Stable sleeping in DSL broadband access: Feasibility and tradeoffs

Energy efficient and stable operation of the DSL broadband access infrastructure has become an essential part of the emerging trend towards green communications. One promising means to obtain energy savings is the use of low power "sleep modes", putting DSL modems to sleep when they are not used. Executing the optimal sleeping policies is, however, not straightforward since turning the modem ON and OFF consumes both energy and time, and it also impacts the stability of the DSL network. We present an analytic framework providing optimal sleeping policies that achieve a Pareto-optimal tradeoff between energy consumption and delay performance. Furthermore, we present mechanisms achieving stable sleep mode operation that improve overall stability of DSL systems. Using a realistic DSL simulator, we demonstrate the three-way tradeoff between energy consumption, delay performance and stability.