RACH Response Signal Transmission via DMRS and CRS Segmentation
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Solution Overview
Problem
The LTE-Advanced system faces inefficiencies in the random access procedure, particularly in MBSFN subframes, extension carriers, and CoMP transmission using a same cell ID, leading to increased error rates and congestion in RACH response transmission, especially for Release 8 compliant terminals and heterogeneous networks.
Innovation Solution
A transmission apparatus that selectively uses DMRS or CRS for RACH response transmission based on the capabilities of the terminal, setting distinct resource groups for terminals that can receive responses via DMRS or CRS, and adjusting transmission methods and resource allocation to optimize response signal transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DMRS-used data transmission is used in MBSFN subframes for LTE-Advanced terminals, then resource utilization efficiency is improved, but Release 8 terminals cannot receive the response signal
Solution Approach 1:
The patent segments the RACH response transmission into two distinct paths: one using DMRS for LTE-Advanced terminals and another using CRS for Release 8 terminals. This segmentation allows each terminal type to receive responses through its compatible reference signal, resolving the compatibility issue while maintaining high resource utilization for advanced terminals
Solution Approach 2:
The patent applies local quality by using different reference signals (DMRS vs CRS) for different terminal groups within the same MBSFN subframe. LTE-Advanced terminals receive responses with DMRS for high efficiency, while Release 8 terminals receive responses with CRS for compatibility, allowing each region of the system to have optimized quality for its specific terminal type
2Adaptability or versatility
If CRS is used for RACH response transmission in MBSFN subframes, then Release 8 terminal compatibility is improved, but resource utilization efficiency deteriorates due to CRS overhead
Solution Approach 1:
The patent segments the terminal population into two groups based on their reference signal capabilities. Release 8 terminals are served via CRS-based responses, while LTE-Advanced terminals are served via DMRS-based responses. This segmentation eliminates the need to use CRS for all terminals, thereby improving overall resource utilization efficiency while maintaining compatibility for legacy terminals
3Adaptability or versatility
If multiple RACH preambles are transmitted on the same resource, then random access capability is improved, but error rate increases due to collision
Solution Approach 1:
The patent introduces a new dimension for preamble differentiation by associating different antenna ports with different reference signal types (CRS vs DMRS). This dimensional separation allows the system to handle multiple preambles on the same time-frequency resource while directing them to different processing paths, reducing collision errors and improving both random access capability and reliability
Data Source
AI summary
In order to provide a transmission device and transmission method with which a response signal for random access preamble transmitted from a preamble transmission device is efficiently transmitted, setting unit in base station sets a first resource candidate group, which enables terminal capable of receiving a latch response transmitted by demodulation reference signal (DMRS) transmission to be selected, and a second resource candidate group, which enables terminal incapable of receiving a latch response transmitted by DMRS transmission but capable of receiving a latch response transmitted by cell-specific reference signal (CRS) transmission to be selected. Control unit selects DMRS transmission as the latch response transmission method when a resource in which latch preamble has been received is included in the first candidate group, but selects CRS transmission as the latch response transmission method when the resource is included in the second resource candidate group.