phuong - 802 16presentationphuongnguyen 681fall2007 upgradedversion (1)

8/12/2019 Phuong - 802 16PresentationPhuongNguyen 681Fall2007 UpgradedVersion (1)

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IEEE 802.16Wireless MAN

(Wireless Metropolitan Network)

A Technical Overview of the WirelessMANTMAir Interfacefor Broadband Wireless Access, Carl Eklund, Roger B.

Marks, Kenneth L. Stanwood and Stanley Wang June 2002Presented by Phuong Nguyen

For 681 Advanced Computer Network Fall 2007


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Topics

Introduction

Physical Layer

MAC Layer (Medium Access Control)

References


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Introduction

Goal:Provide high-speed Internet access to home and business

subscribers, without wires.

Base stations(BS) can handle thousands of subscriber stations(SS)

BS can control all data traffic goes between BS and SS through the

allocation of bandwidth on the radio channel.

802.16 is a Bandwidth on Demand system

Access control prevents collisions.

Supports

Legacy voice systems

Voice over IP

TCP/IP

Applications with different QoS requirements.

Main advantage:

fast deployment, dynamic sharing of radio resources and low cost


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Architecture

Uplink:direction from SS to BS

Downlink:direction from BS to SS

Source: D. Miorandi Create Net


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IEEE 802.16 Extension

802.16 standard was approved in 2001

802.16.1 (10-66 GHz, line-of-sight, up to 134Mbit/s)

802.16.2 (minimizing interference between coexisting WMANs.)

802.16a Support lower frequency 2 to 11Ghzboth licensed and license-exempt

So reach more customers with less expensive

Lower data rates Support Mesh-Network

802.16b Increase spectrum to 5 and 6GHz

Provide QoS (for real-time voice and video service)

802.16c Represents a 10 to 66GHz system profile

802.16d Improvement and fixes for 802.16a

802.16e Addresses on Mobile

Enable high-speed signal handoffs necessary for communications with usersmoving at vehicular speeds

Focus on 802.16.1


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SAP: Service Access Point

PDU: Protocol Data Unit

Accept, perform classification, process higher

PDUs

Deliver CS PDU to MAC SAP

Receive CS PDUs from the peer entity

System access, bandwidth

allocation

connection establishment,

connection maintenance

Authentication, security

key exchange,

encryption

IEEE Std 802.16 protocol layering, showing SAPs

Multiple specifications

each appropriate to

frequency range (ex:

802.16.1 10-66GHz up to

134Mbit/s) and application


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Physical layer

10-66GHz line of sight propagation. US use 20-25MHz, EU use

28MHz

Pointtomultipoint BS transmit a TDM (Time Division

Multiplexing) signal with individual SSs allocatedtime slots

serially Access the uplink by time division multiple access (TDMA)

Burst single-carrier modulation

Allows use of directional antennas

Allows use of two different duplexing schemes:

Frequency Division Duplexing (FDD)

Time Division Duplexing (TDD)

Support for both full and half duplex stations


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Time Division Duplexing (TDD)

Uplink and downlink share a channel but do not transmit simultaneously



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Frequency Division Duplexing (FDD)

Uplink and downlink operate on separate channels sometimesimultaneously

Support full duplex SSs which can transmit and receivesimultaneously

Half duplex which do not

Adaptive Data Burst Profiles

Transmission parameters (e.g. modulation and FECsettings) can be modified on a frame-by-frame basis for eachSS.

Profiles are identified by Interval Usage Code (DIUC and

UIUC) Using both

TDM (Time Division Multiplexing) and

TDMA (Time Division Multiple Access)


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Media Acces Control (MAC)

Supports many different physical layer specifications, both

licensed and unlicensed.

Connection orienteded

ConnectionID (CID)

Channel access: UL-MAP

Defines uplink channel access

Defines uplink data burst profiles

DL-MAP

Defines downlink data burst profiles UL-MAP and DL-MAP are both transmitted in the beginning of

each downlink subframe (FDD and TDD).


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FDD Downlink subframe



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Uplink subframe

Source: D. Miorandi Create NetGrant bandwidth to specific SSs

SSs transmit in assigned allocation using burst profiles UIUC in UL-MAP


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MAC sublayers

Service Specific Convergence Sublayer

ATM CS defined for ATM service

Packet CS defined for IPv4, IPv6, Ethernet

Classify service data unit SDUs to properMAC connection, preserve or enable QoS and

enable bandwidth allocation


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Common Part Sublayer

Point to multi point

Request bandwidth, associate QoS, transport and routing data

SS has universal 48bit MAC address. BS has 48-bit Base Station ID(not MAC address)

Connections identified by 16-bit CID.

used to distinguish between multiple uplink channels associated with the same

downlink channel

many higher-layer sessions may share same CID (with same service parameters)

Used in MAC PDU


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Common Part Sublayer

SS enter network is assigned 3 management

connections Basic connection: transfer short critical MAC messages

Primary connection: transfer longer more delay torelent messages

(authentication, connection setup)

Secondary connection: transfer of standard base management

messages such as DHCP, TFTP, SNMP

In addition, transport connection for contracted services

Other additional connections: Contention based initial access

Broadcast transmissions for Downlink, polling of SSs if needed

Additional connections for multicast


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MAC PDU format

MAC PDU Formats

-The MAC PDU (protocol data unit) is the data unit exchanged between the

MAC layers of the BS and its SSs.

-Consists of a fixed-length MAC header, a variable-length payload, and an

optional cyclic redundancy check (CRC).

MAC Header FormatsTwo MAC header formats: The first is the generic MAC headerthat begins

each MAC PDU containing either MAC management messages or CS data.

The second is the bandwidth request headerused to request additional

bandwidth.


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MAC PDU header


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Transmission of MAC PDUs

Transmission Convergence sublayer is between MAC and PHY

Transformation of variable length MAC PDUs into fixed length FEC block

MAC Message SDU 1 SDU2

PDU1 PDU2 PDU3 PDU4 PDU5MAC PDUs

P FEC1 FEC2 FEC3Burst

Preamble FEC blocks


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MAC Management Messages (rules)

Handle initial ranging, negotiation, SS authentication and registration,

and describing downlink and uplink

link describing:

BS transmits channel uplink and downlink descriptor messages (UCD

and DCD) at periodic intervals

UCD and DCD contain burst profile: info on modulation, error-

correction, preamble length, etc.

uplink and downlink map messages (UL-MAP, DL-MAP) define burst

start times and allocate access to corresponding link channel

ranging: subscriber stations transmit ranging requests at

initialization and then periodically

determines power and burst profile changes (starts with lowest power

level and then moves up)

Create - net


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MAC Management Messages

Uplink schedule service

Unsolicited Grant Service (UGS)

Real-Time Polling Service (rtPS)

Non-Real-Time Polling Service (nrtPS) Best Effort Service

Bandwidth request and grants

SS authentication and registration


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Bandwidth request and allocation

SSs may request bw in 3 ways: Use the contention request opportunities interval upon

being polled by the BS (multicast or broadcast poll).

Send a standalone MAC message called BW request in an

allready granted slot.

Piggyback a BW request message on a data packet.

BS grants/allocates bandwidth in one of two modes:

Grant Per Subscriber Station (GPSS)

Grant Per Connection (GPC)

Decision based on requested bw and QoS requirements vsavailable resources.

Grants are realized through the UL-MAP.Source: D. Miorandi Create Net


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Approaches to Bandwidth Grant

Two basic approaches on the way to grant BW Bandwidth Grant per Subscriber Station (GPSS)

Base station grants bandwidth to the subscriber station

Subscriber station may re-distribute bandwidth among its connections,

maintaining QoS and service-level connections agreements

Suitable for many connections per terminal; off-loading base stationswork

Allows more sophisticated reaction to QoS needs

Low overhead but requires intelligent subscriber station

Bandwidth Grant per Connection (GPC)

Base station grants bandwidth to a connection Mostly suitable for few users per subscriber station

Higher overhead, but allows simpler subscriber


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Bandwidth allocate by Unicast Polling

1. BS allocates space for the SS in

the uplink subframe.

2. SS uses the allocated space to

send a bw request.

3. BS allocates the requested

space for the SS (if available).

4. SS uses allocated space to send

data.

Poll(UL-MAP)

RequestAlloc(UL-MAP)

Data

BS SS



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Initial Ranging

Upon learning what parameters to use for its Initial ranging, SS

scanning for UL_MAP messages present in every frame

SS will send the burst using minimum power setting and try again if it

does not get response

BS command timing advance and power adjustment to SS based on

SS request. Also provide SS with basic and primary management CIDs

SS receive response:

If the response indicates corrections, the SS makes these corrections

and sends another ranging request.

If the response indicates success, the SS is ready to send data on the

UL.


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Negotiation Capabilities and Authentication

Negotiation Capabilities

After successful completion of initial ranging, the SS sends acapability request message to the BS describing its capabilities interms of the supported modulation levels, coding schemes and rates,and duplexing methods.

The BS accepts or denies the SS, based on its capabilities. Authentication

After negotiation, the BS authenticates the SS and provides keymaterial to enable the ciphering of data.

The SS sends the X.509digital certificate and certificate of

manufacturer and a description of the supported cryptographicalgorithms to its BS.

The BS validates the identity of the SS, determines the cipheralgorithm and protocol that should be used, and sends anAuthentication Reply contain Authorization Key encrypted with SSs

public key.


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Registration and IP connectivity

Registration SS will register the network after successful completion of authentication

It sends a registration request message to the BS, and the BS sends aregistration response to the SS.

The registration exchange includes

IP version support

SS managed or non-managed support ARQ parameters support

Classification option support

CRC support

Flow Control

IP connectivity After registration SS attains an IP address via DHCPand establishes time of

day via Internet Time Protocol


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References

IEEE Standard 802.16: A technique overview of the

WirelessMANTMAir Interface for Broachband Wireless

Access,Carl Eklund, Roger B. Marks, Kenneth L.

Stanwood and Stanley Wang, June 2002.

IEEE std 802.16 standard 2004 part 16 (895 pages)


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