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Band-Preference Dynamic Spectrum Management



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Band Preference Dynamic Spectrum Management in a DSL Environment Wooyul Lee Youngjae Kim Mark H Brady and John M Cioffi Department of Electrical Engineering Stanford University Stanford CA 94305 Email wylee youngjae mhbrady cioffi stanford edu Abstract This paper introduces an algorithm for spectrum management for digital subscriber line DSL systems based on band preference The proposed method influences the usage of spectrum through band preference factors that subtly modify the loading algorithm of DSL modems Ad hoc algorithms for computing such band preference factors are discussed Simulation results in a practical ADSL environment show that the performance of the proposed method is better than that of Iterative Water filling IWF 1 and is close to that of Optimal Spectrum Balancing OSB 2 even with a small number of control parameters I I NTRODUCTION While DSL systems are widespread in today s data access networks there still exist several barriers to achieving higher data rates Chief among these barriers is Far End Crosstalk FEXT which is the electro magnetic interference from other same direction users in the binder In order to mitigate FEXT current ADSL systems rely on a Static Spectrum Management SSM scheme to set power spectral density masks PSDMASKs for all the modems 3 PSDMASKs limit each modem s transmitted power so that its FEXT into other users can be guaranteed to be lower than an acceptable level However this form of static spectrum management must be designed conservatively and thus its overall performance is much lower than what can be achieved by Dynamic Spectrum Management DSM Techniques for DSM may be stratified into levels of coordination 4 In Level 0 DSM such as Iterative Water filling IWF each user views other users signals as noise and seeks to maximize its data rate in a fully distributed manner In Level 1 DSM a Spectrum Management Center SMC is able to send limited control commands to each modem such as rate or power back off In Level 2 DSM



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