High-speed Data Transmission in Wireless and Mobile Networks3

8/7/2019 High-speed Data Transmission in Wireless and Mobile Networks3

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High-speed Data Transmission in Wireless andMobile Networks

Tomáš MáchaDepartment of Telecommunications

Brno University of TechnologyBrno, Czech Republic

[email protected]

Luboš NagyDepartment of Telecommunications


[email protected]

Jan OchodnickýDepartment of Telecommunications


[email protected]

Abstract—This article describes the comparison of Voice over IP

(VoIP) calls between two different access points. The first case is

focused on ordinary Wi-Fi access point enabling wireless

connection to hardware and software IP phones. The second

scenario is similar, except the Wi-Fi router is replaced by a Wi-Fi

hotspot created from a HTC mobile phone with Android 2.1

operating system. The goal of the research was to examine high-

speed data transmission in wireless and mobile networks.

Different plots of delay and jitter are analyzed and shown in the

article.

Keywords-Wi-Fi, hotspot, VoIP, SIP, 3G

I. INTRODUCTION

New mobile phones offer new possibilities in effective datatransfer. One of them is the opportunity to configure the mobilephone to a Wi-Fi hotspot. For our experimental network, theHTC Desire mobile phone was used. This mobile phoneenables Wi-Fi hotspot setup. The configuration can be used bythree different devices at the same time.

The idea was to connect Wi-Fi-based devices, such as Wi-Fi phones mutually or with notebooks containing Wi-Fimodule and installed software IP phone. One hardware IPphone was added for the possibility of comparison. Allmentioned software or hardware IP phones were based onSession Initiation Protocol (SIP). User’s accounts were createdin a SIP-based software exchange. This exchange is describedin the next chapter.

The experimental network was located at Department of Telecommunications at Brno University of Technology. TheHTC mobile phone contained an O2 SIM card. In this area, the

O2 operator offers 3G telecommunications network for thewireless transmission of data through radio signals with realspeeds of 3Mbit/s.

The Wi-Fi router was an N Gigabit router (802.11n)compliant device providing high-speed Internet access.

A. 3G WiFi Hotspot

The goal of a hotspot is to cover a public area with an802.11 signal. The hotspot is a site that offers an Internetaccess over a Wireless Local Area Network (WLAN) [1] withthe help of a device connected to an Internet service provider.

Wi-Fi technology is typically used for hotspots. The HTCDesire phone can be used as a portable Wi-Fi hotspot enablingphone’s internet connection to any other device in range via aWi-Fi connection. It connects to CDMA [2] networks at 3G

speeds. HTC Desire manages three devices connected to Wi-Fihotspot.

B. 3CX PBX exchange

3CX Phone System for Windows OS is a software-basedprivate branch exchange based on the SIP standard. This PBXis installed and managed via web interface. It supports IPhardware and software phones [3].

II. EXPERIMENTALNETWORK TOPOLOGY FOR HOTSPOT

The experimental network was created of several wired andwireless end devices. However, only two of them wereconnected to each other for VoIP connection. No conferencecall was originated. Table 1 defines all used devices for the

experimental network. The IP address of Linksys 1 wasassigned by the network. The other IP addresses were fixed.

TABLE I. EXPERIMENTAL NETWORKS SETUP

Device Tel. number IP address

Linksys 1 100 85.160.188.105

Linksys 2 101 147.229.151.210

VIP-153T 102 147.229.151.71

Notebook 104 147.229.151.100

3CX PBX - 147.229.151.105

HTC Desire - -

A. SIP phone to Wi-Fi phohe connection

The first connection was established between a SIP phone(VIP-153T) and a Wi-Fi phone (Linksys 1). The logicaltopology is shown in Figure 1.

The mobile phone with Android OS represented a Wi-Fihotspot. In this scenario, one device was connected to thehotspot, namely Wi-Fi phone Linksys. The Android phoneused 3G connection for data transmission over the O2 operator.Afterwards was the data transmission processed through theBrno University of Technology network up to the PBXsoftware SIP exchange 3CX PBX. This PBX represented an



Asterisk solution for OS Windows. The PBX exchangecontained users account information. To the exchange was alsolinked the hardware SIP phone.

Figure 1 The logical topology of SIP to Wi-Fi phones connection usinghotspot

B. SIP phone to Wi-Fi phone connection

The second scenario was focused on connection betweenthe software IP phone (X-Lite) and the SIP phone VIP-153T.The logical topology of this established connection is shown inFigure 2.

The second topology is very similar to the previous oneexcept one device change. The Linksys phone was replaced bya computer with installed software IP phone called X-Lite. Thesoftware phone user account was also controlled by the 3CXPBX.

Figure 2 The logical topology of X-Lite to SIP phones connection usinghotspot

C. Wireless software IP phone to Wi-Fi phone connection

The last scenario of this type of experimental network wasfocused on connection between the software IP phone (X-Lite)installed on the notebook (wireless connection) and the Wi-Fiphone Linksys. The logical topology of this establishedconnection is shown in Figure 3.

Wi-Fi phone

Wi-Fi hotspot

(Android)

X-Lite phone

3G

(O2)

SIP

PBX

O2 operator Brno University

Of Technology

Figure 3 The logical topology of two wireless end devices connected to theWi-Fi hotspot

III. EXPERIMENTALNETWORK TOPOLOGY FOR WI-FI

ROUTER

This type of network used an ordinary Wi-Fi router for datatransmission between end users and SIP PBX. Another threescenarios were measured. These scenarios are similar to theprevious ones. The difference is in the access point. The HTC

hotspot was replaced by the Wi-Fi router mentioned before.A. SIP phone to Wi-Fi phohe connection

Figure 4 illustrates the configured network for another typeof call. In this case, one end device, namely SIP phone waslinked to the exchange and the second one (Linksys)represented the wireless connection.

Figure 4 The logical topology of SIP phone to Wi-Fi phone connectionusing Wi-Fi router

B. Wireless software IP phone to SIP phohe connection

Figure 5 illustrates the second scenario for Wi-Fi router.SIP phone is connected to the X-Lite software via Wi-Firouter and the users are controlled by the PBX.

Wi-Fi phone

SIPPBX

Wi-Fi router

SIP phone



Figure 5 The logical topology of VIP-153T phone to software IP phoneconnection using Wi-Fi router


Figure 6 illustrates the network configuration of aconnection between wireless end devices, namely the Wi-Fi IPphone and the X-Lite software IP phone.

Figure 6 The logical topology of X-Lite to Wi-Fi phones connection usingWi-Fi router

IV. RESULTS AND COMPARISONS

For each one scenario were performed three calls for moreaccurate measurement. One call took 30 seconds. Delay andjitter plots of all scenarios are illustrated in results. Theestablished connections were monitored and investigatedthrough a packet analyzer Wireshark.

As mentioned before, HTC desire contained O2 SIM card.The information about serving cell follows in Table 2.

TABLE II. O2 SERVING CELL

Name: Value:

Operator O2Type UMTSLAC 3811CID 40238PSC 3801Signal -83dBm

For the hotspot scenarios, the maximal delay was around

60ms. There were some packets which got over 1s but thisdisruption was caused by the load along the path of packets.The packet lost was 0.0%. The maximum jitter was 35ms andthe mean jitter around 5.8ms. According to ITU-T specification[5] for voice quality is the network configuration good forvoice transmission.

For the Wi-Fi router scenarios, the maximal delay wasaround 22ms. Some small inaccuracies were detected, but itwas probably caused by the network background load. Thepacket lost was 0.0%. The maximum jitter was 16ms and themean jitter around 3.7ms.

These measured values are noted for good quality of voiceover data networks according to ITU-T specifications [5].Good results were expected because of minimal network loadand the effective use of the network.

A. SIP phone to Wi-Fi phohe connection results

Figure 7 illustrates the plot of measured delay for SIPphone and Wi-Fi phone Linksys. A red curve indicates

average delay for calls processed via Wi-Fi router and a bluecurve indicates the average delay for calls via hotspot. It canbe seen that the red curve runs around 20ms of delay. The bluecurve noted expected fluctuation caused by the load and alongthe packet’s path through the network. Also according toexpected results, the jitter (Figure 8) noted steady state for Wi-Fi router and fluctuated state for hotspot calls. The jitter iscaused by queuing, contention and serialization effects on thepath through the networks.

Figure 7 The comparison of measured delay for SIP phone and Wi-Fi phone

Figure 8 The comparison of measured jitter for SIP phone and Wi-Fi phone

B. Wireless software IP phone to SIP phohe connection

results

Figure 9 shows the measured delay for SIP phone andsoftware X-Lite phone. A red curve indicates average delayfor calls processed via Wi-Fi router and a blue curve indicatesthe average delay for calls via hotspot. It can be seen that thered curve is steady around 20ms of delay. The blue curvenoted expected fluctuation. Figure 10 depicts the jitter

X-Lite

SIPPBX

Wi-Fi router

SIP phone

Wi-Fi phone

X-Lite phone

SIPPBX

Wi-Fi router



according to expected results. Performed calls via hotspotnoted increased and fluctuated jitter.

Figure 9 The comparison of measured delay for SIP phone and X-Litephone

Figure 10 The comparison of measured jitter for SIP phone and X-Lite phone


results

This scenario is very similar to the previous ones. Again,the red curve indicates calls through the Wi-Fi router and theblue curve indicates calls through the hotspot. The averagedelay (Figure 11) is about 20ms and average jitter (Figure 12)did not cross over 6ms.

Figure 11 The comparison of measured delay for Wi-Fi phone and X-Litephone

Figure 12 The comparison of measured jitter for Wi-Fi phone and X-Litephone

V. CONCLUSION

The real-time multimedia services for transmittinginformation under the certain QoS parameters are one of themost actual issues in telecommunication world. In this article,

the comparison of two different types of networks is described.The first one is focused on 3G Wi-Fi hotspot created from aspecial mobile phone. The second one is represented by anordinary Wi-Fi router.

The issue of QoS refers mainly to the quality of the packetnetwork. The ability of the network to provide required QoS tothe user depends on particular parts of the network. It meansthat the QoS depends on the weakest element of the network.

The delay and jitter for hotspot scenario calls werecharacterized by fluctuation caused by different actions andload in the network along the packet’s path, especially in 3Gnetwork. On the other hand, the delay and jitter for Wi-Firouter scenario calls remained steady without any disturbance.

There were no Mean Opinion Score (MOS) measurements butaccording to objective perception, the Wi-Fi router calls werecharacterized by higher quality.

The real measurements follow expected results. Both typesof scenarios offer good voice quality according to ITU-T.

ACKNOWLEDGMENT

This project was supported by the FRVŠ 2986/2010.

REFERENCES

[1] J. Ross, “The book of Wi-Fi: install, configure and use 802.11b wirelessnetworking,” San Francisco, 245p., 2003. ISBN: 1-886411-45-X.

[2] H. Holma, A Toskala, “WCDMA for UMTS: HSPA evolution and LTE”

5th ed., Wiley, 2010, 597p. ISBN: 978-0-470-68646-1.[3] 3CX PBX Brochure. 2010. www.3CX.com.

[4] T. Macha, “Analýza komunikace př i realizaci VoIP spojení.”Elektrorevue - Internetový časopis (http://www.elektrorevue.cz), 2008,roč. 2008, č. 12, s. 1-11. ISSN: 1213- 1539.

[5] ITU-T. Series G: Transmission systems and Media, Digital Systems andNetworks. International telephone connections and circuits – GeneralDefinitions. The Emodel, a computational model for use in transmissionplanning. Recommendation ITU-T G.107. May 2000.

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High-speed Data Transmission in Wireless and Mobile Networks3