Gleichzeitige Reduktion von Übersprechen und Behandlung von QoS zur Unterstützung von Multimedia-Diensten in VDSL Kabelnetzen
Zusammenfassung der Projektergebnisse
The resulting performance of Digital Subscriber Line (DSL) systems is strongly limited by interferences, which are called Far-End Crosstalk (FEXT). They are produced by each user, disturbing all other users on adjacent lines within the cable binder. Simultaneously there is an always growing demand for really high but also stable data rates, to allow DSL users to run high-rate applications in parallel and stably on their individual DSL line. In the DFG-funded project three crosstalk mitigation solutions using spectrum management and/or partial crosstalk cancellation have been analyzed for upstream transmission. Crosstalk interference can be either mitigated by an appropriate and subcarrier specific choice of the transmit power on each line or by partial crosstalk cancellation techniques in the receiver. In this research project a QoS-based partial cancellation algorithm has been developed. In this case the occurring interferences within the cable binder are successively canceled to finally meet the users’ data rate requirements. The choice of canceled interferences is based on the selection of crosstalker-tone pairs. Savings of computational complexity were obtained compared to classical selection algorithms. With QoS-based partial cancellation techniques, a crosstalk selection method was found, which first focuses on the fulfillment of data rate targets, instead of initially employing the available computational complexity for sum data rate maximization. It is well-known that crosstalk cancellation procedures outperform pure spectral management techniques. In this research project the IterativeWater Filling (IWF) technique in poweradaptive mode has been analyzed with respect to the required QoS targets. In the last step, an algorithm was developed, which combines IWF in rate-adaptive mode and QoS-based partial cancellation jointly. Simulation results showed that additional computational complexity savings are feasible. The needed computational resources for target fulfillment could be reduced by 5%. Applying this algorithm a strong performance increase has been observed especially for long copper lines. All three developed and analyzed methods can be practically used, when an application related high but also stable data rate needs to be guaranteed to all users in a cable binder. In case of collocation of the modems in the Central Office (CO) and access to all line cards in the modems, QoS-based partial cancellation or joint QoS-based partial cancellation and rateadaptive IWF can be applied. Power-adaptive IWF is completely autonomous and does not require any centralized processing.
Projektbezogene Publikationen (Auswahl)
- ’QoS-Based Partial Crosstalk Cancellation in Upstream VDSL Systems’, Proc. 14th International OFDM Workshop, Hamburg, Deutschland, September 2009
Hermann Rohling
- ’Successive Crosstalk Cancellation Facing the Dynamic Situation in VDSL2 Systems’, IET Communications, vol. 5, issue 11, p. 1491-1496, July 2011
Hermann Rohling
