TEL 500
Reaction paper 1
Voice Communications
To Build Context-Aware VoIP Support using Session Initiation
Protocol
Submitted to Prof. Ronny Bull
By
Prasad S V L N Vunnam
About the Paper:
The authors of this paper is Aameek Singh and Arup Acharya. This paper deals with creating
realistic environment to the gamers while playing the games. The main intention of these authors
is using protocols such as Voice over Internet Protocol (VoIP) and Session Initiation protocol
(SIP), they wanted to make the gamers play in a realistic manner mainly or multiplayer
networked games. Generally in multiplayer games, gamers from nook and corner of the globe
play the same game at a time. Therefore, they need to interact each other such as instant
messaging, commenting, voice calling etc. so that they’ll enjoy major part of the game. While
playing all the above said operations, everything must be real time and must function according
to the game environment.
Usually this is not possible as there may be lag in any such parameters. The authors of this
paper tried to enhance all these parameters and proposed few protocols for creating a real time
instant messaging, real time voice between players using Voice over Internet protocol (VoIP).
Various Gaming Networking Methods:
In market there are various gaming consoles such as Xbox, play station, Gamespy Arcade etc.
which are compatible for the games like role play games (RPGs) where the player acts as a
character and he enters into the gaming environment. As these kinds of consoles create a live
environment just visually, we need to create a live environment in every aspect such that the
gamer should even interact with the other members in the game as he is in the field along with
the other gamers from different parts of the world. So the proposed technology to create an
effective realistic environment is using Session Initiation Protocol (SIP), VoIP conferencing.
There are many limitations while playing a game. They are:
1) Game context independent.
2) User initiation requirement
3) Operation of console
The main problem even though there is interaction between the players, that interaction will not
be game dependent. So what the author tried to do is to create a game dependent environment so
that gamers play with much more interest.
There may also be user initiation requirement. This means that if there is change in the game
context, generally the user/gamer needs to change the environment manually. But what the
authors want is that when the game context changes, the environment of the user should also
change automatically.
The VoIP technologies used by different consoles are different which bind the users to their
consoles itself. This is the major drawback with the gaming consoles. In order to experience the
best gaming, all the gaming consoles should use the same VoIP technology so that the consoles
are generalized.
These are the major drawbacks with the present gaming. These drawbacks should be overcome
so that the gamers will get the best gaming experience.
Proposal of new technologies:
The main goal of authors is to make tight bond between voice communication and the gaming
environment. This is possible by coupling SIP protocol with VoIP conference server which
allows the gamers to communicate directly.
The other goal is to provide seamless relaying of gaming environment where the user doesn’t
involve in this process. This is all possible using SIP.
There is also need of dynamic audio sessions, which enables other people to join the conference
in an ongoing game.
Other last goal is to allow audio mixing which provides real world and real time gaming
experience.
These are the possible technologies, authors have proposed.
VoIP and SIP:
Using SIP and VoIP protocols, sending of voice data on IP network is possible. The
communication is enabled between two users by commands such as INVITE, OK and ACK to
the response. The INVITE command sends an invitation to the opponent, if the opponent accepts
the command by OK command, the acknowledgement ACK is sent to the opponent who sent the
INVITE command. Then the connection is established between the two gamers. Then they can
have a real time voice communication. These commands contain user parameters which contains
IP address and the port to which the conference must be established. These all can be possible
using Session Description Protocol (SDP). The data is sent to the opponent using Real time
Protocol (RTP), and signal is established using Transport Control Protocol or User Description
Protocol (UDP) which contains all the opponents IP addresses and ports.
The SIP based VoIP architecture consists of location server, redirect server, registrar server,
proxy server user agent and gateway. Location server, redirect server, registrar server are all SIP
components. Registrar server maintains the address of gamer’s console. There will be a location
server at the area of the gamer. Both the servers are connected to the redirect server which will
connects each. Initially, the user sends the INVITE command. This command passes through the
proxy server. In parallel, the address of the location of the gamer is also sent and the gamer
registers in the registrar server. When everything is one, the commands passes through the PSTN
from the gateway. There will be same architecture in the opponent side. He just accepts the
command and then acknowledgement is sent back to the gamer1. This is some kind of
handshaking process. There are many commands such as RE-INVITE to establish the connection
one again, REFER to refer a known gamer into the current ongoing game, BYE command to
terminate the connection.
Architecture of SIP:
SIP is used to establish audio conference between the gamers within the group of the particular
game. This is somewhat similar to the conference done using PSTN. In SIP based conferencing,
there will be a mixer where all voices from the user agents are mixed and sent to the conference
server. This server initiates the conference between each and every gamer. Here everything is
full duplexed. This sort of communication can be done irrespective of the console. It may be an
IP phone or PSTN Phone or Soft phone. The address if each user will be in the form
sip: conference_id @conference_server.
Gaming Infrastructure and its Integration:
There are two kinds of gaming. They are centralized gaming and decentralized gaming.
Centralized gaming is having few issues that are solved in decentralized gaming. The issues are
scalability where the system cannot handle more incoming connections and reliability where we
cannot estimate performance. In centralized gaming there is a game server which is SIP enabled,
a CS server and a mixer all connected to user agents where as in decentralized gaming there will
not be any SIP enabled game server. There will be only conference server and mixer connected
to user agents. Hence when the user changes the game environment, then the audio session also
changes directly without any initiation which will not happen in centralized gaming.
Various Conferences:
In gaming there are two kinds of conferences.
1) Static gaming conference.
2) Dynamic gaming conference.
In static gaming conference one who comes first initiates the conference. In this the conference is
static irrespective of the state of the game. Where as in dynamic conferencing, the conference is
dynamic that is the conference changes when the game scenario changes.
There should also be a seamless transition of the conference so instead of terminating the
conference just RE-INVITE command is necessary so that again the gamer joins the conference
without establishing the connection once again.
Using ADHOC:
By using ADHOC, the gamers can join the conference even in the middle of the game. No
resource is reserved and is automatically added to the new comer. Therefore there won’t be any
burden on the game server to reserve the resource for the client.
There may also be sub-interactions within the group or with the opposite group which makes the
game very interesting. Normally this is impossible with the game server and this come under
violation of rules. But this can be done using ADHOC conferencing so that the conference can
be started while the game is already in progress and there won’t be any need to initiate the
conference again.
Audio Mixing:
Author proposed audio mixing also to improve the reality of the game. The audio signals are
converted into 1s and 0s and are processed in such a way that the audio levels change depending
upon the position of the player in the game. For example if the player is nearer to other player
then the user agents of that positions hears loud voice. Similarly if the position is far away the
user agent hears soft voice. This creates a real time gaming experience.
Critics:
The authors concentrated much on creating the game environment realistic by enabling the user
agents to have a real time conference. So that they get much involved in the game and can have a
good real time gaming experience. Combining all the above said technologies the authors also
made a prototype at IBM T.J. Watson Research Centre where they achieved their goals for
creating a realtime gaming experience.
Extensions:
Authors proposed every possible way for making the gaming environment realistic. It would be
much more realistic by changing the pitch and intensity of the voice by taking the climate, wind
and the other surroundings into consideration and but not only in audio but also should improve
in video such as the user agent must feel that the agent is really in the field.
References:
ADHOC from http://tools.ietf.org/html/rfc2501
SIP from http://www.rfc-base.org/rfc-3261.html
VoIP
from
https://www.cisco.com/application/pdf/en/us/guest/tech/tk587/c1506/ccmigration_09186a00801
2dd36.pdf