On the Effects of Loose Causal Consistency in Mobile Multiplayer Games Angie Chandler, Joe Finney Computing Department Infolab 21, South Drive Lancaster University, UK SoonKyu Jin NetGames 2005

MMLAB 2 Contents Introduction Evaluation Rendezvous Implementation : Knockabout Conclusion 5

MMLAB 3 Introduction (1/3)  Emerging distributed real-time multiplayer mobile games Operated by Sony PSP, Nintendo DS, Nokia N- Gage and Smart phone platform etc. Bounded by network latency  Existing consistency mechanisms inapplicable to the mobile gaming domain  So, this paper proposes Rendezvous

MMLAB 4 Introduction (2/3)  Necessary to maintain a consistent shared view of the game state  Existing consistency mechanism : Rollback Rely on local lag between action and displaying Bounded by the human tolerance for delay Rollback can no longer be applied  Maximum tolerable latency : 120ms~250ms  Latency of today’s wide area wireless network GPRS : 1000~2700ms 3G : 400~500ms

MMLAB 5 Introduction (3/3)  In high latency network, existing techniques (rollback etc.) for consistency management of multiplayer games cannot be applied to the real- time mobile gaming domain

MMLAB 6 Rendezvous (1/2)  Rendezvous mechanism : each player will see different view of the game action Reflected by received certain state information  The Rendezvous mechanism

MMLAB 7 Rendezvous (2/2)  Generating the target state  Adaptation rule

MMLAB 8 Implementation : Knockabout (1/3)  Mobile multiplayer soccer game  Operate with up to 20 players split into two team  Each interacting with the game via their own gaming handset  Provides simple top down view  Screen size 176*220 pixels Scrolling the overall size is 616*1000 pixels

MMLAB 9 Implementation : Knockabout (2/3)  Action Move around the game area Dribble and kick the ball  Developed in C++ using the Gapidraw graphics libraries  Once per frame 30 times per second  Game state includes Position and trajectory of all Players, the ball, and the Game score

MMLAB 10 Implementation : Knockabout (3/3)  Adaptation rule Priority (e.g.) Overall score > accurate position of player Ball > position of player  These prioritized adaptation rules allow the each user to control the local view of the game

MMLAB 11 Evaluation (1/2)  Comparison between The Rendezvous consistency mechanism And two alternative solutions Rollback (well-known consistency mechanism) control implementation (no consistency mechanism)  Distributed 4 player  Testing three consistency mechanisms at a given latency

MMLAB 12 Evaluation (2/2)  Evaluation Latencies

MMLAB 13 Consistency  Measurement of deviation  Consistency at 500ms in Rendezvous

MMLAB 14 Consistency  Consistency at 500ms in Rollback  Consistency at 500ms in Control

MMLAB 15 Consistency  Consistency at low latency in Rendezvous

MMLAB 16 Consistency  Consistency at low latency in Rollback  Consistency at low latency in Control

MMLAB 17 Conclusion  Compare with Rendezvous and Existing mechanisms  Rendezvous proved highly successful in high latency environments  Future work focusing on the use of more complex control theory

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