NB-IoT Synchronization Signals Using Zadoff-Chu Sequence Offsets
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Solution Overview
Problem
Current LTE synchronization signal designs for NB-IoT lack efficient methods to reduce device complexity and enhance cell search capabilities, particularly in supporting low complexity devices with reduced bandwidth and multiple operation modes.
Innovation Solution
The design of NB-IoT Primary Synchronization Signals (NB-PSS) and Secondary Synchronization Signals (NB-SSS) using Zadoff-Chu sequences, where NB-PSS indicates channel raster offset and NB-SSS differentiates cell IDs through unique root indices and scrambling sequences, facilitating time and frequency synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LTE synchronization signal design is used for NB-IoT, then device complexity is reduced, but cell search capability and synchronization accuracy are insufficient
Solution Approach 1:
The patent modifies the synchronization signal parameters by using Zadoff-Chu sequences with different root indices and cyclic shifts to indicate channel raster offset information. This parameter change enables the NB-PSS to carry additional information (raster offset) while maintaining sequence properties that facilitate correlation-based detection, thereby improving synchronization accuracy without significantly increasing device complexity
Solution Approach 2:
The patent embeds channel raster offset information in the frequency domain by using different root indices of Zadoff-Chu sequences, rather than using time-domain variations alone. This dimensional approach allows the synchronization signal to convey multiple pieces of information (cell ID group and raster offset) simultaneously, enhancing cell search capability while keeping the signal structure simple for low-complexity devices
2Adaptability or versatility
If NB-IoT supports multiple operation modes (standalone, guard interval, in-band), then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent designs a universal NB-PSS structure using Zadoff-Chu sequences that can operate across all three NB-IoT deployment modes (standalone, guard interval, and in-band). The same sequence generation method and detection mechanism work for all modes, with the only variation being the root index selection to indicate different raster offsets. This universal design enables multi-mode support without requiring separate synchronization signal processing for each mode, thus avoiding complexity increase
Solution Approach 2:
The patent segments the cell search process into two distinct stages: first detecting the NB-PSS to obtain timing synchronization and channel raster offset information, then detecting the NB-SSS to obtain frame synchronization and cell ID information. This segmentation allows the receiver to handle different operation modes in a structured manner, processing each mode's specific characteristics through dedicated detection steps while using a unified overall framework
3Difficulty of detecting and measuring
If channel raster offset information is indicated in synchronization signals, then cell search capability is enhanced, but signal complexity increases
Solution Approach 1:
The patent merges the channel raster offset indication function with the existing NB-PSS structure by utilizing different root indices of Zadoff-Chu sequences. Instead of adding a separate signaling mechanism for raster offset, the patent combines this information carrier role with the synchronization signal itself. The receiver extracts both timing synchronization and raster offset information from the same NB-PSS detection process, eliminating the need for additional separate signals and reducing overall system complexity
Data Source
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AI summary
Narrowband Internet of Things synchronization signals are described that carry offset information. In one example an evolved NodeB (eNB) to performs operations to transmit synchronization signals for time and frequency synchronization between the eNB and user equipments (UEs) for narrowband Internet of things (NB-Iot). The operations include concatenating a plurality of short ZadoffChu (ZC) sequences each having a different root index, the ZC sequences being ordered to indicate an offset for use by a UE, generating an NB-Iot Primary Synchronization Signal (NB-PSS) using the concatenation of short ZadoffChu (ZC) sequences, and transmitting the resulting NB-PSS by the eNB in a periodic manner to the UE, wherein, the offset is identified by the order of the ZC sequences.