Challenges in wireless networks - WaveNet
Radio waves propagate in all directions. Unlike cables, they are not bound to a transmission medium (cable). This results in some radio-specific characteristics.
Three decisive influences determine whether a radio signal is transmitted successfully:
- Signal strength
- Signal-to-noise ratio
- Frequency utilisation
Explanation of the influences
Signal strength | Signal-to-noise ratio | Frequency utilisation |
|---|---|---|
The signal strength is the amplitude of the radio wave. The stronger the signal, the more clearly the receiver can receive the transmitted data. The signal strength decreases with increasing distance or due to unfavourable transmission media. The more sensitive a receiver is (the better the antennas are), the less signal strength it needs. | The signal-to-noise ratio (SNR) indicates how strong the noise is compared to the wanted signal. Radio waves do not "end". Theoretically the range is unlimited, practically only the signal strength decreases. This means that radio waves penetrate other radio networks and no longer produce a useful signal, but (disturbing) static noise. If the noise is too strong (i.e. the signal-to-noise ratio is very poor), the receiver can no longer distinguish the wanted signal from the noise. | The utilization of the frequency is the ratio of free transmission time to occupied transmission time. A receiver can only receive one radio signal at a time. WaveNet devices operate according to the "listen-before-talk" principle. No WaveNet device transmits if it detects that a radio signal is already being transmitted on the frequency band in use. This results in waiting times until the frequency band is free again. The longer these waiting times are, the longer it takes for a device to transmit → The transmission speed decreases. |
Examples from daily life
Signal strength | Signal-to-noise ratio | Frequency utilisation |
|---|---|---|
Two people speak to each other (language as a signal). One person speaks louder (signal strength increases). If there is a wall between the people (unfavourable transmission medium), the speech becomes quieter (signal decreases). If a person does not turn towards the speaker (unfavourable alignment of antennas), speech is perceived as quieter (signal decreases). People with good hearing (sensitive receivers) can also understand soft speech (low signal strength). | Two people speak to each other (language as a signal). The people are standing at a busy road next to each other, which causes noise (static). The closer people get to the road, the louder the noise becomes in relation to the speech (signal-to-noise ratio decreases). If people stand too close to the road, they no longer understand each other. People can either move away from the street (noise decreases) or speak louder (signal increases) to improve the signal-to-noise ratio. It makes no difference whether a person can hear better (sensitivity is higher), because with speech (signal) the street (noise) is also heard louder. | Many people want to speak simultaneously (speech as signal). If one person is speaking (frequency band is busy), then no other person can speak (waiting time), otherwise no one will understand. People have to wait until there is a break in the conversation ("listen-before-talk") and then they can speak (start radio signal transmission). The more people are in a room, the longer they have to wait for a break in the conversation (frequency utilisation increases). People can either spread out spatially (to avoid hearing when other people are talking at the same time) or be short (to shorten the waiting time), so that more people can talk in the same period of time (reduce the load on the frequency). |
Possible causes for deteriorating environmental conditions in WaveNet
(List without claim to completeness)
Signal strength | Signal-to-noise ratio | Frequency utilisation |
|---|---|---|
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