BER error rate affects the bit error rate

Bit error rate (BER) is a key parameter used to evaluate systems that transmit digital data.

Systems suitable for bit error rate include wireless data links, as well as fiber data systems, Ethernet, or any system that transmits data through networks where noise, interference, and phase jitter can cause digital signal degradation. Although the working methods of these systems and the way of bit error rate are different, the basic principle of the bit error rate itself is still the same.

When data is transmitted over the data link, there is a possibility that errors are introduced into the system. If errors are introduced into the data, the integrity of the system may be compromised. Therefore, it is necessary to evaluate the performance of the system, and the bit error rate is an ideal way to achieve this goal.

Unlike many other evaluation methods, the bit error rate evaluation system's end-to-end performance includes the transmitter, receiver, and transmission medium between the two. In this way, the bit error rate allows the actual performance of the running system to be tested, rather than just testing the system components and expecting them to function properly in the system.

As the name suggests, the bit error rate is defined as the ratio of errors in the transmission system. This can be directly converted into the number of errors that occur in a fixed-digit string. The definition of the bit error rate can be converted into a simple formula:

If the transmission medium between the transmitter and the receiver is good and the signal-to-noise ratio is high, the bit error rate will be very small, may be negligible, and have no significant effect on the entire system, but if noise can be detected, then it is possible The bit error rate needs to be taken into account.

The main cause of degradation of the data channel and the corresponding bit error rate is the change in noise and propagation path (when a wireless propagation path is used). Both of these effects have a random component for them: the noise that follows the Gaussian probability function when the propagation model follows the Rayleigh model. This means that analysis of channel characteristics is usually performed using statistical analysis techniques.

For fiber optic systems, bit errors (errors) are primarily due to defects in the components that make up the link. These include optical drivers, receivers, connectors, and the fiber itself. Bit errors can also be introduced as a result of possible optical dispersion and attenuation. In addition, the optical receiver itself may introduce noise. Typical possibilities are photodiodes (photodetectors) and amplifiers that need to respond to very small changes, so there may be high noise levels.

Another factor influencing bit error is any phase jitter that may exist in the system, as this may change the sampling of the data.

Signal to noise ratio SNR and Eb/No values ​​are parameters that are more relevant to wireless links and wireless communication systems. In this regard, the bit error rate BER can also be defined as a probability of error or a POE. To determine this, use the other three variables. They are the error function - ERF, the energy of a single bit - Eb, the noise power spectral density (noise power at 1 Hz bandwidth) -- No.

It should be noted that each different type of modulation has its own error function value. This is because each modulation method has different performance in the presence of noise. In particular, higher-order modulation methods (such as 64QAM, etc.) that can achieve higher data rates are less robust in the presence of noise. Low-order modulation methods (such as BPSK, QPSK, etc.) provide lower data rates but are more robust.

The energy per bit Eb can be determined by dividing the carrier power by the bit rate, which is a measure of the energy of the size in Joules. No is the power per Hz, so the power (joules per second) is the size divided by the second. From the perspective of the size ratio, Eb/No, all dimensions are offset to become a dimensionless ratio. It should be noted that POE is proportional to Eb/No and is a form of signal-to-noise ratio.

As can be seen from the use of Eb/No, the bit error rate is affected by many factors. By manipulating variables that can be controlled, the system can be optimized to provide the desired level of performance. This is usually done during the design phase of the data transmission system to adjust the performance parameters during the initial design concept phase.

Interference: The level of interference present in the system is generally determined by external factors and cannot be changed by system design. However, setting the bandwidth of the system is possible. The level of interference can be reduced by reducing bandwidth. However, reducing bandwidth limits the achievable data throughput.

Increase transmitter power: You can also increase the power level of the system to increase the power per bit. This must be balanced with factors including interference levels for other users, as well as increasing the impact of power output on the size and overall power consumption of the power amplifier and battery life.

Low-order modulation: Low-order modulation schemes can be used, but at the expense of data throughput.

Reduce bandwidth: Another way you can reduce the bit error rate is to reduce bandwidth. A lower noise level will be received, so the signal to noise ratio will be improved. This again reduces the achievable data throughput.

In order to achieve a satisfactory bit error rate, all effective factors must be balanced. It is often impossible to meet all the requirements and some trade-offs need to be made. However, even if the bit error rate is lower than the ideal requirement, an error correction level can be introduced in the transmitted data. Although more redundant data needs to be sent and a higher level of error correction is required, this helps to mask the effects of any bit errors that occur, thereby increasing the overall bit error rate.

The bit error rate BER is a parameter that well indicates the performance of a data link such as a wireless or fiber optic system. One of the main parameters of interest in any data link is the number of errors that occur, and the bit error rate is a key parameter. Knowledge of the BER also allows other features of the link, such as power and bandwidth, to be customized to achieve the desired performance.