01 Link Budget and Dimensioning

Slide 1Company Confidential
* © Nokia Siemens Networks WCDMA Network Link Budget and Dimensioning/Deepak Yadav/Aug2008
Company Confidential
BTS antenna gain
Propagation Model
QUALITY RELATED
Indoor/Outdoor Coverage
Location Probability
Blocking Probability
Gives an Estimation of the Equipment Necessary to Meet the Network Requirements
Network Dimensioning Activities
Input Categories
WCDMA Capacity
Traffic distribution and forecase uncertainty and imperfect site selection
Cell-A
Cell-C
Cell-B
"actual" Loading, (ie from the traffic inputs defined in dimensioning)
e.g.. Forecasted Actual UL load = 8%
e.g.. Real Actual UL load = 30%
"actual" Loading, (ie from the traffic inputs defined in dimensioning)
This diagram shows a Fixed Uplink Load design
Results => No or Min Coverage Holes!
No (or minimum) coverage holes problems
More cells required
Cell-A
Cell-C
Cell-B
Cell-D
Cell-E
Cell-F
Cell-C
Cell-B
Cell-G
Cell-A
Cell-H
Uplink
Can be based on many different PS and CS services
Downlink
Can be based on many different PS and CS services
HSDPA/Rel’99 link budget
Uplink
HSDPA associated UL DPCH link budget is used which can be PS 16, 64 ,128 or 384 kbps
Peak HS-DPCCH overhead is included to the Rel’99 DCH
Downlink
HSDPA/HSUPA link budget
Peak HS-DPCCH overhead is included to the HSUPA Eb/No
Own connection interference is included
Downlink
General Settings
Supported Release (not shown, new for version v1.1.1), Clutter Type, Channel Model, Bearer type, Operating Band, RF part selection
Transmitting End Settings (NodeB and UE as well)
Feeder, Antenna, CCCH settings
TMA, Load settings
Radio Network Configurations Settings
Site Layout, Area Size, Required Coverage settings
Trzeba by zupdateowa screena bo nie ma ju Data Card tylko UE Power Class
Critical Parameters - Eb/N0
In order to meet the defined quality requirements (BLER) a certain average bit-energy divided by total noise+interference spectral density (Eb/N0) is needed. NSN simulations for Eb/No are based on ITU recommendations.
Eb is the received energy per bit from the wanted user,
Io is the total received power density, from both interference and thermal noise, excluding the power of the wanted signal.
Eb/No depends on:
HSDPA – General
Data from simulations can have two formats
Throughput vs. CINR for different HARQ (Former Siemens simulations)
Throughput vs. SINR for different amount of codes (Former Nokia simulations)
SINR values are recalculated to CINR values an then put into configuration file
For calculations used values (HARQ = 1 ex-Siemens; 15 codes ex-Nokia)
Simulation results is visualized on following graphs with both BTS lines Eb/Nos vs. throughput
Extensive link level simulations have been conducted in order to identify default values for the HS-DPCCH power offsets that fulfill the HS-DPCCH detection probabilities as specified by 3GPP.
HSDPA – General
CINR value is mapped to the throughput with simple calculation
No limitation on what to put in the data rate input
The Eb/No is calculated from fixed CINR points
168.3 kbps is lower limit with -11.21 dB and 314 kbps is higher limit with -8.41dB
Then gradient, which is 51.83 kbps/dB
Then calculation of CINR -9.64 dB
And last CINR to Eb/No 2.22 dB
Example: 250 kbps
HSDPA – General
Interference Margin Calculation
The link budget uses an interference margin which is calculated as ratio of total inference and thermal noise
Influencing parameters:
nothing else than Information Rate
W - chip rate
f - Other-to-own-Cell Interference factor at cell edge
HSUPA – General
Simulation contains:
HARQ values
Left hand side throughput vs. Eb/No for both PL
Differences are coming from different simulation setups and assumptions
exNokia Eb/No results correspond well in real RAS06/RU10 system behaviour and system implementation.
exNokia values similarly include 1 dB implementation margin which is used to be more on the safe side as the simulations show always optimal conditions when comparing to real system.
HSUPA – General
LV – is HS-DPCCH Overhead for left boundary of considered range
RV – is HS-DPCCH Overhead for right boundary of considered range
LBR – is BitRate for left boundary of considered range
RBR – is BitRate for right boundary of considered range
BR – is currently considered BitRate
2.18
HSUPA – General
Own connection interference
The own connection interference factor reduces the uplink interference floor by the UE’s own contribution to the uplink interference, i.e. by the desired uplink signal power
This factor is included in the HSUPA link budget because uplink bit rates can be greater and the uplink interference contribution from each UE can be more significant
R = Uplink Bit Rate, W = Chip Rate
Eb/No= + 4 dB
RT 64 kbps
Critical Parameters - Interference Margin
Interference margin is calculated from the UL/DL loading () values. This parameter shows in DL how much the BTS "sensitivity" is decreased due to the network load (subscribers in the network) & in UL indicates the loss in link Budget due to load
IMargin =
20
10
6
1.25
3
25%
50%
75%
99%
Critical Parameters - Fast Fading Margin
Describes a margin taken into account as a power backup at the transmitting end
This margin reflects the accuracy of the closed loop fast power control algorithm to follow the steep fluctuations of the link loss caused by the fast fading
This is needed at cell edge for UEs to be able to compensate fast fading
Default values:
Mobile transmission
Critical Parameters - Soft Handover Gain
SHO gain, also called Macro Diversity Combining, gives the Eb/No improvement in soft handover situation compared to a single link connection
In dimensioning SHO Gain is considered at the cell edge
This phenomenon reduces the negative effect of small scale fading
It allows to use lower transmit power or Eb/No requirements
Soft HO
SHO MDC gain (dB)
Critical Parameters - Gain Against Shadowing
At cell edge there is the gain against shadowing. This is roughly the gain of a handover algorithm, in which the best BTS can always be chosen (based on minimal transmission power of MS) against a hard handover algorithm based on geometrical distance.
In reality the gain against shadowing gain is a function of required coverage probability and the standard deviation of the signal for the environment.
The gain is also dependent on whether the user is outdoors, where the likelihood of multiple servers is high, or indoors where the radio channel tends to be dominated by a much smaller number of serving cells.
Soft handover gain can be understood also as reduction of Shadowing Margin
Target Service
With UL fixed at 64Kbps, Limiting Link is CS64
In Symmetrical traffic environment, PS384Kbps is the limiting link
≈ 1.75dB
1.25
3
20
10
6
25%
50%
75%
99%
≈ 1.5dB
≈ 15%
≈ 1.5dB
≈ 15%
Assumptions and Scope
This exercise was performed to demonstrate the 3G network planning(2100MHz) for 19 main cities of Vodafone circles.
Main objective was to provide the site count for various cities in order to support CS64 as umbrella service.
Existing 2G sites were to be considered for future 3G sites and special care is taken while planning 3G sites to re-use existing sites as much as possible.
New 3G sites had also been considered in the special cases where no other alternative was available.
Planned 3G network is entirely coverage driven i.e. capacity aspect is only calculated based on the coverage sites and no additional capacity sites has been considered.
Offered traffic based on coverage sites.
Both GSM900 and GSM1800 networks are be considered for 3G planning to better understand the site count requirements for 3G network.
Data service will be based on “Best Effort” basis only i.e. network will support various data services depending upon the user location.
Map Data 04-05 has been used to perform this planning activities.
Remove Existing Sites which are too close to each other
Coverage Prediction
Target Design
No
Any Coverage Holes?
Add new 3G sites to fill up coverage holes in network
Yes
No
Yes
Avg Reuse approx 85%
Complete Network dimensioning in the end should provide following results -
Cell Range
Site Area
Coverage Thresholds
Number of capacity sites
CE requirement per site
Total Number of sites
Cell Range
Site Area
Coverage Thresholds
Achieved Loading
Total Number of Sites
CE requirement per site
CEs capacity
Site/Cell throughput
Code tree
Cell coverage
Traffic model
+ Very simple approach
+ Rough estimation of throughput can be seen from many studies, which can be used in estimations
- Link budget needed to be used for coverage estimation, not co-used with capacity
- Accurate information about simulation approach and parameters many times missing
No possibility to see the effect of changing parameters
3. Use of Excel dimensioning tool
+ More flexibility to estimate effect of different DCH effect on HSUPA capacity in UL
+ Possibility to get more accurate estimations of coverage and capacity with flexible parameter change
- Requires understanding of the process and parameters
- User has to verify that the dimensioning results and set parameters are in line with the simulation results and according on Nokia specifications
- There is always limitations when using Excel tools
1. Use of COO/R&D Network Engineering dimensioning tool
+ Reliable and harmonized way of doing dimensioning
+ Detailed calculation with fixed parameters
+ Calculation errors not common (if found report immediately!)
+ Product line providing the system parameters
- Complex, hard to implement and change parameters
- Result checking needs detailed understanding of the tool
Recommended method
Network Description
per layer)
Optional: HSPA
Traffic
Assignment
Traffic calculation
Equipment Calc.
No of Node Bs, No of CHCs/ No of FSMs
Equipment
Calculation
Traffic
Assignment
Final Results
Vodafone
Airtel
TTSL
PO – traffic (Rel99, HSDPA, HSUPA):
“best effort”
Multiplexing gain:
CS – traffic:
Formats of traffic model:
BHCA, duration of call or session
and activity or on/off ratio
Throughput per area, PS traffic [kbit/s],
CS traffic [kbit/s] or [Erl]
Throughput per subscriber, PS traffic [kbit/s], CS traffic [kbit/s] or [Erl]
Constrains
1 format of traffic model can be chosen per scenario
Traffic volume is defined separately for each area and phase
Traffic format recalculation is possible
Formats of traffic model per area
Formats of traffic model per subscriber
Recalculation possible
@ 40mErl BH Traffic
Sum ≈ 6.2 Millions
With mixed Traffic profile
Baseband (BB) capacity
Channel Element (CE) refers to the capacity requirement of 1 User voice/16 kbps (UL&DL)
Upgrades in min. 1CE (Channel Element) steps
Additional CE by SW license key
HW supports CCH, DCH, HSDPA and HSUPA
384 kbps supported in UL and DL for both HSDPA and R99 services
Changed to 12
Common channels
Remaining available
Code channels calculation
The number of code channels per BTS are calculated so that the first needed traffic channels per BTS is calculated .
This is done per BTS since the code channels are in one pool over the whole BTS.
The traffic per BTS is calculated from the calculated number of subscribers per BTS and from the subscriber profile.
Then the needed traffic channels per BTS per service is calculated as well as the number of physical channels .
Next the soft handover Overhead is added to the calculated traffic channels to get the no. of physical channels per BTS. The soft Handover overhead addition is done for both UL and DL.
Traffic profile per cell
Traffic profile per BTS
Traffic channels per BTS
Add SHO Overhead for
channels per service into
Add the needed no. of
control channels for
Thank You

01 Link Budget and Dimensioning

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