Point-Casting Service in Wireless Networks

The broadcast nature of existing wireless LANs can produce excessive radio coverage which is often undesirable for applications like wireless IPTV or location-based service. To address this issue, we utilize the characteristics of signal attenuation common to all wireless communications and implement a point-casting service ¹ (PCast) over existing wireless networks that can significantly restrict the coverage for transmissions. The principle of PCast is to split and encode the downlink traffic and deliver it to the client via a few surrounding access points (APs). Hence, an unintended client cannot decode a packet without all its fragments. Equivalently, the service area is bounded within the intersection of communication coverage of all APs. The result coverage area can be further reduced via rate and power control at the APs. In this paper, we present our design and implementation of the PCast service on top of an 802.11a wireless LAN. Experiments conducted in a lab environment show that PCast can bound the service region to be within 2 meters around a client, while incurring jitter of less than 1ms, and bandwidth capacity loss of less than 10%.