Basics, Network Entry ProcedureBasics, Network Entry Procedures, and Bandwidth Request/Grans, and Bandwidth Request/Grand Mechanism for IEEE Std. 802.1d Mechanism for IEEE Std. 802.1

66Chen-Nien TsaiChen-Nien Tsai

Institute of Computer Science and InformatiInstitute of Computer Science and Information Engineeringon Engineering

National Taipei University of TechnologyNational Taipei University of Technology2007.10.82007.10.8

2

OutlineOutline

►A Brief Introduction to IEEE Std. A Brief Introduction to IEEE Std. 802.16.802.16.

►Overview of IEEE 802.16Overview of IEEE 802.16►MAC/PHY BasicsMAC/PHY Basics►Network Entry and InitializationNetwork Entry and Initialization►Bandwidth Request/Grand MechanismBandwidth Request/Grand Mechanism►SummarySummary

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Introduction to IEEE Std. Introduction to IEEE Std. 802.16802.16

►The central aim of IEEE 802.16 The central aim of IEEE 802.16 technology is to support technology is to support broadband broadband accessaccess.. Providing service at a rate of at least 1.544 Providing service at a rate of at least 1.544

Mbps. (ITU definition)Mbps. (ITU definition)

►Broadband Wireless Access (BWA)Broadband Wireless Access (BWA) Broadband extension of the wireless access Broadband extension of the wireless access

concept.concept.

►Wireless Broadband AccessWireless Broadband Access A wireless implementation of broadband A wireless implementation of broadband

access concepts.access concepts.

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Introduction to IEEE Std. Introduction to IEEE Std. 802.16802.16

► IEEE Std. 802.16 is called the IEEE Std. 802.16 is called the wirelessMANwirelessMAN®® standard for wireless metropolitan area nestandard for wireless metropolitan area networkstworks. . Supports networks that are about the size of a Supports networks that are about the size of a

city.city. Not limited to urban applications.Not limited to urban applications. Some of the most likely applications are in ruraSome of the most likely applications are in rura

l areas.l areas.►Replace last-mile.Replace last-mile.

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Wireless TechnologiesWireless Technologies

802.11n

Wi-Fi802.11a/g

Wi-Fi802.11b

WiMAX802.16 4G

3G

2.5G

802.15.3High rate

WPAN

802.15.1Bluetooth

Bandwidth

1 Gbps

100 Mbps

10 Mbps

1 Mbps

PAN LAN MAN WAN<1m 10m 100

mUp to 50km Up to 80km

IEEE 802.15

IEEE 802.11

IEEE 802.16

3GPP/3GPP2/ETSI

PAN: Personal area networkLAN: Local area network

MAN: Metropolitan area networkWAN: Wide area network

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IEEE 802.16 Project TimelineIEEE 802.16 Project TimelineIEEE Std 802.16-2001

IEEE Std 802.16a

IEEE Std 802.16c

IEEE Std 802.16-2004

IEEE Std 802.16-2004/Cor1

IEEE P802.16-2004/Cor2

IEEE P802.16Rev2

IEEE Std 802.16e (mobile)

IEEE Std 802.16f (MIB)

IEEE P802.16g (management)

IEEE P802.16h (coexistence mechanism)

IEEE P802.16i (management)

IEEE P802.16j (multihop relay)

IEEE Std 802.16k-2007

IEEE P802.16m

IEEE Std 802.16/Conf01

IEEE Std 802.16/Conf02

IEEE Std 802.16/Conf03

IEEE Std 802.16/Conf04

IEEE Std 802.16.2-2001

IEEE Std 802.16.2-2004

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Completed

In progress

Superseded Standards

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IEEE Standard StylesIEEE Standard Styles

►AmendmentAmendment contains new material to be incorporated into contains new material to be incorporated into

an existing IEEE standard.an existing IEEE standard. Designated by a lowercase letter after the Designated by a lowercase letter after the

primary standard number.primary standard number. 802.16802.16cc, 802.16, 802.16aa. (amendment to 802.16-. (amendment to 802.16-

2001)2001)

►CorrigendumCorrigendum allows corrections but prohibits new features.allows corrections but prohibits new features. 802.16-2004/Cor1, 802.16-2004/Cor2.802.16-2004/Cor1, 802.16-2004/Cor2.

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IEEE Standard StylesIEEE Standard Styles

►RevisionRevision Base standard and its published Base standard and its published

amendments are editorially merged.amendments are editorially merged. 802.16-2004 (802.16-REVd), including 802.16-2004 (802.16-REVd), including

802.16-2001, 802.16c, 802.16a.802.16-2001, 802.16c, 802.16a. 802.16Rev2 (under development)802.16Rev2 (under development)

Overview of IEEE Overview of IEEE 802.16802.16

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IEEE 802.16IEEE 802.16

►Scope:Scope: Specifies the air interface of fixed BWA systems.Specifies the air interface of fixed BWA systems.

►Including the medium access control (MAC) layer anIncluding the medium access control (MAC) layer and multiple physical (PHY) layer specifications.d multiple physical (PHY) layer specifications.

►Purpose:Purpose: Enables rapid worldwide deployment of cost-eEnables rapid worldwide deployment of cost-e

ffective BWA products.ffective BWA products. Facilitates competition in broadband access bFacilitates competition in broadband access b

y providing alternatives to wireline broadband y providing alternatives to wireline broadband access.access.

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Basic Network ArchitectureBasic Network Architecture

Base Station (BS)

Wireless link

Subscribe Station (SS)

Wired linkCore network

Users

SS

SS

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BS and SSBS and SS

►Base station (BS)Base station (BS) A generalized equipment set providing A generalized equipment set providing

connectivity, management, and control of connectivity, management, and control of the SS.the SS.

►Subscribed station (SS)Subscribed station (SS) A generalized equipment set providing A generalized equipment set providing

connectivity between subscriber connectivity between subscriber equipment and a BS.equipment and a BS.

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Typical Deployment Typical Deployment ScenariosScenarios

Mesh Node

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Reference ModelReference Model

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Service-Specific Convergence SublayerService-Specific Convergence Sublayer

►FunctionsFunctions Classification.Classification. Header suppression.Header suppression.

►Two CS specifiedTwo CS specified ATM CS.ATM CS. Packet CS. Packet CS.

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MAC Common Part SublayerMAC Common Part Sublayer►FunctionsFunctions

System access.System access. Bandwidth allocation.Bandwidth allocation. Call admissionCall admission Connection Connection

management.management.

►Two operation modesTwo operation modes Point-to-multipoint (PMP)Point-to-multipoint (PMP) MeshMesh

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Security SublayerSecurity Sublayer►FunctionsFunctions

AuthenticationAuthentication Secure key exchangeSecure key exchange EncryptionEncryption

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Physical LayerPhysical Layer

►Four PHY specifiedFour PHY specified WirelessMAN-SC PHYWirelessMAN-SC PHY WirelessMAN-SCa PHYWirelessMAN-SCa PHY WirelessMAN-OFDM PHYWirelessMAN-OFDM PHY WirelessMAN-OFDMA PHWirelessMAN-OFDMA PH

YY

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Physical LayerPhysical Layer

►For 10-66 GHz (IEEE 802.16-2001)For 10-66 GHz (IEEE 802.16-2001) WirelessMAN-SC PHYWirelessMAN-SC PHY

►Single-carrier modulation.Single-carrier modulation.

►For 2-11 GHz (IEEE 802.16a)For 2-11 GHz (IEEE 802.16a) WirelessMAN-SCa PHYWirelessMAN-SCa PHY

►Single-carrier modulationSingle-carrier modulation

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Physical LayerPhysical Layer

►For 2-11 GHz (IEEE 802.16a)For 2-11 GHz (IEEE 802.16a) WirelessMAN-OFDM PHYWirelessMAN-OFDM PHY

►256-carrier OFDM (orthogonal-frequency division 256-carrier OFDM (orthogonal-frequency division multiplexing)multiplexing)

►Multiple access is provided through TDMA (time-diMultiple access is provided through TDMA (time-division multiple access).vision multiple access).

WirelessMAN-OFDMA PHYWirelessMAN-OFDMA PHY►2048-carrier OFDM.2048-carrier OFDM.►Multiple access is provided by assigning a subset oMultiple access is provided by assigning a subset o

f the carriers to an individual receiver.f the carriers to an individual receiver.

MAC/PHY BasicsMAC/PHY Basics

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MAC Support of PHYMAC Support of PHY►Several duplexing techniques are supportSeveral duplexing techniques are support

ed by the MAC.ed by the MAC. Time division duplexing (TDD)Time division duplexing (TDD)

►UL and DL transmission occur at different times anUL and DL transmission occur at different times and usually share the same frequency.d usually share the same frequency.

Frequency division duplexing (FDD)Frequency division duplexing (FDD)►UL and DL channels are located on separate frequUL and DL channels are located on separate frequ

encies.encies.►Full duplexFull duplex►Half duplexHalf duplex

►FDD or TDD?FDD or TDD?

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FramingFraming

►Each frame has a DL subframe and UL subEach frame has a DL subframe and UL subframe.frame. DL subframe begins with information necessaDL subframe begins with information necessa

ry for frame synchronization and control.ry for frame synchronization and control. In the TDD case, the DL subframe comes first, In the TDD case, the DL subframe comes first,

followed by the UL subframe.followed by the UL subframe. In the FDD case, UL transmission occur concurIn the FDD case, UL transmission occur concur

rently with the DL frame.rently with the DL frame.

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TDD Frame StructureTDD Frame Structure

PS (Physical slot): a unit of time for allocating bandwidth.

Rate: symbol rate for SC and SCa PHY, nominal sampling frequency for OFDM and OFDMA PHY.

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FDD Bandwidth AllocationFDD Bandwidth Allocation

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TDD Downlink SubframeTDD Downlink Subframe

synchronization

BW allocation and other channel information for DL/UL

Burst profile for DIUC = 0 is well-knownDownlink Interval Usage Code is a code identifying a particular burst profile

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Downlink transmissionDownlink transmission

►PreamblePreamble Synchronization and equalization.Synchronization and equalization.

►Frame controlFrame control DL-MAPDL-MAP

►How and when the DL data are transmitted.How and when the DL data are transmitted.

UL-MAPUL-MAP►How and when the UL data are transmitted.How and when the UL data are transmitted.

DCD/UCDDCD/UCD►Channel description for UL/DLChannel description for UL/DL

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TDD Uplink SubframeTDD Uplink Subframe

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Uplink TransmissionUplink Transmission

►Three classes of bursts may be transmitteThree classes of bursts may be transmitted in a UL subframe:d in a UL subframe: Contention opportunities for initial ranging.Contention opportunities for initial ranging. Contention opportunities for BW requests.Contention opportunities for BW requests. Contention-free periods assigned by BS to indContention-free periods assigned by BS to ind

ividual SSs.ividual SSs.

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Connections and AddressingConnections and Addressing►Each SS has a unique 48-bit MAC address.Each SS has a unique 48-bit MAC address.

It is used only during the initial ranging procesIt is used only during the initial ranging process or authentication process.s or authentication process.

Not carried in every MPDU.Not carried in every MPDU. How to identify src. and dest.? How to identify src. and dest.? CID CID

►802.16 MAC is connection-oriented.802.16 MAC is connection-oriented. Connection is a unidirectional mapping betweConnection is a unidirectional mapping betwe

en BS and SS MAC peers.en BS and SS MAC peers. A connection identifier (CID) is a 16-bit value tA connection identifier (CID) is a 16-bit value t

hat identifies a connection.hat identifies a connection.►A maximum of 65535 connections are supported foA maximum of 65535 connections are supported fo

r each DL and UL.r each DL and UL.

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Connection TypesConnection Types

►Basic connectionBasic connection Assigned to each SS after successful ranging.Assigned to each SS after successful ranging. To transport delay-intolerant basic MAC To transport delay-intolerant basic MAC

messages.messages. Identify the SS for managing per-SS Identify the SS for managing per-SS

functions. (BW grants in UL-MAP)functions. (BW grants in UL-MAP)

►Primary management connectionPrimary management connection Assigned to each SS after successful ranging.Assigned to each SS after successful ranging. To transport delay-tolerant basic MAC To transport delay-tolerant basic MAC

messages.messages.

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Connection TypesConnection Types

►Secondary management connectionSecondary management connection Assigned to each “managed” SS during Assigned to each “managed” SS during

the registration process.the registration process. To transport higher layer management To transport higher layer management

messages (SNMP, TFTP, and DHCP).messages (SNMP, TFTP, and DHCP).

►Transport connectionTransport connection Created and changed by Dynamic Service Created and changed by Dynamic Service

series messages (DSA, DSD, and DSC).series messages (DSA, DSD, and DSC). To transport user data.To transport user data.

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MAC Management MessagesMAC Management Messages

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Connection Identifiers Connection Identifiers ► Initial Ranging CID.Initial Ranging CID.►Basic CID.Basic CID.►Primary Management CID.Primary Management CID.►Secondary Management CID.Secondary Management CID.►Transport CID.Transport CID.►AAS Initial Ranging CID.AAS Initial Ranging CID.►Multicast Polling CID.Multicast Polling CID.►Padding CID.Padding CID.►Broadcast CID.Broadcast CID.

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Well-known Addresses and Well-known Addresses and IdentifiersIdentifiers

m is the maximum possible number of SSs that can be supported

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MAC HeadersMAC Headers►Stand-alone MAC headerStand-alone MAC header

6 bytes.6 bytes. The smallest possible information unit that caThe smallest possible information unit that ca

n be transported between two nodes. (with thn be transported between two nodes. (with the exception of HARQ MAPs)e exception of HARQ MAPs)

None of the stand-alone headers can be used None of the stand-alone headers can be used to encapsulate any payload.to encapsulate any payload.

It is a misnomer to call them “headers.”It is a misnomer to call them “headers.” BW request header and signaling header (defiBW request header and signaling header (defi

ned in other std.) are stand-alone MAC headerned in other std.) are stand-alone MAC headers.s.

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BW Request Header FormatBW Request Header Format000: incremental BR001: aggregate BR

Bandwidth request in bytes

Encryption Control

Header Check Sequence

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MAC HeadersMAC Headers

►Generic MAC headerGeneric MAC header Followed by the optional variable-size payloaFollowed by the optional variable-size payloa

d.d. Payload may consist of:Payload may consist of:

►MAC subheadersMAC subheaders►Management messagesManagement messages►Special payloadSpecial payload►Padding Padding

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Generic MAC Header FormatGeneric MAC Header FormatSubheader type CRC Indictor

Encryption Key Sequence

Header Check Sequence

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MAC SubheadersMAC Subheaders►For generic MAC header onlyFor generic MAC header only

5 4 3 2 1 0

Type

Mesh subheaderMesh subheaderARQ Feedback payloadARQ Feedback payload

Extended TypeExtended TypeIndicate whether the Packing or Fragmentation SIndicate whether the Packing or Fragmentation Subheaders is extended.ubheaders is extended.Fragmentation subheaderFragmentation subheaderPacking subheaderPacking subheaderDownlink: FAST-FEEDBACK allocation subheaderDownlink: FAST-FEEDBACK allocation subheaderUplink: Grant Management subheaderUplink: Grant Management subheader

Packing and Fragmentation subheaders are mutually exclusive.

Network Entry and Network Entry and InitializationInitialization

Once the SS has powered up, it begins the Once the SS has powered up, it begins the network entry and initialization process. After network entry and initialization process. After completing the steps of the process, the SS has completing the steps of the process, the SS has all the addresses and parameters it need to all the addresses and parameters it need to communicate with the rest of the network.communicate with the rest of the network.

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Network Entry and Network Entry and InitializationInitialization

►The procedures for entering and registering The procedures for entering and registering a new SS or a new node to the network.a new SS or a new node to the network.

►The procedures described here apply only The procedures described here apply only to PMP mode.to PMP mode.

BS New SS

Hey, I want to join the network.

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PhasesPhases► Scanning and synchronization to the DLScanning and synchronization to the DL►Obtain transmit parametersObtain transmit parameters► Initial rangingInitial ranging► SS basic capability negotiationSS basic capability negotiation► SS authorization and key exchangeSS authorization and key exchange► RegistrationRegistration► Establish IP connectivityEstablish IP connectivity► Establish time of dayEstablish time of day► Transfer operational parametersTransfer operational parameters► Establish provisioned connectionsEstablish provisioned connections

Optional

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Scanning and synchronization to Scanning and synchronization to the DLthe DL

►Achieve PHY synchronizationAchieve PHY synchronization Scan the possible channels of the Scan the possible channels of the

downlink frequency band of operation downlink frequency band of operation until it finds a valid downlink signal.until it finds a valid downlink signal.

►Then try to acquire the channel control Then try to acquire the channel control parameters for the DL and the UL.parameters for the DL and the UL. How?How?

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Obtain Transmit Parameters Obtain Transmit Parameters (1/4)(1/4)

►Achieve MAC synchronization.Achieve MAC synchronization. The SS achieves MAC synchronization once it The SS achieves MAC synchronization once it

has received at least one has received at least one DL-MAPDL-MAP message. message.

►Obtain downlink parametersObtain downlink parameters Retrieve parameters from the DCD messages.Retrieve parameters from the DCD messages. DCDDCD messages contain: messages contain:

►Frame duration, TTG size, RTG size, downlink Frame duration, TTG size, RTG size, downlink center frequency, BS ID, and more.center frequency, BS ID, and more.

►Downlink burst profilesDownlink burst profiles..

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Obtain Transmit Parameters Obtain Transmit Parameters (2/4)(2/4)

►SS want to know when BS broadcasts SS want to know when BS broadcasts channel parameters.channel parameters. SS can know it from SS can know it from DL-MAPDL-MAP.. Note that DL-MAP is encoded with well-Note that DL-MAP is encoded with well-

known parameters.known parameters.

►SS want to know the downlink channel SS want to know the downlink channel parameters.parameters. SS can know it from Downlink Channel SS can know it from Downlink Channel

Descriptor (Descriptor (DCDDCD) Message.) Message.

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Obtain Transmit Parameters Obtain Transmit Parameters (3/4)(3/4)

►Obtain uplink parametersObtain uplink parameters Retrieve parameters from the Retrieve parameters from the UCDUCD

messages.messages. UCD messages contain:UCD messages contain:

►Uplink center frequency, bandwidth request Uplink center frequency, bandwidth request opportunity size, ranging request opportunity opportunity size, ranging request opportunity size, and other PHY specific parameters.size, and other PHY specific parameters.

►Uplink burst profilesUplink burst profiles..

►Receive the UL-MAPReceive the UL-MAP So that SS can perform initial ranging. So that SS can perform initial ranging. Initial ranging opportunitiesInitial ranging opportunities..

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Obtain Transmit Parameters Obtain Transmit Parameters (4/4)(4/4)

►Now SS know downlink channel Now SS know downlink channel parameters, then it want to know parameters, then it want to know uplink channel parameters.uplink channel parameters. SS can know it from Uplink Channel SS can know it from Uplink Channel

Descriptor (Descriptor (UCDUCD) Message.) Message.

►The next question is when SS can send The next question is when SS can send requests to perform following requests to perform following procedures.procedures. SS can know it from SS can know it from UL-MAPUL-MAP

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Message FlowsMessage FlowsBS SS

DL/UL-MAP

SS power on

Power on sequence complete

Establish PHY synchronization

Wait for UCD

Obtain parameters for UL channel

Extract slot info for uplink

Wait for transmission opportunity to perform ranging

Start ranging process

DL/UL-MAP

UCD/DCD

DL/UL-MAP

DL/UL-MAP

DCD

DL/UL-MAP

UCD

DL/UL-MAP

Send DL/UL-MAP

Send UCD

Send DL/UL-MAP

Send DL/UL-MAP

Send DL/UL-MAP

Send DL/UL-MAP

Send UCD/DCD

Send DCD

Send DL/UL-MAP

Wireless channel

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Initial Ranging (1/3)Initial Ranging (1/3)

►What is ranging?What is ranging? Ranging is the process of acquiring the Ranging is the process of acquiring the

correct timing offset and power adjustments.correct timing offset and power adjustments. RNG-REQRNG-REQ//RNG-RSPRNG-RSP messages. messages.

►Two types of rangingTwo types of ranging Initial ranging: allow SS to join the network. Initial ranging: allow SS to join the network. Periodic ranging: allow SS to adjust Periodic ranging: allow SS to adjust

transmission parameters and maintain the transmission parameters and maintain the quality of RF communication link.quality of RF communication link.

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Initial Ranging (2/3)Initial Ranging (2/3)

► Initial Ranging accomplishes the Initial Ranging accomplishes the following:following: The time advance of SS transmissions is The time advance of SS transmissions is

adjusted to make the SS appear adjusted to make the SS appear collocated with the BS.collocated with the BS.

The transmission power of the SS is The transmission power of the SS is adjusted for optimal reception at the BS.adjusted for optimal reception at the BS.

The SS is allocated its The SS is allocated its Basic and Primary Management CIDsBasic and Primary Management CIDs..

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Initial Ranging (3/3)Initial Ranging (3/3)

► If two SS send there RNG-REQ in the same If two SS send there RNG-REQ in the same slot (opportunity)slot (opportunity) Collision.Collision. Call for Contention Resolution Algorithm.Call for Contention Resolution Algorithm. Binary exponential backoff is specified in the sBinary exponential backoff is specified in the s

pec.pec.

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Basic Capability NegotiationBasic Capability Negotiation►SS informs BS of its basic capabilities SS informs BS of its basic capabilities

by transmitting an SBC-REQ message by transmitting an SBC-REQ message with its capabilities set to “on”.with its capabilities set to “on”.

►BS responds with an SBC-RSP message BS responds with an SBC-RSP message with the intersection of SS’s and BS’s with the intersection of SS’s and BS’s capabilities set to “on”.capabilities set to “on”.

►Capabilities includes:Capabilities includes: Bandwidth allocation support, max. Bandwidth allocation support, max.

transmit power, current transmit power, transmit power, current transmit power, modulation type support, and more.modulation type support, and more.

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Authorization and Key Authorization and Key ExchangeExchange

►Perform authorization and key Perform authorization and key exchange procedures.exchange procedures.

►Details are skipped.Details are skipped.

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RegistrationRegistration

►The process by which SS is allowed entry iThe process by which SS is allowed entry into the network.nto the network.

►SS sends a REG-REQ message to BS.SS sends a REG-REQ message to BS.►BS responds with a REG-RSP message.BS responds with a REG-RSP message.►The SS is allocated its Secondary manageThe SS is allocated its Secondary manage

ment CID if the SS is managed.ment CID if the SS is managed.►Also negotiate the version of IP and the QAlso negotiate the version of IP and the Q

oS parameters for the secondary manageoS parameters for the secondary management connection.ment connection.

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Establish IP connectivityEstablish IP connectivity

►SS and BS shall negotiate IP version SS and BS shall negotiate IP version during REG-REQ/RSP exchange if the during REG-REQ/RSP exchange if the SS is managed.SS is managed.

►After registration, SS shall invoke After registration, SS shall invoke DHCP mechanisms in order to obtain DHCP mechanisms in order to obtain an IP address and any other an IP address and any other parameters needed to establish IP parameters needed to establish IP connectivity.connectivity.

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Establish Time of DayEstablish Time of Day

►That the SS and BS have the current That the SS and BS have the current date and time is required for time-date and time is required for time-stamping logged events by the stamping logged events by the management system.management system.

►The protocol by which the time of day The protocol by which the time of day shall be retrieved is defined in IETF shall be retrieved is defined in IETF RFC 868 (Time protocol).RFC 868 (Time protocol).

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Transfer Operation Transfer Operation ParametersParameters

► If the SS has a configuration file, the If the SS has a configuration file, the name is indicated in DHCP response.name is indicated in DHCP response.

►SS shall download the configuration file SS shall download the configuration file using TFTP (Trivial File Transfer using TFTP (Trivial File Transfer Protocol).Protocol).

►SS notify the BS by transmitting a TFTP-SS notify the BS by transmitting a TFTP-CPLT message when the file download CPLT message when the file download has completed successfully.has completed successfully.

►BS responds a TFTP-RSP message.BS responds a TFTP-RSP message.

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Establish Provisioned Establish Provisioned ConnectionsConnections

► In the case of a managed SS:In the case of a managed SS: The reception of the TFTP-CPLT message The reception of the TFTP-CPLT message

triggers the BS to start connection setup.triggers the BS to start connection setup.

► In the case of a unmanaged SS:In the case of a unmanaged SS: The successful completion of registration The successful completion of registration

serves as the trigger.serves as the trigger.

►Both are BS-initiated.Both are BS-initiated.►After at least one service flow has After at least one service flow has

been activated, the SS is capable of been activated, the SS is capable of sending and receiving user data.sending and receiving user data.

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Dynamic Service Dynamic Service EstablishmentEstablishment

►BS-initiatedBS-initiated

SS BSDSA-RSP

DSA-RSQ

Wireless channel

DSA-ACK

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Dynamic Service Dynamic Service EstablishmentEstablishment

►SS-initialed DSASS-initialed DSA The standard does not go into details on The standard does not go into details on

what actually triggers the DSA.what actually triggers the DSA. Triggering is just assumed to happen, Triggering is just assumed to happen,

stimulated by the upper layers when needed.stimulated by the upper layers when needed.

SS BS

DSA-RSQ

DSX-RVD

Wireless channel

DSA-RSP

DSA-ACK

This allows BS to take it time determining whether to admin the service flow

Bandwidth Bandwidth Request/Grand Request/Grand

MechanismMechanism

The BW request/grand mechanism for The BW request/grand mechanism for the IEEE 802.16 standard was chosen to the IEEE 802.16 standard was chosen to be efficient, low-latency, and flexible.be efficient, low-latency, and flexible.

63

RequestsRequests

►The mechanism that SS use to indicate The mechanism that SS use to indicate to the BS that they need uplink to the BS that they need uplink bandwidth allocation.bandwidth allocation.

►Requests are made on a per-connection Requests are made on a per-connection basis.basis.

►Grants are made to the SS (Basic CID), Grants are made to the SS (Basic CID), not to the connection.not to the connection.

►No explicit acknowledgments of No explicit acknowledgments of requests.requests.

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Requests (1/2)Requests (1/2)

►Contention-based bandwidth requests.Contention-based bandwidth requests. Transmit during contention period.Transmit during contention period. Broadcast polling.Broadcast polling. Multicast group polling.Multicast group polling. Focused contention transmission. (OFDM PHY)Focused contention transmission. (OFDM PHY) CDMA-based bandwidth requests. (OFDMA PHCDMA-based bandwidth requests. (OFDMA PH

Y)Y)►Contention-free bandwidth requests.Contention-free bandwidth requests.

Unicast polling.Unicast polling. PM bit. PM bit.

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Requests (2/2)Requests (2/2)

►Bandwidth stealingBandwidth stealing SS uses a portion of allocated BW for a SS uses a portion of allocated BW for a

connection to send another BW requests connection to send another BW requests rather than sending data.rather than sending data.

►Piggyback RequestPiggyback Request The bandwidth request is piggybacked The bandwidth request is piggybacked

onto a MAC PDU on an existing connection onto a MAC PDU on an existing connection with allocated BW.with allocated BW.

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GrantsGrants

►GPC modeGPC mode Grand Per Connection mode.Grand Per Connection mode. Only optionally allowed in IEEE Std 802.16-Only optionally allowed in IEEE Std 802.16-

2001.2001. No longer specified in IEEE Std 802.16-2004.No longer specified in IEEE Std 802.16-2004.

►GPSS modeGPSS mode Grand per Subscriber Station mode.Grand per Subscriber Station mode. Improves efficiency and latency. (smaller MAP)Improves efficiency and latency. (smaller MAP) An addition scheduler is required to allocate An addition scheduler is required to allocate

the granted bandwidth in each SS.the granted bandwidth in each SS.

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The ProblemsThe Problems

►The reality at the SS and the perception at The reality at the SS and the perception at the BS can get out of sync.:the BS can get out of sync.: BS does not hear a BW request.BS does not hear a BW request. SS does not hear the allocation in the MAP.SS does not hear the allocation in the MAP. BS scheduler decides it does not have BW BS scheduler decides it does not have BW

right now for the particular service.right now for the particular service. SS used BW for a purpose different from that SS used BW for a purpose different from that

originally requested. (e.g., bandwidth stealing)originally requested. (e.g., bandwidth stealing)

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Aggregate RequestsAggregate Requests

►BW request/grant mechanism is BW request/grant mechanism is designed to be self-correcting.designed to be self-correcting.

►After a period, if the SS still needs BW After a period, if the SS still needs BW for a service, it simply asks again.for a service, it simply asks again. SS issues an aggregate request.SS issues an aggregate request. To avoid BS’s perception becoming further To avoid BS’s perception becoming further

askew from reality by duplicate requests.askew from reality by duplicate requests. An aggregate request tells BS that the An aggregate request tells BS that the

current state of SS’s queue for that service, current state of SS’s queue for that service, allowing BS to reset its perception of that allowing BS to reset its perception of that service’s needs.service’s needs.

69

Incremental RequestsIncremental Requests

►There is a chance that a repeated There is a chance that a repeated aggregate request crosses the grant for aggregate request crosses the grant for that same bandwidth in the same frame.that same bandwidth in the same frame. It can cause wasted allocations to the SS.It can cause wasted allocations to the SS. It can be easily avoided by adding the It can be easily avoided by adding the

concept of incremental requests.concept of incremental requests. BS just add this BW requests to it current BS just add this BW requests to it current

perception of the BW needs for that service.perception of the BW needs for that service.

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Incremental or Aggregate?Incremental or Aggregate?

► In general, the airlink should be reliable.In general, the airlink should be reliable.►Therefore:Therefore:

Most BW requests typically would be incremeMost BW requests typically would be incremental.ntal.

Only periodic aggregate requests to ensure BOnly periodic aggregate requests to ensure BS does not deviate too far from reality.S does not deviate too far from reality.

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Other BW Request Options.Other BW Request Options.

►SI (Slip Indicator) bit.SI (Slip Indicator) bit. SS can set this bit, requesting BS to slightly SS can set this bit, requesting BS to slightly

increase the rate at which it automatically increase the rate at which it automatically allocates BW to SS. (up to 1% additional allocates BW to SS. (up to 1% additional BW)BW)

►PM (Poll Me) bit.PM (Poll Me) bit. SS can set this bit, indicating it has a BW SS can set this bit, indicating it has a BW

need on another connection.need on another connection. When BS sees the PM bit set, it knows the When BS sees the PM bit set, it knows the

SS needs to make a BW request and may SS needs to make a BW request and may poll it immediately.poll it immediately.

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Usage RulesUsage Rules

Service Service TypeType PollingPolling Contention Contention

RequestsRequestsPiggyBack RPiggyBack Requestsequests

BandwidtBandwidth Stealingh Stealing

UGSUGS PM bitPM bit Not Not allowedallowed

Not Not allowedallowed

Not Not allowed allowed

rtPSrtPS UnicastUnicast Not Not allowedallowed AllowedAllowed AllowedAllowed

nrtPSnrtPS AllAll AllowedAllowed AllowedAllowed AllowedAllowed

BEBE AllAll AllowedAllowed AllowedAllowed AllowedAllowed

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SummarySummary►MAC/PHY BasicsMAC/PHY Basics

Frame structureFrame structure Connections TypesConnections Types Header formatsHeader formats

►Network Entry ProceduresNetwork Entry Procedures After completing the procedures, SS can After completing the procedures, SS can

communicate with the network.communicate with the network.

►Bandwidth Request/Grand MechanismBandwidth Request/Grand Mechanism Contention-based bandwidth requestsContention-based bandwidth requests Contention-free bandwidth requestsContention-free bandwidth requests

74

SummarySummary

►More about IEEE 802.16More about IEEE 802.16 QoSQoS SchedulingScheduling Mesh modeMesh mode PHY detailsPHY details

75

ReferencesReferences

[1] IEE Std 802.16-2004, IEEE Standard for Local and Metro[1] IEE Std 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed Bpolitan Area Networks—Part 16: Air Interface for Fixed Broadband Wireless Accessroadband Wireless Access..

[2] Carl Eklund [2] Carl Eklund et alet al., ., WirelessMAN: Inside the IEEE 802.16 SWirelessMAN: Inside the IEEE 802.16 Standard for Wireless Metropolitan Area Networkstandard for Wireless Metropolitan Area Networks, IEEE P, IEEE Press, 2006.ress, 2006.

[3] http://www.ieee802.org/16/.[3] http://www.ieee802.org/16/.

The EndThe End

Backup MaterialsBackup Materials

78

DuplexingDuplexing►Duplexing defines how bidirectional comDuplexing defines how bidirectional com

munication is achieved between two devimunication is achieved between two devices or between a BS and a set of client devces or between a BS and a set of client devices in a PMP system.ices in a PMP system. Frequency Division Duplexing (FDD)Frequency Division Duplexing (FDD) Time Division Duplexing (TDD)Time Division Duplexing (TDD)

►Half-duplex: transmit or receive but not both simulHalf-duplex: transmit or receive but not both simultaneously.taneously.

►Full-duplex: transmit and receive simultaneously.Full-duplex: transmit and receive simultaneously.

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MultiplexingMultiplexing

►Refers to a mechanism in which a single Refers to a mechanism in which a single device transmits to multiple devices on a device transmits to multiple devices on a single channel.single channel. Frequency Division Multiplexing (FDM)Frequency Division Multiplexing (FDM)

►The transmitting device divides the time domain The transmitting device divides the time domain into multiple slots to communicate with multiple into multiple slots to communicate with multiple devices.devices.

Time Division Multiplexing (TDM)Time Division Multiplexing (TDM)►The transmitting device uses different frequencies The transmitting device uses different frequencies

to communicate with multiple devices.to communicate with multiple devices.

Orthogonal FDM (OFDM)?Orthogonal FDM (OFDM)?

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Multiple AccessMultiple Access

►Refers to the way that multiple devices Refers to the way that multiple devices access the medium, regardless of access the medium, regardless of whether the communication is many-whether the communication is many-to-one or many-to-many.to-one or many-to-many. Time Division Multiple Access (TDMA)Time Division Multiple Access (TDMA) Frequency Division Multiple Access Frequency Division Multiple Access

(FDMA)(FDMA) Orthogonal FDMA (OFDMA)Orthogonal FDMA (OFDMA) Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA)

Message FormatsMessage Formats

上窮碧落下黃泉上窮碧落下黃泉

82

Downlink Channel Descriptor Downlink Channel Descriptor MessageMessage

►Define the characteristics of a DL Define the characteristics of a DL physical channel.physical channel.

83

DCD Channel Encoding DCD Channel Encoding (partial)(partial)

84

SC Downlink_Burst_Profile SC Downlink_Burst_Profile

85

DCD Burst Profile Encodings – DCD Burst Profile Encodings – SC (partial) SC (partial)

86

DIUC Allocation – SCDIUC Allocation – SC

87

Uplink Channel Descriptor Uplink Channel Descriptor MessageMessage

►Define the characteristics of a UL Define the characteristics of a UL physical channel.physical channel.

88

UCD Channel Encoding UCD Channel Encoding (partial)(partial)

89

SC Uplink_Burst_Profile SC Uplink_Burst_Profile

90

UCD Burst Profile Encodings – UCD Burst Profile Encodings – SC (partial)SC (partial)

91

UIUC Allocation – SCUIUC Allocation – SC

92

DL-MAP MessageDL-MAP Message

93

SC DL-MAP IESC DL-MAP IE

94

UL-MAP MessageUL-MAP Message

95

SC UL-MAP IESC UL-MAP IE

96

RNG-REQ and RNG-RSPRNG-REQ and RNG-RSP

97

SBC/REQ and SBC-RSPSBC/REQ and SBC-RSP

98

REG-REQ and REG-RSPREG-REQ and REG-RSP

99

DSA-REQ and DSA-RSPDSA-REQ and DSA-RSP

100

DSA-ACKDSA-ACK

101

Service Flow EncodingsService Flow Encodings

102

Grant Management SubheaderGrant Management Subheader

FDD or TDD?FDD or TDD?

104

Advantages of FDD SystemsAdvantages of FDD Systems

►Continuous UL and DL Transmissions.Continuous UL and DL Transmissions. Reduce delay for MAC, ARQ, and channel Reduce delay for MAC, ARQ, and channel

information feedback.information feedback.

►Higher Immunity to System Interference.Higher Immunity to System Interference. Due to a large guard band.Due to a large guard band. BS-to-BS and SS-to-SS (or MS-to-MS) BS-to-BS and SS-to-SS (or MS-to-MS)

interference are generally negligible.interference are generally negligible. Note that there are still interferences Note that there are still interferences

between BS and MS.between BS and MS.

105

Issues and Challenges of FDD Issues and Challenges of FDD SystemsSystems

►Feedback Required for CSIT Acquisition.Feedback Required for CSIT Acquisition. CSIT: Channel State Information at the CSIT: Channel State Information at the

Transmitter.Transmitter. UL and DL channels are generally UL and DL channels are generally

uncorrelated, so the quality of CSIT will uncorrelated, so the quality of CSIT will degrade.degrade.

► Inflexible Traffic Allocation.Inflexible Traffic Allocation. Data traffic and Internet service have more Data traffic and Internet service have more

variation in traffic symmetry.variation in traffic symmetry. It would be desirable if the system could It would be desirable if the system could

allocate bandwidth dynamically with regard allocate bandwidth dynamically with regard to traffic demand.to traffic demand.

106

Issues and Challenges of FDD Issues and Challenges of FDD SystemsSystems

►Restrictive Band Allocation.Restrictive Band Allocation. FDD systems require a pair of frequency FDD systems require a pair of frequency

channels, it makes the FDD systems harder channels, it makes the FDD systems harder to fit into the scarce resource of spectrum.to fit into the scarce resource of spectrum.

►Guard Band.Guard Band. It represents a waste of resource.It represents a waste of resource.

►Higher Hardware Cost.Higher Hardware Cost. Requires a separate oscillator of different Requires a separate oscillator of different

frequency, an expensive duplexer, and a frequency, an expensive duplexer, and a sharp RF filter.sharp RF filter.

107

Advantages of TDD SystemsAdvantages of TDD Systems

►Channel Reciprocity.Channel Reciprocity. Channel state information at the receiver provChannel state information at the receiver prov

ides CSIT.ides CSIT. Better CSIT quality.Better CSIT quality.

►Dynamic Traffic Allocation/Traffic AsymmDynamic Traffic Allocation/Traffic Asymmetry.etry. Can distribute the bandwidth between UL and Can distribute the bandwidth between UL and

DL easily by altering their subframe durations.DL easily by altering their subframe durations.

108

Advantages of TDD SystemsAdvantages of TDD Systems

►Higher Frequency Diversity.Higher Frequency Diversity. Diversity is a well-known technique to enhance Diversity is a well-known technique to enhance

the system reliability in fading channels.the system reliability in fading channels. DL and UL signals have wider bandwidth, DL and UL signals have wider bandwidth,

which corresponds to an increase in frequency which corresponds to an increase in frequency diversity.diversity.

►Unpaired Band Allocation.Unpaired Band Allocation. Only one single contiguous channel is needed.Only one single contiguous channel is needed.

►Lower Hardware Cost.Lower Hardware Cost. The sharing of a single oscillator and the The sharing of a single oscillator and the

absence of a duplexer.absence of a duplexer.

109

Issues and Challenges of TDD Issues and Challenges of TDD SystemsSystems

►Guard Time between DL/UL Transitions.Guard Time between DL/UL Transitions. Reduces the efficiency of the system.Reduces the efficiency of the system.

►Duplexing Delay in MAC and ARQ.Duplexing Delay in MAC and ARQ. The traffic in both directions is discontinuous, The traffic in both directions is discontinuous,

and there is a delay between consecutive UL/and there is a delay between consecutive UL/DL subframes, called the duplexing delay.DL subframes, called the duplexing delay.

►Outdated CSIT.Outdated CSIT. The estimated CSIT may be outdated due to dThe estimated CSIT may be outdated due to d

uplexing delay.uplexing delay.

110

Issues and Challenges of TDD Issues and Challenges of TDD SystemsSystems

►Cross-Slot Interference.Cross-Slot Interference. This interference arises when neighboring TDThis interference arises when neighboring TD

D BSs either have different traffic symmetries D BSs either have different traffic symmetries or do not synchronize their frames.or do not synchronize their frames.

A major challenge in TDD systems.A major challenge in TDD systems.► Interoperator Interference.Interoperator Interference.

Different operators neither coordinate in netDifferent operators neither coordinate in network planning nor synchronize their frames awork planning nor synchronize their frames and traffic asymmetry. nd traffic asymmetry.

Would cause strong adjacent channel interferWould cause strong adjacent channel interference.ence.

111

FDD or TDD?FDD or TDD?

►TDD has received significant attention TDD has received significant attention because:because: Traffic asymmetry of high-bit-rate Traffic asymmetry of high-bit-rate

multimedia application.multimedia application. The flexibility of unpaired spectrum.The flexibility of unpaired spectrum.

►To alleviate cross-slot interference, the To alleviate cross-slot interference, the employment of sectored antennas and employment of sectored antennas and time slot grouping are very effective.time slot grouping are very effective.

112

FDD or TDDFDD or TDD

►More detailed discussion can be found in:More detailed discussion can be found in:Petwer W. C. Chan Petwer W. C. Chan et alet al., “The Evolution ., “The Evolution Path of 4G Networks: FDD or TDD,” Path of 4G Networks: FDD or TDD,” IEEE IEEE Communications MagazineCommunications Magazine, vol. 44, issue , vol. 44, issue 12, Dec. 2006, pp. 42-50.12, Dec. 2006, pp. 42-50.

113

Review of the OFDM SystemReview of the OFDM System

►OFDM stands for OFDM stands for Orthogonal Frequency DiOrthogonal Frequency Division Multiplexingvision Multiplexing..

► It was proposed in mid-1960s and used in It was proposed in mid-1960s and used in several high-frequency military system.several high-frequency military system.

► It is a It is a multicarrier transmissionmulticarrier transmission technique. technique. Divides the available spectrum into many subDivides the available spectrum into many sub

carriers, each one being modulated by a low dcarriers, each one being modulated by a low data rate stream.ata rate stream.

114

Single carrier and Multicarrier TranSingle carrier and Multicarrier Transmissionsmission

►Single carrier transmissionSingle carrier transmission Each user transmits and receives data stream Each user transmits and receives data stream

with only one carrier at any time.with only one carrier at any time.

►Multicarrier transmissionMulticarrier transmission A user can employ a number of carriers to traA user can employ a number of carriers to tra

nsmit data simultaneously.nsmit data simultaneously.

115

Single carrier and Multicarrier TranSingle carrier and Multicarrier Transmissionsmission

cos(2 )cf t

ib ( )s t

S/Pib

1cos(2 )f t

2cos(2 )f t

cos(2 )Nf t

∑( )s t

Single carrier transmission

Multicarrier transmission

NN oscillators are oscillators are requiredrequired

116

117

Service ClassesService Classes

►UGS (Unsolicited Grant Service)UGS (Unsolicited Grant Service)►rtPS (Real-Time Polling Service)rtPS (Real-Time Polling Service)►nrtPS (Non-Real-Time Polling Service)nrtPS (Non-Real-Time Polling Service)►BE (Best Effort)BE (Best Effort)