Issues in Emerging 4G Wireless Networks

Issues in Emerging 4G Wireless Networks

Deployment of International Mobile Telephony 2000 standards for third-generation wireless networks may begin this year, with NTT DoCoMo planning to have a nationwide 3G network in Japan this year. These specifications give existing 1G and 2G operators the flexibility to evolve their networks, which support low-bit-rate data and are primarily designed for voice, into 3G systems. They also help satellite and terrestrial providers design new 3G systems. Third-generation networks offer multimedia transmission, global roaming across a cellular or other single type of wireless network, and bit rates ranging from 384 Kbps to several Mbps. Analysts expect worldwide migration to 3G to continue through 2005, depending on market needs, carrier and operator incentives, recovery on investments in existing 1G and 2G wireless systems, and perceived threats to monopolistic wireless carriers in many countries. 4G WIRELESS NETWORKS Meanwhile, researchers and vendors are expressing a growing interest in 4G wireless networks that support global roaming across multiple wireless and mobile networks-for example, from a cellular network to a satellite-based network to a high-bandwidth wireless LAN. With this feature, users will have access to different services, increased coverage, the convenience of a single device, one bill with reduced total access cost, and more reliable wireless access even with the failure or loss of one or more networks. 4G networks will also feature IP interoperability for seamless mobile Internet access and bit rates of 50 Mbps or more. Because deployment of 4G wireless technology is not expected until 2006 or even later, developers will hopefully have time to resolve issues involving multiple heterogeneous networks such as • access, • handoff, • location coordination, • resource coordination to add new users, • support for multicasting, • support for quality of service, • wireless security and authentication, • network failure and backup, and • pricing and billing. Network architectures will play a key role in implementing the features required to address these issues. POSSIBLE ARCHITECTURES One of the most challenging problems facing deployment of 4G technology is how to access several different mobile and wireless networks. Figure 1 shows three possible architectures: using a multimode device, an overlay network, or a common access protocol. Multimode devices One configuration uses a single physical terminal with multiple interfaces to access services on different wireless networks. Early examples of this architecture include the existing Advanced Mobile Phone System/Code Division Multiple Access dual-function cell phone, Iridium’s dualfunction satellite-cell phone, and the emerging Global System for Mobile telecommunications/Digital Enhanced Cordless Terminal dual-mode cordless phone. The multimode device architecture may improve call completion and expand effective coverage area. It should also provide reliable wireless coverage in case of network, link, or switch failure. The user, device, or network can initiate handoff between networks. The device itself incorporates most of the additional complexity without requiring wireless network modification or employing interworking devices. Each network can deploy a database that keeps track of user location, device capabilities, network conditions, and user preferences. The handling of quality-of-service (QoS) issues remains an open research question.

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