TDD PDCCH Coverage Enhancement via Cross-Carrier Scheduling
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Solution Overview
Problem
The limited coverage area of TDD bands in FDD-TDD Carrier Aggregation (CA) restricts the downlink throughput gain, as the Physical Downlink Control Channel (PDCCH) is the coverage bottleneck, despite the wider coverage provided by FDD bands.
Innovation Solution
Implementing PDCCH coverage enhancement techniques using Open Radio Access Network (O-RAN) architecture, including PDCCH configuration optimization, beamforming, precoding, inter-cell coordination, and cross-carrier scheduling, facilitated by AI/ML models to expand TDD coverage area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher band TDD is added to FDD site with Carrier Aggregation, then downlink throughput is more than doubled, but coverage area is limited to the smaller TDD coverage area
Solution Approach 1:
The solution segments the control channel functionality by introducing cross-carrier scheduling where PDCCH on FDD carrier schedules PDSCH on TDD carrier. This separates the coverage-providing function (FDD PDCCH) from the throughput-enhancing function (TDD PDSCH), allowing users in FDD coverage area to access TDD downlink resources without being limited by TDD PDCCH coverage.
Solution Approach 2:
The FDD PDCCH acts as an intermediary that bridges the coverage gap. It carries scheduling assignments for TDD PDSCH, enabling users equipment in the broader FDD coverage area to receive and decode TDD downlink data transmissions, thus extending the effective coverage of the TDD carrier aggregation.
2Area of stationary object
If PDCCH coverage enhancement techniques are implemented, then TDD coverage area is expanded by 4 to 5 decibels, but device complexity increases
Solution Approach 1:
The system changes key parameters including PDCCH aggregation level (using higher aggregation levels like 8 or 16 for coverage enhancement), PDCCH power boost (increasing PDCCH transmission power by 3-6 dB), and PDCCH repetition (transmitting multiple copies of PDCCH). These parameter adjustments enhance coverage by 4-5 dB while managing complexity through network-side control.
Solution Approach 2:
The solution implements dynamic adaptation of PDCCH parameters based on channel conditions. The network dynamically adjusts aggregation level, power boost, and repetition factors according to user equipment's signal quality measurements, allowing coverage enhancement to be applied selectively to users who need it rather than uniformly to all users.
Data Source
AI summary
Time Division Duplexing (TDD) coverage enhancement in Frequency Division Duplexing (FDD)-TDD Carrier Aggregation (CA) is disclosed. The Physical Downlink Control Channel (PDCCH) configurations of the serving cell and its adjacent cells are collected and PDCCH coverage improvement techniques suitable for each cell and user situation are employed. Various data measurements are acquired to detect users with insufficient PDCCH coverage. A PDCCH allocation map is constructed between the serving cell and its adjacent cells and configuration information is exchanged with the adjacent cells. PDCCH configurations are then optimized for target users at or near the TDD cell edge in near-real time. For instance, the PDCCH Aggregation Level (AL) may be changed, PDCCH power may be boosted, PDCCH beamforming and precoding may be performed, inter-cell PDCCH coordination may be performed, cross-carrier scheduling may be performed, multi-Transmission Reception Point (TRP) PDCCH transmission may be performed, etc.