1. August 2000 European Institute for Research and Strategic Studies in Telecommunications GmbH
Deliverable 2
Guidelines for the design
of UMTS Access Networks
Project P921-PF
2. Project P921
Services, applications and
Goals Quality of Service
The main target of this work was to UMTS is going to support a variety of services obtained by means of a link level simulator to
develop recommendations and guide- and applications, using both circuit and pack- corrupt the application bit stream and to
lines for UMTS network design and et switched access. In the framework of evaluate the degradation of the quality due to
implementation. These guidelines and EURESCOM project P921 three kinds of the radio interface.
recommendations are to support plan- applications have been selected for Quality of
ners and operators in designing and Service analysis: audio retrieval, MPEG-4 video The results of the tests have shown a strong
implementing efficient UMTS networks. download applications, and IP-based appli- impact of the UTRA interface on the Quality of
Application testing
Link Level Subjective
Application
Simulator Testing
Error Application
patterns performance
UTRA
character- QoS
isation
cations (web browsing, ftp). The objective of Service. For example, real time streaming
the quality test was to assess the impact of of high quality music over UMTS requires a
the UTRA (UMTS Terrestrial Radio Access) highly protected channel, at least when the
interface on the selected applications. The test application is not using any error resilience
method applied was to use the error patterns tools.
Cell coverage Cell breathing: left lower, right higher cell traffic
in UMTS
One of the fundamental characteristics of
CDMA systems implemented in UMTS is that
the coverage range is intrinsically linked to the
capacity of the system: the more traffic is
carried by a cell, the smaller the coverage area
of the cell becomes. This phenomenon is
known as “cell breathing“, which shows the
service area of one base station with different
traffic loads in the system. This dynamic
behaviour makes cell planning and network
dimensioning a very complex process.
Traditional static prediction methods are not Link level, considering the effects of the radio
appropriate. Therefore simulation and statis- channel on individual bits transmitted in a
tical modelling techniques have to be used. single communication.
However, the system is very complex, with so System level, considering a number of cells
many interactions, that the simulation has and mobiles, based on output parameters
been split into two parts: from individual link simulations produced at
link level.
3. UTRAN characterisation
UTRAN, the UMTS Terrestrial Radio Access Resulting system working point for the 8 kbit/s voice service
Network, operates in two modes, the UTRA as a function of mobile speed and number of users per slot
FDD and the UTRA TDD mode. The UTRAN (downlink – Vehicular A channel)
link level simulation results of P921 are given
for the voice service, circuit switched data
System working point [Eb/No @ BER = 0,1 %]
service (LCD, Long Constrained Delay) and for
15
packet switched data service (UDD Uncon- 8 users
per slot
strained Delay Data) over the ETSI / ITU 14
propagation channels (vehicular A/B, outdoor 13
4 users
to indoor A/B). The simulations include 12 per slot
realistic algorithms for closed loop power 11
1 user
control and pilot assisted channel estimation. per slot
10
For the up-link channel, the antenna diversity
9
technique has been implemented by doubling
the Rake receiver structure and using an equal 8
gain combiner before decoding. Voice service 7
was simulated at 8 kbits/s, and LCD and UDD 1 10 100 1000
services at 64, 144 and 384 kbits/s. Mobile speed [km/h]
Link budget Link-level simulation results
and cell sizes Cell radius [km]
The link budget is calculated by the following 2,0
UMTS speech
procedure:
1. Uplink path loss evaluation 1,5
GSM 1800
2. Downlink power level evaluation at cell
border
1
3. Downlink EIRP value evaluation per traffic UMTS LCD384
(Long Constrained
channel (Effective Isotropic Radiated Power Delay 384kb/s)
– i.e. how much power you would be trans- 0,5
mitting if transmitting in a perfect sphere) UMTS UDD480
(Unconstrained
4. Downlink power evaluation per traffic 0 Delay Data 480kb/s)
channel 21 22 23 24 25 26 27 28 29 30
5. Downlink path loss evaluation Average power of the mobile station [dBm]
On the basis of the radio link results the UMTS
(FDD component based on W-CDMA access)
link budget has been evaluated for the case of a function of average power of the mobile sta- cell radius is greater than the one of GSM
an urban environment. The cell radius of the tion and offered service (70 % cell load). The 1800. In contrast to this, the coverage in UMTS
UMTS system has been compared with the UMTS cell radius is compared to the cell radius is smaller than in GSM 1800 systems for the
one of GSM 1800. The figure presents results of a GSM 1800 system. It is worth noting that other services.
from link level simulations: The coverage range in the GSM 1800 case the cell radius is not
of UMTS services in the urban environment as related to the system load. The results show
that, in the case of a voice service, the UMTS
UTRAN architecture
The UMTS Radio Access Network is built RNC is connected to the Core Network (both that cells and RNCs are identified – normally
around two new nodes and three new inter- packet and circuit domains) by the Iu inter- by the number of bits in the identities, but
faces (see the figure). The Node B is effec- face; RNCs are connected together with the sometimes hidden elsewhere in the protocol
tively a UMTS “base station“, while a Radio Iur interface. Each Node B is connected to an definitions. There is currently no restriction of
Network Controller (RNC) is comparable with RNC by the Iub interface.There are some fun- the numbers of Nodes B in a Radio Network
a GSM Base Station Controller (BSC). Each damental limits on the numbers of cells and Subsystem (RNS) or PLMN.
RNCs that can be supported, due to the way
4. UTRAN architecture
According to standardisation the limits are as
follows:
s Maximum number of Cells in a PLMN Iu Iu
26,435,456
s Maximum number of RNCs in a PLMN RNS RNS
4,096
s Maximum number of Cells in an RNS RNC RNC
65,536 Iur
s Maximum number of Nodes B in an RNS
No limit defined in the standards Iub Iub
s Maximum number of Cells in a Node B
Node B Node B Node B Node B
No limit currently defined in the standards
In practice, the maximum numbers supported
by the vendors will vary and are likely to be
lower than the absolute limit stated here.
Infrastructure sharing
Given the limited number of sites for new base operators. In contrast to the mechanical antennas and feeders, and assuming that
stations, and the cost of errecting new masts, issues, there should be no problem with the the structure is capable of withstanding the
site sharing between 3G and GSM is likely to co-location of W-CDMA and GSM900/1800 additional wind load. This has to be deter-
be of importance, especially for existing sites. It should be possible to share the same mined on a case by case basis.
headframe between GSM and UMTS, assum-
ing there is sufficient space for the additional
Hierarchical cell structures
UMTS, as GSM, supports the deployment of specified in UMTS will result in a minimum equipment designed to a later release of the
micro cells within macro cells to provide obtainable cell radius, which is accentuated standards is available. These issues require
increased capacity in traffic hot spots and when good line of sight is achieved. There is further investigation. There are two options for
coverage where previously none has existed. also some doubt about the suitability of the the choice of carrier for micro cells:
However, there is some concern that the currently specified soft handover mechanism s Same carrier for micro/macro cells
limited dynamic range of the terminal power as for use in contiguous micro-cellular coverage s Different carriers for micro/macro cells
areas. Therefore it could be that micro cells
cannot be designed to perform optimally until
Increasing the coverage area
The UTRAN will support six sectored sites, 3 sectors – 900 beamwidth (left) compared to 6 sectors –
which could maximise coverage and capacity 600 beamwidth (right)
of UMTS sites. The basic principle is that by
using six narrow beam antennas, the coverage
area of a cell will be extended due to the
increased forward gain, and the capacity will
be double that of a three-sectored cell. The
use of six sectors can lead to an increase in
the coverage area that is served by multiple
cells (i.e. the soft handover region), depend-
ing on the local propagation conditions and
the antenna pattern. The two figures show the
overlap between the antenna patterns. This
does not match the soft handover regions, but
it shows, how the overlap can increase, given
certain antenna beamwidths.
5. Conclusions
s The number of services in a UMTS system coverage is intrinsically linked to the performance of the TDD mode is more influ-
is substantially higher compared to GSM, capacity of the system. Cells are breathing; enced by the mobile speed than the FDD
which makes the network design more the coverage range for voice varies between mode. For the voice service, the UMTS cell
complex. Packet switched mode allows cost- 200 m and 1.4 km, depending on the radius is greater than the GSM 1800 one.
effective transport of data, but requires QoS number of users. Traditional static predic- Data services with data rates higher than
control. Some applications such as voice or tion methods for network planning are not 384 kbit/s have a lower cell radius com-
real-time video require throughput with a applicable. pared to GSM 1800.
guaranteed data rate and maximum delay. s Two link level simulators (W-CDMA and TD- s The Project has reviewed available system
Mobile communication applications have to CDMA) have been developed in the project level simulators, and established scenarios
be designed according to the user mobility, to evaluate the radio performance of UTRA. for system level simulations. A future pro-
the radio environment (user speed and The main outcome of link level simulations ject is envisaged to analyse these scenarios.
coverage radius), the application topology, is the system working point, the minimum
and the user terminal requirements. Eb/No (ratio between energy per bit and A more detailed version of this deliverable is
Current applications content, e.g. JPEG, noise). Voice services have an almost available at:
does not allow missing data. constant system working point with respect
s UMTS radio interface has a strong impact to the mobile speed in the range of http://www.eurescom.de/
on the QoS of applications, requiring an 3-250 km/h. Data services (LCD & UDD) public/projects/P900-series/
error-resistant mechanism to obtain the are more sensitive to the mobile speed and p921/P921.htm
required QoS level. In a CDMA network to the propagation environment. The link
About P921 Publications resulting from this work:
EURESCOM Project P921-PF started on 1. D. Wake and R. E. Schuh, IEE Electronics 3. Ralf E. Schuh and David Wake, Proceedings,
23 February 1999 with a planned duration of Letters, vol. 36, no. 10, pp. 901-902, 2000. IEEE International Conference on Third
18 months. The total budget was 100 MM. 2. D. Wake and R. E. Schuh, Technical Digest, Generation Wireless Communications, IEEE
Additional information can be obtained from: International Topical Meeting on Microwave 3g Wireless'2000, San Francisco, Silicon
Photonics – MWP’99, Post deadline paper, Valley, USA, ISSN No. 1529-2592 (2000),
http://www.eurescom.de/
Session F-12, pp. 9-12, ISBN 0-7803-5558- pp. 48 – 51, June 14 - 16, 2000
public/projects/P900-series/
X, Melbourne, Australia, November 17 – 19,
p921/P921.htm
1999.
The Project team:
Project Members
Name Company Email
Josef Noll (Project Leader) Telenor josef.noll@telenor.com
Jon Harris BT jon.w.harris@bt.com
Milan Jankovic Community of Yugoslav PTT ljiljamj@eunet.yu
Borislav Odadzic zjptt@eunet.yu
Armando Annunziato CSELT – Telecom Italia Group armando.annunziato@cselt.it
Enrico Buracchini enrico.buracchini@cselt.it
Bruno Melis bruno.melis@cselt.it
Anne-Gaële Acx France Télécom annegaele.acx@rd.francetelecom.fr
Jean-Francois Chaumet jeanfrancois.chaumet@rd.francetelecom.fr
Nicolas Guerin nicolas.Guerin@rd.francetelecom.fr
Georgos Agapiou OTE gagapiou@oteresearch.gr
Dimitrios Xenikos dimitrios.xenikos@oteresearch.gr
Amparo Sanmateu T-Nova amparo.sanmateu@telekom.de
Ignacio Berberabana Telefónica I+D ibfm@tid.es
Héctor González hector@tid.es
Fernando Martinez fvega@tid.es
Jorge Montero jams@tid.es
Arild Jacobsen Telenor arild.jacobsen@telenor.com
Tor Jansen tor-magnus.jansen@telenor.com
Tore Arthur Worren tore-arthur.worren@telenor.com
Uwe Herzog (Project Supervisor) EURESCOM herzog@eurescom.de
