Wireless Control Signaling with Adaptive Orthogonal CDM Codes
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently identifying multiple terminals using the same resources for ACK/NAK signaling due to issues with code division multiplexing (CDM) performance, particularly when high-speed terminals are involved.
Innovation Solution
A method and apparatus that dynamically select and allocate time domain orthogonal sequences of varying lengths based on cell conditions, ensuring orthogonality by using different cyclic shifts and orthogonal cover indices for terminals sharing resources, thereby improving CDM performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If code division multiplexing is used to allow multiple terminals to share the same time and frequency resources, then resource utilization is improved, but terminal identification accuracy deteriorates due to interference between terminals
Solution Approach 1:
The patent segments the code division multiplexing into two independent parts: frequency-domain cyclic shifts and time-domain orthogonal codes. This segmentation allows each part to handle specific aspects of terminal identification, with cyclic shifts providing frequency separation and orthogonal codes providing time separation, thereby improving overall identification accuracy while maintaining resource sharing.
Solution Approach 2:
The patent introduces a new dimension by combining both frequency-domain and time-domain multiplexing mechanisms. Instead of relying solely on frequency-domain cyclic shifts, the system adds time-domain orthogonal codes as an additional dimension, creating a two-dimensional code space that significantly increases the number of distinguishable terminals while maintaining orthogonality.
2Reliability
If frequency domain cyclic shifts are used for code division multiplexing, then terminal orthogonality is improved, but performance deteriorates in high-speed terminal scenarios
Solution Approach 1:
The patent makes the code selection dynamic by allowing the base station to select different time-domain orthogonal codes based on terminal speed conditions. For high-speed terminals, the system dynamically switches to orthogonal codes that maintain orthogonality under Doppler shift conditions, while for low-speed terminals, frequency-domain cyclic shifts are used. This dynamic adaptation resolves the contradiction between maintaining orthogonality and performing well in high-speed scenarios.
Solution Approach 2:
The patent changes the parameter of code selection based on terminal velocity. By monitoring terminal speed and adjusting the code type (cyclic shift vs. orthogonal code) accordingly, the system optimizes performance for different mobility conditions. This parameter change allows the system to maintain reliability across diverse operational scenarios.
3Device complexity
If a single fixed code sequence length is used for all terminals, then system simplicity is maintained, but adaptability to different cell conditions deteriorates
Solution Approach 1:
The patent implements dynamic code sequence length selection where the base station determines the appropriate code length based on cell conditions and terminal speed. The system can switch between different code sequence lengths (e.g., length-2 or length-4 orthogonal codes) depending on the operational requirements, providing adaptability while maintaining manageable complexity through base station control.
Solution Approach 2:
The patent changes the code sequence length parameter based on cell conditions such as terminal velocity and interference levels. By adjusting this parameter dynamically, the system adapts to different operational scenarios without requiring complex reconfiguration, achieving both simplicity and adaptability.
Data Source
AI summary
When a plurality of terminals share the same resources in a wireless communication system, and when control information such as acknowledgement/negative acknowledgement (ACK/NAK) information or scheduling information is transmitted, a method of efficiently performing code division multiplexing (CDM) is required to distinguish the plurality of terminals. In particular, it is necessary to develop a method by which a code sequence of CDM can be selected and used according to each cell condition. Provided is a method of forming a signal in a wireless communication system in which a plurality of terminals commonly share frequency and time resources. The method includes the operations of receiving condition information in a cell; selecting one of a plurality of time domain orthogonal sequences having different lengths, according to the condition information; and allocating the selected time domain orthogonal sequence to a control signal symbol block.