Wi-MAX - pub.ro › ~arusu › ABDRT › Laboratory platforms... · Laboratory – Wi-MAX Technology 1 Wi-MAX technology 1. Theoretical Introduction 1.1. WiMAX Network 1.1.1. General

Laboratory – Wi-MAX Technology

1

Wi-MAX technology

1. Theoretical Introduction

1.1. WiMAX Network

1.1.1. General Features

WiMAX (Worldwide Interoperability for Microwave Access) is a

telecommunications technology broadband wireless standard based on IEEE 802.16.

The main advantages of this technology are:

o Physical layer based on orthogonal frequency multiplexing (OFDM) scheme

offering good behavior under multipath propagation and allows operation without

direct line of sight;

o Very high transmission rates: for example, using a bandwidth of 10MHz and with

time duplexing (TDD), can be achieved, in good signal conditions, a maximum

rate of 25Mbps on the downward path;

o Adaptive modulation and coding (AMC): selection, by an algorithm, of the best

modulation and coding schemes, supportable in the existing SNR conditions in

the channel at that time;

o Automatic retransmission request (ARQ) at the link layer (level 2 OSI), for

connections requiring high reliability;

o Allocation of resources per user and per Frame in time, frequency and optionally,

in space.

1.1.2. Components of a WiMAX network

WiMAX network reference model provides a unified architecture for fixed,

nomadic and mobile communications and is based on an IP network. The WiMAX

network can logically be divided into three parts:

o Subscriber stations used by end users to access the network;

o Access service network (ASN), which consists of one or more base stations and

one or more ASN GateWays (GW). This is the radio access network. ASN GW is

located at the edge of network access services, and links to network connectivity

services (CSN).

o Connectivity service network (CSN) that provides IP connectivity and all IP

network services underlying the WiMAX network. Here is the server for

authentication, authorization and account (AAA). Here is done the IP address

allocation for subscriber stations, the QoS management, based on user

subscription type and the billing of the subscriber, among others.


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A simplification of this model is shown in Figure 1:

Reţeaua de

acces

ASN

GW Reţea IPReţeaua de servicii

conectivitate (CSN)

AAA

Gateway

Internet

Reţea IP

PSTN

3GPP/

3GPP2

ASP

SS

SS

SS

BS

BS

BSReţeaua de

servicii acces

(ASN) 3GPP/3GPP2: reţele UMTS / CDMA2000

AAA: autentificare, autorizare, conturi

ASN GW: gateway reţea de servicii acces

ASP: furnizor serviciu aplicaţie

BS: staţie de bază

PSTN: reţea comutată publică de telefonie

SS: staţie de abonat

Figure 1: Architecture of an IP-based WiMAX network

1.2. Protocol stack attached WiMAX systems

Taking as reference the OSI reference model (Open Systems Interconnection), the

802.16 standard handles the MAC sub-layer (Medium Access Control) of the level 2

(Data Link) and all of level 1 (physical), as can be seen in Figure 2:

7. Aplicaţie

6. Prezentare

5. Sesiune

4. Transport

3. Reţea

2. Legătură de Date

1. Fizic

Subnivelul LLC

(Control Legătură Logică)

Subnivelul MAC

(Control Acces la Mediu)

Subnivelul CS

(Convergenţă)

Subnivelul SS

(Securitate)

Subnivelul CPS

(Parte Comună)

Subnivelul TCS

(Convergenţă

Transmisie)

Nivelele modelului OSI

Standardul 802.16 ocupă subnivelul MAC al nivelului 2 şi întreg

nivelul 1 din modelul OSI

QPSK 16QAM 64QAM

Figure 2: Framing the 802.16 standard in the OSI reference model


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1.2.1. MAC layer

MAC layer is responsible for controlling and multiplexing of data streams from

different applications and services (HTTP, VoIP, etc.) on the same transmission medium.

The main functions of the MAC level are:

o Segmentation or concatenation of the service data units (SDU) received from

higher levels in MAC protocol data units (MAC PDU), which are creating the

blocks of the payload of the MAC layer;

o Selection of modulation schemes and transmission power level suitable for

transmitting the MAC -protocol data units;

o Retransmission of the MAC - protocol data units that have been received

erroneously by the subscriber station, when the ARQ mechanism is activated;

o Control of the quality of service (QoS) and prioritization of MAC PDUs

belonging to different data streams;

o Allocation of the resources of the physical layer (PHY) to the MAC PDU to be

transmitted;

o Offers support to higher levels for mobility management;

o Management of security and of the encryption keys;

o Offers the possibility of switching the equipment to low power consumption

modes.

The MAC layer is divided into three sub-layers:

Convergence sub-layer (CS): is responsible to receive packages, called service data

units (SDU), from the upper level, and perform on them all the operations dependent on

the type of higher level protocol. Thus, this sub-layer masks the protocol from the upper

level and its requirements in relationship with the lower MAC and PHY sublevels.

Common part sub-layer (CPS): performs on packets all operations that do not depend

on the upper level protocols, such as fragmentation/concatenation of SDU in MAC PDU,

quality-of-service control, and automatic retransmission request (ARQ).

Security Sublevel (SS) is responsible for encryption, authorization and encryption key

exchange between the base station and subscriber station.

1.2.2. The physical layer (PHY)

The physical layer of a WiMAX network is based on orthogonal frequency

multiplexing (OFDM). This scheme is very efficient for high-speed data transmission in

conditions without direct visibility and/or multipath propagation.

OFDM parameters used in WiMAX:

Parameters Fixed WiMAX

OFDM- PHY

Scalable mobile WiMAX

OFDMA -PHY


4

FFT size 256 128 512 1024 2048

Number of used subcarriers 192 72 360 720 1440

Number of pilot subcarriers 8 12 60 120 240

Number of null subcarriers/guard

interval 56 44 92 184 368

Cyclic prefix of the guard interval

(Tg/Tb) 1/32 1/16 1/8 1/4

Channel bandwidth (MHz) 3,5 1,25 5 10 20

Distance between subcarriers (KHz) 15,625 10,94

Time Symbol (μS) 64 91,4

OFDM symbol duration (μS) 72 102,9

The number of OFDM symbols in a

frame of 5 μs 69 48

In a WiMAX system, not all OFDM subcarriers are used to transmit data. Some

of them are pilot subcarriers, used for synchronization and channel estimation, another

part are guard subcarriers and the rest are data subcarriers.

1.3 The WiMAX Frame

Subcarriers may be divided into groups called sub-channels. These groups are

defined in the standard. A sub-channel represents the minimum frequency that can be

allocated to a subscriber station. By allocating different sub-channels to various

subscriber stations, the multiple access technique called OFDMA (orthogonal frequency

division multiple access) is performed. The smallest unit in time and frequency that can

be allocated to a connection is called slot. It consists of the use of a sub-channel for the

duration of one, two or three OFDM symbols, depending on the scheme used to share the

sub-channels. A contiguous portion of slots allocated to a user is called the data portion

of that user. Algorithms for allocating resources are based on user demand, quality of

service (QoS) and channel conditions.

Figure 3 illustrates the WiMAX frame structure


5

Burst DL nr.2

Burst DL

nr.1

Burst DL

nr.3

Burst DL nr.4

Burst DL nr.5

Burst UL nr.1

Burst UL nr.3

Burst

UL nr.4

Ranging

Burst UL nr.7

Burst UL nr.2

Burst UL

nr.5

Burst UL

nr.6

Pre

am

bu

l

UL-M

AP

DL

-MA

PD

L-M

AP

UL

-MA

P (

con

tinu

are

)

Numărul simbolului OFDM (timp)

Su

bp

urt

ăto

are

(fr

ecv

en

ţă)

Subframa legăturii

descendente

Subframa legăturii

ascendente

Interval de gardă

Figure 3: Structure of a WiMAX frame

As shown in Figure 3, the downlink sub-frame starts with a preamble which is

used by the physical layer for time and frequency synchronization, and for the initial

estimation of the channel. The map with the data portions allocated to each subscriber

station is contained in the MAP messages (DL -MAP and UL -MAP), which are sent to

all stations. MAP messages contain burst profiles, defining the modulation scheme and

the coding used for that link.

Uplink sub-frame consists of multiple burst from different users, and a portion

with competition -based access, used for many purposes. The main goal is ranging, i.e.

realizing frequency, time, and power corrections, in the initial phase (entry in the

network) and then periodically. Ranging channel is used by a subscriber station also to

require allocation of bandwidth on the uplink. Uplink sub-frame also contains a channel

through which the subscriber stations transmit channel quality information (CQICH) to

the base station and a channel through which the base stations transmit acknowledgments

of reception of data on downlink (ACK).


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1.4 Modulation and coding

Figure 4 shows the modulation and coding schemes supported in WiMAX system:

Downlink Uplink

Modulation BPSK modulation (optional for.

OFDMA - PHY), QPSK, 16QAM,

64QAM

BPSK, QPSK, 16QAM,

64QAM (optional)

Coding Required coding: convolutional

codes of rate 1/2, 2/ 3, 3 /4, 5/6

Optional: convolutional turbo code

of rates 1/2, 2/ 3, 3 /4, 5/6, repetitive

codes of rates 1/2, 1/ 3, 1 /6, LDPC

codes, Reed – Solomon.

Required coding: convolutional

codes of rate 1/2, 2/ 3, 3 /4, 5/6

Optional: convolutional turbo code

of rates 1/2, 2/ 3, 3 /4, 5/6, repetitive

codes of rates 1/2, 1/ 3, 1 /6, LDPC

codes.

Figure 4: Modulation and Coding Scheme in WiMAX System

Adaptive modulation and coding (AMC)

Using the CQICH channel, the base station receives from the subscriber- station

information about the quality of the downlink. For the uplink, the base station can

estimate the quality using the received data signals. Thus, taking into account the quality

of the uplink and downlink for each user, the AMC algorithm from each base station

assigns to each user a modulation and coding scheme for uplink and another one for

downlink, that will maximize the capacity of the connections for the existing signal-to-

noise-ratio of the channel at the time.

2. WiMAX equipment overview

In making an experimental WiMAX network, the following equipment can be

used:

• The sector controller AN-100U

• Radio-frequency transceiver

• A subscriber station

All these equipment are manufactured by Redline Communications. The bridge

and sector controller are indoor units, while the RF transceiver and the subscriber station

(elements between which the radio link forms) are outdoor units.

In addition, one will use cables and various RF components, such as splitters and

attenuators, since the radio connections in the lab are on cable and not throughout the air.

Also, for each device’s configuration, will use a computer connected to the unit’s

management interface.


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2.1. AN-100U sector controller

AN-100U is a sector controller. It operates at frequencies between 2-11 GHz, and

supports PTP (point to point) or PMP (point to multipoint) connectivity. AN-100U

provides QoS transfer rates’ control, on both DL/UL, thus enabling predictable transfer

rates. It uses BPSK modulation schemes, as well as QPSK, 16QAM, 64QAM and coding

rate of ½, 2/3, ¾. It also supports ARQ (automatic erroneous packet retransmission) and

encrypts/decrypts the data.

Figure 1: AN-100U sector controller

2.1.1. General description

All connectors, indicators and switches are located on the front panel of the

machine. Here are, as can be seen in the figure below, the following:

• N-type female connector, to communicate with the transceiver;

• 2 SMA connectors for time synchronization;

• LED indicators: they can indicate different problems, their description can be found in

the user manual of the equipment.

• LAN data port;

• Management LAN port;

• Management Serial port (RS-232).

Figure 2: AN-100U front panel


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The management LAN pot can be disabled, in order to configure the equipment

over the data port.

2.1.2. Configuration

Setup is done on the LAN interface; the interface has the default IP address

192.168.101.3. To connect to the equipment, use an Ethernet straight cable. The

computer’s IP address and the equipment’s address must be on the same network

(192.168.101.x).

The equipment has a web interface, accessible from Internet Explorer by entering

the equipment IP address (192.168.101.3) and the following login information username:

admin/password: admin. After successful authentication, one the left side, a general

menu appears, where various submenus can be accessed by clicking on the appropriate

lines of text.

Figure 3: AN-100U Web interface – General Menu

Each submenu’s functions are described in the table below.


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Submenu Sub-submenu Functions

Monitoring General Info View general and RF network settings

Status View radio link, data and management statistics

SS Info View system info, IP settings and active subscriber

stations statistics

Event Log View system activity and recorder error messages

Service Flow

Configuration

Service Classes Service Classes

Service Flows Service Flows

Classifiers Define classifiers for each service flow

Manage Activate service flows

Interfaces Wireless

Interface

RF PHY and MAC settings view/modification

Ethernet

Interface

Ethernet interface settings view/modification

Management IP and DHCP settings view/modification

Admin Tools Advanced

Config

RF advanced settings view/modification

Software

Upgrade

Software settings

Accounts

Management

Add users, change system password

Reboot Reboot AN-100U

We will summarize the main settings (radio frequency, IP, etc.):

RF DL Channel KHz: radio channel’s central frequency;

RF Channel Separation kHz: frequency spacing between the DL and UL

channels (for FDD);

Tx dBm Output Power: the power used for transmission by the RF transceiver;

SS Tx Power Control Enable: enables control of the SS’s (subscriber station)

power transmission in order to get a desired RSSI (Received signal strength indicator)on

UL;

RSS Reference: RSSI average value desired for the UL;

Enable Auto Rx Gain: enables automatic control of the receiver’s sensitivity;

Select MHz Band: select the type of band spreading inside the channels;

Channel Size MHz: channel’s bandwidth;

Guard Interval: cyclic prefix length;

Ms Frame Duration: Frame duration

DL Ratio: The ratio between the downlink's duration and the overall frame’s

duration;

Disable RF: disable the RF transceiver’s output;

IP Address: the terminal’s IP address;


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Subnet Mask: the terminal’s IP address’s subnet mask;

Default Gateway: the IP address of the terminal’s default gateway;

DHCP Server: the address of a DHCP server. AN-100U will forward all requests

to the server DHCP coming from subscriber stations.

In the bottom of the setup window there are three control options:

Save: Save settings;

Cancel: returns to previous settings;

Default: Restore to factory settings.

2.2. RF Transceiver

The radio transceiver is an outdoor equipment. For this reason it is locked in an

aluminum casing, resistant to weather variations and connectors are also protected in this

regard. As shown in the figure below, the transceiver is mounted on a pole together with

the antenna.

Figure 4: RF Transceiver


The radio transceiver has only two ports:

IF port (intermediate frequency) – N-type mother jack, and only through this port,

the transceiver:

o Send/receive data modulated with the intermediate frequency (of) the

indoor terminal (AN-100U)

o Send status information to the indoor unit


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o Get control information from the terminal

o Get power supply from the terminal

RF port (radio-frequency) is also an N-type mother jack, and is used by the

transceiver to send/receive the radio signal(s) to/from the antenna. In the

experimental laboratory platform, this port will be connected to a coaxial cable,

then will connect various radio frequency components (attenuators, splitters) and

finally, at the other end, will be connected subscriber station.

2.3. Subscriber’s station

The subscriber station is an outdoor equipment. For this reason it is closed and in

an aluminum casing resistant to weather variations. As shown in the figure below, the

station has a mounting bracket and the power cable is PoE-type. Also, through this cable,

occur data and management traffic. The station is designed to operate at frequencies

between 2-11 GHz, in PTP and PMP configurations. It supports modulation schemes

such as BPSK, QPSK, 16QAM, 64QAM and coding rates of ½, 2/3, ¾, ARQ mechanism,

QoS, among others.

Figure 5: The subscriber’s station


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The subscriber station has an integrated antenna, an Ethernet connector for power

supply, an N-type female RF Connector, and grounding.

2.3.2. Configuration

The equipment’s configuration is available over the LAN interface, using the

Telnet protocol, the default IP address is 192.168.101.1. Once the BS connection is

established, configuration can be done on the WAN interface.

To connect to the equipment, one has to use an Ethernet crossover cable, from the

computer’s interface, and use an address on the same network as the equipment

(192.168.101.x). When connecting, the user will be prompted login information (Login:

super/Password: super).

After logging, the station's command prompt appears, where you can enter

commands. The command line has the autocomplete function (by pressing TAB) and

command history (clicking↑ and ↓) and help (?).

Commands can be divided into categories, and the command prompt changes

depending on the level at which we find ourselves in the tree order. Eg: RPM#>

RPM#>rfconfig

RPM(rfconfig ->)#>

We summarize the main commands, which helps setting/viewing RF, PHY, IP

parameters:

rfconfig show: Radiofrequency display settings. An example of output of this command

is given below:

Settings --- <<SS Mmgt RF Configuration Parameter>>

Transmit Receive

---------------------------------- ----------------------------------

FixedPower:............10.00 dBm Gain:...................0.00 dB

ActualPower:............1.60 dBm RfRssi:.................0.00 dBm

Lock:......................0 Lock:......................0

FixedGain:.................0 Agc:.......................0

Frequency Others ---------------------------------- ----------------------------------

LoRfFreq1:...........2680000 kHz RfTemp:.................0 Celsius

HiRfFreq1:...........2680000 kHz MaxRngRetries:............10

Priority1:.................0 StickinessTimer:..........30 sec

LoRfFreq2:.................0 kHz MaxTxPower:............27.00 dBm

HiRfFreq2:.................0 kHz Nomadic:.........Disabled(0)

Priority2:.................0

LoRfFreq3:.................0 kHz

HiRfFreq3:.................0 kHz

Priority3:.................0

LoRfFreq4:.................0 kHz

HiRfFreq4:.................0 kHz

Priority4:.................0

LoRfFreq5:.................0 kHz


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HiRfFreq5:.................0 kHz

Priority5:.................0

LoRfFreq6:.................0 kHz

HiRfFreq6:.................0 kHz

Priority6:.................0

LoRfFreq7:.................0 kHz

HiRfFreq7:.................0 kHz

Priority7:.................0

LoRfFreq8:.................0 kHz

HiRfFreq8:.................0 kHz

Priority8:.................0

LoRfFreq9:.................0 kHz

HiRfFreq9:.................0 kHz

Priority9:.................0

LoRfFreq10:................0 kHz

HiRfFreq10:................0 kHz

Priority10:................0

LoRfFreq11:................0 kHz

HiRfFreq11:................0 kHz

Priority11:................0

LoRfFreq12:................0 kHz

HiRfFreq12:................0 kHz

Priority12:................0

LoRfFreq13:................0 kHz

HiRfFreq13:................0 kHz

Priority13:................0

LoRfFreq14:................0 kHz

HiRfFreq14:................0 kHz

Priority14:................0

LoRfFreq15:................0 kHz

HiRfFreq15:................0 kHz

Priority15:................0

LoRfFreq16:................0 kHz

HiRfFreq16:................0 kHz

Priority16:................0

RfFreq:..............2680000 kHz

As shown, there are 16 frequency intervals for the SS to scan in order to to find a

network. These commands are user configurable, using commands such as:

rfconfig set LoRfFreq1 2580000

rfconfig set HiRfFreq1 2600000

rfconfig set LoRfFreq2 2630000

rfconfig set HiRfFreq2 2640000

.................

rfconfig set LoRfFreq16 xxxxxxx

rfconfig set HiRfFreq16 xxxxxxx

If LoRfFreqX and HiRfFreqX are configured with identical values, the SS scans

only that frequency. In the example above, one frequency has been set, since LoRfFreq1

and HiRfFreq1 have the same value, while the remaining intervals are not configured.

rfconfig set txFixedGain 1: sets the SS transmission gain to a fixed value.

rfconfig set txFixedPower x: sets the above gain to a value which achieves a x

dBm transmission power.

rfconfig set txFixedGain 0: sets the tranmission gain to be controlled by the BS.


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interface wman0 show phy: displays PHY settings. An output example is shown

below:

Settings --- <<SS Mmgt PHY Configuration Parameter>>

Bandwidth= 5000 kHz

FftSize= 512

CyclicPrefix= 8 PS

FrameSize= 5000 usec

These parameters can be configured using the following commands:

interface wman0 set phy bandwidth x: sets the bandwidth. Possible values for x are

5000, 7000, 8750 and 10000 (KHz). With this parameter changes automatically and FFT

Size, as follows:

Bandwidth FftSize

5000 512

7000 1024

8750 1024

10000 1024

interface wman0 set phy framesize x: sets the WiMAX frame length. Possible values

for x are 5000 and 10000 (us).

interface eth0 show ip: displays IP settings.

interface wman0 set ip address xxx.xxx.xxx.xxx: sets the station’s IP address.

interface wman0 set ip mask xxx.xxx.xxx.xxx: sets the station’s IP mask.

status show: displays statistics about the link quality (RSSI, PCLNR, packets

sent/received, number of errors HCS/DL CRC). An example of the output of this

command is given below:

Settings --- <<SS Mmgt Status Data>>

Downlink General Uplink General

----------------------------------- -----------------------------------

fpCount:....................0 MapCount:...................0

fpErrCount:.................0 MapErrCount:................0

fpCrcCount:.................0 MapCrcCount:................0

MapCount:...................0 ByteCount:..................0

MapErrCount:................0 SduCount:...................0

MapCrcCount:................0 MpduCount:..................0

ByteCount:.........1621934196

SduCount:.............1577757

MpduCount:..................0

HCrcErrCount:...............1

CrcErrCount:................3

Management Downlink Chan Desc

----------------------------------- -----------------------------------

RxCount:...............541516 RxCount:....................0

ErrCount:...................0 ErrCount:...................0

CrcCount:...................0 CrcCount:...................0

ChangeCount:.............2591


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Uplink Chan Desc Others

----------------------------------- -----------------------------------

RxCount:.................2591 Rssi:...................-72.6

ErrCount:...................0 Snr:.....................35.2

CrcCount:...................0 FreqOffset:..............2609

TCnt:.......................0

ModemResets:................0

LostFrames:.................0

FrameDuration:..............0

RngTimeCorrection:..........0

TotalHCrcErrors:............0

TotalCrcErrors:.............0

TotalTxBurstCount:..........0

TotalRngReqCount:...........0

TotalBwReqCount:............0

TotalMgmSentCount:......10371

TotalPaddingCount:.1318473221

RfRssi:.................-72.6

TxPower:.................16.0

LinkStatus:.................1

exit: jumps to a previous level in the commands’ tree. Example: RPM#>

RPM#>interface

RPM(itf)#>wman0

RPM(itf:wman0)#>exit

RPM(itf)#>exit

RPM#>

3. Practical activities

The equipment described above will connect as follows:

The sector controller will be connected with the transceiver through a coaxial

cable from the controller’s N type signal jack to the transceiver’s IF jack.

The transceiver will be connected to the splitter via a coaxial cable attached to the

RF jack.

At the splitter’s other jack will be connected the subscriber station, using two

attenuators of 30 + 10 = 40 dB and a coaxial cable.

The sector controller will be powered from the 220 power-line via a power cable.

The subscriber station will also be powered from the main 220V AC line via the

power-over-Ethernet adaptor, using a power cord and a straight network cable for

outdoor. This network cable connects to the adaptor’s “Data-and-power” jack.

The sector controller connects to PC 1, using a straight-type network cable, from

the controller’s “Data” jack.

The subscriber’s station connects to PC 2 using a cross-over-type network cable,

from the power-over-Ethernet adaptor’s “Data” jack.

To configure the sector controller first check PC1: Control Panel-Network

Settings that PC1's IP family is 192.168.101.xxx. Then open a web browser window (eg.

Internet Explorer or Mozilla) on PC1 and access the appropriate page of the controller IP

address (192.168.101.3).


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In order to authenticate, use User: 'admin', Password 'admin'. After authentication,

the user has the possibility to modify the operating parameters of the Controller. Students

can change them, but must not save them, so when restarting the Controller, to return to

the original settings.

To study the WiMAX network’s performances, we use the Jperf program, both on

PC1 and PC2. For this, we set Jperf, turned on PC1, which is connected to the controller

sector, to act as server. Then we set Jperf, turned on PC2, which is connected to the

subscriber station, to act as customer. Also, in this window, we will write the server’s IP

address, i.e. PC1’s IP address.

To generate data traffic between two PCs via WiMAX network, select on PC2

Jperf’s window a transmission time of 20 seconds and choose TCP traffic. Traffic will

start between the two PCs after the Run option is selected in both windows. We will

observe the throughput offered, which is a transfer rate metric.

Next, we will perform several sets of measurements obtained with Jperf, in order

to complete the table below. The transfer rate is displayed in real time in Jperf’s center

console.

To activate a service class, activate only the two service flows associated with that

class. These two streams are uplink and downlink. The other flows defined in the list

must be disabled.

To change the power output of the controller, enter the Wireless Interface menu:

Tx Power.

To find the type of modulation used by the Controller, choose Monitoring-SS Info.

Scenario no. Service

Class

Suma

atenuatoarelor

[dB]

Controller’s

transmission

power

Transfer

rate

Modulation

and Coding

1 Class 1 40 0

2 Class 2 40 0

3 Class 3 40 0

4 Class 3 70 0

5 Class 3 80 0

6 Class 3 90 0

7 Class 3 100 0

Indicate in the table the maximum attenuation at which network traffic still occurs.

4. Preliminary questions

1. Enumerate the components of the WiMAX access network.

2. Describe the subcarrier types used in the OFDM modulation by the WiMAX

technology.

3. Explain two functions of the medium access control (MAC) sublevel of the WiMAX

technology.

Wi-MAX - pub.ro › ~arusu › ABDRT › Laboratory platforms... · Laboratory – Wi-MAX Technology 1 Wi-MAX technology 1. Theoretical Introduction 1.1. WiMAX Network 1.1.1. General

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