Implementation
ImplementationChapter 8
WCDMA Radio Network Design
OBJECTIVES:
Upon completion of this chapter the student will be able to:
List capabilities of the RBSs in Ericssons RBS portfolio
Describe concepts such as spurious emissions, intermodulation
products, transmitter noise and receiver blocking
Describe what co-existence problems can appear, in particular
for WCDMA and GSM
8 Implementation
Table of Contents
TopicPage
111INTRODUCTION
RBS 3000 Summary112The rBS 3000 family115RBS 3000 Macro
versions115RBS 3000 Mini versions118RBS 3000 Micro version121wTRU
plug-in123RRU, Remote Radio Unit124Expansion of the
RBS125Configurations126RBS characteristics127Product
Evolution128Adaptive antenna128Interference cancellation128Transmit
diversity128radio network design data for the macro
rbs129Overview129RBS reference point129multi carrier power
amplifiers129RBS output power130RBS Sensitivity131RBS
configurations132RBS capacity134HW elements134TMA134Feeder
Types135Antenna types135User equipment137User equipment output
power137User equipment sensitivity137Antenna gain of user
equipment138Concepts and definitions139Frequency bands139Guard band
and carrier separation140Isolation between
systems140Interference142General considerations142General isolation
requirements143Interference analysis145Spurious
emissions146Transmitter noise147Intermodulation products147Receiver
blocking150The near far problem150Systems coexisting with
WCDMA153WCDMA with WCDMA153WCDMA with WCDMA TDD154WCDMA with
GSM157Summary160
INTRODUCTION
RBS 3000 is a family of Radio Base Stations (RBSs), built upon
the worldwide experience obtained from building and deploying
Ericsson mobile telephone systems.
A description of the RBS 3000 family is given in this chapter,
but in addition to the RBSs, some other Ericsson products are also
briefly mentioned.
RBS 3000 Summary
The following is a summary of the RBS 3000 base station family
of products.
Standard: The RBS 3000 family is based on 3GPP requirements.
Installation: The RBS 3000 is delivered pre-tested and
pre-configured to the site including a built-in self-test mechanism
and the Equipment Configuration Wizard enabling of the
configuration which leads to reduced installation time and faster
network roll-out.
Operation and Maintenance
The RBS 3000 is accessible for the execution of management tasks
from any node in the network. The following features exist to
ensure minimal service impact during change or maintenance
activity:
Software corrections and software upgrades can be performed
while the RBS 3000 is in operation.
RBS hardware (plug-in units) can be replaced using hot-repair
principle.
RBS hardware can be added while the RBS 3000 is in
operation.
The RBS 3000 has a root-cause fault location capability.
The RBS 3000 node can be ordered into power saving mode
(optional function) in order to lower the overall power
consumption.
Transmission: Most common transmission standards are supported
and different transmission configurations (cascading, star and
tree) can be combined to support different network structures for
RBS 3000.
Reliability: The RBS 3000 includes a number of redundancy
concepts (such as N+1 redundancy, load sharing and processor
cluster) for increased availability and reduced downtime.
Flexibility: One and the same RBS 3000 equipment configuration
handles different, time-varying traffic mixes consisting of voice,
circuit switched and packet data services which gives a RBS that
does not have to be reconfigured depending on what kind of traffic
it handles.
Expandability: An increase in coverage, number of simultaneous
users, number of carriers and number of sectors is easily achieved
by adding extra hardware boards or extra cabinets to the RBS 3000.
Furthermore will future development with more integrated solutions
will give the possibility to get more capacity by replacing
hardware
Evolution: The RBS 3000 is designed for future capacity
improvements and reduced power consumption. This evolution is
achieved by e.g. interference cancellation, adaptive antenna
techniques, improved MCPA efficiency, more advanced ASICs and
transmit diversity.
Site Solutions provide easy logistics and implementation
advantages, giving short lead-time from ordering to cut over at
site.
The RBS 3000 Family of Products
Indoor Macro1-4 carriers, 1-6 sectors, 20/40 W carrier using
internal power supply for 230 VAC or +24 VDC.
Indoor Macro1-4 carriers, 1-6 sectors, 20/40 W carrier using a
-48 VDC external power supply.
Outdoor Macro1-4 carriers, 1-6 sectors, 20/40 W carrier, power
system and battery backup integrated in cabinet. External supplied
power 230/380 V AC
Indoor MiniCompact size, 3 sectors, 1-2 carriers per sector or
six sectors: One carrier per sector, integrated power supply. Macro
coverage by use of Remote Radio Units. Outdoor MiniCompact size,
convection cooled, weatherproof outdoor RBS with the same
specification as the indoor Mini.
MicroA small, lightweight, weatherproof base station with no
floor space requirements. 1 carrier, 1 sector, 1 W/carrier
integrated RF output and optional Remote Radio Unit for extended
coverage.
wTRU conceptThe wTRU concept gives a fast and smooth way to
quickly build WCDMA coverage. The wTRU uses two empty TRU slots in
a already installed GSM RBS 2000 cabinet. Together with a Remote
Radio Unit the wTRU concept gives one carrier and 1-3 sectors. RRU,
Remote Radio UnitRemote radio head including transceiver and power
amplifier. RRU has up to 10 W RF output power. And can be connected
to mini or micro RBSs and wTRU via a digital interface.
Pre-assembled site solutionsAll types of RBSs are available in
pre-assembled outdoor containers, including everything needed to
build a complete site.
The rBS 3000 family
RBS 3000 Macro versions
General
All RBS 3000 macro models are designed to handle a variety of
services. The RBS hardware and software has a modular design.
The RBS hardware is flexible and no exchange of equipment is
needed for different traffic situations. Within a certain range,
any mix of voice and data services can be handled by the same
hardware.
The RBS architecture is scalable and thereby easy to expand.
Adding extra carriers or more channel capacity is done by adding
extra boards or a complete cabinet.
RBS indoor macros
Overall characteristics
Indoor RBS
Internal or external power supply
1-4 carriers
1-6 sectors
20 or 40 W/carrier
Figure8-
SEQ Figure \* ARABIC 1 RBS indoor macro (internal power supply
unit) configured for three sectors with two carriers each
Figure8-
SEQ Figure \* ARABIC 2 RBS indoor macro (external power supply
unit) configured for three sectors with two carriers
each.Cabinet
All units in the cabinets (see figures 8-1 and 8-2) are easily
accessible from the front of the cabinet. There are no requirements
on access to the cabinets from the sides or the back, which implies
that the cabinets can be mounted side by side with the back to a
wall. All cable interfaces are located at the top of the
cabinets.
RBS outdoor macro
Overall characteristics:
Outdoor RBS
External power supply
1-4 carriers
1-6 sectors
20 or 40 W/carrier
Figure8-
SEQ Figure \* ARABIC 3 RBS outdoor macro configured for three
sectors with two carriers each.Cabinet
The RBS outdoor macro is weatherproof outdoor cabinet for
outdoor sites with high capacity and high coverage. The RBS outdoor
macro houses integrated power supply with backup batteries, space
for transmission equipment and climate package for ensuring an
indoor climate for all units installed.
RBS 3000 Mini versions
The Mini RBS consists of a Main Unit and up to six Remote Radio
Units (radio heads), connected via a digital interface (see figure
8-3). The Remote Radio Unit is flexible and can be placed at the
Main Unit cabinet, on the roof or in the tower near the antenna.
The high output power together with placing the Remote Radio unit
closed to antenna makes the Mini RBS suitable for macro
coverage.
The Mini RBS concept is a cost-effective complement to the Macro
RBS for sites with limited space or sites where the capacity of a
Macro RBS is not needed.
Overall Characteristics
Indoor RBS Three sectors: 1-2 carriers per sector or six
sectors: One carrier per sector.
Up to 10 W RF output power per sector-carrier using RRU (RRU
mandatory)
Power supply integrated in the Main Unit
Figure8-
SEQ Figure \* ARABIC 4 The indoor Mini RBS, in a 3-sector
configuration
The indoor Mini RBS
The indoor Mini RBS together with Remote Radio Units and an
optional external backup battery cabinet constitute a complete,
very compact, base station solution.
Figure8-
SEQ Figure \* ARABIC 5 Indoor Mini RBS
Cabinet
The indoor Mini RBS cabinet, including fan unit and power
supply, can be mounted on the wall or placed on the floor or on a
shelf, see figure 8-5.
RBS Outdoor Mini
The outdoor Mini RBS is a complete RBS system housed in a
compact convection cooled weatherproof cabinet.
Delivery of a pre-configured and pre-tested outdoor Mini RBS
requires a minimum of site preparations and installation work,
supporting fast network roll-out.
Since the outdoor Mini RBS offers macro cell coverage in a
microcell package (figure 8-6), it can serve both as a traditional
macrocell base station and a microcell base station.
Figure8-
SEQ Figure \* ARABIC 6 Outdoor Mini RBS with Remote Radio Units
in a 3-sector configuration.
Cabinet
The Main unit is a compact, convection-cooled unit, which can be
mounted anywhere - on a wall, on a pole, on the side of a building,
or on a rooftop.
The Main Unit houses transmission interface to RNC, performs all
system-level diagnostics, provides system timing via the
transmission interface source, performs power control and call
processing, performs WCDMA encoding and decoding and performs
softer handover.RBS 3000 Micro version
General
The RBS micro version is based on Ericssons long experience in
designing micro and pico base stations for 2nd generation mobile
telephone systems.
The micro RBS is weather proof to withstand rough environment;
at the same time as the appearance is suitable for discrete
installation. The design gives a small, low weight RBS, which can
easily be installed by one person (figure 8-7).
Overall characteristics
Suitable for both indoor and outdoor use
One carrier
Omni or Sector
1 W
External antenna as option
RRU Remote Radio Unit for macro coverage as an option
Power and battery cabinet as option
Figure8-
SEQ Figure \* ARABIC 7 The Micro RBS
Hardware units
The Micro RBS has the same basic functionality as the Macro RBS.
The difference is in capacity and coverage.
The transceiver and power amplifier is integrated into the RBS
cabinet. This is achieved by using highly integrated ASIC
technology resulting in high availability, small volume, low weight
and low power consumption.
Cabinet
The cabinet houses one transceiver plus common equipment needed
for serving one cell. Convection cooling and heater functionality
allows the use of a small and weatherproof cabinet.
Antenna System
The Micro RBS supports these types of antenna
configurations:
Integrated directional antennas for cell coverage, supporting
micro cell space diversity (TX/RX, RX).
Integrated omni antennas for cell coverage, supporting micro
cell space diversity (TX/RX, RX).
A two feeder interface for external antennas, space/polarization
diversity compatible (TX/RX and RX antennas).
A single feeder interface for an external antenna/antenna
system, for the non-diversity case (TX/RX).
RRU Remote Radio Unit for macro coverage as an option.
Remote Radio Unit
The Remote Radio unit can be used together with the RBS 3301 to
increase the coverage of the Micro RBS.
wTRU plug-in
The wTRU plug-in is a cost-effective solution for rapid rollout
of moderate WCDMA capacity. The wTRU can be deployed within a
partially filled Ericsson GSM RBS 2000 cabinet, uses two TRU slots
in an RBS 2000 cabinet, allowing the shared use of resources such
as power and cooling (figure 8-8). The wTRU supports one carrier
and 1-3 sectors.
Figure8-
SEQ Figure \* ARABIC 8 wTRUCabinet
The wTRU is plugged into a RBS 2000 cabinet. So the wTRU is not
containing any cabinet. The RBS 2000 cabinet cools the wTRU.
RRU, Remote Radio Unit
The Remote Radio Unit (RRU) is a radio head with up to 10 W RF
output power, used together with Mini RBS and wTRU (figure 8-9). It
can optionally also be used together with the Micro RBS to get
extended coverage.
The Remote Radio Unit houses RF filter, power amplifier, RX Low
Noise Amplifier and TRX for one sector-carrier. RX space diversity
is supported. It can be placed at the cabinet, on the roof or in
the tower near the antenna.
An optical digital interface is used between Main Unit and
Remote Radio Unit. This ensures high performance and makes it
possible to place the Remote Radio Unit up to 300 meter from the
Main Unit.
As many different Main Units support the optical digital Remote
Radio Unit interface, the Remote Radio Units can be re-used when
upgrading the Main Unit to higher capacity.
Figure8-
SEQ Figure \* ARABIC 9 RRU, Remote Radio UnitCabinet
RRU is weatherproof and suitable for both indoor and outdoor
placement. It generates no significant acoustic noise, as only
conventional cooling is used.
RRU can be mounted in the antenna tower or close to the main
unit.
Expansion of the RBS
The RBSs can be expanded by
Adding Carriers
Adding redundancy
Adding Sector
Adding Capacity
Increasing Coverage
Other options are also available such as
Tower Mounted Amplifier (TMA)
Circuit emulation
Handling of external alarms
Redundancy for baseband parts
Power Saving Mode
Remote Electrical antenna Tilt
Add one carrier
Adding carriers for increased capacity or coverage can easily be
done by adding boards or cabinets. For easy optimization of needed
capacity it is possible to add one cell-carrier in any sector, for
example (1,1,1) can be added to be, i.e. (1,2,1). Each number
describes the number of carriers in each sector in a 3-sector
RBS.
Add channel elements
The amount of channel elements included in the RBS can be
optimized to fit the current need depending on type of users and
the amount of users using the different services.
The RBS is prepared for future capacity upgrades utilizing more
highly integrated ASICs, as they become available for later
releases.
Extend coverage
Coverage can be extended for certain configurations by
installing extra amplifiers. By having more output power in the
downlink the cell range and/or the capacity can be increased.
Configurations
Example of RBS Product Configurations
The table below specifies some examples of configurations for
RBS 3000 Macro family.
Table 1: Configuration examples for the RBS indoor macros
Config. (sectors x carriers)No. of RBS CabinetsOutput power
per
sector-carrier
1x1120/40 W
1x2120 W
3x1120/40 W
3x2120 W
3x3220 W
3x4220 W
6x1220/40 W
6x2220 W
For configurations with one carrier per sector there is one
TX/RX and one RX antenna in each sector, for the RBS indoor macro.
For configurations with two to four carriers per sector there are
two TX/RX antennas.
Note that the number of antennas is reduced if cross-polarized
antennas are used.
RBS characteristics
The RBS 3000 family is based on 3GPP requirements.
System data
Receiver:
1920-1980 MHz
Transmitter:
2110-2170 MHz
Channel bandwidth:5 MHz
Duplex Separation:190 MHz
Output power
Nominal output power per carrier at RBS TX antenna
connector.
Macro indoor and outdoor RBSs
All configurations:
43 dBm
High coverage version (1x1, 3x1, 6x1):46 dBm
Remote Radio Unit
40 dBm
The micro RBS
30 dBmProduct Evolution
Additional features for boosting coverage as well as capacity
will be introduced in the future. Some of the important methods for
improving the performance that Ericsson is studying are listed
below.
The RBS architecture is designed for later introduction of
capacity and interference improving techniques. This ensures a
smooth upgrade of the system.
Technical evolution such as new highly integrated ASICs, new RF
power transistor technology and new cooling concepts will result in
higher capacity and less power consumption.
Adaptive antenna
Adaptive antenna arrays is a technology that will boost both
capacity and/or coverage. Investigations are ongoing with field
trials among many other tests to evaluate this technique. The
adaptive antenna gives better performance in both up- and
downlink.
Interference cancellation
Interference cancellation (IC or Multi-User Detection) is
another promising technology, which could improve up-link capacity.
This will give a capacity benefit mainly in the up-link. Ericsson
is currently looking into different types of IC schemes.
Transmit diversity
Transmit diversity has initially been studied in both ARIB and
ETSI and the work is now continued in 3GPP. It has been shown
through simulations that transmit diversity provides a significant
gain in some scenarios.
radio network design data for the macro rbs
Overview
Here some data on the macro RBS and related equipment such as
antennas and User Equipment, UE is presented.
RBS reference point
The reference points for the transmit power (TX reference point)
and for sensitivity (RX reference point) are shown in Figure8-10.
There are two separate cases; without TMA and with TMA.
Figure8-
SEQ Figure \* ARABIC 10 Reference point definitions
It is important to note that these reference points are for RF
planning purposes only. Some system processes and algorithms such
as, for example, the handover algorithm, may use different
reference points.
multi carrier power amplifiers
A Multi Carrier Power Amplifier (MCPA) is an ultra linear power
amplifier that can transmit more than one carrier frequency. This
is advantageous in WCDMA radio networks since the alternative is
using (more) single carrier power amplifiers and either combine,
with losses, the output to one antenna (which is only possible if
there is a guard band) or using several feeders and antennas.
RBS output power
The maximum output power values for various configurations of
the macro RBS are listed in Table 2.
Table 2: Output powers of Macro RBS configurations
Configuration (sectors x carriers)No. of RBS cabinetsOutput
power per sector
1x1120/40 W
1x2120 W
3x1120/40 W
3x2120 W
3x4220 W
The maximum output power is determined by the configuration of
the MCPAs in the RBS. Each cabinet has six MCPA units, which are
used either singularly for a 20 W per sector output or in parallel
pairs for a 40 W per sector output. The 40 W configuration is only
available on site configurations with a single carrier per
sector.
A schematic displaying the two possible MCPA configurations is
shown in Figure8-11. The connection between the Transceiver Board,
TRXB, the MCPAs and the antenna system is via the Antenna Interface
Unit Board, AIUB.
Figure8-
SEQ Figure \* ARABIC 11 MCPA configurations for 20/40 W
output
In the future the capabilities of the RBS will be expanded to
allow a 40 W output power with more than one carrier per
sector.
RBS Sensitivity
The sensitivity of a WCDMA RBS is dependent on the user data
rate, the Eb/Io (bit energy over interference energy), the thermal
noise figure and the RBS noise figure. The data rate and Eb/Io are
dependent on the particular Radio Access Bearer, RAB and channel
model used.
The Unloaded RBS sensitivity (i.e. the sensitivity level without
any interference contribution from other UEs) can be expressed
as:
RBSsens = Nt + Nf + 10log(Ruser) + Eb/Io(1)
where
Ntis the thermal noise power density
Nfis the noise figure
Ruseris the user bit rate (information bits per second,
excluding retransmission)
Eb/Iois the bit energy level over noise level
The following noise figure values may be used for planning
purposes.
Thermal noise power densityNt = 174 dBm/Hz
Noise figureNt = 3 dB with TMA, 4 dB without TMA
In Table 3 some RBS sensitivity levels with TMA are given.
Table 3: RBS sensitivity levels [dBm] with TMA. The figures are
given at the TMA antenna connector.
Service Pedestrian A 3km/h
Speech 12.2 kbps125.9
Circuit 64 kbps119.0
Packet 128 kbps118.0
The figures presented are based on values from the RTT
submission to ITU.
RBS configurations
The macro RBS can be configured in a single or double cabinet
installation. In the single cabinet case the maximum configuration
possible is a 3 x 2 (3 sectors with 2 carriers per sector). The
double cabinet case can support a 3 x 4 configuration.
Note: A 3 x 2 configuration can also be written as a 222 and a 3
x 4 as a 444 where the notation is of the form: (number of carriers
in sector 1) (number of carriers in sector 2) (number of carriers
in sector 3).
The single and double RBS case support all sub-configurations of
the maximum. For instance with a single cabinet there can be a 3 x
1 (111) or a 2 x 1 (11) configuration. Sectors can have different
numbers of carriers, for example 221 or 112. In the double cabinet
case examples of sub-configurations are 333, 223 or 43 (2
sectors).
All RBS configurations use the same AIUB but the Combiner and
Splitter Unit, CSU, which is part of the AIUB must be configured in
each case depending on number and configuration of sectors,
carriers, MCPAs and antennas.
There are five different CSU Configuration types, A to E, but
the A and C types are not used initially. The CSU configuration is
changed by software command but a site visit is necessary to change
from one to two transmit antennas per sector and vice versa.
The configurations and options are summarized in Figure
8-13.
Figure8-
SEQ Figure \* ARABIC 12 RBS configurations with CSU type (B, D
and E)
Note that when there are three carriers per sector then there
are two different CSU configurations used. In this case two of the
carriers are transmitted from one antenna and the third carrier is
transmitted from a second one.
In future releases of the macro RBS there will be both increased
functionality such as transmission diversity and more
configurations, up to 6 x 4.
RBS capacity
The traffic throughput of the macro RBS is determined by the
capacity of the Baseband Subsystem. The TXBs and Random Access and
Receiver Boards, RAXBs process the downlink and uplink
respectively.
HW elements
TMA
A TMA, Tower Mounted Amplifier, is mounted close to the
receiving antenna where it amplifies the uplink signal before the
main length of the feeder. The benefit of this is an improved RBS
performance on the uplink.
Figures showing the impact of using a TMA on RBS noise figure
and sensitivity have already been listed in previous sections.
In addition to improving the RBS sensitivity inserting a TMA
into the feeder path results in a loss on the downlink power
budget, LTMA.
TMA loss LTMA = 0.4 dB
The TMA available for WCDMA is a double dual duplex TMA unit. A
dual duplex TMA has two duplexers, one before the low noise
amplifier and another after it. This allows the use of one feeder
for both the uplink and the downlink signals. The double dual
duplex unit contains two dual duplex TMA units. A schematic is
shown in Figure8-13.
Figure8-
SEQ Figure \* ARABIC 13 Double dual duplex TMA unit
Feeder Types
Typical feeder types and their attenuation are listed in Table
4.
Table 4: Typical attenuation for feeder cables.Feeder
typeAttenuation [dB/100m]
LCF 15/84.2
LCF 11/4 5.3
LCF 7/8 6.5
LCF 1/2 10.5
Antenna types
The antenna types that will be supplied by Ericsson for use with
WCDMA are presented in the following table.
The antennas have 3 tilt options:
FET Fixed Electrical Tilt
MET Manually adjustable Electrical Tilt
RET Remotely adjustable Electrical Tilt (adjusted using the
RANOS system)
The TMA can, if required, be mounted as an integrated part of
the antenna unit for all of the antennas listed.
Table 5: Antennas offered by Ericsson
BandGain [dBi]Half Power BeamwidthSize /mTilt Options*
UMTS15.0 65(0.7FET/MET/RET
17.0 65(1.3FET/MET/RET
20.0 65(2.0FET/MET/RET
19.0 45(1.3FET/MET/RET
22.0 33(2.0FET
1710 2170MHz15.0 65(0.7FET/MET/RET
17.0 65(1.3FET/MET/RET
20.0 65(2.0FET/MET/RET
900/UMTS15/17 65(1.3MET(9/U) RET(U)
17/19 65(2.6MET(9/U) RET(U)
1800/UMTS15/15 65(0.7MET(18/U) RET(U)
17/17 65(1.3MET(18/U) RET(U)
19/19 65(2.0MET(18/U) RET(U)
900/1800 /UMTS15/17/17 65(1.3MET(9/18/U) RET(U)
17/18/19 65(2.0MET(9/18/U) RET(U)
*In many cases a particular tilt option is not available for all
bands supported by an antenna. In this case the tilt type is listed
and the bands for which it is available are listed in brackets
using the following notation: 9=900MHz, 18=1800MHz, U=UMTS.
User equipment
User equipment output power
There are 4 User Equipment, UE, classes defined for WCDMA. The
maximum output powers are listed in Table 6.
Table 6: User Equipment output power at the antenna
connector.
ClassOutput power [dBm]
133
227
324
421
The recommended UE class to use when planning for handheld units
is Class 3.
User equipment sensitivity
The unloaded sensitivity is calculated in the same way as for
the RBS, assuming a noise figure (Nf) of 7 dBY IF = Y "" "
[ECS/Peter van de Berg]" \* MERGEFORMAT .
Table 7: User equipment sensitivity levels at the antenna
connector for some RABs and the pedestrian A channel model
[dBm].
Service Pedestrian A
Speech 7.95 kbps119.3
Circuit 64 kbps112.5
Packet 128 kbps111.3
Antenna gain of user equipment
While antenna gain may vary between manufacturer and between
various types of UEs, the following values are recommended for
planning purposes:
UE antenna gain, non hand-held Gant,UE = 2 dBi
Concepts and definitions
Frequency bands
The different bands utilised by the different systems discussed
in here are shown in Figure8-14. The most critical co-existence
situations occur when the DownLink (DL) of the interfering system
(aggressor) is close to the UpLink (UL) of the interfered system
(victim). In that case the Radio Base Station (RBS) of the
interfering system is constantly disturbing the victim RBS,
probably with high gain antennas on both sides.
When a TDD system is the aggressor, both DL and UL can be close
to the victim UL.
User Equipment (UEs) may also be close to each other and cause
interference, but this happens only occasionally. RBS and UE may
also interfere each other in special situations.
Figure8-
SEQ Figure \* ARABIC 14 Operating frequency bands for 2G/3G
mobile communication systems.
The PCS 1900 spectrum in the U.S. and Canada is allocated by
three 5 MHz blocks, and three 15 MHz blocks. The base station
transmit band is the same as much of the WCDMA RBS receive band,
hence the systems will need to be modified in order to coexist.
However WCDMA technology and services can be deployed in any of the
three 15 MHz blocks, for PCS operators who use a spectrum
re-farming strategy.
Guard band and carrier separation
Guard band means the unutilised frequency band between two
cellular systems, i.e. the area between two operators outside the
allocated spectrum. Carrier separation means the distance between
the centre frequencies of two adjacent channels.
Isolation between systems
Isolation between systems is defined as the attenuation between
the transmitter reference point in the interfering system (RBS or
UE) and the receiver reference point (RBS or UE). Isolation is
required between transmitter reference points also. In Figure8-15
the DL of one RBS disturbs the UL of another RBS. The isolation
between the reference points in this case is:
Isolation = Lf1 GA1 + Lp GA2 + Lf2 + LxWhere,
Lf1 and Lf2are the feeder losses of feeders 1 and 2
GA1 and GA2 are the antenna gains of antennas 1 and 2
Lpis the propagation loss
Lxis losses in an extra filter
Figure8-
SEQ Figure \* ARABIC 15 Isolation between systems as defined in
this document. Isolation is the total path loss due to feeder
losses, propagation and attenuation in any extra filters or other
devices.
The propagation loss can, for distances in the far field zone of
the antenna (>10 m), be approximated by free space
propagation.
Lp = 32.4 + 20log(d) + 20log(f)Where,
dis distance [km]
fis frequency [MHz]
For short antenna separations the value of ( GA1 + Lp GA2) can
be replaced with a measured coupling loss of typical antennas.Many
of the co-existence problems discussed here can be solved through
the use of additional filters. There are several useful filter
products available on the market and Ericsson also provides some
types. Since the desired filter performance depends highly on the
exact situation regarding frequencies, frequency response curves,
attenuation etc. no specific filter products are mentioned.
When the required isolation is not fulfilled it appears as
degradation of the receiver sensitivity performance.
The type of filter that is needed depends on whether the
detailed characteristics of the RBS are known or not. It is not
unusual that the RBS is actually better than what is required in
the technical specifications. If the characteristics are known, as
they are for an Ericsson RBS, it may be possible to use filters
with lower attenuation.
Interference
General considerations
There are a number of considerations that may affect the
likelihood of interference:
When MSs or UEs are the interferers, they may be treated as
transitory interference sources, by assuming mobility and short
transmit duration.
Reception impairments due to bursty interference may be
recovered by error correction and interleaving techniques specified
in mobile communication standards, though the dynamics of various
algorithms, such as power control, may also be affected.
Directional antennas may provide additional attenuation due to
the off-beam discrimination characteristics.
RBSs, UEs or MSs may not be transmitting at full power, except
when service at the coverage edge is required.
RBSs may be deployed with sufficient power margins avoiding
operation close to the receiver sensitivity levels. Typical margins
may account for Rayleigh fading, in-building penetration, handover,
etc.
Equipment performance may be better than the minimum
requirements specified in the mobile communication standards.
Operators providing service to the same (and/or adjacent)
coverage area may coordinate their deployment of RBSs. This may be
due to network performance considerations, availability of new cell
sites, regulatory requirements, commercial considerations, etc.
However, worst-case data for interference analysis is used
below, based on minimum requirements stated in mobile communication
specifications.
General isolation requirements
Co-sited equipment
The testing of macro RBSs always includes a 30dB isolation
between TX-RX reference points. This means that the RBS performance
specified is not guaranteed without this isolation.
The 30dB isolation requirement is easy to achieve between
antennas. There are dual polarized antennas with 30dB isolation
between the two internal arrays. An additional requirement is to
keep at least 30dB isolation between all antennas at a site. The
physical separation needed for 30dB isolation is of the order of
one meter, but depends strongly on the horizontal beamwidth and on
the wavelength.
Here it is always assumed that co-sited RBSs have the required
30 dB antenna isolation.
Operation in the same area
Systems can be operating in the same geographical area, without
co-sited RBSs. In a worst case scenario there are no feeder losses
and the isolation depends only on the antenna gains and the
pathloss as
Isolation = GA1 + Lp GA2For worst case analysis directional
antennas with
GA1 = GA2 = 18 dBi (for outdoor RBSs only)is always assumed
here. Assuming the distance between RBSs is 100 m, the free space
propagation loss for the different frequency bands are:
800 MHzLp = 70 dB900 MHzLp = 71 dB1500 MHzLp = 76 dB1800 MHzLp =
78 dB1900 MHzLp = 78 dB2 GHz
Lp = 78 dBIndoor systems
Analysis of the co-existence environment can be extended to
include indoor coverage areas also.
In terms of co-existence, some of the factors differentiating
indoor from outdoor environments are:
Lower RBS and MS/UE output power
Lower RBS antenna gain
Shorter distance between RBS antennas
Building penetration losses
Shorter distance between RBS and MS/UE, and quite often a direct
line of sight propagation path is available
Shorter distance between indoor and outdoor RBSs, when compared
with distances between outdoor RBSs
Reduced mobility and longer call duration for MS/UE
Where indoor coverage is considered, it is assumed that:
the RBS output power is reduced
the RBS antenna gain is GA1 = GA2 = 0 dBi the building
penetration loss is 20 dB (but may only be 2 10 dB in some
cases)
Interference analysis
WCDMA is an interference-limited system. Since all radio links
interfere with each other, there is a need for power control to
balance each radio link to an acceptable level. Interfering power
introduced from other cellular systems results in decreased
sensitivity level in the WCDMA RBS.
The RBS sensitivity, in a system with noise from sources other
than thermal (i.e. interference from other cellular systems), can
be expressed as:
RBSsens = 10log(kTB) + Nf + 10log(Ruser) + Eb/Io + Pint [dB]
where
kis Boltzmans constant (1.3810-23J/K)
Tis the thermal noise temperature (290K)
Bis the receive bandwidth [Hz]
Nfis the noise figure (assume 3dB with TMA, and 4dB without)
Ruseris the user bit rate (information bits per second,
excluding retransmission)
Eb/I0is the required bit energy above interference for minimum
call quality [dB]
Pintis the received level of the external interferer [dBm]
Thus, if the external interference Pint = 0, the equation
defaults to the familiar thermal noise equation for sensitivity.
Any increase in Pint degrades the sensitivity over the thermal
noise case. This is illustrated by Table 8 below, which shows the
degradation to sensitivity versus Pint /kTBNf.
Table 8: Degradation of sensitivity versus Pint /kTBNfPint
/kTBNf [dB]Degradation of sensitivity [dB]
(200.04
(160.11
(100.41
(60.97
(31.76
0 (Pint = kTBNf)3
The maximum tolerable sensitivity degradation is set to 0.11dB.
The maximum allowable received interference level then becomes:
Pint_max = 10log(kTBNf) ( 16 [dB]
Assuming Nf = 4 [dB], 10log(kTB) = 174[dBm/Hz] yields
Pint_max = 174+ 4 16= 186[dBm/Hz] or
Maximum tolerable sensitivity degradation Pint_max =
120[dBm/3.84MHz]
This is the maximum tolerable external interference for WCDMA to
not degrade the receiver sensitivity in the RBS more than
0.11dB.
The noise floor of the unloaded RBS, i.e. the noise level in the
unloaded RBS receiver without external interferer, can be
calculated to174+ 4[dBm/Hz] = 104[dBm/3.84 MHz]
Spurious emissions
Spurious emissions are emissions on frequencies that are not
immediately outside the channel bandwidth for transmission,
measured at the base station TX reference point. Unwanted emissions
immediately outside the channel bandwidth are specified by a
spectrum emission mask and adjacent channel power ratio for the
transmitter.
Spurious emissions are caused by unwanted transmitter effects
such as:
intermodulation products caused by different frequencies used
internally in the transmitter (i.e. actual spuriouses)
intermodulation caused by carrier frequencies
harmonics that are emitted at integer multiples of the carrier
frequency (e.g. 2fc, 3fc, 4fc, etc.)
frequency conversion products which are caused by any
oscillations that are generated to produce the carrier.
All of these may cause interference to a nearby receiver.
Here spurious emissions are considered to be the dominant
contributing interference source between different mobile
communication systems. However, the occurrence of spurious
emissions may be occasional and there is a certain probability that
the WCDMA channel is not affected. Therefore the treatment of
spurious emissions in this document may be perceived as more
pessimistic than what would be found with measurements of the exact
situation.
Transmitter noise
While spurious emissions are occasional emissions outside the
carrier frequency, transmitter noise is a low level of continuous
wide band emission. Therefore transmitter noise cannot be minimised
with frequency planning, or ignored due to low probability of
occurrence. Instead, extra TX filters on the interfering system are
required. Documented noise levels from different equipment types
are hard to find since it is the worst case emissions that are
measured in type approvals.
Intermodulation products
General
Intermodulation (IM) products are created when two or more
frequencies mix in non-linear devices in the transmit path, or the
receive path. IM products of order n are the sums and differences
in n terms of the original frequencies. The strengths of the IM
products decline with higher orders. Figure8-16 is an example of
how the products decrease with higher order. If one of the terms is
weaker than the rest, the power of the IM product also
decreases.
Figure8-
SEQ Figure \* ARABIC 16 Examples of odd order IM products of two
frequencies, f1 and f2. The two frequencies, f1 and f2, are
transmitted with the power of P1 and P2 respectively.
Intermodulation products fall into three general categories,
transmitter generated, receiver generated, and resulting from
mixing in other non-linear devices.
Transmit intermodulation
Transmitter (TX) intermodulation (IM) products are created at
the transmitting RBS through the mixing of wanted carriers in the
same power amplifier, combiner, duplex filter, connectors or
antenna. TX IM may lead to interference between systems. This
requires high isolation between systems or extra filters to be
added to the interfering system. Adding filters may not be possible
if the interfering system belongs to a competing operator.
Example: WCDMA TX IM products, co-sited equipmentEvery system
has hard requirements on TX IM suppression in its own receiver
band. The requirements are set to prevent WCDMA systems belonging
to different operators to interfere with each other. The worst case
is when equipment is co-sited from two different operators, see
figure below.
Figure8-
SEQ Figure \* ARABIC 17Isolation between co-sited antennas
belonging to two operators, operator A and operator B.
The transmit intermodulation performance specified by 3GPP is
the same as the out of band emission or the spurious emission
requirements. A WCDMA RBS is allowed to transmit IM products in the
WCDMA receive band at levels < 96[dBm/100kHz] (80[dBm/3.84MHz]).
If the IM frequencies coincide with UL frequencies of the other
operator, an isolation of 80 (120) = 40 dB is required to prevent
receiver performance degradation (where the maximum tolerable
interference, Pint_max, = 120dBm). Consequently the isolation
between the TX and RX side needs to be 40dB or more.
Assuming a normal antenna isolation of 30 dB, additional filters
are needed to achieve the required 40 dB isolation. However, the
Ericsson WCDMA RBS is designed for this isolation requirement.
Receive intermodulation
Receiver (RX) IM is created in the receiver amplifiers and can
occur if, in addition to a weak wanted signal (which is close to
the sensitivity threshold), there are two strong, incoming unwanted
signals with certain separation from the wanted receive signal.
The main difference between TX IM and RX IM in terms of
co-existence is that the magnitude of co-channel interference from
TX IM is more predictable than interference from RX IM. While TX IM
is less than 45dBc (dB below the carrier), the strength of RX IM3
and IM5 increases 3 and 5 times as fast (in dB) as the received
interfering carriers creating the RX IM. Thus the strengths of RX
IM products increase rapidly with the power of the strong received
(unwanted) carriers.
RX IM is often associated with an RX IM rejection level.
Unwanted carriers above the IM rejection level may result in severe
interference while carriers below the level are harmless. For WCDMA
the (in band) RX IM rejection level is 48dBm for the RBS and 46dBm
for the UE, allowing for a degradation of 6 dB for the RBS and 3 dB
for the UE receiver sensitivity, according to the 3GPP
specifications.
Intermodulation caused by other non-linear devices
There are other sources of intermodulation that can cause
problems. In general almost any combination of dissimilar metals
with the presence of oxide can produce intermodulation. Antenna
lines, connectors, antenna mounting brackets, chain link fences,
corroded stand-by battery cables, loose or corroded AC wiring,
rusty towers, guy wires, metal doors, air conditioning vents and
many other things have been known to be sources of intermodulation
problems.
Site cleanliness and good mechanical maintenance can help
prevent this type of intermodulation. Antennas, towers, lines and
everything around a site should be properly maintained to reduce
the potential of this source to interference.Receiver blocking
The receiver blocking characteristics is the maximum level of a
non-adjacent channel interferer that can be received at the same
time as a weak input signal, without the interferer causing a
receiver sensitivity degradation of more than 6dB.
The near far problem
All transmitters have noise, spurious emissions and TX IM
products outside the carrier bandwidth. In this section these
emissions are all treated as noise. These emissions may cause
interference to a nearby receiver that is tuned to a weak signal
from a transmitter (RBS or UE) far away. The closer in frequency
the interfering carrier is to the used carrier, the more sensitive
the receiver is for interference.
The interference is a mix of out-of-band interference due to
insufficient attenuation in the receiver band pass filter, and
in-band interference from the wide band noise of the close
interfering transmitter.
WCDMA can be used as an illustration of this problem. The
principle as well as the magnitude of the problem applies equally
for many mobile communication standards.
DL interference
An example of DL interference to a subscriber of operator A is
shown in Figure8-18. The nearby signal from operator B may be 40
dBm (or even 30dBm).
Figure8-
SEQ Figure \* ARABIC 18 How the DL of operator A can be
interfered by a close RBS belonging to operator B. The high noise
level from the nearby RBS degrades the UE sensitivity.The worst
case is when operator B is using an adjacent frequency to operator
A, see Figure8-19. Interference from operator B will leak into the
UE connected to operator A due to non-ideal band pass filtering
both in the RBS and the UE. The quality of the filtering can be
expressed in Adjacent Channel Leakage power Ratio (ACLR) on the TX
side and in Adjacent Channel Selectivity (ACS) on the RX side.
Figure8-
SEQ Figure \* ARABIC 19 Adjacent WCDMA carriers with a bandwidth
of 3.84MHz and a carrier separation of 5MHz. The carriers leak into
each others TX bands due to non-ideal band-pass filters in the RBS
and UE.
ACLR is the ratio of transmitted power to the power measured in
adjacent channels. The minimum requirement for an RBS adjacent
channel offset of 5MHz is 45dB according to the 3GPP specification.
Noise will also be introduced in the UE receiver from operator
B.
ACS is a measure of the receivers ability to receive a wanted
signal at the presence of an adjacent WCDMA channel, and is given
as the receive filters attenuation on the adjacent channel(s). The
minimum requirement for ACS in the UE is 33dB according to the 3GPP
specification.The total interference contribution from both ACLR in
the RBS and ACS in the UE is called Adjacent Channel Interference
Ratio (ACIR) and is calculated as:
The ACIR for the adjacent channel interference from operator B
is 33dB, when the minimum required values for ACLR and ACS,
according to the 3GPP specification, are inserted in the equation.
The limiting factor is the receiver filter in the UE.
The interference introduced by operator B becomes 40 33 = 73dBm.
The maximum tolerable interference Pint_max, without degrading the
RBS sensitivity more than 0.11dB, is 120dBm. The interferer in this
example results in a downlink sensitivity degradation of 47dB (or
57dB for the 30dBm case).
This reduces operator As coverage and creates a dead zone around
operator Bs site. The UEs of operator A will suffer from downlink
quality problems for both idle and connected modes. Further
analysis shows that UEs of operator B also suffer from downlink
quality problems when close to operator As RBS.
The near far problem is generic and can affect significant
portions of coverage area serviced by multiple operators.
Coordinated site locations will bring mutual benefits to the
cooperating operators, by reducing the number of locations with
near far problems. Otherwise filters are needed in the TX branch of
the RBS, to increase the attenuation on the receive band.
UL interference
The same considerations for the downlink apply for the uplink.
An UE may cause interference when close to a RBS of another
operator.
The minimum ACLR requirement for an UE is 33dB, according to the
3GPP specification. The ACS requirement for the RBS receiver is to
handle adjacent channel interference of up to 52dBm. The resulting
ACIR will be 33dB for the uplink. The transmit filter in the UE is
the limiting factor for the uplink.The UL signal from the UE close
to operator B may be 50dBm (or 40dBm). The resulting RBS noise
floor for operator B is 50 33 = 83dBm (or 73dBm for the 40dBm
case). The RBS sensitivity degradation will therefore be 37dB (or
47dB for the 40dBm case).
Systems coexisting with WCDMA
WCDMA with WCDMA
Frequency bands
UL [MHz]DL [MHz]
WCDMA1920 19802110 2170
Near far problems
Coverage and capacity problems can be expected between two
totally uncoordinated WCDMA operators. In areas where uncorrelated
WCDMA systems co-exist, a UE can be exposed to high adjacent
channel interference. This occurs when the UE is far away from its
own server but close to a site of another operator. As discussed in
the example, near far problems may occur if the site positions of
the other operators are not taken into consideration when planning
the radio network. Both capacity and coverage will be affected.
The magnitude of the problem depends on the site positions,
where the worst case is when the other operators sites are placed
at the cell border of the own cells. Another important factor is
the size of the cells. Larger cells suffers more from near far
problems than small cells, which in general have smaller power
levels to the UEs and therefore a larger pool of power to combat
interference with.
The system capacity is quite sensitive to the different
operators site positions. Simulations show that the system capacity
could drop below 20% for a site to site distance of 2000m,
depending on the distance between the operators. If the sites are
co-located the capacity loss is negligible.
Solution
Probably the most effective way to solve the problem regarding
interoperator interference is to place the operators sites as close
to each other as possible. Coordination between operators is
needed, the other operators site positions have to be taken into
consideration when planning the network.
Directional antennas also offer a possibility to decrease near
far problems. The design target is to use antennas with relatively
low gain close to the sites and with high gain in the direction
where the UEs will need the most DL power, i.e. at the cell borders
or close to the other operators sites. Thus, relatively narrow beam
antennas, both in the horizontal and vertical direction, should be
used.
WCDMA with WCDMA TDD
Frequency bands
UL [MHz]DL [MHz]
WCDMA1920 19802110 2170
WCDMA TDD1900 19202010 2025
Spurious emissions
The WCDMA TDD specification places different requirements on
spurious emissions for co-sited and non-cosited cases with
WCDMA.
Co-sited equipment
Co-siting WCDMA TDD base stations with WCDMA RBSs is not
recommended due to the high requirements placed on the WCDMA RBS
design.
Operation in the same area
The maximum tolerable spurious emission level from TDD is
32[dBm/1MHz] according to the TDD specification. The emitted power
in the WCDMA receive band can be calculated to
32[dBm/1 MHz] + 10log(3.84/1) = 26[dBm/3.84MHz].
According to the interference analysis made earlier, the maximum
tolerable external interferer is 120[dBm/3.84MHz], yielding
26 (120) = 94[dB]
as the required isolation.
Required isolation between WCDMA TDD and WCDMA due to spurious
emissions from TDD, non-cositing: 94dB
The worst case is when a WCDMA network is deployed on a WCDMA
TDD network, with WCDMA with directional antennas pointing towards
TDD omni antennas.
Assuming a distance of 100m between the TDD and WCDMA sites, the
isolation between the systems (assuming 18 dBi WCDMA antenna, 20 dB
building penetration loss and 0 dB TDD antenna gain) can be
calculated to 80 dB. The additional attenuation required in the TDD
RBSs is then
94 80= 14[dB].
Filters have to be used in the TDD RBSs to accomplish this
isolation.
Spurious emissions from WCDMA into TDD receive band
The maximum tolerable spurious emission level from WCDMA is
52[dBm/1MHz] according to the FDD specification. The emitted power
in the WCDMA TDD receive band can be calculated to
52[dBm/1 MHz] + 10log(3.84/1) = 46[dBm/3.84MHz].
According to the interference analysis, the maximum tolerable
external interferer is 120[dBm/3.84MHz], yielding
46 (120) = 74[dB]
as the required isolation.
Required isolation between WCDMA and WCDMA TDD due to spurious
emissions from WCDMA, non-cositing: 74dB
The worst case is when a WCDMA TDD network is deployed in an
existing WCDMA network, with both WCDMA and WCDMA TDD sites
equipped with directional antennas, and pointing towards each
other.
Assuming a distance of 100m between the TDD and WCDMA sites, the
isolation between the systems can be calculated to 42 dB. The
additional attenuation required in the WCDMA RBSs is
74 80 = 6[dB]
Filters do not have to be used in the FDD RBSs to accomplish
this isolation.
Receiver blocking
The blocking levels of the WCDMA RBS receiver for the TDD
transmit bands, allowing for a 6 dB degradation to the receiver
sensitivity, are
40dBm for 1900 1920 MHz, and15dBm for 2010 2025 MHz.Assuming an
indoor TDD base station with 1.5 W output power, the isolation can
be calculated to
10log(1.5/110-3) (40) = 72[dB] for 1900 1920 MHz
10log(1.5/110-3) (15) = 47[dB] for 2010 2025 MHz.
Required isolation between WCDMA and WCDMA TDD due to WCDMA
receiver blocking:72dB for 1900 1920 MHz47 dB for 2010 2025 MHz
The isolation for 100m at 2 GHz is 80 dB when an 18dBi antenna
is assumed on the WCDMA RX side, with 20 dB building penetration
loss. The isolation requirements can be achieved.
The blocking level of the TDD receiver, allowing for a 6 dB
degradation to the receiver sensitivity, is 15 dBm for 2045 12750
MHz, which is part of the WCDMA transmit band. Assuming a WCDMA RBS
with 40 W output power, the isolation can be calculated to
10log(40/110-3) (15) = 61[dB].
Required isolation between WCDMA TDD and WCDMAdue to TDD
receiver blocking:61dB
The isolation for 100m at 2 GHz is 80 dB when an 18dBi antenna
is assumed on the WCDMA RX side, with 20 dB building penetration
loss. The isolation requirement can be achieved.
WCDMA with GSM
Frequency bands
UL [MHz]DL [MHz]
WCDMA1920 19802110 2170
GSM 900876 915921 960
GSM 18001710 17851805 1880
Spurious emissions
The maximum tolerable spurious emission level from GSM is
30[dBm/3MHz] peak-hold according to the GSM specification, both for
GSM 900 and 1800. The emitted power in the WCDMA receive band can
be calculated to
30[dBm/3 MHz] + 10log(3.84/3) = 29[dBm/3.84MHz].
According to the interference analysis, the maximum tolerable
external interferer is 120[dBm/3.84MHz], yielding
29 (120) = 91[dB]
as the required isolation.
Required isolation between GSM and WCDMA due to spurious
emissions from GSM:91dB
Co-sited equipment
Thus for a normal antenna isolation of 30dB, additional filters
have to be used in the GSM BTS. The filter requirement is 61 dB
attenuation in the WCDMA receive band. When an Ericsson GSM BTS
(with known characteristics) is used there might be a possibility
to decrease the filter demands, if the transmitted spurious
emission level is known to be lower than what is specified in the
standard.
Operation in the same area
The worst case is when a WCDMA network is deployed in an
existing GSM network, with both GSM and WCDMA sites equipped with
directional antennas, and pointing towards each other.
Assuming a distance of 100m between the GSM and WCDMA sites, the
isolation between the systems can be calculated to 42 dB. Hence the
required isolation between GSM and WCDMA is
29 (120) 42 = 49[dB].
Additional filters have to be used in the GSM RBSs to accomplish
this isolation.
Spurious emissions from WCDMA into GSM receive band
The spurious emission level in the GSM 900 and 1800 BTS receive
bands, caused by WCDMA RBSs is 98 [dBm/100kHz]. The emitted power
in the GSM receive band can be calculated to
98[dBm/100 kHz] + 10log(200/100) = 95[dBm/200kHz].
The GSM 900 and 1800 BTS receive sensitivity is
104[dBm/200kHz].
Assuming a C/I requirement of 9 dB, the maximum noise level
without degrading the GSM BTS sensitivity is
104 9 = 113[dBm/200kHz].
Thus the required isolation between WCDMA and GSM is
98[dBm/100 kHz] + 10log(200/100) (113) =18[dB].
Required isolation between WCDMA and GSMdue to spurious
emissions from WCDMA:18dB
This requirement can be achieved by the normal antenna isolation
of 30 dB for cositing cases, and by the pathloss for non-cositing
cases.
Receiver blocking
The blocking level of the WCDMA RBS receiver is 15dBm for 1
1900MHz, allowing for a 6 dB degradation to the receiver
sensitivity. Assuming a GSM base station with 25 W output power,
the isolation can be calculated to
10log(25/110-3) (15) = 59[dB].
Required isolation between WCDMA and GSMdue to WCDMA receiver
blocking:59dB
The isolation, when 18dBi antennas are assumed on the RBSs, for
100 m is
35 dB for GSM 900, and
42 dB for GSM 1800.The additional 24dB isolation for GSM 900,
and 17 dB for GSM 1800, can be achieved by WCDMA RBS filters on the
GSM transmit band. However, the Ericsson WCDMA RBS is designed for
these isolation requirements.
The blocking level of the GSM RBS receiver, allowing for a 3 dB
degradation to the receiver sensitivity, is
8 dBm for GSM 900, and0 dBm for GSM 1800,for the WCDMA transmit
band. Assuming a WCDMA RBS with 40 W output power, the isolation
can be calculated to
10log(40/110-3) (8) = 38[dB] for GSM 900, and
10log(40/110-3) (0) = 46[dB] for GSM 1800.
Required isolation between GSM and WCDMAdue to GSM receiver
blocking:38dB for GSM 90046 dB for GSM 1800
The isolation for 100m at 2 GHz is 42dB, when 18dBi antennas are
assumed on the RBSs. The additional 4 dB isolation for GSM 1800 can
be achieved by installing filters in the GSM RBSs, increasing the
distance or by redirecting the WCDMA antennas.
Summary
In the previous sections some examples of isolation requirements
between different type of systems have been discussed. Different
combination of systems have different requirements and in general
all cases have to be studied separately keeping in mind that
sometimes additional requirements may already be fulfilled by the
design of Ericssons radio base stations.
EN/LZT 123 6039 P1E 2
EN/LZT
_1019300394.doc
Isolation
Feeder loss 1
Antenna gain 1 Propagation loss Antenna gain 2
Extra filter
Feeder loss 2
RX
TX
_1022428444.doc
TRXB
AIUB
MCPA
TRXB
AIUB
MCPA
MCPA
Antenna system
Antenna system
20W /sector
40W /sector
_1022431367.doc
TX antennas
per sector
3 x 1
3 x 2
3 x 4
3 x 3
Output
power
40W
1
1
2
20W
20W
D
D
B
E
B
B
B
D
_1022427578.doc
RBS
TMA
TX/ RX reference point
Antenna
RBS
Antenna
RX reference point
TX reference point
_1018353560.doc
f1
f2
(2f1(f2)
P1
P2
IM3
IM3
IM5
IM5
IM7
Frequency
Power
(3f1(2f2)
_1018354120.doc
3.84 MHz
5 MHz
Carrier A
Carrier B
Power
Frequency
_1014529910.unknown
_908259872.doc
lhg
sddffd
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