Peer-to-Peer AOI Voice Chatting for Massively Multiplayer Online Games (P2P-NVE 2007 workshop) Jehn-Ruey Jiang and Hung-Shiang Chen Adaptive Computing and Networking Lab Dept. of CSIE, National Central University, Taiwan

Adaptive Computing and Networking Lab, CSIE, NCU Communications in MMOGs Massively Multiplayer Online Games (MMOGs) are growing rapidly  World of Warcraft: 9 million subscribers  500,000 concurrent users Players often type and read text instead of speaking and listening

Adaptive Computing and Networking Lab, CSIE, NCU Player-initiated solutions Teamspeak, Ventrilo, Skype  Set your own voice server  Group chat for 5 (skype) to ~10 (teamspeak) But…  Need to set up own server (s)  Support only limited, fixed user group  Explicit / preconfigured joining required

Adaptive Computing and Networking Lab, CSIE, NCU Voice chat with fixed membership A B D C E

Adaptive Computing and Networking Lab, CSIE, NCU A better scenario… AOI voice chatting  Each player listens and talks to all users within its AOI (area of interest)  More natural  More realistic Our proposal  If neighbors are known  Talk to them directly

Adaptive Computing and Networking Lab, CSIE, NCU Voice chat with dynamic membership A

Adaptive Computing and Networking Lab, CSIE, NCU A simple approach NimbusCast:  MMOG system first provides a list of AOI neighbors  individual voice packets for all AOI neighbors

Adaptive Computing and Networking Lab, CSIE, NCU But… bandwidth overload occurs Number of supportable users very limited  256 kbps / 16 kbps = 16 users (theoretical maximum)

Adaptive Computing and Networking Lab, CSIE, NCU Human conversation model Conversations are made of short bursts of voices  Talkspurts:single talk & double talk  Pauses: gaps in speech or mutual silence A person only talks 40% of time Talking rate of a listener is 6% [ITU-T, 2003]

Adaptive Computing and Networking Lab, CSIE, NCU Our proposal Observation: idle bandwidth can be used to forward voice packets, supporting more users Under two goals:  Reasonable delay [ITU-T P.59] 150~250ms (good) 400ms (tolerable)  No bandwidth overload: Voice bursts should not exceed bandwidth limit

Adaptive Computing and Networking Lab, CSIE, NCU QuadCast Quadrant-based Forwarding  A list of AOI neighbors is first obtained from the MMOG system  Voice packets sent to forwarding assistants (FAs)  FAs then forwards to remaining AOI neighbors in each quadrant  A recipient list is attached to the packet, and continuously divided

Adaptive Computing and Networking Lab, CSIE, NCU Player clustering in MMOGs In MMOG, players usually group at some hot-spots End-to-end latency in some quadrants may be long

Adaptive Computing and Networking Lab, CSIE, NCU SectorCast Similar to QuadCast except in player grouping Players are grouped into four sectors with equal sizes according to polar angles

Adaptive Computing and Networking Lab, CSIE, NCU Packet aggregation Different packets might be sent to the same target:  Header sharing (HS)  Voice mixing (VM)

Adaptive Computing and Networking Lab, CSIE, NCU Evaluation Simulation parameters  200 ~ 1000 nodes (in 200 increments, i.e. 8 ~ 40 AOI neighbors)  1000 x 1000 area  AOI radius: 100  40% talking, 60% silent  Random movement model (10 units / step)  1000 time-steps of 100ms intervals  40 bytes header  100 bytes voice  256 kbps upload

Adaptive Computing and Networking Lab, CSIE, NCU Alternatives to recipient list The recipient list incurs bandwidth overhead Trade communication with computation Append just the ID of the current FA to next FA Next FA determines forwarding area based on position & AOI of the speaking node SectorCast requires begin & end angles as well

Adaptive Computing and Networking Lab, CSIE, NCU Total upload bandwidth (unlimited b/w)

Adaptive Computing and Networking Lab, CSIE, NCU Total upload bandwidth (limited b/w)

Adaptive Computing and Networking Lab, CSIE, NCU Dropping rate (limited bandwidth)

Adaptive Computing and Networking Lab, CSIE, NCU Average latency (in hop counts)

Adaptive Computing and Networking Lab, CSIE, NCU Comparisons LatencyDrop rateComputationScenarios NimbusCastLowHigh Low (none) Low density QuadCastHighMedium (grouping) Uniform SectorCastMediumLow High (sorting) Clustering

Adaptive Computing and Networking Lab, CSIE, NCU Conclusion AOI voice chatting proposed for MMOGs Idle bandwidth & human behavior exploited  Lower dropping rate & bandwidth overloading  QuadCast:suitable in uniform distributions  SectorCast:suitable in clustered distributions Usable with both client-server or P2P MMOGs

Adaptive Computing and Networking Lab, CSIE, NCU Q & A Thank you!