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Reducing Crosstalk in Data Communication

Published Date
Author Cadence System Analysis

Key Takeaways

  • Twisted-pair cables interlaced inside a cable are used for wired data transmission.

  • There are two main types of crosstalk: near-end crosstalk (NEXT) and far-end crosstalk (FEXT).

  • The most common way of mitigating crosstalk in cable data transmission is to increase the physical distance between cable pairs.

 Data Communicaiton

Crosstalk in data communications has a serious impact on reliability

The exchange of digital data between computers is one kind of data communication. Data communication in computer networks can be established using cables or wireless media. Irrespective of the mode of transmission, crosstalk in data communication has a serious impact on the reliability and service hours of the data exchange between computers. The sensitivity of data communication to crosstalk can inject noises in data transmission and thus degrade the signal-to-noise ratio (SNR) of the desired data signal. We will discuss crosstalk in data communication over cables in this article. 

Data Communication

The process of exchanging data or information is generally called data communication. The exchange of digital data is done between two devices over a transmission medium. Any data communication system consists of a sender, receiver, and transmission medium over which the data is sent. The path taken by the digital data to reach the receiver from the sender is called the transmission medium. The transmission medium can be cables or a wireless medium.

The critical data exchanged over the transmission medium can be affected by noise, interference, bridge taps, attenuation, and crosstalk. The interference caused by crosstalk can influence the performance of data communication by reducing the throughput and increasing the delay time. Crosstalk significantly impacts wired as well as wireless data communication. Therefore, any data communication system design must have steps in place to ensure reliability and security during transmission.

Crosstalk in Data Communication 

Let’s explore crosstalk further. We will discuss how it is generated, the types of crosstalk, and, finally, some mitigation strategies to reduce the effects of crosstalk.

How Is Crosstalk Generated?

Twisted-pair cables interlaced inside a cable are used for wired data transmission and are generally called cable bundles. When digital data is sent over a cable bundle, the electrical data signals radiate electromagnetic energy. The energy interferes with the signals in the neighboring pairs in the same cable bundle. If signal transmission or reception over a cable bundle is in the same frequency, the original signal gets mixed up with crosstalk-induced signals. As the distance between the cable pairs decreases, it increases the crosstalk value on the original data signal. For the smallest distance between the cables, crosstalk reaches the maximum value.

The probability of crosstalk signal distortion and interference increases as the data traffic increases. An increase in the frequency of the signals significantly makes data transmission vulnerable to a higher amount of self radiation, and thereby more crosstalk. Crosstalk changes the shape of data signals and decreases the SNR of the original signal. Crosstalk reduces the data transmission rate and thus slows down the network. It can lead to sudden shutdowns of the network in an instant, which may require a restart. 

Crosstalk Types 

There are two main types of crosstalk: near-end crosstalk (NEXT) and far-end crosstalk (FEXT). The influence of NEXT is very crucial, as the neighboring pair disturbances induce heavy distortions in the original data signal. The use of different frequency ranges for transmission and reception can cause a loss of the NEXT crosstalk effect on data communication.

In the context of signal distortions in the cable, FEXT is less significant, as it attenuates the interfered signal at the far end of the cable loop while traveling. Increasing the frequency increases the attenuation inside the cable pairs and reduces the influence of FEXT crosstalk on data signals.

Crosstalk Mitigation 

The most common way of mitigating crosstalk in cable data transmission is to increase the physical distance between cable pairs. One way of increasing the physical distance between cable pairs is to increase the sheath thickness by using specific shapes. However, this crosstalk mitigation method is less efficient, as it reduces cable flexibility and cable duct utilization.

Conventionally, unshielded twisted pair cables are employed for wired connections of data transmission. Increasing the twisting frequency of the wires can reduce the crosstalk influence in unshielded cable pairs. It prevents interference crossover between twisted cable pairs. 

To reduce crosstalk in data communications, shielded pairs of twisted cables are more effective than unshielded twisted pairs. Cadence software can help you in data communication system design using both shielded and unshielded cables.

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