Bcl Wimax Training Doc v1

Banglalion Communications Ltd. Training Doc

Introduction of WiMAX

WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is a wireless digital communications system that is intended for wireless "metropolitan area networks". This technology can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations.

How WiMAX Works?

The WiMAX network uses an approach that is similar to that of cell phones.

Coverage for a geographical area is divided into a series of overlapping areas called cells. Each cell provides coverage for users within that immediate Area. When subscriber travels from one cell to another, the wireless connection is handed off from one cell to another.

A WiMAX system consists of two parts:

A Base station, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles (~8,000 square km).is mounted on a tower or tall building to broadcast the wireless signal.

A WiMAX subscriber device, these could be WiMAX enabled notebook, mobile Internet device (MID), or even a WiMAX modem by using the subscriber receives the signals. Currently we have the dongle, indoor unit and outdoor unit.

Need to show the Laptop connected to the internet

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Canada2.3/2.5GHz3.5/5GHz

USA1.5/2.3GHz2.5/5GHz

C & SA2.5/3.5GHz

5GHz

ME & A3.5GHz5GHz

Europe3.5GHz5GHz

Russia2.3/2.5/3.5GHz

5GHz

Asia Pacific2.3/3.3/3.5GHz

5GHz


The user pays the service provider for wireless Internet access, just as they would for a normal Internet connection via a cable network. The service provider provides the end user with the CPE, software, an userid and a password.

If the CPE at the user end catches the signals, an uninterrupted internet connection will be established as long as the signal is available. One WiMAX base station can send signals over distances of several miles depending on the terrain. The more flat the terrain, more the coverage area. If end user moves from one base station to another, your laptop receiver will hook up to the other base station (of the same service provider) with a stronger signal.

Radio Frequency Spectrum:

We are using the radio frequency 2.5 GHz which is a 35 MHz spectrum and the range is from 2585—2620 MHz.

Usage of Radio Frequency in WiMAX Network:

If we see the available usage of RF frequency all over the world in respect to WiMAX we can see WiMAX basically high RF frequency which nature is more likely Microwave frequency.

Figure 02: Worldwide RF frequency in WiMAX Technology

Some RF Parameters Related with WiMAX :

We can check the status of Air interface or Um interface by checking some parameter at the user end which are:

Receive Signal Strength Index (RSSI): This is the parameter which basically indicates the strength of signal which comes from WiMAX BTS.

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Usually RSSI is good for near to the BTS and getting worst if we go away from the BTS. Sometimes it is bad even if we are near to BTS as because of blockage.

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Figure 03: RSSI strength of a Telecom Network

The above picture shows MS B is getting poor signal than MSA as because of large distance from BTS/Tower. In technical language it is called “Path Loss”. Sometimes we may experience different scenario, for example we may get poor signal even if we are very close to BTS. Refer to the picture below:

Figure 04: MS is getting poor signal

In the above picture there is an wall or blockage in between BTS and MS, so it’s getting poor signal. As a result RSSI will be poor for this MS.

RSSI Unit: Usually we defined this parameter in dB. Its value is always negative. So the value tends to zero is better. For example if RSSI of MSA is -60dB and MS B is -85 dB so MS A is in better condition. This value can not be zero. Maximum RSSI value can be up to -30 dB and in worst case RSSI can be up to -120 dB.

Carrier to Interference and Noise Ratio (CINR): The name indicates it is an ratio. So mathematically we can write:

CINR = Carrier (Our desired WiMAX signal)/ (Noise (System Noise)+Interference (Either external or internal)) This is another parameter by which we can measures the signal status or quality. The main challenge in WiMAX technology is interference. So the RF engineers try to minimize this interference as much as possible.

This value is not depending on the BTS position as like RSSI but it depends on Radio planning, external illegal users.

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CINR Units: This parameter is unit less as because its an ratio. The CINR is better if its value is greater. For example: CINR of MS A with 20 is better than CINR of MS B 10. The greater the value the better it is. This value is up to 40. But the minimum value for WiMAX service is at least 10. WiMAX CPE or MS still sometimes work under CINR value 10 but that one is not guaranteed service.

In summary, we have to check the combined RSSI and CINR value to have the status and quality of signal. Both parameters should be in acceptable range for better service.

MS (CPE/ USB Modem) Antenna Parameter:

At present we are providing multi vendors CPE and MS to our end users/ Subscribers. The CPE which we usually provide are:

Dongle / USB Modem;Indoor CPE;Outdoor CPE;

Subscriber can’t buy any CPE from the free market. The subscriber has to choose one from the tested one that we are providing.

Furthermore, the antenna which is inbuilt of these types of CPEs is different.

Dongle / USB Modem: It is small and can use it with our laptop or desktop. The antenna gain of this type of USB modem is only 2 dBi. It is suggested to use this type of USB modem in good radio condition (for example: RSSI>= -75; CINR>= 15)

Figure 05: USB Modem

Indoor CPE: This type of CPE usage in indoor as it name indicates. The main difference in between USB modem and indoor CPE is the antenna gain (which is 4 to 6 dBi) higher than USB modem and need external power source to run this modem as well as one Ethernet cable if no built-in Wi-Fi.

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Figure 06: Indoor CPE

It can work with poor radio condition than USB modem. We suggest to use this type of modem placing near window.

Outdoor CPE: This is very similar with indoor CPE but the name indicates that this type of CPE placed in outdoor (maybe wall mounted). The antenna gain is higher than indoor CPE (above 10 dBi). As the antenna gain is high it is capable to work in poor radio condition. Typical scenario is it is used in village or used in place where radio signal is poor.

Figure 07: Outdoor CPE

So, in WiMAX network there are several types of users using several types of CPEs in different radio signal status.

Figure 08: Different types of CPEs in a WiMAX network

Typical Coverage Radius with Respect to Various Clutters:

In Bangladesh the clutter (Area Scenario) is not the same all over the country. Some areas are highly dense (for ex: City area), some are less dense (for ex: thana, upozilla) and some are in almost flat area (for ex: village area). The coverage also varies with respect to this clutter definition.

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Figure 09: Typical CPEs usage for different clutter

WiMAX Base Station:

In WiMAX technology one site has three antennae and each Antennae has one WBS (Wireless Base Station). This type of naming is vendor dependent. For Alcatel it is WBS where as in other vendors (ZTE or Huawei) they are called RRU (Radio Receiving Unit) in each sector. But three antennas in one site is the unique configuration. Rarely some of the sites may have two sectors (two antennae).

Conclusion

In summary Radio part is not as smooth as like other part of WiMAX network. This document is just having an idea or overview of Radio part of WiMAX technology. In reality the scenario is much more complex and complicated.

Core Network

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There are different network elements in the core network and those are AAA, switch, Router, HA etc.

What is 8950 AAA?

8950 AAA (Authentication Authorization Accounting) is a carrier class RADIUS / Diameter server widely deployed in many Service Providers, to do the AAA of any type of access technology (dial-up, xDSL, VPN’s with IPsec, GSM/GPRS/UMTS, CDMA2000/EVDO, WiFi, etc.).

What Is Radius?

RADIUS (Remote authentication) was originally created to authenticate PPP (Point-to-Point Protocol) switched users connecting to IP networks via dial-up, in a centralized way. In fact, it stands for Remote Authentication DIal-up User Service.

However, it has evolved a lot since then, and has become the authentication standard for any other access technology: xDSL, GPRS/UMTS, CDMA2000/1xEVDO, IPsec with IKEv1&IKEv2, etc. And also for access over Ethernet (802.1X) including Wi- Fi and Wi-Max.

RADIUS client (WAC, Home Agent… in WiMAX), which is usually the access device that provides IP connectivity to users. This Network Access Server is also known as NAS in RADIUS terminology.

RADIUS server, which is a central repository of user authentication information and user profiles, that based on some configuration, decides to authorize the user into the network and how.

Authentication types

Authentication has several purposes in a WiMAX network:

1. Verify the user trying to connect (user authentication), to validate that (s)he really belongs to that Network Service Provider to connect in that network (NSP) and can be billed for the connection and access the company intranet (orIP network),

2. For the user to verify that (s)he connecting to the correct network, and not to a hacker’s network (network authentication)

3. Optionally, device authentication. To verify the device (handset, CPE, PCMCIA card, etc.) identity (Ethernet MAC address) is valid and hasn’t been modified or tampered with. Based on this device ID (MAC) it can be decided to authorize that device into the network if it is not in a black listed (hasn’t been stolen, for instance).

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These air interface encryption keys are dynamically generated between the user and the AAA (RADIUS) server when the user starts the session. But in order to have the best possible security, these keys should be dynamically changed. This imply doing a user re-authentication periodically (every 30 min, every hour, etc.). This

EAP Overview

EAP (Extensible Authentication Protocol) itself is only a framework to be able to transport authentication information between the EAP supplicant (the user) and the EAP server (the AAA=RADIUS server).

Figure 14.- Elements in an EAP authentication

The authenticator is the element that will prompt the user to be authenticated, and will encapsulate any EAP message coming over Ethernet into RADIUS, and vice versa.

The advantages of EAP are:

End-to-end authentication, between the user and the final AAA server. Even if there are proxy-radius servers in between, they won’t be able to know about the user’s credentials.

The EAP authenticator (the WAC for WiMAX) doesn’t have to understand the authentication mechanism used (EAP-TTLS, EAP-AKA, etc.), and even if in the future new EAP methods arise, it won’t need to be modified to understand it.

The 1st message in any EAP exchange is an EAP-Identity where the user provides an Identity in the form of NAI (Network Address Identifier), made up of:

NAI = <identity>@<realm>

The realm is the network Identifier where this user is registered, and is used between RADIUS servers to proxy the RADIUS request to the correct AAA server in case of roaming.

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EAP-TTLS

It is a method, derived from EAP-TLS, to establish a secure communication tunnel between the user (EAP supplicant) and the home RADIUS server (H-AAA), to later transmit the user’s login & password (subscription credentials) in an encrypted manner.

It also provides mutual authentication, as the user knows (s)he is connecting to the right network because the AAA server provides an X.509 digital certificate, usually issued by the WiMAX Forum®.

Optionally, it can also authenticate the device, in case the device has a digital certificate issued by the device manufacturer.

Figure 15.- General authentication diagram with EAP-TTLS

As the 1st message is always the EAP-Identity which travels un-encrypted, it is recommended for the EAP-supplicant to generate a random 32-digit hex pseudonym(or longer) as use it for the EAP-Identity. The actual login (User-Name) will be provided to the AAA server encrypted inside the EAP-TTLS secure tunnel, so that the AAA server can retrieve the user password and profile from the provisioning DB.

In WiMAX, the EAP-TTLS version used is the 0.6, and the inner method used to authenticate the user by login/password is MS-Chap-V2.

This EAP-TTLS/MsChapV2 is currently the most common authentication method in WiMAX, as most of Service Providers subscribers are identified by login/password, and all non-Service Providers networks (employees of a company, etc.) are also authenticated in the same way. However, also PAP and CHAP can be used to provide the login/password information to the AAA server inside the EAP-TTLS tunnel.

As an example, next there is a screenshot from an EAP-TTLS supplicant, showing that:

It supports putting a different User-Name inside the TTLS tunnel, than the EAP- Identity for outside of the TTLS tunnel (should be at least a random 32-digit Hexadecimal number, to comply with the standards)

It supports different authentication methods inside the TTLS tunnel: PAP, CHAP & MsChapV2

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Figure 16.- Screenshot from an EAP-TTLS supplicant for a PCMCIA card

Due to the digital certificate verification, which involves very complex cryptographic operations, EAP-TTLS is very CPU intensive, both in the EAP server and the EAP supplicant. As the EAP server has to authenticate several users in parallel, this CPU issue can be a bottleneck in the AAA server.

As the users have to re-authenticate periodically (30 or 60m) to verify the user is still there and to generate new keys to encrypt the session traffic in the air interface(PKMv2), EAP-TTLS provides a session-resumption mechanism. Basically, during the1st EAP-TTLS full authentication, the EAP server and the EAP supplicant generate a session key, which can be used for the next re-authentications, so that the authentication can take place without the exchange and verification of the X.509 digital certificate(s).

This session resumption is very advantageous for the AAA server, as the CPU usage is reduced, but the EAP supplicant must also support it to take full advantage of it. It not, a full authentication will have to take place as in the 1st authentication of the session.

EAP-TLS

EAP-TLS (Transport Layer Security) is a mechanism that provides mutual authentication (the EAP server authenticates before the EAP supplicant, and the Supplicant before the user) based on having each peer an X.509 digital certificate.

In this case, there is no login/password, and the subscription is not associated to a person (login) but to the device itself. The EAP-Identity used will be the device MAC address (without dashes).

Figure 17.- General authentication diagram with EAP-TLSTypical uses for EAP-TLS might include:

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Temporal access to a WiMAX network from the user’s device, usually paying in advance to having the service. Typically in an airport or fair via a web portal

Satellite TV STB (Set Top Box), where the return channel is via WiMAX instead of via dial-up modem.

Rental of CPE/USB dongles, where the user pays both for the service and for the device

Remote measuring devices spreaded across the country, and the measuring company has the list of provisioned MAC address.

In these cases, the device must have the MAC address inside the digital certificate, that guarantees the authenticity of that MAC address and that it hasn’t been hacked. The typical certification authority will be the WiMAX Forum®, which will issue sub-CA certificates to the manufacturers.

There can even be another case where there is no subscription neither by login/password nor by device; anonymous access for free. In this case, the digital certificate subject (the MAC address) is not validated to be in a list of paying/allowed MAC addresses, and even the device could not provide a digital certificate.

This type of access is used for On-Line Subscription (OLS). The user connects initially to the WiMAX network of the NSP, but can not access the Internet, only a subscription portal to register initially in the network, and paying a fee for the access. In that subscription portal, the user will auto-register and will associate the money paid

to a MAC address for authenticated EAP-TLS access, or login/password for EAP-TTLS access, without any limitation on which device to use to

connect from.

In this case, the device will indicate it doesn't want subscription authentication because the user wants to do On-Line Subscription, by prefixing the Identity with{sm=1}. The rest of the identity is the device MAC address, and the realm indicates to which NSP the user wants to subscribe to:

{sm=1}<MAC>@<NSP realm>

Summary of EAP methods and the authentication types they are valid for

The following table tries to make a summary of the different authentication types that can be used in WiMAX.

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AAA Service Profile

For providing Video on Demand, DATA, VOICE, VIDEO, VPN, Video Conference we can use following service profile type.

Best Effort (BE)BE delivery describes a network service in which the network does not provide any special features that recover lost or corrupted data. By removing the need to provide these services, the network operates more efficiently.

Real Time Polling Service (rtPS)rtPS concerns QoS services, and supports real-time flows that generate variable size data packets on a periodic basis (MPEG) and offers periodic unicast request opportunities. The CMs specify the size of the desired data grants.

UGS - Unsolicited Grant ServiceUGS is a QoS indication employed on the R1 RP of a WiMAX network which indicates that the air interface traffic will have low latency requirements eg VoIP

Extended real time Polling Service (ErtPS)ErtPS applies to QoS services. It supports real-time flows that generate variable size data packets on a periodic basis (MPEG) and offers periodic unicast request opportunities. The CMs specify the size of the desired data grants. This service supports silence suppression.

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Non real time Polling Service (nrtPS)nrtPS concerns the QoS services. It supports flows that require variable size data grants on a regular basis (high bandwidth FTP) and offers infrequent unicast polls plus contention and piggybacking.

Work Flow

Feb 2009 8950AAA WiMAX Guide for ALU W4 13

In this case, the WAC receives all user IP information via RADIUS. When the WAC receives the DHCP Discover message from the user, instead of doing a relay to a DHCP server, it will answer the message directly with the information provided by the AAA server. This way of behaving is know as “DHCP proxy” instead of “DHCP relay”.

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Introduction to Domain Name System (DNS):

The DNS is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various informations with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. An often used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, www.banglalion.com.bd.com translates to 180.149.31.2.

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed, fault tolerant, and helped avoid the need for a single central register to be continually consulted and updated.In general, the Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.

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Introduction to DHCP

Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway. RFCs 2131 and 2132 define DHCP as an Internet Engineering Task Force (IETF) standard based on Bootstrap Protocol (BOOTP), a protocol with which DHCP shares many implementation details. DHCP allows hosts to obtain necessary TCP/IP configuration information from a DHCP server.

Benefits of DHCP

Reliable IP address configuration. DHCP minimizes configuration errors caused by manual IP address configuration, such as typographical errors, or address conflicts caused by the assignment of an IP address to more than one computer at the same time.

Reduced network administration. DHCP includes the following features to reduce network administration:

o Centralized and automated TCP/IP configuration.o The ability to define TCP/IP configurations from a central location.o The ability to assign a full range of additional TCP/IP configuration values by

means of DHCP options.o The efficient handling of IP address changes for clients that must be updated

frequently, such as those for portable computers that move to different locations on a wireless network.

o The forwarding of initial DHCP messages by using a DHCP relay agent, thus eliminating the need to have a DHCP server on every subnet.

Why use DHCPEvery device on a TCP/IP-based network must have a unique unicast IP address to access the network and its resources. Without DHCP, IP addresses must be configured manually for new computers or computers that are moved from one subnet to another, and manually reclaimed for computers that are removed from the network.

DHCP enables this entire process to be automated and managed centrally. The DHCP server maintains a pool of IP addresses and leases an address to any DHCP-enabled client when it starts up on the network. Because the IP addresses are dynamic (leased) rather than static (permanently assigned), addresses no longer in use are automatically returned to the pool for reallocation.

The network administrator establishes DHCP servers that maintain TCP/IP configuration information and provide address configuration to DHCP-enabled clients in the form of a lease offer. The DHCP server stores the configuration information in a database, which includes:

o Valid TCP/IP configuration parameters for all clients on the network.o Valid IP addresses, maintained in a pool for assignment to clients, as well as

excluded addresses.

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o Reserved IP addresses associated with particular DHCP clients. This allows consistent assignment of a single IP address to a single DHCP client.

o The lease duration, or the length of time for which the IP address can be used before a lease renewal is required.

A DHCP-enabled client, upon accepting a lease offer, receives:

o A valid IP address for the subnet to which it is connecting.o Requested DHCP options, which are additional parameters that a DHCP server

is configured to assign to clients. Some examples of DHCP options are Router (default gateway), DNS Servers, and DNS Domain Name. For a full list of DHCP options, see “DHCP Tools and Settings.”

oDHCP Terms and Definitions

Term Definition

DHCP server A computer running the DHCP Server service that holds information about available IP addresses and related configuration information as defined by the DHCP administrator and responds to requests from DHCP clients.

DHCP client A computer that gets its IP configuration information by using DHCP.

Scope A range of IP addresses that are available to be leased to DHCP clients by the DHCP Server service.

Subnetting The process of partitioning a single TCP/IP network into a number of separate network segments called subnets.

DHCP option Configuration parameters that a DHCP server assigns to clients. Most DHCP options are predefined, based on optional parameters defined in Request for Comments (RFC) 2132, although extended options can be added by vendors or users.

Lease The length of time for which a DHCP client can use a DHCP-assigned IP address configuration.

Reservation A specific IP address within a scope permanently set aside for leased use by a specific DHCP client. Client reservations are made in the DHCP database using the DHCP snap-in and are based on a unique client device identifier for each reserved entry.

Exclusion/exclusion range

One or more IP addresses within a DHCP scope that are not allocated by the DHCP Server service. Exclusions ensure that the specified IP addresses will not be offered to clients by the DHCP server as part of the general address pool.

DHCP relay agent Either a host or an IP router that listens for DHCP client messages being broadcast on a subnet and then forwards those DHCP messages directly to a configured DHCP server.

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The DHCP server sends DHCP response messages directly back to the DHCP relay agent, which then forwards them to the DHCP client. The DHCP administrator uses DHCP relay agents to centralize DHCP servers, avoiding the need for a DHCP server on each subnet. Also referred to as a BOOTP relay agent.

Superscope A configuration that allows a DHCP server to provide leases from more than one scope to clients on a single physical network segment.

Multicast IP addresses

Multicast IP addresses allow multiple clients to receive data that is sent to a single IP address, enabling point-to-multipoint communication. This type of transmission is often used for streaming media transmissions, such as video conferencing.

Multicast Scope A range of multicast IP addresses that can be assigned to DHCP clients. A multicast scope allows dynamic allocation of multicast IP addresses for use on the network by using the MADCAP protocol, as defined in RFC 2730.

BOOTP An older protocol with similar functionality; DHCP is based on BOOTP. BOOTP is an established protocol standard used for configuring IP hosts. BOOTP was originally designed to enable boot configuration for diskless workstations.

How to troubleshoot to install CPE?

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For USB Dongle

Check the OS in the computer. Also check the service pack for that OS---Select My Computer

--Right Click To My Computer And Select Properties

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--At General Tab Check The Service Pack 2

Check the USB Dongle Software---Click the Start tab

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Select the Control Panel

At Control panel Select the Add or Remove Programs

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Check the Software

Check The WiMAX Network Adapter by selecting My Computer

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Right Click to My Computer And Select Manage

Select Device Manager

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Check The WiMAX network Adapter

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Verify the Dongle Username And Password1. At user name always give the relaim (i.e @banglalion.com.bd)2. give the user password3. confirm the password4. Press OK

Check the Dongle Power is ON

-Go to the Dongle Software at the Taskbar-double click it-Select the Tools Tab of the Dongle Software

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Make power ON

Click OK

Check the Automatic IP by selecting the My Network places

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Right Click on My Network places and select properties

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Right Click the LAN and select properties

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Select TCP/IP and click properties

Check Obtain IP Address and DNS server Automatically

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Check the IP Configuration:Go to the Run prompt from the taskbar

Type: cmd

Type: ipconfig /all

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Press enter and verify the IP Adress, Subnetmask, Defaultgetway, DNS and DHCP server, Physical Address

Ping any website Type: Ping yahoo.com

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Ping the client IP AddressType: Ping 180.149.7.23

Ping the Default gatewayType: Ping 180.149.0.1

Ping the DNS ServerType:Ping 180.149.31.2

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How to Configure a USB Dongle?

Follow the configure sequence.

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Bcl Wimax Training Doc v1

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