new_1x_description of link budget paramet
TRANSCRIPT
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2004. Feb.
ED 04
System Lab. 2 (Wireless)
Description of
Link Budget Parameter
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Description of Link Budget Parameters 2004-02-27
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CONTENTS
1. OVERVIEW....................................................................................................................................... 2
2. PARAMETERS ................................................................................................................................. 22.1 Forward link ...................................................................................................................................................22.2 Reverse link .....................................................................................................................................................8
3. EXAMPLES OF LINK BUDGETS................................................................................................... 113.1 1X Forward link Voice .................................................................................................................................113.2 1X Forward link data...................................................................................................................................113.3 1X Reverse link voice ...................................................................................................................................123.4 1X Reverse link data.....................................................................................................................................12
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1. Overview
The link budget is to estimate the maximum cell range satisfying required Eb/No which is related to the some
quality (FER) target. In the link budget some factors such as the antenna gains, cable losses, diversity gains,
fading margins, and etc., are taken into account. The output of the link budget calculation is the MAPL
(Maximum Allowed Propagation Path Loss) i.e., the maximum tolerable mean path loss in the link.
2. Parameters
2.1 Forward link
Test environment
In the link budget the three test environments, indoor, outdoor and vehicle, are considered for both voice and
data service. For those environments two channel models, Pedestrian B (Ped-B) and Vehicular B (Veh-B),
recommended by ITU-R M. 1225 are used for indoor/outdoor and vehicle environments, respectively.
Traffic channel fraction of total power, Ec/Ior(dB)
Ec/Ior is the ratio of the traffic channel energy per chip on a given channel relative to the total transmitted
power spectral density at the Base station (BS). Note that it is also the fraction of the power allocated to the
channel from the total BS transmitted power used. It is often utilized in down link performance requirements. In
Samsung link budget table the simulation results by CDG (CDMA Development Group) evolution study report
and by Samsung are used for voice and data service, respectively.
(1) Voice service
Figure 1 and 2 show Ec/Ior for voice channel according to the geometry in CDMA2000 1X and they are
adopted from CDG evolution study report. Ped-B and Veh-B environment are shown in Figure 1 and 2,
respectively. In Samsung link budget, the Ec/Ior value at geometry 0 dB represents the cell edge condition with
0 dB soft handoff (SHO) imbalance is chosen.
(2) Data service
CDMA2000 1X Samsung simulation results in Ped-2 path, turbo code environment at geometry 4 dB for Ped-B,
and geometry 0 dB for Veh-B with respect to the 153.6 kbps data rate are shown in Figure 3 and 4, where 5%
target FER is given.
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cdma2000 1X , Ped - B, no - TD, RC3 (R 1/4)
- 20
- 18
- 16
- 14
- 12
- 10
- 8- 6
- 4
- 2
0
- 6 - 3 0 3 6 9 12
Geometry [ dB]
Ec/ordB]
0 dB SHO Imbalance
3 dB SHO Imbalance
6 dB SHO Imbalance
No SHO
F igure 1. CDMA2000 1X, Ped-B, no-TD , RC3, voice channel Ec/I or according to geometry.
cdma2000 1X , Veh - B, no - TD, RC3 (R 1/4)
- 20
- 18
- 16
- 14
- 12
- 10
- 8
- 6
- 4
- 2
0
- 6 - 3 0 3 6 9 12
Geo metry [ dB]
Ec/ordB]
0 dB SHO Imbalance
3 dB SHO Imbalance
6 dB SHO ImbalanceNo SHO
F igure 2. CDMA 2000 1X, Veh-B, no-TD , RC3, voice channel Ec/I or according to geometry.
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cdma2000 1X , Ped - B, no - TD, RC3 (153.6 kbps)
- 12
- 10
- 8
- 6
- 4
- 2
0
2 4 6 8 10 12
Geometry [ dB]
Ec/ordB]
F igure 3. CDMA2000 1X, Ped-B, tur bo code, Samsung simu lation resul t.
cdma2000 1X , Ved - B, no - TD, RC3 (153.6 kbps)
- 14
- 12
- 10
- 8
- 6
- 4
- 2
0
0 2 4 6 8 10 12
Geometry [ dB]
Ec/ordB]
F igure 4. CDMA2000 1X, Veh-B, turbo code, Samsung simu lation resul t.
BS maximum transmitter power per traffic channel (dBm) is calculated from traffic channel fraction
(Ec/Ior) of total power and BS maximum transmitter power, 43 dBm.
Cable, connector and combiner losses (dB) are the combined losses of all transmission system components
between the transmitter output and the antenna input. Note that all losses in positive dB values in link budget
table. A typical value is 3 dB.
BS transmitter antenna gain (dBi) is the maximum gain for the transmitter antenna in the horizontal plane.It is specified as dB relative to an isotropic radiator.
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BS transmitter EIRP per traffic channel (dBm) is the effective transmitting power in traffic channel. It is
calculated by the summation of BS maximum transmitter power per traffic channel (dBm), transmission
system losses (-dB), and the transmitter antenna gain (dBi).
MS receiver gain (including body loss etc.) (dBi) is the total gain affected by the MS receiver antenna gain
(dBi), receiver system loss (-dB) and body loss (-dB). The typical values of receiver system and body lossesare 0 dB and 3 dB, respectively.
Thermal Noise Density (dBm/Hz) is the noise density generated by thermal agitation of electrons in a
conductor. It can be calculated by the following equation, N=KTW/Hz, where, K is Boltzman constant (-
228.6 dBW/KHz) and T is the absolute temperature. Therefore, it is the function of temperature, T and
bandwidth, W.At the room temperatureN = -174 dBm/Hz
Receiver Noise Figure(dB) is represented by the ratio, usually expressed in dB, of the thermal noise power
at the output to that at the input. 8 dB is a typical value for commercial mobile system (MS). .
Total effective noise + interference density [dBm/Hz] is the effective noise. It is estimated by simulation.
In simulation, 2-tier hexagonal cell structure is used to evaluate, and the following geometries are used for
cell edge condition.
Service Type Ped-B Veh-B
Voice Geometry 0 dB Geometry 0 dB
Data Geometry 4 dB Geometry 0 dB
Information Rate (Bit rate) (dB-Hz) is the channel bit rate, and is the dB scale of bit rate.
Required Eb/(No+Io) (dB) is the ratio of the required energy per bit to interference power spectral density
for satisfying the proper target FER, 1% for voice and 5% for data service. These parameters are obtained by
long-term link level simulation using given FER condition.
Receiver Sensitivity (dBm) is the required minimum received signal power at receiver without margin and
gain.
Handoff Gain (dB) is the effective gain due to the duration of the transmitter signal at receiver. The gain is
dependent on the standard deviation of the individual fading processes of the two paths and the relative
correlation between the two paths. Therefore, the handoff gain increases as the standard deviations of the
fading processes increase. Handoff gain is estimated by analytical method1.
Penetration Loss (dB) is the required margin to overcome another losses due to the car and the building.
a. Indoor penetration loss
It is associated with the degradation of the RF signal caused by a building structure. Variations result
from construction material, building layout, user location inside the building and direction from base
1 For a detailed discussion of handoff gain, please see: A. J. Viterbi, A. M Viterbi, K. S. Gilhousen, E. Zehavi, Soft Handoff Extends
CDMA Cell Coverage and Increased Reverse Link Capacity, IEEE J. Select. Areas Comm., Vol. 12, No. 8, Oct. 1994, p.1281-1288.
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station.
b. Outdoor penetration loss
No penetration loss is applied on outdoor environment.
c. Vehicle penetration loss
It is the degradation of the RF signal caused by an enclosure of vehicle.
Log-normal Fade Margin (dB) is defined at the cell boundary for isolated cells. This is the margin
required to provide the specified coverage availability over the individual cells. In Samsung link budget the
log-normal fade margin with 95% area coverage and 9 dB shadowing standard deviation is applied. Note
that 95% area coverage probability can be regarded as 87.3 % cell edge coverage probability, alternatively.
Figure 5 shows the log-normal fade margin with 9 dB standard deviation to the coverage probability at the
cell edge.
Cell-Edge Coverage (or Small Area Coverage)
PDF of
=
2
2
2
)(exp
2
1)(
xxxp
Coverage = 1 outage
[ ]
=
==
22
1
2
1
)()(
0
00
0
xxerf
dxxpxxPRPx
x
Fade Margin = xx 0
where,
: Received signal strength (log-normal distribution) [dBm]
x : Mean of Log-normal distribution v(median value) [dBm]
0x : Receiver threshold [dBm]
: Shadowing log normal standard deviation
[Note] Coverage: fraction of the locations at r = R wherein a mobile would experience a received
signal above threshold.
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0
5
10
15
20
25
0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1
coverage probability at cell edge
Log-normalfadingmarg
in(dB)
F igure 5. Log-normal fading margin(dB) according to coverage probabil ity at cell edge(std.= 9 dB)
Maximum Allowable Path Loss (dB) is the maximum tolerable mean path loss in the link. In other words,
this is the largest value that the mean path loss can achieve such that the mobile and base station will still
have enough power to close the link. The path loss is specified as a mean path loss since most propagation
prediction algorithms do not consider the effects of slow fading and therefore generate mean predictions.
The maximum allowable path loss is calculated with receiver sensitivity, i.e., minimum received signalpower, and maximum transmitted EIRP.
Cell Radius (km) is the cell coverage. Cell coverage can be defined to the region satisfying minimum
received signal level and signal quality required to obtain the performances of optimal system. In other
words, cell coverage can be defined as the range of distance separation between base station and mobile in a
certain location where the received signal exceeds minimum received signal level. This distance is
determined by using maximum allowable path loss and propagation model. In Samsung link budget a
Modified HATA model is applied to estimate cell radius. As an example, Path loss to the distance evaluation
using Modified HATA model is drawn in Figure 6.
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Mo di f ied Hata M o de l at 889 MHz / U rban
0
20
40
60
80
100
120
140
160
180
0 1 2 3 4 5
Distanc e [ km]
PathlossdB]
F igure 6. Path loss vs. distance at 889 MHz when Modif ied HATA model is appli ed for propagation model
2.2 Reverse link
Test environment
RF test environments are same as those in the forward link. Details are described in Section 2.1 for forward
link.
MS maximum power per traffic channel (dBm) is the maximum transmitting power per traffic channel
by MS. It depends on type of mobile. A typical value is about 23 dBm.
MS antenna gain (including body loss, etc.) (dBi) is the total gain affected by the MS receiver antenna
gain (dBi), receiver system loss (-dB) and body loss (-dB). A typical value of receiver system and body
losses are 0 dB and 3 dB, respectively.
MS transmitter EIRP per traffic channel (dBm) is the effective MS transmitting power in traffic channel.
It is calculated by the summation of BS maximum transmitter power per traffic channel (dBm), transmissionsystem losses (-dB), and the transmitter antenna gain (dBi).
BS receiver antenna gain (dBi) is the maximum gain for the receiver antenna in the horizontal plane and it
is specified as dB relative to an isotropic radiator.
BS cable and connector losses (dB) are the combined losses of all transmission system components
between the transmitter output and the antenna input. Note that all losses in positive dB values in link budget
table. A typical value is 3 dB.
Thermal noise density (dBm/Hz)
Details are described in Section 2.1 for forward link.
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Receiver Noise Figure(dB)
Details are described in Section 2.1 for forward link. 3 dB is estimated for Samsung system.
Loading factor (%) is the ratio of realistic maximum traffic users to Pole capacity, which is inversely
proportional to interference. This indicates the change of the user traffic. In general, 50% loading in reverselink is assumed in order to balance reverse and forward link capacity.
Interference margin (dB) is necessary to use in the reverse link budget since the loading of the cell, the
loading factor, affects the coverage. The more loading is allowed in the system, the larger is the interference
margin required in the reverse link, and the smaller is the coverage area. The relation between interference
margin (I .M) and loading factor (X) is as follows:
IocIscNIocIsc
NNX
th +++==
max
X
NIocIsc
IocIsc
NIocIsc
NN
NIocIscMI
thth
thth
th
=
++
+
=
++
=++
=1
1
1
11..
)1log(*10).(. XdBMI =
where,maxN : pole capacity
Isc: same cell interference density
Ioc: other cell interference density
thN :thermal noise density
For example, loading factors (cell loading) are 50% (= 0.5) and 70% (= 0.7), then, interference margin is 3dB
5.23dB, respectively.
Total effective noise and interference density (dBm/Hz)
Details are described in Section 2.1 for forward link.
Information rate(dB-Hz)
Details are described in Section 2.1 for forward link.
Required Eb/(No+Io) per antenna (dB) is the ratio of the required energy per bit to interference power
spectral density for a good quality on reverse link. In Samsung link budget, the simulation resulted from
3GPP2 contribution for both voice and data.services are adopted. The 1% and 5% target FER for voiceservice and data service, respectively are chosen.
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Receiver sensitivity (dBm)
Details are described in Section 2.1 for forward link.
Log-normal fade margin (dB) ,
Detail descriptions are in Section 2.1 for forward link. Note that the different combining methods are used in
forward and reverse link. A 95% area coverage and 9 dB of standard deviation are applied in Samsung linkbudget.
Handoff gain (dB) Detail descriptions are in Section 2.1 for forward linkThe following table shows the
handoff gains used in Samsung reverse link budget. They are obtained from the simulation.
Condition 95 % area coverage probability with 9 dB std. of fading
Service type Voice Data (153.6 kbps)
Channel model Pedestrian Vehicle Pedestrian VehicleGeometry (dB) 0 4 0
Handoff gain (dB) 4.45 0.15 0.32
The above table indicates that handoff gain in data service is smaller than that of voice service, since total
received power at MS in case of data service is lower than voice case due to the path difference to the MS
from each BS in serving cell and target cell. Penetration loss (dB) is the required margin to overcome the loss due to car and building
Detail descriptions are in Section 2.1 for forward link
Maximum allowable path loss (dB)
Detail descriptions are in Section 2.1 for forward link
Cell radius (km)
Detail descriptions are in Section 2.1 for forward link
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3. Examples of Link Budgets
3.1 1X Forward link Voice
3.2 1X Forward link data
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3.3 1X Reverse link voice
3.4 1X Reverse link data