75 research outputs found
Performance Analysis of Coherent and Noncoherent Modulation under I/Q Imbalance
In-phase/quadrature-phase Imbalance (IQI) is considered a major
performance-limiting impairment in direct-conversion transceivers. Its effects
become even more pronounced at higher carrier frequencies such as the
millimeter-wave frequency bands being considered for 5G systems. In this paper,
we quantify the effects of IQI on the performance of different modulation
schemes under multipath fading channels. This is realized by developing a
general framework for the symbol error rate (SER) analysis of coherent phase
shift keying, noncoherent differential phase shift keying and noncoherent
frequency shift keying under IQI effects. In this context, the moment
generating function of the signal-to-interference-plus-noise-ratio is first
derived for both single-carrier and multi-carrier systems suffering from
transmitter (TX) IQI only, receiver (RX) IQI only and joint TX/RX IQI.
Capitalizing on this, we derive analytic expressions for the SER of the
different modulation schemes. These expressions are corroborated by comparisons
with corresponding results from computer simulations and they provide insights
into the dependence of IQI on the system parameters. We demonstrate that the
effects of IQI differ considerably depending on the considered system as some
cases of single-carrier transmission appear robust to IQI, whereas
multi-carrier systems experiencing IQI at the RX require compensation in order
to achieve a reliable communication link
マルチホップ無線ネットワークの特性解析に関する研究
九州工業大学博士学位論文 学位記番号:情工博甲第309号 学位授与年月日:平成28年3月25日1 Introduction||2 Impact of Transceiver Hardware Impairments on Cognitive Network||3 Case study: Two-Way Cognitive Relay in RF Energy HarvestingWireless Sensor Network||4 Soft Information Relaying Protocol||5 Overall Conclusion and FutureWorkWireless communication has been considered as the most efficient mean of data
transmission. We have been witnessed the breakthrough of wireless communication
era in many manifolds, such as speech, coverage area, and stability. However,
frequency bands, the resource to convey information wirelessly, are limited and expensive
to be granted usage licenses.
Attaining the goals of ubiquitous wireless devices will require the future wireless
networks stepping forward to overcome the scarcity and expensiveness of wireless
frequency bands. Thus, the future wireless networks should evolve to utilize wireless
frequencies more efficiently, such as cognitive relay network where non-license
users are able to transmit data in the same frequency band that officially allocated to
primary users. Subsequently, the transmit power of users in a cognitive network is
limited and the performance is vulnerable to impairments of transceiver hardware.
This dissertation aims to analyze the performance of the cognitive relay network
under the impact of transceiver hardware impairments. A case study of two-way
cognitive relay network is given for further investigate the impact of transceiver
hardware impairments on end-to-end outage performance and throughput. Furthermore,
we provide a new relaying scheme in order to lessen the impact of transceiver
hardware impairment and further boost the system performance. For the purposes,
this dissertation is organized into five (5) chapters.
Chapter 1: Introduction. In this chapter, multihop wireless networks and the performance
metrics are overviewed. In particular, the relay networks and cognitive relay
networks are presented. Moreover, the general model of the practical transceiver
hardware impairment is detailed for further analysis.
Chapter 2: The impact of transceiver hardware impairments on cognitive relay networks.
By using the general hardware impairment model for the received signal, the
closed forms of outage probability of the relay network with decode-and-forward
(DF) and amplify-and-forward (AF) under the impact of transceiver hardware imperfection
are derived. Based on these results, we provide further discussion on
transceiver hardware selection guideline.
Chapter 3: Case study: two-way cognitive relaying in energy harvesting wireless
sensor networks. A two-way relay wireless sensor network equipped with
RF energy harvesting node is introduced. This network is aimed to be implemented
in hazardous or remote areas where power supply for the relay node is
difficult to maintain. In this chapter, we consider four configurations of the network
with formed by combining two bidirectional relaying protocols and two wireless
power transfer policies. The detailed performance analysis of outage probability
and throughput of the case-study network with four configurations are presented.
Based on the analysis, we provide performance comparison between the four and
suggest the network configuration with the best performance.
Chapter 4: Soft information relaying protocol. The soft information relaying protocol
is proposed and analyzed. The analysis shows that this relaying protocol can
gradually reduce the impact of transceiver hardware impairment on cognitive relay
networks. Hence, soft relaying protocol is considered as a solution for cognitive
relay network with cost-effective wireless transceiver devices.
Chapter 5: Overall conclusion. An overall summary of the works presented in
the above is provided in this chapter. Moreover, the future related work is also
discussed.
The results in this dissertation acknowledge the impact of transceiver hardware impairment
by presenting the reduction of outage probability and throughput of the
cognitive relay network. It puts forward the consideration of including the impact
of transceiver hardware impairments on wireless network performance analysis, especially
for the cognitive networks of which the transmit power is limited.
Furthermore, a new relaying protocol, namely soft information relaying protocol,
is proposed as a solution to lessen the impact of transceiver hardware impairment.
The analysis shows that the impact of transceiver hardware impairment in cognitive
relay network is reduced in compared to conventional relaying schemes.
As a final point, we have provided a full picture of performance analysis for the
cognitive relay network under the impact of transceiver hardware imperfection and
the solution to reduce the performance loss by applying soft information relaying
scheme. This research would contribute to boost the development of cognitive relay
networks where frequency bands are used more efficiently
Advanced DSP Algorithms For Modern Wireless Communication Transceivers
A higher network throughput, a minimized delay and reliable communications
are some of many goals that wireless communication standards, such as the fifthgeneration
(5G) standard and beyond, intend to guarantee for its customers. Hence,
many key innovations are currently being proposed and investigated by researchers in
the academic and industry circles to fulfill these goals. This dissertation investigates
some of the proposed techniques that aim at increasing the spectral efficiency, enhancing
the energy efficiency, and enabling low latency wireless communications systems.
The contributions lay in the evaluation of the performance of several proposed receiver
architectures as well as proposing novel digital signal processing (DSP) algorithms to
enhance the performance of radio transceivers. Particularly, the effects of several radio
frequency (RF) impairments on the functionality of a new class of wireless transceivers,
the full-duplex transceivers, are thoroughly investigated. These transceivers are then
designed to operate in a relaying scenario, where relay selection and beamforming
are applied in a relaying network to increase its spectral efficiency. The dissertation
then investigates the use of greedy algorithms in recovering orthogonal frequency
division multiplexing (OFDM) signals by using sparse equalizers, which carry out the
equalization in a more efficient manner when the low-complexity single tap OFDM
equalizer can no longer recover the received signal due to severe interferences. The
proposed sparse equalizers are shown to perform close to conventional optimal and
dense equalizers when the OFDM signals are impaired by interferences caused by the
insertion of an insufficient cyclic prefix and RF impairments
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