Narrow Band Synchronization Signal Using FEC Codewords
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Solution Overview
Problem
Narrow Band (NB) wireless communication systems face challenges due to resource limitations, particularly in NB-IoT and eMTC, where legacy synchronization signals like the Secondary Synchronization Signal (SSS) may not be feasible or desirable, leading to ambiguity and complex processing requirements.
Innovation Solution
A method and apparatus for generating and transmitting a Narrow Band Secondary Synchronization Signal (NB-SSS) using a sequence of orthogonal frequency division multiplexing (OFDM) symbols, where each symbol is mapped to a forward error correction (FEC) codeword, with source symbols carrying cell identifier and frame timing information, and parity symbols providing redundancy for error correction, utilizing short Zadoff-Chu sequences and specific cyclic shifts and root indexes to convey different cell ID and frame timing information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If legacy synchronization signals are used in narrow band communication, then the system can support traditional LTE protocols, but the resource limitations cause ambiguity and complex processing requirements
Solution Approach 1:
The patent changes the fundamental parameters of the synchronization signal by using repeated sequences within each OFDM symbol and across multiple symbols, rather than traditional single-instance sequences. This repetition structure transforms the detection approach from complex pattern recognition to simpler correlation-based detection, reducing processing complexity while maintaining reliability
Solution Approach 2:
The synchronization signal is segmented into multiple OFDM symbols with repeated sequences in each symbol. This segmentation allows the receiver to perform detection on individual symbols and combine results, reducing the computational burden compared to processing a long continuous sequence, thereby reducing device complexity while maintaining detection reliability
2Adaptability or versatility
If legacy synchronization signals are used in narrow band communication, then existing LTE infrastructure can be utilized, but resource limitations lead to ambiguity requiring complex processing
Solution Approach 1:
The patent designs a synchronization signal structure that serves multiple functions: it provides cell identification, frame timing information, and maintains compatibility with LTE infrastructure through OFDM modulation. The repeated sequence structure enables universal detection methods across different narrow band scenarios (NB-IoT, eMTC) while reducing processing complexity through correlation-based detection
Solution Approach 2:
The synchronization signal is designed with pre-defined repeated patterns and known sequence structures before transmission. This preliminary structuring allows the receiver to use template matching and correlation detection rather than complex blind detection, reducing processing complexity while maintaining protocol compatibility
3Loss of information
If traditional synchronization signals are transmitted in narrow band, then system compatibility is maintained, but resource constraints cause ambiguity and increased processing requirements
Solution Approach 1:
The repeated sequence structure provides implicit feedback to the receiver - each repeated instance confirms the detection result. This redundancy acts as feedback that verifies synchronization information accuracy without requiring complex verification protocols, maintaining information accuracy while reducing processing complexity through simple correlation validation
Solution Approach 2:
The patent incorporates redundancy in the form of repeated sequences before transmission, which cushions against channel errors and ambiguities. This beforehand cushioning ensures synchronization information accuracy even in noisy narrow band conditions, while the structured repetition enables simple error correction through majority voting or correlation combining, reducing receiver processing complexity
Data Source
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AI summary
In order to reduce ambiguity in NB-SSS and complexity of receiver processing, a transmitter apparatus generates an SSS, wherein the SSS signal comprises a sequence of OFDM symbols, wherein each symbol of the sequence of SSS symbols is mapped to a codeword symbol of an FEC code. Source symbols of the sequence of SSS symbols carry a PCID and frame timing information, and parity symbols of the sequence of SSS symbols introduce redundancy and coding gain. A receiver receives the NB-SSS over multiple OFDM symbols, each symbol of the SSS comprising a short ZC sequence with a combination of root index and cyclic shift. The apparatus derives path metrics using cross-correlation for each of the plurality of symbols, determines a candidate SSS source message based on the derived path metrics and coding constraints of FEC codewords, and identifies a PCID and timing information based on the candidate SSS source message.