Data communication Equipments | Data communication tests
This page covers data communication equipments used for data communication tests. The most common data communication equipments used are pattern generator, BER (Bit Error Rate) tester, TDR tester (LAN meter or cable analyzer), protocol analyzer etc. The data communication tests include eye diagrams,noise margin, Bit Error Rate (BER) or Packet Error Rate (PER) etc.
Introduction: As we know modern wireless communication technologies such as LTE, LTE-advanced, 5G are emerging due to complex data modulation techniques. For basic modulation (ASK, FSK, PSK) based communication technologies, standard RF and wireless equipments are enough for test and measurement. For advanced techniques, binary signals are required to be analyzed in more depth to understand their behaviour.
Data Communication Tests or testing
Following is the list of common data communication tests conducted in order to verify data communication devices.
Eye Diagrams:It is used as common method to analyze quality of the binary data. It is the display of individual bits overlapped with one another. The resulting signal will look similar to open eye. Shape of the pattern and degree by which eye is open can help us determine quality of the transmission. The figure-1 depicts baseband data signals as it travels through medium (i.e. coaxial or twisted pair cable). The figure-2 depicts eye diagrams of signal having good bandwidth (BW), limited bandwidth and severe bandwidth with noise. As shown amplitude of the signals are different due to different level of noise applied to the signal on the path.
Noise Margin: Noise margin is expressed as percent based on ratio of noise margin level 'a' to maximum peak to peak value of eye 'A'. Smaller the noise margin value, greater is the noise and greater is the BER.
Noise margin = (a/A) x 100
Bit Error Rate: This test helps in comparing transmitted bits with received bits. It keeps track of total number of bits transmitted and number of bits received in error. It can be expressed as follows.
BER (%) = (Number of bits received in error / total number of bits transmitted) x 100
Data Communication Equipments
Following is the list of common data communication equipments used for data communication testing.
Pattern Generator: A pattern generator is a device which produces fixed binary bit patterns in serial form. It is used as test signal generator in data communication tests. It can generate repeating ASCII code or any desired binary stream of 1s and 0s. It is available in equipment form or can be simulated in software for testing.
Oscilloscope: It is time domain data communication equipment used to analyze time domain behaviour of the binary signal including eye diagrams.
BER Tester: It is used to measure BER (Bit Error Rate) of a communication chain both standalone and end to end.
TDR Tester: It is known as cable analyzer or LAN analyzer. This equipment is connected to coaxial cable or twisted pair cable for test and measurement purpose. TDR stands for Time Domain Reflectometry. Some of the tests performed by TDR analyzer include open circuit test, short circuit test, impedance anomalies on cables (coaxial, twisted pair), cable length measurement, capacitance measurement, loop resistance measurement, cable attenuation measurement, cable miswiring etc.
Protocol Analyzer: It is used to capture and analyze data transmitted in real time without affecting normal functioning of the communication chain or system. As we know data communication system transmits data in specific packet and/or frame format. This includes sync bits, source/destination addresses, header, error correction bytes, payload etc. All these frame/packet information fields are segregated by protocol analyzer and displayed. Data communication protocols such as HDLC, SDLC, BISYNC, Ethernet, SONET etc. are being analyzed by protocol analyzer.