Cloud RAN LTE Scheduling for Unlicensed Spectrum Latency
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Solution Overview
Problem
Conventional radio access networks (RANs) face challenges in upgrading and evolving due to their integrated hardware design, leading to high capital and operating costs, and there is a need for scalable and easy-to-upgrade solutions to support increased capacity requirements, especially when extending LTE technologies to unlicensed and shared spectrum.
Innovation Solution
A system and method for LTE operation in unlicensed bands using a cloud RAN framework, where the BBU schedules non-GBR traffic on unlicensed cells and GBR traffic on licensed cells, with retransmission of failed packets on licensed bands, and employs dynamic frequency selection and Listen Before Talk (LBT) processes to optimize spectrum usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LTE operation is enabled in unlicensed bands, then spectrum utilization is improved, but communication latency increases due to fronthaul latency and spectrum sensing execution
Solution Approach 1:
The system performs preliminary actions by pre-scheduling traffic on licensed cells before attempting unlicensed spectrum access. The BBU prepares and buffers packets for potential unlicensed transmission, and the system pre-establishes licensed cell pathways as backup routes. This preliminary preparation reduces the impact of latency when unlicensed access is attempted, as the system has already positioned data for rapid transmission or fallback.
Solution Approach 2:
The patent introduces an intermediary mechanism where the BBU acts as a mediator between the licensed and unlicensed spectrum operations. The BBU manages the timing coordination, packet buffering, and dynamic switching between licensed and unlicensed cells. This intermediary control layer allows the system to optimize spectrum utilization while managing latency through intelligent packet handling and retransmission strategies.
2Reliability
If dynamic frequency selection and retransmission strategies are implemented, then spectrum access uncertainty is reduced, but device complexity increases
Solution Approach 1:
The system segments the complexity management by dividing responsibilities between the BBU and the network infrastructure. The BBU implements the core dynamic frequency selection logic and retransmission strategies, while leveraging existing network components for execution. This segmentation allows sophisticated spectrum access control without requiring every network element to be equally complex.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting transmission parameters such as timing advance values, packet buffering durations, and retransmission thresholds based on observed spectrum conditions. The BBU modifies these parameters in response to unlicensed spectrum availability, allowing the system to adapt to changing conditions without requiring permanent complex infrastructure changes.
3Productivity
If non-GBR traffic is scheduled on unlicensed cells, then spectrum efficiency is improved, but service reliability deteriorates due to shared spectrum access
Solution Approach 1:
The system implements dynamic traffic scheduling where the BBU continuously monitors unlicensed spectrum conditions and dynamically adjusts which non-GBR traffic flows are routed to unlicensed cells versus licensed cells. This dynamic approach allows the system to maximize spectrum efficiency when unlicensed access is favorable while automatically protecting service reliability when spectrum conditions deteriorate, creating a flexible dual-mode operation.
Solution Approach 2:
The patent incorporates feedback mechanisms where the BBU receives information about unlicensed spectrum access outcomes, transmission success rates, and latency measurements. This feedback is used to adjust future scheduling decisions, packet routing, and retransmission strategies. The feedback loop enables the system to learn from past performance and optimize the balance between spectrum efficiency and service reliability over time.
Data Source
AI summary
There is provided a system, method, and interfaces for Radio Access Networks and Cloud Radio Access Networks.