DeltaCast: Efficient File Reconciliation in Wireless Broadcast Systems

Recently, there has been an increasing interest in wireless broadcast systems as a means to enable scalable content delivery to large numbers of mobile users. However, gracefully providing efficient reconciliation of different versions of a file over such broadcast channels still remains a challenge. Such systems often lack a feedback channel and consequently updates cannot be easily tailored to a specific user. Moreover, given the potentially large number of possible versions of a file, it is impractical to send a tailored update for each particular user. In this paper we consider the problem of efficiently updating files in such wireless broadcast channels. To this extent, we present DeltaCast, a system that combines hierarchical hashes and erasure codes to minimise the amount of battery power and the amount of time needed to synchronise each mobile device. Based on our experimental results, we show that DeltaCast is able to efficiently identify the missing portions of a file and quickly updated each client.