315 research outputs found
Performance Analysis of Multihop Wireless Links over Generalized-K Fading Channels
The performance of multihop links is studied in this contribution by both analysis and simulations, when communicating over Generalized- () fading channels. The performance metrics considered include symbol error rate (SER), outage probability, level crossing rate (LCR) and average outage duration (AOD). First, the expressions for both the SER and outage probability are derived by approximating the probability density function (PDF) of the end-to-end signal-to-noise ratio (SNR) using an equivalent end-to-end PDF. We show that this equivalent end-to-end PDF is accurate for analyzing the outage probability. Then, the second-order statistics of LCR and AOD of multihop links are analyzed. Finally, the performance of multihop links is investigated either by simulations or by evaluation of the expressions derived. Our performance results show that the analytical expressions obtained can be well justified by the simulation results. The studies show that the channel model as well as the expressions derived in this paper are highly efficient for predicting the performance metrics and statistics for design of multihop communication links
Performance analysis of cooperative relay networks in presence of interference
In the past decade, cooperative communication has emerged as an attractive
technique for overcoming the shortcomings of point-to-point wireless communications
systems. Cooperative relaying improves the performance of wireless networks
by forming an array of multiple independent virtual sources transmitting
the same information as the source node. In addition, when relays are deployed
near the edge of the network, they can provide additional coverage in network
dead spots. Interference in the network can also be reduced in cooperative communications
systems as the nodes can transmit at lower power levels compared
to equivalent point-to-point communications systems.
Optimum design of a cooperative network requires an accurate understanding
of all factors affecting performance. In order to parameterize the performance
of cooperative systems, this thesis introduces mathematical models for different
performance metrics, such as symbol error probability, outage probability and
random coding error exponent, in order to analytically estimate network capacity.
A dual-hop network is introduced as the most basic type of relay network.
Random coding error exponent results have been obtained using this simple network
model are presented along with corresponding channel capacity estimates
based on the assumption of Gaussian input codes. Next, a general multihop
network error and outage performance model are developed.
Detailed mathematical and statistical models for interference relay networks
are presented. The basic statistical parameters, cumulative distribution function
and probability density function for interference cooperative dual hop relay networks
are derived and explored. A partial formulation for the random coding
error exponent (RCEE) result is also presented.
Simulation results over Rayleigh and Nakagami-m fading channel models are
included in each chapter for all of the selected performance metrics in order to
validate the theoretical analysis, under the assumption that channels are flat over
the duration of one symbol transmission. These results are in close agreement
with the predictions of the analytical models.University of Technology, Sydney. Faculty of Engineering and Information Technology
Energy Detection of Unknown Signals over Cascaded Fading Channels
Energy detection is a favorable mechanism in several applications relating to
the identification of deterministic unknown signals such as in radar systems
and cognitive radio communications. The present work quantifies the detrimental
effects of cascaded multipath fading on energy detection and investigates the
corresponding performance capability. A novel analytic solution is firstly
derived for a generic integral that involves a product of the Meijer
function, the Marcum function and arbitrary power terms. This solution
is subsequently employed in the derivation of an exact closed-form expression
for the average probability of detection of unknown signals over *Rayleigh
channels. The offered results are also extended to the case of square-law
selection, which is a relatively simple and effective diversity method. It is
shown that the detection performance is considerably degraded by the number of
cascaded channels and that these effects can be effectively mitigated by a
non-substantial increase of diversity branches.Comment: 12 page
Throughput Scaling of Wireless Networks With Random Connections
This work studies the throughput scaling laws of ad hoc wireless networks in
the limit of a large number of nodes. A random connections model is assumed in
which the channel connections between the nodes are drawn independently from a
common distribution. Transmitting nodes are subject to an on-off strategy, and
receiving nodes employ conventional single-user decoding. The following results
are proven:
1) For a class of connection models with finite mean and variance, the
throughput scaling is upper-bounded by for single-hop schemes, and
for two-hop (and multihop) schemes.
2) The throughput scaling is achievable for a specific
connection model by a two-hop opportunistic relaying scheme, which employs
full, but only local channel state information (CSI) at the receivers, and
partial CSI at the transmitters.
3) By relaxing the constraints of finite mean and variance of the connection
model, linear throughput scaling is achievable with Pareto-type
fading models.Comment: 13 pages, 4 figures, To appear in IEEE Transactions on Information
Theor
Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying over Nakagami-m Fading Channels
published_or_final_versio
A Hop-by-Hop Relay Selection Strategy in Multi-Hop Cognitive Relay Networks
In this paper, a hop-by-hop relay selection strategy for multi-hop underlay cognitive relay networks (CRNs) is proposed. In each stage, relays that successfully decode the message from previous hop form a decoding set. Taking both maximum transmit power and maximum interference constraints into consideration, the relay in the decoding set which has the largest number of channels with an acceptable signal-to-noise ratio (SNR) level to the relays in the next stage is selected for retransmission. Therefore, relay selection in each stage only relies on channel state information (CSI) of the channels in that stage and does not require the CSI of any other stage. We analyze the performance of the proposed strategy in terms of endto-end outage probability and throughput, and show that the results match those obtained from simulation closely. Moreover, we derive the asymptotic end-to-end outage probability of the proposed strategy when there is no upper bound on transmitters’ power. We compare this strategy to other hop-by-hop strategies that have appeared recently in the literature and show that this strategy has the best performance in terms of outage probability and throughput. Finally it is shown that the outage probability and throughput of the proposed strategy are very close to that of exhaustive strategy which provides a lower bound for outage probability and an upper bound for throughput of all path selection strategies
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