OFDM Receiver Buffer Synchronization via Cyclic Prefix Correlation
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Solution Overview
Problem
In communication systems like digital audio broadcasting (DAB), synchronization of receiver processing circuitry is challenging due to slow synchronization information rates, especially in noisy conditions, leading to difficulties in aligning symbol timing and carrier frequency.
Innovation Solution
An apparatus and method that utilize a buffer and feedback circuit to align OFDM samples by computing prefix correlations, detecting peak values, and filtering sample indices to generate a feedback value, allowing for synchronization without relying on synchronization information within the data stream, thereby enabling rapid and resilient synchronization of symbol timing and carrier frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronization information is inserted periodically in the data stream, then the receiver can synchronize its processing, but the synchronization rate is slow and difficult in noisy conditions
Solution Approach 1:
The system uses the OFDM signal itself (specifically the cyclic prefix portion) to generate synchronization information, rather than relying on externally inserted synchronization symbols. The correlation between the cyclic prefix and the corresponding signal portion provides inherent synchronization cues that are robust to noise and enable rapid synchronization.
Solution Approach 2:
The invention extracts synchronization information from the cyclic prefix portion of the OFDM signal, separating this function from dedicated synchronization symbols. By utilizing the redundant cyclic prefix data, the system achieves both timing and frequency synchronization without depending on periodically inserted synchronization information.
2Reliability
If conventional synchronization methods are used, then synchronization information is available, but synchronization time is long and resilience to noise is poor
Solution Approach 1:
The OFDM signal's cyclic prefix serves dual purposes: maintaining signal integrity and providing synchronization information. This self-service approach eliminates the need for separate synchronization symbols, reducing synchronization time while improving resilience since the cyclic prefix is inherently robust to noise and multipath effects.
Solution Approach 2:
The cyclic prefix, originally designed for combating inter-symbol interference, is made multi-functional by also serving as the source for synchronization information. This universal utilization of signal components reduces overall system complexity and improves performance without adding dedicated synchronization elements.
Data Source
AI summary
In an embodiment, an apparatus includes a buffer to store incoming orthogonal frequency division multiplexed (OFDM) samples. This buffer is configured to output the OFDM samples according to a read pointer that can be adjusted by a sum value corresponding to a sum of a length of a symbol and a feedback value, to align the read pointer with the symbol. In addition, the apparatus further includes a feedback circuit coupled to the buffer to receive the output OFDM samples and generate the feedback value based at least in part on the output OFDM samples.