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The wireless generation dance - 1G, 2G, 2Gt, 3G, 3Gt, 4G

The worldwide communication technology thirst and demands in bringing digital information to widespread end users have pushed innovation to extremes. Each successive generation of cellular technology has been based on a new enabling technology. By new, i mean the availability of an existing technology at low cost, or, for handset designers, the availability of a technology sufficiently power efficient to be used in a portable device.

Too often we fail to learn from lessons of the past. As an industry, we have over 20 years of experience in designing cellular handsets and deploying cellular networks. The past tells us precisely what is and what is not possible in terms of future technology deployment. This allows us to detect when reality gaps occur. Reality gaps are those between technical practicality and wishful thinking. They happen all the time and can be particularly painful when technically complex systems are being deployed. Almost all technologies start with a reality gap. The technology fails to deliver as well as expected. Some technologies never close the gap and become failed technologies. Some people can make money from failed technologies, but the majority doesn’t. Failed technologies ultimately fail because they do not deliver user value. We also tend to forget that user expectations and customer expectations change over time. A technology has to be capable of sufficient dynamic range to be able to continue to improve as the technology and user expectations mature. Failed technologies often fail because they cannot close the reality gap and cannot catch up with changing user expectations. One example of a failed technology is WiMax!

Successful technologies are that which deliver along the whole industry value chain—device vendors, handset manufacturers, network manufacturers (software and hardware vendors), network operators, and end users. I aim to show in this article how different generations of wireless technology has been evolving to become a successful proposition, both technically and commercially. I hope you enjoy reading this article and hope to get your feedback.

The cellular wireless communications industry witnessed tremendous growth in the past decade with over four billion wireless subscribers worldwide. The first generation (1G) analog cellular systems supported voice communication with limited roaming. The second generation (2G) digital systems promised higher capacity and better voice quality than did their analog counterparts. Moreover, roaming became more prevalent thanks to fewer standards and common spectrum allocations across countries particularly in Europe.

The two widely deployed second-generation (2G) cellular systems are GSM (global system for mobile communications) and CDMA (code division multiple access). As for the 1G analog systems, 2G systems were primarily designed to support voice communication. In later releases of these standards, capabilities were introduced to support data transmission.

However, the data rates were generally lower than that supported by dial-up connections. The ITU-R initiative on IMT-2000 (international mobile Telecommunications 2000) paved the way for evolution to 3G. A set of requirements such as a peak data rate of 2 Mb/s and support for vehicular mobility were published under IMT-2000 initiative. Both the GSM and CDMA camps formed their own separate 3G partnership projects (3GPP and 3GPP2, respectively) to develop IMT-2000 compliant standards based on the CDMA technology. The 3G standard in 3GPP is referred to as wideband CDMA(WCDMA) because it uses a larger 5MHz bandwidth relative to 1.25MHz bandwidth used in 3GPP2’s cdma2000 system. The 3GPP2 also developed a 5MHz version supporting three 1.25MHz subcarriers referred to as cdma2000-3x. In order to differentiate from the 5MHz cdma2000-3x standard, the 1.25MHz system is referred to as cdma2000-1x or simply 3G-1x.

The first release of the 3G standards did not fulfill its promise of high-speed data transmissions as the data rates supported in practice were much lower than that claimed in the standards. A serious effort was then made to enhance the 3G systems for efficient data support. The 3GPP2 first introduced the HRPD (high rate packet data) system that used various advanced techniques optimized for data traffic such as channel sensitive scheduling, fast link adaptation and hybrid ARQ, etc. The HRPD system required a separate 1.25MHz carrier and supported no voice service. This was the reason that HRPD was initially referred to as cdma2000-1xEVDO (evolution data only) system. The 3GPP followed a similar path and introduced HSPA (high speed packet access) enhancement to the WCDMA system. The HSPA standard reused many of the same data-optimized techniques as the HRPD system.

A difference relative to HRPD, however, is that both voice and data can be carried on the same 5MHz carrier in HSPA. The voice and data traffic are code multiplexed in the downlink. In parallel to HRPD, 3GPP2 also developed a joint voice data standard that was referred to as cdma2000-1xEVDV (evolution data voice). Like HSPA, the cdma2000-1xEVDV system supported both voice and data on the same carrier but it was never commercialized. In the later release of HRPD, VoIP (Voice over Internet Protocol) capabilities were introduced to provide both voice and data service on the same carrier. The two 3G standards namely HSPA and HRPD were finally able to fulfill the 3G promise and have been widely deployed in major cellular markets to provide wireless data access.