TDD Radio Transmit Power Allocation in Shared Spectrum
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Solution Overview
Problem
Current shared spectrum allocation techniques for Time Division Duplexing (TDD) systems in Citizens Broadband Radio Service (CBRS) are inefficient, as they assume simultaneous transmission from all CBSDs, leading to lower power levels being allocated to CBSDs, which restricts their operational range and number in a neighborhood.
Innovation Solution
A method to determine the largest interferer in a TDD system and allocate maximum allowable transmit power levels to it, while adjusting other TDD CBSDs' power levels based on this, allowing increased transmission power and operational range for CBSDs, including access points, by identifying and prioritizing the CBSD with the highest interference contribution in each protection point's neighborhood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interference margin is allocated fairly to all CBSDs assuming simultaneous transmission, then interference protection is ensured, but transmission power levels are reduced and operational range is limited
Solution Approach 1:
The patent applies dynamics by transitioning from static interference margin allocation (assuming all CBSDs transmit simultaneously) to dynamic allocation based on actual transmission timing. The SAS controller determines interference contributions only from CBSDs actively transmitting during specific time intervals, allowing transmission power levels to adapt dynamically to actual network conditions and TDD configurations.
Solution Approach 2:
The patent changes the parameter of interference calculation from a static worst-case assumption to a dynamic parameter that varies with TDD configuration and actual transmission patterns. By recalculating interference margins based on which CBSDs are actually transmitting at given times, the system optimizes the balance between interference protection and transmission power allocation.
2Reliability
If interference margin is allocated to all CBSDs in the neighborhood, then interference protection is provided, but the number of operational CBSDs and their range are restricted
Solution Approach 1:
The system dynamically adjusts the set of CBSDs contributing to interference calculations based on TDD configurations and actual transmission schedules. Instead of statically including all CBSDs in the neighborhood, the SAS controller identifies only those CBSDs that are actively transmitting during relevant time intervals, thereby reducing the number of CBSDs that constrain power allocation while maintaining interference protection.
Solution Approach 2:
The patent applies partial action by considering only the subset of CBSDs that are actually transmitting at any given time, rather than allocating interference margins for all potential CBSDs. This selective approach reduces the total interference burden assumed in the system, enabling more CBSDs to operate within the neighborhood while maintaining adequate protection.
3Power
If maximum transmission power is allocated to all CBSDs simultaneously, then transmission range is maximized, but interference at protection points becomes excessive
Solution Approach 1:
The patent leverages periodic TDD transmission patterns to manage interference. By analyzing interference contributions in the context of periodic time-division schedules, the SAS controller determines that not all CBSDs transmit at maximum power simultaneously. This periodic action allows the system to allocate higher power levels to individual CBSDs during their designated transmission windows while maintaining acceptable overall interference levels at protection points.
Solution Approach 2:
The system dynamically adjusts power allocation based on the temporal dimension of TDD operations. Instead of applying a static power ceiling to all CBSDs, the SAS controller determines time-varying power levels that reflect actual transmission patterns, enabling CBSDs to operate at higher power when their transmissions do not create excessive interference at protection points.
Data Source
AI summary
Techniques for determining power levels of radios, including a time domain duplexing (TDD) system, in shared frequency spectrum is provided. A TDD radio, of the TDD system, in a neighborhood having a largest interference contribution in the frequency spectrum at the point. Transmit power levels are determined for (a) the selected TDD radio, (b) other radios in the neighborhood that are not part of the TDD system, and (c) at least one radio in the TDD system that is not the TDD radio having the largest interference contribution in the frequency spectrum. Thus, interference margin may be fairly allocated to radios in neighborhood(s) about protection points.