Relay Station Transmission Power Control for Boundary Interference
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Solution Overview
Problem
In wireless communications systems with relay stations, performance degradation occurs due to inter-cell and inter-relay-station interference, particularly at cell and relay station boundary regions, limiting improvements in these areas.
Innovation Solution
Implementing relay stations that support multiple carriers with varying transmission power levels and schedules, where access terminals in boundary regions are prioritized for high power carriers and time intervals, and using coordinated power profiles to minimize interference between adjacent relay stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay stations are deployed to improve performance at cell boundary regions, then performance at cell boundaries is improved, but inter-relay-station interference is introduced causing performance degradation in relay station boundary regions
Solution Approach 1:
The patent applies local quality by assigning different transmission power levels to different carriers based on the specific needs of boundary region terminals. Relay stations transmit at higher power levels on certain carriers to serve terminals in their own boundary regions while lower power levels are used on other carriers to reduce interference to adjacent relay stations' boundary terminals. This localized power adjustment resolves the contradiction by improving service to local boundary terminals without causing excessive interference to neighboring areas.
Solution Approach 2:
The patent changes the transmission power parameter dynamically based on carrier frequency and terminal location. Different carriers are assigned different power levels (e.g., F1 at P1, F2 at P2, F3 at P3 where P1<P2<P3), and relay stations adjust which power level to use on which carrier based on whether the target terminal is in a boundary region. This parameter change strategy allows the system to improve boundary region performance while controlling inter-relay-station interference through selective power level assignment.
2Object-affected harmful factors
If multiple carriers are used with different power levels, then interference mitigation is achieved, but device complexity increases
Solution Approach 1:
The patent implements periodic action through the use of frame structure where different power levels are applied periodically across different carriers. The system uses a predefined pattern (e.g., first carrier at first power level, second carrier at second power level, third carrier at third power level) that repeats across transmission frames. This periodic structure simplifies the complexity by providing a regular, predictable pattern rather than requiring complex real-time decision-making, while still achieving interference mitigation through the varied power levels.
3Productivity
If access terminals in boundary regions are prioritized for high power carriers, then throughput for boundary terminals is improved, but interference to non-boundary terminals increases
Solution Approach 1:
The patent applies local quality by differentiating service quality based on terminal location. Boundary region terminals receive high power level service on specific carriers to improve their throughput, while non-boundary terminals receive service at lower power levels. This localized quality adjustment ensures that high power transmission is applied only where needed (at relay station boundaries) rather than universally, thus improving boundary terminal throughput without unnecessarily increasing interference to non-boundary terminals.
Data Source
AI summary
Methods and apparatus relating to communicating in a system including relay stations are described. Various described methods and apparatus are directed to improved performance and/or mitigating interference in relay station boundary areas. Relay station transmission power is controlled based on at least one of time or frequency such that a transmission power level for a frequency is varied in a predetermined manner with time or such that different transmission power levels are used for different carrier frequencies. Different adjacent relay stations are intentionally configured to use different transmission power levels for the same carrier and/or have different time varying transmission power level profiles for the same carrier. A relay station performs access terminal scheduling based on access terminal location with respect to relay station boundary regions and transmission power level information.