Multi-beam Discovery Reference Signals for Shared Spectrum
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Solution Overview
Problem
Wireless communication systems, particularly in millimeter wave frequencies, face challenges with signal attenuation and overcrowding due to frequent transmission of critical reference signals in shared spectrum systems, leading to coexistence issues and inefficiencies in channel access procedures.
Innovation Solution
The implementation of multi-beam and opportunistic discovery reference signals (DRS) transmission techniques, where base stations transmit DRS in a multi-beam or single-beam fashion, opportunistically or periodically, using beamforming and listen-before-talk procedures to manage channel access and reduce overcrowding, allowing for more efficient spectrum usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequent or periodic transmission of discovery reference signals is implemented, then cell synchronization and discovery are maintained, but spectrum overcrowding and coexistence issues occur
Solution Approach 1:
The patent implements periodic transmission of discovery reference signals at configured intervals rather than continuous transmission. The base station transmits DRS periodically based on configured periodicities (e.g., every 20ms, 40ms, or 80ms), which maintains cell synchronization and discovery functionality while reducing overall signal density in the spectrum, thereby mitigating overcrowding issues in shared spectrum environments.
Solution Approach 2:
The patent enables dynamic adjustment of DRS transmission parameters including periodicity, bandwidth, and power based on network conditions, traffic load, and interference levels. This dynamic configuration allows the system to adapt transmission frequency to maintain reliable discovery while avoiding excessive spectrum occupancy, resolving the contradiction between reliability and spectrum crowding.
2Productivity
If multiple operators use shared spectrum, then spectrum utilization efficiency is improved, but coexistence issues and interference increase
Solution Approach 1:
The patent implements listen-before-talk (LBT) procedures and channel sensing mechanisms before transmitting discovery reference signals. The base station performs clear channel assessment and energy detection in advance of DRS transmission to ensure the spectrum is available, preventing collisions with other operators' transmissions. This preliminary action enables multiple operators to share the spectrum efficiently while maintaining acceptable interference levels through coordinated access.
3Reliability
If beamforming is used to overcome path loss, then signal transmission reliability is improved, but system complexity increases
Solution Approach 1:
The patent segments the beamforming process into discrete, pre-configured beam patterns and transmission scenarios. Instead of implementing complex real-time adaptive beamforming, the system uses a limited set of predefined beam configurations that are selected based on channel conditions and UE location. This segmentation maintains signal transmission reliability through directional beamforming while significantly reducing the computational complexity and implementation burden.
4Adaptability or versatility
If channel sensing procedures are implemented, then fair spectrum access is achieved, but channel access time and overhead increase
Solution Approach 1:
The patent implements simplified channel sensing procedures that perform only the essential measurements needed for fair spectrum access decisions. Rather than comprehensive channel characterization, the system performs energy detection and basic clear channel assessment at critical decision points. This partial action approach achieves fair spectrum access among multiple operators while minimizing the time overhead and processing burden associated with extensive sensing procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the efficiency of reference signal transmission, reduces overcrowding, and improves coexistence in shared spectrum systems by optimizing beam usage and channel access, thereby maintaining effective cell synchronization and discovery while minimizing interference.
Implementation Method 1
signal processing techniques, such as beamforming, may be used to coherently combine energy and overcome the path losses at these frequencies
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. The method may include determining multiple transmission beams (e.g., beamformed directional beams) for transmission of an opportunistic or multi-beam discovery reference signal (DRS) over a shared radio frequency spectrum band. A base station may perform a listen before talk (LBT) procedure for the multiple DRS transmission beams, and transmit, based on the LBT procedure, the DRS over the shared radio frequency spectrum band using a set of the multiple transmission beams (e.g., a set that cleared an LBT procedure). In some cases, the LBT may be performed for each transmission beam, or for a union of all transmission beams, associated with the DRS transmission beams. Alternatively, the base station may determine a contention exempt transmission (CET) period for the shared spectrum band and transmit the DRS using the multiple transmission beams during CET period.