Wireless Device Random Access Preamble Transmission in TDD Systems
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Solution Overview
Problem
In time division duplex (TDD)-based wireless communication systems, particularly in 3GPP LTE, half-duplex wireless devices face challenges in transmitting random access preambles due to varying UL-DL configurations across multiple serving cells, leading to interference and difficulties in PRACH transmission when UL propagation differences occur or different configurations are applied.
Innovation Solution
A method where a wireless device configures multiple serving cells with different UL-DL configurations, selects a suitable UL subframe for random access preamble transmission, and adjusts the preamble length if it exceeds the subframe range, ensuring transmission within the UL subframe, even if adjacent subframes are DL subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple serving cells with different UL-DL configurations are configured, then data rate is improved, but interference occurs and PRACH transmission becomes difficult
Solution Approach 1:
The patent applies preliminary action by determining the relationship between UL subframes of different serving cells before performing PRACH transmission. The wireless device identifies which UL subframes may cause interference with DL subframes of other cells in advance, and selects appropriate UL subframes for PRACH transmission based on this pre-determined relationship, thereby avoiding interference while maintaining multiple serving cells for high data rate
Solution Approach 2:
The patent applies local quality by allowing different UL-DL configurations to be applied to different serving cells individually. Each serving cell can have its own configuration optimized for local conditions, while the wireless device selectively performs PRACH transmission on UL subframes that do not cause interference in other cells, thus maintaining both high data rate and avoiding interference
2Reliability
If random access preamble length is increased, then transmission reliability is improved, but it exceeds UL subframe range causing interference
Solution Approach 1:
The patent applies parameter changes by adjusting the PRACH transmission parameters based on the determined UL subframe relationships. When a longer preamble would exceed the UL subframe range and cause interference, the device modifies transmission parameters such as selecting a different UL subframe or adjusting preamble format, thereby maintaining transmission reliability while avoiding interference with DL subframes of other serving cells
3Productivity
If UL transmission and DL reception are performed simultaneously in full duplex, then capacity is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies segmentation by dividing the operation into separate UL transmission and DL reception phases in time, rather than performing them simultaneously. The wireless device determines appropriate UL subframes for PRACH transmission by analyzing the UL-DL configuration relationships, ensuring that UL transmission does not overlap with DL reception in other cells, thus maintaining half-duplex operation while achieving effective communication capacity
Data Source
AI summary
Provided is a method and an apparatus for transmitting a random access preamble in a time division duplex (TDD)-based wireless communication system. A wireless device selects an UL subframe in which a random access preamble is to be transmitted in a first serving cell. If the next subframe following the selected UL subframe is a DL subframe and the length of the random access preamble exceeds the UL subframe, the random access preamble may be generated such that the length of the random access preamble may not exceed the UL subframe.