DRS Multiplexing in LAA Transmission Bursts
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Solution Overview
Problem
In wireless communication systems using Licensed-assisted access (LAA) for LTE in unlicensed spectrum, the challenge lies in multiplexing Discovery Reference Signals (DRS) within a transmission burst, particularly when data transmission collides with DRS measurement timing configuration (DMTC), and allocating Physical Downlink Shared Channel (PDSCH) in subframes containing DRS.
Innovation Solution
Configuring DRS measurement timing configuration with periodicity and transmitting DRS in complete subframes of Transmission Opportunity (TxOP), allocating PDSCH in physical resource blocks outside central blocks to ensure bandwidth and continuity, and using reserved resource elements for system information transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DRS is transmitted during a DMTC period that collides with data transmission in a TXOP, then DRS measurement can be performed, but it causes collision with data transmission and fractional subframes
Solution Approach 1:
The patent segments the DMTC period into multiple candidate positions for DRS transmission. When a collision with data transmission is detected, the system selects an alternative candidate position within the same DMTC period, thereby separating the DRS transmission from the conflicting data transmission while maintaining the measurement functionality.
Solution Approach 2:
The patent introduces dynamic selection of DRS transmission timing based on channel conditions and data transmission status. The network entity dynamically determines whether to transmit DRS at the configured DMTC position or at an alternative candidate position within the same DMTC period, allowing adaptive resolution of collisions between DRS and data transmission.
2Productivity
If DRS is transmitted in a fractional subframe, then DRS can be transmitted within the TXOP, but the fractional subframe structure causes complexity in resource allocation and transmission
Solution Approach 1:
The patent allows DRS transmission in complete subframes within the TXOP even if this means using only part of the available TXOP duration. By restricting DRS to complete subframes rather than allowing fractional subframe usage, the system simplifies resource allocation and transmission processing while maintaining adequate DRS transmission capability.
3Productivity
If central PRBs are used for PDSCH allocation in DRS subframe, then bandwidth utilization is maximized, but it interferes with DRS transmission and system information delivery
Solution Approach 1:
The patent segments the frequency resources in a DRS subframe by designating central PRBs exclusively for DRS and system information transmission, while allocating non-central PRBs for PDSCH. This frequency domain segmentation prevents interference between DRS and data transmission while maintaining efficient bandwidth utilization across different resource blocks.
Solution Approach 2:
The patent applies different resource allocation strategies to different frequency regions within the same subframe. Central PRBs are designated with special properties for carrying DRS and system information, while non-central PRBs use standard PDSCH allocation. This local differentiation ensures that critical signaling resources are protected while maintaining overall system efficiency.
Data Source
AI summary
Methods and apparatus are provided for multiplexing DRS within a transmission burst for opportunistic spectrum access. In one novel aspect, DRS is not transmitted in a fractional subframe within a TXOP. In one embodiment, if the starting fractional subframe, which contains initial signal, occurs in a configured DMTC, DRS is transmitted in the first subframe next to the starting fractional subframe. In another embodiment, if DMTC starts from a complete subframe within a TXOP, DRS is transmitted in the first candidate position within a DMTC. In another novel aspect, in the DRS subframe, PDSCH is allocated in the PRBs outside the central PRBs (six or twenty-five PRBs). In one embodiment, the reservation signal can be used to satisfy the requirement of occupied bandwidth and continuity transmission. In another embodiment, the free REs in central PRBs carry the system information when required on the unlicensed band.