Wireless Outstation Trigger Timing for TDD Uplink Synchronization
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Solution Overview
Problem
Fixed wireless access networks using Wi-Fi standards face challenges in accommodating pre-determined time division duplex schedules, limiting the use of commercially available chipsets and preventing efficient implementation of features like Triggered Uplink Access (TUA) due to varying propagation distances and times.
Innovation Solution
A wireless outstation generates a locally triggered frame based on a predetermined time division duplex schedule, allowing simultaneous uplink message transmission by outstations, using MU-MIMO and OFDMA, and integrating with standard chipsets by providing the trigger frame at baseband or modulated onto a carrier frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trigger frame is transmitted from the access point to trigger uplink message transmission, then the uplink message timing can be controlled centrally, but only a limited range of propagation times can be tolerated due to the predetermined time window for reception at the access point
Solution Approach 1:
Instead of the access point generating and transmitting the trigger frame to control uplink timing, the invention inverts the approach by having each outstation generate its own trigger frame locally based on a predetermined time division duplex schedule. This local generation allows each outstation to independently calculate the appropriate transmission timing that accounts for its specific propagation delay to the access point, thereby accommodating a wide range of propagation times while maintaining reliable timing control.
2Ease of manufacture
If commercially available Wi-Fi chipsets are used in a fixed wireless access network, then standard Wi-Fi message formats can be utilized, but the pre-determined time division duplex schedule required for efficient fixed wireless operation cannot be accommodated
Solution Approach 1:
The invention changes the operational parameters of the Wi-Fi chipset by having the outstation generate the trigger frame locally with timing information derived from a predetermined time division duplex schedule specific to fixed wireless access networks. This parameter change allows the standard Wi-Fi chipset to operate in a fixed wireless access network mode, accommodating the required TDD schedule while maintaining compatibility with commercially available hardware.
3Productivity
If uplink messages are transmitted by outstations with wide ranging propagation times to arrive simultaneously at the access point, then efficient resource allocation can be achieved, but the reception timing window at the access point becomes difficult to satisfy when using access point-triggered transmission
Solution Approach 1:
The invention applies preliminary action by having each outstation pre-calculate its uplink message transmission timing based on a predetermined time division duplex schedule and its measured propagation delay to the access point. Each outstation generates a local trigger frame that schedules its uplink transmission in advance, ensuring that messages from outstations with widely varying propagation times will arrive simultaneously at the access point within the reception time window, thereby achieving both efficient resource allocation and precise timing synchronization.
Data Source
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AI summary
A wireless outstation is operated in a fixed wireless access network comprising an access point and a plurality of wireless outstations, the wireless outstation comprising a receiver circuit (11) configured to receive a message (2) from the access point comprising a trigger frame to trigger transmission of an uplink message (5) from the wireless outstation. The trigger frame (4) is generated at the wireless outstation based on a predetermined time division duplex schedule and the generated trigger frame (4) is provided as an input to the receiver circuit (11).