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Wireless Interference Mitigation

Estimated read time: 5 minutes
Difficulty: easy

Wireless communication is a vital component of our everyday routine. It facilitates phone calls, internet browsing, video and music streaming, and home automation. Despite its benefits, wireless signals and devices can interfere with each other, resulting in dropped calls, slower speeds, and reduced audio quality. Interference is often caused by the simultaneous use of the same bandwidth or frequency by different devices. Thankfully, there exist numerous techniques to mitigate wireless interference, ensuring smooth communication and uninterrupted connectivity. The ones we will describe in this article are beamforming, frequency hopping, dynamic frequency selection, channel bonding, Listen Before Talk, error correction coding, packet fragmentation, and selective retransmission.

Beamforming is a technique that is used in wireless communication systems to improve signal strength and reduce interference. It involves directing the wireless signal toward a specific location instead of broadcasting it in all directions. By doing this, the signal is focused on the intended receiver and can be improved, leading to higher quality and more reliable communication. Imagine you are trying to talk to a friend across a crowded room, but there is a lot of noise from other people talking. You might cup your hands around your mouth and direct your voice toward your friend, making it easier for him to hear you. This is similar to how beamforming works in wireless communication.

Beamforming can be further improved with the use of directional antennas, which allow for even more precise targeting of wireless signals. By combining beamforming with directional antennas, interference can be reduced even further and signal strength can be increased. This is particularly useful in scenarios where there are multiple wireless devices in the same area, such as in a crowded public space or office building.

Frequency hopping is a technique that is widely used in wireless communication systems. For example, FHSS (Frequency Hopping Spread Spectrum) is a technique used in Bluetooth technology to avoid interference from other wireless devices. Dynamic frequency selection is also an important technique that is used in wireless communication to select the least congested frequency for transmission. The probability of successful transmission with frequency hopping can be calculated using the formula

Mathematical graph
where k is the number of hops and I is a metric proportional to the interference.

Frequency hopping can be compared to a driver who changes lanes on the highway to avoid traffic congestion. Just like how a driver will switch lanes to find a faster route, frequency hopping switches between frequencies to avoid interference and find the clearest channel for transmission. Dynamic frequency selection complements this technique by automatically selecting the least congested frequency for transmission, similar to how a GPS system will direct a driver to the quickest route based on current traffic conditions.

Channel bonding is a commonly used technique to mitigate wireless interference. It involves using multiple channels to transmit data simultaneously, which can increase the overall throughput of the network and reduce interference. The amount of gain from channel bonding can be quantified using the Shannon-Hartley theorem, which expresses the maximum theoretical channel capacity as

Mathematical graph
where C is the channel capacity, B is the channel bandwidth, and S/N is the signal-to-noise ratio.

The signal-to-noise ratio can be compared to trying to have a conversation in a loud and crowded room. The signal is the voice of the person you are trying to talk to, and the noise is all the other conversations and sounds in the room. If the signal is strong and the noise is low, you can easily hear and understand the other person. However, if the signal is weak and the noise is high, it can be difficult or impossible to hear what the other person is saying. Similarly, a high signal-to-noise ratio means that the signal is strong compared to the noise, while a low signal-to-noise ratio means that the signal is weak compared to the noise.

By increasing the number of channels used, the overall capacity of the network can be increased, leading to a reduction in interference and higher throughput. This is because the total bandwidth available to the network is proportional to the number of channels used and can be expressed as Btotal = Bper channel X ChN where Btotal is the total bandwidth, Bper channelp is the bandwidth of a single channel, and ChN is the number of channels used.

Another technique that can be used to mitigate interference is LBT (Listen Before Talk). LBT is a protocol that requires wireless devices to listen to other transmissions on a channel before transmitting. If a transmission is detected, the device will wait for a random amount of time before attempting to transmit again. This can reduce collisions between transmissions and improve overall network efficiency. LBT is particularly useful in scenarios where multiple devices are competing for the same channel, such as in a crowded public space. By implementing LBT, the chances of interference can be significantly reduced, leading to a more stable and efficient wireless network.

In addition, there are techniques that involve changing the way data is transmitted. One such technique is error correction coding, which involves adding redundant data to the transmission so that errors can be detected and corrected. The probability of successful decoding with error correction coding can be calculated using the formula where R is the code rate.

Mathematical graph

Error correction coding can be compared to proofreading a document before submitting it. By adding redundant data to the transmission, errors can be detected and corrected, similar to how a proofreader may catch and correct mistakes in a document using his knowledge (redundant information) before it is submitted. This ensures that the final product is error-free and of high quality.

Packet fragmentation is another useful technique for reducing interference and improving network efficiency, but it can also lead to issues with retransmissions. If one of the smaller fragments is lost or corrupted during transmission, the entire packet may need to be retransmitted, which can lead to delays, reduced throughput, and potentially increased information air-time, which can lead to a higher chance of colliding with another packet. To mitigate this issue, robust wireless communication protocols use a technique called selective retransmission, which allows only the lost or corrupted fragments to be retransmitted instead of the entire packet. This can significantly improve network efficiency and reduce delays caused by retransmissions.

All the techniques mentioned, such as beamforming, frequency hopping, dynamic frequency selection, channel bonding, Listen Before Talk, error correction coding, packet fragmentation, and selective retransmission, are part of Glass-Link's ECCM (Electronic Counter Counter Measures) tactics. What’s worth mentioning, Glass-Link uses a combination of these techniques, and as a result, creates a robust wireless network that can handle the demands of modern Industries. It is crucial to note that wireless interference mitigation is an ongoing process. As technology advances, new devices, and communication protocols will be introduced, leading to new forms of interference. Therefore, it is essential to stay vigilant and continue to adopt new techniques to mitigate wireless interference. The engineering team at Glass-Link is aware of these challenges and is constantly evolving the infrastructure to account for new potential interference sources in the future.


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