Digital Signal Processing for Dual-Polarization Intensity and Interpolarization Phase Modulation Formats Using Stokes Detection

A polarisation-division-multiplexing (PDM)-based four-level pulse amplitude modulation (PAM4) fibre-free-space optical (FSO) convergent system with optical band-pass filters (OBPFs) for polarisation de-multiplexing is feasibly demonstrated for the first time. In a PDM scenario with PAM4 modulation, the transmission capacity of fibre-FSO convergent systems is enhanced four times with an aggregate channel capacity of 128 Gb/s (64 Gb/s PAM4/polarisation × 2 polarisations). With an OBPF, polarisation-tracking free de-multiplexing is attained by eliminating other optical carrier with orthogonal polarisation. An OBPF is a simple polarisation de-multiplexing scheme in which the polarisation-orthogonal carrier can be effectively de-multiplexed and the cross-polarisation interference can be nearly eliminated. Compared with traditional PDM-based fibre-FSO convergent systems with sophisticated polarisation-tracking mechanism and elaborate digital signal processing (DSP) approach, it reveals a noteworthy one with the advantage of simplicity. Through 25 km single-mode fibre transport and 500 m FSO link, sufficiently low bit error rate and qualified PAM4 eye diagrams are attained. This proposed polarisation-tracking free PDM-based fibre-FSO convergent system is notable because it not only incorporates the fibre backbone and optical wireless feeder, but it also simplifies the framework since complicated polarisation-tracking mechanism and DSP approach are not involved.

Multi-carrier code division multiple access (MC-CDMA)has been considered as a strong candidate for next generation wireless communication system due to its excellent performance in multi-path fading channel and simple receiver structure. However, like all the multi-carrier transmission technologies such as OFDM, the inter-carrier interference (ICI) produced by the frequency offset between the transmitter and receiver local oscillators or by Doppler shift due to high mobility causes significant BER (bit error rate) performance degradation in MC-CDMA system. Many ICI cancellation methods such as windowing and frequency domain coding have been proposed in the literature to cancel ICI and improve the BER performance for multi-carrier transmission technologies. However, existing ICI cancellation methods do not cancel ICI entirely and the BER performance after ICI cancellation is still much worse than the BER performance of original system without ICI. Moreover, popular ICI cancellation methods like ICI self-cancellation reduce ICI at the price of lowering the transmission rate and reducing the bandwidth efficiency. Other frequency-domain coding methods do not reduce the data rate, but produce less reduction in ICI as well. In this paper, we propose a novel ICI cancellation scheme that can eliminate the ICI entirely and offer a MC-CDMA mobile system with the same BER performance of a MC-CDMA system without ICI. More importantly, the proposed ICI cancellation scheme (namely Total ICI Cancellation) does not lower the transmission rate or reduce the bandwidth efficiency. Specifically, by exploiting frequency offset quantization, the proposed scheme takes advantage of the orthogonality of the ICI matrix and offers perfect ICI cancellation and significant BER improvement at linearly growing cost. Simulation results in AWGN channel and multi-path fading channel confirm the excellent performance of the proposed Total ICI Cancellation scheme in the presence of frequency offset or time variations in the channel, outperforming existing ICI cancellation methods.

An Iterative Detection and Decoding (IDD) scheme in a high-order Multiple-Input Multiple-Output (MIMO) wireless communication system requires a heavy computational complexity for an outstanding Bit Error Rate (BER) performance in a given Signal-to-Noise Ratio (SNR) environment. A new computational complexity reducing IDD scheme designed with optimum parameters is proposed in this paper to guarantee Quality of Service (QoS) without the loss of BER performance. There are three parameters to control the trade-off between computational complexity and BER performance of an IDD scheme: a candidate list size of Dynamic List Sphere Detector (D-LSD), a number of intra-iteration of Turbo decoder, and a number of IDD iteration. A complexity reduction of about 70 % is demonstrated in this study, when the target BER is around 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(-4)</sup> at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =7dB in the case of a 4 x 4 MIMO system with 16-ary Quadrature Amplitude Modulation (QAM).

– This paper analyses the performance of Multiple Input Multiple Output (MIMO) wireless communication system by combining it with an efficient algorithm Diagonal Reduction (DR). DR is a powerful tool to achieve more efficiently a high performance with less complexity. This paper proposes a DR algorithm in order to reduce its complexity named Greedy Diagonal Reduction (GDR) algorithm which gives reduced complexity with efficient performance at the receiver using the MATLAB communication tool box version 7.0 as a simulation tool. From the simulation results of various reduction algorithms it is observed that, DR can reduce the number of iterations using size reduction operations. Proposed DR algorithm gives identical Bit Error Rate (BER) performance with LLL algorithms when applied to Successive Interference cancellation (SIC) decoding. Greedy DR reduces the computational complexity in Multiple Input Multiple Output systems by improving the efficiency in terms of size reduction operations. Sphere Decoding (SD) technique gives better BER performance on comparing with Successive Interference cancellation decoding technique.

End-to-end learning of a communications system using the deep learning-based autoencoder concept has drawn interest in recent research due to its simplicity, flexibility and its potential of adapting to complex channel models and practical system imperfections. In this paper, we have compared the bit error rate (BER) performance of autoencoder based systems and conventional channel coded systems with convolutional coding (CC), in order to understand the potential of deep learning-based systems as alternatives to conventional systems. From the simulations, autoencoder implementation was observed to have a better BER in 0-5 dB E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> range than its equivalent half-rate convolutional coded BPSK with hard decision decoding, and to have only less than 1 dB gap at a BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> . Furthermore, we have also proposed a novel low complexity autoencoder architecture to implement end-to-end learning of coded systems in which we have shown better BER performance than the baseline implementation. The newly proposed low complexity autoencoder was capable of achieving a better BER performance than half-rate 16-QAM with hard decision decoding over the full 0-10 dB E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> range and a better BER performance than the soft decision decoding in 0-4 dB E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> range.

This paper focuses on the bit error rate (BER) performance of intelligent transportation communication system under multipath mobile frequency-selective channels. After presenting the theoretical BER performance formula of single carrier frequency domain equalization (SC-FDE) in the form of double integral, a closed-form approximate upper bound of BER performance was derived，as well as specific analytical expressions for approximate BER performance bounds under typical modulations. Analysis and simulation show that the derived approximate BER bound highly approaches the theoretical one. The bound also indicates that the research about the preferable equalization methods is still necessary.

In free space optical (FSO) communication systems, atmospheric turbulence is the major cause of bit error rate (BER) performance degradation. The error performance of the system can be significantly improved with the help of spatial diversity by employing multiple transmit or receive apertures. However, correlation of channels under turbulence in the case of small separation between transmit apertures can substantially reduce the benefits of spatial diversity. Still, a thorough analysis of the system performance in terms of diversity order and coding gain for the FSO multiple-input single-output (MISO) system under turbulence influenced correlated channels has not been studied when the repetition coding is used to achieve improved BER performance. In this paper, we provide unique results of the BER performance analysis of the considered correlated FSO-MISO system over Gamma–Gamma distributed turbulence channel. Using the joint moment generating function of received signal-to-noise ratio (SNR), a novel generalized approximate BER expression is derived, followed by convergence test of the power series based BER expression using the Cauchy's ratio test. Then, an asymptotic analysis at high SNR is performed to obtain a novel closed-form expression for BER of FSO-MISO system. We also derive expressions for coding gain, diversity gain, and coding gain loss due to correlation in channels. Although the effect of correlation in channels on the BER performance of the system is analyzed under different scenarios, while it is observed that it does not affect the diversity order; it significantly degrades the coding gain of the considered system.

The optical ZCZ code, which is a set of pairs of binary and biphase sequences with zero correlation zone, can provide code division multiple access (CDMA) communication system without co-channel interference. The M-ary amplitude shift keying spread spectrum (M-ary/ASK-SS) system using this code can detect a desired sequence without interference of undesired sequences. We have proposed the compact construction of a matched filter bank for this code, which is called the compact-type matched filter bank. However, M-ary/ASK-SS system using this filter bank might go down the bit error rate (BER) performance because input-output characteristics of this filter bank for this code with zero correlation zone 4n - 2 are nonlinear characteristics. In this paper, we clarify that BER performance in the M-ary/ASK-SS system over the additive white Gaussian noise (AWGN) channels is not influenced by nonlinear characteristics of this filter bank by the theoretical formula of BER characteristics and the computer simulation. The BER performance in the ASK-SS system using compact-type matched filter under the AWGN environment go down compared to that using direct-type matched filter as expected. But the BER performance in the M-ary/ASK-SS system using this compact-type matched filter bank under the AWGN environment is almost equal compared to that using parallel-type matched filter bank. In fact, this compact-type matched filter bank is effective in the M-ary/ASK-SS system.

This paper seeks to determine the Bit Error Rates (BER) performance for feasible free space optical communication (FSOC) deployment in Namibian and South African atmospheric weather conditions. In order to achieve this objective, the Pulse Position Modulation (PPM) based BER performance model was invoked to compute various BER values in selected towns of both countries. The results showed that in winter season, BER values were generally lower than in summer season. A comparative analysis for various towns with the lowest and the highest scintillation in both countries showed that BER increases rapidly as photon count increases in towns with high scintillation index values. The BER values realized from this study could be used to simulate internet traffic QoS advantages of the FSOC links when compared to the RF technology networks. The study outcomes are likely to benefit operators, industry, regulators, governments, and researchers in understanding feasible areas of FSOC deployment in both countries.

Space-time block code (STBC) based on orthogonal design is one of the space-time coding methods to achieve multi-input multi-output (MIMO) diversity gain. STBC can provide sufficient space diversity gain, but it can not provide coding gain. Polar codes based on channel polarization are the first class of provably capacity-achieving codes with low encoding and decoding complexity. In order to improve the bit error rate (BER) performance of STBC, a concatenated scheme with Polar codes and STBC, named Polar-STBC scheme, is proposed in this paper. The BER performance of Polar-STBC system is discussed by numerical simulation under different polar code length, different polar code rates, and different coding methods of STBC. The results show that the performance of Polar-STBC has a big improvement in comparison with that using STBC only. The coding gain of Polar-STBC system is about 5dB when the BER is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Meanwhile, the longer code length and the lower code rate Polar codes have, the better BER performance the Polar-STBC system has. In addition, the different STBC coding methods have influence on the Polar-STBC system. The Polar-STBC system with more receiving antennas has a better BER performance in comparison with those with the same sending antennas and less receiving antennas. The coding gain of Polar-STBC system with 2 receiving antenna is 6.5dB improvement to the system with 1 receiving antenna when BER is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and the code length is 1024.

This paper presents a bit error rate (BER) performance analysis of vehicular communication systems (VCS) based on the IEEE 802.11p standard assuming velocity variations of the mobile stations (MSs). To that end, we propose a novel Monte Carlo vehicle-to-vehicle (V2V) fading channel simulator that takes into account the accelerated motion and trajectory variations of the MSs. On the grounds of the proposed channel simulator, we assess the impact of the MSs' velocity variations on the system's BER performance. We assume that the channel state information is obtained following the least-squares (LS) channel estimation techniques that are commonly implemented in commercial off-the-shelf WiFi devices. The results show that the velocity variations have in general a slight impact on the system's BER performance. However, the performance is aggravated as the data frame length or the relative speed increases. The simulation framework presented in this paper can be used as a benchmark to evaluate the performance of the emerging VCS in safety critical scenarios.

Aa analytical approach is presented for modeling crosstalk and to evaluate the bit error rate (BER) performance in a wavelength division-multiplexing (WDM) network for link with optical cross connect (OXC) without wavelength converter. Factors that affect the magnitude of crosstalk in the OXC are investigated and parameters that play important role in determining magnitude of crosstalk and BER are identified. The effects of OXC induced crosstalk on the BER performance is evaluated at a bit rate of 10 Gb/s by optimizing different parameters.

Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can significantly improve the downlink bit error rate (BER) performance of DS-CDMA in a frequency-selective fading channel. However, the uplink BER performance degrades due to a strong multi-user interference (MUI). We have proposed frequency-interleaved single-carrier spread spectrum multi-access (SC-SSMA) with MMSE-FDE, in which the subcarrier components of each user's signal are interleaved onto a wider bandwidth. Since frequency-interleaving patterns assigned to different users are orthogonal to each other, frequency-interleaved SC-SSMA can avoid the MUI completely while achieving frequency diversity gain with MMSE-FDE. In this paper, transmit/receive antenna diversity is applied to frequency-interleaved SC-SSMA with MMSE-FDE to further improve the BER performance. Its conditional BER is derived for the given set of channel gains. The average BER performance is numerically evaluated using the derived conditional BER and is confirmed by computer simulation.

Generalized frequency division multiplexing (GFDM) and circular filter bank multicarrier (C-FBMC) are two contender waveforms with circular pulse-shaping that are recently proposed for the physical layer of the fifth generation of wireless communication networks (5G). This paper puts these waveforms under the microscope and conducts an analysis on their practical feasibility and performance. In addition, we present a transmitter structure for both GFDM and C-FBMC and show that this structure has the same complexity for both systems. In this paper, GFDM receiver with successive interference cancellation (SIC) is considered as it can get a performance close to that of OFDM (orthogonal frequency division multiplexing). Our bit error rate (BER) performance analysis reveals that GFDM has limitations in terms of the total number of symbols per data packet. When the number of symbols in a packet has an even value, GFDM suffers from a high error floor in BER. For the small constellation sizes, GFDM and C-FBMC reach the same BER performance as that of OFDM. As the constellation size increases, a gap between the BER curve of GFDM and OFDM starts to appear while C-FBMC keeps the same performance as OFDM. Finally, our computational complexity analysis reveals that C-FBMC receiver is simpler than GFDM.

We discuss the bit error rate (BER) performance of asynchronous baseband DS/SSMA systems using line coded M sequences. As the line codes, we adopt FM family codes that provide M sequences with the DC free spectrum and good correlation properties. It has been already reported that some combinations of three FM coded M sequences provide a better cross-correlation property than that of the preferred pairs of noncoded M sequences. Since their quantitative evaluation in terms of the BER performance improvement due to the line coding has not been done yet, we considered it in this paper. We first derive an equation for the BER analysis, then compare the BER performance of the FM coded M sequences with that of the noncoded M sequences in two bandwidth limited channels, a band pass and a power line channel. In our scenario, the improvement of the required E/sub b//N/sub 0/ is 1 dB and 3 dB, respectively. Furthermore we propose a system using FM coded M sequences of different periods simultaneously. This proposed system of the different periods can achieve the channel efficiency 4/3 times better than a system using noncoded M sequences of the same period, while the required E/sub b//N/sub 0/ of both systems is almost the same.