PRACH Preamble Configuration for Unlicensed Carrier Access
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Solution Overview
Problem
The challenge is to enable efficient coexistence of LTE systems with Wi-Fi in unlicensed frequency bands, particularly in reducing access time delay for user equipment, as traditional LTE systems lack a Listen Before Talk (LBT) mechanism to avoid collisions and detect idle channels effectively.
Innovation Solution
A preamble configuration method is introduced, where a base station configures PRACH parameters including subframe location, CCA interval, channel detection mechanism, and preamble format information, allowing user equipment to detect idle states and send preambles efficiently, thereby adapting to dynamic LAA frame structures and minimizing uplink subframe occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional LTE systems transmit without monitoring rules in unlicensed frequency bands, then spectrum efficiency is improved, but interference to Wi-Fi devices increases and coexistence deteriorates
Solution Approach 1:
The patent changes the transmission parameters by introducing LBT (Listen Before Talk) mechanisms and dynamic channel access control. The base station configures PRACH parameters including subframe location, CCA interval, and channel detection mechanisms that allow the system to adapt transmission behavior based on channel conditions, thereby reducing interference to Wi-Fi while maintaining efficient spectrum utilization.
2Object-affected harmful factors
If LTE systems implement LBT mechanism to coexist with Wi-Fi, then coexistence is improved, but access time delay increases due to lack of preamble sending mechanism
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple preamble formats (format 0, 1, 2, 3, 4) and their corresponding time durations at the base station before actual random access occurs. The UE can select from these pre-configured formats based on channel conditions, avoiding the need to negotiate preamble parameters during the access process and thereby reducing access delay.
Solution Approach 2:
The patent introduces dynamic preamble selection where the UE can choose different preamble formats (0-4) with different time durations based on real-time channel conditions and LBT outcomes. This dynamic adaptation allows the system to optimize access time by selecting shorter preambles when appropriate while maintaining compatibility with LBT requirements.
3Productivity
If multiple preambles are configured in a subframe to reduce access delay, then random access efficiency is improved, but uplink subframe occupation increases
Solution Approach 1:
The patent applies partial action by configuring multiple preambles (M preambles) within a single subframe rather than requiring separate subframes for each preamble transmission. This allows the system to achieve faster random access by parallelizing preamble transmissions while occupying only one uplink subframe, thus improving access efficiency without proportionally increasing resource occupation.
Data Source
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Figure 2
AI summary
An embodiment of the present disclosure provides a preamble configuration method on an unlicensed carrier, the method includes: configuring a Physical Random Access Channel ( PRACH) configuration message, the PRACH configuration message including subframe location information, first Clear Channel Assessment (CCA) interval location information, a channel detection mechanism, preamble format information, and preamble sending location information. The subframe location information indicates a location of a subframe where M to-be-transmitted preambles are located. The first CCA interval location information represents a location of a CCA interval before each preamble in the M to-be-transmitted preambles on the subframe or on a previous subframe of the subframe. The channel detection mechanism is used for indicating whether user equipment detects that the unlicensed carrier is in an idle state. The preamble format information indicates that the to-be-transmitted preambles are format 4 preambles. Sending control signaling carrying the PRACH configuration message to the user equipment. The present disclosure also provides a preamble transmission method and a related device. The present disclosure can reduce the time delay of access.