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Thursday, August 11, 2011

4G Air Interfaces: The Idea ubiquitous coverage

In mobile communication systems, the air interface is the radio-based link between the mobile device and an active base station (BS). Designing and developing an air interface for future communication systems requires careful consideration of the envisioned scenarios for operation of these communication systems and identification of the expected challenges.
Lets not forget that Mobile and wireless communication is an important driver of economic growth. Significantly improved transmission capabilities are increasingly required to support content-rich, data oriented services in order to connect people as well as machines to the information society. Mobile and wireless systems beyond third generation (3G) emerged as the means to realize the concept of ‘‘optimally connected anywhere, anyhow, and anytime’’ supported by all system levels, from access methods and networks to service platforms and architectures. These systems were modeled as a horizontal communication model in which different terrestrial access levels and technologies are combined to complement each other in an optimum way for different service requirements and radio environments.

Broadband air interfaces are needed to provide for high-bit-rate wireless communications. To achieve this goal, consolidated research is required among areas such as communication theory, information theory, signal processing, propagation, antennas, and real-time hardware.

The rising demand for fast, scalable, efficient, and robust data transfer over the air has produced a variety of RATs (Radio Access Technologies). Future 4G (and Beyond 4G) wireless systems are supposed to provide high-bit-rate services in IP-based, real-time, person-to-person as well as machine-to-machine multimedia communications. These systems will include a number of coexisting subnetworks with different RATs. The interworking between radio subnetworks and, especially, the tight cooperation between them is very interesting in operating RATs for system capacity optimization. The reconfiguration technology provides adaptation of the radio interface to varying RATs, provision of possible applications and services, updating of software, and enabling full exploitation of the flexible resources and services of heterogeneous networks. Reconfigurable terminals, with embedded radio link layer functionalities according to network architecture, will allow for cooperation among multiple RATs.
Generally the deployment scenarios for any Next generation system ( Such as 4G) is as shown in the table here;
A successful system deployment should enable economic solutions with respect to spectrum need, deployment, and equipment costs. Higher data rates and possibly higher carrier frequencies reduce the covered range significantly compared to existing systems. Ubiquitous coverage, therefore, requires a higher number of BSs and access points, which would increase the deployment costs.

For this reason, 4G radio systems must ensure sufficient range and scalability with respect to system capacity and deployment costs. New frequency bands might also be required to provide for new high-data-rate services. Optimum spectrum use is one of the research challenges related to radio interface system design and optimization. The illustration shown here shows an ubiquitous radio system concept.
One key to ubiquitous deployment is the ability to operate in multiple scenarios. The system shown in the illustration here is able to provide coverage in wide- as well as short-range areas. Relays offer benefits in terms of coverage extension, and technologies such as cooperative relaying are being considered in the context of 4G networks. Relaying requires specific channel models, relay to relay and mobile to relay.

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