RACH Message Format for Extended Range Wireless Systems
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Solution Overview
Problem
Conventional wireless communication systems face challenges in extending the range of random access channels beyond 15 km without increasing receiver complexity or introducing inter-symbol interference, especially as proposed systems aim for coverage areas up to 100 km.
Innovation Solution
A method involving a base station that accumulates signal energy during offset time intervals within a 2 ms transmission time interval, using two processing threads to analyze signal energy and detect random access channel messages with a flexible RACH structure that includes a cyclic prefix, a preamble, and a guard time, allowing for extended coverage with reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the transmission time interval is increased to 2 ms to extend coverage area to 100 km, then the coverage range is improved, but the receiver complexity increases due to the need to continuously monitor and search for preambles over a longer time interval
Solution Approach 1:
The 2 ms transmission time interval is segmented into multiple non-overlapping time windows, each window corresponding to a specific delay range. The receiver only needs to monitor and search for preambles within the current active window rather than continuously monitoring the entire 2 ms interval, thereby reducing receiver complexity while maintaining extended coverage capability.
Solution Approach 2:
The method pre-calculates and defines multiple time windows with predetermined delay ranges before reception. This preliminary structuring allows the receiver to efficiently jump to the appropriate monitoring window based on expected signal arrival times, avoiding the need to search the entire extended time interval and reducing computational complexity.
2Object-affected harmful factors
If the guard time is increased to reduce inter-symbol interference for extended range, then the inter-symbol interference is reduced, but the time available for data transmission decreases
Solution Approach 1:
Different time windows are allocated with different guard time durations based on their specific delay ranges. Windows corresponding to longer delays have longer guard times to prevent inter-symbol interference, while windows with shorter delays use shorter guard times, optimizing the balance between interference reduction and data transmission efficiency for each local time segment.
3Area of stationary object
If the cyclic prefix duration is increased to support larger coverage areas, then the coverage range is extended, but the time available for preamble and data transmission decreases
Solution Approach 1:
The cyclic prefix duration is segmented and varied across different time windows based on their delay requirements. Time windows corresponding to larger coverage areas have longer cyclic prefixes, while windows for shorter ranges use shorter cyclic prefixes, allowing the system to support extended coverage without uniformly reducing transmission time across all windows.
Data Source
AI summary
The present invention provides a method for transmitting and receiving random access channel messages in an extended range wireless communication system. One embodiment of the method may include accumulating, at a base station, signal energy received during a first portion of a transmission time interval. The method may also include accumulating, at the base station, signal energy received during a second portion of the transmission time interval. The first and second portions are offset from the start or end of the transmission time interval by selected delay intervals. The method may further include detecting the message(s) based on the signal energy accumulated during the first and second portions of the transmission time interval.