Adaptive Preamble Sets for Random Access Channel Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE, there is a challenge in balancing detector sensitivity, detection delay, and channel coherence time in the random-access mechanism used by the physical random-access channel (PRACH), while also managing receiver complexity and processing requirements.
Innovation Solution
The method involves configuring preamble sequences into sets based on uplink transmission conditions, allowing for the selection of appropriate preamble sequences that adapt to current conditions, such as signal-to-noise ratio, to optimize detection and reduce processing complexity by limiting the number of sequences detectors need to search for.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the preamble sequence length is increased to improve detector sensitivity and signal energy, then detection accuracy improves, but detection delay increases and sensitivity to channel coherence time worsens
Solution Approach 1:
The patent applies dynamics by making the preamble sequence length adaptable rather than fixed. The wireless device determines transmission conditions (such as signal-to-noise ratio, channel coherence time, and device capability) and selects an appropriate preamble sequence length dynamically. This allows the system to optimize between detection accuracy and detection delay based on actual channel conditions, resolving the contradiction between longer sequences improving sensitivity and longer sequences increasing delay.
2Adaptability or versatility
If the number of different preamble sequences is increased to improve adaptability to transmission conditions, then system versatility improves, but receiver complexity and processing requirements increase
Solution Approach 1:
The patent segments the large set of possible preamble sequences into multiple groups or sets, where each group is associated with specific transmission conditions or device capabilities. The wireless device selects an appropriate group based on current conditions, and the receiver only needs to search within the corresponding group rather than all possible sequences. This segmentation approach maintains system versatility while significantly reducing receiver complexity and processing requirements.
Solution Approach 2:
The patent changes the parameter of preamble sequence selection based on transmission conditions. Instead of using a fixed set of preambles, the system adjusts which preamble sequences are used based on factors like signal-to-noise ratio, channel coherence time, and device capability. This parameter change allows the system to adapt to different conditions while managing receiver complexity by only processing relevant sequences for current conditions.
3Reliability
If longer preamble sequences are used to increase signal energy for better detection in noisy conditions, then detector sensitivity improves, but the system becomes more sensitive to channel coherence time variations
Solution Approach 1:
The patent applies dynamics by adaptively selecting preamble sequence length based on channel coherence time conditions. When channel coherence time is short, the system uses shorter preambles to avoid exceeding the coherence window, while when coherence time is long, longer preambles are used to maximize signal energy. This dynamic adaptation resolves the contradiction between detector sensitivity and sensitivity to channel coherence time variations.
Data Source
AI summary
The present disclosure relates to random access in wireless communication systems, and in particular to transmitting, receiving, and detecting preamble sequences. A method in a wireless device for transmitting a preamble sequence to a network node is disclosed. The method comprises configuring a number of preamble sequences into two or more preamble sets, wherein each preamble set is associated with at least one respective uplink transmission condition; determining a transmission condition of an uplink from the wireless device to the network node; and selecting one out of the two or more preamble sets based on the determined transmission condition to be a selected preamble set, and a preamble sequence from the selected preamble set to be a selected preamble sequence; as well as transmitting the selected preamble sequence on the uplink.