Wireless WANs

It is abundantly clear that wireless networks are a very important part of our future, promising to dramatically change the way society and industry function. Wireless networks fall into the same domains as wireline networkswide area networks (WANs), metropolitan area networks (MANs), local area networks (LANs), and personal area networks (PANs)and are applied in support of a growing number of applications, including mobile (such as cellular and PCS systems), fixed (as in wireless local loop), broadcast (television), and sensor-based (such as RFID) networks.

This chapter explores wireless wide area network (WWAN) standards and systems. WANs can be global, national, or regional in scope. Traditional WWAN solutions include cellular radio and PCS networks (including analog and digital cellular) as well as early wireless data networks (i.e., Cellular Digital Packet Data [CDPD] and packet radio). Newer generations are focused on supporting high-speed data as well as video and multimedia, with increased emphasis on mobile content delivery.

Given the basic human desire and need for freedom of movement, it is little surprise that the demand for wireless network solutions is enormous. With the introduction of cellular communications, we saw an increasing demand for wireless services. The growth was so rapid that by 2002, we witnessed a major shift in network usage: For the first time in the history of telecommunications, the number of mobile subscribers exceeded the number of fixed lines. And that trend continues. According to the ITU, at year-end 2004, the total number of mobile subscribers was 1.75 billion, while the total number of fixed lines worldwide was 1.2 billion. By September 2005, the number of mobile subscriber connections exceeded 2 billion. Although the history of cellular networks has been rather brief, it has already seen three generations, the fourth is emerging, and a fifth generation is on the drawing boards:

• First generation (1G) The first generation, which initially debuted in Japan in 1979, is characterized by analog transmission systems. Key 1G standards included AMPS, TACS, JTACS, and NMT.
• Second generation (2G) The second generation introduced digital transmission, and the first 2G networks were operational in 1992. GSM, UWC-136, cdmaOne, and PDC are the four major 2G cellular standards, along with the Personal Communications Services (PCS) standards GSM 1800, GSM 1900, and PDH. 2G networks are currently serving the vast majority of mobile subscribers.
• Intermediate second generation (2.5G) An intermediate second generation called 2.5G offers enhancements to the data services on existing 2G digital platforms, achieving many of the same speeds offered by 3G networks but without requiring the operator to acquire new spectrum and put in an entirely new infrastructure. The key 2.5G standards include GPRS, HSCSD, and EDGE.
• Third generation (3G) The third generation, which is now upon us, involves digital transmission but also permits per-user and terminal mobility, providing a single mobile communications service, adjusted for broadband applications (including voice, data, and multimedia streams) to be supported at higher data speeds, in the range of 144Kbps to 384Kbps, up to 2Mbps in some cases, and with visions of supporting 155Mbps. The major 3G standards include W-CDMA, UMTS, CMDA2000, CDMA450, TD-SCDMA, and FOMA. 3G standards deployment is occurring around the world, but universal deployment is still far from complete. The key advances in emerging technologies that greatly improve spectrum utilization and performance threaten 3G.

  An intermediate third generation, 3.5G, is introducing many enhancements designed for services running over an IP backbone, including high-speed data and video. Key 3.5G standards include HSDPA, HSUPA, and HSOPA.

• Beyond 3G Also known as Long-Term Evolution (LTE), Super 3G, and Ultra 3G, Beyond 3G is an enhancement to 3G that involves today's 3G technologies but supports bandwidths greater than 5MHz and adds smarter and more efficient IP-based back-end infrastructure and additional one-way or two-way airlinks to provide further capabilities.
• Fourth generation (4G) The fourth generation, which is under development, will bring with it new technologies that allow even better use of capacity and better performance. The introduction of 3G technology provides a huge expansion in mobile capacity and bandwidth, and 4G will do the same for broadband communications. 4G will support a wide range of data rates, promising a maximum of 50Mbps to 100Mbps while moving and an average of 20Mbps and up to 1Gbps while standing still. The two key technologies involved with 4G are OFDM and MIMO.
• Fifth generation (5G) Beyond 2010, a new generation of network will emerge, rendering 3G and 4G obsolete. By the time 5G comes along, researchers predict a revolution that will enable fast downloads of large chunks of data across the Internet. The user could access a 5G network to download a movie or videogame and then store the data in a handset. More importantly, 5G will support the sorts of advanced multimedia applications discussed in the book's introduction, such as teleimmersion, virtual reality, and telerobotics.