A multi-service dimensioning methodology is
essential in order to propose a cost-effective
H. Ramzi radio access network solution to operators.
UMTS radio access network dimensioning
Introduction Among the various elements of a UMTS network, the
Radio Access Network (RAN) is a major part of the oper-
In recent months, the mobile telecom world has moved for- ator’s investment (see Figure 1). Hence one of the key
ward into the “UMTS era”. Governments have identified issues for the operator’s partner (supplier) is to propose
the number of Universal Mobile Telecommunications a cost-effective RAN solution.
System (UMTS) licenses to be awarded and have defined This article highlights how UMTS differs from the Global Sys-
the associated legal framework. Standardization bodies are tem for Mobile Communication (GSM) and the main steps
fine-tuning the latest versions of the standards. Regula- involved in dimensioning a UMTS radio access network.
tors are setting up UMTS license award processes (beauty
contests, auctions or a mix of the two). Operators are set-
ting up critical size consortia through acquisitions or What is Different about UMTS?
alliances to compete for UMTS licenses. Content providers
are building up and enhancing their mobile services and UMTS uses different technologies than GSM, and this
applications portfolios. Investors are carefully analyzing directly affects dimensioning of the UMTS RAN. The main
the UMTS value chain and its associated business plans. differences are:
Suppliers are optimizing their solutions (time to market,
technical features, commercial issues, etc). The press is • New multiple access technique: Wideband Code Divi-
speaking highly about the capabilities of UMTS, and hence sion Multiple Access (WCDMA).
kindling user interest in UMTS. • Multi-service traffic environment.
Operators that already own a UMTS license or are can- • Asynchronous Transfer Mode (ATM) transport in the
didates for one are now looking for reliable business part- RAN (UMTS Release ’99).
ners that can provide end-to-end UMTS solutions
(i.e. user terminals, radio access network, core and New Multiple Access Technique
backbone networks, service integrator capabilities and One of the key aspects in cellular networks is the multi-
content provider capabilities). ple access technique adopted on the air interface
between the user equipment and the
Node B. The chosen technique must
Fig. 1 UMTS radio access network optimally divide the available radio
spectrum (MHz) into a number of
channels and define how these chan-
nels are allocated to the many users
Radio Access ISDN (subscribers) accessing the network.
WCDMA has been chosen for the air
interface to meet the constraints of the
No Iu-b UMTS radio interface: variable bit
rates, variable Quality of Service
B (QoS), etc.
B To illustrate this technique, one can
imagine a “cocktail party”. Picture a
large room with a number of partygoers
B Iu who would like to simultaneously
hold a conversation with a “super
translator” in the middle of the room.
Alcatel Telecommunications Review - 1 st Quarter 2001 55 UMTS radio access network dimensioning
Fig. 2 Cocktail party As the number of partygoers increases further, partygoers
must move closer to the translator to be heard, or must speak
more loudly. As a result, partygoers at the edges of the room
are no longer served by the cell. However, if partygoers start
to speak more loudly, the noise continues to increase. Thus
a stringent discipline needs to be implemented within the
Tra Supe room to resolve this problem. The translator (Node B) solves
r the noise problem by requesting that each individual
speaks loudly enough to be heard, but no louder. Thus power
control is needed to operate a WCDMA system.
As the useful signal is conveyed over a wide frequency band
(5 MHz), two multipaths can be “easily” distinguished and
combined by the receivers (inherent frequency diversity of
WCDMA). This is carried out by a Rake receiver. As two adja-
cent cells can use the same carrier, one user equipment can
be connected simultaneously to two Node Bs to benefit from
two-path diversity. WCDMA thus supports soft handover.
Each partygoer is carrying on a conversation in his or her
own unique language with the super translator (see Fig-
ure 2). The room corresponds to the coverage area of one Tab. 1 Main characteristics of WCDMA affecting the design
cell; the partygoers correspond to user equipment in the • WCDMA is a noise limited system
cell; the translator corresponds to the Node B; and each • Coverage depends on the amount of traffic in the cell
language corresponds to a given code. • No frequency planning is needed (users are differentiated by codes)
Each person sees the other conversations as noise, which
• Path diversity (known as “macrodiversity”) thanks to soft handover.
should do no more than cause a slight rise in the “noise
floor” or interference level. This is done by “spreading” the
transmitted signals using a direct spreading techniques, Hence, a specific WCDMA power budget is needed.
such as WDCMA.
As more partygoers (user equipment) enter the room Different Traffic and QoS Constraints: Multi-service
(cell), the room gets noisier. The translator (Node B) hears Environment
more noise and so do the other partygoers. Ultimately, the UMTS will give subscribers access to a great variety of
noise level increases to the extent that it interferes with services and applications, which can be grouped into
conversations. Hence, the system capacity (simultaneous three main categories: always-on applications, media
number of users) is limited by the level of noise in the room applications and M-commerce applications, as shown in
(cell). Consequently, WCDMA is a noise-limited technique. Figure 3.
Fig. 3 Typical UMTS user services
Always-on Media Fun
• Games (Hangman, Poker, Quiz, …)
Directories • Screen Saver
• Yellow/White Pages • Ring Tone
• International Directories • Horoscope
Mobile Office • Operator Services • Biorhythm
• Agenda Music
• IntraNet/InterNet • Downloading of music
• Corporate Applications files or video clips
• Database Access
• Flight/train Schedule (general/specific) Location services
• Reservation • International/National News • Traffic Conditions
• Local News • Itineraries
• Sport News • Nearest Restaurant, Cinema, Chemist,
• Weather Parking;, ATM ...
• Lottery Results
Vertical application • Finance News
• Traffic Management • Stock Quotes
• Automation • Exchange Rates
• Mobile Branches M-commerce
Non physical Physical
• On-line Banking On-line Shopping
• Ticketing On-line Food
• Best Price
Alcatel Telecommunications Review - 1 st Quarter 2001 56 UMTS radio access network dimensioning
Each service requests a minimum bit rate Fig. 4 RAN dimensioning
to provide the quality of service that the
user (human or machine) expects. How- INPUTS : OUTPUTS :
ever, these services are conveyed over the Regulators/Operators A Radio Access Network solution, i.e.:
requirements in terms of : R.A.N • Node B : Number and configuration
RAN onto a standard set of bearer services. • Coverage, • RNC : Number and configuration
A typical set of bit rates (to be provided by • Traffic,
Design • Transmission Links capacities : Mbit/s
• QoS • Architecture : Topology
FDD/WCDMA) is as follows:
• Adaptive MultiRate (AMR) speech
(4.75 to 12.2 kbit/s) ➜ circuit-switched
ALCATEL PRODUCTS PORTFOLIO :
12.2 kbit/s. • Evolium™ products range
• Real-time 64 kbit/s (circuit-switched) ➜ • Litespan products range
• DSLAM products range
Non-real-time 64 kbit/s (packet • Broadband Wireless Access solutions
switched). • Optinex™ products range
• Real-time 128 kbit/s and real-time
144 kbit/s (circuit-switched) ➜ Non-real-
time 144 kbit/s (packet-switched).
• Real-time 384 kbit/s (circuit-switched)
➜ Non-real-time 384 kbit/s (packet switched). UMTS RAN Dimensioning: Methodology
Throughput is not the only criterion on which the user bases The aims of radio access network dimensioning are to:
his or her opinion of quality of the delivered service. Max-
imum delay and data error rates (Bit Error Ratio, Block • Estimate the number and configuration of the various
Error Rate, Frame Erasure Rate) are also critical param- network elements required to provide a mobile service
eters. Hence, services are also classified into: in a given region (at national or regional level), with roll-
out spread over several phases (e.g. 5 years).
• Conversational: very delay-sensitive, symmetric. • Propose a RAN topology.
• Streaming: delay sensitive, very asymmetric.
• Interactive: round-trip-delay sensitive, asymmetric. A combination of these two aspects should lead to a cost-
• Background: most delay-insensitive, asymmetric. effective solution, as shown in Figure 4.
Tab. 2 Main characteristics of the multi-service environment Inputs
For each phase of the roll-out plan, three types of input
• A set of bit rates: AMR (4.75 to 12.2 kbit/s); 64 kbit/s, 144 kbit/s, 384 kbit/s.
data are required:
• Circuit-switched and packet-switched.
• Asymmetry between the uplink and downlink bit rates. Coverage
• Variable QoS: mean throughput, maximum throughput, blocking probability, • Regions to be covered (e.g. areas with more than
500 000 inhabitants).
• Partitioning of the region into subareas (e.g. business,
Hence, a multi-service traffic model is needed. residential).
• Identification of the class of each subarea (e.g. dense
Different Transport Technology: ATM Transport (Release 99) urban, urban, suburban, rural). This directly translates
As a consequence of the multi-service environment, the links into propagation conditions.
between network elements have to be multi-service “pipes”,
supporting variable bit rates and able to support variable QoS. Traffic
Release 99 of the UMTS standards assumes that ATM trans- • Spectrum availability (e.g. 3 x 15 MHz).
port is used for the radio access network. Hence, one has • Subscriber density per subarea (e.g. 500 subscribers
to consider the overheads inherent to ATM when evaluating per km2).
the link capacity over the Iu-b, Iu-r, Iu-cs and Iu-ps inter- • Subscriber profile.
faces. One must also consider the inherent Virtual Cir-
cuit/Virtual Path (VC/VP) grooming capabilities of an ATM Quality of Service
transport network when designing the transmission net- • Coverage probability (e.g. 95% probability of the
work topology. strength of the signal received within the cell being
It should be noted that Iu-r is a new interface which did not above a given threshold).
exist in GSM. This interface allows soft handover between • Blocking probability, maximum delay, minimum
two “adjacent” Node Bs managed by two different Radio throughput.
Network Controllers (RNC), as shown in Figure 1. • Service level per subarea (e.g. deep indoor coverage for
a dense urban subarea, that is, a mobile service can be
Tab. 3 Main characteristics of ATM transport technology provided even in a meeting room without windows).
• Inherent overheads
• VC/VP grooming capabilities
Once all the above information has been assembled for a
given phase and a given subarea, the process of deriving
Hence, a new RAN architecture is needed. the number and configuration of the various network ele-
Alcatel Telecommunications Review - 1 st Quarter 2001 57 UMTS radio access network dimensioning
ments can commence using the proce- Fig. 5 Node B dimensioning process
dure outlined below.
Node B dimensioning
The aim of Node B dimensioning is to
• cell range; Required number
• number of carriers per sector; channels WCDMA Cell range
• required common baseband capacity. Analysis Link Budget
Number of count
Coverage and capacity are closely linked per sector
when using WCDMA. Hence, the Node B
dimensioning process should deal simul-
taneously with both the coverage and
capacity, as well as taking into account
the multi-service traffic mix. Figure 5 Iterative process until convergence
shows the principle of the Node B
dimensioning process, which is applied
independently to the uplink (user equip-
ment to Node B) and to the downlink (Node B to user • Step 5 bis: A propagation model (e.g. Okumura-Hata
equipment). or Walfish-Ikegami) is applied which reflects the con-
The analysis for the uplink comprises the following steps: straints of the subarea in order to calculate the cell
range. In turn, this is used to derive the site area cov-
• Step 1: Assume a typical cell range R0, which gives the ered by a Node B taking into account the QoS con-
cell area. straints, which then leads to the calculated cell
• Step 2: Estimate the average traffic captured within the range and thus the cell area.
cell area based on the traffic inputs. • Step 6: Continue the iteration until the calculated cell
• Step 3: Derive the number of simultaneous channels range equals the assumed cell range.
(codes) required to convey the peak traffic per service, • Step 7: Check that the cell load (i.e. noise rise) is below
which leads to the number of channels required to sup- a certain level. If not, add a new carrier to split the
port the peak mix of traffic. Figure 6 illustrates the traffic.
• Step 4: A statistical approach is then used to calculate The analysis for the downlink comprises the following
the aggregate rise in noise generated by this traffic mix. steps:
• Step 5: The aggregate noise rise is fed into the multi-ser-
vice power budget, which is used to determine the Max- • Step 1: Assume a typical cell range, and thus the cell
imum Allowable Path Loss (MAPL) or attenuation. The area.
power budget takes into account the performance of the • Step 2: Based on traffic inputs, identify the average
products involved (e.g. transmitted power, feeder losses, traffic captured within this cell area.
antenna gain, sensitivity) and degradation of the radio path • Step 3: Determine the required number of simulta-
(propagation attenuation, shadowing effects, multipath neous channels (codes) needed to convey the peak traf-
effects) when calculating the MAPL, as shown in Figure 7. fic for each service.
Fig. 6 Required number of simultaneous channels
Air interface "pipe" Peak Traffic = worst case
conferencing Average traffic
Voice, SMS Number
Shopping on line of radio
Web browsing resources
Alcatel Telecommunications Review - 1 st Quarter 2001 58 UMTS radio access network dimensioning
• Step 4: Calculate the mean power Fig. 7 Power budget
required for one user of each service.
• Step 5: Based on a knowledge of Antenna Gain
the uniform distribution of user Radio Path Degradation :
Attenuation, shadowing, Multipath
equipment over the cell area (with
or without soft handover), use a
statistical approach to determine
the aggregate Node B transmit
power corresponding to the traf- Feeder Losses
fic mix. BS
• Step 6: The aggregate Node B trans-
mit power is fed into the multi-service
power budget, which is used to
determine the MAPL and hence the
• Step 7: The iteration is continued
until the assumed cell range leads to
the maximum transmit power of the
Having calculated the cell ranges for
both the uplink and downlink, the
most limiting link is selected. The analysis for the non- uplink and the transmitted power on the downlink.
limiting link (uplink or downlink) is then repeated, tak- • Consistent multi-service power budget analysis.
ing into account the selected cell range (i.e. decrease user • No a priori assumptions are made about the limiting
equipment transmit power or decrease the Node B link (uplink or downlink), neither for coverage nor for
transmit power). capacity.
In summary, The Node B dimensioning methodology • One absolute cell range for all services, ensuring con-
developed by Alcatel involves: tinuous coverage for all services.
• Consistent multi-service traffic analysis. Figure 8 shows some screenshots from the Alcatel
• Statistical approach to determine the noise rise on the UMTS radio dimensioning tool.
Fig. 8 Screenshots taken from the Alcatel UMTS radio dimensioning tool
Alcatel Telecommunications Review - 1 st Quarter 2001 59 UMTS radio access network dimensioning
Fig. 9 Screenshots of radio network planning tool
Database Coverage prediction
Traffic map Pilot coverage Soft handover areas
Radio network planning study management limitation constraint, it is possible to cal-
Having dimensioned the Node B, the next stage is to carry culate the minimum number of RNCs required to han-
out a Radio Network Planning (RNP) study. This requires dle the Node Bs (number of Node Bs ÷ maximum num-
accurate data (RNP databases) related to the area being ber of Node Bs per RNC). This is designated NR1.
studied, including such information as topography and • Step 2: From the average traffic assumptions provided
morpho-class (urban, suburban, rural, etc). RNP studies as input and from the traffic limitation constraint, one
are generally focused on key target areas (“hot spots”) can determine the minimum number of RNCs required
and are carried out before site search or site acquisition. to handle the average traffic (NR2av).
Both new sites and existing GSM sites can be considered. • Step 3: Knowing the average traffic per RNC, it is pos-
These studies are carried out using a specialized RNP tool. sible to calculate the peak traffic to be handled per
It should be mentioned that in GSM, RNP studies were RNC (statistical distribution function). It is important
mainly focused on predicting the coverage area. How- to check that the traffic capacity of the RNC being
ever, in the case of UMTS, the RNP studies consider not considered is sufficient to carry this peak traffic. If
only the coverage, but also noise rise analysis, capac- not, N R2av is increased, or a larger configuration is
ity planning, soft handover areas, etc, as shown in Fig- considered, and a new peak traffic per RNC is cal-
ure 9. culated.
• Step 4: Number of required RNCs is NR; the greater of
RNC Dimensioning NR1 and NR2peak is selected.
Dimensioning of the RNC is largely conditioned by its • Step 5: Knowing the peak user traffic per RNC, it is pos-
characteristics. The ones affecting the dimensioning sible to calculate the incoming aggregate traffic on the
process are: Iu-b interface (number of STM-1s) as well as the aggre-
gate outgoing traffic on the Iu-cs, Iu-ps and Iu-r inter-
• Traffic limitations, that is, the maximum throughput per faces (cf. next paragraph). Hence, a final check is made
RNC: on the connectivity limitation constraint.
- maximum circuit-switched throughput (Erlangs);
- maximum packet-switched throughput (Mbit/s).
• Management limitations, that is, the maximum number
of Node Bs managed by an RNC. Fig. 10 Iu-b dimensioning
• Connectivity limitations, that is, the maximum number
of connections towards the Iu-b, Iu and Iu-r interfaces. ATM O&M
Calculated by means of Overheads Traffic
an analytical approach Factor
The traffic limit for a given RNC is a tradeoff between the
circuit-switched throughput and packet-switched
throughput. Average Peak Total
Traffic Traffic Throughput
Dimensioning the RNC comprises the following five
Soft 30% Signaling
• Step 1: Node B dimensioning determines the total Handover Factor
number of Node Bs for the target area. Based on the
Alcatel Telecommunications Review - 1 st Quarter 2001 60 UMTS radio access network dimensioning
Fig. 11 Iu-cs and Iu-ps dimensioning dimensioning. The total capacity required for the Iu-r inter-
face is a proportion of the total Iu user traffic.
The purpose of “Architecture” is to propose an overall
topology for the radio access network, that is, to identify
RNC CS & PS Total RNC locations, to define the type of interconnection
Dimensioning Peak I u-cs and I u-ps
Traffic Throughput between the Node Bs and the RNC (daisy chain, star,
ring), and, if necessary, to identify transmission nodes.
Signaling Here we look at several possible RAN transmission solu-
Factor tions which take into account UMTS traffic from the
Node Bs and GSM traffic from the Base Transceiver Sta-
tion (BTS). Node Bs generate ATM cells that are mapped
Interface Dimensioning Fig. 12 Multiplexing of GSM and UMTS traffic within an SDH node
The Iu-b interface is dimensioned by
calculating the capacity of the “pipe” No
coming from the Node B. This pipe B de
• Peak user traffic (aggregated), B
including soft handover traffic.
• Overheads for ATM/ATM Adaptation RN
Layer (AAL), signaling and Opera-
Tr Ba ra
tions and Maintenance (O&M). No
an ck di
B sm bo o S
is ne DH
There are two steps in this process: on )
• Step 1: Alcatel has developed an ana- BTS
lytical approach to determine the
aggregate peak traffic at Node B
level. This approach requires the fol-
lowing parameters as inputs: number C
of users of service i (active or not);
channel bit rate for service i; session
inter-arrival rate for service i; session
length for service i; activity factor for
service i; and percentage of users in
soft handover. Fig. 13 ATM concentration of GSM and UMTS traffic
• Step 2: The ATM/AAL, signaling and
O&M overheads are then added to the
peak traffic calculated in Step 1 (see
Figure 10). de
Iu-cs and Iu-ps
de de de
The dimensioning process for Iu-cs and No
B No No
B B S
Iu-ps calculates the peak user through- BT
put for both the circuit-switched and
packet-switched streams. Hence, the C
total throughputs for both these streams
(i.e. Iu-cs and Iu-ps) can be determined No
tic Back smis
by adding the ATM/AAL, signaling and /ra bo sio
dio ne n
O&M overheads (see Figure 11). SD
The Iu-r interface carries the traffic
generated by users in soft handover
between two Node Bs managed by dif-
ferent RNCs. Iu-r user traffic is a portion
of the Iu-b user traffic. Margins for
ATM/AAL overheads and signaling have
to be taken into account, as for Iu
Alcatel Telecommunications Review - 1 st Quarter 2001 61 UMTS radio access network dimensioning
onto Plesiochronous Digital Hierarchy Fig. 14 UMTS is ATM concentrated, while GSM is SDH multiplexed
(PDH) or Synchronous Digital Hier-
archy (SDH) frames, whereas voice
traffic generated by the BTS are No
mapped onto channeled E1 (PDH). No
de de de
Case 1 No
B No No
Both GSM and UMTS traffic are mul- S
tiplexed within an SDH node. ATM RN
traffic generated by the Node Bs is C
conveyed over PDH or SDH and mul- de Tra
No (op n
tiplexed together with GSM traffic B tic Back smis
/ra bo sio
coming from BTS within an SDH node dio ne n
(e.g. Add/Drop Multiplexer; ADM). H)
The aggregate streams (SDH VCs) are S
transparently conveyed over the SDH
transmission backbone (see
This architecture is recommended if
SDH nodes already exist in the net-
work at the Point Of Concentration
(POC), and if overall UMTS traffic at
this point is quite low (< 30 x E1) and
does not require any ATM concentra-
Fig. 14b UMTS is ATM concentrated while GSM is SDH multiplexed (optimized)
Both GSM and UMTS traffic are de
aggregated within an ATM switch. No
GSM traffic, adapted in AAL-1 (circuit de de
No de No
emulation) and encapsulated in ATM B No
cells, is concentrated together with
UMTS traffic generated by Node Bs RN
within an ATM switch. The aggre- C
gated stream is then carried on the No
transport backbone. This minimizes tic Back smis
the bandwidth required in the trans- /ra bo sio
dio ne n
mission backbone (see Figure 13). SD
This architecture is recommended if BT
the SDH nodes already exist, UMTS
traffic is very high and there is only
a moderate amount of GSM traffic (a
few E1s). It becomes mandatory if the
existing transport backbone cannot
support the new UMTS “incoming”
traffic without a capacity upgrade.
UMTS traffic (ATM) is concentrated within an ATM Fig. 15 RAN architecture
switch, while GSM traffic is multiplexed within an SDH
node. The aggregated ATM stream is then multiplexed
within an SDH node together with the GSM traffic (see Suburban Node B
This architecture is recommended if SDH nodes already Transmission
exist, UMTS traffic is very high and GSM traffic is very Node B Node
high. No ATM engineering is needed for GSM traffic in
this case. GSM traffic is treated independently. Network 2xE1
Figure 14b shows an optimized implementation of this RNC
case based on the Alcatel O-MSN (Optinex™ Multi-ser-
vice Node). An ATM switch – IP/SDH/ATM (ISA) 4xE1
board – is integrated in the SDH node and internal SDH Node B
multiplexing (no external cabling) is performed.
Alcatel Telecommunications Review - 1 st Quarter 2001 62 UMTS radio access network dimensioning
Typical RAN Dimensioning Results Conclusion
Let us assume an area to be covered made up of three Dimensioning is the first step in the design of a UMTS
subareas – urban, suburban and rural – with rollout Radio Access Network. It is important to note that it is
spread over three phases. Typical examples of RAN very different from GSM dimensioning. The characteris-
dimensioning results related to this area are given in tics of UMTS introduce greater complexity and make the
Tables 4 to 6. RAN designers’ task more interesting!
In order to propose a cost-effective RAN solution to its
partners, Alcatel has developed an innovative multi-ser-
Tab. 4 Node B results showing the number and con- vice dimensioning methodology which addresses the spe-
figuration of network elements in the RAN cific features of UMTS.
Phase 1 Phase 2 Phase 3 The technical parameters involved in this methodology,
as well as the process itself, are regularly enhanced based
Urban S333 0 S333 0 S333 8
on feedback from simulations and field trials conducted
S222 0 S222 6 S222 6
by Evolium SAS, the joint Alcatel-Fujitsu venture. s
S111 10 S111 4 S111 4
Suburban S222 0 S222 0 S222 10
S111 20 S111 30 S111 20
Rural 01 0 01 0 01 12 1. H. Biscéré: “RNC and UTRAN Interfaces dimensioning”,
* Cumulative figures September 2000.
S333 Three-sector site with three carriers per sector 2. Y. Dupuch: “UMTS Radio dimensioning rules”, September
S222 Three-sector site with two carriers per sector 2000.
S111 Three-sector site with one carrier per sector
O1 Omnidirectional site with one carrier 3. M. Bourguignon: “UTRAN Transmission network solu-
Bold figures indicate upgraded sites (additional carrier) from the previous tions”, November 2000.
Tab. 5 RNC results showing the number and configura- Hani Ramzi is Director of Mobile Network
tion of the network elements in the RAN Design within the Alcatel Mobile Communication
Phase 1 Phase 2 Phase 3 Division in Vélizy, France.
Large RNC 0 Large RNC 0 Large RNC 1
Medium RNC 0 Medium RNC 1 Medium RNC 1
Small RNC 1 Small RNC 1 Small RNC 0
The figures in bold represent the upgraded RNC (in capacity)
Tab. 6 RAN interface results
lu (lu-cs+lu-ps) Phase 1 Phase 2 Phase 3
Large BSC 70 Mbit/s
Medium BSC 50 Mbit/s 50 Mbit/s
Small BSC 30 Mbit/s 30 Mbit/s
These figures are provided to illustrate the types of output.
Accurate figures are derived on a case-by-case basis.
Figure 15 shows a typical RAN architecture.
Alcatel Telecommunications Review - 1 st Quarter 2001 63 UMTS radio access network dimensioning