Dynamic Spectrum Management in Digital Subscriber Line Networks With Unequal Error Protection Requirements

Digital subscriber line (DSL) technology remains the most popular broadband access technology. A variety of algorithms has been developed to improve performance in DSL networks, which are commonly referred to as dynamic spectrum management (DSM) algorithms. The main goal of these algorithms is to fight crosstalk between different lines in a cable bundle. Current DSM algorithms provide an equal level of error protection for each serviced application and each user. However, different applications may have unequal error protection (UEP) requirements. The equal level of error protection usually provided by DSM algorithms may then be excessive for some applications, which leads to a waste of valuable resources. This paper, therefore, considers DSM for DSL networks providing UEP. Four joint signal and spectrum coordination algorithms are presented, enabling a different level of error protection for different applications. These algorithms are modified versions of existing optimal spectrum balancing and distributed spectrum balancing algorithms for joint signal and spectrum coordination in upstream as well as downstream DSL. In addition, an algorithm is presented which, for each application, selects a suitable modulation and coding (MC) scheme from a set of admissible MC schemes. Through simulations, it is shown that DSM with UEP can indeed lead to moderate performance gains.