08 RA41208EN30GLA0 LTE Radio Planning Capacity GC

1 © Nokia Siemens Networks RA41208EN30GLA0

LTE RPESS Radio Planning Capacity


Module Objectives

After completing this module, the participant should be able to:

• Understand basic traffic modelling

• Evaluate the cell capacity

• Understand the main factors impacting the cell capacity

• Review the baseband dimensioning


Radio Planning Capacity

Capacity Dimensioning

Cell Capacity (Throughput)

Baseband Dimensioning


Capacity Dimensioning Process – Overview

Site Area Area Size Subscribers Traffic Model Site Capacity

Subscribers

Density

Subscriber Data Volume in BH

Total Offered Traffic

# Capacity Sites

# Coverage Sites

# Sites

Max

BH = Busy Hour

• Outputs:

• Site count for capacity and coverage

• The final number of sites is the bigger number from capacity and coverage point of view

• The calculation could be done for each clutter type and for different phases (for example

years)


The Number of Sites due to Coverage


Subscribers

Density

Subscriber Data Volume

in BH


# Capacity Sites

# Coverage Sites

# Sites

Max

BH = Busy Hour


The Number of Sites due to Coverage

Area Size (Km²)

• this is the planned area

• typically defined for each clutter type

• the customer may provide this value

Site Area (Km²)

• this is the site area calculated from the link budget and using the propagation model

• depends on the number of cells per site (typical 3 cells per site)

Number of sites due to coverage:

# Sites due to Coverage = Roundup (Area Size / Site Area)

Example:

• Planned area is 100 Km²

• Site Area is 10 Km²

• The number of sites due to coverage is 100 Km²/ 10 Km² = 10


The Number of Sites due to Capacity


Subscribers

Density


in BH


# Capacity Sites

# Coverage Sites

# Sites

Max

BH = Busy Hour



Operator subscriber density depends on: • Population density

• Mobile phone penetration

• Operator market share

The subscriber density & subscriber traffic profile are the main

requirements for capacity dimensioning

Traffic forecast should be done by analysing the offered Busy Hour traffic

per subscriber for different services in each rollout phase

Traffic data:

• Voice: • Erlang per subscriber during busy hour of the network

• Codec bit rate, Voice activity

•Video call : •Erlang per subscriber during busy hour of the network

•Service bit rates

• NRT data : • Average throughput (kbps) per subscriber during busy hour of the network

• Target bit rates


Traffic Model • Subscriber traffic profile from

traffic model

• The main purpose of traffic model is

to describe the average subscriber

behaviour during the most loaded

day period (the Busy Hour)

• One example is the NSN LTE

traffic model

– The traffic model defines an

application mix consisting of 5

services (VoIP, Video,

Streaming, Web browsing & FTP)

– There are 3 subscriber profiles

each one mapped onto an

application mix: Voice Dominant

Data Dominant

Voice/Data

session length

or

session size Typical Subscriber’s Profile:

FTP = File Transfer Protocol

BHCA = Busy Hour Call Attempts

NSN Traffic Model (TM)


Total Offered Traffic – Example

• Number of Subcribers = 10,000

• Average Data Volume per Subscriber per Busy Hour (BH) from the NSN

Traffic Model assuming the data dominant scenario: 10.24 MByte

• The Average Data Rate per Subcriber could be calculated as:

= Average Data Volume per Subscriber per BH [bit] / 3600 s

= 22.75 Kbps

• The Total Offered Traffic could be calculated as:

= Number of Subscribers * Average Data Rate per Subscriber

= 10,000 * 22.75 Kbps = 227.5 Mbps


Capacity Dimensioning Process – Overview


Subscribers

Density


in BH


# Capacity Sites

# Coverage Sites

# Sites

Max



• Site Capacity – The site capacity could be derived from the cell capacity:

Site capacity = Cell Capacity * Number of Cells per Site

– The cell capacity is defined as the overall cell throughput (average cell capacity)

– Calculation of an average cell throughput in LTE is based on system level

simulations

– Details are provided on the next section of this chapter

• The number of sites due to capacity:

# Sites due to Capacity = Roundup (Total Offered Traffic / Site Capacity)

Example:

– Site Capacity is 10 Mbps

– Total Offered Traffic is 100 Mbps

– The number of sites due to capacity is 100 Mbps/ 10Mbps = 10







Cell Throughput Calculation Methodology

• DL & UL Capacity are calculated based on system level simulations

• Algorithm calculates the Average Cell Throughput (capacity) for a single cell

• During the system level simulations effects like UE mobility, slow/ fast fading,

scheduling, power control, admission control, handovers have been considered

• The basic principle of these simulations is that for a given cell area a certain (evenly

distributed) subscriber density is assumed and for each subscriber particular SINR

conditions apply which depend on the location of the subscriber in the cell

• Capacity Simulations Results:

• Calculation of an average cell throughput is based on a method which calculates

the spectral efficiency

• 4 representative site grids (defined by the Inter-Site Distance (ISD): 500m, 1732m,

3000m, 9000m) have been simulated in dynamic system level environment

• UL & DL spectral efficiency figures have been gathered for all available channel

bandwidth configurations (1.4MHz, 3MHz, 5 MHz, 10MHz, 15MHz & 20 MHz)


Simulation Assumptions

Parameter/Feature UL DL

Operating Band 2100 MHz 2100 MHz

Transmission power per PRB Open loop power control; max UE

power 23dBm

0.8 W (for every bandwidth

configuration)

Antenna Scheme Number of TX antenna = 1

Number of RX antenna = 2

Number of TX antenna = 1

Number of RX antenna = 2

Hexagonal layout 3 sector layout, 7 sites, 21 cells 3 sector layout, 7 sites, 21 cells

Scheduling Channel unaware with Round Robin

strategy

Channel aware with Proportional

Fairness

Mean number of users per sector 10 UEs (ISD = 500m)

30 UEs (ISD = 1732m)

60 UEs (ISD = 3000m)

164 UEs (ISD = 9000m)

10 UEs per sector

210 UEs per area

Number of users per TTI 1 (1.4 MHz)

3 (3 MHz)

7 (5 MHz)

10 (10 MHz)

20 (15 & 20 MHz)

1 (1.4 MHz)

3 (3 MHz)

7 (5 MHz)

10 (10 MHz)

20 (15 & 20 MHz)

UE speed 3Km/h 3Km/h

Traffic model Full buffer * Full buffer *

Propagation model 3GPP TR 25.814 (macro cell) 3GPP TR 25.814 (macro cell)

*Full Buffer indicates the cell load is always 100% independent on the number of subscribers in the cell or their position in the cell


UL/DL Spectral Efficiency

UL Spectral Efficiency DL Spectral Efficiency

ISD: Inter-Site Distance

Sp

ectr

al E

ffic

ien

cy (

Kb

ps/K

Hz)

Note: The simulation setup refers to SIMO mode, and focuses on realistic assumptions rather than on an idealized configuration.


UL/DL Cell Capacity

UL Average Cell Throughput (C100%) DL Average Cell Throughput (C100%)



Cell Throughput Interpolation

Purple bars obtained from simulations. Yellow bars have been interpolated based on simulation results.

• In real planning scenarios the Inter Site Distance (ISD) obtained from the Link Budget Calculation is not equal to the ISDs that have been simulated

• Therefore, additional interpolation is required to adapt to the results from the Link Budget

• One interpolation example could be seen below:


Factors Affecting the Cell Capacity

• The LTE Cell Capacity (Throughput) depends on:

• Cell Range (Pathloss) – Considered as a variation of the Inter Site Distance (ISD)

– The effect of larger ISD has been presented in the previous slides

– The SINR distribution is bad in larger cells which becomes more & more noise limited

• Channel Bandwidth (1.4 MHz ... 20 MHz) – The best capacity performance can be achieved with wide channel bandwidth due to

the maximum frequency diversity gain

– Small Bandwidth configuration are characterized by high system overhead

• Cell Load – The values presented so far are for 100% cell load

– The impact of cell load is based on simulation results

• LTE Features: – MIMO (Multiple Input Multiple Output)

– Scheduling: Proportional Fair or Round Robin

See next slides for details


Impact of Cell Range on Cell Capacity

DL


Spectral Efficiency Relative to 10 MHz

0 %

20 %

40 %

60 %

80 %

100 %

120 %

1.4 MHz 3 MHz 5 MHz 10 MHz 20 MHz

Downlink

Uplink

Impact of Channel Bandwidth on Cell Capacity

-40% -13% Reference

LTE maintains high efficiency with bandwidth down to 5 MHz

The differences between bandwidths come from frequency scheduling gain and different overheads


Impact of Cell Load on Cell Capacity (1/3)

• Simulated spectral efficiency (SE) figures are calculated for 100% load in all cells: – Best case from the resource utilization point of view (all resources -PRBs- are utilized)

– Worse case from the interference point of view

• Additional simulations are available to investigate the impact of the cell load – The simulation scenario is shown in the figure below

– The centre cell which is fully loaded all the time is the victim for which the overall cell

throughput is measured

– Surrounding cells impact the victim by inter-cell interference which depends on the

neighbor cell load



• The figure below shows the relation between the victim cell throughput & the neighbour cell

load

• The victim cell throughput has been normalised to 1 in the figure, the value of 1 meaning

100% neighbor cell load

• It has to be noticed that when the neighbour cell load is decreasing the cell throughput is

increasing as expected

• The most sensitive to interference is the case ISD = 500m



The impact of the cell load on the cell throughput can be summarized by applying scaling

factor for different ISDs and different cell load:

The Capacity C considering the

Scaling factor is:

C = C100% x load x scaling_factor(load)

Example:

ISD = 500m

Cell Load is 50%

the Capacity C is:

C = C100% * 0,5 * 1.36 = 0.68 C100%


C100%: Capacity, when all cells are loaded to 100%


Impact of MIMO on Cell Capacity (1/3)

RL 30 supports 2 transmit antennas at the eNodeB

Transmit diversity (Tx diversity)

• results in coverage improvement

• therefore, it is more suitable to be used at the cell edge

Open / Closed Loop Spatial Multiplexing

• Spatial multiplexing on the other hand doubles the user data rate

The mechanism of Adaptive MIMO Mode Control assures CQI dependent switching

between Transmit Diversity and Spatial Multiplexing (see next slide)

The average cell capacity is then determined by:

• the ratio of the dual-stream transmissions (how much Tx diversity & how much spatial

multiplexing) for one connection in average

• The number of users out of total cell users which are using either Tx diversity or spatial

multiplexing



Simulation Results (Source 4GMAX) Tx Div: Transmit Diversity

SM or SpMux: Spatial Multiplexing

OL MIMO: Open Loop MIMO

SNIR: Signal to Noise + Interference Ratio



• The highest gain could be seen for smaller ISD (higher SINR values over the cell so

higher probability to be dominated by spatial multiplexing)

• The lowest gain is for bigger ISD (lower SINR values more likely so the cell is dominated

by transmit diversity)

Recommended Adaptive MIMO Mode Control Capacity Gain

The gain values in % are relative to the original spectral efficiency (without MIMO)

4 ISDs (Inter Site Distances) = 500m, 1732m, 3000m, 9000m

Inter-site distance ISD (m)

10%

20%

30%

500 m 1732 m 3000 m 9000 m

16%

24%

15% 15%

2x2 OL MIMO Mode 3

2x2 CL MIMO Mode 4


Impact of Scheduling on Cell Capacity (1/3)

• In RL 20 two scheduling strategies for DL FDPS* are supported:

• Round Robin RR (default)

• Proportional Fair PF (license)

• From the average cell throughput point of view there is some gain when

Proportional Fair (PF) is used versus Round Robin (RR)

• The main reason for the gain is coming from the fact that the SINR distribution in

the cell is improved when Proportional Fair is used

• The gain is dependent on the number of users that are scheduled together in the

same TTI (1ms): the higher the number of scheduled users per TTI the higher the

average cell throughput gain when Proportional Fair is in use

• 2 examples coming from simulations are shown in the next slides:

• 3 scheduled users per TTI

• 10 scheduled users per TTI

* FDPS: frequency domain packetscheduling



CDF (Cumulative Distribution Function) of SINR

Average Sector Throughput [Mbps]

Case 1: 3 simultaneous Users per TTI

*Assumptions: Operating Band 2GHz, Channel Bandwidth 10MHz, Total Power of the eNodeB shared among the PRBs, Antenna Scheme is 1Tx – 2RX, Full Buffer traffic model, random uniform distribution of users

PF

RR

RR

PF



Case 2: 10 simultaneous Users per TTI

Average Sector Throughput [Mbps]

*Assumptions: Operating Band 2GHz, Channel Bandwidth 10MHz, Total Power of the eNodeB shared among the PRBs, Antenna Scheme is 1Tx – 2RX, Full Buffer traffic model, random uniform distribution of users

PF

RR RR

PF

CDF (Cumulative Distribution Function) of SINR


Cell Capacity Calculation Example

Step 1: To obtain the Spectral Efficiency (SE) figures for specific ISD (Inter-site

distance) and channel bandwidth interpolation is needed:

SE = interpolate_SE (ISD, channel_bandwidth)

Step 2: Calculate the cell throughput (C) from the spectral efficiency (SE) taking into

account the cell bandwidth:

C = SE x channel_bandwidth

Step 3: MIMO gain is applied in case of 2 TX antennas at eNB

C = C x (1 + MIMO_gain(ISD))

Step 4: Spectral efficiency figures have been simulated for 100% load case. It is needed

to scale them according to the resource utilization and inter-cell interference level

C = C x load x scaling_factor(load)

Step 1: interpolate_SE(500m, 10MHz) = 1.19bps/Hz

Step 2: C = 1.19bps/Hz x 10MHz = 11.9Mbps

Step 3: C = 11.9Mbps x (1+20%) = 14.28Mbps

Step 4: C = 14.28Mbps x 50% x 1.37 = 9.8Mbps

Example for ISD=500m, 10MHz, 2x2 MIMO, 50% load


LTE Capacity: RL20 & RL30 features

Voice over LTE

LTE VoIP

3G CS voice

LTE VoIP

3G CS voice 3G CS voice 3G CS voice

Single Radio Voice Call Continuity (SR-VCC)

Options for voice call continuity when running out of LTE coverage (RL30):

• 1) Handover from LTE VoIP to 3G CS voice

– Voice handover from LTE VoIP to WCDMA CS voice is called SR-VCC

– No VoIP needed in 3G

• 2) Handover from LTE VoIP to 3G VoIP

– VoIP support implemented in 3G

LTE VoIP available in RL20

15 x more users per MHz with 3GPP LTE than with GSM EFR!


RL30: 3 Sector vs. 6 Sector Capacity

LTE 6-sector site solution brings >70% site throughput gain compared to 3-sector

In RL30 also 6 sector sites are supported

The single cell capacity decrease by around 6% mainly due to increased inter-cell interference

The site capacity is increasing by more than 70%







Baseband Dimensioning Target of Baseband Dimensioning:

• Target of Baseband Dimensioning: Allow to estimate HOW many sites are required taking

into account the HW (System Module) Limitations

• The approach presented so far in this chapter to calculate the number of sites from the

capacity point of view (site throughput) only takes into account Physical Layer and/or RRM

features into account (e.g. Channel bandwidth, transmit power, scheduler type, etc...)

System Module options:

• FSME: high capacity system module

• FSMD: lower capacity system module

• Note: FSME is the only one supported by RL10 and by RL20.

In RL 30 also FSMD is available

Input of the dimensioning:

• Total Number of subscribers

• Number of active subscribers (per Site)

• Share of active subscribers

Output of the dimensioning:

• Number of sites from baseband point of view


Active Subscribers

• Flexi SM processing power has a strict limitation for the number of active UEs which can be handled*

• UE in E-UTRAN RRC_Connected and with DRB (Data Radio Bearer) established but with or without data to be transmitted in the buffer i.e. smartphones with always on applications like IM and mail

Share of active Subscribers

• Percentage of active subscribers which should

be handled by the eNB

• Share of Active Subscriber values have been

calculated for each of NSN Traffic Models:

– Voice Dominant: 11%

– Data Dominant: 40%

– Voice & Data Mix: 30%

• Typical assumption is 30% Share of Active Subscribers for RL20 dimensioning

Baseband Dimensioning Input for the Dimensioning

*Note that in LTE the System Module capabilities depend strictly on the number of the included DSP modules. The 3G specific notation of system module capacity by means of Channel Elements (CEs) is not anymore valid

*Note that for FSME 3 cells per system module are assumed for all frequency bands.

For FSMD there are 3 cells per system module for 5 &10 MHz and 2 cells per system module for 15 & 20MHz


Baseband Dimensioning Output of the dimensioning

Number of Sites (Baseband)

• Number of Sites required based on the number of active users:

• Example:

• Assume 10000 subscribers in the area

• System bandwidth is 10MHz

• There are 600 active users per cell with FSME in RL30

• 3 sectors per site

• Share of active subscribers is 30%

• #Sites (Baseband) = (10000*0,3)/(600*3) ≈ 2

Subscribers x ShareOfActiveSubscribers #Sites =

#MaxActiveSubscribers x NoOfCellsPerSite

*Note that for FSME 3 cells per system module are assumed for all frequency bands.

For FSMD there are 3 cells per system module for 5 &10 MHz and 2 cells per system module for 15 & 20MHz

Documents

08 RA41208EN30GLA0 LTE Radio Planning Capacity GC