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Chip Deals Bringing DSM Closer Conexant, Ikanos, Upzide sign on Dave Burnstein, DSL Prime Dynamic Spectrum Management is the most promising technology for improved DSL performance, several key telco engineers have told me. The first stage is now close to market, with John Cioffi's Assia announcing Rapide, an interface to a DSM management system that optimizes DSL performance. DSM is a family of techniques that optimize customer circuits for the actual conditions. The first step is to get information on the noise in the actual circuit and binder, and adjust profiles of each DSL modem. The more difficult task is to adjust multiple modems in the group in a way that improves performance for all. That's challenging, especially in real time. Today's DSL chips have highly sophisticated test capability. There's been an intense struggle over the standard of how to provide that data to a management system, a story I should be reporting. First payoff of DSM is improved performance on marginal ADSL loops which are the most prone to expensive service problems. The future goal is doubling VDSL rate/reach for many customers. ADSL in particular is close to the Shannon Law limits on performance. VDSL chips can still be improved without hitting the Shannon Limit. No one has directly shared with me test data, but both AT&T and Swisscom have been publicly disappointed by the current generation of chips. The next generation should be better. Beyond that, progress will require an end run around the Shannon Limit, which is defined in relation to a given noise level. DSL standards before DSM assumed a standard noise level and chips are optimized to perform in a standard noise test environment. DSM effectively reduces noise and allows the entire system to be optimized for even better performance. |
