Narrowband Synchronization Signal Mapping in Single Resource Block
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently performing device discovery and synchronization for narrowband wireless communications, particularly in Machine-to-Machine (M2M) communications, due to high processing complexity and power consumption, and interference from legacy wideband signals in LTE systems.
Innovation Solution
The implementation of a synchronization signal, such as a Primary Synchronization Signal (PSS) or Secondary Synchronization Signal (SSS), transmitted within a single resource block in a narrowband transmission, along with a Common Reference Signal (CRS) that punctures the synchronization signal, allowing for efficient device discovery and synchronization. Additionally, the system identifies the location of the narrowband resource block within a wideband region and modifies subcarriers based on the center-frequency subcarrier for improved decoding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronization signals are transmitted in narrowband regions using traditional wideband methods, then device discovery and synchronization can be achieved, but processing complexity and power consumption increase significantly for MTC devices
Solution Approach 1:
The patent changes the fundamental parameters of synchronization signal transmission by confining them to narrowband regions (single resource block or 3-6 contiguous RBs) rather than wideband transmission. This parameter change reduces the processing burden on MTC devices while maintaining synchronization functionality, directly resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent segments the synchronization signal transmission into dedicated narrowband regions separate from wideband LTE transmissions. By dividing the frequency spectrum into narrowband slots for MTC devices, the system enables MTC devices to process only relevant narrowband signals rather than entire wideband signals, reducing processing complexity while preserving synchronization capability
2Reliability
If MTC devices use sampling rates appropriate for non-MTC devices, then signal processing can be performed, but power consumption becomes excessively high
Solution Approach 1:
The patent changes the sampling rate parameter from wideband rates (appropriate for non-MTC devices) to narrowband sampling rates matched to the narrowband transmission characteristics. This parameter change enables MTC devices to process signals at lower sampling rates, directly reducing power consumption while maintaining signal processing capability through proper normalization and scaling of the received narrowband signals
3Productivity
If narrowband transmissions are implemented within wideband LTE regions, then spectrum efficiency improves, but interference from legacy wideband signals increases
Solution Approach 1:
The patent segments the frequency spectrum by allocating specific narrowband regions within wideband LTE bands for MTC transmissions. This segmentation allows non-contiguous resource block allocations for MTC devices, enabling spectrum efficiency improvement while isolating MTC signals from legacy wideband signal interference through frequency-domain separation and selective reception
Solution Approach 2:
The patent converts the presence of legacy wideband signals into a benefit by using them as reference for synchronization and channel estimation. MTC devices can detect and synchronize to the CRS (Cell-specific Reference Signals) embedded in the narrowband transmissions, which are themselves part of the LTE infrastructure, thereby turning the coexistence challenge into a synchronization opportunity
4Productivity
If synchronization signals occupy multiple OFDM symbols in a single resource block, then device discovery efficiency improves, but signal robustness against interference decreases
Solution Approach 1:
The patent employs periodic transmission of synchronization signals across multiple OFDM symbols within the narrowband region. This periodic action in the time domain enhances device discovery efficiency by providing multiple opportunities for detection, while the repetition also provides inherent robustness through diversity combining, allowing the device to average out interference effects across multiple symbols
Data Source
AI summary
Various techniques for narrowband communications in a wireless communications network are provided. Narrowband communications may be transmitted using a single resource block (RB) of a number of RBs used for wideband communications. In order to provide for efficient device discovery and synchronization using narrowband communications, a synchronization signal, such as a primary synchronization signal (PSS) or secondary synchronization signal (SSS), may be transmitted within the single resource block. The synchronization signal may be transmitted, for example, using multiple orthogonal frequency division multiplexing (OFDM) symbols within the single RB. A common reference signal (CRS) may also be present in the single resource block, which may puncture the synchronization signal, in some examples. In other examples, the synchronization signal may be mapped to non-CRS symbols of the single resource block.