Modified SNR gap approximation for resource allocation in LDPC-coded multicarrier systems

The signal-to-noise ratio (SNR) gap approximation provides a closed-form expression for the SNR required for a coded modulation system to achieve a given target error performance for a given constellation size. This approximation has been widely used for resource allocation in the context of trellis-coded multicarrier systems (e.g., for digital subscriber line communication). In this contribution, we show that the SNR gap approximation does not accurately model the relation between constellation size and required SNR in low-density parity-check (LDPC) coded multicarrier systems. We solve this problem by using a simple modification of the SNR gap approximation instead, which fully retains the analytical convenience of the former approximation. The performance advantage resulting from the proposed modification is illustrated for single-user digital subscriber line transmission

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

© 2017 IEEE. 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.status: publishe

Unequal error protection in rate adaptive spectrum management for digital subscriber line systems

© 2015 EURASIP. Crosstalk between different lines in a cable bundle is the major source of performance degradation in DSL systems. Spectrum coordination techniques have been shown to substantially alleviate the crosstalk problem. The equal level of error protection that these techniques provide can however be excessive for some applications. Many applications with diverse error protection requirements can be sharing the same connection. In this paper, two novel rate adaptive spectrum management algorithms are presented that enable a different level of error protection for different applications. The algorithms are generalizations of the globally optimal OSB and the locally optimal DSB algorithms for systems that incorporate unequal error protection. Through simulation, it is shown that unequal error protection can lead to significant performance gains.status: publishe

A modified SNR Gap Approximation for resource allocation in LDPC-coded multicarrier systems

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Delay Performance Enhancement for 4th Generation DSL Networks through Cross-Layer Optimization

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