Uplink Access via PDCCH Feedback
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Solution Overview
Problem
The existing Instant Uplink Access (IUA) operation in LTE networks is inefficient due to the need for continuous PHICH transmissions, which are energy-intensive and can lead to data loss and interference, especially in time division duplex mode and unlicensed bands, where uplink and downlink transmissions share the same frequency bands.
Innovation Solution
The proposed solution involves configuring user equipment (UE) to ignore PHICH transmissions and assume a NACK response, allowing non-adaptive retransmissions when a response from the network node is missing, and using a control channel for acknowledgments and resource grants, thereby reducing unnecessary transmissions and conserving energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous PHICH transmissions are used for IUA operation, then acknowledgment feedback is provided to UE, but energy consumption increases and data loss occurs in TDD mode and unlicensed bands
Solution Approach 1:
The patent applies periodic action by transitioning from continuous PHICH transmissions to periodic PDCCH-based acknowledgments. The UE is configured to monitor PDCCH for uplink grants at specific intervals (e.g., every 4, 8, or 16 subframes) rather than requiring continuous PHICH feedback, thereby reducing energy consumption while maintaining reliable acknowledgment mechanisms through periodic control channel monitoring.
2Reliability
If PHICH transmissions are always enabled for IUA, then HARQ feedback is provided, but interference increases in unlicensed bands where uplink and downlink share the same frequency
Solution Approach 1:
The patent extracts the HARQ feedback function from the PHICH channel and relocates it to the PDCCH. By taking out the acknowledgment mechanism from the downlink PHICH and implementing it through uplink-oriented PDCCH grants, the system eliminates downlink transmissions in unlicensed bands while maintaining HARQ functionality, thereby reducing interference in frequency bands where uplink and downlink share the same spectrum.
3Use of energy by moving object
If PHICH is not transmitted when data is successfully received, then energy is saved, but UE cannot distinguish between successful reception and missed PHICH transmission
Solution Approach 1:
The patent implements feedback through PDCCH monitoring where the network sends explicit uplink grants containing acknowledgment information. Instead of relying on the absence or presence of PHICH transmissions, the system provides positive feedback through PDCCH grants that clearly indicate whether the uplink transmission was successfully received, eliminating ambiguity while maintaining energy efficiency by only transmitting when necessary.
Solution Approach 2:
The PDCCH acts as an intermediary mechanism that mediates between the network's need to acknowledge successful receptions and the UE's need for clear feedback. By introducing PDCCH grants as an intermediate communication channel, the system provides unambiguous acknowledgment information without requiring continuous PHICH transmissions, thus resolving the information loss problem while preserving energy efficiency.
Data Source
AI summary
According to certain embodiments, a method is disclosed for use in a wireless device. The method comprises transmitting uplink data to a network node. The uplink data is transmitted according to a semi-persistent scheduling (SPS) configuration obtained from the network node. The uplink data is transmitted without transmitting padding when no data is available for transmission. The method further comprises retransmitting the uplink data to the network node until receiving an indication to transmit new uplink data. The indication is received from the network node via a control channel.