Multimode and Reconfigurable Platforms

 
Multimode and Reconfigurable Platforms
A major contributor toward the convergence of platforms in the B3G era is reconfigurability, which
provides technologies (SDRs) that enable terminals and network segments to dynamically adapt to
the set of radio access technologies (RATs) that are most appropriate for the conditions encountered
in specific service area regions and at specific times of the day. RAT selection is not restricted to
those preinstalled in the elements. On the contrary, the missing components can be dynamically
downloaded, installed, and validated. Reconfigurability poses requirements on the functionality of
wireless networks. Some of the challenges that have to be met to realize the reconfigurability concept
are given below.
First, three families of scenarios that must be taken into account when designing the reconfigurability
technology have been identified: the promises of ubiquitous access, pervasive services, and
dynamic resources provisioning. Ubiquitous access is mainly targeted at increasing the worldwide
access to services. It relates to the support of users who turn on a device in a wireless environment to which it has not been previously connected. Roaming is another example of this scenario, and
the reconfigurability concept must increase roaming possibilities for users. The concept of pervasive
services stresses the need for reconfigurability when several radio access technologies are present
in a given wireless environment. Indeed, the proper use of these different access technologies and
reconfigurable equipment needs many capabilities like system discovery, protocol reconfiguration,
and a method of vertical handover. Dynamic resources provisioning involves a dynamic reconfiguration
of the terminal and network elements to improve the bandwidth for users with better adapted
radio interfaces as well as additional spectrum. In this case, the protocol stack must be updated in
the terminal and in the network. Consequently, the different communication systems covering such
areas must be able to adapt to load and services variations.
Second, reconfigurability research has identified the concept of a Management and Control System
that enables network elements to operate in an end-to-end reconfigurability context. The main idea
of this concept is a clear separation of network management and control functions. Reconfigurable
components, like programmable processors and reconfigurable logic, are envisioned for reconfigurable
equipment. B3G architecture needs to support the dynamic insertion and configuration of different
protocol modules as devices join and leave the given wireless environment. Furthermore, the reconfigurability
of SDR equipment is widely seen as one of the enabling technologies for communication
systems beyond 3G.
Third, the full benefits of SDR show up only if the network infrastructure takes into account
the specifics of a particular terminal and provides support for it. Network support for reconfigurable
entities requires the definition of appropriate functions in existing network elements or separate reconfiguration
entities (for example, reconfiguration proxies). The definition of reconfiguration signaling
between reconfiguration functions and reconfigurable entities is another key point. On the basis of
the network architectures derived, and the reconfiguration signaling between entities for installation,
deinstalling and verification must also be researched. Intelligent and self-learning protocols dependent
on the reconfiguration context will have to be evaluated. Reconfiguration security for secure download,
installation, verification, and fault management must be addressed to ensure a reliable operation
and to satisfy regulatory demands for radio software. A framework for secure access to reconfiguration
functionality by operators, manufacturers, and third parties must be developed. Furthermore, the
active network environment for the management of reconfiguration needs to be studied.
Lastly, efficient spectrum management (initially discussed in Section 6.1) is of prime importance
for reconfigurability to be realized. In discussions on reconfigurability, efficient spectrum management
is one of the components of radio resource management (RRM), which also includes a joint
management of radio resources belonging to different (2G and 3G) RATs with fixed spectrum allocation,
cognitive radio, and a progressive network planning process. RRM is a complex process, but is
necessary for the deployment of B3G networks. It consists of dynamically managing a spectrum as
well as allocating traffic dynamically to the RATs participating in a heterogeneous, wireless access
infrastructure. The coexistence of diverse technologies that form part of a heterogeneous infrastructure
has brought about the idea of flexibly managing the spectrum. This implies that fixed frequency
bands are no more guaranteed for RATs, but through an intelligent management mechanism, bands
are allocated to RATs dynamically in a way that ensures that the capacity of each RAT is maximized
and interference is minimized. Furthermore, there is a tight relationship between spectrum management
and cognitive radio. Cognitive radio will provide the technical means for determining in real
time the best band and the best frequency to provide the services desired by a user. Additionally,
the growing demand for high-speed access to all kinds of telecommunication systems has made the
reconsideration of traditional network planning methods necessary. Taking into account the fact that
the advent of composite reconfigurable networks has become an inseparable part of almost every
communications conference and journal, dynamic network planning (DNP) is essential in order to
handle the alternations that take place in frequent time periods, with respect to the demand pattern
in a specific geographical area. So, the goal of DNP is to reduce the cost of network deployment by the selection of the appropriate RATs for operation at different times and in different regions [541].
More research needs to be done on RRM to make reconfigurability a reality in B3G systems.
Summarizing, reconfigurability requires enhanced functionality for both terminals and networks.
Researchers are developing a system for the management and control of terminal and network equipment.
Special attention is required for the interface between (the separated) network management
and control functions. One preliminary concept would allow (re)configuration of all affected layers
through a unified, generic interface. A more detailed specification of these services and functions is
needed [542].