DwPTS Subframe Signal Demodulation Using Preceding DMRS
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Solution Overview
Problem
The LTE system faces challenges in transmitting and demodulating Downlink Pilot Time Slot (DwPTS) subframes, particularly in configurations with fewer OFDM symbols, where existing technologies do not support PDSCH and ePDCCH transmissions due to the lack of defined UE-RS patterns and channel estimation for 3-OFDM-symbol DwPTS subframes.
Innovation Solution
The method involves expanding Physical Resource Blocks (PRBs) prior to a DwPTS subframe to include additional resource elements, utilizing DeModulation Reference Signals (DMRS) from a preceding subframe for channel estimation, and mapping UE-RS to support ePDCCH transmissions in DwPTS subframes with reduced OFDM symbol configurations, allowing for demodulation of signals in these subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If DwPTS subframes are configured with fewer OFDM symbols (e.g., 3 symbols), then the downlink-to-uplink switch-point periodicity is reduced and latency is decreased, but the lack of defined UE-RS patterns and channel estimation prevents PDSCH and ePDCCH transmissions
Solution Approach 1:
The patent applies preliminary action by performing channel estimation using DMRS from the preceding downlink subframe before the DwPTS subframe begins. The base station expands PRBs to include REs of the DwPTS subframe and schedules transmissions in the expanded PRBs, allowing the UE to have advance channel estimates available for demodulating signals in the DwPTS subframe even though UE-RS patterns are not defined in the DwPTS itself.
2Reliability
If existing LTE technologies are used without modification, then system compatibility is maintained, but PDSCH and ePDCCH transmissions cannot be supported in DwPTS subframes with 3 OFDM symbols
Solution Approach 1:
The patent applies parameter changes by modifying the PRB structure to expand PRBs in the downlink subframe to include REs from the DwPTS subframe. This structural parameter change allows the system to maintain compatibility with existing LTE Rel-10 while enabling new transmission capabilities. The base station configures expanded PRBs that span across the subframe boundary, and the UE uses these expanded PRBs for receiving and demodulating PDSCH and ePDCCH transmissions in the DwPTS subframe.
3Measurement precision
If DMRS from preceding subframe are used for channel estimation, then channel estimation accuracy is improved for DwPTS subframes, but the complexity of PRB expansion and scheduling increases
Solution Approach 1:
The patent applies segmentation by dividing the PRB structure into conventional PRBs in the downlink subframe and expanded PRBs that include additional REs from the DwPTS subframe. The base station configures which PRBs are expanded and schedules transmissions accordingly. This segmentation allows the system to maintain simple PRB structures where needed while introducing expanded PRBs only where necessary for DwPTS transmissions, managing complexity through selective application.
Data Source
AI summary
For use in a wireless network, a method for scheduling a Downlink Pilot Time Slot (DwPTS) subframe is provided. The method comprises expanding Physical Resource Blocks (PRBs) in a subframe prior to a DwPTS subframe to include resource elements (REs) of the DwPTS subframe, a number of OFDM symbols of the DwPTS subframe being less than or equal to a threshold OFDM symbol number. The method further comprises facilitating for a UE to demodulate REs in a DwPTS subframe based on DeModulation Reference Signals (DMRS) transmitted in a downlink subframe prior to the DwPTS subframe.