Wireless Network Evolution

The first generation of wireless mobile communications was based on analog signaling. Analog systems, implemented in North America, were known as Analog Mobile Phone Systems (AMPS), while systems implemented in Europe and the rest of the world were typically identified as a variation of Total Access Communication Systems (TACS). Analog systems were primarily based on circuit-switched technology and designed for voice, not data.

The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). GSM systems, first implemented in 1991, are now operating in over 125 countries and territories around the world. GSM technology is a combination of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band. FDMA is used to divide the available 25MHz of bandwidth into 124 carrier frequencies of 200kHz each. Each frequency is then divided using a TDMA scheme into eight timeslots. The use of separate timeslots for transmission and reception simplifies the electronics in the mobile units. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas, where they operate in the 1.9 GHz band.

In addition to GSM, a similar technology, called Personal Digital Communications (PDC), which uses TDMA-based technology, emerged in Japan. Since then, several other TDMA-based systems have been deployed worldwide. While GSM technology was developed in Europe, Code Division Multiple Access (CDMA) technology was developed in North America. CDMA uses spread spectrum technology to break up speech into small, digitized segments and encodes them to identify each call. CDMA systems have been implemented worldwide.

While GSM and other TDMA-based systems have become the dominant 2G wireless technologies, CDMA technology is recognized as providing clearer voice quality with less background noise, fewer dropped calls, enhanced security, greater reliability and greater network capacity. The 2G wireless networks mentioned above are also mostly based on circuit-switched technology. 2G wireless networks are digital and expand the range of applications to more advanced voice services, such as Called Line Identification. 2G wireless technology can handle some data capabilities such as fax and short message services at a data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.

Evolution to 2.5G

Because 2G data rates are too slow for today's Internet, GSM, PDC and other TDMA-based mobile system providers and carriers have developed a 2.5G technology that is packet-based and increases the data communication speeds to as high as 384kbps. These 2.5G systems are based on High Speed Circuit-Switched Data (HSCSD), General Packet Radio Service (GPRS), and Enhanced Data Rates for Global Evolution (EDGE) technologies.

HSCSD is one step toward 3G wideband mobile data networks. This circuit-switched technology improves data rates up to 57.6kbps by introducing 14.4 kbps data coding and by aggregating four radio channels timeslots of 14.4 kbps. GPRS is an intermediate step that is designed to allow the GSM world to implement a full range of Internet services without waiting for the deployment of full-scale 3G wireless systems. GPRS technology is packet-based and designed to work in parallel with the 2G GSM, PDC, and TDMA systems that are used for voice communications and for table look-up to obtain GPRS user profiles in the Location Register databases. GPRS uses a multiple of the 1 to 8 radio channel timeslots in the 200kHz-frequency band allocated for a carrier frequency to enable data speeds of up to 115kbps. The data is packetized and transported over Public Land Mobile Networks (PLMN) using an IP backbone so that mobile users can access services on the Internet, such as SMTP/POP-based e-mail, FTP, and HTTP-based Web services.

EDGE technology is a standard that has been specified to enhance the throughput per timeslot for both HSCSD and GPRS. The enhancement of HSCSD is called ECSD, whereas the enhancement of GPRS is called EGPRS. In ECSD, the maximum data rate will not increase from 64 kbps due to the restrictions in the A interface, but the data rate per timeslot will triple. Similarly, in EGPRS the data rate per timeslot will triple and the peak throughput, including all eight timeslots in the radio interface, will exceed 384 kbps.

Jump Forward to 3G

Third generation wireless technology represents the convergence of various 2G wireless telecommunications systems into a single global system that includes both terrestrial and satellite components. One of the most important aspects of 3G wireless technology is its ability to unify existing cellular standards, such as CDMA, GSM, and TDMA, under one umbrella, which is achieved through three radio interfaces: wideband CDMA, CDMA2000, and the Universal Wireless Communication (UWC-136) interfaces.

Wideband CDMA (WCDMA) is compatible with the current 2G GSM networks prevalent in Europe and parts of Asia. WCDMA requires bandwidth of between 5MHz and 10 MHz, making it a suitable platform for higher capacity applications. It can be overlaid onto existing GSM, TDMA (IS-36) and IS95 networks. Subscribers are likely to access 3G wireless services initially via dual band terminal devices. WCDMA networks will likely be used for high-capacity applications and 2G digital wireless systems will be used for voice calls. CDMA2000 is backward compatible with the second generation CDMA IS-95 standard predominantly used in US. Universal Wireless Communications UWC-136, also called IS-136HS, was proposed by the Telecom Industry Association and is designed to comply with ANSI-136, the North American TDMA standard.

Initially, 3G wireless networks are likely to be deployed as "islands" in business areas where more capacity and advanced services are demanded. However, the implementation of 3G wireless systems raises several critical issues, such as the successful backward compatibility to air interfaces, as well as to deployed infrastructures.

The existence of legacy networks in most regions of the world highlights the challenge that communications equipment manufacturers face when implementing next-generation wireless technology. Compatibility and interoperability between new 3G wireless systems and old legacy networks must be achieved in order to ensure the acceptance of new 3G wireless technology by service providers and end-users.

Existing core technology used in mobile networks is based on traditional circuit-switched technology for delivery of voice services. However, this traditional technology is inefficient for the delivery of multimedia services. The core switches for the next-generation of mobile networks will be based on packet-switched technology, which is better suited for data and multimedia services.

About Continuous Computing

Continuous Computing provides integrated systems and services that enable telecom equipment manufacturers to rapidly deploy Next Generation Networks (NGN). Over 150 customers worldwide benefit from the company's unique blend of customized professional services, Trillium protocol software, AdvancedTCA and CompactPCI systems, and BladeCenter hardware. Continuous Computing helps customers reduce platform lifecycle costs, optimize data delivery, and accelerate deployments of NGN, 3G/4G Wireless, and IP Multimedia Subsystem (IMS) infrastructure. The company is ISO-9001 and CMMI certified and based in San Diego with development centers in China and India. For more information, visit www.ccpu.com.

Continuous Computing, the Continuous Computing logo, Create | Deploy | Converge, FlexTCA, Flex21, FlexChassis, FlexCompute, FlexCore, FlexDSP, FlexPacket, FlexStore, FlexSwitch, FlexTCA, Network Service-Ready Platform, Quick!Start, TAPA, Trillium, Trillium+plus, and the Trillium logo are trademarks or registered trademarks of Continuous Computing Corporation. Other names and brands may be claimed as the property of others.