Supporting continuous mobility through multi-rate wireless packetization

Continuous mobility scenarios are those in which applications continue to use the radio interface while on the move. With the emergence of Voice-over-WiFi phones, WiFi-enabled music players, and many other such gadgets, continuous mobility is becoming a prevalent mode of operation for WiFi standards. We contend that the existing packetization structures employed in WiFi devices, is not the most suitable for these emerging class of continuous mobility applications. Therefore, in this paper, we suggest a new software-level, standards-compliant extension to the WiFi packetization techniques that provides greater agility and improved performance. In particular, we propose the notion of a multi-rate wireless packet, in which different segments of the same Protocol Data Unit (PDU) are modulated at different physical transmission rates. This is a departure from conventional modulation mechanisms in which the entire PDU is modulated using a single rate. In this paper, we (i) discuss some uses of such a packetization structure for continuous mobility applications, (ii) describe a practical approach to implementing multi-rate wireless packetization in the 802.11 context as a software-only modification that directly leverages current PHY and MAC layer implementations, and (iii) demonstrate the benefits of such an approach with some simple evaluation. We conclude by discussing some of the next steps needed to realize the full potential of this notion.