DM-RS Scheduling for Uplink Spectrum Efficiency
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Solution Overview
Problem
Current LTE specifications are not optimized for small cell environments, leading to inefficient resource utilization due to high overhead from demodulation reference signals (DM-RS), which limits the potential system throughput and spectrum efficiency.
Innovation Solution
The proposed solution involves dynamically adjusting the DM-RS transmission schedule by reducing the number of DM-RS transmissions, altering their mapping within subframes, and using interlaced frequency division multiplexing to minimize resource usage, allowing for more efficient use of resources in both time and frequency domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DM-RS is transmitted in every uplink time slot with standard mapping, then channel estimation accuracy is maintained, but resource overhead increases and spectrum efficiency decreases
Solution Approach 1:
The patent extracts and removes unnecessary DM-RS transmissions from the uplink time slot structure. Specifically, it eliminates DM-RS from certain time slots or reduces the number of DM-RS per time slot, keeping only the essential reference signals needed for channel estimation while discarding redundant ones, thereby reducing resource overhead while maintaining necessary measurement precision.
Solution Approach 2:
The patent applies partial action by transmitting DM-RS only in certain time slots or at reduced density rather than in every time slot with full density. This partial transmission strategy provides sufficient channel estimation accuracy for the specific small cell deployment scenario while significantly reducing the quantity of DM-RS resources consumed.
2Adaptability or versatility
If standard DM-RS mapping is used in LTE, then compatibility with existing systems is maintained, but spectrum efficiency is limited in small cell environments
Solution Approach 1:
The patent introduces dynamic DM-RS mapping that can adapt to different small cell deployment scenarios. The mapping configuration is no longer fixed but can be adjusted based on channel conditions, traffic patterns, and specific deployment requirements, allowing the system to optimize spectrum efficiency while maintaining compatibility through configurable parameters that work with existing LTE infrastructure.
Solution Approach 2:
The patent applies different DM-RS mapping strategies to different local conditions in small cell environments. Instead of a uniform mapping approach, the system can apply optimized mapping patterns specific to particular time slots, frequency resources, or spatial conditions, thereby improving spectrum efficiency locally while maintaining overall system compatibility.
3Reliability
If DM-RS is transmitted with high density, then demodulation reliability is improved, but resource utilization efficiency decreases
Solution Approach 1:
The patent uses copying of essential DM-RS patterns at reduced density rather than transmitting full-density DM-RS in every time slot. By copying only the critical reference signal structures where most needed and omitting redundant copies, the system maintains sufficient demodulation reliability while improving resource utilization efficiency through selective replication of essential elements.
Data Source
AI summary
Methods and systems are disclosed for reducing control signaling in uplink transmissions. A device, such as a wireless transmit/receive unit, may determine to use a demodulation reference signal (DM-RS) transmission schedule out of a plurality of DM-RS transmission schedules. The DM-RS transmission schedule may be characterized by a DM-RS transmission being mapped to a single orthogonal frequency-division multiplexing (OFDM) symbol per subframe of a data stream. The DM-RS transmission schedule may be characterized by a DM-RS transmission being mapped to a first subset of subcarriers of an OFDM symbol of a subframe of a data stream and Physical Uplink Shared Channel (PUSCH) transmission or Physical Uplink Control Channel (PUCCH) control information being mapped to a second set of subcarriers of the OFDM symbol. The first set of subcarriers may be different than the second set of subcarriers. The data stream may be transmitted according to the DM-RS transmission schedule.