802.20 unlocks the potential for IP-based mobile broadband access

No mobile standards to date have been specifically designed from the outset to carry native Internet Protocol (IP) traffic for fully mobile broadband wireless access. Most technologies used or proposed for mobile data communications have been adapted from standards originally optimized for other applications, such as circuit-switched mobile voice.

In March 2002, the notion of 802.20 was launched with a tutorial presented by Cisco, Flarion, HP (Compaq) and Nextel. This act formed the basis for the IEEE MBWA Study Group, whose purpose was to carry out a feasibility analysis and develop the project-authorization request that would lead to the formation of a full-fledged standards working group within IEEE. Through multilateral efforts and contributions from across the industry, including ArrayComm, Flarion, Motorola and Nextel, the study group reached a consensus and was sanctioned as the 802.20 Working Group by the IEEE Standards Association Board last December.

As with 802.11 wireless local-area networks and 802.16 broadband wireless metropolitan-area networks, the IEEE 802 model of designing a new physical (layer 1 protocol) and media-access control/link (layer 2 protocol) around the Internet Engineering Task Force's IP packet layer 3 has proven to be the right approach for unwiring the Internet.

In the same manner that 802.11 technologies enabled short-range wireless access to LANs and the 802.16 standard untethered fixed broadband wireless access, 802.20 is poised to fully mobilize the Internet Protocol, opening up major new data markets beyond the more circuit-centric 2.5 and 3G cellular standards.

As technologies evolve, incremental broadening of their applications and inevitable market overlap with other technologies occur. However, in each distinct market segment, the favored technology is generally the one specifically designed and optimized for the dominant applications in that segment. In addition, backward-compatibility and legacy issues tend to limit any evolving standard from rapidly repositioning itself for applications that substantially differ from those for which they were originally designed.

In the 1990s, the original charter of the 3G standards initiative was to unify global cellular voice standards under a common "universal" protocol. As the Internet exploded with the success of the World Wide Web, 3G technologies repositioned themselves as "all-IP" by retrofitting their circuit-based wireless access technologies between the IP core network and IP-based host devices, such as laptops.

Keeping IP moving

Their circuit-oriented protocols, however, introduced serious latency, reliability and capacity challenges for IP packet transport. As a result, 3G data adaptations have included excessive encapsulation, translations, spoofing and long control loops, along with a centralized, hierarchical network architecture that goes against the grain of the very nature of distributed IP networks.

Recently, the 802.16 Working Group also began work on a mobile extension to its existing standard, called 802.16e. Evolving from a fixed application, 802.16e is in a position to incrementally offer mobility as an enhancement to the standard's existing capability. While some form of mobility is present in each approach, each has its unique identity and characteristics with respect to mobility, latency and complexity.

Twenty years ago, when cellular technology was first introduced, the wireline voice market was at maturity. Optimizing a brand-new mobile wireless air interface around the voice circuit-switching architecture unlocked more than $100 billion in incremental voice service revenue in the United States alone. Cellular technologies succeeded, in part, because other than mobility, the application and the nature of the device did not change.

Today the computer has become as indispensable a communications device as the telephone was in 1980. To date, however, there has been no new, fully mobile air interface designed from "a clean sheet of paper" for IP. Hence, 802.20 endeavors to optimize an IP-friendly, mobile wireless air interface around today's data packet-switching architectures to mobilize the computer. Other than mobility, the user devices and applications need not change. With this, a multibillion-dollar, mobile-data opportunity stands to be unlocked.

All three technologies — 802.16, 802.20 and 3G — have enormous market potential, with each segment representing an estimated 200 million devices in the United States alone. While there is some market overlap among these segments, each has its distinct applications and device segments that these standards are optimized to address. Whether looking at the user application, service or device, each is optimal for the segment it was originally intended to serve.

To date, the 802.20 group has received numerous contributions from companies representing nearly every corner of the industry, including telecom, wireless, computing, networking and public safety/homeland security. Technical contributions range from an analysis of requirements (channel models, traffic/data message models, etc.) to potential air interfaces for both FDD and TDD applications, spanning a wide array of technologies, including OFDM spread-spectrum techniques and smart antennas. The initial technical progress and broad industry support put the 802.20 group well on the path of delivering a compelling new standard in the late 2004-early 2005 time frame and, with it, addressing the enormous market potential for IP-based mobile broadband access in a way that is complementary to both 802.16 and 3G.