Content Scheduling in Multimedia Interactive Mobile Games

The paper by M. Mohsin Saleemi, Kristian Nybom, Jerker Björkqvist and Johan Lilius of Åbo Akademi University, Finland, studies how to schedule multimedia content sent over a DVB-H broadcast channel combined with a point-to-point 3G or GPRS channel in a location-based interactive mobile game called Åbot. The authors model the scheduling problem, present a use-case, propose a priority-based content scheduling algorithm, and evaluate it in a Ptolemy II discrete-event simulation. The simulated channel has a bandwidth of 384 Kbps and is assumed to be error free. The server predicts each player's movement toward quest locations and schedules data once the player reaches a threshold time, whose minimum value is calculated as the data size divided by the available bandwidth.

In the simulations, all deadlines were met with 10 players and 10 locations at 200 Kb per location, using 175 Kbps of bandwidth. Raising the player count to 15 kept deadlines met but increased bandwidth use to 300 Kbps, which the authors note is not linear with player growth. With 300 Kb data per location, deadlines began to slip at one point because position updates consumed remaining bandwidth; raising the threshold resolved this for 10 players.

With 20 players and 20 locations, deadlines were missed for 5 players once the 384 Kbps limit was reached. With 40 locations and 20 players, many deadlines were missed because some locations fell within the threshold range of a single player. The authors conclude that the scheduler works reasonably well for fewer than 20 players and data sizes below 300 KB in a small playing area.