8/2/2019 Why WiMAX and LTE Are 4G Technologies - ABI Research

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Why WiMAX and LTE are 4G Technologies

Released: 2010-10-26

What is 4G? ABI Research director Phil Solis has discussed this question with hundreds ofpeople throughout the mobile wireless industry over the last 5 years or so. Some in the industryagree with ABI Research that today's WiMAX (802.16e) and LTE technologies are 4G - andothers disagree. Now that the ITU has officially accepted 802.16m and LTE-Advanced as IMT-Advanced technologies, the issue has surfaced again. What make it more confusing is thatwhere the ITU mainly referred to IMT-2000 and IMT-Advanced in the past, it is now including 3Gwith IMT-2000 and 4G with IMT-Advanced. In ABI Research's opinion WiMAX and LTE are still4G technologies. Here's why.

Generations of technology (1G through 4G) are used to describe different types of air interfaces.They are grouped like this:

1G - analog, frequency division

2G - shift to digital, frequency + time division [TDMA] 3G - frequency + code division [CDMA] 4G - orthogonal frequency division [OFDMA] (and offshoots of OFDMA)

Some will argue that the criteria for meeting IMT-2000 or IMT-Advanced are arbitrary - datarate, for example. Why 100 Mbps and not 107 Mbps or 39 Mbps? 100 Mbps is just a number,one that is necessary to set a threshold for meeting a goal, but the number itself does notchange what the technology is fundamentally.

Within 2G, technologies in a family are compatible. The latest iterations of EDGE can fallback to older iterations of EDGE, back to GPRS, and even back to GSM. The pattern in 3G isthe same. The most complex version of HSPA+ can fall back to a very simple and slowerversion of HSPA+, back to HSPA, back to HSDPA, and even back to WCDMA. EV-DO Rev Bcan fall back to Rev A and back to Rev 0. (It can even fall back to CDMA 2000 1x, because itis based on CDMA.) All 2G air interfaces are based on a form of TDMA. All 3G air interfacesare based on a form of CDMA. WiMAX and LTE are not based on CDMA, but rather onOFDMA.

Of course, WiMAX and LTE do not meet IMT-Advanced specifications. WiMAX 2 (802.16m)and LTE-Advanced, however, both do meet IMT-Advanced specifications. 802.16m can fallback to 802.16e, and LTE-Advanced can fall back to LTE. So if the IMT-Advanced-compliant

versions are 4G, then today's WiMAX and LTE technologies surely must be 4G technologiesas well, because they are forward and backwards compatible. A 4G technology falling backto a 3G technology is impossible.

8/2/2019 Why WiMAX and LTE Are 4G Technologies - ABI Research

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As background, the WiMAX Forum lobbied hard to get WiMAX (802.16e) accepted as anIMT-2000 technology, but not because the WiMAX Forum thought it was also a 3Gtechnology. Rather, the reason was: spectrum. The WiMAX Forum wanted the possibility andpotential of WiMAX to have access to IMT-2000-designated spectrum. The 3GPP pushed forLTE to be accepted as an IMT-2000 technology as well.

Some will claim that dual-carrier HSPA+ with 64 QAM with MIMO can go faster than today'sinitial WiMAX technologies. Yes, they can. Speed is not the only variable; what is important isa combination of speed, latency, capacity, and cost/MB. That's where WiMAX and LTE aredifferent. Even more important is the fundamental radio technology being used.

Some also describe 1G through 4G as marketing terms. They are certainly used asmarketing terms because they are easier to grasp than IMT-2000 or IEEE 802.16e, but theyare more than just marketing terms, because engineers and product managers use 3G and4G as well, since they are shorter, easier to say, and align very well with the fundamentaltechnology behind them.

WiMAX and LTE are based on OFDMA and are something completely different from the 3Gtechnologies on the market. They have room for improvement in their current form, but astheir IMT-Advanced versions develop and come to market, today's 4G technologies will notbe left stranded because they will be compatible with the coming IMT-Advanced-compliant4G technologies.