Statistical estimation of access frequencies in data broadcasting environments

Abstract

In a data publishing environment, the server periodically broadcasts data to users based on a broadcast program. The program is constructed using knowledge of access frequencies, which is assumed to be available and accurate, on the broadcast data. For example, the program may broadcast frequently accessed data more often in a broadcast cycle. However, it remains an open question as to how to obtain such access frequencies. The difficulty of obtaining such access frequencies is that in such an environment, mobile users are only listening to the channel they are interested in and do not request for the data items from the server. A promising approach in the literature is to make use of broadcast misses to understand the access patterns in a data publishing environment. In this case, mobile users may decide whether to wait for the required item to arrive or to make an explicit request for it even though it will be published. However, estimation of access frequencies based on broadcast misses may not be accurate because the number of broadcast misses to the data depends on how frequently the data is broadcast: if a piece of data is more frequently broadcast than the others, then the broadcast misses to that piece of data will be low because the average waiting time is low. In this paper, we propose a statistical estimation model that is based on maximum likelihood estimation to estimate the access frequencies. Our approach is novel in that it exploits knowledge that is available - broadcast misses and broadcast frequencies - to refine the program to better meet the needs of the user population. We report our simulation study that demonstrates the effectiveness of our approach.