wimax in depth - module 1

7/29/2019 WiMAX in Depth - Module 1

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WIMAX in Depth IEEE 802.16Copyright LEVER Technology Group PLC - http://www.lever.co.uk - All Rights Reserved

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Copyright 2005 LEVER Technology Group PLC - http://www.lever.co.uk1

WiMAX In Depth

IEEE 802.16

Worldwide Interoperability for Microwave Access

V2


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Course Instructor

Don Cochrane


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Introduction & Objectives

Overview

This three-day course is about the IEEE 802.16 BroadbandWireless Access Standard

Key benefits:

Understand what has been standardised

Learn the basic concepts underpinning Fixed Wireless Access

Appreciate what the 802.16 standard means and how thetechnology operates

It assumes:

A technical background, some telecoms would be useful

Introduction & ObjectivesAs a general strategy, the course does not reproduce pages of data figures. This is because:1. The figures may change with subsequent releases of the standard - anyone

needing them must refer to the latest issue of the standard2. Relatively few people need the actual numbers and overloading everyone withnon-essential data is counter-productive3. Trying to remember them is unnecessary and hard work4. Lists of parameters are very boring to both present and to listen to.


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Housekeeping

Start/Finish Time

Lunch

Coffee Breaks

Emergencies

Toilets

Mobile Phones

Questions


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Course Agenda

Overview of IEEE 802.16and WiMAX

802.16 Family of Standards

RF Design and Characteristics

802.16 Air Interface - PhysicalLayer

802.16 - MAC layer

Quality of Service

WiMAX Security

Planning a WiMAX Network

Network Designand Implementation

Interference

Delivering Voice over IP Services(VoIP)

Current trends with WiMAX

Over Three Days


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CHAPTER ONE

Overview of WiMAX and 802.16


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Something to Remember

People focus on throughput in bits per second.

We see claims about 11 Mbps, 100 Mbps, etc. Two things:

This rate is shared between uplink and downlink so, forexample, WiFi (802.11b) claims 11 Mbps but the one way rateis around 5.5 Mbps

Its SHARED between all the users in the area

Think of the radio capacity of a cell/Access Point as a cake:

The cake is the available capacity of the cell.

If users get a big slice then we have few users

If users each get a crumb then everybody gets a bit

But it could be a VERY small bit

Something to RememberAn excellent example is 3G (UMTS) a range of different data rates are available up to 384 kbpsper user. However with 384 kbps to a user there may be at most 3 such users taking most of

the cell capacity and planning constraints may drop that to just 1 such user.Alternatively there could be 250+ users each with just a few kbps.


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System Architecture

SS Subscriber Station

TE Terminal Equipment (The customers stuff)

RS - Repeater Station

CoreNetwork

BaseStation

Directional Antenna

or

Intercell

Link

SS TE

SS TE

SS TE

SS TE

SS TE

G

RS

RS

~~

~

~

~

~

~

~

TE TE

Omnidirectional Antenna

System ArchitectureA real system may have all or only some of these, e.g. there may not be Repeaters if there isno mesh.

Repeaters are used when the Base Station has no line of sight (LOS) to the SS and also toincrease the effective range of the Base StationTraffic may pass through one or more Repeaters to reach an SS.


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Fixed Wireless Access

Replace the local loop between a customer and a local exchange

Traditionally copper pair used

Straight telephone service using radio is Wireless Local Loop

We are looking to provide a better service than that

Just like ADSL and Cable Modems do for copper pairs

Looking for data rates well above 2 Mbps

Hence Broadband Wireless Access

Large coverage distances of up to 50 kilometres under LOS conditionsand typical cell radii of up to 5 miles/8 km under NLOS conditions.

LOS = Line of Sight NLOS = Non-Line of Sight

Fixed Wireless AccessLOS doesnt mean just a really narrow path between buildings from transmitter to receiver but areasonably wide free space path. Technically, this is defined as 60% of the first Fresnel zone.


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The Idea The First Mile

Cheaper than cable

Easy to deploy andwithdraw

High bit rates (severalMbit/s per customer)

Frequencies used: 2.4 to40 GHz, and lower (fromLOS to nLOS solution)

Associated services :VoIP, broadbandinternet, multimedia

Source: ATDI


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NLOS is GOOD!!

Means the transmitmast neednt be thehighest thing around

This makes planning alot easier

Also installation atcustomer site needntbe on the roof

NLOS is GOOD!!In a NLOS link, a signal reaches the receiver through reflections, scattering, and diffractions. Thesignals arriving at the receiver consists of components from the direct path, multiple reflected paths,

scattered energy, and diffracted propagation paths. These signals have different delay spreads,attenuation, polarizations, and stability relative to the direct path.The multi path phenomena can also cause the polarization of the signal to be changed. Thus usingpolarization as a means of frequency re-use, as is normally done in LOS deployments can beproblematic in NLOS applications.How a radio system uses these multi path signals to an advantage is the key to providing service inNLOS conditions. A product that merely increases power to penetrate obstructions (sometimescalled near line of sight) is not NLOS technology because this approach still relies on a strongdirect path without using energy present in the indirect signals. Both LOS and NLOS coverageconditions are governed by the propagation characteristics of their environment, path loss, and radiolink budget.There are several advantages that make NLOS deployments desirable. For instance, strict planning

requirements and antenna height restrictions often do not allow the antenna to be positioned forLOS. For large-scale contiguous cellular deployments, where frequency re-use is critical, loweringthe antenna is advantageous to reduce the co channel interference between adjacent cell sites. Thisoften forces the base stations to operate in NLOS conditions. LOS systems cannot reduce antennaheights because doing so would impact the required direct view path from the CPE to the BaseStation.NLOS technology also reduces installation expenses by making under-the-eaves CPE installation areality and easing the difficulty of locating adequate CPE mounting locations.The NLOS technology and the enhanced features in WiMAX make it possible to use indoorcustomer premise equipment (CPE). This has two main challenges; firstly overcoming the buildingpenetration losses and secondly, covering reasonable distances with the lower transmit powers andantenna gains that are usually associated with indoor CPEs. WiMAX makes this possible, and theNLOS coverage can be further improved by leveraging some of WiMAXs optional capabilities.


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The Market Place

Point to Multi-Point is normal

Needs Line of Sight to Base Station at higherfrequencies

Lower Frequencies can support Non-line of sight

One Base Station

Several thousand customersin a 4 - 5 km range

Not mobileNot nomadicFixed users

The Market Place


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Mesh?

Each user acts as a relay to other usersSolves the line of sight problem

Users may have two antennasWIBNI antennas were steerable remotely to add new users

Mesh?The provider can use the facilities of Network Management to reconfigure the configuration.This may be necessary when a new building blocks an existing line.


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Deployment: WiMAX for Backhaul

This, like hotspot backhaul is really a niche market Insufficient to make a serious business or warrant huge

investment

Similar to rural access.

Some pundits predict that the main markets are in urban areasand the mobile (802.16e) market (IDC)

This in April 2005. Dishnet Wireless plans to spend US$57 million to rollout national Wi-Fihotspot network in India via WiMax: The firm wants to jumpstart service ahead of rivals whichare committed to wireline operations. Dishnet will use WiMax (or pre-WiMax, more likely until

certification) to handle backhaul among a potential 6,000 Wi-Fi hotspots. By next March, theywill link up 38 cities, starting with Bangalore. The owner of Dishnet Wireless sold a wirelineDSL business (Dishnet DSL) to a former government-owned Internet provider. He also has aninterest in the Barista coffee chain which will offer Dishnet Wireless service.


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Deployment: WIMAX Hotspot Solution

This from Aradial

WiMAX

Opportunity: A carrier is deploying two new cell towers and a Wi-Fi hotspot in a

rural community within the next two months. They want to be able toconnect their cell towers to their core network and the hotspot to

the Internet.

Solution:WiMAX provides the best solution for this challenge because it

provides a cost-effective, rapidly deployable point-to-point

backhaul solution.

Radius Server (AAA) and Radius Billing Solutions.The diagram shows how Aradial Radius server is connected to the network.Hardware (Accessclients) : ISP routers, PPPOE, VOIP Gateways and PBX, Hotspots Access points, Hotspots

Access gateways, and Mobile AAA (WAP,GPRS,MMS and 3G).Radius server communicates with the radius billing server for authentication and accounting


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Deployment: Last Mile

A WISP wants to expand its service coverage to underservedmarkets. QoS is a significant factor for this deployment becausesome of the new customers are local government and small andmedium businesses requiring a guaranteed level of service forcertain applications. Deployment cost and vendor interoperabilityis key because many users within the target-market segment mayend up owning their own WiMAX CPE.

WiMAX provides the best and the most cost-effective broadband

solution to this challenge because the cost of deploying and

providing traditional broadband services is prohibitivelyexpensive. WiMAX is designed from the ground up to provide afast, cost-effective and easy-to-deploy solution with built-inQoS. WiMAX is based on IEEE standards and WiMAX-certifiedproducts are vendor interoperable.

Source: IntelWISP Wireless Access Service Provider


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Operator Needs

Source: Redline Communications


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ETSI BRAN

Source: ETSI

Broadband Radio Access Network initiative

Addressing more than one area

Inside buildings - HiperLAN

LANs to Servers - HiperLink

Access to public networks - HiperAccess

ETSI BRANThe work of the ETSI Broadband Radio Access Networks (BRAN) project and itsHIPERACCESS family is looking toward a greater symmetry with broadband delivery possible

in both uplink and downlink directions supporting ATM and/or IP transport. To this end, theBRAN project has strong links to the ATM-Forum and their wireless ATM group. Additionally,the HIPERACCESS group expects to draw on the expertise of the HIPERLAN standardisationgroups, also within the BRAN project, which have drafted standards for Radio LAN short range,licence exempt, equipments also employing ATM transport in the 5GHz spectrum area.HIPERACCESS systems will use fixed bi-directional radio connections to convey broadbandservices between users premises and a broadband core network. HIPERACCESS is aimedparticularly at residential customers and small businesses, where the economic benefits ofusing the shared radio medium are greatest. Radio access will be particularly useful to allownetworks to be built economically by the competing telecommunications service providers ofthe future.


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All the Hipers.

HIPERLAN/2 Short range, high speed access (25 Mbit/s typicaldata rate) to a variety of networks including the UMTS corenetworks, ATM networks and IP based networks. Range 30 to 150Metres. Connection oriented.

HIPERACCESS Long range, point-to-multipoint, high speedaccess (25 Mbit/s typical data rate) by residential and smallbusiness users

HIPERLINK Short range, very high speed interconnection ofHIPERLANs and HIPERACCESS, e.g. up to 155 Mbit/s overdistances up to 150 m.

W.I.B.N.I. HiperAccess and IEEE 802.16 were, at least, compatible?

ETSI seem to have been working on this for years and years!

All the HIPERSHIPERACCESS target range is 5 km. Products seem very quiet or non-existent

W.I.B.N.I. Wouldnt it be nice if


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HIPERAccess

First HIPERAccess specification approved in 2002 The first deliverables for the HIPERACCESS broadband radio

access system are out:

The HIPERACCESS Physical Layer specification (TS 101 999)HIPERACCESS System Overview (TR 102 003)


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A Makers Problem

802.16 is a very large specification designed to cover the fixedbroadband wireless access needs of a variety of differentsituations.

There are allowances for different physical layers for differentfrequency bands

The system can be IP or ATM centric.

An implementer faces a tough decision: build an IEEE 802.16compliant system implementing every possible feature, eventhose features you know will never be used in systems for yourtarget customers?

Or, do you build a system with only the subset of features youneed for your market, risking accusations of non-compliance andlack of interoperability?

it is clear that the IEEE 802.16 Air Interface Specification is a very largespecification. It was designed to cover the fixed broadband wireless access needsof a variety of different situations. There are allowances for different physical

layers for different frequency bands and country-by-country frequency userestrictions. There are features that allow one to build an IP centric system or anATM centric system depending upon the needs of customers. The specification isdesigned to cover application to diverse markets from very high bandwidthbusinesses to SOHO and residential users.Because of the wealth of options available, an implementer currently faces a toughdecision. Do you build an IEEE 802.16 compliant system implementing everypossible feature, even those features you know will never be used in systems foryour target customers? Or, do you build a system with only the subset of featuresyou need for your market, risking accusations of non-compliance and lack ofinteroperability?


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The OFDM Forum

Just in passing: Members of the WiMAX Forum

A nested forum

Dedicated to promoting the concept of Orthogonal WavelengthDivision Multiplexing

In several wireless areas.

Seen as a good bandwagon to be on

They may be right

The OFDM Forum is a voluntary association of hardware manufacturers, software firms andother users of orthogonal frequency division multiplexing (OFDM) technology in wirelessapplications. The OFDM Forum was created to foster a single, compatible OFDM standard,

needed to implement cost-effective, high-speed wireless networks on a variety of devices.OFDM is a cornerstone technology for the next generation of high-speed wireless dataproducts and services for both corporate and consumer use. With the introduction of the IEEE802.11a, ETSI BRAN, and multimedia applications, the wireless world is ready for productsbased on OFDM technology.


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Relationship between 802.11 (WLANs)and 802.16 (Wireless Access)

Scope

Speed

Range

Radio Freq

802.16 Wireless Access

Raw rates >120 Mbps

Local Area: 4 - 6 km

Licenced 10 - 60 GHz

Licenced 2 - 11 GHz

Unlicenced 5-6 GHz

802.11 WLAN

11-53 Mbps

Picocell, office,Starbucks, etc.

10-20 m

Unlicenced2.4/5.8 GHz

802.15 WPANs

1 20 Mbps10 Metres or so

Unlicenced2.4 GHz

Note thatWiMEDIA islooking to goto 400 Mbps

Relationship between 802.11 (WLANs) and 802.16 (Wireless Access)The distinction between WLANs and wireless access is important. The WLAN business isgrowing very quickly at the moment.

Wireless access is for non-moving users, a replacement for a physical connection whilst theWLAN is for nomadic users, i.e. they arent mobile when using the system but move betweenuses. The Starbucks initiative was that you go into a Starbucks, get a cup of coffee and sit andreceive email, etc. whilst you drink it. Then you finish the coffee but havent finished emailing soyou drink more coffee. The really smart deal that Starbucks did (on their side) however, finishedoff the (dumb) carrier concerned.


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So what is WiBRO?

WiBRO is the South Korean version of mobile WiMAX (The estandard)

South Korea has a higher density of broadband than anywhereelse on earth

WiBRO doesnt have the frequency agility of WIMAX as it usesthe 2.3 GHz band not generally available or only available withlimited channels (US)

WiBRO grew out of the Korean HPi (High-speed Portable Internet)project which originally ignored the IEEE work.

HPi was also considered to be a portable solution versus a trulymobile solution.

HPi was being designed for sub-60km/h with sub-150ms intra-cellhandover versus the more stringent Mobile WiMAX requirementsof 120km/h and sub-50ms, respectively.

In April 2004, the Koreans moved towards compatibility.

So what is WiBRO?In February 2002 the South Korean government assigned 100MHz in the 2.3GHz spectrum fora portable Internet service.


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Why so many?

10-66 GHz Line of Sight (LOS) is needed Little or no multipath interference Channels of 25 or 28 MHz Point to Multipoint, 120 MBps raw data rates

Frequencies below 11 GHZ LOS not required More multipath problems

Needs power management and interference strategy

Licence exempt (probably 5 to 6 GHz) As above but more interference Regulations limit power output Dynamic Frequency Selection (DFS) to avoid interferers

Why so Many?Wireless performance varies with frequency.


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wimax in depth - module 1

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