  With the popularity of mobile devices, using the traditional client-server
model to handle a large number of requests is very challenging. Wireless data
broadcasting can be used to provide services to many users at the same time, so
reducing the average access time has become a popular research topic. For
example, some location-based services (LBS) consider using multiple channels to
disseminate information to reduce access time. However, data conflicts may
occur when multiple channels are used, where multiple data items associated
with the request are broadcast at about the same time. In this article, we
consider the channel switching time and identify the data conflict issue in an
on-demand multi-channel dissemination system. We model the considered problem
as a Data Broadcast with Conflict Avoidance (DBCA) problem and prove it is
NP-complete. We hence propose the frequent-pattern based broadcast scheduling
(FPBS), which provides a new variant of the frequent pattern tree, FP*-tree, to
schedule the requested data. Using FPBS, the system can avoid data conflicts
when assigning data items to time slots in the channels. In the simulation, we
discussed two modes of FPBS: online and offline. The results show that,
compared with the existing heuristic methods, FPBS can shorten the average
access time by 30%.
