Future Trends in Telecommunications Network Planning

1. White Paper
New Universal Evolution of Telecommunications Network Planning:
Fixed-Mobile Convergence with Application and Service
Divergence
Prof.Dr.Dipl.Ing.Mehmet Erdas
SIEMENS PSE TN MNS SA
mehmet.erdas@siemens.at
Abstract:
The unification of both packet- and circuit switched world leading to the convergence of fixed
and mobile networks together with the database planning, necessitated the concomitant
introduction of new applications and services in order to protect the previous
telecommunications investments of operators or investors, who are urgently looking for the
protection of their investments. This paper gives an overview of how to optimize the network
planning problem by maximizing benefits while minimizing the risks of the investors-
suppliers-and operators, under the light of latest developments in the area of network
planning like the self-similarity of traffic, dynamic routing and topological constraints ,
summarizing the scope and the methodology of network planning and network management.
The next generation of access, switching, and transmission networks, as well as the end-
user IT-equipment will be much more faster and intelligent, much more self-contained-and
actively self-regulating, adapting themselves through their own iterative adjustment and
decision making mechanisms to their own conditions or adaptive goal-settings. .
The New Network Planning and Network Management Teams has to act at the speed of light
or at least at the speed of thought, in order to be able to keep pace with the accelerated rate
of change of the market demand (All-IP, IPsec, DiffServ QoS),as the main driving force of the
technological innovation.The new stored program controlled complex procedures with fully
open interfaces will make the active networks soon a market reality leading to the
convergence of the fixed-and mobile networks. The All-IP (Ipv4 replaced soon by Ipv6)
convergence of different protocol stacks are to be achieved by the unification of circuit-and
packet switched technologies through queueing theory and stochastic discrete event
simulation.
The new unified network architectures enabling gigabits or terabits of throughput with
underlying topological configurations and dynamic routing policies will in themselves be
offered as a totally new revenue generating business, service or product. The world of ISPs
or ASPs will be too complicated facing the question of survival against rapidly changing
challenging market conditions. The Operators –Suppliers-and Investors of future
telecommunications products or services will definitely need the network as an intelligent
unique product in itself offered by the Network Planners or Consultants, because ISPs /ASPs
are just about to loose their own control, or having to outsource , at least losing soon their
degrees of freedom and/or competence in decision making to the network planners of the
universally converged, but with services and applications totally diverged next generation
networks.
Mehmet Erdas page 1

2. Introduction:
Network Planning Problem means in the broadest sense how to meet the customer,
business and infrastructure specific conflicting competitive objectives under efficient
resource-and capacity utilization constraints over time.
The term „network planning“ has a broad scope of coverage, implying fundamentally both the
strategical -and the operational network planning processes, which can be summarized as
the radio network planning process tuned to the fixed-and mobile network planning
processes , short-medium-and long-term resource allocation problem , capacity assignment
and routing problem together with the integrated network data base planning,considering the
network evolution, network compatibility and the integration of OEM-products into existing
networks, network planning standardization, security and diffserv capability of a variety of
middleware applications developed independently of underlying network structures, but as a
feedback influence increasing the complexity of network traffic load, assuming a unified
future network described by ist network database. The treatment of telecommunications
network economics against the network availibility,network redundancy (availibility of
redundant paths meeting overload and burstiness in peak hours ), network security and
network database back-up and recovery concepts should be the main emphasis of an
integrated network planning. Shortly defined, the integrated network planning process covers
the orderly , time-dependent efficient deployment and management of computer-and data
communications facilities. The new service product Network Planning is used in both the
operational ( referring to existing telecommunication networks) and the strategical
sense( identifying future technology trends driven by market forces ).The evolutionary
network planning aims at the overall technological-economical-and financial integration of
new network components features and technologies into existing networks.
For the development of network planning and integration tools, the well-known classical
O.R. algorithms of advanced.dynamic integer.programming and graph theory, queueing
theory and combinatorial optimization, branch and bound methods, penalty methods, and
Discrete Event Simulation.are the most commonly used network planning and optimization
algorithms..(1),(2),(3),.(14)
The Network planning problem has to be understood as an optimization problem, stated
under the optimization criteria of cost effectiveness, high reliability- availibility-flexibility,
extendability of networks and network components to minimize the overall network costs
(reduce equipment) with a modular subnetworks structure. The general planning factors to
be considered are mainly the technological factors, economical factors, financial factors,
business factors, organizational factors,and environmental factors. Depending upon the level
of planning detail required , for the definition of the network components, network modules
(HW-and SW), various system and network architectures, network services, network
topology ,different routing strategies specified according to the underlying network topology
can be used. Finally based on the assumed traffic load sharing and traffic channelizing
mode, quite different problem formulations of network planning problem can be presented.
The most important network features can be counted as the statistical multiplexing of loads,
the existence of a large number of heterogenous subnetworks, their modular interconnection,
and value-added services, the future growth prospects of existing networks The end –to –
end delay, cell or packet loss, blocking probabilities and the calculation of the link budgets
and protocol overheads which are to be taken into account together with the quality of
service parameters. The Bandwidth availibility on demand is another bottleneck, that has to
be considered in the formulation of network planning-and optimization problem.The
economies of scale, finiteness of resources, standardisation and growth prospects of new
technologies, modular extendability, hardware and software variety and emergence of new
solutions should also considered as objective variables or constraints in the formulation of
heterogenous networks` planning problem.
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3. The evolution of networks over time is a key aspect of network planning and network
optimization.The new network engineering requests may come due to a new product or
technology or new customer (market-driven or technology-driven) expectations. The
definition of new services, business priorities, reuse of existing infrastructure in migration are
important to identify the network design strategy.
The optimized routing, colocation of network elements are the other factors influencing the
cost-revenue-profit picture.
Aggregation and/or Decomposition into smaller Problems:
Methodologically,the network planning and optimization problem has to be divided into a
number of smaller, easily manageable subproblems. One set of subproblems might be
defined relying on the existing network structure, network topology, the priority rules for
services in proportion to their shares in revenues, and the routing strategy. Another set of
subproblems might be defined as end-user terminal equipment design (intelligence of end-
user equipment), access technologies design, the assessment of switching technologies and
finally the transmission systems.(5) The Markov Chains, queueing theory, general birth-death
processes and renewal theory can be used to unify the totally different world of circuit
switching and packet switching. The Erlang-k distribution and priority queueing models as M/
G/m queues can be used efficiently to simulate the traffic load as Poisson distributed
interarrival times and service times; defining their ratio as the utilization factor. (6),(8).(9)
Applications such as video and voice telephony are delay sensitive and will require
differentiated services (QoS) with prioritization introduced into the queueing models.Analysis
of the accuracy of bursty traffic models together with the response and recovery times and
load sharing/load balancing in case of overload are an essential part of performance analysis
of telecommunication networks Traffic models should match closely to real data in order to
obtain reasonable tracking of the critical network performance bottlenecks..
Generically, one could optimize the cost-revenue-profit triple by minimizing the cost of
expenditures for equipment and operations, and maximize revenues by introducing value-
added intelligent services through intelligent networking (add a separate control layer to
achieve service,network and end-user equipment independence) and doing all this over time
as technology, user requirements and the economic factors change. The decomposition of
network planning problem into smaller optimization problems has to be done for the sake of
simplicity, consistence, uniqueness and solvability.
There are various types of classification approaches for different types of network planning,
such as fixed and radio network planning, administrative planning, fundamental technical
planning to develop plans for network management, switching and routing, addressing,
signalling, operations, provisioning and maintenance. Engineering plans are detailed and
immediate plans. Another type of planning can be accomplished on the basis of network
components selection, like the number of base stations, local exchanges, toll exchanges,
interexchange transmission, loop plant, signalling network and customer premises
equipment, LAN, WAN,MAN, Routers, Bridges, Gateways etc. For GSM/GPRS/EDGE/UMTS
network planning, the main classification is usually the radio network planning and fixed
network planning besides of course the packet switching and the circuit switching. According
to different services, another classification could be made as POTS, ISDN, SMDS or FR
services, Packet, Video, Cellular Telephone, E-Mail, Remote Login, File Transfer, Image
Transfer, Voice Connections, World Wide Web.
According to timing or time coverage of plans, the long-term plans(5-20 years), medium-term
plans (2-5 years), and short-term plans (1-2 years) could be done using iterative dynamic
programming or simulation scenario techniques by changing the planning assumptions. ( 7)
Mehmet Erdas page 3

4. Performance Evaluation of High Speed Packet Switching Networks
The Packet-switching network was developed during the 1960s.The idea behind a packet-
switching network was to create a network of dedicated leased lines whose sole function
would be to transport digital data traffic. At the source, data would be divided into groups of
bits called packets. An actual packet has two parts: Header and the actual information field
or payload. The System Performance measures in a packet switched network are the
interarrival times, service times, queue length, transit time, waiting time, and server idle time.
(2)
The Header contains information about the originating point, packet`s destination, its priority
and its error codes. The payload is the group of information bits that has to be transported
over the network.algorithms running in the switching nodes read a packet`s destination
address and forward the packet over the next successive link on its way to its destination.
The great advantage of statistical multiplexing in packet switching technology , that is sharing
of transmission lines by the bursty data traffic between many users,lowered the cost of
transmitting data over leased lines and combined the inherent bursty data traffic into
aggregate flows that could be accommodated economically by long lasting leased-line
connections. Today packet-switching is used overall in general user networks such as
Internet as well as in specialized applications such as in establishing the connections in
telephone networks through the Common Channel Signalling System 7.
With the introduction of ATM (Asynchronous Transfer Mode) technology, the share of packet-
switching in the total world communications bandwith increased drastically. ATM combined
broadband(high-speed) communications and services of voice- data-and video traffic in an
integrated manner (ISDN). Some important advantages of ATM technology against
STM(Synchronous Transfer Mode):
No rigidly structured hierarchy anymore needed
No time slot assignment (Mapping) problem anymore
No need for separate switches at each data rate by multirate switching as a combination of
64kbps switching building blocks.Bursty data traffic and services instead of fixed-demand
services possible
During Network Planning the individual network components are to be planned and
integrated into the existing GSM network and Internet. This covers the interconnecting of
network equipment according to the network planning, configuration of system parameters
for each network component, customer specific setup of the network management system
tests with real applications and real traffic simulations.
The scope of overall end-to-end network planning problem should be divided into smaller
subnetwork planning problems as the
-Radio Network Planning(RNP)
-Fixed network Planning ( PSTN,B- ISDN..)
-Mobile Network Planning (GSM/GPRS/EDGE/UMTS)
-Database Planning (Backup-and Recovery (14)
Planning a High Quality, High Performance Network Architecture
The right network architecture should be tailored depending upon the relative market choices
of companies; even within a single market the architecture and technology are to be
considered as moving targets, under which we should look for optimum network
solutions(maximizing benefits while minimizing risks). Mobile operators are building networks
only for their own use, without any real traffic simulations. The large variety of subnetworks
and services necessitates a dedicated and specialized planning. The diversity of hardware
and software complicates network management and planning. Therefore the choice of HW
Mehmet Erdas page 4

5. and SW and the rapid growth in networks makes it compulsory to install higher capacity
systems accompanied by proper network planning.
Mathematical Programming for Network Planning
An objective function and associated set of constraints is called a mathematical program,
consisting of decision variables and surplus or slack variables to convert the constraint
inequalities into equations which are then to be solved by matrix operations of inversion and
multiplication. The set of all constraints determines the feasible solution space. The Objective
function might be cost, performance or reliability metrics. Network planning problem
formulated as a mathematical programming, might have a single unique globally optimal
solution or many locally optimal solutions. A locally optimal solution is only optimal for a
limited portion of the feasible solution space. Sometimes heuristic algorithms, which use
intuitive procedures to find out optimal solutions, might be useful to achieve global optimal
solutions starting with local optimal solutions. The canonical problem formulation for network
planning and queueing theory used to formulate the telecommunications network design and
the solution technique , called simplex algorithm, can be found in Ref.(1).p.14-41.
The Network Optimization is indispensable because of shifts in subscriber-and application
distribution and their traffic behaviour, changes in the subscriber mobility profile, subscriber
growth, unbalanced market-driven regional network growth and limitations of frequency
resources on air-interface.
Routing Problem and Discrete Event Simulation
ISPs or ASPs face a challenge in provisioning of network resources because of the rapid
growth of bursty internet traffic and wide fluctuations of the traffic patterns. The dynamic
routing should be used to prevent congestions and application performance as a valuable
traffic engineering tool. The deployment of load-sensitive routing is however difficult due to
overheads imposed by link-state update propagation, path selection and signalling. Through
simulation experiments of one week or one-month duration, packet flows could be traced to
differentiate between long-lived and short-lived flows to improve the performance of the
links and to achieve the routing stability. The existing routing protocols OSPF, BGP, RIP etc.
are optimizing in one way, leaving the longer paths underutilized.
A middle approach between physical experimentation and statistical analysis which is often
used, is simulation technique. Since simulations are performed with software , it is easy to
change or test the model assumptions, or change requests. The usual type of simulation of a
network is called discrete event simulation. The”discrete events” are occurrences such as
packets being transmitted , a buffer receiving a packet, or a call being switched. Simulations
can be run to trace transient behaviour of networks,which occur over a very short period of
time as a result of some event. The behaviour of networks over long time periods and the
self-similarity of internet traffic, that means the steady-state behaviour of networks could be
observed and simulated to examine various planning assumptions, whether they represent
the reality.of traffic as it is. Discrete event simulation is stochastic in nature, because basic
inputs like packet arrivals and call placements are to be generated randomly by using
pseudorandom number generators.as software products.(3)
The self-similar traffic modelling is going to replace the poisson modelling of network traffic,
because of long-range dependence in wide-area networks. The simplest models with long-
range dependence are self-similar processes, which are characterized by hyperbolically –
decaying autocorrelation functions. The long-range dependence of self-similar processes can
be charactereized by a single parameter, called the Hurst parameter., which can be
estimated using Whittle`s procedure (11)
Mehmet Erdas page 5

6. Transient queueing analysis is essential for network planners to understand the temporal
behaviour of their networks. The sojourn time performance of a network node has to be
studied under realistic traffic environment. For that purpose , a network node has to be
modeled as a finite quasi-birth-death process(instead of simplest M/M/1queueing model) with
level dependent transitions, which are used to model a controlled or prioritized queueing
system, where both the arrival and the service processes are to be regulated based on the
instantenous buffer occupancy level, because the size of the buffer is always finite in
reality.and the arriving cells are lost when the buffer is full. This approach allows the
incorporation of more sophisticated and accurate traffic models than the previous 2/3 State
Markov Models.of network traffic. The impact of input traffic characteristics and the effect of
various simplifying assumptions like infinite buffer approximations, the effect of statistical
multiplexing and the controlling effect of preemptive cell discarding (to assure the QoS) on
the sojourn time behaviour of the system has to be studied further in depth.to explain the
nodal congestion in networks planning. Realistic networks of today have large buffer size, but
complex and bursty input traffic makes the infinite buffer assumption invalid. Buffering
together with the statistical multiplexing can be used to increase the redundancy, reliability
and availibility of networks to avoid congestions and to provide the QoS parameters in case
of overload or highly bursty traffic input with long duration.(12, 13)
Trends in Network Planning:
For Transmission capacity services: TDM SONET/SDH WDM/DWDM-First step to the future
–optical switching at 10-100 Terabits/sec.
For Access Networks services: TDM CATV,DSL,802.11,LMDS Wireless-Mobile-IP
Convergence of fixed-and mob.IP,100Mbit Ethernet is the right next step,but fiber optics is
the future transmission medium in telecommunications.
For Fixed Voice Networks services: CS VoIP using H.323 Replace with SIP and MGCP
Session Initiation and Mediagateway Protocol
For Mobile Voice and Data Networks :.VoGSM SMS WAP GPRS EDGE UMTS or 802.11 IP-
based new Value-Added Services, like IP-based Intelligent networking and new middleware
applications development just by separating the control plane and data plane.
New IP-Services Best Effort DiffServQoS IPsec.for VPN Security WDM-Switching replacing
ATM ; as a moving target between assured delay and assured bandwith use MPLS for traffic
engineering, just putting the bandwidth where the traffic is or putting the traffic where
bandwidth is.
Overall Trends and Conclusions: Fiber is the only future proof foundation for all network
services; SIP and MGCP will be the key to voice/data convergence; mobile phone operators
will become wireless Internet access providers and last but not least: Internet is able to
provide QoS and Security without Layer2 VCs. With the realization of UMTS, the cellular
networks of the future might well be dimensioned for the dominant type of traffic which is
expected to be mobile data, rather than voice. This would lead to network consolidation of IP,
ATM and Frame Relay.through network consolidating layers enabling cost savings in
infrastructure.
FMC: Fixed-Mobile Convergence:
The heterogenous networks evolution and the mobility of Internet requires a unique OAM
Concept for common billing, operation and maintenance of diversified network services.
FMC can be realized by establishing a combined switching centre enabling the service and
support of both the mobile and the fixed customers through the same exchange. This might
be a hardware or software solution or a combination of both depending upon the existing
network infrastructure. Global access to personalized services are independent of access
methodology, underlying network and delivery method. It should be mentioned that the
access
network is not so expensive to build out and to upgrade. Convergence will first happen in
enterprise networks when voice is moved from traditional voice VPN (PABX networks) to
data-VPN and thereafter into long distance IP-based intelligent VPNs. In the medium-term,
Mehmet Erdas page 6

7. the emerging technologies and standards will facilitate service and network convergence to
an IP based network with fixed and mobile access increasing complexity with ever growing
data throughput rates, bandwidth allocation and network configuration management
problems. The optimization criteria for such a converged network can be counted as the end-
to-end targeted quality of service levels, throughput rates, link capacity utilization, the
minimized overall cost and delay levels with differentiated security allocations for different
applications and the interoperability or compatibility of hardware and software units without
posing any difficulties for combined implementation.
Conclusion:
Modified overall network optimization problem formulation for a unified network planning
process
The overall planning problem for such a converged network could be be formulated as the
minimization of end-to-end total line costs (call set up, volume-and time dependant charging
accounting for the cross-product of total connection time and volume of data transferred end-
to-end packet-and circuit switched connections), subject to a given traffic load sharing
model, given the chosen coding schemes for radio network coverage, given the specified
node locations, inter-node and intra-node peak circuit- switched -and packet- switched traffic
load sharing mechanisms, adjusted or matched by general birth-date stochastic queueing
models delivering the required minimum link budgets and buffer sizes for smoothing out the
burstiness of packet data traffic, over the decision variables of underlying network topology
and routing policy, yielding the total channel or link capacities adapted by channel allocation
choices (channelized, unchannelized, fractional, setting DE for FR or CLP for ATM or
labeling for ATM LSR ) relying on the DiffServ or prioritized QoS-using static,virtual, dynamic
routing mechanisms, without leaving any longer paths underutilized, if congestion in the
shortest paths occurs), satisfying the allowed overall access-switching-transmission end-user
equipment delays, reliability-redundancy-and availibility constraints, all being discrete(non-
continuous) and iterated .over time covering the network planning period. The outputs of
such a planning model will be measured or scaled in multiple functional HW-or SW units,
bits -and seconds, which are to be converted into monetary units using a market-driven
sales, qualified cost- and pricing strategy allowing for the investment protection of investors-
suppliers-and operators triple defined as survival value chain, such that none of the market-
players will be threatened in survival.
This overall problem formulation for the optimization of combined radio-and fixed network
planning process could be extended for incorporating the involved database planning,
database security, back-up and recovery processes.
References:
1-Thomas G. Robertazzi:Planning Telecommunication Networks , 1999, IEEE
Communications Society, Ch.1-2-3 pp 2-36
2-Susan L. Solomon Simulation of Waiting Line Systems, 1983 Prentice Hall, pp 11-16
3-Jerry Banks,John S.Carson II, Barry L.Nelson :Discrete-Event System Simulation, 1999
Prentice –Hall
pp 92-96
Mehmet Erdas page 7

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