Downlink Discontinuous Transmission CRS Segmentation
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Solution Overview
Problem
Current LTE wireless communication systems face inefficiencies in downlink discontinuous transmission modes, particularly with the use of common reference signals (CRS), which lead to overhead and reduced spectral efficiency, and lack support for robust transmission modes like transmit diversity and open loop MIMO when CRS is not available in all subframes.
Innovation Solution
Implementing a method in base stations and user equipment to use CRS in conjunction with discontinuous transmission, specifically transmitting CRS only in certain subframes for synchronization and RRM measurements, while allowing for transmit diversity and open loop MIMO modes by signaling which subframes contain CRS and using CSI-RS for channel state information feedback, enabling dynamic on/off behavior of CRS transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common reference signals (CRS) are transmitted in all subframes, then reliable channel estimation and demodulation are maintained, but overhead increases and spectral efficiency decreases
Solution Approach 1:
The patent segments the transmission of common reference signals by subframe type. CRS are transmitted in non-DTX subframes to enable reliable channel estimation, but omitted in DTX subframes to reduce overhead. This segmentation allows the system to adapt reference signal transmission to actual data transmission needs, resolving the contradiction between reliability and overhead.
Solution Approach 2:
The patent implements dynamic CRS transmission behavior where the presence of CRS is determined by the DTX state of the subframe. In non-DTX subframes, CRS are transmitted for reliable demodulation; in DTX subframes, CRS are omitted to reduce overhead. This dynamic adaptation allows the system to optimize the trade-off between reliability and overhead based on actual transmission requirements.
2Productivity
If CRS are omitted in DTX subframes, then spectral efficiency improves, but support for robust transmission modes like transmit diversity and open loop MIMO is lost
Solution Approach 1:
The patent segments transmission modes into those that can operate without CRS (DMRS-based modes like TM9-TM10) and those that require CRS (CRS-based modes like TM1-TM8). In DTX subframes, only CRS-independent modes are supported, while in non-DTX subframes, all transmission modes including robust CRS-based modes are available. This segmentation resolves the contradiction by allowing spectral efficiency improvement in DTX subframes while maintaining transmission mode versatility in non-DTX subframes.
Solution Approach 2:
The patent changes the available transmission mode parameter based on the DTX state. In DTX subframes without CRS, the system restricts to DMRS-based transmission modes. In non-DTX subframes with CRS present, the system enables all transmission modes including robust CRS-based transmit diversity and open loop MIMO modes. This parameter change approach allows the system to optimize spectral efficiency when CRS are omitted while maintaining full transmission mode support when CRS are available.
3Adaptability or versatility
If CRS are transmitted continuously, then backward compatibility is maintained, but energy consumption increases
Solution Approach 1:
The patent segments CRS transmission by subframe type, transmitting CRS only in non-DTX subframes where data is actually sent. In DTX subframes where no data is transmitted, CRS are omitted to save energy. This segmentation maintains backward compatibility in subframes where UEs need to receive data while reducing energy consumption in subframes where the base station can sleep or reduce transmission activity.
Solution Approach 2:
The patent implements periodic CRS transmission aligned with the DTX pattern. CRS are transmitted periodically in non-DTX subframes to maintain compatibility with UEs that expect CRS, but are omitted in DTX subframes to reduce energy consumption. This periodic action pattern allows the base station to conserve energy during low-activity periods while maintaining compatibility during active transmission periods.
Data Source
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AI summary
A method and system for downlink discontinuous transmission are provided. In one embodiment, a base station includes a memory, a processor and a transmitter. The memory stores information to be transmitted in a subset of sub frames to a UE. The information includes transmission mode configuration information. The processor operates to configure the transmitter according to a selected transmission mode configuration that includes one of a transmit diversity mode and a MIMO mode, and configures the transmitter to transmit discontinuously and include CRS in only a subset of sub frames.