Are LTE and mobile WiMAX really 4G networks? A look at ITU-R IMT Advanced attributes

There have been several recent articles comparing and contrasting LTE vs. mobile WiMAX as potential 4G network technologies. Indeed, SPRINT and Clearwire have been marketing their WiMAX offering as a 4G service. But is it really 4G? Is LTE a 4G technology? What about ultra-wideband?

It turns out that no broadband wireless technology can legitimately claim to be 4G, because the ITU has not completed its 4G specifications yet (4G is known as IMT Advanced in the ITU-R). Hence, there is no benchmark document(s) for which to evaluate any of the proposed 4G technologies. Several important ITU documents and presentations are listed in the References at the bottom of this article.

What are the attributes of 4G?

The ITU has stated that 4G will be a "completely new, fully IP-based integrated system of systems and network of networks- achieved after convergence of wired and wireless networks." This is in sharp contrast to current 3G networks, which are circuit-switched based, with an overlay of data carrying capabilities (EVDO for CDMA and HSDPA for GSM). 4G networks will be entirely IP packet switched. Mobile voice will be carried as a stream of IP packets–VoIP over the equivalent MAC sub-layer.

According to the ITU, 4G networks will be capable of providing 100 Mbps and 1 Gbps downstream rates, in outdoor (mobile) and indoor (fixed access) environments, respectively. 4G networks will have end-to-end QoS and high security, offer any kind of services at any time as per user requirements, anywhere with seamless interoperability, always on, affordable cost, one billing and fully personalized.

Here are the key features of 4G/IMT-Advanced (as per ITU-R document: BACKGROUND ON IMT-ADVANCED, 7 March 2008- see References below):

• a high degree of commonality of functionality worldwide while retaining the flexibility to support a wide range of services and applications in a cost efficient manner;
• compatibility of services within IMT and with fixed networks;
• capability of interworking with other radio access systems;
• high quality mobile services;
• user equipment suitable for worldwide use;
• user-friendly applications, services and equipment;
• worldwide roaming capability; and,
• enhanced peak data rates to support advanced services and applications (100 Mbit/s for high and 1 Gbit/s for low mobility were established as targets for research).
• These features enable IMT-Advanced to address evolving user needs, which implies a network that will evolve and change over time.

The 4G Radio technologies will include:

• Orthogonal Frequency-Division Multiple Access (OFDMA)- a highly efficient multi-carrier modulation scheme, and
• Multiple Input Multiple Output (MIMO)- a multi-antenna system that minimizes data errors and optimizes speed.

How do LTE and mobile WiMAX stack up against the 4G/IMT-Advanced Objectives?

Both LTE and WiMAX are based on OFDMA and MIMO technologies and both are all IP networks with QOS and (some) security. 3GPP’s initial LTE specification, due in March 2009, is that organization’s choice for a 4G network. As noted in an earlier post today, IEEE 802.16 TG m is chartered with ammending the IEEE 802.16 WirelessMAN-OFDMA specification to meet IMT-Advanced requirements, while offering continuing support for legacy WirelessMAN-OFDMA equipment. This will provide an UPGRADE path for existing mobile WiMAX networks based on IEEE 802.16-2005 to a 4G-like network.

But it remains to be seen if either of these networks will qualify as 4G/ IMT-Advanced networks when they are initially rolled out. It will take a long time to validate their attributes and operational performance against the numerous IMT Advanced requirements. Let’s not take all the hype too seriously at this time.

LTE vs. WiMAX: The 4G Wireless War

Remember when 3G was the future of wireless data? It’s not even universally available in the U.S. yet, and the race is already well underway to replace it. WiMAX, the 4G network technology that counts Sprint and Intel among its boosters, has a head start. But it’s losing ground to Long Term Evolution (LTE).

LTE’s promise of high-speed, two-way wireless data promises an “all-IP” mode of communications in which voice calls are handled via VoIP. It’s also designed to handle video well, and to permit roaming through multiple systems–from cellular to Wi-Fi and satellite.

LTE is considered by many to be the obvious successor to current-generation 3G technologies, based on WCDMA, HSDPA, HSUPA and HSPA, in part because it updates UMTS technology to provide significantly faster data rates for both uploading and downloading, while preserving backwards compatibility with existing handsets based on older standards. Verizon Wireless, has already said that it will support LTE as its 4G technology of choice, abandoning its current CDMA based network.

Speed, theoretically superior to WiMAX, would give LTE an edge for bandwidth-hungry applications such as live TV and video downloads. LTE handsets are also expected to embrace automatic roaming to non-cellular systems, such as Wi-Fi and satellite.

It’s true that WiMAX, unlike LTE, is available today–but it’s only in the early stages of rollout. (Sprint-backed Clearwire, the only company to roll out WiMAX in the U.. to date, offers service only in scattered areas in sixteen states.) Analysts express doubts that phone manufacturers, networking companies, app developers, operators, and carriers will ever make WiMAX a popular replacement for 2G or 2.75G facilities and services.

Still, WiMAX may endure–Clearwire has vowed to build a nationwide network. But the leisurely pace of its rollout indicates extra caution about the necessary investments. And Clearwire is controlled by Sprint, widely considered the weakest of the major U.S wireless carriers.

Whether they bet on LTE, WiMAX, or some combination of the two, major carriers, hardware companies, and other telecommunications players cannot postpone decisions about their 4G plans–even though it’s not yet clear how the competing technologies will sort themselves out. Investing mammoth amounts of money on building out what may be a temporary technology is high risk–especially during the worst economic crisis since the Great Depression–but they can’t leave the market open to their competitors.

The matter of superiority, WiMAX vs. LTE, is mind-boggling to industry observers, even if it might not be to a genius, or to electrical and wireless engineers. Innovation advocates might see LTE as a natural evolution of technology. Yet some technology writers have described it as unusual, in the logical sequence of technological advancement. At least, the adoption of LTE shows that the best decision, in the acceleration of wireless-connectivity technology, is not to wait for the economic recession to hit rock bottom or reverse.

The CTIA Wireless trade show in Las Vegas last month made the industry’s 4G road map a bit clearer. Most players, including Motorola and Verizon, said that they would go straight to LTE without touching WiMAX. Nokia, went further: According to a Financial Times report, Anssi Vanjoki, Nokia’s head of sales and manufacturing, compared WiMAX’s prospects to those of Betamax.

Worldwide, LTE’s prospects look promising. Some observers say that China will go directly to LTE, bypassing WiMAX. Major Chinese telecommunications players, including China Mobile and Huawei, are believed to be working hard to step up to LTE in a year or two.

My home, Pakistan, would also benefit from LTE. Currently, almost all the mobile operators, including the formerly state-owned landline monopoly Pakistan Telecommunication Company (PTCL), have flooded the consumer market with phones, cameras, music players, and USB modems that use a form of connectivity that’s similar to WiMAX but slower. These devices in Pakistan offer Internet connectivity of 300-kbs. Companies such as Wateen Telecom of the United Arab Emirates have tried to offer WiMAX, but without much success; but hardly succeeded; PTCL has tried a package of cellular connectivity, satellite TV, and broadband Internet that is also far from a success so far. China Mobile is one of the five major mobile operators in Pakistan, and other Chinese companies such as ZTE and Huawei are major players, so Pakistan’s 4G future will likely mirror that of China.

Countries such as Sweden and Finland, which are small but well-developed and technology-rich can benefit from this transitional period of wireless technologies, during which 3G, WiMAX, and LTE will coexists. Examples could be Sweden, with rich file-sharing experience, and Finland, with Nokia having early experimentation on real time interactive videos. Next in line are rapidly developing countries, including China, India, and Pakistan.

The U.S., a traditional leader in innovation and technological advancement, may struggle to adopt 4G as rapidly as other countries. Why? One reason is the difficulty of ramping up LTE during a period of recession. Another is the indecisiveness of U.S. industry heavyweights about next-generation standards. But even if the U.S.’s 4G future is somewhat murky, wireless connectivity is bound to evolve towards higher speed, great traffic capacity and more reliable connections.