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
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
B
D
A
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
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:
Pauses:
single talk & double talk
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)
 No
400ms (tolerable)
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
Latency
NimbusCast
QuadCast
SectorCast
Low
High
Medium
Drop rate
High
Medium
Low
Computation
Low
(none)
Medium
(grouping)
High
(sorting)
Scenarios
Low density
Uniform
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!
Adaptive Computing and Networking Lab, CSIE, NCU