Frequency Hopping Interference Mitigation in White Space Networks
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Solution Overview
Problem
Wireless networks operating in white space, particularly in the UHF TV band, face interference challenges due to variable bandwidth and coexistence with TV broadcasts, where existing frequency hopping mechanisms do not effectively address localized interference affecting specific terminals.
Innovation Solution
A communication device and terminal that determine if a terminal is subject to interference on a frequency in the hopping sequence, allowing them to skip or reschedule communications to avoid that frequency, thereby minimizing interference and improving communication reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency hopping is used to minimize interference to TV reception, then TV reception quality is improved, but communication reliability may deteriorate due to localized interference affecting specific terminals on specific frequencies
Solution Approach 1:
The system applies local quality by identifying terminals experiencing localized interference on specific frequencies and applying interference mitigation measures selectively to those terminals rather than globally. The base station determines which terminals are affected by localized interference and schedules their communications to avoid the interfered frequencies, while other terminals continue using the standard frequency hopping sequence without disruption.
Solution Approach 2:
The system implements dynamics by making the frequency hopping sequence adaptive and flexible. Instead of using a fixed hopping sequence for all terminals, the system dynamically adjusts the sequence for specific terminals based on detected localized interference conditions. The base station can modify the hopping sequence in real-time based on feedback from terminals about their reception quality and interference experiences.
2Object-affected harmful factors
If the bandwidth of the whitespace transmitter is reduced to a small fraction of the DTV channel bandwidth, then interference to TV reception is minimized, but the terminal becomes more sensitive to multipath fading
Solution Approach 1:
The system applies periodic action through frequency hopping, where the transmitter periodically changes frequencies according to a hopping sequence. This periodic frequency changing ensures that no single frequency is used continuously, reducing the chance of long-term fades affecting the entire communication. The periodic nature of hopping provides diversity over time, complementing the narrowband transmission approach.
Solution Approach 2:
The system implements preliminary action by proactively selecting frequency hopping sequences and time slots that avoid known interfered frequencies. The base station determines localized interference conditions in advance and pre-schedules communications to avoid problematic frequencies, rather than reacting to interference after it occurs. This preliminary planning prevents communication failures before they happen.
3Object-affected harmful factors
If the white space database is used to determine available channels and power levels, then coexistence with TV broadcasts is ensured, but localized interference affecting specific terminals cannot be detected or avoided
Solution Approach 1:
The system implements feedback by having terminals report their reception quality and interference experiences back to the base station. The base station uses this feedback information to identify localized interference patterns that affect specific terminals. The feedback loop enables the system to detect and respond to localized interference conditions that the database cannot identify, allowing dynamic adjustment of frequency assignments.
Solution Approach 2:
The base station acts as an intermediary between the white space database and the terminals. While the database provides general channel availability information at the cell level, the base station uses this information and supplements it with local measurements and terminal feedback to make informed decisions about frequency assignments. The base station mediates between the coarse-grained database information and the fine-grained localized interference conditions.
Data Source
AI summary
A communication device for communicating with a plurality of terminals using a frequency hopping sequence, the communication device being configured to determine that one of the plurality of terminals is subject to interference on a frequency in the frequency hopping sequence and to, in response to that determination, schedule communication with that terminal to avoid that frequency.