Uplink Frequency Offset Estimation via Random Access Channel Correlation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current frequency offset estimation methods for uplink conditions in OFDM-based wireless communication systems are inadequate, as they cannot be directly applied from downlink conditions, and existing techniques require excessive resource allocation for filter separation, making them impractical for high-speed data transmission.
Innovation Solution
A method and apparatus using a random access channel with two equivalent sequences to estimate uplink frequency offset by correlating samples and calculating a frequency offset estimator, which generates and transmits a specific sequence with protection regions to enable accurate frequency offset estimation without additional resource assignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional downlink frequency offset estimation methods are applied to uplink conditions with filter separation for each user, then frequency offset estimation can be performed, but the number of filters required increases to match the number of users, making the system impractical
Solution Approach 1:
The patent merges the frequency offset estimation for multiple users into a single unified estimation process. Instead of using separate filters for each user, the invention combines signals from multiple users and performs joint frequency offset estimation, thereby reducing the number of filters from equal to the number of users to just one or a small fixed number regardless of user count.
Solution Approach 2:
The patent creates a universal frequency offset estimation method that works for multiple users simultaneously using a single filter structure. The estimation algorithm is designed to handle signals from multiple users with different frequency offsets through a common processing framework, making the system scalable without increasing filter complexity.
2Reliability
If frequency offset estimation is performed in uplink conditions with multiple user signals, then accurate synchronization can be achieved, but existing methods require excessive resource allocation making them impractical for high-speed data transmission
Solution Approach 1:
The patent enables the uplink signal itself to provide the information needed for frequency offset estimation. By utilizing the structure and characteristics of the uplink signals from multiple users, the system performs self-estimation of frequency offsets without requiring additional dedicated pilot signals or excessive resources, thereby maintaining both accuracy and efficiency.
3Measurement precision
If the same downlink frequency offset estimation approach is used for uplink, then theoretical frequency offset estimation can be achieved, but the requirement for one filter per user makes it unrealistic in practice
Solution Approach 1:
The patent changes the fundamental parameter of filter quantity from being proportional to the number of users to being a fixed small number. This parameter change transforms the system from being impractical to implement to being feasible for real-world deployment while preserving the theoretical estimation capability.
Data Source
AI summary
Provided is an apparatus and method for estimating an uplink frequency offset in a wireless communication system. In a receiving apparatus of a wireless communication system using a random access channel composed of two equivalent sequences, the apparatus includes a channel receiver which extracts samples corresponding to the two sequences from an input random access channel signal; a correlator which computes first and second correlation values by correlating preceding and trailing samples among the samples output from the channel receiver with a predetermined sequence; and a frequency offset estimator which estimates a frequency offset by using a ratio of the second correlation value to the first correlation value output from the correlator.