Measuring Online Game Application in GPRS and UMTS

Measuring Online Game Application in GPRS and UMTS Author: Anssi Hämäläinen Supervisor: Professor Raimo Kantola Instructor: Mikko Mäkinen M.Sc. (Tech.)

Contents • Scope definition • Research problem and objectives • Online game applications and architectures • Performance • Measurements • Results • Conclusions • Future research

Scope definition • The scope is limited to existing mobile networks (GPRS, EDGE and UMTS) in a controlled laboratory environment and the measurements are done by using one selected real-time online game application. • GPRS (General Packet Radio Service) • EDGE (Enhanced Data Rates for Global Evolution) • UMTS (Universal Mobile Telecommunications Systems) • UMTS uses WCDMA (Wideband Code Division Multiple Access) radio access

Research problem and objectives • The Research problem is to investigate the possibilities to use mobile networks for online gaming and especially for real-time gaming • The goal of this thesis is to study how the online game applications work in the 2G and the 3G mobile communication systems • The main objective of this thesis is to measure the online game performance over the mobile networks • The second objective of this thesis is to evaluate the online game application latency derived from each of the mobile networks and to compare them with each other • The target of this research is to find out the potential of the mobile networks for real-time gaming

Online game applications • Real-time action games • usually contain virtual people moving in a real–time virtual environment • have real-time requirements, meaning that a certain delay and bit rate need to be guaranteed by the network in order to provide an acceptable end-user quality • Real-time strategy games • although this type of game has an interactive nature, normally higher delays can be accepted than in action games • Turn-based games • have the loosest delay requirements, allowing even several seconds between any interactions between players

Online game architectures • Game server in network • In this architecture one node acts as the game server • This architecture avoids the game state inconsistencies of peer-to-peer architecture by limiting game control to one server node • The players receive all necessary state information over the network from the server • Peer-to-peer gaming • The traditional approach and does not use a game server • Player actions are broadcasted over the network to all the other players in the game • This approach requires a very reliable communication link, because any lost or corrupted data can easily lead to inconsistencies between the perceived game states of individual players

Performance • There are three main factors that cause lag in online-games: high network latency, packet loss, and insufficient bandwidth • Latency • The latency of a connection is the time it takes for a packet to travel from the source to the destination host • Packet loss • Packet loss occurs when the network is congested • Bandwidth • Bandwidth is the amount of information that can be transmitted over a connection in a given amount of time • Bandwidth is the limiting factor in mobile networks (GPRS) • Bandwidth requirements tend to increase with the number of players participating in a game

Round trip time (RTT) • RTT is an essential feature for online game applications and affects the gaming performance • RTT was measured by using a protocol analyzer • RTT is possible to be calculated from the packets’ sending time and receiving time RTTAB = TAreceive packet 2 – TAtransmit packet 1 – (TBtransmit packet 2 – TBreceive packet 1)

Acceptable quality from the end-user point of view • The RTTs will be estimated and compared with different thresholds, that define the maximum delays for experiencing a good or acceptable quality from the end-user point of view The estimated RTTs for experiencing a good or acceptable quality from the end-user point of view:

Measurements • In the measurements the main objective was to find out the differences in the RTT in the UMTS, EDGE and GPRS networks • Another objective was to measure the performance over the UMTS emulator and to find out the one-way transfer delay for uplink and downlink directions. • The connection time to the game server was also measured in the emulated UMTS.

Measurement set-up for emulated UMTS Network • The emulator is a flexible research, development and testing environment, that can be used to emulate fixed and / or wireless network transport

Measurement set-up for real UMTS, EDGE and GPRS networks in a laboratory

Measurement tools • Protocol Analyzer • The protocol analyzer is a program or a device, which can capture traffic over a given interface and usually can decode it to be readable by people • In this research a protocol analyzer is used to capture traffic timestamps from which the end-to-end delays and all the needed results can be calculated • Automation Language • In this research an automation language is used to help to measure the connection time to the server • Automation language is useful for repetitive measurements

Measurement application • Application: A Real-Time Action Game • There is a wide range of real-time online action games on the market and one of them was selected for the measurements • The selected application is a very popular first person shooter (FPS) game, because it is a freeware product and designed for network environment • This real-time action game is an online game application for multiple players • The minimum requirements for the network game are a modem or a better Internet connection or a LAN network

Results in real networks • The RTTs were measured over all the three mobile networks in a laboratory environment • The average RTTs were 150,0 ms in UMTS, 696,7 ms in EDGE and 896,6 ms in GPRS • The average RTT in GPRS is about six times higher than in UMTS • The average RTT in UMTS is good enough for online game applications and real-time action games • The EDGE and GPRS networks are more suitable for applications which do not have critical delay requirements

Average RTT • The average RTT in UMTS, EDGE and GPRS

Packet size • The average packet sizes in UMTS, EDGE and GPRS

Packet loss rate • The packet loss rate in UMTS, EDGE and GPRS

Conclusions • In this thesis the online game performance over the mobile networks was measured • The measurements were done with real networks and an emulator • According to the measurement results the RTT delay performance is good for real-time online action games only in UMTS • In EDGE and GPRS the RTT delay performance is too low for real-time action games • The needed throughput in the uplink direction is too high to be transferred over GPRS • For that reason, the packet loss rate rises too high in the uplink direction and playing is impossible • The online game performance between the different network technologies depends on the specifications (3GPP), and especially on the radio interface specifications

Conclusions • There are lower data rate capabilities in GPRS and EDGE than in UMTS • The frame length in UMTS is different from GPRS and EDGE frame length and affects the performance • The performance values are also dependent on the network configurations • Mobile networks are designed to provide higher data speed in the downlink direction than in the uplink direction • According to the measurement results, when two clients are playing, more bandwidth is needed in the uplink direction than in the downlink direction • This feature is not a problem for UMTS or EDGE performance, but it would affect GPRS performance results

Future research • A study of the online game application in wireless packet networks with more than only two players • Another interesting research objective could be the high-speed downlink packet access (HSDPA) • HSDPA technology will reduce the delay and the online game performance should be improved

Measuring Online Game Application in GPRS and UMTS