Showing papers on "Bit error rate published in 2014"

Generalized Frequency Division Multiplexing for 5th Generation Cellular Networks

Abstract: Cellular systems of the fourth generation (4G) have been optimized to provide high data rates and reliable coverage to mobile users. Cellular systems of the next generation will face more diverse application requirements: the demand for higher data rates exceeds 4G capabilities; battery-driven communication sensors need ultra-low power consumption; and control applications require very short response times. We envision a unified physical layer waveform, referred to as generalized frequency division multiplexing (GFDM), to address these requirements. In this paper, we analyze the main characteristics of the proposed waveform and highlight relevant features. After introducing the principles of GFDM, this paper contributes to the following areas: 1) the means for engineering the waveform's spectral properties; 2) analytical analysis of symbol error performance over different channel models; 3) concepts for MIMO-GFDM to achieve diversity; 4) preamble-based synchronization that preserves the excellent spectral properties of the waveform; 5) bit error rate performance for channel coded GFDM transmission using iterative receivers; 6) relevant application scenarios and suitable GFDM parameterizations; and 7) GFDM proof-of-concept and implementation aspects of the prototype using hardware platforms available today. In summary, the flexible nature of GFDM makes this waveform a suitable candidate for future 5G networks.

Practical quantum key distribution protocol without monitoring signal disturbance

Abstract: Quantum cryptography exploits the fundamental laws of quantum mechanics to provide a secure way to exchange private information. Such an exchange requires a common random bit sequence, called a key, to be shared secretly between the sender and the receiver. The basic idea behind quantum key distribution (QKD) has widely been understood as the property that any attempt to distinguish encoded quantum states causes a disturbance in the signal. As a result, implementation of a QKD protocol involves an estimation of the experimental parameters influenced by the eavesdropper's intervention, which is achieved by randomly sampling the signal. If the estimation of many parameters with high precision is required, the portion of the signal that is sacrificed increases, thus decreasing the efficiency of the protocol. Here we propose a QKD protocol based on an entirely different principle. The sender encodes a bit sequence onto non-orthogonal quantum states and the receiver randomly dictates how a single bit should be calculated from the sequence. The eavesdropper, who is unable to learn the whole of the sequence, cannot guess the bit value correctly. An achievable rate of secure key distribution is calculated by considering complementary choices between quantum measurements of two conjugate observables. We found that a practical implementation using a laser pulse train achieves a key rate comparable to a decoy-state QKD protocol, an often-used technique for lasers. It also has a better tolerance of bit errors and of finite-sized-key effects. We anticipate that this finding will give new insight into how the probabilistic nature of quantum mechanics can be related to secure communication, and will facilitate the simple and efficient use of conventional lasers for QKD.

Uplink non-orthogonal multiple access for 5G wireless networks

Abstract: Orthogonal Frequency Division Multiple Access (OFDMA) as well as other orthogonal multiple access techniques fail to achieve the system capacity limit in the uplink due to the exclusivity in resource allocation. This issue is more prominent when fairness among the users is considered in the system. Current Non-Orthogonal Multiple Access (NOMA) techniques introduce redundancy by coding/spreading to facilitate the users' signals separation at the receiver, which degrade the system spectral efficiency. Hence, in order to achieve higher capacity, more efficient NOMA schemes need to be developed. In this paper, we propose a NOMA scheme for uplink that removes the resource allocation exclusivity and allows more than one user to share the same subcarrier without any coding/spreading redundancy. Joint processing is implemented at the receiver to detect the users' signals. However, to control the receiver complexity, an upper limit on the number of users per subcarrier needs to be imposed. In addition, a novel subcarrier and power allocation algorithm is proposed for the new NOMA scheme that maximizes the users' sum-rate. The link-level performance evaluation has shown that the proposed scheme achieves bit error rate close to the single-user case. Numerical results show that the proposed NOMA scheme can significantly improve the system performance in terms of spectral efficiency and fairness comparing to OFDMA.

A Vector Approach for the Analysis and Synthesis of Directional Modulation Transmitters

Abstract: In order to formalize and extend on previous ad-hoc analysis and synthesis methods a theoretical treatment using vector representations of directional modulation (DM) systems is introduced and used to achieve DM transmitter characteristics. An orthogonal vector approach is proposed which allows the artificial orthogonal noise concept derived from information theory to be brought to bear on DM analysis and synthesis. The orthogonal vector method is validated and discussed via bit error rate (BER) simulations.

Relay Selection for Two-Way Full Duplex Relay Networks With Amplify-and-Forward Protocol

Abstract: The full duplex (FD) technique, which allows the communication node to transmit and receive signals over the same frequency band simultaneously, has the potential to double the spectral efficiency in comparison with the traditional half duplex (HD) technique. However, self-interference, leaking from the FD node's transmission to its own reception, has the detrimental impact on the performance of FD communication. In this paper, we analyze and optimize the two-way FD relay system using amplify-and-forward protocol, when the multi-relay scenario is considered. The optimal relay selection scheme in maximizing the effective signal-to-interference and noise ratio is proposed, which significantly improves the system performance than a single relay network. Furthermore, to facilitate the comparisons with the traditional two-way HD relay, the analytical expressions of the two-way FD relay are derived in a closed form, including bit error rate (BER), ergodic capacity, and outage probability. Based on the analytical expressions, the optimal power allocation and the optimal choice of duplex mode, i.e., FD and HD, are obtained by minimizing the outage probability. Monte-Carlo simulations are fulfilled to verify the analytical expressions. The results reveal that the residual self-interference after interference suppression limits the performance of two-way FD relay: when the residual interference is small, the FD mode has lower BER/outage probability and higher ergodic capacity since it utilizes the resources effectively; otherwise, the HD mode achieves lower BER/outage probability and higher ergodic capacity since it can completely cancel the self-interference at the cost of lower resource utilization.

Performance of Full-Duplex AF Relaying in the Presence of Residual Self-Interference

Abstract: This paper investigates the error and diversity performances of full-duplex (FD) amplify-and-forward (AF) singlerelay systems under the effect of residual self-interference. The variance of this interference is assumed to be proportional to the λ-th power of the transmitted power (0 ≤ λ ≤ 1). The study considers the cooperative linear relaying protocol with direct source-destination link and the dual-hop scheme without direct link, both under uncoded and coded frameworks. At first, closed-form pairwise error probability expressions are derived for the uncoded systems, which are then used to obtain tight bounds to the bit error rate (BER) of the coded systems. To shed an insight on the diversity behavior, asymptotic expressions at high transmission powers are also presented. Different from previous works that treat the direct link as interference, this paper shows that FD linear relaying systems with a suitable precoder can attain the same diversity function as their half-duplex (HD) counterparts. However, further analysis shows that HD orthogonal AF using a superposition constellation is asymptotically optimal in terms of maximum coding gain. In addition, it is shown that the diversity of FD dual-hop systems is a decreasing function of λ and is equal to zero when λ = 1. Although HD relaying is asymptotically optimal under the considered protocols and interference model, illustrative results show that FD relaying is advantageous at practical BER levels when λ is sufficiently small.

Adaptive OFDM Modulation for Underwater Acoustic Communications: Design Considerations and Experimental Results

Abstract: In this paper, we explore design aspects of adaptive modulation based on orthogonal frequency-division multiplexing (OFDM) for underwater acoustic (UWA) communications, and study its performance using real-time at-sea experiments. Our design criterion is to maximize the system throughput under a target average bit error rate (BER). We consider two different schemes based on the level of adaptivity: in the first scheme, only the modulation levels are adjusted while the power is allocated uniformly across the subcarriers, whereas in the second scheme, both the modulation levels and the power are adjusted adaptively. For both schemes we linearly predict the channel one travel time ahead so as to improve the performance in the presence of a long propagation delay. The system design assumes a feedback link from the receiver that is exploited in two forms: one that conveys the modulation alphabet and quantized power levels to be used for each subcarrier, and the other that conveys a quantized estimate of the sparse channel impulse response. The second approach is shown to be advantageous, as it requires significantly fewer feedback bits for the same system throughput. The effectiveness of the proposed adaptive schemes is demonstrated using computer simulations, real channel measurements recorded in shallow water off the western coast of Kauai, HI, USA, in June 2008, and real-time at-sea experiments conducted at the same location in July 2011. We note that this is the first paper that presents adaptive modulation results for UWA links with real-time at-sea experiments.

Practical Switching-Based Hybrid FSO/RF Transmission and Its Performance Analysis

Abstract: Hybrid free-space optical (FSO)/radio-frequency (RF) systems have emerged as a promising solution for high-data-rate wireless backhaul. We present and analyze a switching-based transmission scheme for the hybrid FSO/RF system. Specifically, either the FSO or RF link will be active at a certain time instance, with the FSO link enjoying a higher priority. We considered both a single-threshold case and a dual-threshold case for FSO link operation. Analytical expressions have been obtained for the outage probability, average bit error rate, and ergodic capacity for the resulting system. Numerical examples are presented to compare the performance of the hybrid scheme with the FSO-only scenario.

Channel Hardening-Exploiting Message Passing (CHEMP) Receiver in Large-Scale MIMO Systems

Abstract: In this paper, we propose a multiple-input multiple-output (MIMO) receiver algorithm that exploits channel hardening that occurs in large MIMO channels. Channel hardening refers to the phenomenon where the off-diagonal terms of the H H H matrix become increasingly weaker compared to the diagonal terms as the size of the channel gain matrix H increases. Specifically, we propose a message passing detection (MPD) algorithm which works with the real-valued matched filtered received vector (whose signal term becomes H T Hx, where x is the transmitted vector), and uses a Gaussian approximation on the off-diagonal terms of the H T H matrix. We also propose a simple estimation scheme which directly obtains an estimate of H T H (instead of an estimate of H), which is used as an effective channel estimate in the MPD algorithm. We refer to this receiver as the channel hardening-exploiting message passing (CHEMP) receiver. The proposed CHEMP receiver achieves very good performance in large-scale MIMO systems (e.g., in systems with 16 to 128 uplink users and 128 base station antennas). For the considered large MIMO settings, the complexity of the proposed MPD algorithm is almost the same as or less than that of the minimum mean square error (MMSE) detection. This is because the MPD algorithm does not need a matrix inversion. It also achieves a significantly better performance compared to MMSE and other message passing detection algorithms using MMSE estimate of H. Further, we design optimized irregular low density parity check (LDPC) codes specific to the considered large MIMO channel and the CHEMP receiver through EXIT chart matching. The LDPC codes thus obtained achieve improved coded bit error rate performance compared to off-the-shelf irregular LDPC codes.

Pilot-Assisted PAPR Reduction Technique for Optical OFDM Communication Systems

Abstract: This paper investigates the use of a pilot signal in reducing the electrical peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) intensity-modulated optical wireless communication system. The phase of the pilot signal is chosen based on the selected mapping (SLM) algorithm while the maximum likelihood criterion is used to estimate the pilot signal at the receiver. Bit error rate (BER) performance of the pilot-assisted optical OFDM system is identical to that of the basic optical OFDM (with no pilot and no PAPR reduction technique implemented) at the desired BER of less than 10-3 needed to establish a reliable communication link. The pilot-assisted PAPR reduction technique results in higher reduction in PAPR for high order constellations than the classical SLM. With respect to a basic OFDM system, with no pilot and no PAPR reduction technique implemented, a pilot-assisted M-QAM optical OFDM system is capable of reducing the electrical PAPR by over about 2.5 dB at a modest complementary cumulative distribution function (CCDF) point of 10-4 for M = 64. Greater reductions in PAPR are possible at lower values of CCDF with no degradation to the system's error performance. Clipping the time domain signal at both ends mildly (at 25 times the signal variance level) results in a PAPR reduction of about 6.3 dB at the same CCDF of 10-4 but with an error floor of about 3 ×10-5. Although it is possible to attain any desired level of electrical PAPR reduction with signal clipping, this will be at a cost of deterioration in the systems's bit error performance.

Directional Modulation Based on 4-D Antenna Arrays

Abstract: Four-dimensional (4-D) antenna arrays are formed by introducing a fourth dimension, time, into traditional antenna arrays. In this paper, a time-modulated 4-D array with constant instantaneous directivity is proposed for directional modulation. The main idea is that the 4-D array transmits correct signal without time modulation in the desired direction, while transmitting time-modulated signals in other directions. As longs as the time modulation frequency is less than the bandwidth of the transmitted signal, the time-modulated signals cannot be demodulated correctly due to the aliasing effect, implying that time-modulated signals go distorted. Thus, the 4-D array can be used to transmit direction-dependent signals in secure wireless communications. The proposed idea is verified by experiments based on AM signal transmission through the 4-D array. Moreover, BPSK signal transmission through the 4-D array is studied and the bit error rate (BER) performance is investigated. Simulation results show that the BERs of time-modulated BPSK (TM-BPSK) signals transmitted through the sidelobes of the 4-D array are much higher than those of BPSK signals and almost keep unchanged even under higher SNR. Finally, two enhanced methods are presented to improve the feasibility of directional modulation by using random time sequences and random time modulation frequency.

Experimental Demonstration of 50-Mb/s Visible Light Communications Using 4 $\,\times\,$ 4 MIMO

Abstract: This letter reports the experimental demonstration of an indoor visible light nonimaging multiple-input multiple-output system with an aggregate error free bit rate of 50 Mb/s over a distance of 2 m. The system uses four independent white LED transmitters, each transmitting 12.5 Mb/s of data in the ON-OFF keying nonreturn zero format, and four independent nonimaging optical receivers. The performance of four detection methods ranging from the basic channel inversion to the more advanced space time techniques is compared experimentally. The results gathered demonstrate that the simplest technique is capable of the same bit error rate as the most complex scheme. The system also provides full illumination with a mean level of 350 Lux satisfying the ISO lighting standards for home and office environments.

Hybrid asymmetrically clipped OFDM-based IM/DD optical wireless system

Abstract: In this paper, we present a hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (OFDM) system. This system uses a combination of asymmetrically clipped optical OFDM (ACO-OFDM) and pulse amplitude modulated discrete multitone (PAM-DMT) techniques, which can be used in intensity modulated direct detection (IM/DD) optical wireless (OW) systems. In this hybrid scheme, ACO-OFDM and PAM-DMT signals are transmitted together. Clipping noise is estimated at the receiver and canceled to recover the PAM-DMT symbols. This scheme does not require any DC bias for transmission, which makes the transmitter less complex and very power efficient. With this system, we can increase the data rate of the ACO-OFDM system by almost twice. In addition, no bandwidth penalty is incurred. Extensive computer simulations show that the bit-error rate (BER) performance of ACO-OFDM in the additive white Gaussian noise environment is not affected by any kind of interference, but only due to half of the available transmit power, we see a 3 dB degradation. However, the BER performance of PAM-DMT shows some degradation at low signal-to-noise ratio (SNR) but is identical to the conventional scheme at higher SNR. We also see a slight improvement in peak-to-average power ratio (PAPR) of the output combined signal. Therefore, advantages such as increased data rate, DC-bias elimination, no bandwidth, and PAPR penalty make this scheme very attractive for OW systems using IM/DD.

On-demand spectrum and core allocation for reducing crosstalk in multicore fibers in elastic optical networks

Abstract: In the past few years, many researchers have studied elastic optical networks, which exhibit a dramatically improved transmission capacity compared with conventional optical networks. However, the transmission capacity per fiber will soon reach the physical limit for traditional single-mode fibers. Multicore fiber (MCF) is among the innovative fibers based on space-division multiplexing technology. MCF has multiple cores and achieves a far larger transmission capacity than traditional single-mode fibers. However, signals transmitted in these crowded multiple cores interfere with each other and are degraded. This degradation has a serious impact on the network resource management in elastic optical networks. Previous research indicates that the crosstalk effect of MCF is dependent on an arrangement of signals regarding the spectrum and core. Therefore, we approach the problem of the crosstalk in MCF with regard to the spectrum and core allocation, from the network perspective. First, this paper summarizes the related work regarding elastic optical networks and MCFs. Next, we propose an “on-demand” spectrum and core allocation method that reduces both the crosstalk and fragmentation in elastic optical networks with MCFs. This proposed method is based on two predefined policies related to the crosstalk and fragmentation. The first, the core prioritization policy, is based on the MCF's structure, and the other is a core classification policy based on the required bandwidth of the connections. The core prioritization policy realizes the core allocation that reduces crosstalk by avoiding filling adjacent cores. The core classification policy reduces the spectrum fragmentation by allocating a uniform bandwidth connection for each core. Finally, we evaluate the proposed method using computer simulations. The results indicate that the proposed method can, under various network conditions, improve both the crosstalk and blocking probability of the total network through our two policies.

0.34-THz Wireless Link Based on High-Order Modulation for Future Wireless Local Area Network Applications

Abstract: This paper presents a 0.34-THz wireless link for future wireless local area networks (WLANs), which is based on high order 16-quadrature amplitude modulation (16QAM). The system adopts super heterodyne transceivers and parallel digital signal-processing techniques. The 0.34-THz transceiver consists of a 0.34-THz subharmonic mixer, a 0.34-THz waveguide H-ladder bandpass filter, and a 0.17-THz multiplier chain. Two 0.34-THz Cassegrain antennas with 48.4-dBi gain have been developed to extend the transmission distance. Based on a 32-way parallel signal processing, we have successfully realized the 3-Gb/s, 16QAM real-time modulator and demodulator. The measured data indicate that the lowest bit error rate of the 0.34-THz, 3-Gb/s data link is 1.784×10-10 over a 50.0-m line-of-sight channel. The maximum received energy per bit to noise power spectral density ratio ( Eb/N0) is 23.8 dB, while the output power of transmitter is -17.5 dBm and the noise temperature of receiver is 5227 K. In addition, this paper presents a 0.34-THz WLAN prototype based on IEEE 802.11b/g protocol. The WLAN prototype, which consists of an access point and two terminal nodes, achieves a transmission data rate of 6.536 Mb/s over 1.15 m by using rectangular horn antennas.

End-to-End Energy Modeling and Analysis of Long-Haul Coherent Transmission Systems

Abstract: In this paper, we model and analyze the end-to-end energy consumption of 100-Gbps coherent long-haul transmission systems. In particular, we investigate the impact of forward error correction (FEC) on the end-to-end energy consumption. We compare the energy efficiency of commonly used modulation formats in 100-Gbps transmission, namely dual polarization-quadrature phase-shift-keying (DP-QPSK) and dual polarization-16-quadrature amplitude modulation (DP-16-QAM), for different transmission distance and input bit error rate. Our energy model includes consumption of transmitter, booster, link amplifier as well as receiver. Compared with previous digital signal processing models, we provide a very detailed model that not only includes all the significant functional blocks (such as timing and carrier recovery, chromatic and polarization mode dispersion compensation, and FEC), but also takes into account impact of the number of samples processed every clock cycle and of operations other than multiplications. We have found that receiver energy consumption dominates in transmission systems that use electronic dispersion compensation over long transmission distances. Our results show that for short transmission distances where hard-decision decoding is adequate for both modulation formats, DP-16-QAM is more energy efficient than DP-QPSK. However, as the transmission distance increases, the energy saving due to the low symbol rate of DP-16-QAM is offset by the energy consumption of soft-decision decoding. In this case, the two modulation formats have approximately similar energy consumption.

An Enhanced Color Shift Keying Modulation Scheme for High-Speed Wireless Visible Light Communications

Abstract: This paper presents a new color shift keying (CSK) modulation format for wireless visible light communication (VLC), based on four colors instead of the three colors used in the existing IEEE 802.15.7 CSK physical layer standard. The new four color system uses a novel intensity modulation and direct detection approach to realize a four-dimensional signaling scheme that uses the available color and signal spaces efficiently. The bit error rate evaluation of both the existing and proposed system shows that the new four color scheme achieves a significant 4.4-dB electrical SNR gain over the three color scheme for an additive white Gaussian noise channel. The performance of existing and proposed CSK systems is examined over a range of dispersive optical wireless channels including the channel crosstalk and insertion losses, which reveals that the four color CSK scheme is more power efficient and reliable than the three color scheme for a particular amount of delay spread that the optical wireless channel may have.

Joint Approximately Sparse Channel Estimation and Data Detection in OFDM Systems Using Sparse Bayesian Learning

Abstract: It is well known that the impulse response of a wideband wireless channel is approximately sparse, in the sense that it has a small number of significant components relative to the channel delay spread. In this paper, we consider the estimation of the unknown channel coefficients and its support in OFDM systems using a sparse Bayesian learning (SBL) framework for exact inference. In a quasi-static, block-fading scenario, we employ the SBL algorithm for channel estimation and propose a joint SBL (J-SBL) and a low-complexity recursive J-SBL algorithm for joint channel estimation and data detection. In a time-varying scenario, we use a first-order autoregressive model for the wireless channel and propose a novel, recursive, low-complexity Kalman filtering-based SBL (KSBL) algorithm for channel estimation. We generalize the KSBL algorithm to obtain the recursive joint KSBL algorithm that performs joint channel estimation and data detection. Our algorithms can efficiently recover a group of approximately sparse vectors even when the measurement matrix is partially unknown due to the presence of unknown data symbols. Moreover, the algorithms can fully exploit the correlation structure in the multiple measurements. Monte Carlo simulations illustrate the efficacy of the proposed techniques in terms of the mean-square error and bit error rate performance.

Constellation Shaping for Fiber-Optic Channels With QAM and High Spectral Efficiency

Abstract: In this letter, the fiber-optic communication channel with a quadrature amplitude modulation (QAM) input constellation is treated. Using probabilistic shaping, we show that high-order QAM constellations can achieve and slightly exceed the lower bound on the channel capacity, set by ring constellations. We then propose a mapping function for turbo-coded bit-interleaved coded modulation based on optimization of the mutual information between the channel input and output. Using this mapping, spectral efficiency as high as 6.5 bits/s/Hz/polarization is achieved on a simulated single channel long-haul fiber-optical link excluding the pilot overhead, used for synchronization, and taking into account frequency and phase mismatch impairments, as well as laser phase noise and analog-to-digital conversion quantization impairments. The simulations suggest that major improvements can be expected in the achievable rates of optical networks with high-order QAM.

Successive interference cancelation amenable multiple access (SAMA) for future wireless communications

Abstract: In this work, we introduce a novel multiple access scheme which is based on the joint design of the system signature matrix at the transmitter and the successive interference cancelation (SIC) based detector at the receiver. The symbols of the different users are judiciously spread in the frequency (space) domain, which can be effectively exploited by the SIC based technique, such as the iterative message-passing algorithm (MPA), to cancel the multi-user interference as well as to obtain diversity gain. Numerical results show that the non-orthogonal system based on the proposed successive interference cancelation amenable multiple access (SAMA) paradigm employing the iterative MPA achieves significant performances gain over the orthogonal one for the same spectral efficiency with affordable complexity.

Multi-Branch Tomlinson-Harashima Precoding Design for MU-MIMO Systems: Theory and Algorithms

Abstract: Tomlinson-Harashima precoding (THP) is a nonlinear processing technique employed at the transmit side which is a dual to the successive interference cancelation (SIC) detection at the receive side. Like SIC detection, the performance of THP strongly depends on the ordering of the precoded symbols. The optimal ordering algorithm, however, is impractical for multiuser MIMO (MU-MIMO) systems with multiple receive antennas due to the fact that the users are geographically distributed. In this paper, we propose a multi-branch THP (MB-THP) scheme and algorithms that employ multiple transmit processing and ordering strategies along with a selection scheme to mitigate interference in MU-MIMO systems. Two types of multi-branch THP (MB-THP) structures are proposed. The first one employs a decentralized strategy with diagonal weighted filters at the receivers of the users and the second uses a diagonal weighted filter at the transmitter. The MB-MMSE-THP algorithms are also derived based on an extended system model with the aid of an LQ decomposition, which is much simpler compared to the conventional MMSE-THP algorithms. Simulation results show that a better bit error rate (BER) performance can be achieved by the proposed MB-MMSE-THP precoder with a small computational complexity increase.

Generalized codebook design method for limited feedback systems

Abstract: In a closed-loop wireless communication system, a codebook-based feedback mechanism is provided where each codeword indicates a particular profile to be used to provide a target performance measure (e.g., bit error rate or spectral efficiency) for the transmission channel. This may be accomplished by using a multi-stage quantization process to construct the codewords as a plurality of transmission parameters specifying a MIMO transmission scheme, precoding vector or matrix, power allocation in space/time/frequency, modulation and channel code.

On the Closed-Form Performance Analysis of Maximal Ratio Combining in Shadowed-Rician Fading LMS Channels

Abstract: In this paper, the maximal ratio combining (MRC) scheme in Shadowed-Rician (SR) fading land mobile satellite (LMS) channels is studied. The MRC scheme for SR fading LMS channels has been studied in existing literature; however, most of the existing analytical results are in the form of infinite power series, which are not in closed-form. In this paper, we derive approximate closed-form expressions of the probability density function and cumulative distribution function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels. Then we provide approximate closed-form expressions of the bit error rate (BER), outage probability, and capacity of the considered scheme. One of the derived closed-form BER expressions is found useful for obtaining the analytical diversity order and coding gain of the considered MRC scheme.

Influence of pulse shaping on bit error rate performance and out of band radiation of Generalized Frequency Division Multiplexing

Abstract: Generalized Frequency Division Multiplexing (GFDM) is a multicarrier transmission scheme that offers flexible pulse shaping of individual subcarriers. The application of pulse shaping per subcarrier can control the out of band (OOB) radiation and create non-orthogonal waveforms. In this paper, the influence of the pulse shaping to the overall system performance, namely bit error rate (BER) over AWGN channels and OOB radiation, is investigated. Closed from expressions for the BER and power spectral density (PSD) of GFDM are derived. Simulation results show that GFDM reduces the OOB radiation by 46dB compared to OFDM, while at the same time, the OFDM BER can be achieved when using the Dirichlet pulse filter. In case some self-interference is allowed, the OOB radiation can be reduced even more, which is a key aspect for cognitive radio (CR) applications.

A Tight Upper Bound on Bit Error Rate of Joint OFDM and Multi-Carrier Index Keying

Abstract: This letter investigates performance enhancement by the concept of multi-carrier index keying in orthogonal frequency division multiplexing (OFDM) systems. For the performance evaluation, a tight closed-form approximation of the bit error rate (BER) is derived introducing the expression for the number of bit errors occurring in both the index domain and the complex domain, in the presence of both imperfect and perfect detection of active multi-carrier indices. The accuracy of the derived BER results for various cases are validated using simulations, which can provide accuracy within 1 dB at favorable channels.

An Optimal Data Collection Technique for Improved Utility in UAS-aided Networks

Abstract: Recent technological advances in electronics, sen- sors, and communications devices have facilitated the prolifer- ation of Unmanned Aircraft System (UAS)-aided applications. However, the UAS-aided communications networks are yet to receive sufficient research endeavor. In this paper, we address one of the most important research challenges pertaining to UAS-aided networks comprising adaptive modulation-capable nodes, namely how to fairly maximize the energy efficiency (throughput per energy). For the mobility pattern innate to the UAS, we demonstrate how the adaptive modulation behaves. Furthermore, we formulate the problem as a potential game that is played between the UAS and the network-nodes, and prove its stability, optimality, and convergence. Based upon the potential game, a data collection method is envisioned to maximize the energy efficiency with the fairness constraint. Additionally, we analyze the Price of Anarchy (PoA) of our proposed game. Extensive simulations exhibit the effectiveness of our proposal under varying environments. sensor nodes require only capabilities to communicate with the CHs. The mobility pattern of the UAS causes the distance between a CH and the UAS to vary. The distance between the CH and the UAS affects the Signal-to-Noise Ratio (SNR), which in turn affects the Bit Error Rate (BER) of the CH transmissions. Both SNR and BER affect the modulation scheme. This is because modulation schemes that transmit more bits per symbol require higher values of SNR for a given BER requirement (9). Moreover, if high levels of BER are acceptable, the achievable number of bits per symbol that a modulation scheme transmits can be increased.

A 100-Gb/s Multiple-Input Multiple-Output Visible Laser Light Communication System

Abstract: A 100-Gb/s multiple-input multiple-output (MIMO) visible laser light communication (VLLC) system employing vertical-cavity surface-emitting lasers with 16-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) modulating signals is proposed and experimentally demonstrated. The transmission capacity of systems is significantly increased by space-division-multiplexing scheme. With the aid of low-noise amplifier and equalizer at the receiving site, good bit error rate performance and clear constellation map are obtained for each optical channel. A system of eight 16-QAM-OFDM channels over 5-m free-space links with a total data rate of 100 Gb/s (12.5 Gb/s/channel × 8 channels) is successfully achieved. Such a proposed MIMO VLLC system is shown to be a prominent one not only presents its convenience in free-space optical communication, but also reveals its potential for the real implementation.

An efficient reliable PUF-based cryptographic key generator in 65nm CMOS

Abstract: Physical unclonable functions (PUFs) are primitives that generate high-entropy, tamper resistant bits for use in secure systems. For applications such as cryptographic key generation, the PUF response bits must be highly reliable, consistent across multiple evaluations under voltage and temperature variations. Conventionally, error correcting codes (ECC) have been used to improve response reliability, but these techniques have significant area, power, and delay overheads and are vulnerable to information leakage. In this work, we present a highly-reliable, PUF-based, cryptographic key generator that uses no ECC, but instead uses built-in self-test to determine which PUF bits are reliable and only uses those bits for key generation. We implemented a prototype of the key generator in a 65nm bulk CMOS testchip. The key generator generates 1213 bits in an area of <;50k/μm2 with a measured bit error rate of <; 5 * 10-9 in both the nominal and worst case corners (100k measurements each). This is equivalent to a 128-bit key failure rate of <; 10-6. The system can generate a 128-bit key in 1.15μs. Finally, we present a realization of a “strong”-PUF that uses 128 of these highly reliable bits in conjunction with an Advanced Encryption Standard (AES) cryptographic primitive and has a response time of 40ns and is realized in an area of 84k/μm2.

Performance Analysis of Relay-Assisted All-Optical FSO Networks Over Strong Atmospheric Turbulence Channels With Pointing Errors

Abstract: In this study, we consider a relay-assisted free-space optical communication scheme over strong atmospheric turbulence channels with misalignment-induced pointing errors. The links from the source to the destination are assumed to be all-optical links. Assuming a variable gain relay with amplify-and-forward protocol, the electrical signal at the source is forwarded to the destination with the help of this relay through all-optical links. More specifically, we first present a cumulative density function (CDF) analysis for the end-to-end signal-to-noise ratio. Based on this CDF, the outage probability, bit-error rate, and average capacity of our proposed system are derived. Results show that the system diversity order is related to the minimum value of the channel parameters.

Digital Preemphasis in Optical Communication Systems: On the DAC Requirements for Terabit Transmission Applications

Abstract: Next-generation coherent optical systems are geared to employ high-speed digital-to-analog converters (DAC), allowing for digital preprocessing of the signal and flexible optical transport networks. However, one of the major obstacles in such architectures is the limited resolution (less than 5.5 effective bits) and –3 dB bandwidth of commercial DACs, typically limited to half of the currently commercial baud rates, and even relatively reduced in case of higher baud rate transponders (400 Gb/s and 1 Tb/s). In this paper, we propose a simple digital preemphasis (DPE) algorithm to compensate for DAC-induced signal distortions, and exhaustively investigate the impact of DAC specifications on system performance, both with and without DPE. As an outcome, performance improvements are established across various DAC hardware requirements (effective number of bits and bandwidth) and channel baud rates, for m-state quadrature amplitude modulation (QAM) formats. In particular, we show that lower order modulation formats are least affected by DAC limitations, however, they benefit the most from DPE in extremely challenging hardware conditions. On the contrary, higher order formats are severely limited by DAC distortions, and moderately benefit from DPE across a wide range of DAC specifications. Moreover, effective number of bit requirements are established for m-state QAM, assuming low and high baud rate transmission regimes. Finally, we discuss the application scenarios for the proposed DPE in next-generation terabit transmission systems, and establish maximum transportable baud rates, which are shown to be used toward increasing channel baud rates to reduce terabit subcarrier count or toward increasing forward error correction (FEC) overheads to reduce the pre-FEC bit error rate threshold. Maximum baud rates after DPE are summarized here for polarization multiplexed BPSK, QPSK, 8QAM, and 16QAM, assuming two DACs: Current commercial DACs (5.5 effective bits, 16 GHz bandwidth) 57, 54, 51, and 48 Gbaud, respectively. Next-generation DACs (7 effective bits, 22 GHz bandwidth): 62, 61, 60, and 58 Gbaud, respectively.