Lecture 11 802.16/ WiMax A MAC/PHY Technical Overvieilenia/course/11-wimax.pdf · WiMax spectrum is more economical than 3G. The price paid per Hz is as much as 1000 times lower than

Lecture 11Lecture 11

802.16/802.16/WiMaxWiMax

Ilenia Tinnirello

802.16/802.16/WiMaxWiMax

A MAC/PHY Technical OverviewA MAC/PHY Technical Overview

1. Introduction1. Introduction

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1. Introduction1. Introduction

Moore’s Law for Moore’s Law for

Mobile InternetMobile InternetUltra Mobile PCUltra Mobile PC

Thin and LightThin and LightNotebookNotebook

SubSub--NotebookNotebook

17”17” ScreenScreen

3”3” ScreenScreen

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EntertainmentEntertainment& Productivity& Productivity

NotebookNotebook

NotebookNotebook17”17” ScreenScreen

NEAR FUTURE…

~10XLOWER POWER

~10XMORE MOBILE

Product descriptions, plans and comparisons provided are estimates only and subject to change without notice

Statements are vs. current devices

The Economic Challenge: The Economic Challenge:

Device CostDevice Cost

$60$60

$100$100

$80$80

Monthly ARPU Est.Monthly ARPU Est.

3G Today3G Today

90% Attach 90% Attach Rate GoalRate Goal

<10% Attach <10% Attach RateRate

$40$40

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$20$20 $40$40 $60$60 $100$100$80$80 $120$120PC CardPC CardCost Est.Cost Est.Source: Intel, Instat, Q3’06Source: Intel, Instat, Q3’06

$20$20

$0$0

WiFiWiFiTodayToday

+ WiMAX + WiMAX TomorrowTomorrow

• 5 year goal for the mobile Internet worldwide: $30 - $30

• Can be achieved only by volume economics

Mobile Broadband Wireless Access Mobile Broadband Wireless Access

(MBWA)(MBWA)

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Think of InternetThink of Internet

�There are three possible ways to access internet.

�Broadband access

Uses DSL or cable modem at home and T1 or T3 line at office

�WIFI

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�WIFI

Uses WIFI routers at home and hotspots on the road

�Dial Up Connection

�A new one: WiMax!!

�Target scenario: Wireless ADSL

How How WiMaxWiMax works?works?

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Modes of OperationModes of Operation

�Non-Line of sight

Uses a lower frequency range.

�Line of sight

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�Line of sight

Uses a higher frequency range.

WIMAX CHIPSWIMAX CHIPS

WiMAX Mini-PCI Reference Design Intel’s first WIMAX chip

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WiMaxWiMax/IEEE 802.16/IEEE 802.16

�Technical name: IEEE 802.16

�Requirements:

�Range- 50 km from base station

�Speed- 70 Megabits per second

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�Speed- 70 Megabits per second

�Frequency bands- 2 to 11 and 10 to 66(licensed and

unlicensed bands respectively)

�Defines both MAC and PHY layer and allows multiple

PHY layer specifications

IEEE 802.16 IEEE 802.16 ArchitectureArchitecture

� IEEE 802.16 Protocol Architecture has 4 layers: Convergence, MAC, Transmission and physical, which can be mapped to two OSI

lowest layers: physical and data link.

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IEEE 802.16 TopologiesIEEE 802.16 Topologies

�P2MP

BS connected to Public Networks

BS serves Subscriber Stations (SS)

Provides SS with first mile access to Public

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Provides SS with first mile access to Public Networks

�Mesh

Optional architecture for WiMAX

P2MP TopologyP2MP Topology

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Mesh Mesh TopologyTopology

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Benefits of Benefits of WiMaxWiMax

�Speed

� Faster than broadband service

�Wireless

�Not having to lay cables reduces cost

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�Easier to extend to suburban and rural areas

�Broad Coverage

�Much wider coverage than WiFi hotspots

Benefits to Service ProvidersBenefits to Service Providers

�Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video

�Facilitate equipment compatibility�Reduce the capital expenditures required for network expansion

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network expansion�Provide improved performance and extended range

Benefits to CustomersBenefits to Customers

�Range of technology and service level choices from both fixed and wireless broadband operators

�DSL-like services at DSL prices but with portability

�Rapidly declining fixed broadband prices

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�Rapidly declining fixed broadband prices�No more DSL “installation” fees from incumbent

WiMaxWiMax vs. vs. WiFiWiFi: Scalability: Scalability

• Channel bandwidths can be

chosen by operator (e.g. for

sectorization)

• 1.5 MHz to 20 MHz width

• Wide (20MHz) frequency

channels

802.16a802.11

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• 1.5 MHz to 20 MHz width

channels. MAC designed for

scalability. independent of

channel bandwidth

• MAC designed to support

thousands of users.

• MAC designed to support 10’s

of users

2.7 bps/Hz54 Mbps20 MHz802.11

Maximum

bps/Hz

Maximum

Data Rate

Channel

Bandwidth

WiMax vs. WiFi: Performance

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5.0 bps/Hz100 Mbps1.5 – 20 MHz802.16a

2.7 bps/Hz54 Mbps20 MHz802.11

WiMaxWiMax vs. vs. WiFiWiFi: :

Quality Quality of Serviceof Service

• Grant-request MAC

• Designed to support Voice and

• Contention-based MAC

(CSMA/CA) => no guaranteed QoS

• Standard cannot currently

802.16a802.11

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• Designed to support Voice and

Video from ground up

• Supports differentiated service

levels: e.g. T1 for business

customers; best effort for

residential.

• Centrally-enforced QoS

• Standard cannot currently

guarantee latency for Voice, Video

• Standard does not allow for

differentiated levels of service on a

per-user basis

• 802.11e (proposed) QoS is

prioritization only

WiMaxWiMax vs. vs. WiFiWiFi: Range: Range

• Optimized for up to 50 Km

• Designed to handle many users

spread out over kilometers

• Optimized for ~100 meters

• No “near-far” compensation

802.16a802.11

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• Designed to tolerate greater

multi-path delay spread (signal

reflections) up to 10.0µ seconds

• PHY and MAC designed with multi-

mile range in mind

• Designed to handle indoor multi-

path delay spread of 0.8µ seconds

• Optimization centers around PHY

and MAC layer for 100m range

WiMaxWiMax vs. vs. 3G3G

�Using an assortment of proprietary and standards-based technologies, such as OFDM and W-CDMA ,WiMax has a clear advantage over 3G

�The advantages include

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�The advantages include

�Higher Throughput

�Low Cost

�Lower Latency

WiMaxWiMax vs. 3Gvs. 3G

�WiMax spectrum is more economical than 3G.

�The price paid per Hz is as much as 1000 times

lower than for 3G spectrum

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�The low cost is a clear driver for service providers to

enter the field of wireless services with WiMax

Bandwidth AllocationBandwidth Allocation

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WiMaxWiMax in in EuropeEurope

Spain: Iberbanda has integrated a pre-WiMax technologyto its broadband network

Norway: Allocations of about 150 licences for the frequency range 3.4-3.6 GHz

Switzerland: Licences assigned for WLL in the range 3.4-

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Switzerland: Licences assigned for WLL in the range 3.4-3.6 GHz enabled for WiMax too

UK: Telabria has started a public network based on WiMax

Italy: assigned at beginning 2008..in the range 3.4-3.6 GHz

BLOCCO A

ARIADSL S.p.A

A.F.T.

WiMaxWiMax in Italy: in Italy:

National LicensesNational Licenses

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BLOCCO B

E-VIA GRUPPO RETELIT

TELECOM ITALIA S.p.A.


National LicensesNational Licenses

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TELECOM ITALIA S.p.A.

TOURIST FERRY-BOAT/TEMIX/MEDIANET COMUNICAZIONI

BLOCCO C

A.F.T.

BRENNERCOM

MGM Productions/Profit Group

Ribes/Hal Service/Lan Service/Informatica System/Tex97/B.B.Bell


Regional Regional LicensesLicenses

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Assomax

Infracom

City Carrier

ARIADSL

Active Offers(from October 2008)

ARIA Family 2 Mbit/sVELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN)100 KBIT/s DI BANDA GARANTITA

CANONE MENSILE 23,94€

ARIA Entry 2 Mbit/sVELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN)230 KBIT/s DI BANDA GARANTITA


ARIA Office 4 Mbit/sVELOCITÀ DI CONNESSIONE 2MBIT/S

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ARIA Family 4 Mbit/sVELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN)180 KBIT/s DI BANDA GARANTITA


VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN)340 KBIT/s DI BANDA GARANTITA


ARIA Enterprise 4 Mbit/sVELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN)480 KBIT/s DI BANDA GARANTITA


MAX 20€Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico.

MAX 30€Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico + VOCE

Active OffersActive Offers

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MAX 45€Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico + VOCE + 3 ore/mese verso i cellulari

Canone di attivazione 50€se in addebito diretto o 100€ se con bollettino postale

Modem radio Gratuito

Navigazione gratuita negli hot spot

2. Network Architecture2. Network Architecture

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PointPoint--toto--Multipoint Multipoint

Wireless MAN: not a LANWireless MAN: not a LAN

� Base Station (BS) connessa alle reti pubbliche

� Ogni BS serve un certo numero di Subscriber Stations (SSs)

� Ogni SS tipicamente copre un edificio

� Rappresenta la connettivita’ radio a larga banda per l’ultimo miglio

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� Rappresenta la connettivita’ radio a larga banda per l’ultimo miglio

� Confronto con le Wireless LAN:

� Servizio multimediali e a qualita’ di servizio

� Molti piu’ utenti

� Data rate molto piu’ alti

� Distanze maggiori

Wireless MANWireless MANAdaptive PHYAdaptive PHY

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(burst(burst--byby--burst adaptivity not shown)burst adaptivity not shown)

Network ArchitectureNetwork Architecture

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Divisione fornitore di rete da

fornitore di servizi!!

Network TopologyNetwork Topology

MAC

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MAC

Address

PointPoint--toto--Multi Point (PMP)Multi Point (PMP)

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MESH ModeMESH Mode

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3. Protocolli3. Protocolli

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BWA Working groupBWA Working group

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Wireless Interoperability for Wireless Interoperability for

Microwave Access (WiMAX)Microwave Access (WiMAX)

�Il WiMAX Forum�promuove la tecnologia IEEE 802.16 per l’accesso wireless in ambientemetropolitano (Wireless Metropolitan Area Network, WMAN)

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�certificha l’interoperabilità tra i dispositivibasati sulla tecnologia IEEE 802.16

Protocolli 802.16Protocolli 802.16

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MAC SubMAC Sub--LayersLayers

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MAC MAC SubSub--Layers (2)Layers (2)

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MAC SubMAC Sub--Layers (3)Layers (3)

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Frequency BandwidthsFrequency Bandwidths

�10-66 GHz con licenza�fenomeno attenuativo dovuto a strutture, pioggia, ecc.

�Line-Of-Sight (LOS)

�2-11 GHz con licenza

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�2-11 GHz con licenza�Non-Line-Of-Sight (NLOS)�fenomeno multi-path

�2-11 GHz senza licenza�Non-Line-Of-Sight (NLOS)�fenomeno multi-path�interferenza dovuta ad altri utenti

Physical Layer (PHY)Physical Layer (PHY)

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�Modulazione Single-Carrier

�Modulazione Multi-Carrier

�Orthogonal Frequency Division Multiplexing (OFDM)

Orthogonal Frequency Division Orthogonal Frequency Division

Multiplexing (OFDM)Multiplexing (OFDM)

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Physical Layer DetailsPhysical Layer Details

�PHY basato sul frame

�Accesso multiplo Time Division Multiple Access (TDMA)

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�Duplexing �Frequency Division Duplexing (FDD)

�Time Division Duplexing (TDD)

DuplexingDuplexing

�Time-Division Duplex (TDD)

�DL & UL time-share the same RF channel

�Dynamic asymmetry

�SS does not transmit/receive simultaneously (low cost)

�Frequency-Division Duplex (FDD)

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�Frequency-Division Duplex (FDD)

�Downlink & Uplink on separate RF channels

�Static asymmetry

�Half-duplex SSs supported

�SS does not transmit/receive simultaneously (low cost)

DuplexingDuplexing

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Physical Layer SummaryPhysical Layer Summary

Designation Applicability MAC Duplexing

WirelessMAN-SC 10-66 GHz Licensed

Basic TDD, FDD

WirelessMAN-SC 2-11 GHz Licensed Basic, (ARQ), (STC), (AAS)

TDD, FDD

2-11 GHz Licensed Basic, (ARQ), TDD, FDD

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WirelessMAN-OFDM

2-11 GHz Licensed Basic, (ARQ), (STC), (AAS)

TDD, FDD

2-11 GHz License-exempt

Basic, (ARQ), (STC), (DFS), (MSH), (AAS)

TDD

WirelessMAN-OFDMA

2-11 GHz Licensed Basic, (ARQ), (STC), (AAS)

TDD, FDD

2-11 GHz License-exempt

Basic, (ARQ), (STC), (DFS), (MSH), (AAS)

TDD

DefinitionsDefinitions

�Service Data Unit (SDU)�Data units exchanged between adjacent layers

�Protocol Data Unit (PDU)�Data units exchanged between peer entities

�Connection and Connection ID

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�Connection and Connection ID�a unidirectional mapping between MAC peers over the

airlink (uniquely identified by a CID)

�Service Flow and Service Flow ID�a unidirectional flow of MAC PDUs on a connection that

provides a particular QoS (uniquely identified by a SFID)

Adaptive Burst ProfilesAdaptive Burst Profiles

�Burst profile

�Modulation and FEC

�Dynamically assigned according to link conditions

�Burst by burst, per subscriber station

�Trade-off capacity vs. robustness in real time

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�Trade-off capacity vs. robustness in real time

�Roughly doubled capacity for the same cell area

�Burst profile for downlink broadcast channel is well-known and robust

�Other burst profiles can be configured “on the fly”

�SS capabilities recognized at registration

General Downlink Frame StructureGeneral Downlink Frame Structure

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• Downlink Interval Usage Code (DIUC) indicates burst profile

Per le stazioni

half-duplex, in

modalita’ FDD

Burst FDD FramingBurst FDD Framing

frame

UPLINK

DOWNLINK

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frame

Broadcast

Full Duplex Capable User

Half Duplex Terminal #1

Half Duplex Terminal #2

Allows scheduling flexibility

General Uplink Frame StructureGeneral Uplink Frame Structure

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• Uplink Interval Usage Code (UIUC) indicates burst profile

Frame Structure Frame Structure –– SummarySummary

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MAC Common Part SubMAC Common Part Sub--LayerLayer

�Management operations�Access to the network

�Multi access

�Scheduling

�QoS support

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�QoS support

�Power control

MAC Common Part SubMAC Common Part Sub--LayerLayer

�MAC Characteristics�Connection oriented: service flows (SF) over virtual

connections (CID: 16 bit)

�SS have standard 802 48-bit MAC, only used as equipment id

�Channel access controlled by BS through UL-MAP, DL-MAP

�Services offered to higher layers

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�Services offered to higher layers�Legacy time-division multiplex voice and data

�Internet protocol connectivity

�Support any application flow: data, voice, VoD, video streaming

�Continuous and bursty traffic support

�Reservation/Polling scheme for resource allocation

�Scheduling non standardized: provide a way for vendors to

differentiate their equipments

Management ConnectionsManagement Connections

� Upon entering the network, the SS is assigned three management connections in each direction� Basic connection: transfer of short time-critical control messages

� Primary management connection: longer delay-tolerant messages (used

of authentication and connection setup)

� Secondary management connection: transfer of other management

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protocols messages such as DHCP, TFTP, SNMP

SS

Basic

Primary

Secondary

Data ConnectionsData Connections

� SSs are allocated transport unidirectional connections for the contracted services� Typically assigned in pairs

� Additional connections for other purposes

�Contention-based initial access

�Broadcast or multicast transmissions

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SS

CID1

CID2

CID3

MAC PDUMAC PDU

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MAC Management MessagesMAC Management Messages

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Generic MAC HeaderGeneric MAC Header

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MAC SubMAC Sub--HeaderHeader

�Esistono 5 tipi�Mesh

�Fragmentation

�Packing

�Fast Feedback Allocation

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�Fast Feedback Allocation

�Grant Management

SubSub--HeaderHeader

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FragmentationFragmentation

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Fragmentation subFragmentation sub--headerheader

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PackingPacking

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Packing subPacking sub--headerheader

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Difference between Difference between

concatenation and packingconcatenation and packing

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Network Entry ProcessNetwork Entry Process

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Network Entry ProcessNetwork Entry Process

1. syncronization

2. ranging

to find the RTD

3. registration

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Initial RangingInitial Ranging

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Capability NegotiationCapability Negotiation

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Service FlowService Flow

�Ad ogni flusso di dati dello stesso tipo e’ associato un Service Flow

�Ogni service flow e’ caratterizzato da un set diparametri diQoS�throughput

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�ritardo

�jitter

�probabilità di perdere un pacchetto

�Ogni service flow appartiene ad una classe diservizio a seconda dei parametri di QoSspecificati

Service Flow ManagementService Flow Management

�Ciascun service flow ha un identificativo(SFID) di 32 bit associato ad un Connection Identifier (CID) di 16 bit

�I service flow possono essere configurati a priori o dinamicamente�possono essere creati, modificati ed

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�possono essere creati, modificati edeliminati

�a tale scopo sono definiti dei messaggi di MAC management

Service ClassesService Classes

�Unsolicited Grant Service (UGS)

�e.g. VoIP

�Real-time Polling Service (rtPS)

�e.g. MPEG

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�Non-Real-time Polling Service (nrtPS)

�e.g. FTP

�Best effort

Unsolicited Grant Service (UGS)Unsolicited Grant Service (UGS)

�Allocazione statica di banda per la trasmissione uplink della SS

�Disegnato per supportare Service Flow realtime che generano pacchetti didimensione costante su una base periodica(p.e. Voice over IP, VoIP)�Non serve sollecitare ulteriori allocazioni

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�Non serve sollecitare ulteriori allocazioni

�Questo meccanismo consente di� eliminare overhead ed i ritardi introdotti dalmeccanismo di richiesta di banda

� garantire una banda costante che soddisfa i requisitireal-time dell’applicazione

RealReal--time Polling Service time Polling Service rtPSrtPS

�Allocazione statica di banda minima + possibilita’ di chiedere altra banda in piggybacking

�Disegnato per supportare traffico real-time che genera pacchetti di lunghezza variabile suuna base periodica (p. e. MPEG video)

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una base periodica (p. e. MPEG video)� Questo meccanismo consente

� soddisfare i requisisti real-time� la SS richiede la banda di cui ha bisogno

Non realNon real--time Polling Service nrtPStime Polling Service nrtPS

� Allocazioni periodiche di banda per trasmettere“richieste di banda” + ulteriori richieste di banda a contesa

� Disegnato per supportare traffico non real-time chegenera burst di dimensione variabile su una base periodica (p.e. FTP)

� Le richieste di banda possono essere inviate ad

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� Le richieste di banda possono essere inviate ad intervalli regolari, senza bisogno di contendere

� Questo meccanismo� introduce maggiore overhead dovuto alle richieste

� la banda è quella necessaria e questo incrementa l’efficienza

Best Effort (BE)Best Effort (BE)

�Allocazioni di banda solo dopo messaggi dirichiesta inviati a contesa

�L’obiettivo è fornire ad un traffico best effort un servizio più efficiente possibile

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Multi Access MechanismsMulti Access Mechanisms

�Tre modalita’ di base�banda garantita

�Voice over IP (VoIP)

�Polling

�Video streaming

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�Contesa

�Web browsing

�Applicate, per ogni flusso di servizio, in base ai requisiti del servizio richiesto dalla SS�banda

�ritardo

Requests and GrantsRequests and Grants

�La SS può richiedere banda in uplink adottando diversi meccansmi�un messaggio di PiggyBack per richieste incrementali

�un messaggio di richiesta (BR) dopo polling o a contesa

�Le richieste sono espresse in byte poichél’allocazione temporale può variare in base alla modulazione e codifica adottata

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alla modulazione e codifica adottata(adattamento al link)

�Le richieste da parte delle SS si riferiscono ad una connessione

�I grant generati dalla BS possono essere per connessione o per SS�La SS ri-distribuisce il grant tra le sue connessioni

QoSQoS ArchitectureArchitecture

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ContentionContention--based BRsbased BRs

�La scelta dello slot in cui trasmettere ilBandwidth Request (BR) avviene adottandoun meccanismo di backoff esponenzialebinario troncato�la base della finestra di backoff è 2

�la dimensione iniziale viene decisa dalla BS

�La SS estrae un numero casuale all’interno della finestra di

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�La SS estrae un numero casuale all’interno della finestra dibackoff

�la trasmissione della richiesta viene ritardata di un numero dislot pari al numero estratto

�Il Bandwidth Request (BR) viene trasmesso in un intervallo a contesa quindi si può verificareuna collisione

BackoffBackoff ProcessProcess

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Contention ResolutionContention Resolution

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PollingPolling--based BRsbased BRs

�La BS alloca nel UL-MAP una banda che la SS può utilizzare per trasmettere Bandwidth Requests

�può essere per connessione o per SS�Se la banda non è sufficiente per attivare un unicast polling verso tutte le SS inattive alloraè possibile adottare un multicast polling

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è possibile adottare un multicast polling�anche in questo caso il polling non è un messaggio esplicito ma una banda allocata nelmessaggio UL-MAP

�SS con delle connessioni UGS attive devonoporre ad 1 il bit poll-me nel grant management sub-header per richiedere bandaper il polling

OFDM/OFDMA PHYOFDM/OFDMA PHY

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OFDM/OFDMA PHYOFDM/OFDMA PHY

OFDM PHY ParametersOFDM PHY Parameters

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Coding and ModulationCoding and Modulation

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Downlink Sub Frame (FDD)Downlink Sub Frame (FDD)

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Downlink Sub Frame (TDD)Downlink Sub Frame (TDD)

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Uplink Sub Frame (TDD+FDD)Uplink Sub Frame (TDD+FDD)

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OFDMA OrganizationOFDMA Organization

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Frame Structure (TDD+FDDFrame Structure (TDD+FDD))

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Data RegionData Region

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ExampleExample

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Frame StructureFrame Structure

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ReferencesReferences

� IEEE 802.16-2004 (802.16REVd)

� IEEE 802.16-2005 (802.16e)

� Intel’s Whitepapers, 2004 (http://www.intel.com/technology/itj/2004/volume08issue03/)

� “IEEE Standard 802.16: A Technical Overview of the WirelessMAN Air Interface for Broadband Wireless Access,” C. Eklund et al., IEEE Communication

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WirelessMAN Air Interface for Broadband Wireless Access,” C. Eklund et al., IEEE Communication Magazine, June 2002

� “Broadband Wireless Access with 802.16/WiMax: Current Performance Benchmarks and Future Potential,” A. Ghosh et al., IEEE Communication Magazine, Feb 2005

� “Fundamentals of WiMax”, J. Andrews et al., Prentice Hall

Lecture 11 802.16/ WiMax A MAC/PHY Technical Overvieilenia/course/11-wimax.pdf · WiMax spectrum is more economical than 3G. The price paid per Hz is as much as 1000 times lower than

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