Narrowband M2M Cell Search Using Single Sync Sequence
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Solution Overview
Problem
Current narrowband machine-to-machine (NB M2M) cell search procedures face challenges in estimating time and frequency offsets, especially in bad or extended coverage, leading to longer synchronization times and reduced battery life, with high complexity and limited cell ID support.
Innovation Solution
A method using a single differentially encoded synchronization sequence, such as a Zadoff-Chu sequence, for both time and frequency offset estimation, allowing wireless devices to synchronize with network nodes more efficiently and supporting a larger number of cell IDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three separate sequences (PSS, SSS, FIIS) are used for cell search, then cell ID detection and frame synchronization are achieved, but synchronization time increases and battery life decreases
Solution Approach 1:
The patent combines PSS, SSS, and FIIS into a single synchronization sequence that carries multiple functions. This single sequence enables both time/frequency offset estimation and cell ID detection simultaneously, eliminating the need for separate correlation operations for each sequence and reducing overall synchronization time.
Solution Approach 2:
The synchronization sequence is designed to perform multiple functions: time offset estimation, frequency offset estimation, and cell ID detection. By embedding different functional elements within a single sequence structure, the system achieves multi-functionality without requiring multiple separate sequences, thereby reducing processing time and power consumption.
2Measurement precision
If device clock inaccuracy is corrected, then frequency offset is reduced, but device complexity increases
Solution Approach 1:
The synchronization sequence contains embedded pilot symbols that enable the device to self-correct frequency offsets without requiring complex external calibration equipment or procedures. The sequence structure itself provides the reference signals needed for accurate frequency offset estimation, making the correction process self-contained and reducing overall system complexity.
3Adaptability or versatility
If multiple cells are supported, then network coverage is improved, but device complexity for cell search increases
Solution Approach 1:
The patent uses different Zadoff-Chu sequence roots and cyclic shifts to represent different cell IDs within a single synchronization sequence framework. By varying these parameters rather than using completely separate sequences for each cell, the system can support multiple cells while keeping the device's cell search algorithm relatively simple and unified.
Data Source
AI summary
A method in a wireless device is disclosed. The method comprises receiving a synchronization signal from a network node, the received synchronization signal comprising a synchronization sequence, a cell ID sequence, and a frame index indication sequence. The method further comprises estimating a time offset of the received synchronization signal using the synchronization sequence, and estimating a frequency offset of the received synchronization signal using the synchronization sequence. The method further comprises detecting a cell ID of a cell associated with the network node using the estimated time offset and the estimated frequency offset, and detecting a frame number using the estimated time offset, the estimated frequency offset, and the detected cell ID of the cell associated with the network node.