Algorithms for Communications Systems and their Applications, 2nd Edition

Chapter 17Applications of interference cancellation

The algorithms and structures discussed in this chapter can be applied to both wired and wireless systems, even though transmission systems over twisted‐pair cables will be considered to describe examples of applications. Full‐duplex data transmission over a single twisted‐pair cable permits the simultaneous flow of information in two directions using the same frequency band. Examples of applications of this technique are found in digital communications systems that operate over the telephone network. In a digital subscriber loop, at each end of the full‐duplex link, a circuit called hybrid separates the two directions of transmission. To avoid signal reflections at the near and far‐end hybrid, a precise knowledge of the line impedance would be required. As the line impedance depends on line parameters that, in general, are not exactly known, an attenuated and distorted replica of the transmit signal leaks to the receiver input as an echo signal. Data‐driven adaptive echo cancellation mitigates the effects of impedance mismatch.

A similar problem is caused by crosstalk in transmission systems over voice‐grade unshielded twisted‐pair (UTP) cables for local‐area network applications, where multipair cables are used to physically separate the two directions of transmission. Crosstalk is a statistical phenomenon due to randomly varying differential capacitive and inductive coupling between adjacent two‐wire transmission lines ...