Wireless WANs: Cellular Radio and PCS Networks

Wireless WANs: Cellular Radio and PCS Networks

WANs can be global, national, or regional in scope. Today, they are associated with relatively low data speeds, generally only up to 19.2Kbps; in some locations, VSAT systems provide up to 2Mbps. (VSATs are discussed in Chapter 3, "Transmission Media: Characteristics and Applications.") Third-generation cellular systems are promising to someday be capable of delivering 155Mbps, but that is still quite some time in the future probably toward the end of this decade. WAN solutions include cellular radio and PCS networks (including analog and digital cellular) and wireless data networks (that is, Cellular Digital Packet Data [CDPD] and packet radio).

Although the history of cellular networks has been rather brief, it has already seen three generations:

         First generation The first generation, which initially debuted in Japan in 1979, is characterized as an analog transmission system.

         Second generation (2G) The second generation introduced digital transmission, and the first of these networks were operational in 1992.

         Third generation (3G) The third generation, which is now quickly coming upon us, will include digital transmission, but it will also permit per-user and terminal mobility, providing a single mobile communication 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, and even up to 2Mbps in some cases. 3G standards development is occurring in Europe and Asia, but universal deployment seems doubtful at present. There are still a lot of issues to resolve, especially regarding the auctioning process. For instance, in Europe, some countries paid very exorbitant rates for their licenses, and they now have to invest a similar amount in building out 3G networks, which means they face a 15- to 20-year payback period, and that is hard to justify in today's environment.

There is also an intermediate generation what we call 2.5G and that's where we currently are and where we are likely to stay for some time. 2.5G offers enhancements to the data services on existing second-generation digital platforms.

Analog Cellular Networks

Analog cellular systems are very quickly on their way out, but you will still hear the terminology related to them, so this section quickly defines some of these terms:

Cellular Versus PCS

Cellular is classified as including both analog and digital networks. Cellular networks started out as being analog, and they migrated to digital infrastructures. Cellular operates in the 800MHz to 900MHz band, depending on where you are in the world. Cellular tends to operate in macrocells, which involve a coverage area of up to 8 miles (12.8 kilometers), and because of the large coverage area, the power use is high, ranging from 0.6 watts to 3 watts.

PCS is a newer introduction than cellular, and it has been digital from the start. It operates in the 1.8GHz to 2GHz band, again depending on where you are in the world. It uses both microcell and picocell architectures, which means the coverage areas are quite small, around 1 mile (1.6 kilometers), and because the coverage area is small, much lower power is used 100 milliwatts or so.

Functionally, cellular and PCS work the same way, they perform the same functions, and they use the same types of network elements. The key differences between them are the frequency at which they operate, the coverage area over which they operate, and the power levels they use.

         Advanced Mobile Phone System (AMPS) AMPS, also known as IS-54, is on the 800MHz band, involves some 832 channels per carrier, and originated in the United States.

         Total Access Communication Systems (TACS) TACS operates in the 900MHz band, offers 1,000 channels, and originated in the United Kingdom.

         Japanese Total Access Communication Systems (JTACS) JTACS works in the 800MHz to 900MHz band, and it originated in Japan.

         Nordic Mobile Telephone System (NMT) The original variation of NMT was 450MHz, offering some 220 channels. NMT had a very large coverage area, thanks to its operation at 450MHz (you could probably travel through half of Scandinavia and still be within one cell), but the power levels are so intense that mobile sets were incredibly heavy. NMT originated in Denmark, Finland, Norway, and Sweden.

Within the cellular radio system there are three key components (see Figure 14.9): a transceiver station, a mobile telephone switching office (MTSO), and the mobile unit (that is, the phone). Each cell needs a base transceiver station the tower that is transmitting the signals to and from the mobile unit. Each of these base transceiver stations, one per cell, connects to an MTSO. The MTSO then interfaces into the terrestrial local exchanges to complete calls over the PSTN. The connections from the base transceiver stations to the MTSO can be either microwave or wireline, and then typically from the MTSO to the local exchange there is a wireline facility, but it could also potentially be microwave. (Chapter 3 discussed the various media options in detail.)

Figure 14.9. The analog cellular architecture

When a mobile unit is on, it emits two numbers consistently: the electronic identification number and the actual phone number of the handset. These are picked up by the base transceiver stations, and depending on signal level, they can determine whether you are well within the cell or transitioning out of that cell. If your power levels start to weaken and it appears that you are leaving the cell, an alert is raised that queries the surrounding base transceiver stations to see who's picking up a strong signal coming in, and as you cross the cell perimeter, you are handed over to an adjacent frequency in that incoming cell. You cannot stay on the same frequency between adjacent cells because this creates cochannel interference (that is, interference between cells).

Digital Cellular Networks

Digital cellular radio was introduced to offer a much-needed feature: increased capacity. The growing demand for mobile communications in the late 1980s was well beyond what the analog cellular infrastructure could support. Recall from earlier in the chapter that the basic cell in analog can handle about 60 subscribers; for a number of years, we have expected the number of people using wireless or mobile services to grow exponentially to an anticipated 1.5 billion people by 2004. So, we realized that we needed to be able to use the existing spectrum more efficiently, and digitalization is the first technique toward that goal. Another reason to switch to digital was to improve security. The industry was suffering from a tremendous amount of toll fraud. Creative thieves would stand on busy street corners, intercepting those electronic identification numbers and phone numbers and then cloning chips; the next month you'd have a bill for US$3,000 to an area you'd never called in your life. Digitizing that ID information meant that we could encrypt it and improve the security. Finally, the digital cellular infrastructure is very closely associated with intelligent networks, and that is what gives you the roaming capability to engage in conversations when you are outside the area of your own service provider.

So with digital cellular architectures, everything remains the same as in the analog architecture. As you can see in Figure 14.10, a base transceiver station services each cell. But because there are more cells to address the increasing capacity (remember that the first technique for spectrum reuse is to break down the coverage areas into smaller chunks), we have more base transceiver stations. Therefore, we need an intermediate device, the base station controller, to control a group of base station transceivers. The base station controllers feed into the mobile switching center, which interfaces into the group of databases that enable roaming, billing, and interconnection, as well as interfacing to a gateway mobile switching center, which passes on the relevant billing information so that the home service provider can produce invoices.

Figure 14.10. The digital cellular architecture

A number of databases are critical to the process of roaming:

         Home location register The home location register provides information about the subscribers in a particular mobile switching center-controlled area.

         Visitor location register The visitor location register stores information about the calls being made by roaming subscribers and periodically forwards information to subscribers' home service providers for billing and other purposes. Each mobile service switching center must have a visitor location register.

         Authentication center The authentication center protects the subscriber from unauthorized access, providing security features including encryption, customer identification, and so on. It is associated with the home location register.

         Equipment identity register The equipment identity register registers the mobile equipment types, and maintains a database of equipment that has been stolen or blacklisted for some reason.

Wireless Data Networks

Wireless data networking methods include CDPD and packet radio. These technologies are not generally part of new deployments today, and the extent to which these methods remain viable depends in large part on the service operators. They are covered here because you'll encounter this language.

CDPD

CDPD is a packet data protocol that is designed to work over AMPS or as a protocol for TDMA. The initial concept of CDPD was publicly introduced in 1992. CDPD was envisioned as a wide area mobile data network that could be deployed as an overlay to existing analog systems, a common standard to take advantage of unused bandwidth in the cellular air link (that is, the wireless connection between the service provider and the mobile subscriber). (Unused bandwidth is a result of silence in conversations, as well as the moments in time when the call is undergoing handover between cells. These periods of no activity can be used to carry data packets and therefore take advantage of the unused bandwidth.) That was the main objective, and large cellular network operators backed it. It is defined by the Wireless Data Forum as a connectionless, multiprotocol network service that provides peer network wireless extension to the Internet. CDPD's greatest advantage is that it was designed to operate as an extension of existing networks, namely IP networks. Any application developed for CDPD can be adapted to run on any IP-based network.

The complete network specification including architecture, airlink, network interfaces, encryption, authentication, network management, and security is defined. Throughput is nominally 19.2Kbps, but you should more routinely expect 9.6Kbps. CDPD looks like TCP/IP, which gives it some advantages, but it does require a specialized subscriber unit.

Figure 14.11 shows a CDPD network. A mobile user has a CDPD subscriber device, typically a proprietary modem provided by the network operator. It is an overlay network that goes on top of the existing analog cellular telephone network. Incorporated into the base station are some new elements, including the CDPD mobile database station and a CDPD mobile data intermediate system (that is, a router). The voice calls are switched out over the telco network, and the data traffic is sent over the CDPD router network.

Figure 14.11. CDPD network architecture

Packet Radio

Packet radio data networks are an offshoot of specialized mobile radio (SMR). They use licensed bandwidth and are built specifically for two-way data, not for voice communications. The data rates supported by packet radio range up to 19.2Kbps, but the norm is 9,600bps. The best applications for packet radio are short sessions, as in short message services (SMS), transaction processing, and perhaps e-mail; packet radio is not a solution for bulk file transfers or client/server interactions. The key applications for packet radio include dispatching, order processing, airline reservations, financial services and banking, lottery, remote database access, messaging, point-of-sale, and telemetry.

In the packet radio data network configuration shown in Figure 14.12, the end user has a mobile unit, a laptop, as well as a proprietary packet modem that provides access into the private packet base station. A private packet network is the backbone, and it may interface into public data networks or be used on a private basis, for a company's own enterprise network.

Figure 14.12. Packet radio data network architecture

Among the packet data options is Mobitex, which is a trunked radio system based on X.25, originally operated at 8Kbps, and now ranging up to 19.2Kbps. It is available worldwide on various frequencies, and it offers international roaming throughout Europe. It involves a 512-byte packet, and it is a fault-tolerant architecture.

Another packet data option is Advanced Radio Data Information Services (ARDIS), which was originally built by Motorola for IBM. Like Mobitex, ARDIS started out with a slow data rate, 4.8Kbps, and it now ranges up to 19.2Kbps. Generally, it has a coverage radius of 1 to 20 miles (1.6 to 32 kilometers). The base stations emit about 40 watts, and mobile units operate at about 4 watts. ARDIS is a hierarchical network, with 4 hubs, 36 network controllers, and more than 1,200 base stations; it is oriented toward SMS.

Cellular and PCS Standards

As mentioned earlier in this chapter, one problem in the wireless realm is that a plethora of standards have been developed and observed worldwide, and that creates interoperability problems. Developments on all the standards fronts are required to address the growing need for data communications and Internet access, as well as the building of a wireless Internet. This section describes the major standards.

GSM

One of the most popular of the digital cellular standards is GSM, which was first deployed in 1992. GSM uses TDMA and FDD, and it is independent of underlying analog systems. GSM networks and networks based on GSM derivatives have been established in more than 170 countries, and GSM involves more than 400 operators, with a user base numbering more than 500 million. In principle, GSM can be implemented in any frequency band. However, there are several bands where GSM terminals are currently available:

         GSM 900 This is the first and traditional implementation of GSM, and it operates over 880MHz to 915MHz, paired with 925MHz to 960MHz.

         GSM 1800 This band is also referred to as DCS (Digital Cellular System) 1800, and it is the PCS implementation of GSM globally. It operates over 1710MHz to 1785MHz, paired with 1805MHz to 1880MHz.

         GSM 1900 This band is also called PCS 1900 and is the North American implementation of GSM. It operates over 1850MHz to 1910MHz, paired with 1930MHz to 1990MHz.

GSM mobile stations transmit on the lower-frequency sub-band, and base stations transmit on the higher-frequency sub-band. Dual-band and triple-band phones are now becoming available, which greatly facilitates roaming between countries that use these different frequency bands.

GSM supports 124 channel pairs with a 200KHz spacing to prevent channel interference and is based on an eight time-slot technique, which means it can support eight callers per channel. Of course, voice is supported, and so is data, but with basic GSM, data rates reach only as high as 9,600bps. Among the features of GSM are international roaming with a single invoice, the capability to handle SMS, which can offset the need for paging by enabling text messages up to 160 alphanumeric characters in length to be sent to and from a GSM phone, and an external system such as e-mail, paging, and voicemail systems. It also offers message-handling services in support of the X.400 standard, which was quite important when we were using largely proprietary e-mail systems. Now with the ubiquitous addressing scheme afforded by the Internet, it's not as important, but remember that GSM evolved quite some time ago. GSM also supports Group 3 fax and, very importantly, it provisions a subscriber identity module (SIM) card, which is a smart card that defines the accounting and personal details of your service. The SIM card can be used in any GSM handset to activate service, so it can help you roam on a global basis and still be able to maintain service. You simply rent a handset tuned to the frequencies of the country you're visiting and use your SIM card to authorize the services and ensure that accounting occurs to the proper address.

GSM offers spectrum utilization that is much better than in the analog environment, the capability to improve security by applying encryption to the digital bitstreams, and authentication and fraud prevention via SIMs.

A variety of voice compression devices both half-rate coders and enhanced full-rate coders where voice quality is the preeminent concern are being developed so that we can use GSM to make more efficient use of the available spectrum. Another area of development is the capability to create closed user groups and to engage in group calls. GSM is working on offering a number of important 2.5G data services. There are currently more than 80 items being covered in the various working groups, and the following sections highlight just a few of the most important developments.

HSCSD High-Speed Circuit-Switched Data (HSCSD) makes use of the existing circuit-switched equipment, but via software upgrades. This enables you to grab several time slots, which increases the overall data rate you, as a single user, experience. HSCSD is a high-speed transmission technology that enables users to send and retrieve data over GSM networks at transmission speeds between 28.8Kbps and 43.2Kbps (but the norm is generally around 28.8Kbps) by enabling the concurrent usage of up to four traffic channels of a GSM network. The key applications for HSCSD are those in which an end-to-end circuit is important, including applications such as large file transfers, remote access, the delivery of multimedia information, mobile navigation, and mobile video.

GPRS The 2.5G technology General Packet Radio Services (GPRS) is receiving a lot of press right now, especially because it's a prerequisite for enabling the mobile Internet. GPRS makes it possible for users to make telephone calls and to transmit data at the same time. (For example, with a GPRS phone, you will be able to simultaneously make calls and receive e-mail massages.) The main benefits of GPRS are that it reserves radio resources only when there is data to send and it reduces reliance on traditional circuit-switched network elements. Also, GPRS introduces IP to GSM networks.

GPRS is an always-on nonvoice value-added service that allows information to be sent and received across a mobile telephone network. It supplements today's circuit-switched data services and SMS. It is a packet-switched solution, so it works by overlaying a packet-based air interface on the eight time slots that are used for GSM transmission. Obviously, this requires that network operators install new hardware, but when they do, they can offer their subscribers transmission speeds of up to 115Kbps.

However, achieving the theoretical maximum GPRS data transmission speed of 115Kbps would require a single user taking over all eight time slots without any error protection. It seems unlikely that service providers would allow all eight time slots to be allocated to a single user. In addition, the initial GPRS terminals are expected be severely limited, supporting only one, two, or three time slots each. Therefore, the stated theoretical maximum GPRS speeds should be compared against the reality of constraints in the networks and terminals.

Adding GPRS to a GSM network requires several additions to the network. First, two core modules the gateway GPRS service node (GGSN) and the serving GPRS service node (SGSN) must be added. The GGSN acts as a gateway between the GPRS network and public data networks, such as IP and X.25 networks. GGSNs also connect to other GPRS networks to facilitate GPRS roaming. The SGSN provides packet routing to and from the SGSN service area for all users in that service area. It sends queries to home location registers (HLRs) to obtain profile data of GPRS subscribers. SGSNs detect new GPRS mobile subscribers in a given service area, process registration of new mobile subscribers, and keep a record of their location inside a given area. Therefore, the SGSN performs mobility management functions such as mobile subscriber attach/detach and location management. The SGSN is connected to the base-station subsystem via a Frame Relay connection to the packet control units (PCUs) in the base station controller.

The GGSN acts as a gateway between the GPRS network and public data networks, such as IP and X.25 networks. GGSNs also connect to other GPRS networks to facilitate GPRS roaming. GGSNs maintain routing information that is used to properly tunnel the protocol data units (PDUs) to the SGSNs that service particular mobile subscribers. Additional functions include network and subscriber screening and address mapping. One or more GGSNs may be provided to support multiple SGSNs.

To add GPRS to a GSM network, other changes need to take place as well, including the addition of PCUs (often hosted in the base station subsystems), mobility management to locate the GPRS mobile station, a new air interface for packet traffic, new security features such as ciphering, and new GPRS-specific signaling.

The best-suited and most popular applications for GPRS are Internet e-mail, corporate e-mail, and other information services, such as qualitative services, job dispatch, remote LAN access, file transfer, Web browsing, still images, moving images, chat, home automation, document sharing/collaborative working, and audio.

GPRS is not the only service designed to be deployed on GSM-based mobile networks. The IS-136 TDMA standard, which is popular in North and South America (and which is discussed earlier in this chapter), also supports GPRS.

EDGE Enhanced Data rates for Global Evolution (EDGE) is an enhanced version of GPRS. It combines digital TDMA and GSM, and it is anticipated that we will be able to use EDGE to reach 85% of the world by using dual-mode handsets that are backward compatible with older TDMA schemes. EDGE offers anywhere from 48Kbps to 69.2Kbps per time slot on an aggregated basis, up to 384Kbps.

The GSM Association (GSMA), European Telecommunications Standards Institute (ETSI), Third Generation Partnership Project (3GPP) and UWC have agreed on EDGE as a standard. EDGE has strong endorsement because both TDMA and GSM operators can deploy it. Additionally, EDGE can be deployed in multiple spectrum bands and serve as the path to UMTS (W/CDMA) technology. TDMA operators have the option of deploying a GSM/GPRS/EDGE overlay existing in parallel to their TDMA networks at both 850MHz and 1900MHz. Eventually, we will see the convergence of TDMA and the more specialized variation of GSM. (GSM and GPRS are discussed earlier in this chapter.)

UWC

UWC, also known as ANSI-136, is the dominant technology in the Americas, with approximately 70 million worldwide users as of mid-2001, and 150 million users anticipated by 2005.

UWC uses TDMA and TDD schemes, and it offers a total of six time slots (two per user). Because it employs TDD, a time slot is required for each end of the conversation, resulting in the capability to carry three conversations per channel. UWC operates in the 800MHz frequency band, uses AMPS for signaling to reserve resources, and transfers speech in digital form; therefore, it is a digital overlay that is interoperable with the analog AMPS infrastructure. TDMA can now support a tenfold increase over AMPS capacity by using microcell and hierarchical cell engineering. In terms of data capabilities, the IS-136 standards that exist today, and those that are soon to be introduced, include the following:

         IS-136 currently allows data rates up to 30Kbps.

         IS-136+ will provide 43.2Kbps to 64Kbps.

         IS-136 HS (high-speed) will range from 384Kbps to 2Mbps. It is looking toward the same sorts of data rates that 3G promises. It uses the Eight Phase Shift Keying modulation scheme and GPRS for packet data, and it also supports EDGE.

One of the main UWC developments is UWC-136, an advancement of the IS-136 standard that uses EDGE technology. The International Telecommunication Union (ITU) has endorsed UWC-136 technology.

TIA/EIA IS-95

The TIA/EIA IS-95 standard, also known as CDMA, makes use of the spread-spectrum technologies discussed earlier in the chapter. It operates in the 800MHz and 1,900MHz frequency bands but can work on other frequency bands as well, depending on the country's standards; it's simply a matter of engineering the appropriate radio frequency on the front end. It is full-duplex (that is, it is FDD): 1.25MHz for the forward direction, and 1.25MHz for the reverse direction. cdmaOne is the CDMA Development Group's (CDG's) name for cellular carriers that use 2G CDMA technology (IS-95), and it offers a data rate range of 9.6Kbps to 14.4Kbps. The first commercial cdmaOne network was launched in 1995. Today, there are more than 71 million subscribers to CDMA networks worldwide. It is used in the United States, Asia, and Europe. In the CDMA arena, we are seeing these developments:

         IS-95A The initial data-friendly revision to the cdmaOne protocol falls under the TIA/EIA-95-A standard and is commonly called IS-95A. This revision provided for low-rate data services up to 14.4Kbps by using a CDPD overlay.

         IS-95B IS-95B adds a data capability of up to 115Kbps. This can be considered to be IS-95's 2.5G solution. This upgrade allows for code or channel aggregation to provide data rates of 64Kbps to 115Kbps. To achieve 115Kbps, up to eight CDMA traffic channels offering 14.4Kbps need to be aggregated. IS-95B also offers improvements in soft hand-offs and interfrequency hard hand-offs.

         IS-95 HDR Qualcomm's IS-95 HDR (high data rate) promises a 2.4Mbps data rate in a standard 1.25MHz CDMA voice channel (using Qualcomm technology). It includes enhanced data capabilities, and it is optimized for IP packets and Internet access.

3G Mobile Systems and Beyond

Data service is expected to rise sharply as a traffic stream on wireless networks. However, the allotted wireless spectrum and the compression techniques we know today really won't allow us to make use of the existing wireless infrastructure as if it were a wireless Internet. Visual traffic will play a very demanding role in the future of telecom networks, and the problems this traffic poses are magnified many times over with wireless media.

The future demands a new generation of infrastructure the third generation (3G), the broadband wireless realm. When you think about 3G, it's important to keep a number of things in mind. First, 3G is under development. Do not expect large-scale implementations to occur until 2003 or so; that's when 3G handsets are expected to become available in numbers that matter. Second, it is not yet certain that 3G networks will actually be implemented and installed. Although auctions have occurred and companies have acquired licenses, many have paid very large sums for those licenses and now face the prospect of having to invest just as much into the actual infrastructure because 3G requires a wholly new generation of equipment. It's not an upgrade from existing platforms, so it will require new investments to be made in the variety of network elements that will serve 3G. The bottom line is that we don't know how quickly we can expect to engage in the services and features of 3G, but we will begin to see rollouts, at least on a trial basis, between late 2001 and 2003. For wide-scale availability of broadband data rates (that is, 2Mbps), 2008 is most likely, although 3G technology can begin ramping up commercial customers by the end of 2003 if spectrum is identified by the end of 2001.

Keep in mind that while we argue the lifetime of 3G, the labs are already in development on 4G and 5G. At any point in time, new technologies are being developed and operating in labs that will emerge commercially within five to seven years. The result is that between the time of the vision and the time of the implementation, enough changes will have occurred to render the solution somewhat outdated, yet the formalization of the new and improved version is still too far off to be viable. So, let's examine the goal of 3G, and then compare 4G and 5G expectations.

3G

3G is designed for high-speed multimedia data and voice (see Figure 14.13). Its goals include high-quality audio and video and advanced global roaming, which means being able to go anywhere and be automatically handed off to whatever wireless system is available.

Figure 14.13. A vision of 3G networks

The following are some of 3G's objectives:

         Support for messaging, Internet access, and high-speed multimedia

         Improved throughput and QoS support

         Improved voice quality

         Improved battery life

         Support for fixed applications and a broad range of mobility scenarios

         Support for position-location services

         Support for all current value-added voice services

         Ease of operations and maintenance

         Coexistence with current infrastructures, including backward compatibility, ease of migration or overlay, interoperability and handoffs, the need for bandwidth on demand, improving authentication and encryption methodologies to support mobile commerce (m-commerce), and moving toward supporting higher bandwidths over greater allocations (that is, 5MHz to 20MHz)

The 3G frequencies for IMT-2000 are identified by the ITU. The bands 1,885MHz to 2,025MHz and 2,110MHz to 2,200MHz are intended for use, on a worldwide basis, by administrations that want to implement International Mobile Telecommunications 2000 (IMT-2000). Such use does not preclude the use of these bands by other services to which they are allocated. Terrestrial IMT-2000 services will operate in the FDD mode in the bands 1,920MHz to 1,980MHz paired with 2,110MHz to 2,170MHz with mobile stations transmitting in the lower sub-band and base stations transmitting in the upper sub-band. The bands 1,885MHz to 1,920MHz and 2,010MHz to 2,025MHz are unpaired for TDD operation.

3G Standards 3G is defined by the ITU under the International Mobile Telecommunications 2000 (IMT-2000) global framework. In 1992 the ITU World Radio Conference identified 230MHz, in the 2GHz band, on a worldwide basis for IMT-2000, including both satellite and terrestrial components. As a strategic priority of ITU, IMT-2000 provides a framework for worldwide wireless access by linking the diverse system of terrestrial- and/or satellite-based networks. It will exploit the potential synergy between the digital mobile telecommunications technologies and those systems for fixed wireless access (FWA)/wireless access systems (WAS).

IMT-2000 services include the following:

         Voice IMT-2000 promises to offer end-to-end store-and-forwarding of messages, which implies a data rate of 8Kbps to 64Kbps.

         Audio service Audio service, including telemetry and signaling, should be available at 8Kbps to 64Kbps or 64Kbps to 384Kbps.

         Text Text, including messaging, paging, and e-mail services, is expected to be offered at 8Kbps to 64Kbps.

         Image services Image services, which would support fax and other still images, should be provided at 8Kbps to 64Kbps.

         Video IMT-2000's video services are expected to support video telephony, video mail, teleshopping, and so on, at 64Kbps to 1,920Kbps.

The IMT-2000 terrestrial standard consists of a set of radio interfaces that enable performance optimization in a wide range of radio operating environments (see Table 14.1):

         WCDMA This interface is also referred to as the Universal Terrestrial Radio Access (UTRA) Frequency Division Duplex (FDD) UMTS. FDD operations require paired uplink and downlink spectrum segments. The radio access scheme is direct-sequence WCDMA.

         Cdma2000 This radio interface is also called CDMA MC (multicarrier), and it operates in FDD. The radio interface uses CDMA technology and is a wideband spread-spectrum system. It provides a 3G evolution for systems using the current TIA/EIA-95-B family of standards. Radio frequency channel bandwidths of 1.25MHz and 3.75MHz are supported at this time, but the specification can be extended to bandwidths up to 15MHz.

Table 14.1. IMT-2000 Radio Interfaces
Interface	Technology	Technique	ITU Designation
WCDMA (UMTS, UTRA FDD)	CDMA	Direct sequence	IMT DS
Cdma2000 (1X and 3X)	CDMA	Multicarrier	IMT MC
UTRA TDD and TD SCDMA	CDMA	Time code	IMT TC
UWC-136/EDGE	TDMA	Single carrier	IMT SC
DECT	FDMA/TDMA	Frequency time	IMT FT

         UTRA TDD This radio interface uses a direct-sequence CDMA radio access scheme. There are two versions: UTRA Time Division Duplex (TDD), which uses 5MHz bandwidth, and TD-SCDMA, which uses 1.6MHz bandwidth. TDD systems can operate within unpaired spectrum segments.

         UWC-136 This radio interface was developed with the objective of maximum commonality between TIA/EIA-136 and GSM GPRS. UWC-136 enables the TIA/EIA-136 technology to evolve to 3G capabilities. This is done by enhancing the voice and data capabilities of the 30KHz channels, adding a 200KHz carrier for high-speed data (384Kbps) for high-mobility applications, and adding a 1.6MHz carrier for very high-speed data (2Mbps) for low-mobility applications.

         DECT This radio interface uses an FDMA/TDMA scheme, and it is defined by a set of ETSI standards.

IMT-2000 satellite interfaces cover LEO, MEO, and GEO orbits as well as those specifically aimed at maximizing the commonality between terrestrial and satellite interfaces.

Universal Mobile Telephone Systems (UMTS, a WCDMA approach) is part of ETSI's Advanced Communications Technologies and Services (ACTS) program. ETSI standardization groups have been involved in defining the access method to use in sharing the new UMTS spectrum. The major objective of UMTS is personal mobility, and the vision is that any UMTS user will be able to approach any fixed or mobile UMTS terminal, register his or her presence, and then access services, such as telephony, data, and video, over this terminal. Any calls made to an international mobile user number will make use of UMTS mobility management features to find the user at the terminal of registration.

UMTS aims to remove any distinctions between mobile and fixed networking and will support the ITU's UPT concept, which means personal mobility across many different networks. Each user is issued a unique UPT number, and each UPT number has a unique user profile associated with it. By manipulating these profiles, the user can specify individual terminals for call delivery and call origination and also access advanced services such as call screening and call forwarding. UPT supports SS7 integration.

UMTS, then, defines both narrowband (that is, 2Mbps) and broadband (over 100Mbps, in the 60GHz band) types of services. Additional ETSI programs have developed Mobile Broadband System (MBS), which uses spectrum in the 40GHz to 60GHz bands, to provide data rates greater than 155Mbps. MBS aims to marry the mobile environment with intelligent networks and WCDMA, and it also promises support for multimedia, improved voice quality, improved security, interoperability, international roaming, and support for technological evolution in general. This is a combining of the mobile environment and intelligent networks. UMTS network architecture involves the development of additional intelligent networking functional entities, which will reside at nodes within the network and communicate with each other, by using sophisticated signaling protocols to deliver advanced telephony features, such as freephone and televoting, as well as some core mobility functions.

The ETSI standardization groups have been involved in defining the access methods to be used in sharing the new spectrum, and they have settled on WCDMA, which is standardized under IS-665 (OKI/Interdigital Wideband CDMA) and is the airlink technology of choice. There will be a single WCDMA standard with three modes: Direct-Sequence FDD (DS-FDD), which employs a single wideband carrier; Multicarrier FDD (MC-FDD), which involves multiple 1.25MHz carriers; and TDD for unpaired frequency bands.

The ETSI strategy is to evolve the core UMTS network from the current GSM technology. Phase 2+, or 2.5G, acts as a pre-UMTS system, and more advanced capabilities can be added in microcell or picocell environments as we evolve. The use of dual-mode or multimode handsets should enable users to move from pre-UMTS systems to the full 3G capability. UMTS support for data will probably be based on GPRS. Data speeds will range from 100Kbps, for a pre-UMTS GSM-based system, up to 2Mbps, for the new 3G radio access networks; again, the goal is to provide 155Mbps soon, sometime between 2008 and 2010.

Cdma2000 is a 3G technology for increasing data transmission rates for existing CDMA (cdmaOne) network operators, and it is a common name for ITU's IMT 2000 CDMA MC. There are several levels of Cdma2000. Cdma2000 1X is a 3G technology that offers a two-times increase in voice capacity and provides up to 307Kbps packet data on a single (1.25MHz, or 1X) carrier in new or existing spectrum. Cdma2000 1XEV is an evolution of Cdma2000 1X. 1XEV-DO (data only) uses a separate 1.25MHz carrier for data and offers peak packet data rate of 2.4Mbps. 1xEV-DV (data voice) integrates voice and data on the same carrier. Phase 2 of these standards promises the integration of voice and data at up to 4.8Mbps. Cdma2000 3X is a 3G technology that offers voice and data on a 5MHz carrier (or three times [3X] the 1.25MHz carrier).

Many standards and technologies are being considered, and there is no global agreement on what the standard for 3G should be, so, again, we are violating the promise of being able to engage in open standards on a global basis.

3G Technology Data Rates Figure 14.14 tracks where CDMA, GSM, TDMA, and mixed approaches stand in terms of the data rates they support in 2G, 2.5G, and 3G.

Figure 14.14. 3G technology evolution

Barriers to 3G A main barrier to 3G is that there is a lot of competition in this arena, with many different standards being advocated. Also, there is already an installed base, and we need to protect our investment there. Another barrier to 3G is that many nations suffer from the syndrome of "not invented here" pride. There is also some basic fear about whether there is truly market demand for the services that 3G will want to promote. Also, different nations have different priorities in terms of frequency allocations. Finally, the issues of cost and coverage are barriers to 3G.

4G and 5G Visions

Although we haven't even made it to 3G yet, at least a few parties are already advocating a vision for 4G and 5G technologies. The 4G vision is to be capable of supporting data rates of 5Mbps to 80Mbps, averaging around 20Mbps. It's a combination of Orthogonal Frequency Division Multiplexing and EDGE technologies. The features to be supported include streaming audio and video; the capability for asymmetric network access; adaptive modulation or coding schemes; dynamic packet assignment; and the use of smart adaptive antennas. It is important to consider even the generations beyond 3G, so that as you assess the future, you are considering the full range of options.

Mobile Internet

It is wise to be careful in how you interpret the use of the Internet on a wireless basis. Although in the wireline Internet we are striving for more bandwidth-intensive applications (such as voice, video, and streaming media), we need to have different expectations of the mobile Internet. We are not going to be able to Web surf visually, engaging in high-quality interactive multimedia, on a wireless basis for quite a few years. Yes, we will have the ability to access text-based information, so in the near term, the wireless Internet will be extremely usable as a messaging platform. But if you promise customers that they are going to get the mobile Internet, you may find yourself regretting having stated that, because if their experience has been a PC-based experience, their mobile Internet experience will not come close to what they're used to. On the other hand, in places such as Japan, where the PC penetrations are lower, the mobile experience is like a very first engagement with the Internet, and the users' perception will be much different.

A single device will not be suitable for all mobile Internet activities. People will use a variety of devices to connect to the Internet, depending on where they are going and for how long, and depending on what they need to do.

The main applications of mobile Internet are expected to be messaging, entertainment, wireless gaming, real-time financial data, online banking, travel information and reservations, geographical information, and location-based services. M-commerce is seen as potentially being a revolutionary new approach to using wireless. It is expected that in the next several years, more than a billion handsets, personal digital assistants, and Internet appliances equipped with wireless capabilities will be in use. The number of mobile devices connected to the Internet is expected to exceed the number of connected PCs in a very few years; couple this with the fact that the majority of the global households do not have a PC, and there is a potential m-commerce market worth double-digit billions.

WAP and i-mode

A student in France asked me if I know what WAP stands for, and then he proceeded to tell me with a smile: "wrong approach to portability." It's a good example of how lack of compelling applications and a difficult user interface can diminish the potential of a new technology. Indeed, this seems to be the case, and let's examine why. Wireless Application Protocol (WAP) is an enabling technology, a set of rules, for transforming Internet information so that it can be displayed on the necessarily small screen of a mobile telephone or other portable device. It enables a standard way of transmitting real-time content, which allows mobile phones to browse the Internet. WAP must strip down much of the information that we today enjoy on the Internet most of the images and multimedia to just the bare essential text-based information, and therein may lie some of WAP's limitations. Some of its other drawbacks are slow transmission speeds, difficulty related to inputting Web and e-mail addresses by using a 12-digit phone pad, and a scarcity of sites that use Wireless Markup Language (WML) rather than HTML as a basis.

This is how WAP gets you on the Web:

1.       A person with a WAP-enabled cell phone types the address of the Web site on the phone's screen, using a keypad, a stylus, or another interface.

2.       The microbrowser sends the request over the airwaves as a digital signal.

3.       A cell phone transmission tower picks up the signal and relays it by landline to a server operated by the wireless network.

4.       The server, which contains a software filter called a WAP gateway, is then linked to the Internet. The WAP gateway software finds the Web page requested by the cell phone user.

5.       The coding software converts the Web page from HTML to WML, which is optimized for text-only displays because it is a compact binary form for transmission over the air. This enables greater compression of data that is optimized for long latency and low bandwidth. The WAP gateway then prepares the document for wireless transmission.

6.       The WML document is transmitted to the user's cell phone. The device's microbrowser receives the signal and presents the text on the phone's small screen.

Whether WAP succeeds depends on its services and features, as well as the population for which it is targeted. To date it has been seen as a bit of a failure because it involves an entirely new language (WML), slow operating speeds, difficult user interfaces, and a capability to duplicate only parts of existing Web sites. Many believe that m-commerce will be the force to drive growth in the mobile sector, and according to some estimates, the growth of m-commerce will outstrip e-commerce within three years. These estimates are based on the success of one early entrant that has been very popular: DoCoMo's i-mode system in Japan, which currently has about 20 million users. i-mode is very much like WAP, except that it uses a proprietary protocol. People who have never owned a PC before are capable of enjoying the benefits of e-mail, and of buying things on the Internet, by using i-mode.

The key to i-mode's popularity has been Japan's love of the mobile phone. Cellular phone users in Japan number some 49 million, whereas PC users total between 3 million and 4 million. Another interesting reality of i-mode is that 50% of the users are in their twenties, 30% are in their teens, and most of the rest are in their thirties. The major revenue producer for i-mode is the capability to download the day's cartoon character. So i-mode is not trying to make today's wireline Internet applications available on a wireless basis. Instead, it is an entirely new set of services, tailored specifically for the mobile or location-based market, and it is based on the youth culture. The use of i-mode is now being considered in parts of the world other than Japan, including the United States.

Mobile Applications

The mobile Internet, like its wired sibling, is a composition of infrastructure and applications. The full-service wireless networks will support a range of mobile services, including mobile entertainment, mobile Internet, mobile commerce, and mobile location-based services. M-commerce needs to develop quickly, because it is required in order to provide effective delivery of electronic commerce into the consumer's hand, anywhere, by using wireless technology. The success of mobile entertainment, mobile location-based services, and mobile Internet depend on the ability to conduct secure financial transactions. M-commerce has the power to transform the mobile phone into a mobile wallet. Already, major companies have begun to establish partnerships with banks, ticket agencies, and top brands to take advantage of the retail outlet in the consumer's hand.

One of the main requirements for m-commerce content is ease of use. Another consideration is how personal the content is; successful content has an electronically adjustable skin, if you will, to meet the inexhaustible demand for customization. One eagerly anticipated m-commerce application is the personal finance manager, which integrates all the aspects of your finances, including bank records, work expenses, and electronic purse expenditures.

M-commerce transactions are very important because doing finances is more compelling than monitoring them. A successful system will let you pay your bills while sitting on the bus, shuffle your shares while taking a break from work, or book your plane tickets while walking down the street.

Among other mobile applications, mobile entertainment is expected to grow, with GSM WAP or GPRS-based technology being used to deliver mobile games, mobile betting, mobile music, and mobile cartoons/icons. Mobile music will offer a wide array of possibilities, including MP3 music and artist or music clips, and the downloadable ringtone musique. Mobile betting is often considered an early example of m-commerce, with large segments of the population likely to participate. Japanese networks today offer the capability to download cartoons/icons (a major revenue producer for DoCoMo's i-mode system), and will soon be seen in GSM with WAP/GPRS capability.

Geography is very important in content development, and location-based online services promise to be a very big business. The position of a handheld device is instantly identifiable because the radio signals it emits can be tracked from cellular towers and triangulated, yielding locations nearly as accurate as those of global positioning system (GPS) receivers. The triangulation calculation yields the location of the transmitting phone, and the first derivative of location yields speed, which could be used to deduce traffic jams, road construction locations, and other roadside events. Bus stations could broadcast schedules to nearby pedestrians. Trains could become online shopping malls. Automobiles could locate the nearest restaurant, give directions to the nearest filling station that sells your brand of gasoline, or locate the nearest police station, hospital, parking lot, or movie theater. Broadband compasses could allow users to access pictures and information about landmarks. So a very wide range of everyday communication services could potentially be developed.

The geography factor also means that content can be tailored to where the user is weather forecasts, restaurant locations with table availability and instant reservations, parking spaces, fast food delivery, dating services with prerecorded video profiles, and e-mail or voice mail exchanges. Any service where physical proximity is important can add value to the new devices.

Mobile consumers want convenience and they want novelty, and because a cell phone conversation provides a very important piece of information the user's location every business will need physical latitude, longitude, and elevation coordinates to sell merchandise to these moving targets. Therefore, Internet push technology may experience a revival. Once they are wired, mobile consumers offer endless new moneymaking possibilities. Unfortunately, we currently lack the business models and technology needed to realize this dream, but creative partnerships will see that the m-commerce marketplace materializes. Many such partnerships have already formed: Microsoft MSN Mobile and Ericsson, IBM and Nokia, HP and Nokia, Oracle and Telia, Sun Microsystems and NTT DoCoMo, and Yahoo! Mobile Services and Sprint. Toyota is launching My Car Universe, which is being created in partnership with Intel, Hewlett Packard, and Compaq. It would be difficult for any one supplier to carry through the entire chain, which requires customer premises equipment, transport, and content, but creative partnerships bundling several of these together will produce the revenue streams that tomorrow's infrastructures promise.

A View into the Wireless Future

What might life look like in the wireless future say, in 2008? In the next few years, companies plan to introduce handheld devices that could perform a wide variety of tasks, and this scenario involves a few people conducting their daily activities.

A university student, waiting at the bus stop, uses his digital companion to find out whether the bus is running on time. On the bus, a woman's device beeps an alert. She's been bidding for a collectible phone booth; someone has just outbid her, so she quickly sends in a higher bid.

A set of twins on the same bus are playing a networked game with an Internet friend who lives halfway around the globe.

Meanwhile, a woman riding along in a limo is using her device to check her stock portfolio because her news service just sent her a flash on merger rumors.

In a taxi nearby, a matchmaker service on a man's device beeps a proximity alert. A single woman who shares his taste in movies is close by. The man finds the woman, thanks to GPS location services, and starts a conversation. He used his digital companion to identify the closest flower shop and orders flowers for her, and as they walk by, the shop owner meets them at the door with a smile. Another wireless service helps him find a nearby Thai restaurant. Over lunch, they review the local movie reviews and schedules, then book tickets to a movie later that evening.

Meanwhile, outside the Thai restaurant, a teen walks down the street, bouncing to the beat of the latest music releases he downloaded to his wireless device earlier that morning.

After a long and leisurely lunch, the man and woman consult their digital companions, clearing their schedules so they can spend the rest of the day together.