing up valuable air interface resources.
Solution Approach 2:
The base station uses the uplink pilot signals transmitted by terminals to self-determine the frequency offset values. This self-service approach allows the system to obtain compensation information from the terminal's own transmission signals rather than requiring separate downlink message delivery, thus conserving downlink bandwidth.
3Measurement precision
If frequency offset compensation requires message delivery and demodulation, then compensation accuracy can be maintained, but processing complexity and time increase
Solution Approach 1:
The base station performs frequency offset estimation and compensation value calculation in advance during the pilot signal reception phase. This preliminary action consolidates the complex processing steps before data transmission begins, simplifying the real-time processing requirements while maintaining estimation accuracy through proper signal processing techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables quick frequency offset compensation, reducing processing delays and conserving radio air interface resources by allowing simultaneous compensation of terminals within the same group without occupying downlink bandwidth.
Implementation Method 1
the Doppler frequency offset of the signals received by each terminal and the BS. The Doppler frequency offset is in proportion to the movement speed of the terminal and the carrier frequency.
Data Source
AI summary
Frequency offset compensating methods and apparatus are provided. A frequency offset of a terminal according to the pilots is estimated, and terminals are grouped according to the frequency offset of the terminals. The terminals in different frequency offset groups are dispatched and are scheduled to occupy the time frequency resources in different time slices. Frequency offset compensation is carried on for each group of terminals by using a corresponding frequency offset compensation value.