Full Duplex Uplink Scheduling in Unlicensed Spectrum
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Solution Overview
Problem
In LTE and 5G wireless communication systems, the limited number of transmission slots in unlicensed spectrum limits achievable throughput due to interference and the need for Listen-Before-Talk mechanisms, making efficient simultaneous downlink and uplink communication challenging.
Innovation Solution
Implementing full duplex communication by allowing the evolved Node B to schedule uplink and downlink transmissions simultaneously, with the network node signaling user equipment to ignore carrier sensing mechanisms and perform self-interference cancellation, enabling the use of the same or overlapping frequency resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Listen-Before-Talk mechanism is implemented in unlicensed spectrum, then interference is reduced, but transmission slots are limited and throughput decreases
Solution Approach 1:
The patent implements full duplex communication that allows continuous simultaneous transmission of downlink and uplink communications during the same transmission slot, eliminating the alternating transmission pattern of half-duplex modes. This continuous useful action doubles the productive use of each transmission opportunity while the base station's interference management capabilities maintain reliability.
Solution Approach 2:
The patent transitions from time-division multiplexing (one dimension) to frequency-division full duplex (adding another dimension), allowing simultaneous uplink and downlink transmissions on the same frequency resources. This dimensional change enables parallel communication streams that overcome the sequential limitation of LBT-based half-duplex operation.
2Productivity
If full duplex communication is implemented with simultaneous uplink and downlink transmissions, then throughput is improved, but self-interference occurs
Solution Approach 1:
The patent converts the harmful self-interference effect into a beneficial training opportunity. During downlink transmissions, the base station intentionally allows self-interference to occur and uses this signal to train interference cancellation filters. The harmful interference becomes the training signal itself, which is then used to cancel future interference, transforming the problem into a solution.
Solution Approach 2:
The patent performs preliminary training of interference cancellation filters during downlink communication before uplink transmission begins. This preliminary action prepares the base station's signal processing capabilities in advance, enabling effective self-interference cancellation when full duplex operation commences, thereby preventing performance degradation.
3Reliability
If carrier sensing mechanism is enforced for uplink transmissions, then channel access is managed, but transmission delays increase
Solution Approach 1:
The patent extracts the carrier sensing requirement specifically for uplink transmissions scheduled during downlink frames, removing this constraint while maintaining it for other scenarios. The base station signals selected UEs to skip LBT and transmit immediately, extracting the sensing function from the uplink path while preserving it where needed, thereby eliminating unnecessary delays.
Solution Approach 2:
The base station acts as an intermediary that grants explicit permission for UEs to bypass carrier sensing. Through uplink grants and signaling, the base station mediates between the need for channel access management and the desire for immediate transmission, allowing UEs to skip LBT when authorized while maintaining overall channel coordination.
4Productivity
If uplink frequency resources overlap with downlink frequency resources, then spectral efficiency is improved, but interference management becomes more difficult
Solution Approach 1:
The patent creates a copied version of the downlink signal at the base station's receiver, using the known transmitted downlink signal as a reference copy. This copy is used in conjunction with trained interference cancellation filters to subtract the self-interference component from the received uplink signal, enabling separation of the overlapping frequency resources through signal processing rather than physical isolation.
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 significantly improves uplink throughput by allowing simultaneous data transfer during downlink frames, achieving nearly double the throughput compared to half-duplex modes with minimal impact on downlink performance and reducing the need for extensive UE hardware changes.
Implementation Method 1
training self-interference cancellation filters during a first portion of the downlink communication
Data Source
AI summary
A method and apparatus may include determining that downlink communication is to be scheduled for transmission to user equipment. The method may also include scheduling the downlink communication. The method may also include scheduling uplink communication. The uplink communication is transmitted by user equipment to the network node. The uplink communication and the downlink communication are transmitted such that (1) uplink frequency resources are the same as downlink frequency resources, (2) uplink frequency resources are contained within downlink frequency resources, or (3) uplink frequency resources overlap with downlink frequency resources. The method may also include signaling user equipment to ignore a carrier sensing mechanism. User equipment transmits the uplink communication at a time specified by the network node.