PRACH Preamble Slot Allocation Using Cyclic Shifts and Start Positions
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in configuring short PRACH preamble formats that utilize only a fraction of a slot, leading to high overhead and interference between preambles.
Innovation Solution
The configuration of PRACH preambles is optimized by combining cyclic shifts and starting positions within a slot with a single root sequence, and additional sequences are used if necessary to minimize overhead and interference, using techniques such as Zadoff-Chu and m-sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If short PRACH preamble formats are used that occupy only a fraction of a slot, then time resource utilization is improved, but overhead and interference between preambles increase
Solution Approach 1:
The patent segments the slot into multiple starting positions for different PRACH preambles. Each preamble can start at different positions within the slot (e.g., first quarter, second quarter, third quarter, fourth quarter), allowing short preambles to be distributed throughout the slot rather than concentrated at the beginning. This segmentation reduces interference between preambles while maintaining high time resource utilization.
Solution Approach 2:
The patent introduces a time-position dimension for preamble allocation by combining cyclic shifts with starting positions within the slot. Instead of only using frequency separation, the solution adds temporal positioning as another dimension, where preambles are separated both in frequency (cyclic shifts) and time (starting positions), thereby reducing interference while improving resource utilization.
2Productivity
If multiple random access resources are allocated per slot, then random access capacity is improved, but resource overhead increases
Solution Approach 1:
The patent makes a single slot serve multiple random access functions by allocating multiple starting positions within that same slot for different preambles. Instead of requiring separate slots or extensive frequency resources for each preamble, the solution allows one slot to handle multiple random access attempts through temporal multiplexing of starting positions, reducing overall resource overhead while increasing access capacity.
Solution Approach 2:
The patent employs periodic patterns in allocating starting positions and cyclic shifts for different preambles. By using regular, periodic structures for preamble allocation across time and frequency, the system efficiently manages multiple random access resources within a slot while maintaining predictable resource usage patterns that minimize overhead.
Data Source
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AI summary
An example method for transmitting a random access preamble comprises selecting (502) a random access preamble configuration from a plurality of predetermined random access preamble configurations. The method further includes determining (504) a time interval in which to transmit the random access preamble. The method further comprises transmitting (506) the random access preamble according to the selected random access preamble configuration. Each of the plurality of random access preamble configurations comprises a combination of (a) a single root sequence from a predetermined set of one or more root sequences, (b) a single cyclic shift of a predetermined plurality of cyclic shifts for the root sequence, and (c) a single starting position of two or more predetermined starting positions within time intervals allocated for random access preamble transmission.