Uplink Gap Alignment for NB-IoT Reference Signal Orthogonality
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Solution Overview
Problem
In NB-IoT systems, the orthogonality of reference signals between terminal devices is compromised when different devices transmit uplink data on shared resources due to differing start locations, even after inserting 40 ms gaps to correct frequency offsets, leading to reduced uplink transmission efficiency.
Innovation Solution
Terminal devices and network devices determine a shared reference time domain location and adjust their start times based on this location, ensuring that gaps are aligned, thus maintaining orthogonality of reference signals before and after gap insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If terminal devices transmit uplink data on shared resources with different start locations, then resource utilization is improved, but reference signal orthogonality deteriorates after gap insertion
Solution Approach 1:
The patent applies preliminary action by pre-configuring gap insertion rules and reference signal patterns before uplink transmission. Terminal devices are instructed to insert gaps at specific positions (e.g., after certain number of slots) and use specific reference signal patterns that ensure orthogonality is maintained from the outset, rather than attempting to correct orthogonality issues after they arise from different start locations
Solution Approach 2:
The patent changes parameters of reference signals and gap insertion patterns based on terminal device characteristics and transmission conditions. Different terminal devices may be assigned different reference signal patterns, cyclic shifts, or gap positions to maintain orthogonality. The system dynamically adjusts these parameters to ensure that even with different start locations, the reference signals remain orthogonal after gap insertion
2Measurement precision
If 40 ms gaps are inserted to correct frequency offset, then frequency synchronization is improved, but reference signal orthogonality deteriorates when start locations differ
Solution Approach 1:
The patent applies local quality by making the gap insertion and reference signal properties device-specific rather than uniform across all terminals. Each terminal device is configured with local parameters (such as device-specific cyclic shifts, pattern indices, or gap positions) that are tailored to its specific start location and transmission characteristics, ensuring that the local reference signal maintains orthogonality despite the global gap insertion
Solution Approach 2:
The system performs preliminary configuration of gap insertion rules and reference signal patterns before transmission. The network device pre-calculates and informs terminal devices about the appropriate gap positions and reference signal parameters that will maintain orthogonality, so that when gaps are inserted for frequency correction, the reference signals remain orthogonal by design rather than by chance
3Adaptability or versatility
If terminal devices use different start locations for uplink transmission, then transmission flexibility is improved, but uplink transmission efficiency deteriorates due to loss of reference signal orthogonality
Solution Approach 1:
The patent changes parameters of reference signals (such as cyclic shifts, patterns, or sequences) based on the terminal device's start location and other transmission parameters. This allows the system to maintain reference signal orthogonality even when terminal devices have different start locations, thereby preserving uplink transmission efficiency while retaining transmission flexibility
Solution Approach 2:
The system dynamically adjusts reference signal parameters and gap insertion patterns based on real-time transmission conditions, terminal device capabilities, and resource allocation. This dynamic adaptation ensures that reference signal orthogonality is maintained under varying conditions, preventing efficiency loss while allowing flexible start locations
Data Source
AI summary
Example communication methods and apparatus are described. In one example method, a first cell includes a plurality of terminal devices that can transmit uplink data on a same uplink time-frequency resource. A first terminal device in the plurality of terminal devices determines a reference time domain location based on a preconfigured uplink time-frequency resource, where the reference time domain location is the same as a reference time domain location determined by another terminal device in the plurality of terminal devices. The first terminal device determines a time domain location that is (first duration×N H+second duration×(N−1)) away from the reference time domain location as a start time domain location of X gaps. The first terminal device further determines a time domain location that is (first duration×(M−1)+second duration x (M−1)) away from the reference time domain location as a start time domain location of Y first durations, where Y=X or Y=X+1. Uplink data is sent by the first terminal device to a network device on a first time-frequency resource used to transmit uplink data.