WiMAX Development and 4G Evolution

The Important Role of the WiMAX Forum

What is WiMAX? It is an acronym for Worldwide Interoperability for Microwave Access, and is based on the IEEE 802.16-2005 standard. The latest version of this standard is IEEE 802.16-2009, which includes amendments on the previous IEEE 802.16-2005. IEEE standards only specify the Physical (PHY) and Media Access Control (MAC) layers. The WiMAX Forum has played an important role in ensuring all equipment and devices manufactured according to the standard are interoperable and can be deployed worldwide. It has also defined specifications for upper layers and network components for commercial deployment. The relationship between IEEE 802.16 and the WiMAX Forum Technical Working Group/Network Working Group (TWG/NWG) is shown in Figure 1.

WiMAX NWG has defined the WiMAX network reference model—which standardizes all interfaces to simplify Network Inter-Operability Test (IOT) (see Figure 2.)

The WiMAX Forum consists of multiple working groups. How the WiMAX Forum functions with various working groups is illustrated in Figure 3.

Equipment with the current version of WiMAX 1.0 is also sometimes referred to as “802.16e” equipment by people familiar with the WiMAX legacy. WiMAX has adopted scalable Orthogonal Frequency-Division Multiple Access (OFDMA) technology. In order to increase frequency efficiency and maximize network throughputs, OFDMA—along with Multiple-In Multiple-Out (MIMO) antenna technology, and Hybrid Automatic Repeat Request (HARQ) error correction scheme—has been part of a mandatory profile. Enhanced versions of OFDM and MIMO will also be adopted by ITU as an IMT-Advanced standard (also referred to the fourth generation (4G)). Therefore WiMAX and LTE, have both adopted OFDM and MIMO in their profiles, and are often branded “4G” technologies.

ZTE joined the WiMAX Forum in 2004, and has been a WiMAX Forum Board Member for over five years. As a leading global provider of end-to-end WiMAX solutions, ZTE has been playing a very active role in promoting WiMAX technology worldwide. It is also one of the most important contributors to the WiMAX ecosystem. The past five years have seen the rapid growth of WiMAX membership, from fewer than 50 members to more than 500, and the ecosystem has been shaped by silicon providers, system equipment vendors, and operators alike. The size of the WiMAX Forum Board of Directors has increased from fewer than 10 board members to more than 20, and this has steered the ecosystem in a healthy direction. More importantly, a number of stories have emerged about successful WiMAX deployments worldwide. ZTE is very fortunate to have been part of these showcases. Since the second half of 2009, ZTE’s leadership in this new market segment has been evident.

Shifting IEEE 802.16m Development into High Gear

After the IEEE 802.16-2005 standard was released, the 802.16 Working Group continued to make various amendments to it. In September 2006, members from eight companies proposed a new 802.16m Project Authorization Request (PAR), and ZTE was one of them. The development of 802.16m enables greater speed and efficiency, more advanced features, and more converged data communications while, at the same time, maintaining backward compatibility support of legacy Mobile WiMAX networks and terminals (which have been deployed all over the world). The main purpose of 802.16m is to comply with IMT-Advanced requirements and timelines, so that 802.16m—as a candidate to become a 4G standard—can be adopted by ITU in IMT-Advanced.

Since the 802.16m project began, the 802.16m Working Group has attracted more than 1200 professionals from 240 organizations in over 23 countries. The number of contributions has increased rapidly over the past three years: over 300 contributions in 2007, over 1500 in 2008, and over 2200 in 2009. The first standard of 514 pages was drafted in July 2009, and has successfully entered the Letter Ballot stage.

There are many enhancements earmarked for inclusion in 802.16m. The key areas are protocol structure, frame structure, PHY and MAC layers, Convergence Sub-layer (CS), Multi-hop Relay, multi-carrier support, Location Based Services (LBS), Enhanced Multicast Broadcast Service (EMBS), interference mitigation, and support of Femtocell and Self-Organization Network (SON) deployment.

The WiMAX Forum has endorsed IEEE’s submission to ITU-R of an IEEE 802.16m-based candidate for IMT-Advanced. The WiMAX Forum has also announced that it will finalize its WiMAX Release 2 system profile based on IEEE 802.16m, and it will do this in parallel with IMT-Advanced, ensuring that WiMAX Release 2 networks and devices  remain backwardly compatible with legacy WiMAX deployments. IEEE 802.16m will feature major enhancements in 4×4 MIMO design, VoIP capacity, spectral efficiency, latency, handover speed, cell range, and coverage, and it will support wider operating bandwidth in both TDD and FDD duplexing. IEEE 802.16m systems will provide a much faster data speed than the current Mobile WiMAX Release 1. WiMAX Release 2 equipment could be available for commercial deployment as early as 2012.

ZTE has been one of the most active and committed companies in 802.16 standard development, and has long history of contribution to various Working Groups (starting with the 802.16e project). ZTE continues to demonstrate its strong commitment, playing an important role in ongoing 802.16m standard development. As part of ZTE’s overall 4G strategies, both ZTE’s WiMAX CSN and ASN equipment should be software upgradable to comply with WiMAX Release 2 (based on 802.16m) and future IMT-Advanced specifications.

WiMAX Networks Paving the Way Towards 4G (IMT-Advanced)

The 802.16m standard will offer new capabilities and efficiencies to meet the challenges of IMT-Advanced. In the same way current 3G systems were established through ITU’s  IMT-2000 project, the ITU Radio Communication Sector (ITU-R) is in the process of establishing an agreed and globally accepted definition of 4G wireless systems using the name “IMT-Advanced.”

The IMT-Advanced project schedule shows that Radio Interface Technology (RIT) or Set of RITs (SRIT) candidate proposals were submitted and received in 2009. The technology evaluation process has begun, and is expected to be finalized by July 2010. In Release 10, 3GPP will address IMT-Advanced requirements in a version of LTE called LTE-Advanced. The LTE-Advanced specifications could become available by 2011. WiMAX will address IMT-Advanced requirements in a version called Mobile WiMAX Release 2, and its RIT system profile will be based on the IEEE 802.16m specification. The IMT-Advanced radio interface specification is scheduled to be completed in February 2011. From past experience, it can be reasonably expected that IMT-Advanced equipment will be commercially available by 2012-2014. 

This timeframe, however, seems insufficient when considering the strong and ever increasing demand for data today. According to Moore’s Law, silicon halves in size and doubles in speed every 18 months. That translates into faster and cheaper silicon. The rapid growth of data consumption, observed by many operators and forecasted by analysts, has caused traffic congestion in some networks today.

Despite the recession, the good news is that broadband markets are still growing. In fact mobile Internet has been experiencing explosive growth. During downturns, people tend to spend less on their shopping and cut down on other expenses rather than give up their mobile phones or broadband Internet access. However, the amount of network traffic has been increasing much faster than revenues can be generated. Various forms of mobile Internet access have doubled from last year, and this trend shows no sign of slowing. Social networking traffic tops the list with an annual increase of over 400%.

Smartphones, netbooks, and USB dongles are commonly used today for mobile Internet access. People read emails, access news, book airline tickets, watch video clips, and do their shopping online. Behaviors and lifestyle are changing, and instead of doing at home, we now go online with handheld devices. How to handle the explosion of data traffic is fast becoming the biggest problem facing operators. Indeed, like Pamplona crowds awaiting the bulls (see Figure 4), most gear in today’s networks is not ready for the potential growth in data traffic over the next 2-3 years.

WiMAX is a proven technology, and an early taste of 4G technology. Stories of successful WiMAX deployment come from all parts of the world. The Total Costs of Ownership (TCO) have proven much lower compared with other technologies, and WiMAX reduces the wait time for Return On Investment (ROI). The industry has observed that the time delay for ROI is reducing.

ZTE has maintained rapid growth and continued to innovate despite the global economic recession. It has been positioning for the next wave of explosive broadband growth. With ZTE’s WiMAX product portfolio, an operator can start rapid deployment of WiMAX to meet both fixed and mobile broadband demands, reliably and at very competitive cost. The TCO of the network can be greatly reduced. In the closely run race towards 4G, whichever operator can build their networks fast enough will likely win the mobile broadband markets. Like buying insurance for an uncertain future, ZTE’s CSN and ASN (including base stations) are made up of common DSP platforms that can be software upgraded to comply with WiMAX Release 2 and future IMT-Advanced specifications. Figure 5 shows ZTE’s software upgradable base stations. Each year, ZTE ships tens of thousands of base stations with the same platform for the deployment of different technologies. It doesn’t make sense to wait for IMT-Advanced—to be the market forerunner; operators can start with WiMAX now and leave decisions about technology evolution for the future.