C WF WiMAX 16e Principle 20070528 a 2.0

8/12/2019 C WF WiMAX 16e Principle 20070528 a 2.0

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HUAWEI TECHNOLOGIES CO., LTD. Page 1

WiMAX Principle

HUAWEI TECHNOLOGIES CO., LTD.

www. huawei. com

ISSUE 2.0


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Know the technical standards of the WiMAX 16e.

Know the overall network structure of WiMAX 16e protocols.

Grasp the ground principles of WiMAX 16e physical layer and MAC

layer, especially the principle of the OFDMA and the definitions and

types of handover and QoS.

Grasp the key technologies and corresponding principles of

WiMAX 16e.

After this course, you will be able to:


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1 WiMAX Overview

2 WiMAX Network Structure

3 WiMAX Principle

4 WiMAX Key Technologies


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WiMAX Technical Advantages

LA/MBS/QOS/FSS/Mobility

OFDM/OFDMA MIMO/AAS Scalable Channel Bandwidth

NBTS

Multi-element

Transmitter

M

MS

Multi-element

Receiver

AMC/HARQ

64QAM

16QAM

From 1MHz to 20MHz

D D D U UD D D

D Downlink U Uplink

Spectrally-Efficient TDD

QPSK

WiMAX key technologies play an important role in the network planning.

The diversified and flexible configuration adds the complexities of network planning.


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Wireless Standard System and Its Evolution

IEEE 802.16 standard is a complement of wireless personal area network (WPAN)

IEEE 802.15 standards and wireless local area network (WLAN) IEEE 802.11

standards. It breaks the blank history of IEEE in the wireless metropolitan area

network (WMAN).


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Introduction to IEEE 802.16 Series

802.16d and 802.16e are two mainstream Um interface standards.

SN Technical Field

802.16 10-66 GHz, fixed broadband wireless access system air standard

802.16a 2-11 GHz fixed broadband wireless access system air standard

802.16c Supplementary provisions about the compatibility of 10-66 GHz fixed broadband wireless

access system

802.16d 2-66 GHz fixed wireless access system air standard

802.16e 2-66 GHz fixed and mobile broadband wireless access system air standard

802.16f Fixed broadband wireless access system air interface MIB requirements

802.16g Fixed and mobile broadband wireless access system air interface management plane f low and

service requirements


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1 WiMAX Overview


3 WiMAX Principle



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WiMAX IP-Based Network Structure


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WiM X Network Models and Interfaces

NAP

R1R3 R5

SS/MSS

R2

ASN CSN CSN

ASP Network OR

Internet

ASP Network OR

Internet

R4,

Another ASN

R2Visited NSP Home NSP

SS


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Establish layer 2 connections between the BS and the MS.

Transmit AAA messages to the home NSP of the MS.

Assist the high level to establish layer 3 connections with the MS and assign

the IP addresses.

Perform the radio resource management (RRM).

Perform the intra-ASN mobility management and handover.

Perform the intra-ASN paging and location management.

Establish and manage the tunnels between the ASN and the CSN.

Store the list of temporary subscriber information, which is similar to the

function of VLR in a 3G network.

Functions of the ASN


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Functions of the CSN Definition

It is a combination of a set of network functions and provides IP

connections for the WiMAX subscribers. The CSN consists of the router,

AAA agent or server, subscriber database, and Internet gateway equipment.

The CSN can a new network entity in a new WiMAX system or can realize

the functions of CSN through some existing network equipment.

Main functions of the CSN:

Establish the connections between subscribers and assign IP

addresses for the

Perform the Internet access.

Use the AAA agent or server.

Control the user system parameters-based QoS and license.

Establish and manage tunnels between the ASN and the CSN.

Perform the subscriber accounting and settlement.

Perform the inter-ASN mobility management.

Realize WiMAX services, such as location based service, point-to-

point service, multicast service, IMS, and emergency call.


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NAP & NSP

NAP: Network Access Provider

NSP: Network Service Provider

V-NSP: Visited NSP

H-NSP: Home NSP

NAPprovides the operation entities of network facilities required by the WiMAX wireless access

for one or more NSPs. The network facilities can consist of one or more ASNs.

NSPprovides IP connection based WiMAX services according to the agreements entered with the

WiMAX terminal uses at the service layer. As a result, the NSP can enter an agreement with other

ASPs or ISPs to provide specific services. In the roaming mode, the NSP must enter an

agreement with other NSPs. When a mobile terminal is located in the area served by the NSP

beyond the home NSP, the NSP that provides the services for the terminal is called V-NSP. The

CSN belongs to the NSP.


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ASN Reference Model

ASN reference model:

including single ASN-GW.

ASN reference model:

including multiple ASN-GWs.


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Profile A & C

GW

BS

R4

R3

R6

R1

Profile B

R4

R3

R1

BS +

ASNGW

Profile A: GW management handover

Profile C: BS management handover (GWs

transmits the handover messages only.)

ASN Profiles : Profile A, B & C

BSBS

Functions of Profile B


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Huawei WiMAX Network Structure and Interfaces

BS

BS

BS

ASN-GWHA

ROUTER

BS

BS

BS

ASN-GW

RAN entity

SS

AAA/Hserver

Charging Billing

InternetFW

SBC

Softswitch

MGWOMC-R

DNS server

DHCP server

ASN

ASN

R1

R6

R3

NGN / IMS

CSN 1

R4

PSTN /

PLMN


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Functions of the ASN-GW&BS

MAC/PHY function

Power control

Radio resource management

Paging managementLocation management

QoS management

Security management

Session management

Location management

Mobility management

RRM

PC

IP address managementQoS management

Tunnel management

Authentication

Accounting

Service control

BS functional entities ASN-GW functional entities


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1 WiMAX Overview


3 WiMAX Principle



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3 WiMAX Principle

3.1 WiMAX PHY Layer Principle

3.2 WiMAX MAC Layer Principle


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WiMAX PHY Layer Principle

Handling process of physical layer

Frame structure

Terms

Sub-carrier allocation modes

Data mapping

Modulation schemes


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BS Transmitting and Receiving Process

Transmitting: After being processed at the MAC layer, the downlink data is sent to the physical layer inthe format of MAC PDU. The MAC PDU arranges the data block size according to the allocation results of radio

resources at the MAC layer. After the data packets are processed through the channel coding, modulation, and

IFFT at the physical layer, the CP is added to form the integrated time domain OFDMA symbols, and then, the

symbols are transmitted in the downlink sub-frame structure through the RF processing.

Receiving:After the signals received by the antenna are processed through the RF intermediatefrequency, the baseband IQ data is sent to the baseband for processing. After the baseband receiving end

performs FFT, channel estimation, channel equalization, sub-carrier demapping, demodulation, and channel

decoding, the data packets are sent to the MAC layer through the interfaces. The competitive codes of the

Ranging and bandwidth request competitive slots in the uplink sub-frame must be detected.


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Terminal Transmitting and Receiving Process

Transmitting:The process is similar to that of BS. The frequency offset is pre-corrected. The Ranging andBW Request are generated at the physical layer and a code is selected according to the indication at the MAC

layer. After the modulation, they are mapped to competitive slots selected at the MAC layer. Later, they are thesame as the normal data.

Receiving:The process is similar to that of BS. The frequency synchronization is added. It is not requiredto detect the competitive codes of Ranging and bandwidth request.


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Frame structure

Terms


Data mapping

Modulation schemes

F St t


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Frame Structure

The physical frame includes the downlink sub-frame, uplink sub-frame, TTG, and RTG. The physical frame length and the respective duration of downlink sub-frame

and uplink sub-frame are broadcast by the BS through the DL_MAP broadcast message.

The downlink sub-frame consists of the Preamble, frame control header (FCH), DL_MAP, and downlink data burst. To assign flexibly and effectively the radio resources,

the resource allocation of each frame is variable. Each frame is broadcast through the broadcast message.

Preamble seizes the first symbol of downlink sub-frame. It is used for the SS to get the time and frequency synchronization and get the DL_PermBase, Segment

number, and IDcell information of the BS.

The position and size of the FCH are fixed in the downlink sub-frame. It is used to send some basic frame control information and demodulate the parameters of

DL_MAP message.

DL_MAP is followed by the FCH and is used to broadcast the resource allocation of downlink sub-frame to all the SSs. The resource allocation includes the

location, size, and burst profile of each downlink burst.

Downlink data burst carries the downlink data, and each downlink burst is planar in the frame structure. A downlink burst may include the data with multiple SSs.

After the demodulation, the SS can judge the data according the CID information in the MAC PDU header.

The uplink sub-frame consists of Ranging sub-channel and downlink data burst.

Ranging sub-channel is competitive and is used by the SS to originate the competitive Ranging and bandwidth request information. All the SSs can be used and

the BS is used for detection.

The uplink data burst carries the uplink data, and each uplink SS uses a burst.

TTG is the time interval between the downlink sub-frame and uplink sub-frame. It must be greater than the round-trip delay within the maximum coverage range. The

RTG is the time interval between the uplink sub-frame and downlink sub-frame.


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Frame structure

Terms


Data mapping

Modulation schemes

Terms


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Terms

Frequency domain symbolsBasic parameters

BWbandwidth

Nused available sub-carrier (include DCnsampling factor, 28/25 if BW are multiple of any 1.25,1.5,2,2.75 MHz,8/7 else

Import parameters

NFFT - 1285121024, 2048

Sampling frequency Fs = floor (n*BW/8000)*8000

Sub-carrier spacingf= Fs/ NFFTTb=1/ f,

Sampling periodf= Fs/ NFFTData sub-carrierDC sub-carrier

Guard sub-carrier


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Terms

Time domain symbolsTs: OFDMA symbol period Ts = Tb + Tg

Tb: Effective symbol period Tb = 1/ f

Tg: CP length Tg=G*Tb

CP: anti-multipath interface and symbol synchronization error

G : 1/32, 1/16,1/8, and 1/4. The MS is accessed initially, all

the possible CPs must be searched. The uplink CPs and

downlink CPs must be the same.

Terms


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Slot It is the minimum unit of resource allocation.

The handovers with different modulation modes and channel

schemes are performed between slots only. Two dimensions concept : sub-channel by OFDMA symbol

In the DL FUSC and optional FUSC, 1 slot1 sub-channel1

OFDMA symbol

In the DL PUSC, 1 slot1 sub-channel2 OFDMA symbol.

In the UL PUSC1 slot = 1 sub-channel3 OFDMA symbol.

In the AMC1 slot = 1 sub-channel2,3,or 6 OFDMA symbol.

Data region It indicates the two-dimensional allocation composed of a groupof continuous sub-channels and continuous OFDMA symbols.

One downlink data region can be used to transmit one or a group

of MSs.

The downlink is a regular rectangle, but the uplink is irregular.

Terms

Segment It indicates the segment of a group of

available sub-channels, or all the

available sub-channels.

A Segment is a MAC entity.

In PUSC, any segment used shall be

allocated at least the same number of

sub-channels as in group #0.

Terms


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Terms

Replacement zone

Each frame always starts and ends with the PREAMBLE. It is used by the MS to synchronized

with the BS, and the MS can get the SEGMENT symbol and IDCELL of the cell from the

PREAMBLE.

The PUSC replacement zone is followed by the PREAMBLE. The replacement zone is

mandatory and includes important broadcast information, such as FCH, and DL-MAP.

The optional replacement zone specified by the protocols is followed by the first PUSC

replacement zone. They can exist or do not exist in the frame structure.

In a downlink sub-frame, there are at most eight downlink replacement zones.


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Frame structure

Terms


Data mapping

Modulation schemes


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Sub-Carrier Allocation Mode 1

DL PUSC - Downlink partial Usage

Sub-Channels

The downlink PUSC replacement zone is

unique, that must exist in the frame

structure specified by the protocols.

DL PUSC with all SC -

PUSC with all sc indicates the PUSC

replacement mode when all the

bandwidth resources are used.

DL FUSC-Downlink Full Usage Sub-

Channels

321

PUSC with all SC / FUSCPUSC


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Sub-Carrier Allocation Mode 2

UL PUSC- Uplink Partial Usage

Sub-Channels

BAND AMC- Mobile WiMAX profile

specifies that both downlink and

uplink can use the BAND AMC

allocation mode. The sub-channels

of BAND AMC are continuous.

Whatever the uplink or downlink,

each sub-channel has an

independent pilot.


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Frame structure

Terms


Data mapping

Modulation schemes

Downlink Data Mapping


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Downlink Data Mapping

DL

SlotData Region

Uplink Data Mapping


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UL

Step 1 Allocate OFDMA slots to bursts.Step 2Map OFDMA slots within the UL allocation.

Uplink Data Mapping


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Frame structure

Terms


Data mapping

Modulation schemes

Modulation Schemes


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Modulation Schemes

Modulation schemes

QPSK quadrature phase-shift keyingQAM 16 quadrature amplitude modulation

QAM64 quadrature amplitude modulation


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3 WiMAX Principle

3.1 WiMAX PHY Layer Principle

3.2 WiMAX MAC Layer Principle

WiMAX MAC La er Principle


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WiMAX MAC Layer Principle

MAC Layer Overview

MPDU Construction

Network Access

Handover

QoS

MAC Layer Structure


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MAC Layer StructureConvergence sub-layer

Data packet

categorizer

Header

compression

Common part sub-layer

Mediaaccess

contr

ollayer(M/)

Physical

layer(PHY)

Packet data

processing

Network

access

Connection

management

Document dispatching

and QoS controlAir link control

Broadcast and

point-to-multi-

point service

Power

management

HO

management

Pairwise key management (PKM2), extensible authentication protocol (EAP),

message authentication code (CMAC), and AES-CCM encryption

1024.512FFT, sub-channel queue, sub-channel arrangement, time division

multiplexing frame structure, adaptive modulation coding (AMC), hybrid

automatic repeat request (H-ARQ), channel quality information channel

(CQICH), Adaptive Beamforming, space time code (STC), and multiple input

multiple output (MIMO)

Security sub-layer

MAC Layer Overview


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y

The MAC layer is oriented to the connections. Each connection corresponds to a service flow. The service

flow defines the QoS parameters of PDU transmitted over the connection.

The design core of the MAC protocol is the concept of service flow architecture on the connection. The

service flow provides an uplink/downlink QoS management mechanism. An MS is based on a connection to

request the bandwidth. Actually, the MS is associated with the service flow.

Each connection is identified by a 16-digit CID. The basic three pairs of management connections are Basic

management connection (emergent time and short MAC layer management message), Primary management

connection (carrying longer MAC management messages of some delays), and Secondary management

connection (tolerate the messages of delay based on the DHCP, TFTP, and SNMP). Different connections

have different QoS levels. The uplink CID and downlink CID of a connection are the same.

Resource dispatching

Priority queue

Service flows

Logic connection of

network QoS

Data packet categorizer

WiMAX MAC L P i i l


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MAC Layer Overview

MPDU Construction

Network Access

Handover

QoS

MPDU Format


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MPDU Format

MPDU format

Fixed MAC header, variable load, and optional CRC

MAC header format

The downlink has a Generic MAC layer only and is located in the front of each

MAC PDU. The MAC PDU includes the MAC management message and CS data.

The uplink defines two MAC headers: Generic MAC header and the MAC header

without payload. The Generic MAC header is located in the front of each MAC

PDU, which includes the MAC management message and CS data. For the latter,

there is no payload and CRD at the back of the MAC header.

MPDU construction method

Agreed/cascaded/segment/packet


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MAC Layer Overview

MPDU Construction

Network Access

Handover

QoS

Network Access


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The network access is a process of an MS performing the normal

communication from power-on to network access.

The network access includes two phases, power-on and access.

Objectives of the power-on process The power on process is the initial operation after an MS is powered on and before

accesses the network.

During the power- on, an MS must get the basic information of the BS.

During the power-on, an MS must realize the uplink and downlink synchronization

with the BS.

During the power-on, an MS must notify the BS of the access.

Objectives of the access process An MS determines the traffic channel related information.

An MS negotiates with the BS over the related information of the service flow.

Contents of Network Access


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Cell selection

Downlink synchronization

Obtain the transmission parameters

Uplink synchronization

Negotiating basic capabilities

Authentication and key exchange

Negotiating the high-layer parameters

Obtain the IP address

Obtain the system time

Obtain the FTP parameters

Create the preliminary service flow



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MAC Layer Overview

MPDU Construction

Network Access

Handover

QoS

Applications Scenarios of Handover


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pp

When an MS moves, the MS must change the connected BSto get better signals because of the impacts of fading and

interface.

From the other BS, the MS can get better QoS.

The handover can be used to realize the load balancing.

Hard Handover (HO)


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The hard handover indicates the process of an MS moving from the radio resource interface

provided by the serving BS to another radio resource interface provided by the target BS. The

radio resources provided by the target BS are limited or the network topology structure with the

serving BS is restricted, the target BS cannot become the diversity BS of the serving BS. It

provides the hard handover mechanism for an MS for handover.

In the case of hard handover, the BS capability parameters, service flow parameters, and MAC

layer information may be changed.

The MS has two choices, break-before-make HO or BBM, and make-before-break HO or MBB.

The BBM indicates the MS releases the connection with the serving BS, and then leaves the

serving BS and makes an attempt to access the target BS. The MBB indicates the MS leaves the

serving BS first and makes an attempt to the target BS, but does not release the connection with

the serving BS. After the MS accesses successfully the target BS or the resource reservation timer

configured by the serving BS for the MS expires, the MS releases the connection with the serving

BS. Correspondingly, the serving BS releases the connection saved for the MS.

Fast BS Switching (FBSS)


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The FBSS indicates the process of an MS moving from the radio resource interface

provided by the serving BS to another radio resource interface provided by the diversity

BSs of the serving BS. During the FBSS, the MS can perform the data communication witha BS of the diversity BSs only, but each diversity BS establishes connection resources for

the MS. The neighbor BS can become a diversity BS of the serving BS when the radio

resources and network topology structure meet the requirements. The diversity BS can

become the serving BS when the radio communication signals meet the requirements. The

active serving BS in the diversity BSs is also called the Anchor BS.

In this mode, the MS communicates with a unique serving BS (Anchor BS) but remains a

list of Active BSs. The MS can choose fast a better Active BS from the list to replace the

active Anchor BS. The fast switching process of an MS selecting the BS can improve the

link quality during the handover.

The FBSS includes the Active Update or Diversity Set Update an Anchor BS Update. The

former indicates that the neighbor BS becomes a diversity BS of the serving BS. The latter

indicates the diversity BS becomes the active serving BS and the serving BS becomes the

diversity BS.

Soft Handover (SHO) or Macro-Diversity Handover

(MDHO)


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(MDHO)

The SHO indicates the process an MS moving from one or more radio resource interfaces provided by the

macro-diversity BS to another one or more radio resource interfaces provided by the macro-diversity BS. During

the MS moving, the MS synchronously performs the data communication with one or more BSs in the macro-

diversity BS. Each macro-diversity BS is the serving BS of the MS. In all the serving BSs, only one BS is the

main control diversity BS, that is called Anchor BS. When the radio resources and the network topology structure

meet the requirements, the neighbor BS can become the macro-diversity BS. When the radio communication

signals meet the requirements, the macro-diversity BS can become the main control BS.

The SHO also includes Active Update or Diversity Set Update and Anchor BS Update. The former indicates that

the neighbor BS can become the macro-diversity BS. The latter indicates that the macro-diversity BS can

become active main control BS, but the original main control BS becomes the macro-diversity BS.

The MS moves from the Um interface under one or more BSs to another Um interface. On the downlink, two or

more BSs can synchronously transmit the same data packets of MAC/PHY protocols, and the MS realizes the

diversity combining. On the uplink, two or more BSs can receive the data of the same MS and the MS realize thediversity combining among the BSs.

Differences Between 16e SHO and 16e Hard HO


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In the hard handover mode, an MS can communicate with a Severing BS only. No MAC

layer information (handover between two MAC entities) is shared between the Serving BS

and Target BS. In the soft handover, all the BSs in the active set share a MAC entity,

including the MAC layer status information, such as service flow, ARQ, and encrypted

authentication.

The hard handover requires a synchronization and access process in the target BS (the

exchange of some messages can be omitted according to actual needs). The soft handover

does not require a synchronization and access process in the target BS.

During the hard handover, the services are interrupted for a short period of time (even for

the MBB, there is a conversion process of from receiving and transmitting data at the

source side to receiving and transmitting data at the target side. There is also an access

process. Thus, the handover time may be longer. During the soft handover, the services are

not interrupted, because an MS can communicate synchronously with multiple BSs. Even

when an MS disconnects a link with a BS or performs a handover, the services are notaffected. However, the soft handover occupies more Um interface resources.

WiM X M C Layer Principle


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MAC Layer Overview

MPDU Construction

Network Access

Handover

QoS

QoS Measurement Parameters


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Subscriber requirements (end to end)

Bandwidth Loss rate

Delay

Delay jitter

Network performance

Throughput: It indicates the maximum transmission speed of

measured objects, such as system, equipment, specific connection,

and service. The throughput can be measured through thebandwidth.

16e Service Types


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IEEE 802.16 protocols support multiple types of services.

IEEE802.16d protocols classify all the services into the following

four categories according to the service characteristics: Unsolicited grant: the corresponding service is the Unsolicited Grant Service

(UGS).

Real-time polling: the corresponding service the real-time polling service (rtPS).

Non-real-time polling: the corresponding service is the non-real-time polling

service (nrtPS).

Best effort: the corresponding service is the best effort (BE) service.

IEEE802.16E extends a type of service.

Extended real-time polling service (ertPS)

Relationship between QoS and Applications


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QoS Policy


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QoS policy: It is used to determine the QoS level for a service. RSVP,

Diffserv, and MPLS protocols provide different mechanisms for different

traffic. QoS policy regulates the use methods of the mechanisms.

Common Open Policy Service (COPS) technology: Through the

centralized policy management and distributed and simplified network

management (defined by the RFC2748), it is used for exchanging the

policy information between the policy server and client based on the

status inquiry an the response mechanism protocols.

QoS Assurance from the MAC Layer


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The MAC layer of the 802.16 system supports multiple types of services and

processes the data packets according to the connections. Each connection has

own QoS parameters and/or dispatching type. Thus, the MAC layer of the802.16 system controls the QoS in the unit of connection.

On the downlink, the BS distributes the connected data according to the actual

data in the Buffer and the requirements of connected QoS.

On the uplink, the bandwidth used by the SS is granted by the BS in the unit of

frame. If the BS does not grant the bandwidth for the SS, the SS cannot send

the uplink data. The BS cannot directly knows the generated data in the SS,

five dispatching types are defined according to different service types. The

dispatching types correspond to different modes of uplink bandwidth allocation.


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1 WiMAX Overview


3 WiMAX Principle


WiMAX Key Technologies


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WiMAX Key Technologies

OFDM / OFDMA

TDD

AMC

HARQ

MIMO

AAS

OFDM Principle


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The idea of the OFDM is to convert the data in a serial and parallel mode to get the N-path parallel

data flows. Each path of data flow is modulated to the mutual-quadrature sub-carrier, and the sub-

carrier spectrum can be overlapped.

The OFDM system realizes the Quadrature carrier modulation through the highly-effective FFT/IFFT

algorithm.

P/SIFFTS/Ps(t)Add

Cyclic

Prefix

n(t)

S/PFFTP/Sr(t)Remove

CyclicPrefix

Transmitter

Receiver

Channel

Advantages of OFDM High spectrum efficiency


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High spectrum efficiency In the OFDM system, the sub-carriers are overlapped and

mutually quadrature. The traditional multi-carrier system

requires the protection band. Thus, the spectrum efficiency is

improved greatly.

Effectively resist the multi-path interference The OFDM system transmits the high speed data in a parallel

mode, so the anti-multipath interference capability of the

system is improved greatly.

Effectively resist the frequency selective

fading In the OFDM system, the technologies, such as coding,

frequency diversity, channel weighting, and dynamic sub-

carrier allocation are used to resist the frequency selective

fading.

Easily compatible with other technologies It is a modulation technology in essence.

Realize easily the channel estimation and

equalization Use the IFFT/FFT effective DSP technologies to realize the

modulation and demodulation of the OFDM to reduce the

system complexity and make it more real-time.

0 100 200 300 400 500 600-30

-25

-20

-15

-10

-5

0

5

10

Frequency

FrequencySlec

tive

Fading

OFDMA Principle


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HUAWEI TECHNOLOGIES CO., LTD.Page 64

OFDM-based modulation

Divide the available sub-carriers of each OFDM symbol into multiple sub-channels. Each subscriber can occupy one or more sub-channels.

TDMA+FDMA

Advantages of OFDMA

The granularity of resource allocation is smaller and the resource allocation


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The granularity of resource allocation is smaller and the resource allocation

becomes more flexible. In the same OFDMA symbol, multiple subscribers can

be accessed. The uplink can be used to improve the coverage through the power

concentration. The downlink coverage is not restricted. If the downlink

coverage is restricted, the coverage is improved through the repeated codes or

power concentration. In the PUSC mode, some sub-carriers are cooperated to

improve the coverage.

Scalable: At the OFDMA physical layer, the system with different bandwidths

uses different FFT points, which is called Scalable OFDMA. For example, the

1.25 MHz bandwidth uses 128 points and 5 MHz bandwidth uses 512 points.

Easily compatible with other technologies: The OFDMA is modulated on a

basis of OFDM, so it is easily compatible with other technologies

(MIMO/AAS/CDMA.

TDD Characteristics

Advantages: high spectrum efficiency and low CAPEX/OPEX


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Require no duplexer and save the cost. The equipment complexity is low. The TDD equipment either transmit or receive. Thus, the

equipment design is simple. The FDD system synchronously transmit and receive and a good isolation must be established between the

receiving bands. Thus, the equipment cost is high, and it reliability is lower than that of TDD system.

The uplink and downlink proportions are scalable and more applicable to the symmetrical services.

The features of uplink and downlink channels are symmetrical and the open loop power control without overhead can be used. It

facilitates the support of multi-antenna technologies and further improves the spectrum efficiency.

The frequency can be selected at random in the specified band, or the band can be used at odds and ends. unlike the FDD, the band

must be selected in pairs. Thus, it is more flexible to select the frequency of the TDD.

The transmitting and receiving of the TDD use the same band. Thus, the new technologies are easily compatible. For example, the

smart antenna considers the signal receiving and transmitting at single band. For the FDD, the band is considered in pairs, that is, the

TDD has advantages over the use of the cost in terms of new technology.

In the FDD system, the uplink frequency is different from the downlink frequency. The power control is realized by the feedback and

the accurate power control is difficult.

Disadvantages: easily cause the interference

Require the synchronization of the overall network and require external synchronous sources

The system receives and transmits the interference.

Impacts on the network planning (especially when multiple networks coexist)

AMC Principle


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Measure the receive channels and adaptive handover modulation modes and codingschemes are used to optimize the throughput-SNR curve according to the measurement

results.

The coding schemes include CC, BTC, CTC, and LDPC. The modulation modes include

the QPSK, 16QAM, and 64QAM.

The adaptive modulation selects the required modulation mode according to the channel

conditions. When the high modulation mode, such as 64-QAM is used, the high SNR can

be used to conquer other interferences to keep the BER.

To improve the coverage range, select the low modulation mode, such as QPSK. If the

subscriber is close to the BS, select the high modulation mode.

Combination Between the AMC and the Power Control


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802.16e protocols define the uplink power control only.

The uplink power control includes the inner loop powercontrol and outer loop power control.

Inner loop power control: the uplink CINR is a judgment basis. The four parameters,

cinr-target, cinr-upper-threshold, cinr-lower-threshold, and max-adjust-step are used

for power control.

Outer loop power control: the uplink BLER is a judgment basis. The five parameters,

bler-target, bler-upper-threshold, bler-lower-threshold, Max-adjust-step, and qos-type-

index are used for power control.

Combination between the AMC and the inner loop power

control

In the AMC, each coding scheme has two values, cinr-upper-threshold and cinr-lower-threshold. When the uplink CINR of terminal measured by the BS is higher than cinr-

upper-threshold, the coding scheme is improved by an order. If the CINR is lower than

cinr-lower-threshold, the coding scheme is reduced by an order.

HARQ- Concept and Types


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HARQ (hybrid ARQ): Combination between Automatic repeat request (ARQ)

and forward error correction (FEC)

According to the mode for combining FER codes of the HARQ at the receiving

end, the HARQ is classified into three types:

Type I HARQ -The receiving end decodes and monitors the packet quality through the

FEC. If an error exists in the packets, the retransmission is required and the error

packets are discarded. TypeHARQ The receiving end stores the error packets and combines the packets

transmitted for multiple times.

Chase CombingEach retransmission codes the data packets through the same FEC

and the decoder at the receiving end combines the copies of the transmission packets

according to the received SNR.

TypeHARQ incremental redundancy: Increase gradually the redundancy of

transmission codes. The receiving end combines and decodes the data frames of the

same information received.

Realization of HARQ in the WiMAX


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In the 802.16 protocols, the HARQ can be used at the MAC layer or PHY layer.

Use HARQ at the MAC layer

Realized in the MPDU: A HARQ Packet includes one or more MAC PDUs and the CRC is added.

The CRC is of 16bits, in the format of CRC16-CCITT.

Use HARQ at the PHY layer:

Realized in the burst: Add the CRC with 16 bit in the transmission of burst. This CRC corresponds to

the CRC in the MPDU.

HARQ channel: Downlink HARQ, UL is allocated for an ACK/NAK channel. The channel isallocated through the HARQ ACK Region Allocation IE message of the UL_MAP. Uplink

HARQ connection, the downlink provides the ACK through the HARQ MAP message.

HARQ - Performance


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Orange curve: HARQ that is not combined by the receiver. The performance is similar to that

of traditional ARQ.

Blue curve: HARQ of diversity combining by the receiver

Red curve: Add the HARQ in the FEC redundancy mode

HARQ improves the performance with a low SNR, which helps improve the cell edge coverage

probability.

MIMO System Model


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MIMO system: A link has the radio system with multiple INs and OUTs.

Transmitting end: After being pre-processed, the imported high speed bit stream becomes

the symbol stream that complies with the constellation rule. And then, after the space time

coding, the symbol stream becomes Nt parallel sub-symbol streams. The sub-symbol

streams are transmitted from the Nt transmitting antennas at the same time.

Receiving end: After the signal vectors received from the Nr receiving antennas are inversewith the transmitting end, the original information bit is restored.

C1(k) r1(k)

Signal

source

Space

Time

coding

Spacetime

decoding

Signal

sink

C2(k)

CN(k)

r2(k)

rN(k)

MIMO TypesSpace division multiplexing (SM): Matrix B and Matrix C (four antennas)


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Divide one data flow at a high transmission rate into a group of data flows at a low transmission rate. Independently

code, modulate and transmit the different data flows from different antennas, and use the same frequency and slots.

Space time coding (STC): Matrix A

Through the coding, the information included in the symbols transmitted at the different antennas is associated.

Adaptive HO MIMO

Perform a handover between the multiplexing and diversity to make a balance

between the capacity and link quality.

FFT

IFFT

FFT

IFFT

Serial/

parallelconver

sion

Space

timecoding

Signal

Coding

AndmappingInput data

FFTafter removing

the cyclic

prefixSpaceTime

Decoding

OrSignal

detection

Channel estimation

Parallel/

serialconversion

Signal

demodulation

and

demapping

IFFTand

add the cyclic

prefix

Output data

IFFT

andadd the

cyclic prefix

a1

a2

am

OFDM

OFDM

OFDM

TX

TX

TX

OFDM

RX

RX

RX

OFDM

OFDM

a1

a2

am

OFDM

OFDM

OFDM

TX

TX

TX

OFDM

RX

RX

RX

OFDM

OFDM

a1

a2

am

OFDM

OFDM

OFDM

TX

TX

TX

OFDM

RX

RX

RX

OFDM

OFDM

Inputdata

a1

a2

am

OFDM modulation

OFDM modulation

OFDM modulation

TX

TX

TX

Spacemultiplexing

detectionOFDM demodulation

Receivedata

RX

RX

RX

Channel estimation

OFDM demodulation

OFDM demodulation

Vector

coder

FFT

after removingthe cyclic

prefix

Impacts of MIMO on the Coverage


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Coverage radius

In diversity mode only Bring the diversity gain and increase the cell coverage radius.

In multiplexing mode only

Improve the cell edge rate to increase the cell coverage radius.

Coverage probability

When the coverage radius is fixed, the coverage gain obtained

through the MIMO technology is reserved for the shadowing

fading margin to improve the coverage probability of signal.

Impacts of MIMO on the Capacity

Sector throughput and spectrum efficiency


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g p p y

In multiplexing mode only

Both the transmitting end and receiving end use multiple sets of antennas. Through the

space dimensional resources, each antenna transmits the separate data flows. When

the transmit power and bandwidth are increased, the transmission capacity and

spectrum efficiency of the radio communication system are improved by multiplies.

In diversity mode only

Add the cell radius to increase the proportions in the high-order modulation mode to

improve the transmission capacity and spectrum efficiency of the radio communicationsystem.

Peak rate

In multiplexing mode only, theoretically speaking, the air interface peak rates

of uplink and downlink are increased proportionally with the number of

antennas. In uplink cooperation MIMO mode, only the sector throughput is increased, but

the peak rate of single user is not increased.

Basic Concepts of AAS


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AAS: Smart antenna technology defined in the IEEE 802.16e protocols

Beamforming (for single user) and SDMA (for multiple users), which require

multiple arrays of antennas for the BS, but without requirements for terminals

Interferers

Desired Signal

Beamforming of single user Multi-user SDMA

AAS Types


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AAS has three types: HO beam antenna array, quasi- dynamic multi-beam antenna array, and adaptive antenna

array

Beam HO AAS: Use a group of pre-designed overlapped beam to cover the whole space domain. The system

outputs the big beams to irradiate each subscriber.

Quasi-dynamic AAS: Each array element uses the phase shifter to directionally receiver and transmit the signals.

Actually, it receives the signals at maximum.

Adaptive AAS: To adapt the change of electromagnetic field, adjust the weighted value of each unit antenna

according to the algorithm and optimization rules. And then, accumulate the weighted space sensor signals to form

the required beam.

Interference InterferenceInterference

Interference

Beam handover

antennaQuasi-dynamic multi-

beam antenna

Adaptive multi-beam

antenna

Figure 1

Impacts of AAS on the CoverageTraffic channel

The SNRs of single user and with Gaussian nose are increased


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The SNRs of single user and with Gaussian nose are increased.

Uplink: The equivalent power is improved by 42 multiplies. The noise is improved by M

multiplies. The equivalent SNR is improved by M multiples, that is, 10logM (M indicates

the number of array elements).

Downlink: The signal receiving capacity of terminal is increased by M multiplies, that is,

20logM, and the noise is not changed. The equivalent SNR is improved by 20logM

(including the array total power gain 10logM).

The intra-frequency CIR is improved.

Broadcast channel

The shaping fails. The maximum power required is 10 lg MdB higher than that of traffic

channel of the AAS antenna.

Coverage rules

When the number of array elements is smaller than 8, the coverage of Preamblechannel is similar to that of the shaped traffic channel.

If the Preamble channel uses the CSD technology, the coverage is better.

It is hard to make the CSD and AAS compatible.

Impacts of AAS on the Capacity

SNR rise


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SNR rise

After the smart antenna with M array elements is used, the SINR is

improved by about 10lgM. When the SINR is increased, the capacity is

increased.

The intra-frequency CIR is increased, it means that the closer

frequency mode can be used to improve the capacity.

SDMA

The capacity can be improved by multiplies.

The capacity improvement is closely related to the AAS realization

method, frequency multiplexing mode, number of array elements and

the cell radius. In the case of capacity estimation, the specific

beamforming algorithm and SDMA realization method must be used.

AAS MIMO

Comparison Between the AAS and the MIMO


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Characteristics Use the dependent characteristics of

different antenna signals. The distancebetween antennas is small.

Use the independent charters tics of different

antenna signals. The distance betweenantennas is large.

Application The performance is good in the macro

cell and the antenna position is high.

The performance is good in the micro cell and

indoors.

BS There are many channels and the impact

on the system structure is large. The

optimization of system structure is

required specially for the AAS. It is hard

to be compatible with the traditional

system structure.

Two channels, for baseband signal processing,

small impact on the system structure, and

easily compatible with traditional system

structure

Terminal Small impact, add partial signaling only Great impact, the terminal must support

multiple antennas.

The AAS can be cooperated with the MIMO, for example, use the bipolarization array. The AAS is used

between the antennas with the same polarization, and the MIMO is used between the antennas with

different polarization. The subscribers of different channels in the same cell can select the AAS or

MIMO. As a result, the system complexity is increased.


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Thank You

www. huawei. com

C WF WiMAX 16e Principle 20070528 a 2.0

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