WIRELESS LOCAL LOOP
CDMA Repeater Technical Characteristics
1
CDMA Repeater Technical Characteristics
1. Introduction
MNO is operating a nationwide CDMA WLL network in Asia. Operating frequencies are
450MHz and 1900MHz. We are looking for CDMA repeaters in both frequencies bands.
1.1
Introduction to CDMA Repeaters
The key to the success of wireless and mobile communication service is
to provide ideal coverage, high quality call, and service time with lowcost system and equipment. Through network planning, the base
stations are distributed in each service area to provide services to the
users. Because of the nature of the propagation of the RF signals and
blocks, there are blind areas or weak-signal areas for the RF signals.
For example, in the underground, inside a building, in streets
surrounded by high buildings, remote areas, or valleys, the call quality
deteriorates and call drops or interference happen. A repeater works as
a base station to extend the coverage and to improve the quality of the
coverage. Whether to use a base station or a repeater depends on the
estimated traffic. Under low traffic situation, repeaters can be used to
provide low-cost coverage.
ZTE
Coverage of the base station
Donor base station
Repeater
Coverage of
the repeater
Fig. 1-1 Repeaters in a Mobile Communication Network
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CDMA Repeater Technical Characteristics
Types of repeaters:
1.2

RF repeater: Directly receives the RF signals from the base
station, amplifies and transmits them. Uplink is the same as the
downlink. The characteristics are simple, affordable, widely
applicable, and easy to install. This is the most widely used type.
This type can be further divided into broadband, frequency
selection, frequency shift, and micro series.

Optical repeaters: Optical repeaters are divided into remote and
local optical repeaters. A local repeater is located at the
equipment room of the base station. The coupler (or testing
interface) in the transceiving antenna of the base station couples
the RF signals from the base station and converts them to optical
signals and sends them to the remote repeater; The remote
repeater converts the optical signals to RF signals, amplifies and
transmits them. The uplink signals undergo the same conversion
from the remote repeater and are coupled into the base station
via the local repeater. The advantages of optical repeaters are
good quality, low interference, and no isolation. Optical repeaters
are high-end application’s priorities.

Indoor distribution system: An indoor distribution system is a
small-scale RF repeater or optical repeater. An indoor distribution
system with indoor active or passive distributed antenna is
applicable to indoor coverage inside a big building.
Principles of a CDMA Repeater
Unlike a base station, a repeater does not have baseband processing
circuit and does not demodulate radio signals. It only bi-directionally
relays and amplifies radio signals. Therefore a repeater only enlarges
the coverage and improves the coverage quality but does not increase
the system capacity.
LNA
Filter
Downlink
PA
Monitoring
unit
Duplexer
Duplexer
Service
antenna
Donor antenna
Downlink RF signal
Uplink PA
Filter
LNA
Monitoring
signal
Uplink RF signal
Fig. 1-2 Block diagram of a Repeater
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CDMA Repeater Technical Characteristics
The above figure shows the block diagram of a typical RF repeater. The
left donor antenna faces the base station antenna to be forwarded to
and receives the weak downlink radio signals from the base station. The
signals pass through duplexer, Low Noise Amplifier (LNA), filter, power
amplifier, and duplexer. The signal intensity is increased and the signals
are transmitted to the blind area or weak-signal area via the service
antenna to enlarge the downlink coverage or improve the quality of the
coverage. At the same time, the right service antenna receives signals
from an MS. The signals pass through similar filter and amplifier. The
intensified signals are sent to the base station antenna via the donor
antenna. During this procedure, the repeater eliminates the path loss of
the radio signals between the base station and the repeater and in
effect provides a bi-directional transparent path between the base
station and the MS, prolonging the radio signals.
1.3
Features of CDMA Repeater
1.
Low cost
The average radio equipment utilization of a GSM local network in
China only reaches 20%. The base stations in the GSM network only
provide radio coverage. That results in some meaningless waste. It is
also true with CDMA networks. The excellent radio coverage and low
cost of a CDMA repeater enable it to meet customer demand on the
one hand and save core equipment investment on the other hand.
2.
Low configuration
In a wireless network construction, the investment in the core
equipment is only a small fraction of the total investment. The auxiliary
equipment occupies a large portion of the investment. With repeaters,
the investment is lowered not only in core equipment but also in
auxiliary equipment (such as power supply, transmission, equipment
room, and tower).
3.
Low operating and maintenance cost
A repeater is small in size, low in consumption, easy to install, and costeffective in operation and maintenance.
4.
Short construction period
Because a repeater has low requirements (or even no requirement) for
the transmission, power supply, air conditioning, and civil engineering, it
can be directly installed outdoors (or at the top of a tower), it has short
construction period. It takes only 2~3 days to survey and commission a
single repeater and less time (2 repeaters each day) to construct in
batches.
5.
Wide applicability
4
CDMA Repeater Technical Characteristics
At the preliminary stage of networking, using repeaters to substitute
some base stations can lower the investment. After capacity expansion,
the repeaters replaced with base stations are placed at remote areas. In
emergency communications, repeaters are used to provide timely
emergent coverage because of its short construction period. Where
base stations are not suitable temporarily, repeaters are used to provide
coverage; where the conditions are harsh, traffic is low, and expansion
potential is small, repeaters are used to provide permanent coverage,
as in roads, villages, and parking areas.
6.
Flexible networking
A base station can only provide circular or sector coverage; whereas a
repeater is not restricted to such coverage. Several repeaters can form
flexible coverage as required. For example, repeaters standing along a
straight line can cover miles of roads; Repeaters standing in “L” “N”, or
“M” are suitable in mountain areas.
7.
Easy migration
A repeater is small in size and easy to install, and can be moved easily
as the network changes.
1.4
Applications of CDMA Repeaters
1. Coverage of outskirts, villages and roads
The existing and potential mobile communication subscribers are
unevenly distributed in the vast expanse. There are not many
subscribers in outskirts, towns, scenic spots, villages, and railroads,
where coverage must be provided anyway. Repeaters are most suitable
where wireless coverage must be provided but capacity is not a
problem.
2. Coverage inside large buildings, underground parking lots of shopping
malls, and subways.
Repeaters feature excellent cost performance. They can be used
independently or jointly to provide most economical and easy coverage
inside large buildings, underground parking lots of shopping malls, and
subways.
3. Traffic allocation and coverage of pilot polluted areas
Under some special circumstances, the traffic between two base
stations or two sectors of a base station is extremely unbalanced, in
which case repeaters are used to allocate the traffic reasonably,
enhancing the equipment utilization in areas where traffic is small and
lowering the congestion probability in areas where traffic is high. Where
there is pilot pollution in a CDMA network, repeaters can be used to
5
CDMA Repeater Technical Characteristics
enhance the signals of a cell to make them the leading pilots,
eliminating pilot pollution and enhancing network quality.
1.5
Cautions for Repeater Application
1. Let a repeater receive clean donor signals from a donor base station
and adjust the search parameter of the adjacent base stations
accordingly.
2. Existing traffic and estimated traffic of the repeater. The traffic of the
repeater comes mostly from the donor base station. Therefore
technicians should consider the impact of the repeater coverage on the
donor base station. Repeaters are not desirable where there is large
traffic. Neither are repeaters desirable where there will be a significant
traffic increase in the near future.
3. An RF repeater can only enlarge signals of a certain frequency band
but cannot differentiate signals of the same frequency from different
base stations. Therefore RF repeaters are not desirable in urban areas
to provide outdoor coverage.
4. Geographical features of the covered area. In mountain areas with
irregular terrain, repeaters must work with base stations to provide radio
coverage.
5. Desirability of auxiliary equipment construction. Where the cost of
base station construction is high due to transmission, power supply or
housing in especially rural areas, repeaters are desirable to provide
coverage.
6. Relocation of repeaters. After the network develops and the number
of subscribers in repeater-covered areas increases, the repeaters must
be replaced by base stations and must be moved out.
To sum up, repeaters are desirable where the traffic is small and the
covered area is at the border of the network or in well-isolated areas,
such as underground parking lot, remote rural areas, and outskirts.
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CDMA Repeater Technical Characteristics
1.6
Comparison of the Applications of Three
Mainstream Repeaters
Table 1-1 Comparison of the Applications of three Mainstream Repeaters
Features
Broadband Repeaters
Optical Repeaters
Repeaters
Can
selectively
and
amplify
relay
one
or
When a base station
several
expands
frequencies and refrain
carriers,
a
working
broadband repeater can
other
relay
frequencies,
new
without
Advantages
Frequency Selection
carriers
making
any
changes.
Easy
unselected
reducing
interference.
Can ensure each carrier
to
install,
convenient,
short
construction
period,
has the same effective
power.
Easy
to
install,
taking several days to
convenient,
short
construct a broadband
construction
period,
repeater.
taking several days to
construct a broadband
repeater.
Where
Disadvantages
the
When the base station
a
expands
repeater
can cause interference.
frequency
Amplifying
repeater
useless
carriers,
selection
should
add
path modules to relay
effective power.
new carriers.
In
Frequency
multi-carrier
selection
application, the effective
increases the complexity
power of each carrier
of the equipment. Its
lowers
significantly,
price is higher than that
reducing the coverage
of a broadband repeater.
distance.
The installation should
The installation should
take into account the
take into account the
isolation of the donor
isolation of the donor
antenna from the service
antenna from the service
antenna
antenna
spontaneity
repeater.
to
The
stable
good
signals,
communication
quality.
Signals
are
coupled
to
directly
the
base
station without causing
interference.
Because
there
is
no
donor antenna, there is
no isolation requirement.
A
remote
optical
repeater can use omnidirectional
antenna
or
directional antenna.
a
signals means lowering
spontaneity
loss,
radio
environment is complex,
broadband
Low optical transmission
avoid
of
the
service
antenna uses directional
repeater.
to
The
avoid
of
the
service
Optical
fiber
repeater
to
is
the
needed,
increasing the cost. The
construction is restricted
and the installation time
is long.
Optical
repeaters
include remote and local
optical
Because
repeaters.
photoelectric
conversion
is
needed
and the equipment is
complicated, the price is
almost twice that of a RF
repeater.
antenna uses directional
antenna.
antenna.
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CDMA Repeater Technical Characteristics
Features
Broadband Repeaters
Frequency Selection
Repeaters
Optical Repeaters
No other strong radio
signals in the working
frequencies.
The donor link should
ensure no LOS.
The length of the donor
link depends on the pure
Installation
path loss from the base
conditions
station to the repeater.
The signal intensity of
the donor base station at
the
installation
site
should be greater than 80dBm.
Isolation
should
be
where
the
The donor link should
ensure no LOS.
The length of the donor
link depends on the pure
path loss from the base
station to the repeater.
The signal intensity of
the donor base station at
the
installation
site
Optical link is required.
Maximum length of the
optical fiber should not
be over 15 km
should be greater than 80dBm.
Isolation
should
be
satisfied.
satisfied.
Applicable
radio
Applicable
situation
environment
is
Widely applicable. When
good, coverage distance
used in a city, good
is small, and expansion
planning
is
optimization
needed,
such
as
indoor coverage in a city,
and
capability
Areas where there are
optical fibers.
are required.
or network border.
Requirements
A. Repeater equipment for outdoor Coverage requirement












Output power 10W with 90dB gain Vendor will provide possible options
High Gain bidirectional Outdoor Repeater systems
Operating frequency 1900MHz (1895 - 1900 / 1975 - 1980 MHz)
Operating Frequency 450MHz (453-457.300MHz/ 463-467.300MHz) and can be tuned for
any single or two carriers within 5MHz band
Exterior panel donor antenna (high gain) with a required mast and a pole.
Outdoor Repeater Coverage Antenna (Directional 30, 40, 65◦ & 90◦ subscriber side)
Low loss ready to use RF cables with connectors. Vendor provide solution with both 7/8
inch cable which has 25dB/100m loss and 1/2inch cable or any other flexible low loss
cable with less than 10dB/100m loss
Any equipment or tool for testing the installed system such as to measure VSWR, has
signal generator & spectrum analyzer features or any other suggested by vendor
Battery Bank with 24V batteries which can run 24 hour operation without any external
supply. Also voltage stabilizer as per power
Planning, Installation and testing team of the repeater system & Instruction manuals in
English.
O&M center features (If any)
Operating voltage 220V AC
Detail Technical |Specs for out door CDMA Repeater are as follow
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CDMA Repeater Technical Characteristics
Parameters
ITEM
Up-link
Down-link
1895～1910MHz
1975～1990MHz
453 ~ 457.300MHz
463 ~ 467.300MHz
5/2.5/3.75/1.25 MHz
85dB
5/2.5/3.75/1.25 MHz
90dB
27/30dBm 02dB
dB
37/40dBm 02dB
dB
Max Input Power
-30dBm
-30Bm
Delay
≤1.5μs
≤1.5μs
≤-15dBm
≤-13dBm
Frequency Range
1900MHZ
Frequency Range
450MHZ
Working BW (selectable)
Max Gain
Max Output Power
Inter-modulation
Restrain in out-band
Output Power
Adjustment Range
（Fo+BW/2）±2.5MHz≥20dBc
（Fo+BW/2）±10MHz≥60dBc
≥10dB
Gain Adjustment
Range
0~30dB
Gain Adjustment Step
1dB
Gain Variation in band
≤3dB(Maximum)
Noise Figure
≤5dB
In/Out VSWR
≤1.5
Impedance
50Ω/N-F Connector
Radiated
Spurious
Emission
In-Band
Out-band
Centralized Monitoring
Remote-Monitoring
Operating Condition
Storage Condition
Water proof of Box
Power Supply
Power
Weight
Size (L*W*H)
≤-22dBm/30kHz
≤-36dBm/100kHz @9KHz～1GHz
≤-30dBm/1MHz @1GHz～12.75GHz
Should be available
Inside remote monitoring unit (optional)
Temperature：-10℃ ~ +55℃
Relative Humidity：≤95%
Temperature：-40℃~ +80℃
Relative Humidity：≤95%
AC220V±20%, 45 ~55Hz
≤150-350W
575*440*210 / 575*440*245 mm
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CDMA Repeater Technical Characteristics
B. Repeater equipment for Indoor Coverage requirement












Out put power 1W
High Gain bidirectional indoor Repeater systems
Operating frequency 1900MHz (1895 - 1900 / 1975 - 1980 MHz)
Operating frequency 450MHz (453 ~ 457.300/ 463 ~ 467.300MHz)
Exterior Panel Donor Antenna (high gain) with a required mast
Ceiling Mounted/wall mounted indoor Antenna
low loss RF cables with connectors
Any equipment or tool for testing the installed system.
Installation & testing team for repeater system
Instruction manuals in English.
O&M features (If any)
Operating voltage AC 220 (50Hz)
Solution providers who can only offer indoor or out door, they can also give trial for only
one solution
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