In this paper we investigate the performances of Decode-and-forward (DF) assisted by automatic repeat request (ARQ) relaying over Rayleigh fast fading channel. We derive a tight asymptotic approximation of the outage ...
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ISBN:
(纸本)9781467387590
In this paper we investigate the performances of Decode-and-forward (DF) assisted by automatic repeat request (ARQ) relaying over Rayleigh fast fading channel. We derive a tight asymptotic approximation of the outage probability at high signal-to-noise ratio(SNR) regime. Furthermore we formulate an optimization problem aiming at achieving a target outage probability with an optimum allocation of the power budget depending on the relative position of the relay with regard to source and destination.
In this paper, a method for blind identification of linear space-timeblock codes is presented. This relies on a binary tree for decision making, with features based on the empirical cumulative distribution functions ...
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ISBN:
(纸本)9781479965601
In this paper, a method for blind identification of linear space-timeblock codes is presented. This relies on a binary tree for decision making, with features based on the empirical cumulative distribution functions of received signal statistics employed at each node. The proposed method avoids estimation of the channel and noise statistics, and modulation format, and is robust to the carrier frequency offset. Simulation results show that when compared with the existing methods, such as the fourth-order lag product and second-order cyclostationarity-based methods, the proposed non-parametric method exhibits a superior performance.
Spectrum scarcity is an obstacle to deploy emerging high speed wireless services that require more frequency spectrum. Cognitive radio (CR) appears as a promising solution for the spectral congestion by allowing spect...
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Spectrum scarcity is an obstacle to deploy emerging high speed wireless services that require more frequency spectrum. Cognitive radio (CR) appears as a promising solution for the spectral congestion by allowing spectrum sharing between primary and secondary users in which optimum utilization of the available spectrum is achieved. Efficient coex- istence between different users requires full knowledge of the activities in the spectrum of interest. Spectrum awareness is the terminology used to describe the techniques that detect the presence of signals in certain frequency bands, as well as identify the main pa- rameters of such signals, e. g., modulation scheme. These two tasks are commonly referred by the terms spectrum sensing and signal identification, respectively. Blind signal identification was initially used by military applications, such as radio surveillance and electronic warfare, and has recently been extended to civilian applica- tions. This problem becomes more challenging in multiple-input multiple-output (MIMO) scenarios due to the diverse transmission schemes that can be employed, e. g., spatial multi- plexing (SM) and space-timeblock codes (STBCs). A large number of studies have been carried out for developing blind signal identification algorithms in single-input single- output (SISO) scenarios, including identification of the modulation format and recogni- tion of single-carrier (SC) versus multicarrier transmissions. However, the problem of signal identification for MIMO systems remains at an incipient stage. In this dissertation, we develop novel algorithms to blindly identify the MIMO transmission scheme of the received signal. More specifically, in Chapters 2 and 3, we address the problem of identifying STBCs for the SC transmission. Unlike most of the work done to date, we show that STBC iden- tification can be performed using a single receive antenna. Four algorithms are proposed in Chapter 2 to identify SM and Alamouti STBC. Then, the idea
space-time block coding (STBC) can increase the diversity order of spatial modulation MIMO systems. Current deployments consider the use of the optimal detector, which benefits from the decoupled ML detection typical ...
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ISBN:
(纸本)9781467365406
space-time block coding (STBC) can increase the diversity order of spatial modulation MIMO systems. Current deployments consider the use of the optimal detector, which benefits from the decoupled ML detection typical of STBC systems. However, its adaptation to spatial modulation system presents computational complexity increase as more transmit antennas or larger modulation orders are employed, which may turn infeasible its implementation in systems with higher bit rates. This works presents a suboptimal detection strategy for STBC-SM systems based on the generation of a list of candidates, sorted after matched-filtering. A list-length management scheme performs the balance between performance and complexity. Results show that it can achieve near-optimal detection performance with significant computational cost reduction.
space-timecoding is known to be a potential technique for improving the reliability of wireless communication over fading channels. In this paper, we investigate the performance of a space-time coded CDMA system in a...
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ISBN:
(纸本)9781467373098
space-timecoding is known to be a potential technique for improving the reliability of wireless communication over fading channels. In this paper, we investigate the performance of a space-time coded CDMA system in a fading channel. Although significant amount of related work is found in literature, not much reported work exists on the use of Gold codes as spreading sequences in such systems. In this paper, we investigate the performance of a space-timeblock-coded CDMA system for different chip lengths, ranging from 31-chip to 511-chip Gold codes. Results show that at low signal-to-noise ratio, the coding gain provided by the codes surpasses the diversity advantage provided by the use of the multiple antennas. The results also show that coding gain between no-diversity link and its Gold-coded counterpart is the same as that between the transmit-diversity link and its Gold-coded counterpart. The independence of the diversity advantage provided by multiple transmit antennas and the coding gain obtainable from the use of the spreading sequences enables the prediction of the performance of composite space-timeblock-coded CDMA systems.
This paper explores the benefits of application layer forward error correction (AL-FEC) based on Raptor codes for high quality video multicasting over 802.11n multiple-input multiple-output (MIMO) channels. A cross-la...
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ISBN:
(纸本)9781467367820
This paper explores the benefits of application layer forward error correction (AL-FEC) based on Raptor codes for high quality video multicasting over 802.11n multiple-input multiple-output (MIMO) channels. A cross-layer Wi-Fi simulator in combination with a state-of-the-art ray tracing propagation tool was used to analyse the performance of spatial multiplexing (SM) and spacetimeblockcoding (STBC) MIMO techniques under different channel conditions. Simulation results showed that with the use of Raptor code AL-FEC, the operation range of the SM system was increased, i.e., the outage probability was driven to zero even though the MIMO channels were highly correlated. Furthermore, the spectral efficiency was also increased since the SNR gain can be increased up to 10 dB depending on the channel conditions. This results in a higher MCS mode to be selected for the transmission of data. We also presented a MIMO switching algorithm which implements Raptor codes as a means to improve the SM performance and then we evaluated the system under realistic wireless channel conditions.
In this paper we consider a multi relay Decode and Forward (OF) relay network assisted by Hybrid automatic repeat request (HARQ) in a Rayleigh block fading environment. The system uses an incremental relaying strategy...
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ISBN:
(纸本)9781467387095
In this paper we consider a multi relay Decode and Forward (OF) relay network assisted by Hybrid automatic repeat request (HARQ) in a Rayleigh block fading environment. The system uses an incremental relaying strategy in which the best relay is selected to cooperate with source. A space-time block coding (STB) is used for cooperation between source and selected relay to transmit the data to the destination. Relays and destination use maximum ratio combining (MRC) technique to decode the sent message using previously received versions. We derive a closed-form expression of asymptotic outage probability at high Signal-to-Noise Ratio (SNR) regime. We also derive the average delay and throughput in a delay constrained application. The derivation method is based on the Laplace transform, which proves to be a very effective analytical tool when combined with the properties of the special functions. In addition, we investigate the optimum power allocation strategy to minimize the outage probability and consequently maximize the average throughput perceived by the end user. The simulation results show that the obtained analytical bound for the outage probability is very tight at high SNR regime. In addition the proposed power allocation scheme clearly outperforms the equal power allocation.
Recently, spatial modulation (SM) and space-time block coding (STBC) are combined to take advantage of the benefits of both while avoiding their drawbacks for multiple-input and multiple-output (MIMO) systems. The pio...
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ISBN:
(纸本)9781467377881
Recently, spatial modulation (SM) and space-time block coding (STBC) are combined to take advantage of the benefits of both while avoiding their drawbacks for multiple-input and multiple-output (MIMO) systems. The pioneering works on STBC-SM assume that perfect knowledge of the channel fading coefficients is available at the receiver. This work(1) addresses the challenging and timely problem of channel estimation for 4 x 4 STBC-SM systems in the presence of time-varying channels. In this paper, the estimation of channel at pilot durations is done by least square (LS) method and then the channel interpolation is performed by linear interpolation or nearest neighbor interpolation algorithms. Simulation results have demonstrated that the proposed channel estimation based on the linear interpolation offer substantial performance gains over the channel estimation based on the nearest neighbor interpolation. In particular, a savings of about 5dB is obtained at BER = 10(-5), as compared with the nearest interpolation based receiver at 120km/h for 4 x 4 STBC-SM systems with the binary phase shift keying (BPSK) modulation.
In a recent paper [1], Garg et al. present an expression for the exact decoding error probability (DEP) of square orthogonal space-timeblock codes (OSTBCs) with imperfect channel estimation. We show that their DEP ex...
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In a recent paper [1], Garg et al. present an expression for the exact decoding error probability (DEP) of square orthogonal space-timeblock codes (OSTBCs) with imperfect channel estimation. We show that their DEP expression is only asymptotically correct and point out how to obtain the exact result for arbitrary signal-to-noise ratio.
In this letter, an orthogonal space-time (ST) blockcoding (STBC) technique for continuous phase modulation (CPM) is proposed and combined with a frequencydomain equalizer (FDE) to obtain high performance gains over f...
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In this letter, an orthogonal space-time (ST) blockcoding (STBC) technique for continuous phase modulation (CPM) is proposed and combined with a frequencydomain equalizer (FDE) to obtain high performance gains over frequency-selective channels. The new method maintains the constant envelope and phase continuity of the CPM waveforms perfectly by using appropriate tail symbols during the addition of cyclic prefix and interblock transitions and, therefore, has no negative impact on the spectral efficiency. Because the ST-coded CPM blocks remain orthogonal, FDE is applied as in the case of single antenna transmissions without any increase in the computational load. Simulations corroborate the performance improvement offered by STBC while also preserving the desired bandwidth efficiency of CPM.
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