Bit Error Rate BER Definition and Basics
In telecommunication transmission, the bit error rate (BER) is the percentage of bits that have errors relative to the total number of bits received in a transmission, usually expressed as ten to a negative power. This can be directly translated into the number of errors that occur in a string of a stated number of bits. The definition of bit error rate can be translated into a simple formula:
For example, a transmission might have a BER of 10 to the minus 6, meaning that, out of 1,000,000 bits transmitted, one bit was in error. The BER is an indication of how often a packet or other data unit has to be retransmitted because of an error. Too high a BER may indicate that a slower data rate would actually improve overall transmission time for a given amount of transmitted data since the BER might be reduced, lowering the number of packets that had to be resent.
Bit error rate, BER may traditionally be associated with radio communications links, however bit error rate tester is also applicable to other systems such as fibre optic links, Ethernet, or any link over which a digital signal is transmitted.
Factors Affecting Bit Error Rate
It can be seen from using Eb/No, that the bit error rate, BER can be affected by a number of factors. By manipulating the variables that can be controlled it is possible to optimise a system to provide the performance levels that are required. This is normally undertaken in the design stages of a data transmission system so that the performance parameters can be adjusted at the initial design concept stages.
- Interference: The interference levels present in a system are generally set by external factors and cannot be changed by the system design. However it is possible to set the bandwidth of the system. By reducing the bandwidth the level of interference can be reduced. However reducing the bandwidth limits the data throughput that can be achieved.
- Increase transmitter power: It is also possible to increase the power level of the system so that the power per bit is increased. This has to be balanced against factors including the interference levels to other users and the impact of increasing the power output on the size of the power amplifier and overall power consumption and battery life, etc.
- Lower order modulation: Lower order modulation schemes can be used, but this is at the expense of data throughput.
- Reduce bandwidth: Another approach that can be adopted to reduce the bit error rate is to reduce the bandwidth. Lower levels of noise will be received and therefore the signal to noise ratio will improve. Again this results in a reduction of the data throughput attainable.
What is BERT?
A BERT (bit error rate tester) is a procedure or device that measures the BER for a given transmission. Bit error rate testers are used for testing systems that transmit digital data from one location to another. When data is transmitted there is a possibility of errors being introduced into the system, especially if the medium over which the data is transmitted is noisy. If errors are introduced into the data, then the integrity of the system may be compromised. As a result a bit error rate test can indicate much about the link quality and the ability of the system to accommodate the link characteristics.
In order that bit error rate can be measured easily and quickly, a variety of bit error rate testers are available from a variety of manufacturers. Each tester has its own advantages and disadvantages. Take YGBERT 2M PCM bit error rate tester for example, YGBERT 2M PCM bit error rate tester is a pocket-sized and hand-held instrument. It’slight-weighted, fully function and among the best ones in the world. It can be used in inspection systems and supervision of digital micro-wave systems. It’sespecially useful in the installation, field operation and maintenance of digital transmission systems. With its functions of Testing and taking performance analysis on the Bit error rate and on-line code error of Single Group Digital communication system and Digital communication and the development, manufacture, construction and maintenance of the equipment, it can test bit error rate quickly and accurately.