Crosstalk in Wideband Wireline Systems -- Curse and Blessing

Sammanfattning: The fourth generation broadband (4GBB) concept aims for ubiquitous and high-speed data communication over the existing twisted copper pairs between the last distribution point and the customer premise equipment. Although it saves deployment cost for the last-mile communication, using the existing copper infrastructure makes the system vulnerable to crosstalk due to electro-magnetic coupling from the neighboring pairs. Crosstalk is frequency-dependent and its interfering effects vary with implementation scenarios. When exploring higher frequencies and more functionality for the copper-based infrastructure, new practical problems emerge which opens up a space of unknowns to be investigated. This thesis deals with crosstalk, its effects, its mitigation, and approaches to exploit it in emerging systems and applications. Dividing the frequency range into three bands and taking into account the respective architecture’s characteristics, precoding schemes are proposed that properly process the crosstalk to improve end-users’ quality of experience. Chapters I–III of this thesis cope with sudden termination changes that significantly degrade the delivered throughput to active users when using a frequency range from 30 MHz to 180 MHz. A general model that interprets the changed coupling environment is presented and analyzed. Efficient precoder updating procedures are proposed for both linear and non-linear precoding systems which minimize the disturbed period to active end-users. Chapter IV designs modified linear precoders for rate-boosting by utilizing strong crosstalk between 150 MHz and 300 MHz. Taking advantage of a common network topology in a novel way, the proposed precoding schemes can add a decent amount of extra data-rate to target end-user(s) on top of the normal precoding schemes. Finally, Chapters V–VII revisit the frequencies below 30MHz and investigate the potential of using the existing copper-based infrastructure as the analog fronthaul for small-cell densification of the mobile networks. An LTE-over-copper system is sketched and analyzed invoking 3GPP requirements. A time-domain precoding scheme is proposed that performs channel estimation using carried LTE signals and yields an effective channel that is crosstalk-free and has identical direct paths.