Spectrum Scheduling Controller for Interference-Aware Slot Sharing
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Solution Overview
Problem
Existing spectrum allocation methods in the Citizens Broadband Radio Services (CBRS) band face inefficiencies due to limited channel bandwidths and interference issues, particularly in dense urban areas, and the use of Listen Before Talk (LBT) in low or mid-frequency bands leads to user contention and inefficient channel use.
Innovation Solution
A spectrum scheduling controller (SSC) manages resource requests from operator devices, considering latency and data transmission requirements, and groups devices based on coverage contours and interference potential to allocate time-frequency resources efficiently, using guard intervals to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SAS allocates spectrum in frequency domain with minimum 10 MHz channel bandwidth, then spectrum sharing is enabled, but in dense urban areas coverage is reduced due to reduced radio transmit power
Solution Approach 1:
The patent segments the frequency spectrum into multiple channels and further segments time into slots, creating a two-dimensional time-frequency resource allocation framework. This allows the system to serve multiple users simultaneously in different time-frequency resources while maintaining adequate power per user, thereby preserving coverage area while enabling spectrum sharing.
Solution Approach 2:
The patent transitions from one-dimensional frequency-domain allocation to two-dimensional time-frequency resource allocation. By adding the time dimension with configurable slot durations, the system can allocate resources more flexibly, allowing users to access spectrum in different time slots rather than competing for simultaneous frequency access, thus maintaining coverage while enabling sharing.
2Stability of the object's composition
If users on adjacent frequencies use the same TDD uplink-downlink configuration, then frame synchronization is achieved, but base station to base station adjacent channel interference occurs
Solution Approach 1:
The patent assigns different TDD uplink-downlink configurations to different geographic locations or cells. Each base station can be configured with appropriate uplink-downlink patterns based on local interference conditions and traffic requirements, allowing frame synchronization to be maintained within each cell while preventing adjacent channel interference between neighboring base stations through localized configuration differentiation.
3Reliability
If LBT approach is used in low or mid frequency bands, then frequency access is controlled, but channel use efficiency decreases due to user contention in congested environments
Solution Approach 1:
The patent implements preliminary resource allocation where the spectrum access system pre-assigns time-frequency resources to users before transmission occurs. This eliminates the need for contention-based LBT procedures at the time of transmission, as users already have authorized resources allocated to them, thereby maintaining reliable frequency access control while dramatically improving channel use efficiency in congested environments.
Data Source
AI summary
Methods and apparatus for implementing a spectrum scheduling controller (SSC) are described. The spectrum scheduling controller receives resources requests from operator devices, e.g., access points which can be in the form of base stations. The access points can, and sometimes do, correspond to different operators and/or use different communications technologies. The SSC determines the coverage areas of the operator devices requesting resources and groups them into groups based on the potential for interference, e.g., contour area overlap. Operator devices are synchronized on a frame and/or transmission slot level basis with a frame including multiple slots. A schedule is created allocating slots corresponding to operator devices based on latency and/or data transmission requirements. Device priority can be, and sometimes is, considered when generating a schedule. The schedule allocating resources is communicated to members of an operator device group to which the schedule relates.