Bit Synchronization and Delayed Decision Feedback Equalization for EDGE BTS - Hardware Implementation on TMS320C6424 TI DSP

Compared to wired channels, time dispersive radio channels possess more frequent nulls in their spectral characteristics. Thus, the performance of linear filters to compensate intersymbol interference degrades dramatically. The well-known nonlinear decision feedback equalizer (DFE) is one approach to improve this behavior. However, in systems with observations of high dimensionality, the optimum DFE structure is computational intensive. In this paper, we apply the method of the multi-stage Wiener filter (MSWF) to a conventional minimum mean square error (MMSE) DFE in order to reduce computational complexity. The application of the new algorithm to an Enhanced Data rates for GSM Evolution (EDGE) system demonstrates the ability to outperform the even more computational intensive linear Wiener filter (WF).

By dividing the available spectrum into multiple bands, multi-band ultra-wideband (UWB) systems possess many advantages, such as the flexibility to eliminate possible interference and coexistence problems with available wireless standards. UWB channels have large delay spread, causing inter- symbol interference (ISI) in high rate systems. The RAKE receiver is often used to capture multipath energy, but it is incapable of ISI compensation, causing severe bit error rate (BER) degradation in practical UWB channels. This paper proposes an over-sampling multi-channel equalizer per sub-band for multi-band UWB. The performance of the proposed receiver is compared with the RAKE receiver through analytical and simulation studies. The proposed equalizer has been shown to be able to handle ISI under any channel conditions or data rate presented, with an acceptable BER. In addition, the rich multipath diversity of the UWB channels is harnessed by the over-sampling scheme, for output SNR improvement. one. Therefore, equalization receiver based on adaptive algorithms seems to be an effective way to recover the transmitted data. With this consideration, we propose an over-sampling multi-channel equalizer per sub-band for a multi-band UWB system, which provides more effective inter-symbol interference (ISI) suppression compared with the conventional RAKE receiver when operating in channels with large delay spread. Through detailed theoretical analysis and extensive simulations, we are able to show that the proposed 4-arm equalizer scheme is superior to a 4-arm conventional RAKE receiver in the presence of ISI at all signal-to-noise ratios (SNRs). Based on the method presented in (4), the simulated performance is shown to conform to analytical predictions. The RAKE receiver is incapable of ISI compensation, and a moderate level of ISI is shown to cause severe bit error rate (BER) degradation. The proposed over-sampling equalizer, on the other hand, is able to handle ISI under any channel conditions or data rate, with an acceptable BER. Over- sampling is shown to be able to achieve diversity gain, and improves the output SNR.

This paper addresses the problem of low complexity iterative channel equalization in intersymbol interference channels using 8PSK modulation. In this paper, we apply a recently proposed low complexity iterative channel equalization technique, called the iterative decision feedback equalizer (IDFE) to a coded system using 8PSK modulation. In this system, the structure of the DFE has been modified to incorporate soft a priori information from previous iterations of the channel decoder in detection of the corrupted signal. As a result, in this algorithm complexity is only a linear function of channel memory length. Simulation results show that this technique, using a convolutional code with constraint length K=3 and interleaver size N=3000 over a known time invariant ISI channel achieves a remarkable gain of about 5 dB compared to the conventional DFE. Complexity evaluation also shows that the iterative DFE has advantages in terms of complexity compared to other types of turbo equalization techniques and is an appropriate candidate for EDGE (Enhanced Data rates for GSM Evolution) systems.

To enable a higher transmission rate in optical camera communication (OCC) systems, severe inter-symbol interference (ISI) occurs owing to the reduction of the number of pixel-row-per-bit (PPB). Therefore, those pixels representing data bit 0 or 1 may have same gray scale values, significantly deteriorating the bit decision when using the conventional thresholding scheme. In this Letter, a simple yet efficient scheme, referred to as nearest neighbor bit assisted decision (NNBAD) scheme, is proposed and experimentally demonstrated for signal decision in OCC systems. NNBAD leverages the nearest neighbor bit to jointly assist bit decision for pixels with severe ISI. Experimental results show that, for OCC systems with on-off keying (OOK) modulation, those pixels with severe ISI cannot be distinguished by the conventional thresholding scheme. Yet, the NNBAD scheme exhibits strong robustness against ISI, remarkably improving the bit error rate (BER) performance. The proposed scheme can achieve a throughput of 8.2 kbps with OOK modulation under an illuminance of 600 lx.

This paper presents analytical results of the effects of jitter and inter symbol interference (ISI) on a millimeter-wave impulse radio (IR) transceiver, compared with performance of the developed 10-Gb/s W-band IR transmitter prototype. The compact and cost-effective IR transmitter consists of a pulse generator (PG) that creates a short pulse with a duration of <10 ps, a band-pass filter (BPF) that shapes the short pulse to the desired millimeter-wave pulse (wavelet), and a power amplifier (PA) which is deployed as an option. Jitters of the PG and ISI from the BPF are a great issue to make the IR transceiver robust and to obtain excellent performance. One analysis verified that, thanks to a novel retiming architecture, the random jitter and the data dependent jitter from the PG give only a small penalty of <0.5-dB increase in signal to noise ratio (SNR) for achieving a bit error rate (BER) of <10−12. The alternative analysis on the effect of ISI from the BPF indicated that using a Gaussian BPF enables transmission with a BER of <10−12 up to a data rate of 1.4 times as large as a bandwidth of the BPF, whereas the ISI analysis suggested that mismatching of the skirt characteristics of the developed BPF to those of a Gaussian BPF causes tail lobes following the wavelet, resulting in an on/off ratio of <15 dB and hence an SNR penalty of <6 dB.

Intersymbol Interference (ISI) is one of the major bottlenecks in Molecular Communication via Diffusion (MCvD) systems resulting in degraded system performance. This paper first introduces two new families of linear channel codes to minimize the effect of ISI: linear Zero Pad Zero Start (ZPZS) and linear Zero Pad (ZP) codes, ensuring that every codeword is devoid of consecutive bit-1s. Subsequently, the ZPZS linear and ZP linear codes are combined to form a binary ZP code, aiming for a higher code rate compared to the linear ZP codes, which can be decoded with a simple Majority Location Rule (MLR) algorithm. Additionally, a linear Leading One Zero Pad (LOZP) code is proposed, which relaxes the zero padding constraints considering the placement of bit-1s in the codeword as an important metric to have an improved code rate than the ZP code. Finally, a closed-form expression is deduced to compute the expected ISI for the proposed codes and to demonstrate that the expected ISI is a function of the average bit-1 density of the codewords in a code. To compare the ISI and BER performance with average bit-1 density of the proposed codes, two types of MCvD channel are considered: (i) channel without refresh, where the previously transmitted bits persist for a longer duration and (ii) channel with refresh, where the channel is cleared after each successful reception of the message. The ISI comparison, across different sequence distributions for a given length and weight, shows that the linear LOZP code exhibits superior resilience against ISI in a channel with refresh due to the placement of bit-1s at the initial positions, whereas the ZP code performs better in channel without refresh by reducing the average bit-1 density of the code. The asymptotic upper bound of the code rate is derived for the proposed codes, which depicts that a trade-off exists between the ISI and code rate. The simulation results show that the proposed family of ZP and linear LOZP codes can improve the Bit Error Rate (BER) performance by controlling the bit-1 locations and the average bit-1 density of the code, specifically where the ISI is more pronounced over the channel noise, thus providing a better reliability compared to the conventional error correcting codes at different data rate regimes.

The paper considers the problem of constructing adaptive minimum bit error rate (MBER) neural network equalisers for binary signalling. Motivated from a kernel density estimation of the bit error rate (BER) as a smooth function of training data, a stochastic gradient algorithm called the least bit error rate (LBER) is developed for adaptive nonlinear equalisers. This LBER algorithm is applied to adaptive training of a radial basis function (RBF) equaliser in a channel intersymbol interference (ISI) plus co-channel interference setting. A simulation study shows that the proposed algorithm has good convergence speed, and a small-size RBF equaliser trained by the LBER can closely approximate the performance of the optimal Bayesian equaliser. The results also demonstrate that the standard adaptive algorithm, the least mean square (LMS), performs poorly for neural network equalisers because the minimum mean square error (MMSE) is clearly suboptimal in the equalisation setting.

The Multi user Multi Carrier Direct sequencing Code Division Multiple Access (MU-MC-DS-CDMA) strategy was developed in response to rising demand for system capacity, higher data rates, and multimedia services. It's essentially a combination of CDMA and OFDM schemes. As a result, MC-CDMA takes the advantages of both CDMA and OFDM technologies. CDMA improves bandwidth consumption performance, whereas OFDM helps to minimize Inter Symbol Interference (ISI) and multipath fading. This dissertation suggests a method for evaluating the performance of multi user MC-DS-CDMA system. BER and PAPR are used to evaluate the results. The Bit Error Rate (BER) output of the proposed method is then examined using MATLAB for various modulation techniques. By using Walsh-Hadamard (W-H) code is used because it eliminates Multiple Access Interference (MAI). In terms of BER, it can be shown that BPSK performs better than QPSK. Key Words: AWGN, BER, ISI, MC-CDMA, Rayleigh Fading Channel, SNR, QPSK, MAI

One of the most relevant themes of wireless communication is to achieve better spectral efficiency and provide high reliability while providing rich-content data services despite the existence of several serious challenges. A few of them are multipath fading, multi-user interference, co-channel interference (CCI), inter symbol interference (ISI) etc to name a few. Several techniques have already been developed and deployed to eliminate the fading effects. One of the less explored techniques which have been adopted and discussed in this chapter is based on the structure of the transmitting antenna. The physical dimension of the antenna is varied as per the fading condition by adopting a dynamic process which adjusts the structure to provide the best quality of service (QoS). Two types of antenna set-ups are considered - Single Input-Single Output (SISO) and Multiple Input-Multiple Output (MIMO). The transmitting antenna in this system adaptively updates its aperture to improve the system performance and at the same time optimizes the driving power of the antenna as per requirement. The system changes the effective aperture of the transmitting antenna in high data rate, time varying Rayleigh channels to adapt to a previously set Bit error Rate (BER). However, in a real time environment the BER keeps on changing based on the channel condition. It is difficult to attain a fixed value of BER and hence even more difficult to model the antenna structure for a single time instant. As a result there exist a number of effective aperture dimensions for various BER in a single time instant. Out of the various values, two specific limits of the effective aperture of the transmitting antenna needs to be decided. Fuzzy C-Mean (FCM) Clustering method being one of the most popular and efficient clustering technique is used to set two limits of the aperture within which a particular threshold of the BER is obtained at one particular instant of time. The results derived show the effectiveness of the entire system.

The 4G up-gradation was essential because of the exponential increment of the wireless applications. So, 5G was introduced with large capacity, small latency, improved reliability, high data rate, and better quality of services (QoS). 4G uses orthogonal frequency-division multiplexing (OFDM) which has a decent quality of long-distance communication, by eliminating intersymbol interference (ISI) and improving the signal-to-noise ratio (SNR), but it has a spectrum wastage problem. However, the improved data rate is possible by spectrum utilization. 5G adopted various techniques for the better utilization of spectrum in current scenarios. The new generation waveforms, i.e., filtered orthogonal frequency-division multiplexing (F-OFDM), generalized frequency-division multiplexing (GFDM), universal filtered multicarrier (UFMC), and filter bank multicarrier (FBMC), are one of them. This paper will discuss FBMC which is the alternative technology of OFDM with better features by building subcarrier waveform based on prototype filters. Here, FBMC is investigated in terms of BER (bit error rate) by varying several parameters such as the size of inverse fast Fourier transforms/fast Fourier transform (IFFT/FFT), length of guard band, and length of symbols. Results of simulation will show that the bit error rate (BER) of FBMC is not affected by the variation of symbol length, while advancement in the size of IFFT/FFT increases BER, on the given parameter while the BER reduces for large size of the guard band of each subcarrier.KeywordsFilter Bank MulticarrierIFFT/FFTOffset QAMOrthogonal Frequency-Division MultiplexingBit Error Rate

The growth of modern wireless communications has increased the demand for high quality data services. This article presents an analysis of the performance of a DVB-S2 system with MIMO technology. A method for using a receiver-transmitter based on DVB-S2 with MIMO technology, provides a better quality of service for data transmission and discusses ways to improve the quality of data transmission using size and type converters of transmitting and receiving data, an amplifier and a normalizer Gain. The circuit was examined for bit error rate (BER) and peak signal-to-noise ratio (PSNR) between AWGN and multipath Rayleigh fading images operating under intersymbol interference (ISI). The analysis was carried out and a graph of the influence of ISI was obtained. The proposed system has the best quality of service for data transmission for fading channels. The transmission of images in the system includes a Rayleigh channel and AWGN with different values of the signal-to-noise ratio (SNR, dB) and different values of Gain. The Gain values change the BER and PSNR values (7.834 dB, 8.385 dB, and inf) at an SNR of -58 dB with respect to Gain values of 1, 32400 and 648000, respectively. Also obtained eye diagrams, where you can see a decrease in the negative impact of intersymbol interference with an increase in the value of Gain..This system can be used to wirelessly transmit higher quality, high-resolution radiological images (such as computed tomography or magnetic resonance imaging) over a wireless network to remote healthcare workers.

Multicarrier transmission techniques like multicarrier code division multiple access (MC-CDMA) is the strongest contender for the future generation wireless networks which is supposed to cater to the need of very high data rate with mobility and at the same time combat multipath and intersymbol interference in a spectrally efficient manner. To enhance the spectral efficiency further, some form of adaptive modulation is being proposed (Wasantha et al. (2002)). In this paper, first of all, we simulate the performance of various single-h continuous phase modulation (CPM) schemes in an MC-CDMA system by varying the two CPM parameters - size of symbol alphabet (M) and modulation index (h). The parameter sets considered are {M=2, h=0.5}, {M=2, h=0.875}, {M=4, h=0.5} and {M=4, h=0.875}. Simulation results show that the higher order modulation schemes (M=4) need better channel conditions than the lower order schemes (M=2) for a given bit error rate (BER). Moreover, as expected (Xiong (2000)), h=0.875 (approximate optimum value) gives a better BER performance than h=0.5 for a given BER. Based on these simulation results, we then design two adaptive modulation based systems, one considering h=0.5 and the other with h=0.875, each with M=2 and 4. Results of the adaptive systems clearly indicate that the adaptive switching of the modulation formats in each of these two systems increases the system capacity per given bandwidth (spectrum efficiency) effectively without sacrificing the expected BER performance. Also, it is seen that the adaptive system with h=0.875 is superior to the h=0. 5 system, both in terms of BER performance and the number of simultaneous users, but obviously at the cost of reduced bandwidth efficiency as higher the value of h, the higher bandwidth it requires.

Traditionally, channel generated bit error rates (BERs) at a certain signal to noise ratio (SNR) have been modeled by a Gaussian distribution function. This approach has been suitable for a peak detection channel as the analysis is performed in only one bit. In the case of a partial response maximum likelihood (PRML) channel, one data bit is determined by multiple code bits. There is a burst of errors detected if any one of the involved code bits gives an error. The chi-square distribution function, which is a sum of several independent Gaussian-squared distributions, is another method to model BERs of a PRML channel. Particularly, different PRML codes could be modeled by a chi-square distribution with different degrees of freedom. In this paper, the relationship of SNR to BER is generated using the chi-square method. The measured on-track rms SNR, read sensitivity function, and media magnetization are the input parameters. Old data and adjacent track interference are considered as random variables. At specified track pitch and read write misregistration, the probability distributions of these random variables are defined by the read sensitivity function and media magnetization. For a given interference, the off-track SNR is calculated. Error rate at a given interference is then derived from off-track SNR by using the SNR to BER relationship defined by a chi-square distribution. The BER at a specific track pitch and read–write misregistration is computed by integrating the error rate at a given interference with the probability distribution of the interference. This model describes the statistical nature of the BER in magnetoresistance head applications and provides very good correlation to experimental data.

Orthogonal frequency division multiplexing (OFDM) is a type of multicarrier modulation (MCM) technique in which larger bandwidth is divided into parallel narrow bands each of which is modulated by different subcarriers. All the subcarriers are orthogonal to each other and hence it reduces the interference among various subcarriers. OFDM technique is an efficient modulation technique used in certain wired and wireless application.In a wireless communication channel, the transmitted signal can travel from transmitter to receiver over multiple reflective paths. This results to multipath fading which causes fluctuations in amplitude, phase and angle of arrival of the received signal. For example, the signal which is transmitted from BTS (base transceiver station) may suffer multiple reflections from the buildings nearby, before reaching the mobile station. Such multipath fading channels are classified into slow fading/fast fading and frequency-selective/flat fading channels. This paper discusses the performance of OFDM system using various fading channels and channel coding. The parameter which is known as Bit error rate (BER) is calculated under different fading channels (AWGN, Rayleigh and Rician) for different digital modulation (BPSK, QPSK and QAM) and Channel coding (linear/Cyclic coding). Matlab Simulink tool is used to calculate the BER parameter.

Digital predistortion (DPD), based on complex-valued memory polynomials (MP), is established as an efficient method for power amplifier (PA) linearization. The DPD facilitates compliance of the telecommunication infrastructure to strict standard specifications (transmit spectrum mask (TSM), error vector magnitude (EVM), bit error rate (BER), [Formula: see text]) by making PA more linear, while at the same time reduces the running cost of the wireless infrastructure (at both Base Transceiver Station (BTS) and User Equipment (UE) sides) by making PA more power efficient. Even when DPD is utilized, signals with high peak-to-average power ratio (PAPR) produce out-of-band PA spectrum emission due to intermodulation products affecting all above-mentioned critical standard specified parameters. The novelty proposed in this paper is as follows. PA is restricted to operate within “reasonably above” PA linear region using PAPR reduction technique. The residual nonlinearity is taken care of by DPD. The combination of DPD and PAPR PA linearization methods is implemented on software-defined radio board. The necessary steps for efficient PA linearization are presented, compensating both out-of-band and in-band signal distortions. We achieved EVM = 2.0%, ACPR [Formula: see text]50[Formula: see text]dBc, at 10[Formula: see text]W LTE modulated PA output, antenna point and PA output power of 39.5[Formula: see text]dBm.