The Evolution of Mobile WiMAX

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Jose Puthenkulam, Intel’s WiMAX Standards Director, is a telecommunications
renaissance man.  In addition to driving standards development and building
consensus with the progression of the IEEE 802.16 family of standards (as Vice
Chair of the IEEE 802.16 Working Group), Jose is also an active user of
Clearwire’s Mobile WiMAX service in Portland, and a very knowledgeable
technologist in the emerging 4G eco-system.  He is a standards expert –
having worked in IEEE, IETF, 3GPP, WiMAX Forum and GSM Association.  He is
also involved in social networking, Internet telephony, video games, mobile
devices, and keeps tabs on the latest wireless gizmos and gadgets.  Jose
regularly contributes to www.wimax360 and IEEE ComSoc-SCV discussions (open to
all IEEE members).  More about Jose at the end of this article.

Backgrounder:

The IEEE 802.16 Working Group on Broadband Wireless Access Standards is
responsible for developing the IEEE 802.16 WirelessMAN® Standards for Wireless
Metropolitan Area Networks.  In September 2003, a revision project called
802.16Rev-d commenced aiming to align the standard with aspects of the European
Telecommunications Standards Institute (ETSI) HIPERMAN standard and to define
conformance and test specifications.  This project concluded in 2004 with
the release of 802.16-2004 (see list of IEEE 802.16 Standards below), which
superseded the earlier 802.16 documents, including the a/b/c amendments. 
802.16-2009 is now the new base standard.  For more information, see the
list below and http://wirelessman.org/ or
http://ieee802.org/16/.

WiMAX, an acronym for Worldwide Interoperability for Microwave Access, provides wireless transmission of data using
a variety of transmission modes, from point-to-multipoint links to portable and
fully mobile internet access.  The WiMAX Forum, a non profit
organization formed to promote the adoption of WiMAX compatible products and
services, is "chartered to establish certification processes that achieve
interoperability, publish technical specifications based on recognized
standards, promote the technology and pursue a favorable regulatory
environment."

A Brief History of the "Mobile WiMAX" Standard, Profiles and Certification

The objective of the IEEE 802.16e "Mobile WiMAX" standard was to provide
mobility as well as fixed broadband wireless access with high data rates and a
relatively long- range coverage area, much like cellular technologies today. 
The mobile broadband access system also had to include functions to enable
handoff between base stations as a mobile subscriber moved between cells. 
An important objective was to significantly reduce the cost of WiMAX
infrastructure per unit data rate by significantly increasing the system
capacity compared to current 3G cellular systems. 

The MAC sub-layer from 802.16-2004 was to be retained in parts, in order to
carry "IP packets." However, the MAC was significantly enhanced to support
mobility features like Handover, Sleep and Idle mode power management.  The
security features were also improved in 802.16e.

With strong interest from Intel and the KT/ WiBro community, work on the IEEE
802.16e-2005 (AKA Mobile WiMAX) standard commenced in December 2002, when the
IEEE-SA Standards Board approved an initial Project Authorization Request (PAR)
for "Mobile WiMAX." That was well before the IEEE 802.16d-2004 (Fixed WiMAX)
standard was completed.  Note that IEEE 802.16e is not compatible with
802.16d-2004, because it’s PHY layer has to support both mobile and fixed
wireless access (the MAC layer has some commonality between the two standards).

By November of 2003 – almost one year after the 802.16e Task Force (TF) was
created -interest was muted and progress slow due to the perceived competition
from the (Qualcomm led) IEEE 802.20 standards effort (AKA Mobile Broadband
Wireless Access).  Having established very well respected standards
credentials in the IETF and 3GPP, Jose was selected to lead the Intel team that
was developing the IEEE 802.16e standard. 

In late 2003, Jose started to contact interested parties to encourage them to
move forward at a more rapid pace.  His goal was to make 802.16e a very
robust and efficient broadband wireless technology when implemented according to
the standard.  Jose met with several companies seeking their effort and
support of the newly authorized 802.  16e "Mobile WiMAX" standards project. 
Samsung, Alvarion, Runcom, Motorola, Nortel, Alcatel and Siemens were a few of
those companies.  At the time, there was already a very similar standards
effort ongoing in South Korea.  It was known as "High Speed Portable
Internet" and was spearheaded by ETRI, Samsung and KT.  The challenge
was to harmonize the functions and features of the Korean effort with those
proposed to the 802.16e Task Group.

In early 2004 a Scalable OFDMA (Orthogonal Frequency Division Multiple
Access) proposal was drafted, which found broad support at the March 2004 IEEE
802.16 meeting.  Consensus was starting to build.  The 802.16e PAR was
modified, amended, and approved by the IEEE-SA Standards Board in September
2004.  The main purpose was to include new PHY layer capabilities based on
OFDMA, which was documented by several very supportive statements from the
industry.

In late 2004 to early 2005, Jose and several of his Intel team members drove the
effort to include a state of the art security feature in the emerging standard,
while contributing to the specifications for beam forming and MIMO (Multiple
Input Multiple Output).  Those capabilities were included in the IEEE
802.16e final draft that was completed in October 2005.  The 802.16e
standards work was iterated through twelve drafts, based on thousands of
comments and hundreds of contributed documents.  IEEE Std 802.16e-2005 was
approved in December 2005, setting the stage for commercialization of the
technology.

"The IEEE 802.16e standard gives service operators the ability to provide a wide
range of new and revolutionary high-speed, mobile wireless applications and
services that will greatly improve people’s way of life," said Brian Kiernan,
Chair of the IEEE 802.16e Task Group at the time.

In late 2004 to early 2005, the WiMAX Forum started "Mobile WiMAX" profile
specifications, based on the soon to be completed IEEE 802.16e standard. 
The profiles were targeted at certification and inter-operability testing. 
There were two types of profiles that were developed in two stages:

- Wave 1:  SISO configuration Primarily for WiBro (South Korea) in
2.3 GHz
- Wave 2:  MIMO based profile for global deployment in 2.5, 2.3 and
3.5 GHz bands

By June 2008, approximately 2 ? years after the 802.16e-2005 standard was
ratified, the WiMAX Forum

certified the first Wave 2  products for 2.5GHZ bands.

IEEE 802.16e-2005 Scope:  Fixed and Mobile Broadband Wireless Access

The PHY layer of this standard incorporates several advanced radio transmission
technologies, such as OFDMA, MIMO, adaptive modulation and coding, and adaptive
forward error correction (FEC), is designed to provide broadband wireless
capability using a well-defined quality-of-service (QoS) framework.  The
standard is restricted to the access network and is not an end-to-end network
architecture, as some people falsely believe.

The standard also provides enhancements to IEEE Std 802.16-2004 to support
subscriber stations moving at vehicular speeds and thereby specifies a system
for combined fixed and mobile broadband wireless access.

Functions to support higher layer handover between base stations or sectors are
specified.  Operation is limited to licensed bands suitable for mobility
below 6 GHz.  Fixed IEEE 802.16 subscriber capabilities are not
compromised.  In addition to mobility enhancements, this document contains
substantive corrections to IEEE 802.16-2004 regarding fixed operation."

Graceful degradation and return to normal speed are important attributes of the
adaptive modulation process specified in IEEE 802.16e.  When the detected
signal strength weakens, the transmitter will incrementally reduce the
modulation (symbol) rate while maintaining the connection.  When the
detected signal strength increases, the transmitter will bump up the symbol rate
accordingly, thereby facilitating a graceful return to normal speed operation. 
This attribute is quite important for truly mobile subscribers, as the radio
signal conditions will change while the subscriber is moving (within a cell or
to an adjacent cell).  Adaptive modulation works in each direction of
transmission (i.e.  upstream and downstream).

A Network Reference Model is described in 802.16e-2005 Annex G (Informative- not
Normative).  It includes "groups of BS units providing network service (not
necessarily contiguous) to authorized Mobile Stations in a geographic region. 
A group of BS units that share administrative affiliation, and are connected by
a backbone (wired or unwired) are referred to as a provider network. 
Multiple provider networks of varying design, performance, and
ownership/administration may coexist in the same region.  Provider networks
may employ specialized servers for AAA (Authorization, Authentication and
Accounting), management, provisioning, and other functions.  These servers
responsible are collectively termed Authentication and Service Authorization
Servers (ASA-servers) this specification.  A provider may deploy single or
multiple ASA-servers, and may do so in a centralized or distributed manner."

List of Important IEEE 802.16 Standards

- IEEE 802.16-2004 IEEE Standard for Local and metropolitan area networks Part
16: Air Interface for Fixed Broadband Wireless Access Systems

- IEEE 802.16e-2005 IEEE Standard for Local and metropolitan area networks Part
16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems
Amendment for Physical and Medium Access Control Layers for Combined Fixed and
Mobile Operation in Licensed Bands.

- IEEE 802.16f-2005 IEEE Standard for Local and Metropolitan Area Networks –
Part 16: Air Interface for Fixed Broadband Wireless Access Systems–Amendment
1–Management Information Base (MIB)

- IEEE 802.16g-2007 IEEE Standard for Local and Metropolitan Area Networks –
Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems –
Amendment 3: Management Plane Procedures and Services

- IEEE 802.16k-2007 IEEE Standard for Media Access Control (MAC) Bridges
Amendment 2: Bridging of IEEE 802.16

- IEEE 802.16j-2009 Air Interface for Fixed and Mobile Broadband Wireless Access
Systems – Multi-hop Relay Specification.  Approved by IEEE-SA Standards
Board on 2009-05-13 as an amendment to IEEE Standard 802.16-2009. 

- IEEE 802.16-2009 (Revision of IEEE Std 802.16-2004 is the new base standard,
developed by Maintenance Task Group under the draft title "P802.16Rev2"). 
This work resulted in the second revision of IEEE Standard 802.16, following
IEEE 802.16-2001 and IEEE Std 802.16-2004.  It consolidates IEEE Standards
802.16-2004, 802.16e-2005 and 802.16-2004/Cor1-2005, 802.16f-2005, and
802.16g-2007. 

IEEE 802.16 Standards In Progress:

- IEEE 802.16m: Advanced Air Interface development of the P802.16m project to
amend the IEEE 802.16 WirelessMAN-OFDMA specification so that, while offering
continuing support for legacy equipment, it will meet the requirements of IMT-Advanced
next generation mobile networks.

- IEEE 802.16’s License-Exempt (LE) Task Group is developing a draft under the
P802.16h PAR, which was approved by the IEEE-SA Standards Board on 2004-12-08
and extended on 2008-09-26 until the end of 2009.  The subject is "Improved
Coexistence Mechanisms for License-Exempt Operation."

Jose Puthenkulam
Vice Chair, IEEE 802.16
Wireless Standards and Technology,
Mobility Group, Intel

Presently he is leading the standardization efforts in the 802.16m project
targeting IMT-Advanced.  He was also the editor of the initial ITU-R
IMT-2000 contribution for inclusion of WiMAX in IMT-2000 family.  He has
been at Intel since 1996, and has worked on wireless communications, security,
video conferencing, information management protocols and related technologies. 
He has also been active in promoting 802.16 standards internationally for
Broadband Wireless applications.

Author’s Note:  From personal observations at IEEE 802.16
standards meetings, I can attest that Jose has been the "behind the scenes"
leader of the 802.16 standards effort.  He has been successful in building
consensus amongst industry participants, which has enabled the 802.16 standards
projects to rapidly progress and be accepted by many companies (as opposed to
ratified standards that become "paper tigers").  This collaborative process
has fostered the growth of the Mobile WiMAX ecosystem, which is evidenced in the
new WiMAX deployments and build outs that we read about every day.

Alan Weissberger 

Part II of this interview will be on Jose’s view of the emerging 4G Ecosystem.