847 research outputs found
Design guidelines for spatial modulation
A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants
Timing synchronization for cooperative wireless communications
In this work the effect of perfect and imperfect synchronization on the performance
of single-link and cooperative communication is investigated. A feedforward non- data-aided near maximum likelihood (NDA-NML) timing estimator which is effective for an additive white Gaussian noise (AWGN) channel and also for a flat-fading channel, is developed. The Cramer Rao bound (CRB) and modified Cramer Rao bound (MCRB) for the estimator for a single-link transmission over an AWGN channel is derived. A closed form expression for the probability distribution of the timing estimator is also derived. The bit-error-rate (BER) degradation of the NDA-NML timing estimator with raised cosine pulse shaping for static timing errors over an AWGN channel is characterized. A closed form expression is derived for the conditional bit error probability (BEP) with static timing errors of binary phase shift keying modulation over a Rayleigh fading channel using rectangular pulse shaping. The NDA-NML timing estimator is applied to a cooperative communication system with a source, a relay and a destination. A CRB for the estimator for asymptotically low signal-to-noise-ratio case is derived. The timing complexity of the NDA-NML estimator is derived and compared with a feedforward correlation based data-aided maximum likelihood (DA-ML) estimator. The BER performance of this system operating with a detect-and-forward relaying is studied, where the symbol timings are estimated independently for each channel. A feedforward data and channel aided maximum likelihood (DCA-ML) symbol timing estimator for cooperative communication operating over flat fading channels is then developed.
For more severe fading the DCA-ML estimator performs better than the NDA- NML estimator and the DA-ML estimator. The performance gains of the DCA-ML estimator over that of the DA-ML estimator become more significant in cooperative transmission than in single-link node-to-node transmission. The NDA-NML symbol timing estimator is applied to three-node cooperative communication in fast flat-fading conditions with various signal constellations. It is found that timing errors have significant effect on performance in fast flat-fading channels. The lower complexity NDA-NML estimator performs well for larger signal constellations in fast fading, when compared to DA-ML estimator. The application of cooperative techniques for saving transmit power is discussed along with the related performance analysis with timing synchronization errors. It is found that power allocations at the source and relay nodes for transmissions, and the related timing errors at the relay and the destination nodes, have considerable effect on the BER performance for power constrained cooperative communication. The performance of multi-node multi-relay decode-and-forward cooperative com- munication system, of various architectures, operating under different fading con- ditions, with timing synchronization and various combining methods, is presented. Switch-and-stay combining and switch-and-examine combining are proposed for multi-node cooperative communication. Apart from the proposed two combining methods equal gain combining, maximal ratio combining and selection combining are also used. It is demonstrated that synchronization error has significant effect on performance in cooperative communication with a range of system architectures, and it is also demonstrated that performance degradation due to synchronization error increases with increasing diversity. It is demonstrated that decode-and- forward relaying strategy with timing synchronization, using a very simple coding scheme, performs better than detect-and-forward relaying with timing synchronization. Analytical expressions are derived for BEP with static and dynamic timing synchronization errors over Rayleigh fading channels using rectangular pulse shaping for amplify-and-forward and detect-and-forward cooperative communications.
Moment generating function (MGF) based approach is utilized to find the analytical expressions. It is found that timing synchronization errors have an antagonistic effect on the BEP performance of cooperative communication. With the relay intelligence of knowing whether symbols are detected correctly or not, detect- and-forward cooperative communication performs better than the low complexity amplify-and-forward cooperative communication
Cooperative Relaying with CPFSK and Distributed Space-Time Trellis Codes
Cooperative relaying allows single antenna users to achieve diversity and coding gains by utilizing nearby users' transmitting capabilities. We consider a relay system employing constant envelope continuous phase frequency shift keying. Distributed space-time trellis codes are implemented with a novel multiple relay protocol
Cooperative Relaying with CPFSK and Distributed Space-Time Trellis Codes
Cooperative relaying allows single antenna users to achieve diversity and coding gains by utilizing nearby users' transmitting capabilities. We consider a relay system employing constant envelope continuous phase frequency shift keying. Distributed space-time trellis codes are implemented with a novel multiple relay protocol
Cooperative Transmission Techniques in Wireless Communication Networks
Cooperative communication networks have received significant interests from both
academia and industry in the past decade due to its ability to provide spatial diversity
without the need of implementing multiple transmit and/or receive antennas at the
end-user terminals. These new communication networks have inspired novel ideas
and approaches to find out what and how performance improvement can be provided
with cooperative communications. The objective of this thesis is to design and analyze
various cooperative transmission techniques under the two common relaying signal
processing methods, namely decode-and-forward (DF) and amplify-and-forward
(AF).
For the DF method, the thesis focuses on providing performance improvement
by mitigating detection errors at the relay(s). In particular, the relaying action is
implemented adaptively to reduce the phenomenon of error propagation: whether or
not a relay’s decision to retransmit depends on its decision variable and a predefined
threshold. First, under the scenario that unequal error protection is employed to
transmit different information classes at the source, a relaying protocol in a singlerelay
network is proposed and its error performance is evaluated. It is shown that
by setting the optimal signal-to-noise ratio (SNR) thresholds at the relay for different
information classes, the overall error performance can be significantly improved.
Second, for multiple-relay networks, a relay selection protocol, also based on SNR
thresholds, is proposed and the optimal thresholds are also provided. Third, an
adaptive relaying protocol and a low-complexity receiver are proposed when binary
frequency-shift-keying (FSK) modulation is employed and neither the receiver nor the
transmitter knows the fading coefficients. It is demonstrated that large performance
improvements are possible when the optimal thresholds are implemented at the relays
and destination. Finally, under the scenario that there is information feedback
from the destination to the relays, a novel protocol is developed to achieve the maximum
transmission throughput over a multiple-relay network while the bit-error rate
satisfies a given constraint.
With the AF method, the thesis examines a fixed-gain multiple-relay network
in which the channels are temporally-correlated Rayleigh flat fading. Developed is
a general framework for maximum-ratio-combining detection when M-FSK modulation
is used and no channel state information is available at the destination. In
particular, an upper-bound expression on the system’s error performance is derived
and used to verify that the system achieves the maximal diversity order. Simulation
results demonstrate that the proposed scheme outperforms the existing schemes for
the multiple-relay network under consideration
Improving Bandwidth Efficiency in E-band Communication Systems
The allocation of a large amount of bandwidth by regulating bodies in the
70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges
for providing affordable and reliable Gigabit per second wireless
point-to-point links. This article first reviews the available bandwidth and
licensing regulations in the E-band. Subsequently, different propagation
models, e.g., the ITU-R and Cane models, are compared against measurement
results and it is concluded that to meet specific availability requirements,
E-band wireless systems may need to be designed with larger fade margins
compared to microwave systems. A similar comparison is carried out between
measurements and models for oscillator phase noise. It is confirmed that phase
noise characteristics, that are neglected by the models used for narrowband
systems, need to be taken into account for the wideband systems deployed in the
E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed
continuous aperture phased (CAP)-MIMO, is presented. Simulations show that
CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs.
Finally, it is argued that full-duplex relaying can be used to greatly enhance
the coverage of E-band systems without sacrificing throughput, thus,
facilitating their application in establishing the backhaul of heterogeneous
networks.Comment: 16 pages, 6 Figures, Journal paper. IEEE Communication Magazine 201
Performance analysis of diversity techniques in wireless communication systems: Cooperative systems with CCI and MIMO-OFDM systems
This Dissertation analyzes the performance of ecient digital commu- nication systems, the performance analysis includes the bit error rate (BER) of dier- ent binary and M-ary modulation schemes, and the average channel capacity (ACC) under dierent adaptive transmission protocols, namely, the simultaneous power and rate adaptation protocol (OPRA), the optimal rate with xed power protocol (ORA), the channel inversion with xed rate protocol (CIFR), and the truncated channel in- version with xed transmit power protocol (CTIFR). In this dissertation, BER and ACC performance of interference-limited dual-hop decode-and-forward (DF) relay- ing cooperative systems with co-channel interference (CCI) at both the relay and destination nodes is analyzed in small-scale multipath Nakagami-m fading channels with arbitrary (integer as well as non-integer) values of m. This channel condition is assumed for both the desired signal as well as co-channel interfering signals. In addition, the practical case of unequal average fading powers between the two hops is assumed in the analysis. The analysis assumes an arbitrary number of indepen- dent and non-identically distributed (i.n.i.d.) interfering signals at both relay (R) and destination (D) nodes. Also, the work extended to the case when the receiver employs the maximum ratio combining (MRC) and the equal gain combining (EGC) schemes to exploit the diversity gain
Two-Way Relaying Using Constant Envelope Modulation and Phase-Superposition-Phase-Forward
In this article, we propose the idea of phase-superposition-phase-forward (PSPF) relaying for 2-way 3-phasecooperative network involving constant envelope modulation with discriminator detection in a time-selectiveRayleigh fading environment. A semi-analytical expression for the bit-error-rate (BER) of this system is derived andthe results are verified by simulation. It was found that, compared to one-way relaying, 2-way relaying with PSPFsuffers only a moderate loss in energy efficiency (of 1.5 dB). On the other hand, PSPF improves the transmissionefficiency by 33%. Furthermore, we believe that the loss in transmission efficiency can be reduced if power isallocated to the different nodes in this cooperative network in an ‘optimal’ fashion. To further put the performanceof the proposed PSPF scheme into perspective, we compare it against a phase-combining phase-forwardtechnique that is based on decode-and-forward (DF) and multi-level CPFSK re-modulation at the relay. It wasfound that DF has a higher BER than PSPF and requires additional processing at the relay. It can thus beconcluded that the proposed PSPF technique is indeed the preferred way to maintain constant envelope signalingthroughout the signaling chain in a 2-way 3 phase relaying system
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
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