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Position location strategies, applications (Part 1)

Posted: 02 Nov 2011     Print Version  Bookmark and Share

Keywords:CDMA  TDMA  Position location  Cellular network 

4G systems' aim is to provide high network capacity and broadband connectivity so that handsets are able to receive high-definition video; universal coverage so that the anywhere-anytime and any-technology paradigm can be fulfilled; and the ability to form personal networks at low cost.

The integration of service platforms and technologies challenges network operators to provide a seamless mobility among platforms and technologies. Technologically speaking, 4G systems are expected to rely on turbo coding and space–time coding techniques, a modulation based on QAM with OFDM (i.e., multi-carrier QAM), and multiple access still to be defined that integrates information and coordination of interference.

The future 4G networks will incorporate 2G and 3G systems and a wide variety of networks with heterogeneous devices that will be characterized by smart communications techniques. Integration is expected to include WCDMA, GSM, cdma2000, wireless local area networks (WLANs), satellite networks, digital video broadcasting (DVB), digital audio broadcasting (DAB), and newly emerging networks. So instead of having a single network do everything, a variety of networks with different kinds of access will provide all types of services. These networks will have to cooperate so that access to services and applications is transparent to the user.

The smart devices will be able to download configuration files from a service provider to adapt to requirements for accessing a given application. This procedure will make such devices reconfigurable. The 4G network will likely be organised in layers (not hierarchical ones necessarily) where devices can communicate among themselves (e.g., using Bluetooth or WLAN technologies in a peer-to-peer fashion). Also, access points (APs) will comprise a layer providing services such as Internet access. Cellular 2G and 3G networks will work as transport networks providing wireless access to all WLAN APs in order to reach final destinations or universal connectivity, (e.g., to a satellite network). Figure 7 shows an example of this layering network for 4G systems.

Figure 7: 4G concept of integrating technologies.

One of the characteristics of this layered architecture is heterogeneous networks working collaboratively; to provide mobility, there should be consideration not only of internal handoffs, such as those occurring between adjacent cells of a network, but also of handoffs between different technologies. The latter have been called vertical handoffs due to the layered structure of the 4G paradigm. In the upcoming sections, some discussion on this will be presented, but one must keep in mind that in order to perform such vertical handoffs, mobile handsets must be equipped with hardware that is capable of adapting to various radio interfaces. Energy consumption is affected by this feature since transmission power varies by technology. Thus, there is a trade-off between the use of different resources and the need to implement such adaptability.

Development of 4G architectures is concentrated on the flexibility at all levels of the architecture in order to improve performance not only in applications and services, but also in air interface and network control and signalling.

Printed with permission from Academic Press, a division of Elsevier. Copyright 2009. "Position Location Techniques and Applications" by David Munoz, Frantz Bouchereau Lara, Cesar Vargas & Rogerio Enriquez-Caldera.

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