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,
[email protected], [email protected], [email protected]
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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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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ISBN: 978-1-61804-164-7 223
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.
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[3] Gunnar Heine, Holger Sagkob, “GPRS:
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Artech House Publishers, ISBN: 1580531598, 2003
Recent Advances in Circuits, Communications and Signal Processing
ISBN: 978-1-61804-164-7 227