DESIGN FOR TEST

Updated: October 28, 2009

The IEEE 802.16 standard

WiMAX is based on the IEEE 802.16 standard and on ETSI HiperMAN. The latest

version of IEEE 802.16, 802.16-2004 (previously known as Revision D, or 802.16d), was

ratified in July 2004. 802.16-2004 is a wide-ranging standard, that includes previous

versions (802.16-2001, 802.16c in 2002, and 802.16a in 2003) and covers both LOS and

NLOS applications in the 2-66 GHz frequencies. As is customary with IEEE standards, it

specifies only the Physical (PHY) and Media Access Control (MAC) layers.

The changes introduced in 802.16-2004 were focused on fixed and nomadic applications

in the 2-11 GHz frequencies. Two multi-carrier modulation techniques are supported in

802.16-2004: OFDM with 256 carriers and OFDMA with 2048 carriers. The first

WiMAX Forum certification profiles are based on OFDM as defined in this version of

the standard.

In December 2002, Task Group e was created to improve support for combined fixed and

mobile operation in frequencies below 6 GHz. Work on the 802.16e amendment is

approaching completion and its ratification is expected by the end of 2005. The new

version of the standard introduces support for SOFDMA (a variation on OFDMA) which

allows for a variable number of carriers, in addition to the previously-defined OFDM and

OFDMA modes. The carrier allocation in OFDMA modes is designed to minimize the

effect of the interference on user devices with omnidirectional antennae. Furthermore,

IEEE 802.16e offers improved support for Multiple Input Multiple Output (MIMO) and

Adaptive Antenna Systems (AAS), as well as hard and soft handoffs. It also has

improved power-saving capabilities for mobile devices and more extensive security

features. Both OFDM- and OFDMA-based products can take advantage of the newlyadded

capabilities.

As with 802.16-2004, 802.16e will incorporate previous versions of the standard and add

paper, we refer to 802.16e WiMAX profiles as most likely to adopt SOFDMA, and to

802.16-2004 profiles as using OFDM with 256 carriers.

The new version of the 802.16 standard is backwards-compatible, so new specifications

of the OFDM mode are compatible with previous versions. However, OFDM and

SOFDMA modes are not compatible as they are based on two distinct modulation

techniques. As a result, a single-mode OFDM CPE will not work within a SOFDMA

network and, conversely, an SOFDMA CPE will not work within an OFDM network.

WiMAX Forum Profiles

WiMAX is a set of profiles based on IEEE 802.16 developed by the WiMAX Forum and

its members. While 802.16 supports a wide range of frequencies (up to 66 GHz), channel

sizes (1.25 MHz to 20 MHz) and applications (LOS and NLOS; PTP and PMT), the

WiMAX profiles narrow the scope of 802.16 to focus on specific configurations.

The selection of a limited number of profiles is essential to ensure interoperability across

vendors and to generate the economies of scale that lead to lower prices and a more

appealing technology.

The choice of profiles is driven by market demand, spectrum availability, regulatory

constraints, the services to be offered, and vendor interest. For instance, the availability

of spectrum for broadband wireless access services in several countries motivated the

creation of initial profiles in the 3.5 GHz band. The availability of license-exempt

spectrum and the demand for fixed services determined the creation of a profile in the 5.8

GHz band. Demand for mobile services and spectrum availability make the 2.3 GHz and

2.5 GHz bands likely targets for future 802.16e profiles.

WiMAX Forum profiles are defined by the following parameters:

Spectrum band.

Duplexing. Two options are available: Time Division Duplex (TDD) for operators

with unpaired or license-exempt spectrum, and Frequency Division Duplex (FDD).

FDD requires two channels, one for uplink and the other for downlink traffic. In a

TDD network traffic occupies a single channel, with uplink and downlink traffic

assigned to different time slots.

Channel bandwidth. The channel bandwidth is highly dependent on the spectrum

allocated by regulators. Initial profiles are limited to 3.5 MHz and 7 MHz in the

licensed spectrum as these are the prevalent spectrum channels allocated in the 3.5

GHz band. As wider channels are made available to operators, so the WiMAX

Forum members will add certification profiles with wider channel bandwidths.

IEEE standard. 802.16-2004 profiles use OFDM with 256 carriers. 802.16e profiles

are most likely based on SOFDMA. Only the latter support mobility.

All the certification profiles based on 802.16-2004 are based on a common system

profile. This includes WiMAX specifications that remain the same whatever the

frequency, channel size and method of duplexing. A new system profile is currently

being developed for 802.16e certification profiles. If there is sufficient interest from the

vendor community, a third system profile may be introduced for 802.16-2004 products to

support portability and limited mobility. The initial profiles defined by the WiMAX

Forum (Table 2) support fixed and nomadic access in the 3.5 GHz and 5.8 GHz bands.

The WiMAX Forum has defined certification releases as shown in Figure 1. The

timetable for product certification is driven by product availability since three products

are needed to test interoperability across vendors. The certification process includes

interoperability testing with products from other vendors, and compliance testing for

conformance against the WiMAX system profile.

The first certification release for 802.16-2004 is currently under way and includes

products submitted within the two 3.5 GHz profiles with a channel bandwidth of 3.5

MHz. The scope of the certification and the list of tests will be extended during

subsequent releases. The first release will focus on certification of the air protocol. The

second release will add functionality needed to support outdoor services (QoS and

security, for instance). The third release will include support for indoor user devices

The profiles for 802.16e have not yet been announced, as the 802.16e amendment to the

standard has not yet been finalized. The most likely bands for the first mobile profiles are

2.3 GHz and 2.5 GHz. Better indoor coverage and support for mobile or portable devices

make bands below 3 GHz the best targets. However, additional profiles in higher

frequencies (3.3 GHz, 3.5 GHz or even 5.8 GHz) may be added if there is sufficient

demand for 802.16e-based products for fixed or nomadic access.

The WiMAX Forum plans to announce new profiles supporting mobility in the coming

months and to open certification labs in the third quarter of 2006. The first 802.16e

WiMAX Forum CERTIFIED products are expected by the first quarter of 2007.

A comparison between 802.16-2004 and 802.16e profiles

The two versions of WiMAX reflect the demand for products that are either optimized for

fixed or for mobile access. The requirements for the two types of access vary and

different solutions are required to meet them.

Several optional features that are supported in both 802-16.2004 and 802.16e profiles are

more likely to be implemented in 802.16e products simply because mobile services stand

to gain more from the added functionality. Among these, improved support for MIMO

and AAS will bring a substantial increase in throughput and NLOS capabilities

.

The profiles for 802.16e have not yet been announced, as the 802.16e amendment to the

standard has not yet been finalized. The most likely bands for the first mobile profiles are

2.3 GHz and 2.5 GHz. Better indoor coverage and support for mobile or portable devices

make bands below 3 GHz the best targets. However, additional profiles in higher

frequencies (3.3 GHz, 3.5 GHz or even 5.8 GHz) may be added if there is sufficient

demand for 802.16e-based products for fixed or nomadic access.

The WiMAX Forum plans to announce new profiles supporting mobility in the coming

months and to open certification labs in the third quarter of 2006. The first 802.16e

WiMAX Forum CERTIFIED products are expected by the first quarter of 2007.

A comparison between 802.16-2004 and 802.16e profiles

The two versions of WiMAX reflect the demand for products that are either optimized for

fixed or for mobile access. The requirements for the two types of access vary and

different solutions are required to meet them.

Several optional features that are supported in both 802-16.2004 and 802.16e profiles are

more likely to be implemented in 802.16e products simply because mobile services stand

to gain more from the added functionality. Among these, improved support for MIMO

and AAS will bring a substantial increase in throughput and NLOS capabilities

OFDM and SOFDMA

A key difference between 802.16-2004 and 802.16e profiles is the multiplexing

technique: the first uses OFDM and the second will most likely use OFDMA.

WiMAX profiles based on 802.16-2004 are better suited to fixed applications that use

directional antennae because OFDM is inherently less complex than SOFDMA. As a

result, 802.16-2004 networks may be deployed faster and at a lower cost. In addition,

802.16-2004 WiMAX Forum CERTIFIED products will be available earlier and will be

adopted by service providers

that plan to deploy a network

in the near future.

OFDMA gives 802.16e

profiles more flexibility

when managing different

user devices with a variety of

antenna types and form

factors. It brings a reduction

in interference for user

devices with omnidirectional

antennas and improved

NLOS capabilities that are

essential when supporting

mobile subscribers. Subchannelization

defines subchannels

that can be

allocated to different

subscribers depending on the

channel conditions and their

data requirements (Figure 2).

This gives the operator more

flexibility in managing the

bandwidth and transmit

power, and leads to a more

efficient use of resources.

For instance, within the same time slot more transmit power can be allocated to a user

with less favorable channel conditions, while lowering the power for users in better

locations. Improved in-building coverage can be achieved by allocating higher power to

sub-channels assigned to indoor user devices.

Sub-channelization in the uplink brings additional performance improvement, as transmit

power from the user device is severely limited. In OFDM, user devices transmit using the

entire carrier space at once (Figure 3). OFDMA supports multiple access, which allows

user devices to transmit only through the sub-channel(s) allocated to them. In OFDMA

with 2048 carriers and 32 sub-channels, if only one sub-channel is allocated to a device,

all the transmit power will be concentrated in 1/32 of the spectrum available and may

bring a 15 dB gain over OFDM. Multiple access is particularly advantageous when wide

channels are used.

SOFDMA brings an additional advantage over OFDMA. It scales the size of the Fast

Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing

constant across different channel bandwidths. Constant carrier spacing results in a higher

spectrum efficiency in wide channels, and a cost reduction in narrow channels.

Handoffs and roaming

Support for handoffs is another crucial addition in the 802.16e amendment for mobile

access. The ability to maintain a connection while moving across cell borders is a

prerequisite for mobility and will be included as a requirement in the 802.16e system

profile. While the 802.16-2004 standard offers optional handoff capabilities, support for

handoffs is not required by the 802.16-2004 system profile.

802.16e WiMAX will support different types of handoff, ranging from hard to soft and it

is up to the operator to choose among them. Hard handoffs use a break-before-make

approach . the user device is connected to only one base station at any given time .

which is less complex than soft-handoffs but has a high latency. Soft handoffs are

comparable to those used in some cellular networks and allow the user device to retain

the connection to a base station until it is associated with a new one (make-before-break

approach), thus reducing latency. While applications like mobile Voice over Internet

Protocol (VoIP) or gaming greatly benefit from low-latency soft handoffs, hard handoffs

typically suffice for data services. QoS and Service Level Agreements (SLAs) are

maintained during handoffs.

Roaming capabilities across service providers can be implemented in both 802.16-2004

and 802.16e WiMAX, but they are especially valuable for portable and mobile access.

The WiMAX Forum does not expect to include roaming requirements in the 802.16e

system profile, as roaming is a higher level capability that goes beyond the scope of the

certification program, which focuses on the PHY and MAC layers. The Service Providers

Working Group and the Network Working Group within the WiMAX Forum are working

towards identifying the functional requirements for roaming and establishing a roaming

platform.

Acronyms

3GPP 3G Partnership Project

3GPP2 3G Partnership Project 2

AAS Adaptive Antenna System also Advanced Antenna System

ACK Acknowledge

AES Advanced Encryption Standard

AG Absolute Grant

AMC Adaptive Modulation and Coding

A-MIMO Adaptive Multiple Input Multiple Output (Antenna)

AMS Adaptive MIMO Switching

ARQ Automatic Repeat reQuest

ASN Access Service Network

ASP Application Service Provider

BE Best Effort

BRAN Broadband Radio Access Network

CC Chase Combining (also Convolutional Code)

CCI Co-Channel Interference

CCM Counter with Cipher-block chaining Message authentication code

CDF Cumulative Distribution Function

CDMA Code Division Multiple Access

CINR Carrier to Interference + Noise Ratio

CMAC block Cipher-based Message Authentication Code

CP Cyclic Prefix

CQI Channel Quality Indicator

CSN Connectivity Service Network

CSTD Cyclic Shift Transmit Diversity

CTC Convolutional Turbo Code

DL Downlink

DOCSIS Data Over Cable Service Interface Specification

DSL Digital Subscriber Line

DVB Digital Video Broadcast

EAP Extensible Authentication Protocol

EESM Exponential Effective SIR Mapping

EIRP Effective Isotropic Radiated Power

ErtPS Extended Real-Time Polling Service

ETSI European Telecommunications Standards Institute

FBSS Fast Base Station Switching

FCH Frame Control Header

FDD Frequency Division Duplex

FFT Fast Fourier Transform

FUSC Fully Used Sub-Carrier

HARQ Hybrid Automatic Repeat reQuest

HHO Hard Hand-Off

HiperMAN High Performance Metropolitan Area Network

HMAC keyed Hash Message Authentication Code

HO Hand-Off or Hand Over

HTTP Hyper Text Transfer Protocol

IE Information Element

IETF Internet Engineering Task Force

IFFT Inverse Fast Fourier Transform

IR Incremental Redundancy

ISI Inter-Symbol Interference

LDPC Low-Density-Parity-Check

LOS Line of Sight

MAC Media Access Control

MAI Multiple Access Interference

MAN Metropolitan Area Network

MAP Media Access Protocol

MBS Multicast and Broadcast Service

MDHO Macro Diversity Hand Over

MIMO Multiple Input Multiple Output

MMS Multimedia Message Service

MPLS Multi-Protocol Label Switching

MS Mobile Station

MSO Multi-Services Operator

NACK Not Acknowledge

NAP Network Access Provider

NLOS Non Line-of-Sight

NRM Network Reference Model

nrtPS Non-Real-Time Polling Service

NSP Network Service Provider

OFDM Orthogonal Frequency Division Multiplex

OFDMA Orthogonal Frequency Division Multiple Access

PER Packet Error Rate

PF Proportional Fair (Scheduler)

PKM Public Key Management

PUSC Partially Used Sub-Carrier

QAM Quadrature Amplitude Modulation

QoS Quality of Service

QPSK Quadrature Phase Shift Keying

RR Round Robin (Scheduler)

RRI Reverse Rate Indicator

RTG Receive/transmit Transition Gap

rtPS Real-Time Polling Service

RUIM Removable User Identity Module

SDMA Space (or Spatial) Division (or Diversity) Multiple Access

SF Spreading Factor

SFN Single Frequency Network

SGSN Serving GPRS Support Node

SHO Soft Hand-Off

SIM Subscriber Identify Module

SIMO Single Input Multiple Output

SINR Signal to Interference + Noise Ratio

SLA Service Level Agreement

SM Spatial Multiplexing

SMS Short Message Service

SNIR Signal to Noise + Interference Ratio

SNR Signal to Noise Ratio

S-OFDMA Scalable Orthogonal Frequency Division Multiple Access

UL Uplink

UMTS Universal Mobile Telephone System

USIM Universal Subscriber Identify Module

VoIP Voice over Internet Protocol

VPN Virtual Private Network

VSF Variable Spreading Factor

VSM Vertical Spatial Multiplexing

WiFi Wireless Fidelity

WAP Wireless Application Protocol

WiBro Wireless Broadband (Service)

WiMAX Worldwide Interoperability for Microwave Access

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