Fast-Slotted RPMA Power Control for Large Spreading Factors
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Solution Overview
Problem
In half-duplex random phase multiple access (RPMA) communication systems, maintaining equivalent power levels for multiple simultaneous transmitters is challenging, especially with changing signal propagation characteristics, as larger spreading factors result in fewer opportunities for controlled power adjustments due to longer frame transmission times.
Innovation Solution
Implementing a fast-slotted power control system that subdivides uplink and downlink transmissions into smaller 'fast slots' independent of frame rate, allowing for more frequent power control updates and maintaining high receive sensitivity through a large spreading factor and process gain, using open-loop power control based on received power measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large spreading factor is used to increase process gain and receive sensitivity, then receive sensitivity is improved, but the frame transmission time increases and power control update opportunities decrease
Solution Approach 1:
The frame structure is segmented into multiple subframes, with each subframe containing multiple slots. This segmentation allows the system to maintain a large spreading factor for high receive sensitivity while creating more frequent power control update opportunities within each subframe, effectively resolving the contradiction between long frame duration and frequent power control updates.
2Measurement precision
If a large spreading factor is used to increase process gain, then receive sensitivity is improved, but the number of power control update opportunities decreases
Solution Approach 1:
By dividing the frame into subframes and slots, the system creates multiple power control update points within each frame transmission. Nodes can perform open-loop power control adjustments at each slot boundary based on received power measurements, maintaining high receive sensitivity through large spreading factors while achieving frequent power control updates.
Solution Approach 2:
The system implements periodic power control updates at each slot boundary within subframes. This periodic structure allows nodes to regularly adjust transmit power based on received power measurements from access point transmissions, ensuring frequent power control opportunities even with large spreading factors that extend frame duration.
3Device complexity
If half-duplex transmissions are used to divide uplink and downlink slots, then system simplicity is improved, but power control responsiveness deteriorates in changing propagation conditions
Solution Approach 1:
The half-duplex frame structure is segmented into multiple subframes and slots, creating more frequent transmission opportunities. This segmentation allows power control adjustments to occur more frequently within each half-duplex cycle, improving responsiveness to changing propagation conditions while maintaining the simplicity of half-duplex operation.
Solution Approach 2:
The system dynamically adjusts transmit power at each slot boundary based on open-loop power control measurements. This dynamic power adjustment capability allows the system to respond to changing propagation conditions in real-time, improving power control responsiveness while maintaining half-duplex simplicity through structured subframe and slot organization.
Data Source
AI summary
A technique and system is disclosed for controlling power in a spread spectrum system. A fast slot of a frame is received where the frame is divided into a number of fast slots. The received power is measured on the fast slot. A second fast slot is transmitted at a second time with a transmit power setting and a variable spreading factor. The transmit power setting and the variable spreading factor is adjusted based on the received power. The variable spreading factor affects the total number of fast slots that are transmitted.