UMTS Applied Radio Planning

UMTS Applied Radio Planning P025

Course Objectives ▪ Understand the key planning parameters of the UTRAN ▪ Produce UMTS Link Budgets for various services ▪ Understand UMTS Coverage and its KPI’s ▪ Understand Capacity dimensioning in UMTS ▪ Appreciate the Coverage/Capacity relationship in UMTS ▪ Evaluate GSM-UMTS Co-location issues

1- The UMTS Air Interface

The UMTS Air Interface

UMTS ▪ Universal Mobile Telecommunication System ▪ Also called “3G”, along with other IMT-2000 technologies ▪ The evolution from GSM-GPRS-EDGE ▪ WCDMA technology, part of the CDMA family


1.1- WCDMA, Processing Gain and Codes


CDMA - Direct Sequence Spread Spectrum

Frame Period (we may still need frames/timeslots for signaling)


CDMA Spreading •Essentially Spreading involves changing the symbol rate on the air interface

Spreading

Despreading

P

P

Channel f

f

P Tx Bit Stream

P

f f

Code Chip Stream

Air Interface Chip Stream

Identical codes

Rx Bit Stream

P f

Code Chip Stream


Spreading and Despreading 1

Tx Bit Stream

X

Spreading

Code Chip Stream Air Interface Chip Stream

Despreading

X

Code Chip Stream Rx Bit Stream

-1


Spreading and Despreading with code Y

Tx Bit Stream

-1

X

Spreading

1

Code Chip Stream Air Interface Chip Stream

Despreading

X

Code Chip Stream Y Rx Bit Stream


Interference mitigation Tx Signal

Rx Signal (= Tx Signal + Noise) P

P

f

f

P

P

Channel

f

f

Signal

Spreading Code

Spreading Code P

Signal

f

Wideband Noise/Interference ▪ The gain due to Despreading of the signal over wideband noise is the Processing Gain


Processing Gain ▪ If the Bit Rate is Rb, the Chip Rate is Rc, the energy per bit Eb and the

energy per chip Ec then

Eb = Ec ×

Rc Rb Gp =

▪ We say the Processing Gain Gp is equal to:

Rc Rb

▪ Commonly the processing gain is referred to as the Spreading Factor


Visualising the Processing Gain W/Hz

W/Hz

Before Spreading

W/Hz Ec

After Spreading

Io

With Noise

f

f W/Hz

W/Hz After Despreading /Correlation

Post Filtering Orthog = 0

f

Eb

dBW/Hz Eb

No

f

Eb/No No

f

f

Signal Intra-cell Noise Inter-cell Noise

W/Hz Post Filtering Orthog > 0

dBW/Hz

Eb

Eb

Eb/No No

No f

f


Types of Codes ▪ Channelisation Codes ▪Are used to separate channels

from a single cell or terminal

S2 C1 C2 C3

▪ Scrambling Codes ▪Are used to separate cells and

terminals from each other rather than purely channels

S1 C1 C2 C3

▪ Different base stations will use

the same spreading codes with separation being provided by the use of different scrambling codes.

S3 C1 C2 C3


Channelisation Codes ▪ Channelisation codes are orthogonal and hence provide channel separation ▪ Number of codes available is dependant on length of code ▪ Channelisation codes are used to spread the signal


Channelisation Code Generation ▪ Channelisation codes can be generated from a Hadamard matrix x x ▪

  A Hadamard matrix is:    x − x ▪

Where x is a Hadamard matrix of the previous level

▪ For example 4 chip codes are: ▫ 1,1,1,1 ▫ 1,-1,1,-1

Note: These two codes correlate if they are time shifted

▫ 1,1,-1,-1 ▫ 1,-1,-1,1


OVSF codes ▪ Orthogonal Variable Spreading Factor Codes can be defined by a code tree: Cch,4,0 =(1,1,1,1) Cch,2,0 = (1,1) Cch,4,1 = (1,1,-1,-1) Cch,1,0 = (1) Cch,4,2 = (1,-1,1,-1) Cch,2,1 = (1,-1) Cch,4,3 = (1,-1,-1,1) SF = 1

SF = 2

SF = 4

SF = Spreading Factor of code (maximum 512 for UMTS)


Code Usage Efficiency ▪ Any codes further down the trunk of▪ By filling up branches of the code

a branch in use cannot be used ▪ Any codes further out from the

branch in use cannot be reused

tree before starting new branches a greater capacity can be achieved ▪ Multiple code trees can be used

C ch,4,0 =(1,1,1,1) C ch,2,0 = (1,1)

IN USE

from a cell but at an increased level of interference between channels C =(1,1,1,1)

C ch,4,1 = (1,1,-1,-1)

C ch,4,1 = (1,1,-1,-1)

IN USE

C ch,1,0 = (1) C ch,4,2 = (1,-1,1,-1) C ch,2,1 = (1,1)

C ch,1,0 = (1)

C ch,4,2 = (1,-1,1,-1) C ch,2,1 = (1,1)

C ch,4,3 = (1,-1,-1,1)

IN USE

SF = 1

IN USE

ch,4,0

C ch,2,0 = (1,1)

SF = 2

C ch,4,3 = (1,-1,-1,1)

SF = 4 SF = 1

SF = 2

SF = 4


Scrambling Codes ▪ The spread data symbols are then scrambled by multiplying with a complex scrambling sequence ▪ Scrambling codes do not affect the chip rate ▪ The scrambling code is specific for a cell and thus serves to provide isolation between signals from adjacent cells ▪ There are 512 Scrambling Codes in the DL which can be allocated by Radio Planners


1.2- Ec/Io, Eb/No, NR and Loading


Interference and Noise Densities ▪ From the point of view of a UE, every other UE’s power appears as Interference ▪ Io is the Interference Density ▪ No is the Interference + Noise Density ▪ In general, when you talk about chips, or “Ec”, you use Io. When you talk about bits, or “Eb”, you use No. ▪ “No” considers Thermal Noise at the NodeB


Ec/Io ▪ Ec/Io is the Chip Energy we obtain in the presence of the Interference generated by all other users ▪ Ec/Io of the Pilot Channel is used to: ▫ Estimate (“sound”) the channel (multipath characteristics) ▫ Decide which server is “best server” ▫ Make handover decisions ▫ Typical requirement -15 dB


Eb/No ▪ Eb/No is the Bit Energy we obtain after despreading in the presence of the Noise generated by all other users and the Noise from NodeB equipment ▪ There’s a different Eb/No requirement for UL and DL: ▫ Typical requirement 1 to 10 dB ▫ Requirement varies by Bearer, Service, Multipath Profile, Mobile Speed, and Type of Receiver.


Noise Rise ▪ The effective noise floor of the receiver increases as the number of active mobile terminals increases. ▪ This rise in the noise level appears in the link budget and limits maximum path loss and coverage range. Three Users

Two Users One User Background Noise


Effect of Neighbouring Cells

Users in other cells cause interference. Typical ratio of power from other cells to power from own cell, i, is 0.6 (Urban Macrocells)


The Noise Rise Equation I total = PN

1 j =M

1− ∑ L j

=

1

Lj =

1 − ηUL

j =1

j =M

If we have M identical users:

Noise Rise =

1 N W 1 +  0   Eb  R j

∑ Lj =

M N W 1 +  0   Eb  R j

I total = PN 1−

1 M N W 1 +  0   Eb  R j

j =1


Noise Rise and Loading Factor ▪ Capacity is linked to Eb/No value ▪ Maximum Path Loss tolerated is linked to maximum NR

Noise Rise 1 dB 3 dB 6 dB 10 dB

Loading Factor 20% 50% 75% 90%

Noise Rise = −10 log10 (1 − ηUL )


Loading Factor Loading Factor =

Actual Throughput Pole Capacity

For M identical users with data rate R : Loading Factor =

MvR W

 Eb (1 + i )  N  0 

 Eb  M (1 + i )v  N  0 = W R


UL Pole Capacity For large number of users W Pole Capacity ≈ E   b (1 + i )  N0 

W = 3840000 Eb/No = 3 i = 0.5 3840000 Pole Capacity ≈ = 853 kbps (3)(1 + 0.5) • 50% of this would give a Noise Rise of 3 dB. •50% of 853 kbps = 426 kbps


DL Pole Capacity The Downlink benefits from orthogonality between channelisation codes.

Pole Capacity ≈

W  Eb   (1 − α + i )  N0 

α is orthogonality factor and has a value between zero and 1.


1.3- Power Control and Handovers


Power Control and Near/Far Effect ▪ When a UE is near the NodeB it doesn’t need much power to reach it ▪ In the same manner, if a UE is far away it needs greater power to communicate with the NodeB ▪ Power Control is needed in the UL because a single overpowered mobile could block a Cell ▪ Power Control is also needed in the DL to provide far away users with enough power and to keep power low for near-by UEs


Soft and Softer Handover ▪ In UMTS it is possible to have a UE connected to more than 1 NodeB. This is called Soft Handover ▪ When in Soft Handover, the RNC can combine the best signals from the NodeB’s, hence providing a Soft Handover Gain ▪ Softer Handover applies when the mobile is being served by two cells on the same site. A Softer Handover gain also occurs. ▪ However, too many mobiles in Soft or Softer Handover could impose a significant Overhead on the system


Active Set and Pilot Pollution ▪ The Cells with which the UE is communicating form the UE’s Active Set ▪ This Active Set is made typically of 3 cells/pilot signals ▪ Any Pilot which is not a member of a UE’s Active Set and exceeds a certain threshold (typ. Ec/Io>-15dB) is considered a Polluter ▪ Pilot Pollution is a common WCDMA issue that needs to be sorted immediately


Summary of Key Concepts ▪ Processing Gain ▪ Channelisation and Scrambling Codes ▪ Ec/Io ▪ Eb/No ▪ Noise Rise ▪ Cell Loading ▪ Pole Capacity ▪ Near/Far Effect ▪ Soft and Softer Handover Gain


Summary of Key Formulas ▪ Eb/No

Eb (dB ) = Ec + G p N0 I0 ▪ Pole Capacity

UL Pole Capacity ≈

W  Eb  (1 + i )  N  0

DL Pole Capacity ≈

W  Eb  (1 − α + i )  N  0

2- The UMTS Link Budget

The UMTS Link Budget

UMTS Link Budget vs. GSM’s ▪ Interference Margin for Noise Rise ▪ Target Eb/no

▪ Processing Gain (dBs) in UMTS

= 10 log (3840000/User Rate (bps))

▪ Power Control margin ▪ Handover Gains


Interference Margin ▪ An admission control parameter. Same as “Noise Rise Limit”

▪ Puts a limit to how many users can be taken in the UL

▪ Has an associated Loading Factor: ▫ NR= 3dB, Load Factor=50% ▫ NR=6dB, Load Factor=75%


Target Eb/No ▪ UMTS Link Budgets are made for Bearers

▪ A UMTS service may use one or more Bearers, with each

Bearer having a QoS Eb/No requirement

▪ A typical Voice Bearer requires an Eb/No of 5dB ▪ A typical 128 kbps Bearer requires and Eb/No of about 2dB


Processing Gain ▪ Depends on the bitrate of the Bearer

▪ Helps with the required Ec/Io at the receiver

▪ For a 12.2 kbps voice Bearer, Gp = 25dB ▪ For a 128 kbps data Bearer, Gp= 15dB


Power Control (Fast Fading) Margin ▪ It’s entered to allow for adequate Power Control to compensate

for Fast Fading

▪ It’s dependent on the Speed Profile of the Mobile

▪ At higher speeds, its smaller as the network cannot effectively

compensate for Fast Fading


Handover Gains ▪ If a UE is in Soft or Softer Handover, this will provide Diversity

Gains

▪ These gains can help the Link Budget by helping in achieving

the Target Eb/No with less power

▪ This gain is dependent on the Delta on the Ec/Io of the involved

paths


UL Link Budget ▪ Because UL power is lower than DL power coverage is

“UL limited”. ▪ Initially, most attention is paid to the UL budget.


-120 dBm Receiver Sensitivity ▪ Typical noise floor of cell receiver is -104 dBm. ▪ Considering full rate voice (12.2 kbps) processing gain is 25 dB. ▪ If target Eb/No is 5 dB and allowed Noise Rise is 4 dB then: ▫ UE must be capable of delivering (-104-25+5+4)= -120 dBm for

a successful connection. ▫ -120 dBm is effectively the receiver sensitivity for 12.2k voice. ▫ For a 128kbps service, the Rec. Sensitivity is around -110dBm


UL Link Budget - voice ▪ If the UE can transmit at powers up to +21 dBm, the maximum

link loss is: 21 - (-120) = 141 dB. ▪ The maximum air interface path loss can be calculated by

considering antenna gains and miscellaneous losses (e.g. feeder loss, body loss) ▪ If antenna gain = 17 dBi and losses = 4 dB, then maximum path

loss = 141 + 17 - 4 = 154 dB ▪ Note: margins not considered (e.g. shadow fading, building

penetration loss). These could total 24 dB.


Link Budget - voice Noise Floor Noise Rise Limit Processing Gain Target Eb/No Receiver Sensitivity UE Tx Power Maximum Link Loss Antenna Gain Feeder loss Body loss Maximum path loss Margins Target path loss

-104 dBm 4 dB 25 dB 5 dB -120 dBm +21 dBm 141 dB 17 dBi 3 dB 1 dB 154 dB 24 dB 130 dB


UL Link Budget - VT ▪ UMTS is introduced to offer higher level services such as video

telephony (VT). ▪ VT will typically operate at 64 kbit/s. ▫ Processing gain = 17.8 dB

▪ If all other parameters remain the same, then the maximum

path loss will be 154 - 25 + 17.8 = 146.8 dB. ▪ Different service:- different range. ▪ Typically range for voice = 1.6 x range for VT


UL Link Budget- 128 kbps Thermal Noise: -104 dBm, Noise Figure: 4 dB, Eb/No: 1.5 dB Processing Gain: 15 dB

(10 log[3840/128])

Receiver Sensitivity -113.5 dBm Max Link Loss = 21 dBm -(-113.5 dBm) = 134.5 Antenna Gains: 20 dBi

Feeder Loss: 3dB

Maximum Path Loss: 151.5 dB

Body Loss: 0dB


DL Link Budget- 128 kbps Allowable Path Loss: 151.5 dB Receiver Sensitivity -113.5 dBm Required Tx Power: 24 dBm per channel Eb/No= 1.5 dB, which in linear is i = 0.5

10^(1.5/10)= 1.41

1+i = 1.5

3.84 x103 DL Pole Capacity = = 3Mbps (1.41)(1 + 0.5 − 0.6) For 50% loading capacity = 1.5Mbps or 11- 128kbps channels 11 channels @ 24 dBm = 34.4 dBm


Conclusions ▪ Eb/No and capacity intimately linked. ▪ Link budgets are affected by fast fading and interference margins. ▪ Uplink and downlink affected differently by increased loading. ▪ Flexibility allows high data rate services to be provided. ▪ Asymmetric traffic requirements can be designed in.

3- Coverage Planning

Coverage Planning

Coverage Objectives ▪ Achieve Minimum Pilot Coverage on Service Area ▪ Minimum Coverage dependant on: ▫ ALP ▫ Services to be provided ▫ Loading ▪ KPI’s ▫ RSCP (Ec) ▫ RSS (Io) ▫ Ec/Io ▫ Pilot Pollution (Scrambling Code overlapping)

Coverage Planning

Factors affecting Coverage ▪ ALP is a function of: ▫ Clutter Type ▫ Shadow Fading Margin

▪ Services: ▫ The higher the bitrate the lower the coverage ▫ Different Eb/No requirements

▪ Loading: ▫ The higher the loading the lower the coverage ▫ Loading factor tied to Noise Rise Limit

Coverage Planning

3.1 Network Dimensioning

Coverage Planning

Dimensioning Inputs Environment Site Configuration

Service

Demographic

Geographic

Coverage Planning

Simple Coverage ▪ Link Budget based ▫ i.e. simple numerical calculation

Create Link Budget

Max PL

▪ Firstly a link budget is created ▪ The maximum path loss is used to calculate the

Calculate Range

Max Range

cell range using a propagation model Calculate Site Area

▪ The cell range is used to calculate the site area ▪ Site Numbers = (Total Area)/(Site Area)

Max Area Calculate Number of Sites in a given Area

Coverage Planning

Shadow Fading and Building Penetration ▪ Building Penetration ▫ Mean and standard deviation per environment

P(connect) 50%

75%

▪ Shadow Fading ▫ Typically calculated using ‘Jakes’

Fu =

1  1 − 2ab   1 − ab   1 − erf    1 − erf (a ) + exp 2 2  b   b  

Where: a =

(x0 − α ) σ 2

;

 e  b = 10n log10   σ 2 

x0-α = Fade Margin σ = Standard Deviation of Model

n = Propagation Model Exponent

x0 - α

0

P(connect)

76%

90%

Point Location Probability Area Location Probability 5.6

x0 - α

▫ This assumes an isolated omni directional site…

Coverage Planning

Environment Distribution ▪ Spreadsheets don’t deal

with topology or morphology accurately ▫ Hills, parks and distributed

target areas ▫ Interference and traffic

captured by sites will vary

▪ Margins for site acquisition

and overlap are required Urban Area

Suburban Area Site Numbers

Site Numbers?

Coverage Planning

3.2 Planning using Software Tools

Coverage Planning

Pilot Power as an Indicator If pilot power is 33 dBm, the pilot strength on the ground is an indicator of link loss. 113 dB loss: -80 dBm pilot 120 dB loss: -87 dBm pilot

Popular indicator as drive test measurements report on pilot strength.

•> -80 dBm

•> -87 dBm

Coverage Planning

Pilot Power as an Indicator issues ▪ Pilot powers not necessarily equal

deployment of MHA at selected sites will alter target pilot values. ▪ Even if MHAs are universally

deployed, their effect will depend on feeder loss. ▪ Generally, MHAs have a different

effect on UL to DL, therefore DL measurement not a reliable indicator of UL performance.

•> -80 dBm

•> -87 dBm

Coverage Planning

Letting the tool do the work ▪ It is possible to define: ▫The UE: in particular Tx Power ▫The bearer: bit rate and Eb/No. ▫Cell receiver: noise floor; noise

rise; feeder loss; MHA characteristics. ▫Margins required.

▪ This allows maximum path loss to

each cell to be determined and UL coverage to be calculated directly.

•VT coverage achieved

•Voice coverage achieved

Coverage Planning

Assessing Interference with a Static Analyser - Ec/Io ▪ Pilot Ec/Io indicates pilot

power as a ratio of total wideband power (including the pilot itself). ▪ Not terribly “scientific” but

it corresponds directly to measurement reported by the UE in drive tests.

Coverage Planning

Assessing Interference with a Static Analyser - Pilot SIR ▪ Pilot SIR gives the quality of

the pilot. ▫ Effect of orthogonality

on own-cell interference is considered. ▫ Pilot power not

considered as interference. ▪ Pilot SIR is always better

than Ec/Io.

Coverage Planning

3.3 Overcoming Coverage Problems

Coverage Planning

Limiting mutual interference

• Downtilt antennas. • Consider mounting antennas on the side of buildings.

Coverage Planning

Limiting mutual interference 6ºElec 0ºMech 0º

0º

0º 6º

6º

6º

0ºElec 6ºMech

-6º 6ºElec -6ºMech

6º 0º

0º

0º

0º

6º

12º

Controlling the backlobe can produce a small but significant improvement in capacity.

Coverage Planning

Limiting mutual interference • Key parameter: Frequency Re-use Efficiency (FRE).

FRE =

N Intra N Intra + N Inter

N Intra is the intra - cell interference (W) N Inter is the inter - cell interference (W)

Coverage Planning

Mast Head Amplifiers (TMA’s) ▪ Used to lower the Noise Figure of the receiver ▪ Can “offset” feeder losses ▪ MHA used to increase coverage range ▪ Typ. 1.6 dB Noise Figure (NF) ▪ Typ. Gain of 12dB (adjustable) ▪ Increase uplink capacity ▪ Adds Insertion loss on DL (~ 1.3 dB) DC

BiasBias-T

Ant by pass TMA

Coverage Planning

Uplink Receive Space Diversity ▪ Common to have two receive antennas per sector at the base station. ▪ Even if highly correlated, coherent combination should yield ~3 dB

improvement. ▪ In practice a gain of 4 dB or more is expected from antennas spaced 2-3

m apart.

Receive antenna 2

Receive antenna 1

Coverage Planning

Uplink Receive Space Diversity ▪ This is not “conventional” space diversity. ▪ Each antenna is connected to a separate finger of the Rake receiver. ▪ This is possible due to the synchronisation and channel estimation

derived from the Pilot channel. ▪ Thus Eb/No is improved, rather than simply an effective power gain. ▪ Very low individual Eb/No will probably mean a very low pilot level

which will lead to poor coherence and little gain - process becomes “self-defeating”.

Coverage Planning

3.4 Coverage in the Real World

Coverage Planning

Typical vendor values ▪ Pilot Power = 5-10% of Total Power

(30-35 dBm)

▪ Control Channel Powers = 3-5 dB below Pilot

(27-33 dBm)

▫ CCPCH’s

▪ Other signalling Channels = 3-5 dB below Pilot

(27-33 dBm)

▫ PICH, AICH, SCH’s

▪ Summary: Total Non-Traffic Channels = 20-25% of total power

Coverage Planning

Some additional constraints ▪ GSM existing coverage ▪ GSM legacy sites ▪ Antenna limitations: height, azimuths, etc.

4- Capacity Planning

Capacity Planning

Capacity Objectives ▪ Manage effectively predicted Load on Service Area ▪ Capacity dependant on: ▫ Number of users ▫ Position of users relative to the cell ▫ Services demanded ▫ UE Power Control

▪ KPI’s ▫ Cell UL Load Factor ▫ Cell DL Power

Capacity Planning

Factors affecting Capacity ▪ Number of Users: The more users the more noise ▪ Position of Users: The farther away, the more noise ▪ Services demanded: The more high-bitrate users on the cell, the less overall number of users possible ▪ UE Power Control: Imperfect power control will account for more noise in the network

Capacity Planning

Soft and Hard Capacity ▪ Hard Capacity: Hard limit imposed by actual channel elements ▪ Typ. 16 Kbps Channel elements. Also called “Resources” or “Cards” ▪ Soft Capacity: Variable, depending on Network loading

Capacity Planning

UL Pole Capacity ▪ Capacity is typically limited on the UL ▪ This is because, in the UL we don’t have Orthogonality to help us

W UL Pole Capacity ≈  Eb   (1 + i ) N  0

Capacity Planning

UL Pole Capacity Exercise- Voice ▪ If we assume a service with Eb/No = 6dB and i = 0.8 ▪ Eb/No= 4 (linear)

UL Pole Capacity= 533 kbps

▪ If you consider 12.2 kbps Voice bearers: ▫ 533/12.2 = 43.7 Voice Trunks

▪ Adding a typ. Voice activity factor (+overhead) of 58% ▪ New number of voice trunks is 533/(12.2x0.58) = 75.3

Capacity Planning

UL Pole Capacity Exercise- Voice ▪ A typical UMTS Cell can handle about 40E of Voice services ▪ With 75.3E being 100% capacity, 40E = 53% Loading ▪ Noise Rise= -10log (1-0.53) = 3.2dB ▪ Typically, 25% of this capacity will be allocated to Soft Handover

Capacity Planning

UL Pole Capacity Exercise- VT ▪ If we assume a service with Eb/No = 3dB and i = 0.8 ▪ Eb/No= 2 (linear)

UL Pole Capacity= 1066 kbps

▪ If you consider 64 kbps VT bearers with 100% activity factors: ▫ 1066/64 = 16.6 Voice Trunks

▪ Comparing bitrates: 64kbps/7.1kbps = 9

(7.1= 12.2x0.58)

▪ Comparing trunks: 75.3/16.6 = 4.5 ▪ Difference is due to different Eb/No’s 3dB (VT) vs 6dB (voice)

Capacity Planning

4.1 Multi-Services Capacity and Capacity Dimensioning

Capacity Planning

Multi-Service Capacity Eb/No

Activity Factors

▪ Voice= [email protected]

▪ 58%

▪ VT= 3.8dB@64kbps

▪ 100%

▪ 128PS= 2.8dB@128kbps

▪ 100%

dB vs Linear

Bitrate Ratios relative to voice

▪ 5.6dB= 3.6

▪ (1x) 7.1 kbps

▪ 3.8dB= 2.4

▪ (9x) 64 kbps

▪ 2.8dB= 1.9

▪ (18x) 128 kbps

Capacity Planning

Campbell’s Spreadsheet CS

CS

PS

PS

PS

Bearers (kbps)

12.2

64

64

128

384

CS user per cell

30

3

Not Applicable

Not Applicable

Not Applicable

Not Applicable

Not Applicable

0

0

0

58.0%

100.0%

0.0%

0.0%

0.0%

7.1

64.0

0.0

0.0

0.0

6

3

2

1.2

1.8

3.98

2.00

1.58

1.32

1.51

1

0.50

0.40

0.33

0.38

212.28

192

0.00

0.00

0.00

PS Capture Data (Mbytes/hour) Activity factor Average rate (kbps) Eb/No Eb/No ratio Relative Ratio Equivalent data rate (voice)

Factor for i

0.8

Reference Pole Capacity (kbps)

536

Loading of Cell

75.4%

UL Noise Rise (Loading)

6.10

Capacity Planning

Traffic Exercise ▪ Manchester pop. = 2.2 Million ▪ Mobile penetration@80% = 1.76 Million ▪ For an operator with 25% market share = 440K Subs ▪ With an avg voice traffic of 35mE per users = 15,400 Erlangs ▪ Considering 30E per cell = 513 Cells or 171 Sites ▪ This with 52% loading and 2% GOS

Capacity Planning

Simple Capacity Dimensioning ▪ Capacity calculation based

Calculate Carrier Capacity

▪ Calculate maximum capacity

per carrier

Calculate Sector Offered Traffic

▪ Calculate maximum offered

traffic per sector

Calculate Maximum Site Area

▪ Calculate site area based on

traffic density

Calculate Number of Sites in a Given Area

▪ Calculate the maximum number

of sites in an area

Capacity Planning

Other Dimensioning Factors ▪ GSM/UMTS Interaction ▫ Proportion a percentage of voice traffic to GSM ▫ Don’t assume that UMTS carries all of the traffic ▪ Microcells ▫ Offer capacity relief to macrocells ▫ This allows macrocells to be larger, potentially with a lower loading ▪ Repeaters ▫ Extend the coverage of macrocells at a lower cost than adding a new

Node-B

Capacity Planning

“2G” analysis ▪ Coverage thresholds can be set for various services and

coverage examined in a similar manner to that for GSM systems

▪ Traffic captured by cells for GSM traffic can be

interpreted as cell loading for UMTS systems.

Capacity Planning

4.2 Analysis of DL Capacity

Capacity Planning

DL Pole Capacity DL Pole Capacity ≈

W  Eb   N0

  (1 − α + i ) 

▫ The Downlink must be able to match uplink capacity ▫ If i=0.6 and Eb/No is 6 dB; pole capacity is 960kbps. ▫ At 50% loading UL capacity is 480 kbps (39 voice).

Capacity Planning

Further Analysis of the Downlink ▫ Minimum Rx power (25 dB processing gain, 3 dB Noise

figure) = -104 + 3 + 6 - 25 = -120 dBm ▫ If maximum Tx power is 21 dBm, then 141 dB link loss can

be tolerated. Can DL support this? ▫ For every user that’s “allowed” in the UL, the Cell will have to

provide enough power to support it on the DL

Capacity Planning

4.3 Traffic Planning

Capacity Planning

Traffic Density ▪ Traffic Density is forecast in terms of a density in terms of Erlangs per

square kilometre. ▪ Different forecasts are given for different clutter categories. ▪ Knowing the clutter categories in the required service areas allows traffic

to be simulated. Traffic Density Weightings 1 4

2 3

Clutter Category 1: Clutter Category 2: Clutter Category 3: Clutter Category 4:

10 50 30 10

Capacity Planning

Density versus Numbers ▪ It is important to realise that the weightings are in terms of terminal

densities. ▪ Sometimes the clutter category with the highest weighting occupies a small percentage of the area.

Area Weightings

1 4

Weighting of Actual Traffic per Category

3 2 3


28 16 28 28


▪ Notice that the actual traffic volume per category differs from the traffic

density. Traffic density is the parameter entered in the simulation tool.

4.4 Capacity Plots

12.7 36.4 38.2 12.7

Capacity Planning

Coverage vs. Capacity

Maximum Pathloss (dB)

Coverage vs. Capacity 170.00 165.00 160.00

Uplink

155.00

Dow nlink

150.00 145.00 100

200

300

400

500

600

700

800

Throughput (k bps )

Capacity Planning

Link Loss vs. Capacity

Capacity (kbit/s)

1200 1000 800 600 400 200 0 120

130

140

150

160

+43 dBm

+46 dBm

Link Loss (dB) +37 dBm

+40 dBm

Capacity Planning

Orthogonality vs. Capacity

Capacity (kbit/s)

1200 1000 800 600 400 200 0 0

0.2

0.4

0.6

0.8

1

Orthogonality BTS Power: 37 dBm

40 dBm

43 dBm

46 dBm

Capacity Planning

Capacity (kbit/s)

Out of Cell Interf. vs. Capacity 1400 1200 1000 800 600 400 200 0 0

0.4

0.8

1.2

1.6

Out of Cell Interference BTS Power: 37 dBm

40 dBm

43 dBm

46 dBm

2

Capacity Planning

Capacity Planning Summary ▪ Capacity dependant on: ▫ Number of users ▫ Position of users relative to the cell ▫ Services demanded ▫ UE Power Control

▪ Multiple Services Traffic characteristic of UMTS ▪ Pole Capacity, UL Cell Loading and DL Cell Power ▪ Erlangs vs. Number of Terminals

5- UMTS-GSM Co-location Issues

GSM Co-location

Co-location main Issues ▪ Have to live with existing GSM sites ▪ Have to live with existing antenna heights/azimuths ▪ GSM Interference: GSM1800, GSM1900, etc ▪ Different coverage extents

GSM Co-location

Interference Issues ▪ Interference can occur: ▫ between carriers ▫ between operators ▫ between systems

▪ Co-location of GSM and UMTS sites raises

special problems.

GSM Co-location

3rd Generation Spectrum Allocations 1885

ITU

1980

IMT-2000

MSS

Land Mobile

(WARC-92)

1880 1900 1920

Europe

UMTS

UMTS

GSM 1800

DECT

Unpaired

Japan

1980

Paired UL

2110

IMT-2000

20102025 UMTS

SAT

Unpaired

2110

1850

1850

SAT

Land Mobile DL

IMT-2000 1980

PCS

2110 IMT-2000 2170

Land Mobile DL 1990

1950

2200

2110

Reserved

DL

1900

2200

UMTS

Land Mobile UL

UL

1800

2170

2110 IMT-2000 2170

1910 1930

PCS

UMTS

2200

MSS

Paired DL

Land Mobile UL

USA

2170

Land Mobile

Land Mobile

UMTS

IMT-2000

1920 IMT-2000 1980

1920

Korea

20102025

2000

2050

2100

2150

2200

GSM Co-location

Intersystem Interference Issues ▪ Wideband Noise - unwanted emissions from modulation process and

non-linearity of transmitter ▪ Spurious Emissions - Harmonic, Parasitic, Inter-modulation products ▪ Blocking - Transmitter carriers from another system ▪ Inter-modulation Products - Spurious emission, specifications consider

this in particular ▫ Active: non-linearities of active components - can be filtered out by

Cell Equipment ▫ Passive: non-linearities of passive components - cannot be filtered

out by Cell Equipment ▪ Other EMC problems - feeders, antennas, transceivers and receivers

GSM Co-location

Isolation Requirements GSM 900

GSM 1800

UMTS

Receiving band 890 – 915 MHz 1710 – 1785 MHz (UL) Transmitting band 935 – 960 MHz 1805 – 1880 MHz (DL)

1920 – 1980 MHz 2110 – 2170 MHz

For example - To prevent UMTS BTS blocking: with transmit power = 43 dBm Max level of interfering signal for blocking = -15 dBm in UMTS

Isolation required = 58 dB

1805 MHz 1710 MHz

1785 MHz

GSM 1800 Rx

2110 MHz 1980 MHz

1880 MHz 1920 MHz

UMTS Rx

GSM 1800 Tx

2170 MHz

UMTS Rx

GSM Co-location

Typical Isolation Requirements Isolation Requirements Specification GSM Requirements 900/GSM1 UMTS Tx to UMTS Tx to GSM 900 GSM 1800 800 to Rx Rx UMTS Rx

UMTS Tx to UMTS Rx

Blocking isolation

58 dB

40 dB

48 dB

63 dB

Spurious emissions/inter -modulation products

39 dB

34 dB

34 dB

39 dB

GSM Co-location

Achieving Isolation Requirements GSM

▪ Isolation can be provided in a variety of different ways. UMTS

▫ By antenna selection and positioning.

GSM Filter

▫ By filtering out the interfering signal. UMTS

GSM

▫ By using diplexers and triplexers with

shared feeder and multiband antennas. Diplexer

UMTS

6- Practical Examples

Practical Examples

Small, isolated cell ▪ Traffic is spread across a small area with low path loss to the base

station. The cell is heavily loaded. ▪ Eb/No and Ec/Io failures are

associated with path loss.

▪ Noise Rise will be the only radio-

related cause of failure.

Practical Examples

Small, isolated cell ▪ Capacity improvements can be achieved by: ▪ Increasing Noise Rise limit. ▪ Reducing target Eb/No on the

uplink and the downlink.

▪ A Mast Head Amplifier will not be

of much use as uplink Eb/No is not a significant cause of failures.

Practical Examples

Large, isolated cell ▪ As loading increases, meeting Eb/No targets will be a problem. ▪ Heavy loading will result in Cell Breathing. ▪ Users at a great distance from the

base station will not be able to make a connection.

▪ Gaps will appear in network

coverage.

Practical Examples

Sectored Sites ▪ Capacity will be affected by overlap of cell coverage areas.

▪ Cell overlap can be controlled by

pointing of antennas.

▪ Combining mechanical and

electrical tilt can control backlobe radiation.

Practical Examples

Pilot Pollution ▪ A mobile can be too well served.

▪ It may be impossible to decode a

dominant pilot. ▪ Ec/Io and Eb/No failure due to co-

channel interference. ▪ Scaling pilot power and controlling

radiation patterns is vital.

Practical Examples

Soft Handover ▪ Soft handover regions must be controlled to ensure that capacity is

maximised. ▪ Handover margin can be adjusted.

▪ Pilot powers can be scaled.

▪ Effect on handover region can be

monitored.

Practical Examples

Dimensioning and Simulating a Network ▪ We are able to approximately dimension a network with a simple

spreadsheet.

▪ This is a simplified network not considering the effects of mapping data

and uneven traffic distribution.

▪ However, it is possible to simulate such a simplified network so that a

clear understanding of the working of the simulator can be established.

▪ The network can then be modified to incorporate practical features such

as terrain features and traffic distribution.

6.1 Simulation Examples

Practical Examples

The Network and Height Profile ▪ 3dB NR limit

▪ 20m antennas

▪ No MHA, no RX

diversity

▪ 500 Terminals

spread on Urban and Suburban areas

Practical Examples

Voice- Reason for Failure ▪ Polygon area

OK as far as Voice Service

▪ Some NR Limit

reached failures (aqua pixels)

Practical Examples

VT- Reason for Failure ▪ Polygon area

shows UL Eb/No failures

▪ NR Limit

reached failures (aqua pixels)

▪ Changing

azimuths on site to the right of polygon is not an option due to existing traffic restrictions

Practical Examples

VT- NR Limit increased to 6dB ▪ NR limit

parameter changed from 3 dB to 6 dB on all cells

▪ NR Limit reached

problem fixed

▪ UL Eb/No

problem still there

Practical Examples

Pilot Coverage for Polygon ▪ Looking for the

causes of the failure, a Pilot Coverage plot is done

▪ It can be seen

that Pilot level in Polygon area is very low (around -105 dB)

Practical Examples

Height Profile for Polygon ▪ Looking for the

causes poor coverage, a Height Profile is performed ▪ It can be seen

that there is a significant obstruction preventing a good UL

Practical Examples

Height increased to 40m ▪ Trying to fix the

UL Eb/No failure, antenna height is increased from 20m to 40m

▪ This decreases

the pathloss, however, the original problem is not solved

▪ No interference

problems are created either

Practical Examples

Adding MHA and RX Diversity ▪ Another option is

to add an MHA and RX Diversity

▪ These additions

prove the solution for most of the problem pixels inside the polygon

▪ Height is still

40m, due to obstructions and poor site location

End of course

UMTS Applied Radio Planning

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