Adapting Null Cyclic Prefix Length for 5G Spectral Efficiency
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Solution Overview
Problem
In 5G wireless networks operating above 40 GHz, the increased bandwidth and hardware impairments make fully digital array solutions infeasible due to high power consumption of ADCs and DACs, necessitating the use of analog electrically steered arrays, which limits multiplexing and equalization capabilities, and complicates the use of null cyclic prefixes in single-carrier modulation.
Innovation Solution
Adapting the null cyclic prefix length on a per-user basis in frequency-domain null single-carrier communication systems, allowing for optimized communication without changing overall frame timing, by determining the optimal NCP length based on channel estimates and using techniques like uplink sounding or downlink reference signals to minimize overhead and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed null cyclic prefix length is used for all users, then frame timing is simplified, but spectral efficiency decreases because LOS users cannot use shorter NCPs and non-LOS users cannot use longer NCPs
Solution Approach 1:
The patent segments the null cyclic prefix length by user equipment, allowing different NCP lengths to be assigned to different UEs based on their channel conditions (LOS vs non-LOS). This segmentation enables spectral efficiency optimization for each user without requiring a unified fixed NCP length for all users, thereby resolving the contradiction between spectral efficiency and timing complexity.
Solution Approach 2:
The patent introduces dynamic adaptation of NCP length on a per-user basis, where the gNB determines and signals the appropriate NCP length to each UE according to channel estimates. This dynamic approach allows the system to adjust NCP lengths flexibly for different users and conditions, improving spectral efficiency while maintaining timing integrity through centralized control.
2Productivity
If per-user null cyclic prefix adaptation is implemented, then spectral efficiency improves, but overhead increases due to additional signaling and processing
Solution Approach 1:
The patent performs channel estimation and NCP length determination in advance during uplink sounding or downlink reference signal transmission. By determining the optimal NCP length beforehand based on channel conditions, the system minimizes the overhead required during actual data transmission, as the NCP length decision is made during the initial channel characterization phase.
Solution Approach 2:
The system uses uplink sounding signals or downlink reference signals to automatically characterize channel conditions and determine appropriate NCP lengths without requiring additional explicit signaling for NCP length negotiation. The channel estimation process itself provides the information needed to select NCP lengths, making the system self-sufficient and reducing overhead.
3Reliability
If null cyclic prefix lengths are optimized for different user types, then data reception quality improves, but system complexity increases due to multiple NCP length configurations
Solution Approach 1:
The patent applies local quality optimization by tailoring the NCP length to the specific channel conditions of each user (LOS or non-LOS). Instead of using a uniform NCP length, the system assigns locally optimized NCP lengths based on individual user requirements, thereby improving data reception quality for each user type while managing system complexity through condition-based categorization.
Solution Approach 2:
The patent changes the NCP length parameter dynamically based on channel conditions and user type. By adjusting this critical parameter according to LOS/non-LOS classification and channel estimates, the system optimizes data reception quality for different users while maintaining manageable complexity through parameter adaptation rather than structural changes.
Data Source
AI summary
A method is provided including determining, for each of a plurality of user equipments, a null cyclic prefix length for communication in a wireless network using null cyclic prefix single-carrier modulation; and communicating with at least one of the user equipments based at least partially on the determined null cyclic prefix length of the at least one user equipment.