Iterative Bandwidth Allocations for ADSL Modems with Crosstalks

• Main Authors: Shui-Tien Mai, 麥水田
• Other Authors: Miin-Jong Hao
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/69538184066309327415

碩士 === 國立高雄第一科技大學 === 電腦與通訊工程所 === 95 === The performance of DSL systems is severely constrained by crosstalk due to the electromagnetic coupling among the multiple twisted pairs making up a phone cable. In order to reduce the impacts from crosstalk, DSL systems are currently designed under the assumption of worst-case crosstalk scenarios which thus leads to overly conservative DSL deployments. Dynamic spectrum management (DSM) is a new technique for multi-user power allocation and/or detection in digital subscriber line (DSL) networks. In DSM transmit spectra are adapted based on the direct and crosstalk channels seen by the modems within a network. This allows the binder bit rate performance being maximized. Multi-user power control algorithms can be used to combat the degrading effects due to crosstalk. The best ever known distributed power control solution is the Iterative Water-filling (IWF). In this thesis we focus on DSM at level 1 and the power allocation based on the Iterative water-filling algorithm. The values of each subchannel are calculated from the Dual End Loop Test (DECT). Then the values are used in the water-filling algorithm for performing the power allocation for each subchannel. Our simulation results showed that the maximum data rate can be obtained by the rule that allocating more power to the bands with higher channel values. Iterative bandwidth allocation method is very practice and applicable to ADSL modems with water-filling algorithm.