Browsing by Author "Poor, H. Vincent"

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Citation - WoS: 25
Citation - Scopus: 28
Low-Complexity Map-Based Successive Data Detection for Coded Ofdm Systems Over Highly Mobile Wireless Channels
(IEEE-INST Electrical Electronics Engineers Inc, 2011) Panayırcı, Erdal; Dogan, Hakan; Poor, H. Vincent
This paper is concerned with the challenging and timely problem of data detection for coded orthogonal frequency-division multiplexing (OFDM) systems in the presence of frequency-selective and very rapidly time varying channels. New low-complexity maximum a posteriori probability (MAP) data detection algorithms are proposed based on sequential detection with optimal ordering (SDOO) and sequential detection with successive cancellation (SDSC). The received signal vector is optimally decomposed into reduced dimensional subobservations by exploiting the banded structure of the frequency-domain channel matrix whose bandwidth is a parameter to be adjusted according to the speed of the mobile terminal. The data symbols are then detected by the proposed algorithms in a computationally efficient way by means of the Markov chain Monte Carlo (MCMC) technique with Gibbs sampling. The impact of the imperfect channel state information (CSI) on the bit error rate (BER) performance of these algorithms is investigated analytically and by computer simulations. A detailed computational complexity investigation and simulation results indicate that particularly the algorithm based on SDSC has significant performance and complexity advantages and is very robust against channel estimation errors compared with existing suboptimal detection and equalization algorithms proposed earlier in the literature.
Citation - WoS: 81
Citation - Scopus: 92
New Trellis Code Design for Spatial Modulation
(IEEE-INST Electrical Electronics Engineers Inc, 2011) Basar, Ertugrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Spatial modulation (SM) in which multiple antennas are used to convey information besides the conventional M-ary signal constellations is a new multiple-input multiple-output (MIMO) transmission technique which has recently been proposed as an alternative to V-BLAST (vertical Bell Labs layered space-time). In this paper a novel MIMO transmission scheme called spatial modulation with trellis coding (SM-TC) is proposed. Similar to the conventional trellis coded modulation (TCM) in this scheme a trellis encoder and an SM mapper are jointly designed to take advantage of the benefits of both. A soft decision Viterbi decoder which is fed with the soft information supplied by the optimal SM decoder is used at the receiver. A pairwise error probability (PEP) upper bound is derived for the SM-TC scheme in uncorrelated quasi-static Rayleigh fading channels. From the PEP upper bound code design criteria are given and then used to obtain new 4- 8- and 16-state SM-TC schemes using quadrature phase-shift keying (QPSK) and 8-ary phase-shift keying (8-PSK) modulations for 2 3 and 4 bits/s/Hz spectral efficiencies. It is shown via computer simulations and also supported by a theoretical error performance analysis that the proposed SM-TC schemes achieve significantly better error performance than the classical space-time trellis codes and coded V-BLAST systems at the same spectral efficiency yet with reduced decoding complexity.
Citation - WoS: 15
Super-Orthogonal Trellis-Coded Spatial Modulation
(Inst Engineering Technology-IET, 2012) Basar, Ertugrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Spatial modulation (SM) which employs the indices of multiple transmit antennas to transmit information in addition to the conventional M-ary signal constellations is a novel transmission technique that has been proposed for multiple-input multiple-output systems. In this study a new class of space-time trellis codes called 'super-orthogonal trellis-coded SM' (SOTC-SM) is proposed. These codes combine set partitioning and a super set of space-time block coded SM (STBC-SM) codewords to achieve maximal diversity and coding gains by exploiting both SM and space-time block codes. Unlike super-orthogonal space-time trellis codes (SOSTTCs) which parametrise the orthogonal STBCs these new codes expand the antenna constellation using the principle of SM. Systematic construction methods are presented for the SOTC-SM scheme and design examples are given for 2 4 and 8 trellis states at 2 3 and 4 bits/s/Hz spectral efficiencies. The approximate bit-error probability performance of SOTC-SM is derived and shown to match computer simulation results. A simplified maximum likelihood detection method for the proposed scheme is given. It is shown through computer simulations that the proposed SOTC-SM schemes achieve significantly better error performance than SOSTTCs with comparable complexity.
Citation - WoS: 906
Orthogonal Frequency Division Multiplexing With Index Modulation
(IEEE-INST Electrical Electronics Engineers Inc, 2013) Başar, Ertuğrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
In this paper a novel orthogonal frequency division multiplexing (OFDM) scheme called OFDM with index modulation (OFDM-IM) is proposed for operation over frequency-selective and rapidly time-varying fading channels. In this scheme the information is conveyed not only by M-ary signal constellations as in classical OFDM but also by the indices of the subcarriers which are activated according to the incoming bit stream. Different low complexity transceiver structures based on maximum likelihood detection or log-likelihood ratio calculation are proposed and a theoretical error performance analysis is provided for the new scheme operating under ideal channel conditions. Then the proposed scheme is adapted to realistic channel conditions such as imperfect channel state information and very high mobility cases by modifying the receiver structure. The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors. For themobility case several interference unaware/aware detection methods are proposed for the new scheme. It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions.
Citation - Scopus: 26
Low-Complexity Joint Data Detection and Channel Equalisation for Highly Mobile Orthogonal Frequency Division Multiplexing Systems
(2010) Dogan, Hakan; Panayırcı, Erdal; Poor, H. Vincent
This study is concerned with the challenging and timely problem of channel equalisation and data detection for orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency-selective and very rapidly time-varying channels. The algorithm is based on the space alternating generalised expectation-maximisation (SAGE) technique which is particularly well suited to multicarrier signal formats and can be easily extended to multi-input multi-output-OFDM systems. In fast fading channels the orthogonality between subcarriers is destroyed by the time variation of a fading channel over an OFDM symbol duration which causes severe inter-carrier interference (ICI) and in conventional frequency-domain approaches results in an irreducible error floor. The proposed joint data detection and equalisation algorithm updates the data sequences in series leading to a receiver structure that also incorporates ICI cancellation enabling the system to operate at high vehicle speeds. A computational complexity investigation as well as detailed computer simulations indicate that this algorithm has significant performance and complexity advantages over existing suboptimal detection and equalisation algorithms proposed earlier in the literature. © 2010 The Institution of Engineering and Technology.
Citation - WoS: 6
Citation - Scopus: 7
Physical Layer Security With Dco-Ofdm Vlc Under the Effects of Clipping Noise and Imperfect Csi
(Ieee-inst Electrical Electronics Engineers inc, 2024) Panayirci, Erdal; Bektas, Ekin B.; Poor, H. Vincent
Visible light communications (VLC) and physical-layer security (PLS) are key candidate technologies for 6G wireless communication. This paper combines these two technologies by considering an orthogonal frequency division multiplexing (OFDM) technique called DC-biased optical OFDM (DCO-OFDM) equipped with PLS as applied to indoor VLC systems. First, a novel PLS algorithm is designed to protect the DCO-OFDM transmission of the legitimate user from an eavesdropper. A closed-form expression for the achievable secrecy rate is derived and compared with the conventional DCO-OFDM without security. To analyze the security performance of the PLS algorithm under the effects of the residual clipping noise and the channel estimation errors, a closed-form expression is derived for a Bayesian estimator of the clipping noise induced naturally at the DCO-OFDM systems after estimating the optical channel impulse response (CIR), by a pilot-aided sparse channel estimation algorithm with the compressed sensing approach, in the form of the orthogonal matching pursuit (OMP), and the least-squares (LS). Finally, from the numerical and the computer simulations, it is shown that the proposed PLS algorithm with secret key exchange guarantees the eavesdropper's BER to stay close to 0.5 and that the proposed encryption-based PLS algorithm does not affect the BER performance of the legitimate user in the system.
Citation - WoS: 13
Spatial Modulation Aided Physical Layer Security for NOMA-VLC Systems
(Ieee-inst Electrical Electronics Engineers inc, 2023) Panayirci, Erdal; Koca, Mutlu; Haas, Harald; Poor, H. Vincent
We consider the physical layer security (PLS) problem in multi-user non-orthogonal multiple access (NOMA) enabled multiple-input multiple-output (MIMO) visible light communication systems intercepted by a passive eavesdropper (Eve). We propose a novel transmit precoding scheme based on receive spatial modulation (RSM) to degrade the signal-to-interference-noise ratio (SINR) of Eve by exploiting only the slow-fading characteristics of the visible light channel of the legitimate users (Bobs). The proposed PLS precoder is reinforced with secret parameter exchange with Bobs and a CSI acquisition model is proposed to reduce the PLS algorithm's computational load substantially at the transmitter. The closed-form expressions for the achievable secrecy rates and their upper and lower bounds are derived. Via Monte Carlo simulations, we confirm that Bobs can successfully decode their information in various user configurations while Eve's received SINR is significantly worsened by the jamming signal induced by the proposed precoder with secret key exchange. It is also shown that Eve's bit error rate (BER) is increased to the 0.5-level for almost any position in the considered indoor environment. Finally, we corroborate the derived secrecy expressions by computer simulations and show that the proposed scheme provides PLS for Bobs.
Citation - WoS: 2
Citation - Scopus: 3
Reliable Two-Path Successive Relaying
(2013) Basar, Ertugrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Emerging two-path successive relaying protocols generally rely on error-free source-relay channels and/or interference-free inter-relay channels to achieve high-rate and full-diversity. In this paper by removing these optimistic assumptions a novel two-path successive relaying scheme that benefits from relay selection and distributed space-time block coding (STBC) and transfers the data from the source to the destination via relays in a reliable fashion is proposed. The proposed scheme can achieve full diversity without the requirement of perfect decoding at relays since not only the destination but also the relays benefit from distributed STBC and relay selection. As the target STBC coordinate interleaved orthogonal design (CIOD) for two transmit antennas is considered. The average symbol error probability of the proposed scheme is derived and its error performance is compared with reference systems. © 2013 IEEE.
Trellis Coding For Spatial Modulation [uzaysal Modulasyon İ?çi?n Kafes Kodlama]
(2011) Basar, Ertugrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
In this study by combining trellis coding with spatial modulation (SM) a new multiple-input multiple output (MIMO) communication scheme called trellis coded spatial modulation (TC-SM) is proposed. For uncorrelated Rayleigh fading channels code design criteria are given by deriving pairwise error probability (PEP) of this system in which a trellis encoder and SM mapper are jointly designed. These criteria are then used to obtain 4 8 and 16-states TC-SM schemes. It is shown via computer simulations that the proposed TC-SM schemes achieve better error performance than the classical space-time trellis codes with reduced decoder complexity. © 2011 IEEE.
Citation - WoS: 40
Citation - Scopus: 49
Sparse Channel Estimation and Equalization for Ofdm-Based Underwater Cooperative Systemsw With Amplify-And Relaying
(IEEE-INST Electrical Electronics Engineers Inc, 2016) Panayırcı, Erdal; Şenol, Habib; Uysal, Murat; Poor, H. Vincent
This paper is concerned with a challenging problem of channel estimation and equalization for amplify-and-forward cooperative relay based orthogonal frequency division multi-plexing (OFDM) systems in sparse underwater acoustic (UWA) channels. The sparseness of the channel impulse response and prior information for the non-Gaussian channel gains modeled by an exact continuous Gaussian mixture (CGM) are exploited to improve the performance of the channel estimation algorithm. The resulting novel algorithm initially estimates the overall sparse complex-valued channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The effective time-domain non-Gaussian noise is approximated well as a Gaussian noise in the frequency-domain where the estimation takes place. An efficient and low complexity algorithm is developed based on a combination of the MP and the maximum a posteriori probability (MAP) based space-alternating generalized expectation-maximization technique to improve the estimates of the channel taps and their locations in an iterative manner. Computer simulations show that the UWA channel is estimated very effectively and the proposed algorithm exhibits excellent symbol error rate and channel estimation performance.
Citation - WoS: 11
Citation - Scopus: 11
Space-Time Block Coding for Spatial Modulation
(IEEE, 2010) Başar, Ertuğrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Space-time block coded spatial modulation (STBC-SM) which employs space-time block coding (STBC) for spatial modulation (SM) is proposed as a new multiple-input multiple-output (MIMO) transmission scheme. In the STBC-SM scheme the transmitted information symbols are expanded not only to the space and time domains but also to the spatial (antenna) domain therefore both core STBC and antenna indices carry information. A general framework is presented for the design of the STBC-SM scheme for any number of transmit antennas. The proposed scheme is optimized by deriving its diversity and coding gains to exploit the diversity advantage of STBC. A low-complexity maximum likelihood (ML) decoder is given for the new scheme. It is shown by computer simulations that STBC-SM provides approximately 3-5 dB (depending on the spectral efficiency) better error performance than SM and V-BLAST systems.
Citation - WoS: 4
Citation - Scopus: 18
Sparse Channel Estimation for Space-Time Block Coded Ofdm-Based Underwater Acoustic Channels
(Institute of Electrical and Electronics Engineers Inc., 2018) Altabbaa, Mhd Tahssin; Öğrenci, Arif Selçuk; Panayırcı, Erdal; Poor, H. Vincent
Communication over acoustic signals underwater results in multi-scale multi-lag channels due to multipath propagation. Hence a robust channel estimation technique has to be present at the receiver. In this paper assuming underwater channels undergoing Rayleigh fading a path-based channel model that characterizes each path of the time-varying sparse channel by a delay a Doppler scale and an attenuation factor is considered. Alamouti's space-time block transmit diversity scheme is used in the form of two transmit antennas and one receiver and the proposed OFDM-based non-data-aided algorithm iteratively estimates the complex channel parameters of each subcarrier using the expectation maximization (EM) method which in turn converges to a true maximum a posteriori probability (MAP) estimate of the unknown channel where the Karhunen-Lo'eve expansion is performed for complexity reduction. Finally the novel channel estimation algorithm combines the aforementioned MAP-EM technique with ESPRIT for delay estimation by exploiting the sparseness of the underwater acoustic channels. The performance of the proposed algorithm is then presented in terms of average mean square error and symbol error rate for QPSK signaling with extreme Doppler spreads and different pilot spacings. It is shown that excellent mean-square error and symbol error rate performance is achieved even in the presence of extreme Doppler shifts. © 2018 IEEE.
Citation - Scopus: 1
Semiblind Joint Channel Estimation and Equalization for Ofdm Systems in Rapidly Varying Channels
(2010) Şenol, Habib; Panayırcı, Erdal; Poor, H. Vincent; Oğuz, Onur; Vandendorpe, Luc
We describe a new joint iterative channel estimation and equalization algorithm for joint channel estimation and data detection for orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency selective and rapidly timevarying channels. The algorithm is based on the expectation maximization-maximum a posteriori (EM-MAP) technique which is very suitable for the multicarrier signal formats. The algorithm leads to a receiver structure that yields the equalized output using the channel estimates. The pilot symbols are employed to estimate the initial channel coefficients effectively and unknown data symbols are averaged out in the algorithm. The band-limited discrete cosine serial expansion of low dimensionality is employed to represent the time-varying fading channel. In this way the resulting reduced dimensional channel coefficients are estimated iteratively with tractable complexity. The extensive computer simulations show that the algorithm has excellent symbol error rate (SER) and mean square error (MSE) performances for very high mobility even during the initialization step. Copyright © ?enol et. al.
Secure Optical Coded GSSK System with Dimming
(IEEE, 2024) Hassan, Sumeyra; Panayirci, Erdal; Helleseth, Tor; Poor, H. Vincent
In this work, we develop an indoor visible light communications (VLC) system based on a transmitted precoded (TPC)-aided, coded generalized space shift keying (GSSK) system with physical layer security (PLS) capability in the presence of dimming. A new design of the encoder and decoder of linear codes is given to improve the error-correcting capability of the system as well as to enable random selection of the activated indices in the GSSK automatically. The PLS of the system is guaranteed by the appropriate selection of the power allocation coefficients for randomly activated photodiodes (PDs). At the receiver, the unknown channel and dimming coefficients are jointly estimated in the legitimate users with a new pilot-aided estimation technique. Then, the optimal detection of the spatial symbols is implemented using the maximum likelihood (ML) criterion in the presence of dimming. It is shown that the dimming coefficients, unknown to the eavesdropper, provide additional PLS for the legitimate user. The computer simulations show that the legitimate user achieves excellent bit error performance mainly due to the linear coding employed that serves for error correction and selection of the best GSSK constellation in the system. In contrast, the bit error performance of the potential eavesdroppers is significantly degraded.
Citation - WoS: 8
Citation - Scopus: 8
Spatial Constellation Design Based Generalized Space Shift Keying for Physical Layer Security of Multi-User MIMO Communication Systems
(Institute of Electrical and Electronics Engineers Inc., 2021) Su, Nugman; Panayırcı, Erdal; Koca, Mutlu; Poor, H. Vincent
We propose a novel spatial constellation design (SCD) method with generalized space shift keying (GSSK-SCD) signaling for physical layer security (PLS) in multi-user (MU) multiple-input multiple-output (MIMO) communication systems. In GSSK-SCD, the received spatial constellations are optimized through a novel precoding scheme, which minimizes the BERs at legitimate users and significantly worsens eavesdroppers’ BER. In addition to extensive BER simulations, we also provide analytical expressions for the secrecy rate regions for the proposed GSSK-SCD. Both analytical derivations and simulation results, including comparisons with artificial noise aided conventional GSSK, reveal that the GSSK-SCD approach provides significant PLS improvements for MU-MIMO systems.
Citation - WoS: 1
Joint Channel Estimation and Equalization for Ofdm Based Broadband Communications in Rapidly Varying Mobile Channels
(IEEE, 2010) Şenol, Habib; Poor, H. Vincent
This paper is concerned with the challenging and timely problem of channel estimation for orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency selective and very rapidly time varying channels. In OFDM systems operating over rapidly time-varying channels the orthogonality between subcarriers is destroyed leading to inter-carrier interference (ICI) and resulting in an irreducible error floor. The band-limited discrete cosine serial expansion of low-dimensionality is employed to represent the time-varying channel. In this way the resulting reduced dimensional channel coefficients are estimated iteratively with tractable complexity and independently of the channel statistics. The algorithm is based on the expectation maximization-maximum a posteriori probability (EM-MAP) technique leading to a receiver structure that also yields the equalized output using the channel estimates. The pilot symbols are employed to estimate the initial coefficients effectively and unknown data symbols are averaged out in the algorithm in a non-data-aided fashion. It is shown that the computational complexity of the proposed algorithm to estimate the channel coefficients and to generate the equalized output as a by-product is similar to O(N) per detected symbol N being the number of OFDM subcarriers. Computational complexity as well as computer simulations carried out for the systems described in WiMAX and LTE standards indicate that it has significant performance and complexity advantages over existing suboptimal channel estimation and equalization algorithms proposed earlier in the literature.
Citation - WoS: 5
Citation - Scopus: 5
Relay-Aided Secure Broadcasting for Vlc
(IEEE, 2018) Arafa, Ahmed; Panayırcı, Erdal; Poor, H. Vincent
A visible light communication (VLC) broadcast channel is considered in which a transmitter communicates with two receivers in the presence of an external eavesdropper. Trusted cooperative half-duplex relays are deployed to aid with securing the transmitted data. Transmission is amplitude-constrained to maintain operation within the light emitting diodes (LEDs) dynamic range. Achievable secrecy rate regions are derived under such amplitude constraints for this multi receiver wiretap channel first for direct transmission without the relays and then for cooperative jamming decode-and-forward and amplify-and-forward relaying schemes. Superposition coding with uniform signaling is used for transmission along with secure beamforming at the relays. Superiority of the secure relaying schemes over direct transmission is shown with performance depending on how far the eavesdropper is from the transmitter and the relays.
Citation - Scopus: 15
Spatial Modulation Aided Physical Layer Security for Noma-Vlc Systems
(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Panayırcı, Erdal; Koca, Mutlu; Haas, Harald; Poor, H. Vincent
We consider the physical layer security (PLS) problem in multi-user non-orthogonal multiple access (NOMA) enabled multiple-input multiple-output (MIMO) visible light communication systems intercepted by a passive eavesdropper (Eve). We propose a novel transmit precoding scheme based on receive spatial modulation (RSM) to degrade the signal-to-interference-noise ratio (SINR) of Eve by exploiting only the slow-fading characteristics of the visible light channel of the legitimate users (Bobs). The proposed PLS precoder is reinforced with secret parameter exchange with Bobs and a CSI acquisition model is proposed to reduce the PLS algorithm's computational load substantially at the transmitter. The closed-form expressions for the achievable secrecy rates and their upper and lower bounds are derived. Via Monte Carlo simulations, we confirm that Bobs can successfully decode their information in various user configurations while Eve's received SINR is significantly worsened by the jamming signal induced by the proposed precoder with secret key exchange. It is also shown that Eve's bit error rate (BER) is increased to the 0.5-level for almost any position in the considered indoor environment. Finally, we corroborate the derived secrecy expressions by computer simulations and show that the proposed scheme provides PLS for Bobs.
Citation - WoS: 150
Citation - Scopus: 164
Performance of Spatial Modulation in the Presence of Channel Estimation Errors
(IEEE-INST Electrical Electronics Engineers Inc, 2012) Basar, Ertuğrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
This work investigates the negative effects of channel estimation errors on the performance of spatial modulation (SM) when operating over flat Rayleigh fading channels. The pairwise error probability of the SM scheme is derived in the presence of channel estimation errors and an upper bound on the average bit error probability is evaluated for M-PSK and M-QAM signalling. It is shown via computer simulations that the derived upper bound becomes very tight with increasing signal-to-noise ratio (SNR) and the SM scheme is quite robust to channel estimation errors.
Citation - WoS: 11
Citation - Scopus: 12
A Reliable Successive Relaying Protocol
(IEEE-INST Electrical Electronics Engineers Inc, 2014) Başar, Ertuğrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Successive relaying has recently emerged as an effective technique for cooperative networks and provides significant improvements in bandwidth efficiency over traditional relaying techniques ;however to achieve full-diversity the available successive relaying protocols generally assume noise-free sourcerelay and interference-free inter-relay channels. In this paper a novel successive relaying protocol is proposed for N-relay wireless networks by removing these optimistic assumptions. The proposed protocol benefits from distributed space-time block codes (STBCs) with coordinate interleaving and relay selection. It achieves a diversity order of two and high transmission rate under realistic network conditions with single-symbol maximum likelihood (ML) detection. A general N-relay signaling protocol is presented and specific design examples are given for N = 2 3 and 4-relay cooperative networks. The average symbol error probability (ASEP) is analytically derived and shown to match with computer simulation results. It is also shown via computer simulations that the proposed scheme achieves significantly better error performance and is more robust to channel estimation errors than its counterparts given in the literature under realistic network conditions.