ROMSO Cyprus Knowledge Base

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In radio technology, the range in a radio connection is that distance which may exist at most between the transmitter and the receiver, so that communication is still possible.

Basics of digital radio
The reliability of a modern radio system operating with digital transmission methods depends on the bit error rate (BER) of the received bit stream. In order for the error correction methods used by the radio system, such as the forward error correction, to be able to supply a bit stream which is sufficiently error-free for the radio application, the bit error rate of the received, uncorrected bit stream must not be too high. A maximum permissible bit error rate of 0.1% (BER = 1E-3) applies as a rule of thumb for easily understandable voice communication. Thus, at most every 1000 bit may be received incorrectly, so that the error correction methods in the receiving device can correct the bit error and an acceptable speech quality results.

For fast data transmissions, the requirements for the maximum permissible bit error rate are significantly higher. As a rule of thumb for fast data transmissions, a maximum permissible bit error rate of 0.00001 ‰ (BER = 1E-8) applies. The bit error rate measured in the receiving device after passing through all error correction methods must meet this limit value so that fast data transmissions with the network protocol TCP are possible. For more accurate calculations of the maximum allowable bit error rate, the Mathis equation should be used.

The bit error rate (BER) depends on Eb/N0 and the digital modulation method used. Eb/N0 is understood as the normalized signal-to-noise ratio (SNR) and is also referred to as “SNR per bit”. Or to put it more simply: the more symbols a symbol alphabet comprises, the more difficult it is in real transmission systems to be able to reliably distinguish adjacent symbols, imaged in different amplitude values and phase positions of a carrier signal, in the receiver, since physically induced interference such as noise is also added. Very simple digital modulation methods with a very small symbol alphabet and thus with a very low spectral efficiency of 1 bit/s/Hz are very robust against physically induced interference. One such simple digital modulation method is BPSK. BPSK requires a minimum Eb/N0 and a minimum Es/N0 of only:

7 dB for a bit error rate of 0.1% (BER = 1E-3)
12 dB for a bit error rate of 0.00001 ‰ (BER = 1E-8)

In the Gaussian transmission channel, the transmission is only disturbed by the additive white Gaussian noise (AWGR/AWGN). The greater the symbol alphabet, the higher the spectral efficiency of the digital modulation method used, but the greater the demands on the minimum Eb/N0 with the same bit error rate. The same applies to Es/N0. For example:

With the Eb/N0 forms