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Technology Update /

CDMA2000 1xEV-DO delivers 3G wireless

By Vedat Eyuboglu
Network World, 02/25/02

CDMA2000 1xEV-DO technology offers near-broadband packet data speeds for wireless access to the Internet.

CDMA stands for Code Division Multiple Access, and 1xEV-DO refers to 1x Evolution-Data Optimized. CDMA2000 1xEV-DO is an alternative to Wideband CDMA (WCDMA). Both are considered 3G technologies.

A well-engineered 1xEV-DO network delivers average download data rates between 600K and 1,200K bit/sec during off-peak hours, and between 150K and 300K bit/sec during peak hours. Instantaneous data rates are as high as 2.4M bit/sec. These data rates are achieved using only 1.25 MHz of spectrum, one-quarter of what is required for WCDMA.

In an IP-based 1xEV-DO network, radio nodes perform radio frequency processing, baseband modulation/demodulation and packet scheduling.

Radio nodes installed at a cell site can support hundreds of subscribers. Radio network controllers (RNC) typically are located in a central office and provide hand-off assistance, mobility management and terminal-level security via a Remote Authentication Dial-In User Service server. Each RNC can support many radio nodes and connects to a service provider's core data network through a standard wireless router called a packet data serving node. Finally, an element management system lets service providers manage 1xEV-DO radio networks.

1xEV-DO takes advantage of recent advances in mobile wireless communications, such as the adaptive modulation system, which lets radio nodes optimize their transmission rates based on instantaneous channel feedback received from terminals. This, coupled with advanced turbo coding, multilevel modulation and macrodiversity via sector selection, lets 1xEV-DO achieve download speeds that are near the theoretical limits of the mobile wireless channel.

1xEV-DO also uses a new concept called multiuser diversity. This allows more efficient sharing of available resources among multiple, simultaneously active data users. Multiuser diversity combines packet scheduling with adaptive channel feedback to optimize total user throughput.

A 1xEV-DO network is distinguished from other 3G networks in that it is completely decoupled from the legacy circuit-switched wireless voice network. This has let some vendors build their 1xEV-DO networks based entirely on IP technologies. Using IP transport between radio nodes and RNCs lowers backhaul costs by giving operators a choice of backhaul services, including frame relay, router networks, metropolitan Ethernet and wireless backhaul. IP-based 1xEV-DO networks take advantage of off-the-shelf IP equipment such as routers and servers, and use open standards for network management.

1xEV-DO networks have the flexibility to support both user- and application-level quality of service (QoS). User-level QoS lets providers offer premium services. Application-level QoS lets operators allocate precious network resources in accordance with applications' needs. Combined with Differentiated Services-based QoS mechanisms, flexible 1xEV-DO packet schedulers can enable QoS within an entire wireless network.

The International Telecommunication Union and Third Generation Partnership Project 2 recognize 1xEV-DO as an international standard. Subscriber devices based on the standard will become available in the second half of this year in North America. These devices will come in various forms, including handsets, PC cards, PDA sleds and laptop modules.

Multimode 1xEV-DO terminals that support CDMA2000 1x voice will let subscribers receive incoming voice calls even while actively downloading data using 1xEV-DO. While 1xEV-DO is capable of supporting high-speed Internet access at pedestrian or vehicle speeds, it is can also be used from homes, hotels and airports.