Random-Access Modulation Format Selection for 5G Coverage and Overhead
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Solution Overview
Problem
In wireless communications, particularly in 5G systems, the random-access procedure faces challenges due to the differences in Peak to Average Power Ratio (PAPR) between OFDM and DFTS-OFDM, leading to coverage issues and resource overhead inefficiencies.
Innovation Solution
A method is introduced where a network node transmits an indication of a modulation format to wireless devices, allowing them to configure the modulation format for random access message 3 transmissions. This selection can be based on network conditions, receiver capabilities, link budget, and signal-to-noise ratio, enabling the use of either OFDM or DFTS-OFDM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM is used for message 3 transmission, then resource overhead is reduced and receiver complexity is lowered, but coverage is degraded due to higher PAPR requiring lower transmit power
Solution Approach 1:
The patent implements dynamic modulation format selection where the network node can indicate different modulation formats (OFDM or DFTS-OFDM) for message 3 transmission based on current network conditions, UE capabilities, and coverage requirements. This dynamic adaptation allows the system to switch between low-overhead OFDM and high-coverage DFTS-OFDM as needed, resolving the contradiction between resource efficiency and coverage reliability.
2Reliability
If DFTS-OFDM is used for message 3 transmission, then coverage is improved due to lower PAPR allowing higher transmit power, but resource overhead increases and device complexity rises
Solution Approach 1:
The system dynamically selects between DFTS-OFDM and OFDM based on coverage requirements and network conditions. When coverage is the priority (e.g., cell edge users), DFTS-OFDM is selected despite higher resource overhead. When resource efficiency is more important (e.g., good coverage conditions), OFDM is selected. This dynamic approach resolves the contradiction by allowing context-dependent optimization.
3Adaptability or versatility
If the network supports both OFDM and DFTS-OFDM receivers, then adaptability to different modulation formats is achieved, but device complexity increases
Solution Approach 1:
The network node dynamically indicates which modulation format the UE should use for message 3 transmission, allowing the UE to optimize its transmitter for a single format while the network maintains capability to receive both formats. This resolves the contradiction by placing the adaptability burden on the network side (which already has complex receivers) rather than requiring UEs to support multiple reception modes.
Data Source
AI summary
A method in a network node for managing random-access procedures with a plurality of wireless devices. The method comprising transmitting an indication of a modulation format to one or more of the plurality of wireless devices to configure the modulation format for a random access message 3 transmission from the one or more wireless devices.