Traffic load analysis in mobile network implemented in Vala-PTK

Abdullah Havolli, Valdet Shabani, Arianit Maraj

Post and telecommunication of Kosova

Dardania no nr. Prishtina 10 000, Republic of Kosova,

abdullah.havolli@ptkonline.com, valdet.shabani@ptkonline.com, arianit.maraj@ptkonline.com

Abstract- Since first generation of mobile communication has been based on analog technology. After this, is

implemented second-generation (2G) of digital cellular networks, based on global system for mobile

communications (GSM) technology. GSM technology is represented for the first time in the early 1990s and is

digital technology. After this the technology has advanced to GPRS/EDGE , 3 G and finally in 4 G technology.

PTK as incumbent operator always seeks for ways to implement new technologies in mobile platform. At the

beginning (in 2000), the mobile network of VALA in PTK has been based on GSM technology, but later PTK

has implemented EDGE technology, and now has also upgraded network which is ready for 3G network

implementation. In this paper we will analyze traffic load in different segments of VALA network which is

implemented in PTK.

Key words: GSM, traffic load, quality, mobile

1 Introduction The wireless technology in general experienced a

substantial growth since the first generation of

mobile network. Since then, GSM technology has

become the dominant global 2G radio access

standard. Almost 80% of today’s new subscriptions

take place in one of the more than 460 cellular

networks that use GSM technology. This growth has

taken place simultaneously with the large

experienced expansion of access to the Internet and

its related multimedia services. Cellular operators

now face the challenge to evolve their networks to

efficiently support the forecasted demand of

wireless Internet-based multimedia services [1-3].

VALA as first operator of mobile communication in

Kosovo market also has done a much efforts in

leading not just with the services but also with

technology.

Vala mobile operator since the beginning of

the operation till now has been developed in six

different phases. This development was made with

the purpose of increasing the capacity, quality of

services and release of new services and products

based on customer’s demand. At the beginning of

the operation in the VALA network capacity was 30

000 MS, and today has been grown to 1 800 000

MS. This is a very significant growth for every

operator worldwide, not just for VALA.

In 2008 the capacity of VALA was

increased from 700 000 MS to 1 200 000 MS and

70% of capacity passes in NGN. In 2011 the

capacity of VALA was increased from 120 000 MS

to 1 800 000 MS, and switching all network of

VALA in NGN.

The structure of this paper is like below: In

section 2, we have explained into details the

architecture of VALA network implemented in

PTK, including here the detailed explanation of all

corresponding elements of this architecture. In

section 3 we have explained services offered by

VALA platform, including value added services.

Whereas, the section 4 shows the traffic load

analysis for VALA network in PTK.

2 Architecture of VALA network

implemented in PTK The network architecture of VALA is divided in two

different Cities of Kosovo: Prishtina and Prizren.

These two Cities are the biggest one in Kosova and

have the biggest number of customers. The main

reasons for this distribution of network elements in

to two different Cities is due of natural disaster, fire

etc. If any disaster happens to one of our cities

where our equipments are located then the network

elements located in the other city will take over the

operation and the network will continue working

without interruption.

The network architecture of VALA, as seen

in a figure below (figure 1), constitutes of one WCS

(Wireless Call Server) and two MGW (Media

Gateway). Those together form a MSC (Mobile

Switching Centre). In Vala network platform there

are implemented two MSCs and two VLRs (Visitor

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ISBN: 978-1-61804-164-7 222

Local Register). One MSC and one VLR are located

in Pristhina and the other MSC and VLR are located

in Prizren. The network of VALA has also two

HLR (Home Local Register). One HLR is set in

Prishtina and it is active, the other one is set in

Prizren and is in standby mode. The platform of ICC

(Instant Convergent Charging), SMSC (Short

Message Service Centre), VMS (Voice Mail),

SGSN (Serving General Packet Radio Service

Node) and BSCs (Base Station Controller) are

located in Prishtina. Two SRPs (Signaling Resource

Point) and five BSC (Base Station Transceiver) are

located in Prizren. Network architecture and its

corresponding elements are better seen in the figure

1.

MVNO

WCS2

MGW1

MGW2

SMSC SGSNICC

VMS

WCS1

MGW4

MGW3

PSTN

International

GW

HLR HLR

BSC2 BSC7BSC6BSC5BSC4BSC3BSC1 BSC13BSC12BSC11 BSC9BSC8BSC10 BSC14

SRP1 SRP2

ngHLR Primary ngHLR Back - up

PRISHTINA PRIZREN

Signaling

Voice

BSC15

Figure 1. VALA network implemented in PTK

The architecture of VALA network is designed to

have capacity of:

- 36 mErlang/MS

- 40 000 TCH

- 593 BTSs (Base Transceiver Station)

- Coverage 100% of populated territory

This capacity is designed to be for 1 800 000 MS

(Mobile Subscribers),

In the section below, we will explain

shortly all of the network elements and their role

for offering services.

In the VALA platform, one of the main

components is Wireless Call Server, The main

components of WCS are listed like below:

• Call processing centre

• Media Gateway Controller H.248

• SS7 Signaling

• SIGTRAN (M3UA)

• Designed to 3GPP standards

• PSTN signaling interfaces

• Element Management Host

The Mobile-services Switching Centre (MSC)

constitutes the interface between the radio system

and the fixed networks. The MSC performs all

necessary functions in order to handle the circuit

switched services to and from the mobile stations.

The MSC Server mainly comprises the call control

(CC) and mobility control parts of a MSC. The

MSC Server is responsible for the control of mobile

originated and mobile terminated CS Domain calls.

It terminates the user-network signaling and

translates it into the relevant network – network

signaling. The MSC Server also contains a VLR to

hold the mobile subscriber's service data.

The MSC Server controls the parts of the call state

that pertain to connection control for media

channels in a MGW. A MGW may terminate

bearer channels from a switched circuit network

and media streams from a packet network (e.g.,

RTP streams in an IP network). Also, MGW may

support media conversion, bearer control and

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payload processing (e.g. codec, echo canceller,

conference bridge).

3GPP R4 introduces the Next Generation

Network (NGN) concept in the Mobile network.

Transport and Control layers are handled by

separate equipment, the MSC server and the MGW.

On the other hand, Access and Services remain

performed by the UTRAN and the Application

platforms (IN, SAT, …).

The Visited MSC Servers and Gateway MSC

Servers respectively connect to the UTRAN/BSS

and the PSTN. They are mainly in charge of:

Call Control Handling

Media Gateway Control.

There are two kinds of 3GPP R4 Media Gateways,

which are implemented in VALA’s network:

The Access Media Gateway (A- MGW),

The Trunk Media-Gateway (T- MGW), also

called BorderMedia-Gateway (B-MGW)

The A- MGW is at the border between the

Terrestrial Radio Access Network (UTRAN and /or

BSS) and the Circuit Switched Core Network (Cs

CN).

The T- MGW is at the border between the

Cs CN and the Public Switch Transport Network

(PSTN). A- MGW main function is to perform the

switching between the UTRAN and another MGW

which can be a T- MGW or another A- MGW.

The main function of T- MGW is to

support the interworking between the Cs Backbone

and the PSTN. This interworking mainly includes

transcoding and media adaptation. Note that A-

MGW and T-MGW functions can be supported by

the same gateway, resulting in the simultaneous

support of Radio Network and PSTN interfaces in

the same equipment.

The most important register in mobile

networks is HLR (Home Location Register). HLR

is a reference database where the following

information is stored:

- Identities of the subscriber (international

identity, directory number)

- subscribed services

- Rough location of the Mobile Station

(identification of the VLR where the MS is

now registered)

Knowing that the security is the key parameter

in every mobile network, the VALA has also paid a

special attention for installing AuC center. This

center is part of HLR. The AuC (Authentication

Center) is the Security Database of GSM which

generates the parameters used during the

Authentication and Ciphering procedures.

Another register that is also important and is part

of MSC, is VLR. The VLR (Visitor Location

Register) is associated with one or more MSC. It is

a local database with the following information:

- Copy of the HLR data for visiting subscribers

- More precise location of the Mobile Station

(an area of the network called “Location Area”

which is a group of cells

- Call re-direction data

Short Message - Service Center: Is the most

important center that is implemented in VALA

PTK, and has the duties like below:

- The SMS-C is used to manage 160 character-

messages for Mobile Stations (back-up,

transmission / reception).

- When an MS is not reachable (SMS-MT, the

message is stored in the SMS-C and when the

MS switches on again, the SMS-C is informed

by the HLR so that the message can be sent.

- The SMS-C may be coupled with a voice mail

server.

PCU (Packet Control Unit): PCU is also installed

in VALA mobile technology and the main duties

are like below:

- Packet segmentation/re-assembly and

scheduling

- Radio channel access control and management

- Transmission error detection and

retransmission (ARQ)

- Power control

SGSN (Serving GPRS Support Node): is the

interface to the BSS and enables the following

functions:

- GPRS Mobility

- GPRS ciphering (used to provide

confidentiality and integrity protection of

GPRS user data between MS and SGSN)

- Charging

An important part of the mobile network is also the

billing technology. In VALA network as part of

billing is implanted ICC (Instant Convergent

Charging) suite. ICC provides a centralized rating,

charging and mediation capability to

simultaneously support unique tariff plans for:

- Wireless and wireline networks, including 2G,

2.5G, 3G, IMS, NGN, CDMA, GSM and

PSTN

- Voice, SMS, data, video, content/commerce

services

- Prepaid, postpaid and hybrid accounts

These plans help service providers to maximize the

available yield from their subscriber base.

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ISBN: 978-1-61804-164-7 224

implemented in VALA mobile network (with the

corresponding functions) are:

BTS: Base Transceiver Station

- Physical Channel Management

BSC: Base Station Controller

- Logical Channel Management

- Management of interfaces with NSS and OSS

- BTS monitoring

This is the radio part of VALA-s network which is

directly connected to customers.

3 Services offered by VALA

platform

Telecommunication capabilities that the customer

buys or leases from a service provider. Service is

an abstraction of the network-element-oriented or

equipment oriented view. Identical services can be

provided by different network elements, and

different services can be provided by the same

network elements. A set of functions and facilities

offered to a user by a provider.

In this definition, the "user" and "provider"

may be a pair such as application/application,

human/computer, and subscriber/organization

(operator). The different types of service included

in this definition are data transmission service and

telecommunications service offered by an operating

agency to its customers, and service offered by one

layer in a layered protocol to other layers. VALA

as the firs mobile operator in Kosova, offers a lot of

services to 1.2 million of customers. NGN

platform of VALA platform enable to have a

converged services that are very attractive for

customers. The main services that VALA offers

are: voice, sms, roaming, EGPRS/internet, MMS,

VAP, prepaid, postpaid, e-topup, family & friends,

welcome smsetc.

4 Traffic load analysis in mobile

network in PTK Analysis between 2 MSC-s

First, we have made some analysis between WSC1

and WSC2. The segment where we have maid

these analysis is shown in figure 2.

WCS1 WCS2

Figure 2. Network segment between WCS1 and WCS2

In figure 3, we have shown analysis that we made

in this real network-VALA network. We have

analysed the traffic load for a certain period of 1

month, from 09/11/12-09/12/12. As we can see,

the maximum load during peak hours is about 55

%. This percentage can be higher in a cases when

there is any special event, like new year. But, in

most of cases this value stands for every month of

the year. This traffic load is not too high and

doesn’t affect quality of services. This means that

in this segment of network, everything is according

to recommandations for QoS and QoE.

Figure 3. Analysis in network segment WCS1-WCS2

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Analysis between MSC and BSC-s

First scenario: WCS1- BSC1, BSC2, BSC3,

BSC4, BSC5, BSC10, BSC11, BSC12, BSC13 and

BSC14

In order to have a clear picture of traffic

load in VALA-s network, we have seen reasonable

to make some analysis between MSC and BSC-s.

Here, we have made some analysis between WCS1

and BSC1, BSC2, BSC3, BSC4, BSC5, BSC10,

BSC11, BSC12, BSC13 and BSC14. Tin figure 4,

it is clearly shown the real scenario where these

analysis are done.

WCS1

BSC1

BSC14

BSC13

BSC12

BSC11

BSC10

BSC5

BSC4

BSC3

BSC2

Figure 4. Scenario between WCS1 - BSC1, BSC2,

BSC3, BSC4, BSC5, BSC10, BSC11, BSC12, BSC13

and BSC14

We have analyzed the traffic load for a certain

period of 1 month, from 09/11/12 - 09/12/12. As

we can see in figure 5, the maximum loads during

peak hours are different in every BSC.

Figure 5. Result of analysis between WCS2 and BCS-s (BSC1, BSC2, BSC3, BSC4, BSC5, BSC10, BSC11, BSC12,

BSC13 and BSC14)

The maximum load during peak hours in BSC1,

BSC4, BSC5 are 25%, BSC3 is 20%, BSC2 is

40%, BSC14 is 45%, BSC12, BSC13 are 55%,

BSC10 is 62%, BSC11 is 69%. The traffic load is

not high in BSC1, BSC4, BSC5, BSC3, BSC2,

BSC14, BSC12 and BSC13. The traffic load in

BSC10 and BSC11 are high so it is in the limits of

permissible.

As we can see in figure 5, utilization of

each BSC trunks is not the same. Traffic loads in

BSC11 and BSC10 are higher than traffic loads in

BSC3, BSC1, BSC4 and BSC5. In this paper we

propose optimization of BSC trunks by distributing

the traffic load in each BSC. Load sharing between

BSCs is very important to have good quality and to

manage better network resources.

This problem can be solved by moving the BTSs

(Base Station) through BSCs which have fewer

loads. These results are shown in figure 5.

Second scenario: WCS2- BSC6, BSC7, BSC8,

BSC9 and BSC15

In this scenario, we have made some

analysis between WSC2 and BSC6, BSC7, BSC8,

BSC9 and BSC15, see figure 6.

WCS2

BSC6

BSC8

BSC7

BSC15

BSC9

Figure 6. Scenario between WCS2 - BSC6, BSC7,

BSC8, BSC9 and BSC15

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ISBN: 978-1-61804-164-7 226

We have analyzed the traffic load for a certain

period of 1 month, from 09/11/12-09/12/12. As we

can see, the maximum load during peak hours is

different in each BSC. The maximum load during

peak hours in BSC8 is 22%, BSC6, BSC7, BSC9

are 32% and BSC15 is 45%. As we can see, in

figure 7, the traffic load is not high and doesn’t

affect quality of services. This means that in this

segment of network, everything is according to

recommandations for QoS and QoE.

Figure 7. Result of analysis between WCS2 and BCS-s (BSC6, BSC7, BSC8, BSC9 and BSC15)

5 Conclusion

In this paper, first we have explained into details

the architecture of VALA network which is

implemented in PTK. Here we have explained the

role of every element that comprises the VALA

network. The main focus of this paper is in section

4, where we have shown the traffic load analysis

for a certain segments in VALA network PTK.

Since in VALA network there are two MSCs:

WCS1 and WCS2, initially we have made some

analysis in the segment between these two MSC-s.

But, knowing the fact that there are a very huge

amount of traffic between BSC-s and MSC-s, we

have also made some analysis in these segments.

These analyses between MSC- and BSC-s, we have

divided in two scenarios. In the first scenario, we

have made traffic load analysis between WCS1-

BSC1, BSC2, BSC3, BSC4, BSC5, BSC10,

BSC11, BSC12, BSC13 and BSC14. Whereas, in

the second scenario, we have made traffic load

analyses between WCS2- BSC6, BSC7, BSC8,

BSC9 and BSC15.

As we can see from figures 5 and 7, utilization of

each BSC trunks is not the same. Knowing that

load sharing between BSCs is very important to

have good quality and to manage better network

resources, in this paper we have proposed

optimization of BSC trunks by distributing the

traffic load in each BSC.

References

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ISBN 0-470-86694-2 .

[2] William C. Y. Lee, “Mobile Communications

Design Fundamentals”, 2nd edition

1993, 400 Pages, ISBN: 0471574465

[3] Gunnar Heine, Holger Sagkob, “GPRS:

Gateway to Third Generation Mobile Networks”

Artech House Publishers, ISBN: 1580531598, 2003

Recent Advances in Circuits, Communications and Signal Processing

ISBN: 978-1-61804-164-7 227