Subframe-Type Indication Signal for LTE Unlicensed Spectrum Coexistence
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Solution Overview
Problem
Existing LTE communication methods do not adequately consider the coexistence of LTE with other technologies in shared unlicensed spectrum, leading to degraded performance and resource wastage due to persistent CRS transmission.
Innovation Solution
Incorporating a Subframe-type Indication Signal (SIS) to differentiate between punctured and normal subframes, allowing communication devices to correctly map reference signals, control channels, and data channels, thereby improving coexistence of LTE with other technologies like Wi-Fi during Listen-Before-Talk processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If persistent CRS transmission is used in unlicensed spectrum, then LTE communication continuity is maintained, but interference with other technologies (Wi-Fi) increases and coexistence performance degrades
Solution Approach 1:
The patent applies dynamics by making the CRS transmission pattern adaptive rather than persistent. The base station dynamically adjusts CRS transmission based on LBT outcomes and subframe types (normal vs. punctured), transitioning from continuous to conditional transmission. This resolves the contradiction by maintaining LTE continuity when needed while reducing interference when the channel is shared with other technologies.
Solution Approach 2:
The patent changes the transmission parameter of CRS from persistent/continuous to conditional/blocked based on subframe type. By introducing subframe-type indication signals that modify CRS transmission parameters (blocking CRS in punctured subframes), the system achieves both communication continuity and reduced interference, resolving the technical contradiction.
2Adaptability or versatility
If subframe-type indication signaling is introduced, then coexistence performance is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the subframe-type indication signal serve multiple functions: it indicates both the LBT outcome status and the CRS transmission requirement, and can be carried in existing control channels (PDCCH/EPDCCH) without requiring separate dedicated signaling. This multi-functionality reduces the actual complexity increase while achieving improved coexistence performance.
Solution Approach 2:
The patent uses the existing control channel (PDCCH/EPDCCH) as an intermediary carrier for the subframe-type indication signal, rather than creating a completely new signaling mechanism. This approach integrates the complexity into existing infrastructure, minimizing the actual complexity increase while achieving the desired coexistence improvement.
3Reliability
If LBT procedure is applied in unlicensed spectrum, then regulatory compliance is achieved, but transmission capacity is reduced due to punctured subframes
Solution Approach 1:
The patent applies preliminary action by performing LBT before the subframe begins, allowing the base station to pre-determine whether the subframe will be normal or punctured. This advance knowledge enables proper resource allocation and signaling to user equipment, maintaining transmission capacity while ensuring regulatory compliance through proper channel sensing.
Solution Approach 2:
The patent makes the transmission capacity adaptive by dynamically adjusting resource allocation based on LBT outcomes. When LBT succeeds, full capacity is utilized; when LBT fails, the subframe is punctured and resources are reallocated. This dynamic approach maintains regulatory compliance while maximizing transmission capacity under varying conditions.
Data Source
AI summary
A method performed by a first communication device is described herein for sending an indication to a second communication device. The first communication device determines an indication of a subframe type. The subframe type is of a subframe sent on a carrier by a cell associated with the first communication device and a second communication device. The subframe type is one of punctured and normal. The first communication device sends the indication to the second communication device, the indication being as determined by the first communication device.