radio network simulation - commsys.isy.liu.se · amplitude, phase, and angle (at tx and rx side)...

RADIO NETWORK SIMULATION

Niclas WibergEricsson Research

Radio Network Simulation 2011-09-012

Outline

Simulator overview– What is radio network simulation?

Models– The radio environment

Deployment & mobilityPropagation

– Physical layer– Protocols– Traffic

Radio resource management

Simulation methodology


Wireless Communication Simulation

Traditional network simulators– ns-2, ns-3, OPNET, OMNET++– Focus on the network and its protocols– Large networks (many hosts)– Wireless modules are available

Wireless link simulators– COSSAP, proprietary, ...– Radio propagation, signal processing– One or a few links

Radio network simulators– Mostly proprietary– Many transmitters and receivers– Focus on radio resources


What is Radio Network Simulation?

“Simulating performance in terms of coverage, capacity and quality in a multi-cell system”

environment deployment

mobility & trafficalg. parameters

...

Radio Network Simulator

transmit powerinterferenceerror rates

...

throughputservice qualityblock ratedrop rate...


Radio Network Simulation

Mobility Deployment

Internet Protocols

Radio Protocols

Propagation & Fading

Physical Layer

RRM

Application Traffic

TransportNetwork


Deployment, Mobility and Propagation

G = Gd + Ga + Gs + Gm

distance attenuation

antenna gain shadow

fading

multipath fading

Mobility Deployment

Internet Protocols

Radio Protocols


Physical Layer

RRM

Application Traffic

TransportNetwork


Deployment Models

Uniform hexagonal site placement

Wrap-around at borders

Typical network sizes– 7 sites, 21 cells– 12 sites, 36 cells


Mobility Models

Creation distribution– uniform– mixed gaussian– roads

Movement– random walk– roads

Important for– fading dynamics– handover frequency


Propagation Models

Slow part, average pathgain– Okumura-Hata G = -29.03 - 35.2 log10 d [dB]– Directional antenna gain– Log-normal shadow fading

Fast part, multipath fading– Channel time impulse response with independent Rayleigh-

fading rays– Transformed to frequency domain for OFDM physical layer

models


Propagation ModelsExample: Average Pathgain

-160

-150

-140

-130

-120

-110

-100

-90

-80

-70

-2000 -1000 0 1000 2000

-2000

-1000

0

1000

2000-2000 -1000 0 1000 2000

-150

-140

-130

-120

-110

-100

-90

-80

-70

distance [m]

path

gain

[dB

]

distance [m]

distance [m]


Propagation ModelsExample: Single-Carrier Multipath Models

0 2 4 6 8 10

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5-20

-15

-10

-5

0

5

10

0 1 2 3 4 5-20

-15

-10

-5

0

5

10

ITUPedestrian A

3GPPTypical Urban

Mean ray powers Fast fading gain

[m]

[m]

distanceRay delays


Propagation ModelsExample: Multi-Carrier Multipath Models

ITU Pedestrian A 3GPP Typical Urban

Distance [m]

Sub

band

[M

Hz]

0 0.2 0.4 0.6 0.8

2

4

6

8

10

12

14

16

18

20

-10

-8

-6

-4

-2

0

2

4

6

8

10

Distance [m]

Sub

band

[M

Hz]

0 0.2 0.4 0.6 0.8

2

4

6

8

10

12

14

16

18

20

-10

-8

-6

-4

-2

0

2

4

6

8

10


-1000 -500 0 500 1000

-1500

-1000

-500

0

500

1000

1500

1

2

3

4

5

6

7

Ray-Based Spatial Channel Models

Radio channel modeled by a multitude of rays

Each ray is characterized by a delay, amplitude, phase, and angle (at tx and rx side)

Example– A link is modeled by 120 rays (6

groups of 20 rays each)

Ray-based spatial channel models are e.g.:

– 3GPP SCM [1]– WINNER channel models [2], [3]


MIMO Channel Model Example- SCME (suburban macro), BS ant. spaced 10 λ, UE ant. spaced 0.5 λ


Physical Layer Models

Receivermodel

BLER(Error probability)

Mobility Deployment

Internet Protocols

Radio Protocols


Physical Layer

RRM

Application Traffic

TransportNetwork

p1

∑≠

+=

ikkk

iii pGN

pGSINR

p2

p3

G1

G2

G3


Physical Layer ModelsReceiver Model

InputReceived signal quality (SINR)Often multiple values

– Time slots– Frequency subbands

Internal representationReceived Bit Information

– Shannon’s channel capacity

OutputBLER (block error probability)

Decoder model

Linear average

...

Received BitInformation

Demodulator model

SINR

...

Received BitInformation Rate

Block ErrorProbability

-20 -10 0 10 20 300

1

2

3

4

5

6

SINR [dB]

Rec

eive

d B

it In

form

atio

n pe

r S

ymbo

l

QPSK

16QAM64QAM

0 0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

Received Bit Information Rate

Blo

ck E

rror

Pro

babi

lity

Length 100, Rate 0.25

Length 100, Rate 0.75Length 5000, Rate 0.25

Length 5000, Rate 0.75


Protocol ModelsDifferent Detail Levels

Ignore protocols

Simple bit counting models

Detailed modeling of protocol operation

Radio

MAC

RLC

PDCP

IP

TCP/UDP

Application

Radio

MAC

RLC

PDCP GTP-u

UDP

IP

Ethernet

GTP-u

UDP

IP

Ethernet

IP

TCP/UDP

Application

IP

Terminal Base station Gateway Server


Protocol Models ExampleARQ Protocol

Ignore protocols– Model BLER, calculate throughput = (1 – BLER) × bitrate

Simple model– txbuf: number of bits in transmitter buffer– Transmission: txbuf = txbuf – blocksize– Block error: txbuf = txbuf + blocksize (after a delay)

Detailed model– Create data structures for protocol data units (PDUs)– Keep lists transmit & retransmit buffers– Model status reports (feedback) in detail– Implement timers & state variables– Etc...


Detailed ARQ Models (WCDMA)

SDU buffer

Service Data Units (SDUs) to be transmitted

Retransmission buffer

Transmitted Protocol Data Units (PDUs)

Reception buffer

SDU reassembly

Delivered Service Data Units (SDUs)

Received Protocol Data Units (PDUs)

Concatenation/segmentation

Status generation

Channel

Status reception


Traffic Models

User & session models– Often session = user– Random arrival and

lifetime– Fixed number of users

Example applications– Full buffer– Speech with activity

model– Web surfing– Streaming

Mobility Deployment

Internet Protocols

Radio Protocols


Physical Layer

RRM

Application Traffic

TransportNetwork


Traffic Models: Speech with Activity Model

time

Uplink source

rate

12.2 kbps

time

Downlink source

rate

12.2 kbps

Exponentially distributed activity time


Traffic Models: Web Surfing

Example model

Random page requests

Log-normal page size distribution

Exponential readingtime

TCP flow control

0 5 10 15 20 25 30 35 40 45 500

50

100

150

200

250

time [s]

[kby

tes]

Cumulative data flow

requested arrived in network


Radio Resource Management

Link adaptation

Scheduling

Power control

Handover

...

Mobility Deployment

Internet Protocols

Radio Protocols


Physical Layer

RRM

Application Traffic

TransportNetwork


Radio Resource ManagementExample: Channel-Dependent Scheduling

Shared channel transmission

HSDPA & EDGE:Select user and data rate based on instantaneous channel quality

– Time-domain schedulingdata1data2data3data4

TimeFrequency

User #1 scheduled

User #2 scheduled

1 ms

180 kHz

Time-frequency fading, user #1

Time-frequency fading, user #2

LTE: Scheduling in time and frequency domain

Time

User 1 User 2


0 5 10 15-20

-15

-10

-5

0

time [s]

Ec/N

0 [dB

]

cell 1cell 2cell 3

Radio Resource ManagementExample: WCDMA Handover

Measurement models– Simple: average pathgain– Detailed: filtered

multipath

Handover events– add/delete/replace

Apply admission control for new links

delete 1

add 2

replace 2→3


Simulation MethodologyDetermining Capacity

InputPropagation and network deploymentUser mobility and trafficAlgorithms and parameters

OutputUser quality

– Throughput, delay, frame loss, dropped calls

System utilization– throughput– transmitted and received

power

Increase traffic load until service quality is too low

or, with admission control

Ensure that all (or most) users achieve target quality

– block new service requests when necessary to protect present users

Increase traffic load until blocking rate is too high


Simulation MethodologySpeech Capacity

User generation– Random arrival process, or– Fixed number of users

Monitor user quality– Blocking and dropping– Frame loss/drop

Increase #users until less than e.g., 98% are satisfied

Optimize algorithm parameters


Simulation MethodologyPacket Capacity

Random user arrival and packet request process

Monitor– system throughput– user quality, e.g. packet

bitrate

Increase load– until quality drops below

target– until it flattens out

0 10 20 3 0 40 500

10 0

20 0

30 0

40 0

50 0

60 0

0 10 20 3 0 40 500

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 010% b est median 10% wors t

Number of users per cell

Packet bitrate[kbps]

Cell throughput

[kbps]


Summary

Multiple cells, multiple users

Radio Propagation

Physical layer models

Protocol models

Traffic models

Radio resource management

Simulation methodology

Mobility Deployment

Internet Protocols

Radio Protocols


Physical LayerRRM

Application Traffic

TransportNetwork


radio network simulation - commsys.isy.liu.se · amplitude, phase, and angle (at tx and rx side)...

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