LAA Cell Random Access via Channel Preemption Feedback
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Solution Overview
Problem
In LTE systems, the unavailability of PRACH time-frequency resources allocated by an eNB occurs when the LAA cell fails to preempt a channel or when the allowed time for channel use has expired, leading to interruptions in random access processes for user equipment accessing LAA cells.
Innovation Solution
User equipment obtains and uses first information indicating available subframes after the LAA cell successfully preempts a channel, allowing it to initiate random access when the LAA cell has preempted a channel and the PRACH resource is available, ensuring continuous access even if the initial channel is not available or has expired.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LAA cell uses channel preemption to obtain data transmission resources, then the cell can access non-licensed spectrum, but the PRACH time-frequency resource allocated by eNB becomes unavailable when channel preemption fails or the preemption period expires
Solution Approach 1:
The base station performs preliminary actions by detecting channel occupancy status and determining available PRACH resources before user equipment attempts random access. The base station proactively identifies and notifies UE of available PRACH time-frequency resources based on current channel preemption status, ensuring resources are ready before needed.
Solution Approach 2:
The base station implements a feedback mechanism by notifying user equipment of the available PRACH resources through system messages or dedicated signaling. This feedback loop allows the UE to adapt its random access attempts based on real-time channel availability information provided by the base station.
2Productivity
If the LAA cell preempts the channel for a limited period, then the channel can be shared with other cells, but the random access process is interrupted when the preemption period expires
Solution Approach 1:
The system dynamically adapts PRACH resource availability based on real-time channel preemption status. The base station continuously monitors channel occupancy and adjusts the notification of available PRACH resources accordingly, allowing the random access mechanism to flexibly respond to changing channel conditions and preemption durations.
Solution Approach 2:
The base station changes the parameter of PRACH resource availability notification based on channel preemption status. When preemption succeeds, available resources are notified; when preemption fails or expires, resources are marked as unavailable, dynamically adjusting system parameters to match current channel conditions.
3Reliability
If the base station notifies user equipment of channel preemption status, then user equipment can initiate random access when resources are available, but additional signaling overhead is introduced
Solution Approach 1:
The base station uses existing system messages and signaling mechanisms for multiple purposes: conveying system information and simultaneously notifying UE of available PRACH resources. This multi-functionality approach reduces additional signaling overhead by leveraging already-present communication channels.
Data Source
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AI summary
Embodiments of the present invention provide a random access method and an apparatus, and relate to the communications field, to resolve a problem that a PRACH resource allocated by an eNB is unavailable in a process in which UE randomly accesses an LAA cell, because the LAA cell fails to preempt a channel or a period of time in which a preempted channel is allowed for use has expired. The method includes: obtaining, by user equipment, first information, where the first information is used to indicate that a subframe of a physical random access channel PRACH resource for access to a licensed-assisted access LAA cell is one or more available subframes obtained after the LAA cell successfully preempts a channel; receiving, by the user equipment, a first indication sent by a first base station, where the first indication is used to indicate that the LAA cell has successfully preempted a channel, and the first base station is a base station that serves the LAA cell; and initiating, by the user equipment, random access according to the first information after receiving the first indication.