Relay Station Power Control for Wireless Coverage
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Solution Overview
Problem
In wireless networks with relay stations, the power difference between downlink preamble and data signals can cause automatic gain control failures in mobile stations, leading to data recovery issues and enhanced uplink interference, especially when mobile stations are far from the base station but close to the relay station.
Innovation Solution
Adjusting the transmit power of the relay station to match the power level of the downlink data and accounting for the difference in path loss and noise plus interference levels between the base station and relay station, while also adjusting the uplink transmit power of the mobile station to compensate for these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the relay station transmits downlink data at high power to reach distant mobile stations, then the coverage area is extended, but the power difference between preamble and data signals causes automatic gain control failures in mobile stations
Solution Approach 1:
The base station performs preliminary calculations to determine the appropriate relay station transmit power level before data transmission begins. The base station calculates the path loss difference between the base station-to-mobile station link and the relay station-to-mobile station link, then pre-determines the power adjustment needed to ensure the downlink data power level matches the preamble power level at the mobile station receiver, preventing AGC failures before they occur
Solution Approach 2:
The system implements a feedback mechanism where the base station receives information about the relay station's actual transmit power level and the mobile station's received signal conditions. Based on this feedback, the base station adjusts the relay station's transmit power to maintain the appropriate power relationship between preamble and data signals, ensuring continuous reliable operation of the mobile station's automatic gain control
2Power
If the relay station transmit power is increased to improve downlink data reception, then data signal strength is improved, but uplink interference is enhanced due to mismatched noise measurements
Solution Approach 1:
The system changes the parameter used for uplink power control calculations from the base station's noise measurement to the relay station's noise measurement. The base station receives the relay station's measured noise plus interference level and uses this updated parameter to calculate appropriate uplink transmit power levels for mobile stations, ensuring that uplink power control is based on the actual conditions at the relay station where uplink signals are received
3Device complexity
If the mobile station uses base station path loss for uplink power control, then power control is simplified, but uplink transmission power is incorrect when relay station is involved
Solution Approach 1:
The base station acts as an intermediary that receives noise measurement information from the relay station and performs the path loss calculation on behalf of the mobile station. Instead of requiring the mobile station to directly measure and calculate path loss to the relay station, the base station uses its received signal strength information and the relay station's noise measurements to determine the correct uplink path loss value, which it then provides to the mobile station for power control calculations
Data Source
Figure 1~2
Figure 3~7
Figure 4A
AI summary
A wireless network includes a base station and a relay station for extending wireless coverage of the base station. Downlink data is sent by the base station and relayed through the relay station to a mobile station, where the downlink data is associated with a preamble that is sent directly from the base station to the mobile station. A transmit power of the relay station is adjusted for transmitting the downlink data from the relay station to the mobile station to reduce a difference between a first power level of the preamble received at the mobile station and a second power level of the downlink data received at the mobile station. The uplink transmit power of the mobile station tfor the data sent to the relay station is adjusted to compensate for the difference in path loss from mobile station to base station and mobile station to relay station and to compensate for the difference in noise _plus_interference level at relay station compared to that of the base station.