Time-first mapping for unlicensed band signal transmission
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently transmitting and receiving signals through unlicensed bands due to interference from other systems, particularly in LTE systems, where frequency-first mapping can lead to symbol-selective interference and resource collisions.
Innovation Solution
Implementing a time-first mapping scheme for downlink data channels in unlicensed bands, along with additional interleaving techniques, to distribute interference uniformly across code blocks and minimize the impact of symbol-selective interference, while also considering timing advance and HARQ-ACK timing adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If frequency-first mapping scheme is used for downlink data channel in unlicensed band, then resource allocation is simplified, but symbol-selective interference occurs and decoding reliability deteriorates
Solution Approach 1:
The patent inverts the conventional frequency-first mapping approach by implementing time-first mapping for unlicensed bands. Instead of mapping code blocks sequentially across frequency resources first, the system maps code blocks across time resources (OFDM symbols) first, then distributes them across frequency. This inversion resolves the symbol-selective interference problem by ensuring that adjacent code blocks are separated in time rather than concentrated in specific frequency symbols where interference occurs.
Solution Approach 2:
The patent applies different mapping schemes to different band types: frequency-first mapping for licensed bands and time-first mapping for unlicensed bands. This local quality approach tailors the resource allocation strategy to the specific interference characteristics of each band type, optimizing both simplicity where applicable (licensed) and reliability where needed (unlicensed).
2Reliability
If time-first mapping scheme is applied to distribute code blocks across time resources, then symbol-selective interference is reduced, but mapping complexity increases
Solution Approach 1:
The patent segments the downlink data channel into multiple code blocks and applies systematic interleaving techniques. The time-first mapping divides code blocks across different OFDM symbols and subcarriers in a structured manner, while additional interleaving further segments and redistributes code block groups across resource blocks. This segmentation approach manages complexity by breaking down the mapping process into manageable, standardized steps rather than requiring complex adaptive algorithms.
Solution Approach 2:
The patent changes the mapping parameters specifically for unlicensed bands by introducing a mapping indicator that switches between frequency-first and time-first schemes. This parameter change allows the system to adapt to different band characteristics without redesigning the entire mapping architecture, managing complexity through configurable parameters rather than multiple independent algorithms.
3Reliability
If additional interleaving is applied to code blocks in unlicensed band, then interference uniformity across code blocks is improved, but processing time increases
Solution Approach 1:
The patent applies preliminary interleaving to code blocks before they are mapped to physical resources in the unlicensed band. By pre-distributing code blocks across different resource blocks and OFDM symbols through interleaving, the system ensures that interference is uniformly distributed before transmission begins. This preliminary action prevents concentrated interference patterns from affecting multiple code blocks simultaneously, reducing the need for retransmissions and actually saving time in the long run.
Solution Approach 2:
The interleaving process applies periodic distribution patterns to code blocks, systematically assigning them to different resource blocks in a repeating sequence. This periodic action ensures uniform interference distribution across all code blocks while maintaining a predictable, efficient processing rhythm that minimizes overall processing time through regularity and pattern recognition.
Data Source
AI summary
In the present application, a method is disclosed of transmitting a downlink data channel from a base station through a terminal in a wireless communication system. In particular, the method comprises the steps of: mapping the downlink data channel to a transmitting resource of a licensed bandwidth or a transmitting resource of an unlicensed bandwidth; and transmitting the mapped downlink data channel via the terminal. The step of mapping the downlink data channel is characterized by comprising the steps of: applying a frequency priority mapping technique when the downlink data channel is mapped to the transmitting resource of the licensed bandwidth; and applying a time priority mapping technique when the downlink data channel is mapped to the transmitting resource of the unlicensed bandwidth.