Multimode Communication Protocols Enabling Reconfigurable Radios
EURASIP Journal on Wireless Communications and Networking
Multimode Communication Protocols Enabling Reconfigurable Radios
Lars Berlemann 0
0 Chair of Communication Networks, RWTH Aachen University , Kopernikusstraße 16, D-52074 Aachen , Germany
This paper focuses on the realization and application of a generic protocol stack for reconfigurable wireless communication systems. This focus extends the field of software-defined radios which usually concentrates on the physical layer. The generic protocol stack comprises common protocol functionality and behavior which are extended through specific parts of the targeted radio access technology. This paper considers parameterizable modules of basic protocol functions residing in the data link layer of the ISO/OSI model. System-specific functionality of the protocol software is realized through adequate parameterization and composition of the generic modules. The generic protocol stack allows an efficient realization of reconfigurable protocol software and enables a completely reconfigurable wireless communication system. It is a first step from side-by-side realized, preinstalled modes in a terminal towards a dynamic reconfigurable anymode terminal. The presented modules of the generic protocol stack can also be regarded as a toolbox for the accelerated and cost-efficient development of future communication protocols.
and phrases; generic protocol stack; link layer functions; modular layer composition; reconfigurability; softwaredefined radio
1. INTRODUCTION
The radio access of future ubiquitous communication
networks will be released from the constrains of cellular wireless
networks, as for instance universal mobile telecommunication
system (UMTS), or wireless local area networks (WLANs).
Wireless mobile broadband systems, providing a patchy
coverage in densely populated urban areas, will play an
important role. For details on such a fixed and planned
relaybased radio network, see [
1, 2
]. The addressed future wireless
network will have to combine several radio access
technologies (RATs). Consequently, multimode capable terminals and
base stations are required to enable the seamless
interworking between these RATs. Multimode architectures can already
be found in existing systems, like IEEE 802.16 [3] with
different modes of the physical layer (PHY).
Software-defined radios (SDRs) [
4, 5
] are a promising
approach towards these multimode devices. The recent
technological progress allows an extension of the key issues in
research of SDRs from the signal processing of the physical
layer on the complete communication chain used for
wireless communication. The current research efforts are
targeting at the realization of cognitive radios [
4, 6, 7
]: self-aware,
frequency-agile radio systems that are able to identify
unused radio spectrum. These cognitive radios require
protocol reconfigurability to unfold their advantage of dynamic
spectrum usage. Therefore, this paper extends the focus of
SDRs on the protocol software used for reliable
communication over the air. Especially, the data link layer (DLL)
and network layer corresponding to the ISO/OSI reference
model [8] are considered. This work supplements the
research of the integrated project E2R [
9
] dealing with
end-toend reconfigurability. The approach taken in this work aims
at maximizing flexibility by providing a framework that is
both general enough to accommodate a wide range of
protocols, yet efficient enough to ensure competitive performance.
(Classic) single
protocol stack
Data
structures
Protocol
functions
Protocol
architecture
Protocol
management
Protocol
framework
Similar goals have been formulated and followed in the
software engineering domain. The x-Kernel [
10
] architecture
composes a protocol graph of protocol components together
into a system, but the approach does not permit dynamic
reconfiguration of the protocol graph and does not specifically
target wireless communications. The DARPA active
networking program [
11
] tries to answer the key question of
location (and nature) of programmability with the perspective
to build a flexible distributed computing system, again with
a focus on fixed networks.
This paper consolidates previous publications [
12, 13
]
and deduces summarizing conclusions. After introducing the
idea of a generic protocol stack in Section 2, its application
for protocol reconfigurability in the context of a multimode
capable protocol architecture is outlined thereafter. The
realization of a generic protocol stack, based on fundamental
protocol functions that can be parameterized, is summarized
in Section 3. The composition of specific protocol layers of
adequately parameterized modules is shown in Section 4.
Section 5 introduces the composition of system-specific
layers at the example of the UMTS radio link control (RLC) layer,
the transmission control protocol (TCP), and the IEEE 802.11
medium access control (MAC) layer, which differ in their
develo (...truncated)