PPDU Midamble Allocation for Mixed WLAN Station Compatibility
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Solution Overview
Problem
In wireless local area networks, transmitting a PPDU with midambles to devices that do not support midambles results in resource wastage due to the need for separate transmissions, as these devices cannot estimate channels in real time, leading to errors in data reading.
Innovation Solution
A PPDU transmission method that includes a data field with a midamble subfield for devices supporting midambles and a useful information subfield for non-supporting devices, ensuring the useful information is located before the midamble symbol, and using midamble indication subfields in the U-SIG to differentiate between device types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a PPDU with midamble is transmitted to both midamble-supporting and non-supporting devices, then resource utilization efficiency improves, but data reading accuracy deteriorates for non-supporting devices
Solution Approach 1:
The data field is segmented into two separate fields: a first data field for non-midamble-supporting devices and a second data field for midamble-supporting devices. Each data field is independently structured with appropriate subfields, allowing each device type to receive optimized data without interference from the other format
Solution Approach 2:
Different quality characteristics are applied to different parts of the transmission: the first data field uses a structure suitable for non-midamble devices (with useful information subfield before midamble symbol position), while the second data field uses a structure optimized for midamble devices (with midamble subfield for real-time channel estimation). Each part has locally optimized properties for its target device type
2Reliability
If separate transmissions are used for midamble-supporting and non-supporting devices, then data reading accuracy is maintained for each device type, but resource utilization efficiency deteriorates
Solution Approach 1:
Two separate transmission streams are merged into a single PPDU transmission. The first data field and second data field are transmitted simultaneously in the same PPDU structure, allowing both device types to receive their respective optimized data in one transmission operation, thereby improving resource utilization while maintaining data accuracy
3Quantity of substance
If the useful information subfield is located after the midamble subfield, then more data can be transmitted to non-supporting devices, but channel estimation accuracy deteriorates due to Doppler effects
Solution Approach 1:
The useful information subfield is placed before the midamble subfield in the first data field, allowing non-midamble-supporting devices to receive and process critical information before the midamble symbol position. This preliminary placement ensures that data can be accurately retrieved even when devices cannot perform real-time channel estimation using midambles, particularly in Doppler scenarios where channel conditions change rapidly
Data Source
AI summary
A method includes: generating a physical layer protocol data unit PPDU, where the PPDU includes a data field; and sending the PPDU to a first station and a second station, where the first station is a station that does not support receiving a midamble, and the second station is a station that supports receiving the midamble. A second data field transmitted on a second resource unit allocated to the second station includes a midamble subfield. A first data field transmitted on a first resource unit allocated to the first station includes a useful information subfield. The useful information subfield includes useful data information, and the useful information subfield is located before a first OFDM symbol corresponding to the midamble subfield.