  In today's growing data market, wireless service providers (WSPs) compete
severely to attract users by announcing innovative data plans. Two of the most
popular innovative data plans are rollover and shared data plans, where the
former plan allows a user to keep his unused data quota to next month and the
latter plan allows users in a family to share unused data. As a pioneer to
provide such data plans, a WSP faces immediate revenue loss from existing users
who pay less overage charges due to less data over-usage, but his market share
increases gradually by attracting new users and those under the other WSPs. In
some countries, WSPs have asymmetric timing for providing such innovative data
plans, while some other markets' WSPs have symmetric timing or no planning.
This raises the question of why and when the competitive WSPs should offer the
new data plans. This paper provides game theoretic modelling and analysis of
the WSPs' timing of offering innovative data plans, by considering new user
arrival and dynamic user churn between WSPs. Our equilibrium analysis shows
that the WSP with small market share prefers to announce the innovative data
plan first to attract more users, while the WSP with large market share prefers
to announce later to avoid the immediate revenue loss. In a market with many
new users, WSPs with similar market shares will offer the data plans
simultaneously, but these WSPs facing few new users may not offer any new plan.
Perhaps surprisingly, WSPs' profits can decrease with new user number and they
may not benefit from the option of innovative data plans. Finally, unlike
rollover data plan, we show that the timing of shared data plan further depends
on the composition of users.
