• cognitive radio
• multihop
• path selection
• resource allocation

The next-generation cellular wireless networks will support high data
rates and provide quality of service (QoS) for multimedia applications
with increased network capacity. Under limited frequency resources, the
conventional approach to increase network capacity is to install more
base stations (BSs) to exploit spatial reuse. This solution is not very
efficient because the cost of the BS transceiver is quite high. An alterna-
tive approach is to employ relay stations (RSs) as intermediate nodes to
establish multihop communication paths between mobile hosts and their
corresponding BSs. Multihop cellular networks (MCN) can potentially
enhance coverage, data rates, QoS performance in terms of call block-
ing probability, bit error rate, as well as QoS fairness for different users.
A number of different architectures, protocols, and analytical models
for MCNs have been proposed in the literature where different system
aspects were investigated. This thesis aims to present strategies of re-
source allocation (RA) and path selection (PS) for cognitive radio (CR)
multi-hop communications over a packet-oriented and bit-interleaved-
coded OFDM transmission, employing practical modulation and coding
schemes. As a promising technology, cognitive radio can be leveraged by
the cellular network to increase the overall spectral efciency by allowing
additional users in an already crowded spectrum. Here, we assume that
a secondary transmitter (ST) adapt his parameters for transmitting to a
secondary receiver (SR) or to a relay, over sections of spectrum owned by
licensed or primary users (PUs), without harming the quality of service
of the latter. This approach is known as underlay. The performance
of the system are evaluated in terms of goodput (GP), which is defined
as the number of information bits delivered in error free packets per unit
of time. It is able to quantify the trade-off between data rate and link
reliability, and it is a more suitable metric to quantify the actual perfor-
mance of packet-oriented systems, employing practical modulation and
coding schemes, respect to the capacity for example. A generic trans-
mitter of the network is able to optimize the GP by a proper selection
of the transmission parameters, if the channel state information (CSI)
are perfect. In most wireless networks, because of channel estimation
errors and channel feedback delay, this CSI will not be perfect there-
fore any transmitting node only has outdated and imperfect CSI and the
channel prediction and as a consequence, a predicted GP (PGP), will
be optimized. GP depends on PER that is not easy to calculate for a
multi-carrier system and so will be use kESM technique. From here a
Local-RA (L-RA) technique and a Sub-Optimal PS (Sub-PS) strategies
are formulated for non-cooperative CR multi-hop communications, ex-
ploiting xed decode-and-forward (DF) relay nodes (RNs). With these
strategies we are able to reduce the signaling over the feedback channel
and the computational complexity, compared to the Optimal-RA with
Optimal-PS method, paying a very little reduction of GP. Finally we will
evaluate whether the increase of the number of relays corresponds to a
performance increase.