coverage planning course
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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Coverage Planning Principle
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Contents
1. Planning Basis
2. Coverage Planning
3. Advance Planning
4. Advance Technology for improving coverage
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Radio Propagation Environment
Multi-path propagation
Shadowing
Terrain
Building
Reflection
Interference
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Reflections
direct signalstrong reflected signal
equalizer window 16 s
amplitude
delay time
long echoes, out of equalizer window:self-interference
Strong echoes can cause excessive transmission delay
No impact If the delay falls in the equalizer window
Cause self-interference if the delay falls out of the equalizer window
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Fading
Slow fading (Lognormal Fading)
Shadowing due to large obstacles on propagation direction
Fast fading (Rayleigh fading)
Serious interference from multi-path signals
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Fading
time
power
2 sec 4 sec 6 sec
+20 dB
meanvalue
- 20 dB
lognormalfading
Rayleighfading
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Objective of Propagation Model
The propagation model is used to estimate the path loss
during radio wave propagation caused by the terrain and
artificial environments
The propagation model is the foundation of the coverage
planning. A good model mean more precise planning.
The propagation model depends on the working frequency
of the system. Different propagation models have different
working frequencies ranges. Moreover, indoor propagation
model differs from the out door propagation model
Through surveying radio propagation environments, you can get familiar with the
overall landforms, estimate the rough antenna height, and select the proper radio
propagation model, among which the radio propagation model helps you estimate
the number of base station when predicting the coverage. If necessary, you must
adjust the propagation model.
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Page9Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Planning Basis
2. Coverage Planning
3. Advance Planning
4. Advance Technology for improving coverage
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Cell Coverage Range
Achievable cell coverage depend on
Frequency band (450, 900, 1800 MHz)
Surroundings and environment
Antenna type
Antenna direction
Minimum required signal level
Difference band coverage area will be difference. Normally
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Min. Receiving Level
On Down Link
On Uplink
npenetratioinm
inminmmsreceive
LFastFading
ngSlowlyFadiISMin
++
++=
arg
argarg
npenetratioinminminmbtsreceive LFastFadingngSlowlyFadiISMin ++++= argargarg
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Page12Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Fading
Slow fading (Lognormal Fading)
Shadowing due to large obstacles on propagation direction
Fast fading (Rayleigh fading)
Serious interference from multi-path signals
+10
0
-10
-20
-300 1 2 3 4 5 m
Level (dB)
920 MHzv = 20 km/h
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Page13Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Fading
time
power
2 sec 4 sec 6 sec
+20 dB
meanvalue
- 20 dB
lognormalfading
Rayleighfading
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Page14Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Min. Receive Level
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=5dBInterference margin=4dB
? dBmOutdoor
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=5dB
Interference margin=4dB
Penetration Loss=10
? dBmResident area, indoor
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=7dB
Interference margin=4dB
Penetration Loss=18
? dBmDensity urban, indoor
GivenMin. Receiving LevelApplication Environment
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Page15Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Min. Receive Level
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=5dBInterference margin=4dB
-90dBmOutdoor
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=5dB
Interference margin=4dB
Penetration Loss=10
-80dBmResident area, indoor
Sms=-102dBm
Fast Fading Margin=3dB
Slowly Fading Margin=7dB
Interference margin=4dB
Penetration Loss=18
-70dBmDensity urban, indoor
GivenMin. Receiving LevelApplication Environment
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Page16Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Link Budget
receivemsbtscablecombinerbts MinGLGLLP ++
receivecablebtsdiversitymsmsMinLGGLGP +++
GSM has two frequency bands: 900 MHz and 1800 MHz. Each band has
different transmission characteristics. Long wavelength comes with little diffraction
loss and short wavelength comes with little building penetration loss. Indoor wave
component is the superimposition of penetration component and diffraction
component. Diffraction component constitutes most of the wave component, and
therefore, the indoor and outdoor level difference of 1800 MHz is greater than that
of 900 MHz. Because of the issues such as complex transmission environment and
the direction of incident waves, quantify indoor and outdoor level difference is not
very practical. The best way is to carry out level difference test in special
environment for planning optimization.
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Page17Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Link Budget Model
receivemsbtscablecombinerbts MinGLGLLP ++
receivecablebtsdiversitymsmsMinLGGLGP +++
On downlink
On uplink
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Page18Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Equipment-related Parameters BTS Tx power
Maximum BS Tx power. Maximum power of the antennaPtrx-Lcdu
Maximum MS Tx power
900:2W
1800:1W
BS antenna gain
Typical value: Omni directional antenna: 11dBi or 13dBi;
directional antenna: 15 to 18dBi.
MS antenna gain
Generally, MS antenna and the connection loss areconsidered to be 0dB.
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Page19Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Equipment-related Parameters
BTS receiver sensitivity -112.5dBm
The sensitivity is also related with vendor and environment
MS receiver sensitivity
-102dBm
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Page20Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
No Combining
TCOM
TRX0TRX0
TX
TRX1TRX1
TX
TX1
IN1
IN2
TX2
RXM1
RXD1
RXM2
RXD2
combinercombiner
For the cell which just has one or two TRX, the TRX will not be connected to the
combiner and directly connected to DDPU (Dual Duplexer Unit for DTRU BTS). So it is
combiner loss will be 0---1 dB.
The DDPU is for sending multi RF signals from the transceiver in the DTRU to the antenna
through the duplexer
Sending signals from the antenna after amplifying and quartering them to the transceiver in
the DTRU
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Page21Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Wide Band Combining
TRX0TRX0
TX
TRX1TRX1
TX
TX1
IN1
TCOM
IN2
TX2
combinercombiner
If for the cell which has more than two TRX, TRX0 and TRX1 will be connected to
the combiner first and then connected to DDPU. It s combiner
loss will be 3.3+1=4.3dB
The DDPU is intermixed with the DCOM (Combining Unit for DTRU BTS in the
DAFU subrack of the forepart of RF subsystem. It is indispensable. Generally, the number
of DDPU is one at least and three at most. Without the DCOM, there can be at most six
DDPUs
Sending multi RF signals from the transceiver in the DTRU to the antenna through the
duplexer
Sending signals from the antenna after amplifying and quartering them to the transceiver in
the DTRU
The DCOM is optional and there are a maximum three DCOMs. The DTRU
combines two carriers into one channel. The DCOM is required when the DTRUs
are insufficent
The DCOM combines the 2-route DTRU transmission signals and outputs them to
the DDPU
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Page22Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Feeder and Jumper
feederconnector
Feeder
Antenna Adjustable Support
GSM/CDMA
Panel Antenna
BTS
Wall
jumper
In a wireless telecommunication system, the antenna provides the interface between base
transceiver station (BTS) and outside propagation mediums. One set of antenna can both
radiate and receive radio waves. When radiating radio waves, it converts high frequency
current into electromagnetic wave; when receiving radio waves, it converts the
electromagnetic wave into high frequency current.
During network planning, the right antenna is selected according to the radio environment
of the BTS. The parameters, such as antenna height, antenna azimuth angle, tilt angle, are
decided based on the selected antenna.
Antenna is directly related to uplink and downlink converges, so are the radio frequency
(RF) components, such as feeder cable, combiner, and duplexer.
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Page23Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Antenna Feeder SystemFeeder
Feeder:
Frequently-used specification:
7/8 ", 5/4 "
The curvature of the feeders shall not be
too large, and the conductor surface is
required to well connected with the ground
80 meters
900MHZ
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Page24Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Coverage Probability
area coverage probability: Within a coverage area, the percentage
of area in which receive signal strength (RxLev) is always higher than
RxLev threshold
edge coverage probability: In coverage board area, the percentage
time when the receive signal strength (RxLev) is always larger than
the of RxLev threshold
Sometimes during the planning, coverage probability also have to consider. And for
high coverage probability, high shadow fading margin reserved. Normally, there are
two types coverage probabilities: area coverage probability and edge coverage
probability.
According to the standard deviation of the shadow fading and the requirements for
the border coverage probability (determined by the operator), we can calculate the
edge coverage probability by formula.
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Page26Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Margin
To ensure a certain edge coverage probability , it is
necessary to reserve some power margin, i.e. the shadow
fading margin.
Due to the shadow fading, the actual path loss fluctuates
around this value. It is subjected to the logarithmic normal
distribution as the location and time varies.
Note : the 75% edge coverage probability is corresponding to the 90% area
coverage probability.
Concept of communication probability: Success call rate of MS on the
radio coverage border or in the cell
Category of communication probability: location probability and time
probability
In general, the time change has little impact on the communication
probability, so it can be neglected.
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Page27Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Area coverage probability to expected
shadow fading margin
50% 60% 75% 80% 90% 92% 93% 95% 97% 98% 99% 100%
Dense Urban -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3
Urban -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3
SubUrban -6.7 -4.2 -0.1 1.4 5.5 6.5 7.2 8.6 10.7 12.2 14.6 21.3
Rural Area -6.6 -4.3 -0.6 0.8 4.3 5.4 5.9 7.2 9.1 10.4 12.3 19.2
High Way -6.1 -4.4 -1.8 0 1.4 2 2.4 3.2 4.3 5.1 6.5 10.4
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Page28Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Min. Receiving Level
On Down Link
On Uplink
marginfadingshadowarg
argarg
+++
++=
npenetratioinm
inminmmsreceive
LFastFading
ngSlowlyFadiISMin
marginfadingshadow
argargarg
++
+++=
npenetratio
inminminmbtsreceive
L
FastFadingngSlowlyFadiISMin
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Page29Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Example
30MS max. transmitting power(dBm)
-102MS sensitivity (dBm)
?Effective Radiated Power EIRP(dBm)
17BTS antenna gain (dBi)
?BTS combiner, jumper, feeder and connectorloss (dB)
0.5feeder connector loss (dB)
11dB/100m51/2 jumper length (m)
4dB/100m457/8 feeder length (m)
1BTS combiner loss (dB)
46BTS max. transmitting power (dBm)
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Page30Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Example
?dBexpected shadow fading margin (dB)
2Noise correction (dB) (interference margin)
2dBclutter loss (dB) (slow fading margin)
1dBFast fading margin
1dBMS antenna gain
?allowed DL Max Propagation loss in Um interface(dB)
4Body loss (penetration loss)
91%corresponding edge coverage probability
97%expected area coverage probability
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Page31Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Site Coverage Radius: R
Site distance: D=1.5RCoverage Area=1.949R2
Site Coverage Radius: R
Site distance: D=1.732RCoverage Area=2.598R2
3 Sectors site Omni site
Distance and Coverage Area
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Page32Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Example
?Expected BTS number
?Cell dimenstionkm2
0.80Cell radiuskm
OmniSite type
500Expected coverage area
dimensionkm2
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Page33Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Link Balance Tool
link balance
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Page34Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Planning Basis
2. Coverage Planning
3. Advance Planning
4. Advance Technology for improving coverage
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Page35Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Why Indoors
Indoor coverage become the main competition between operators
Subscribers expect continuous coverage and better quality
Outdoor cell cant provide sufficient indoor coverage
INDOOR SOLUTION
GoodQuality!
With the rapid development of economy, hotels, commercial centers, large-
scale flats, underground railways, and underground parking areas are arising
by batch. As a result, mobile stations are more frequently used in indoor
environment. Thus, they require better indoor mobile communication services.
Generally, the following problems are present in indoor mobile
communication systems:
From the perspective of coverage, the complex indoor structure and the
shielding and absorbing effect of the buildings cause great radio wave
transmission loss. As a result, the signals in some areas may be weak,
especially the signals in the first and second floors in the underground are
quite weak, or even there are dead zones. In this case, mobile stations cannot
necessarily access the network, there is no paging response, or subscribers are
not in service areas.
From the perspective of network quality, the factors interfering radio
frequencies are probably present in upper floors of high buildings. In this case,
the signals in service areas are not stable, so ping pong effect may occur and
conversation quality cannot be ensured.
From the perspective of network capacity, if mobile stations are frequently
used in buildings, such as large-scale shopping centers, conference halls,
some areas in the network cannot meet the requirements of subscribers. In
this case, congestion may occur on radio channels.PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com
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Page36Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Building Penetration Loss
rear side :-18 ...-30 dB
Pref = 0 dB
Pindoor = -3 ...-15 dB
Pindoor = -7 ...-18 dB
-15 ...-25 dB no coverage
signal level increases with floornumber :~1.5 dB/floor (for 1st..10th floor)
Signal level in building is estimated by using a building penetration loss
margin
Big differences between rooms with window and without window(10~15 dB)
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Page37Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Building Penetration Loss
Signal loss for penetration varies betweendifferent building materials, e.g.:
mean value
reinforced concrete wall, windows 17 dB
concrete wall, no windows 30 dB
concrete wall within building 10 dB
brick wall 9 dB
armed glass 8 dB
wood or plaster wall 6 dB
window glass 2 dB
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Page38Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Indoor Coverage Solutions
Small BTS
Mini BTS
Repeater
Active
Passive
Optical
Antennas
Distribute antenna
Leaky cable
Signal distribution
Power splitter
Optical fiber
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Page39Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Indoor Planning
Example2:1.2 MHz allocation
50 mErl/subscriber , GOS=2%reuse per two floor, separatefrequencies within one floor:a) three floors
52.12 Erl => 842subs
b) ten floors140 Erl => 2808 subs
Example1:1.2 MHz allocation
50 mErl/subscriber, GOS=2%no frequency reuse:
a) three floors
34.68 Erl=> 694 subscribers
b) ten floors34.68 Erl => 694 subscribers
Single cell approach Multi-Cell approach
t
f5
f6
f5
f1
f2
f1
f3
f4
f3f1..f6
f1..f6
f1..f6
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Page40Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Indoor Coverage Examples
With Repeater
Relay outdoor signal into target building
Need donor cell, add coverage but not capacity
With indoor BTS and distributed antenna
Heavy loss bring by power splitting and cable
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
1:1:1
1:1
4th floor
3rd floor
2nd floor
1st floor
ground floor
Outdoor Antenna
Gain: 18 dBi
Indoor Antenna
Gain: 9dBi
Target Indoor Coverage Building
7/8'' Cable
Loss: 4dB / 50m
Cable length : 25m
-50 dBm
4th Floor
3rd Floor
1st Floor
Ground Floor
2nd Floor
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Page41Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Repeater Application examples
Coverage for low traffic area Remote valley
Tunnel
Underground coverage
needs
decoupling > amplification
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Page42Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Wave Propagation in Tunnels
The tunnel types include railway tunnel (or metro tunnel), highway
tunnel.
Highway tunnel is wide, select the antennas with a larger size to
obtain a higher gain, coverage distance is larger.
Railway tunnel is narrow, the antenna size and gain are greatly
restricted. Especially the radio propagation is greatly affected by
passing train.
The tunnel types include railway tunnel, highroad tunnel, and underground
railway tunnel. Each tunnel has its characteristics, and they are specified as
follows.
For the highroad tunnel, it is wide. The coverage in the highroad tunnels is
relatively stable. When there are vehicles passing by, you can select the
antennas with a larger size to obtain a higher gain, so the coverage distance is
larger.
For the railway tunnel, it is narrow, especially when there is a train passing
by; only a little room is left in the tunnel, so the radio propagation is greatly
affected. Moreover, the train has great effect on radio signals. Since the
antenna installation room is quite limited, the antenna size and gain are
greatly restricted. In addition, because general cars cannot be driven to such
tunnels, the tunnel coverage is hard to be tested. Therefore, the planning forhighroad coverage is different from that of the railway coverage.
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Page43Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Short and Middle Tunnels Coverage
Generally, the tunnels shorter than 100m are defined as short
tunnels. l the antenna can be installed at the tunnel entrance so as
to ensure coverage.
For the tunnels shorter than 500m, can use the combination of a
micro base station and a single antenna (or a repeater) for the
tunnel coverage, and install the antenna in the middle of the
tunnel.
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Page44Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Long Tunnels Coverage
For the tunnels longer than 500m, you need to use the distributed
antenna system or the leaky cable for the coverage.
For the coverage of still longer tunnels, use amplifiers to amplify
signals. That is, you can use either the distributed antenna system
or the leaky cable for the coverage solution. In terms of technical
indexes and installation space, coverage solution based on leaky
cable is recommended.
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Page45Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Tunnels Coverage
If outside tunnel and within the tunnel belong to the difference cell,
handover problem will occur. To solve this problem, can consider
adopting the following methods:
Adopt the bi-directional antenna for the tunnel coverage, because
it can provide enough overlapping area for handover.
Enable special handover algorithms, such as fast level fall
handover algorithm. In this case, a mobile station can hand over
to another cell when the signal level falls fast.
Select the directional antenna with small front-to-back ratio.
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Page46Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Planning Basis
2. Coverage Planning
3. Advance Planning
4. Advance Technology for improving
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Page47Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Transmitting diversity
TDMA
Frame
Delayed
TDMAFrame
TDMAFrame
1~2 Symbols
TRXB
TRXA
Two transciver transmit the same information by the same output power as
single TRX in the different time, the MS equalizer can combine the two
signal just like deal with the multipath signal.
The two downlink path transmitter signal have some time delay even if we use double
polarization antenna, the MS also can combined the two signal in the equalizer.
Improve the downlink BCCH TRX downlink performance
Improve the downlink TCH TRX downlink performance in RF hopping or No RF hopping
Especial for stationary and slowly moving MS
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Page48Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Two TRXs transmit the same signal with 7.4us time
delay.
Improving downlink coverage based on mutualexchange theory.
Generally 3dB downlink gain from transmittingdiversity.
Transmitting diversity
TRXA
TRXB
Two TRX transmit the same signal with 7.4us delay between. Generally 3dB downlink gain
out of transmitting diversity
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Page49Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Transmitting diversity
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Page50Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
PBT(Power Booster Technology)
Adopt the in-phase synthesizing technology. Generally PBT can generate 2dB downlink gain.
PA
RF
PA
Synthesizer
DUPLEX
RF
BB
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Page51Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Dynamic PBT
This technology is based on timeslots, allows a calling subscriber
to use a timeslot in other TRX.
When the receive level is lower , channels corresponding to
identical timeslots in adjacent carriers stop delivering services
temporarily.
At this time, the RF channel in the service timeslot and the
auxiliary channel in the adjacent carrier transmit identical signals,
whose phase is also the same. The combined signals are stronger,
thus improving the receiving quality for the subscriber.
This technology is based on timeslots, allows a calling subscriber to use a timeslot in
other TRX. A measuring report is used to monitor this subscriber s downlink receive
level. When the receive level is lower than the preset threshold, Channels
corresponding to identical timeslots in adjacent carriers stop delivering services
temporarily. The related RF channel provides PBT as an auxiliary channel. At this
time, the RF channel in the service timeslot and the auxiliary channel in the adjacent
carrier transmit identical signals, whose phase is also the same. The combined signals
are stronger, thus improving the receiving quality for the subscriber.
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Page52Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
PBT(Power Booster Technology)
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Page53Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
4-way receiving diversity
Compared with 2-way receiving diversity, 4-way
receiving diversity gets more 3~5dB uplink gain.
RF1
RF2
RF3
RF4
BB
>120%R
2WRD
4WRD
R
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Page54Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
TCH/AHS4.75
TCH/AHS5.15
TCH/AHS5.9
TCH/AHS6.7
TCH/AHS7.4
TCH/AHS7.95
AMR-HR
Experiment 1b - Test Results
1.0
2.0
3.0
4.0
5.0
Conditions
M OS
Sel. Requir.
AMR-HR
EFR
FR
HR
Sel. Requir. 3.99 3.99 3.99 3.14 2.74 1.50
AMR-HR 4.11 4.04 3.96 3.72 3.38 3.10 2.00
EFR 4.21 4.21 3.74 3.34 1.58
FR 3.50 3.50 3.14 2.74 1.50
HR 3.35 3.24 2.80 1.92
No Errors C/I=19 dB C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB
AMR
High voice quality than HR and good customer experience.
Low C/I requirement and easy to network planning.
More robust than HR and stronger anti-interference.
Increase 80%~140% network capacity and decrease CAPEX of network.
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Page55Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Gain of Advance Technology
3~5dB(uplink)4-way receiving diversity
5dB(when EFR lower than
5%,compare with FR)
AMR
2dBPBT
3dBTransmitting diversity
Gain
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Page56Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
The Function of Extended Cell
In the GSM specifications, the cell coverage is restricted within 35km(63
TA) . Thus, the coverage radius of the cell cannot exceed 35km. In wide
and open area where the subscribers are dispersedly distributed, the
traffic is low, and the infrastructure such as transmission and power
supply facilities is hard to construct or cannot reach, the cell with a radius
larger than 35km must be provided.
If the extended cell technology is adopted, the cell coverage radius can
reach 120km in an ideal condition. Operators can adopt this technology to
reduce the number of sites and build their own GSM networks quickly
with smaller investment. In this way, they can attract mobile subscribers
in special areas and thus increase the operation revenue.
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Page57Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Transmission delay t
Transmission delay t
TA
The mobile phone should
send the signal in advance!!
Timing Advance (TA)
Transmission delay is unavoidable in the radio interface. If the mobile station
moves away from the base station during a call, the further distance the more delay.
The uplink is as the same.
If the delay is too high, the timeslots of the signal from a certain mobile station
and that of the next signal from another mobile station received by the base stationwill overlap each other, thus causing inter-code interference. To avoid this, during a
call, the measurement report sent from the mobile station to the base station carries a
delay value. Moreover, the base station should monitor the time when the call arrives
and send an instruction to the mobile station via the downlink channel every 480ms
so as to inform the mobile station the time of advance transmission. This time is the
TA (timing advance), which ranges between 0~63 (0~233s ). The TA value is
limited by the timing advance code 0~63bit of the GSM system. Therefore, the
maximum coverage distance of the GSM is 35km. Its calculation is as follows:
1/2*3.7 s /bit*63bit*c=35km
{In the formula, 3.7s /bit is the duration per bit (156/577); 63bit is the
maximum bit number of the time adjustment; c is the light speed (transmission speed
of the signal); and indicates that the go and return trip of the signal.}
According to the above description, the distance corresponding to 1bit period is
554m. Influenced by the multi-path propagation and MS synchronization precision,
the TA error may reach up to about 3bit (1.6km).
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Page58Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Dual Timeslot Extended Cell
Delay63
Modulation range
Normal cell
Dual timeslot extended cell
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Page59Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Dual Timeslot Extended Cell
To support MS signals with a delay exceeding 63bit, the 2-
timeslot cell can bind the even and odd timeslots, as if a
TDMA frame in the extended cell only has four channels:
0/1, 2/3, 4/5, and 6/7. Only channel 0, 2, 4, and 6 can be
assigned for the MS.
B0 B2 B3B1 B4 B5 B6 B7
0/1 2/3 4/5 6/7
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Page60Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Dual Timeslot Extended Cell
The dual-timeslot function is based on the concentric cell. The carrier in
the underlay cell is configured as the 2-timeslot carrier. The carrier on the
overlay cell is configured as a common cell. When the cell is configured
as a 2-timeslot cell, the concentric cell attribute of this cell is automatically
set to the concentric cell.
If all carriers in the cell must be configured as 2-timeslot carrier, such
solution is called the cell-level 2-timeslot solution. In this case, all carriers
are configured in the overlay cell.
If some carriers in the cell are configured as common carriers and others
as 2-timeslot carriers, the BCCH is located on the 2-timeslot carriers,
such solution is called carrier-level 2-timeslot solution. In this case, the 2-
timeslot carriers are configured in the underlaid cell and the common
carriers are configured in the overlaid cell.
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Page61Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Question
What is the max value of extended cells TA?
Max TA?Max TA?
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Page62Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Assignment of Extended Cell
UnderlaidIn-coming BSC HO
UnderlaidIntra-BSC HO
Depend on assign optimum layerAssignment
UnderlaidImm-assignment
Assignment StrategyType
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Page63Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Configuration
Modify the cell as double timeslot extended cell.
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Page64Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Configuration
Configure the TRX as overlaid or underlaid.
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Summary
In this course, we have learned:
Propagation and planning basis
Coverage planning method
Indoor and tunnel planning
Planning procedure and site location