Speed Improves Delay-Capacity Trade-Off in MotionCast

In this paper, we study a unified mobility model for mobile multicast (MotionCast) with n nodes, and k destinations for each multicast session. This model considers nodes which can either serve in a local region or move around globally, with a restricted speed R. In other words, there are two particular forms: Local-based Speed-Restricted Model (LSRM) and Global-based Speed-Restricted Model (GSRM). We find that there is a special turning point when mobility speed varies from zero to the scale of network. For LSRM, as R increases, the delay-capacity trade-off ratio decreases iff R is greater than the turning point Theta(root 1/k) ; For GSRM, as R increases, the trade-off ratio decreases iff R is smaller than the turning point, where the turning point is located at Theta(root 1/k) when k = o(n(2/3)), and at Theta(k/n) when k = omega(n(2/3)) As k increases from 1 to n - 1, the region that mobility can improve delay-capacity trade-off is enlarged. When R = Theta(1), the optimal delay-capacity trade-off ratio is achieved. This paper presents a general approach to study the performance of wireless networks under more flexible mobility models.