Mobile Carriers

Companies such as AT&T Wireless and Sprint PCS are enlarging their networks to attain a nationwide footprint. Massive investments have been made to acquire air space for PCS service, market services and build cell sites. Cable TV companies, long distance companies and Bell companies formed joint ventures to offer PCS service. Sprint PCS was originally a joint venture of Sprint Communications and three cable companies: TCI, Comcast and Cox Communications. It was conceived as a way to jointly offer wireless and telephone service. The cable companies later divested their ownership of Sprint PCS. International and enhanced data services are focuses of all the large cellular companies in the United States.

Verizon Wireless

Verizon Wireless was formed by a merger with Vodafone AirTouch. Vodafone owns 45% of Verizon Wireless and Verizon Communications owns the rest. In 1999, Vodafone Group PLC purchased AirTouch. At the time, AirTouch was the third largest D-AMPS provider. Prior to the formation of Verizon Wireless, Bell Atlantic purchased GTE, whose wireless assets are part of Verizon Wireless. Verizon Wireless operates CDMA networks in the PCS frequencies as well as its digital and analog service in the 800 frequencies. This is a problem for customers that might want one-number service internationally because Vodafone operates GSM networks.

Cingular Wireless

The merger of SBC's CellularOne operation and BellSouth's cellular arm formed Cingular Wireless. SBC had previously purchased Ameritech, Pacific Bell and Southern New England Telephone in Connecticut cellular service. They converted Ameritech's CDMA to TDMA to make it compatible with CellularOne's TDMA structure. Bell-South has a mix of CDMA and TDMA air access. SBC owns 60% and BellSouth owns 40% of Cingular Wireless.

AT&T Wireless

AT&T Wireless got its start in cellular service with its purchase of the (at that time) largest cellular carrier in the U.S., McCaw Cellular Communications, Inc., for $12.6 billion in 1993. Interestingly, when McCaw was bought by AT&T, it had never made a profit.

AT&T Wireless has a strategy of buying existing cellular networks, forming alliances with cellular providers and building new PCS services from scratch. In 1998, it purchased independent cellular provider Vanguard Cellular. AT&T purchased PCS spectrum from FCC auctions wherever McCaw did not provide its AMPS service. AT&T service is based on TDMA. It introduced PCS services in its non-McCaw territory. It sells tri-mode telephones that adapt automatically and work on analog cellular AMPS, TDMA and 1.9 GHz PCS frequencies. It is adding GSM service to its network.

GSM Providers

The largest provider of GSM service in the United States is VoiceStream Wireless, which has purchased or owns through purchases of other companies: Omnipoint Corporation, Powertel, Inc., DiGiph PCS, East/West Communications and Aerial Communications. Deutsche Telekom purchased VoiceStream in 2001. VoiceStream has 5.4 million customers and offers service in 38 of the United States' 50 states. It will be part of Deutsche Telekom's T-Mobile subsidiary. Both companies' subscribers will have one number, one bill roaming throughout each other's areas. T-Mobile owns cellular providers One2One in the UK and max.mobil of Austria.

The desire for one-number international roaming for corporate clients is providing the impetus for AT&T Wireless and AT&T Rogers Wireless, Inc. to add GSM service to all of its cell sites. This will give AT&T Wireless a larger GSM footprint than VoiceStream. It hopes to sell cellular service to multinational customers with staff in both the United States and abroad. AT&T Wireless plans to sell general packet radio service (GPRS) data service on its GSM platform. It will keep residential customers and customers that don't purchase advanced services on its TDMA service. GPRS is an “always on” packet service with higher speeds than currently available TDMA networks. AT&T Wireless will focus on high-speed data services to corporate clients. It will heavily promote either WAP or i-mode–type Internet access plus two-way messaging service. Cingular Wireless has also announced that it is upgrading some areas to the general packet radio service (GPRS) GSM platform.

Sprint PCS

Sprint PCS has licenses for PCS spectrum in all 50 states plus Puerto Rico and the Virgin Islands. It has added numerous cell sites in 2000 and 2001. One of its advantages is its billing system, which is newer than that of many of its rivals. It markets service to business and consumer customers. It reaches residential customers through its distribution by Tandy Corporation's Radio Shack retail chain. Sprint PCS operates on code division multiple access (CDMA) technology. Sprint is investing heavily in CDMA2000 3G service that it will use as a platform for two-way messaging, email, short messaging service and other data services. (3G high-speed data services are discussed later.)

Virgin Mobile, a unit of UK-based Virgin Group, has announced that it will use the Sprint PCS network over which to sell its own brand of cellular service. Virgin Mobile will provide the sales, marketing, customer service and billing for the service. Virgin Mobile is known as a virtual operator. It supplies service but has none of its own cellular network infrastructure.

The Structure of Cellular Networks

Cellular networks are composed of the following equipment and software. See Figure 9.2. Various vendors have different labels for these devices:

• The base transceiver station (BTS) or base station subsystem (BSS)— The base transceiver station is connected to the antenna. It transmits and receives mobile calls from the cell site's antenna and amplifies (strengthens) signals. A base station consists of a BTS plus the antenna. Due to the quantities needed, base stations are the costliest part of a cellular network's hardware.

• The base station controller (BSC)— The BSC is the traffic cop of the mobile network. It does the pre-call setup (e.g., it assigns calls to radio channels in the base station transceiver, sends ringing to the correct channel and measures signal strength). The base station controller can be located at the base transceiver station or one controller can manage many base transceiver stations (BTSs).

• The mobile switching center (MSC), also called the mobile telephone switching office (MTSO)— The MSC is analogous to a PBX or central office switch. It switches calls between cellular networks and the public switched telephone network. Mobile switches have Signaling System 7^[1] (SS7) links to databases that contain billing and roaming information. (See Chapter 5 for SS7.) Mobile switches control up to 255 cell sites. New ones control up to 1024 sites.

  ^[1] Short message service, information displayed on handsets and enhanced features such as caller ID and repeat dialing, are made possible by Signaling System 7 links to databases.

• Databases— Home location registers (HLRs) contain information service and billing information on subscribers. The HLR also keeps track of the status and location of subscribers within its area. Visitor information is located in the visitor's location register (VLR). The United States has a nationwide Signaling System 7 cellular network operated by a consortium of cellular companies. It was started by AT&T.

• Connections to the public switched telephone network— Mobile telephone switching offices are connected to landline public networks by high-speed 45 megabits per second (Mbps) T-3 links.