Wideband communication and Narrowband communication

Wideband communication

Wideband communication uses – as the name states – a wider portion of the spectrum. This has some advantages and disadvantages:

  • Wideband communication allows for a higher bandwidth and therefore for a faster communication
  • Wideband communication allows for spreading the signal to encrypt it (See: Direct Sequence Spread Spectrum and its derivates)
  • wideband communication allows for notching out narrow noise sources in the spectrum (See OFDM)
  • Wideband communication puts high demands on the linearity of filters (also the respective filter bandwidths are higher)
  • It’s harder to send and detect wideband signals (You need a high Signal to Noise ratio) as the energy of the signal is distributed across the width of the spectrum which makes the signal weaker the wider it gets (transmitting on a given power level)
  • Wideband communication is almost exclusively done in higher frequencies (I’d say 433MHz+) as it’s easier to design integrated circuits which have wider filters
  • Common modulation techniques are OFDM, GMSK, N-PSK and QAM-N in combination with frequency hopping
  • Examples of wideband communication are wireless networks: Wifi, LTE, HSPA

Narrowband communication

Narrowband communication uses a narrow bandwidth.

  • Narrowband signals are used in a slower form of communication where mainly voice or slow datastreams have to be transmitted
  • Narrowband signals usually have a far greater range of reception as narrower filters can be used and therefore cancel out unwanted wideband noise. The transmitted energy also concentrates on a smaller portion of the spectrum.
  • Common uses are FM radio, AM radio, satellite downlinks, morse code (CW), GPS signals and NOAA weather transmissions.
  • Common modulation techniques are AM, FM, SSB, BPSK and CW

Often IC manufacturers do focus on narrowband communication because often you need to flip a switch and propagate the change in signal through the air which does not need a high bandwidth. If you however try to send a x264 packed HD picture with 24MBit over the air you most certainly need a high bandwidth to transmit it in realtime. But according to the frequency usage plans you need to use a higher frequency band to be allowed to use a certain bandwidth (or power level). This is why wideband communication is almost exclusive to hardware used for 1 GHz+ operation.

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