PRACH Frequency Hopping Patterns for Timing Offset Determination
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Solution Overview
Problem
Narrow band (NB) devices face challenges in determining timing offsets due to limited frequency bandwidth and large coverage areas, which existing PRACH procedures struggle to resolve effectively, especially in NB-IOT devices with limited frequency resources and extended timing offsets.
Innovation Solution
Implementing frequency hopping patterns for PRACH transmissions that include a combination of large and small frequency hops to facilitate accurate timing offset determination, using linear hash functions and cyclic shifts to generate non-overlapping random access preambles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If single tone signals are used for PRACH transmissions to provide flexibility in NB device support, then device adaptability is improved, but timing offset determination precision deteriorates
Solution Approach 1:
The PRACH transmission is segmented into multiple frequency hops rather than a single tone transmission. Each hop provides a measurement point for timing offset determination. The frequency domain is divided into multiple resource blocks that can be individually accessed, allowing the system to maintain flexibility for different NB devices while obtaining multiple timing measurements across different frequency positions.
Solution Approach 2:
The solution transitions from a single-point timing measurement to a multi-point measurement by introducing frequency hopping. Instead of determining timing offset at one frequency position, the system measures timing offsets across multiple frequency hops, adding the frequency dimension to the timing measurement process. This enables more robust timing synchronization while maintaining device flexibility.
2Area of stationary object
If large coverage areas are supported with extended timing offsets, then service area is improved, but timing resolution deteriorates
Solution Approach 1:
The timing offset measurement is segmented across multiple frequency hops. Instead of relying on a single timing measurement that must accommodate large propagation delays, the system performs multiple timing measurements at different frequency positions. This segmentation allows the system to support large coverage areas while maintaining timing resolution through aggregated measurements from multiple hops.
Solution Approach 2:
The solution replaces the traditional time-domain timing measurement approach with a frequency-domain measurement approach. By measuring timing offsets across multiple frequency hops and analyzing the phase differences in the frequency domain, the system can achieve better timing resolution for large coverage areas without being limited by the cyclic prefix length.
3Measurement precision
If frequency hopping patterns with multiple hop distances are implemented to improve timing resolution, then timing measurement precision is improved, but system complexity increases
Solution Approach 1:
The system changes the frequency hop distance parameter dynamically based on the measurement requirements. Different hop distances are used in different scenarios: larger hops for initial acquisition and smaller hops for fine timing resolution. This parameter adaptation allows the system to achieve high timing measurement precision while managing complexity by using standardized frequency hopping mechanisms with configurable parameters.
Data Source
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AI summary
Methods, systems, and devices are described for wireless communication. Dedicated frequency resources of a physical random access channel (PRACH) maybe designated for large and small frequency hops to facilitate the determination of timing offsets for PRACH transmissions. For instance, a frequency hopping pattern within the PRACH channel having a plurality of single tone transmission may include a first number of hops associated with a first frequency hopping distance (e.g., large frequency hops), and a second number of hops associated with a second frequency hopping distance (e.g., small frequency hops).