Efficient bit-error-rate estimation of multicarrier transceivers

Multicarrier modulation schemes are widely used in several digital telecommunication systems, such as Asymmetric Digital Subscriber Lines (ADSL) and Wireless Local Area Network (WLAN) based on Orthogonal Frequency Domain Multiplexing (OFDM). An estimate of the Bit-Error-Rate (BER) degradation due to non-idealities in the transceiver (e.g. nonlinear distortions in the analog front-ends, digital clipping,...) is much more complicated in a multicarrier system than in a single-carrier system due to the large number of carriers and the huge number of possible transmitted symbols. This paper proposes a method for estimating the BER of such OFDM modulation schemes in a CPU time that is two orders of magnitude smaller than a Monte-Carlo method, as confirmed by simulations on a 5 GHz IEEE 802.11 WLAN receiver front-end.

ADSL (Asymmetric Digital Subscriber Line) adopts modulation scheme called DMT (Discrete multi tone), a multi carrier system. The process of allocating bits into various sub-channels is called bit-loading. In this paper, a new bit-loading algorithm that reduces the power required to transmit data is proposed. Comparison on power cut back with other algorithms is presented. Also the implementation of the algorithm in the transmitter is discussed. A Matlab simulation model has been developed to simulate ADSL transmitter (with bit-loading), channel and receiver. The ADSL system with bit-loading algorithm is also implemented in hardware using TT's DSK6713 kit and comparison of software and hardware results are tabulated.

The requirement for an automated test system has immensely increased due to the realization that manual testing is associated with additional resources and staffing constraints. In order to achieve a competitive edge, reduced development cost, timely product delivery, and product quality are mandatory in today's organization. Manual testing requires skilled operators that increase cost, time, and product delivery. The low cost computer based automated system helps to get an edge by fulfilling these organizational demands. In this paper, an automated testing system has been developed to support functional testing of Nortel Network's modem system (1-Meg SUT). The modem is an inherently complex asymmetric digital subscriber line (ADSL) product and its testing is far more complex than just verification of process faults. The complexity of ADSL system renders automated test system an important and imperative part of ADSL testing. The subject paper demonstrates the indispensable need of automated test system for ADSL testing and its advantages in providing a competitive edge for the organization.

In this paper the general ADSL (asymmetric digital subscriber line) noise environment is reviewed in the context of the telephone loop plant. Special attention is given to the unique unidirectional transmission nature of ADSL. A set of noise environments is presented for related computer simulation studies and hardware tests. A set of mid-CSA test loops is also proposed for performance evaluation under conditions of T1 NEXT interference. To simplify calibration procedures, noise and loop models are revealed in FIR (finite impulse response) filter form and can be measured in dB loss or dBm/Hz power density terms. A subchannel signal to noise ratio (SNR) based computer simulation method is then used to estimate potential ADSL performance under different noise environments for different serving areas. >

Recently, an efficient error performance scheme named as labeling diversity has been proposed in the literature for wireless local area network (WLAN). This paper proposes labeling diversity for 8-phase shift keying (8-PSK) modulation named as boosted space-time scheme. A pair of labeling map is opted for this scheme by maximizing the utility function in asymptotic coding gain under the supposition of error-free feedback. Furthermore, labeling diversity is employed with the space-time forward error correction (FEC) codes like convolution and turbo codes for point to point communication scenarios. Since non-line of sight (NLOS) point to point communication scenario is assumed therefore Rayleigh distributed channel model is selected which remains constant for single space-time block code (STBC). The STBC used in boosted space-time scheme is non-orthogonal therefore maximum likelihood (ML) soft de-mapper is employed at the receiver. The convergence of iterative decoding between soft de-mapper and decoder is analyzed by the extrinsic information transfer (EXIT) chart. The validity of the convergence of iterative decoding is also verified by Monte Carlo simulation. It is evident from the simulation results that bit error rate (BER) performance of boosted space-time scheme is superior to the conventional spacetime scheme under identical conditions. Moreover, the boosted space-time scheme with convolution code performs better for low signal-to-noise ratio (SNR) regime in comparison to boosted space-time scheme with turbo code. However, for high SNR regime, turbo coding scheme outperforms the convolution scheme. In addition, turbo coding scheme provides better BER performance to the convolution scheme under non-iterative decoding.

Smart metering utility network (SUN) is an emerging wireless technology for achieving intelligent control and information transfer in smart grid applications. However, the operation of SUNs on unlicensed bands is very sensitive to external interferences generated from other networks working on the same spectrum bands, such as wireless local area networks (WLANs). This paper aims to analyze packet error rate (PER) performance of a victim SUN receiver under the interferences of one or more WLAN transmitting nodes. To deal with a scenario leveraged by multiple random variables, such as offset between desired SUN data packet and WLAN packet, duration of WLAN data packet, and time interval between two consecutive WLAN packets, we propose a segmented packet collision model with the help of the probability theory. We first divide all the packets into small segments and then calculate the collision probability of each segment to acquire a more accurate bit error rate (BER). Then, based on different BERs in distinct segments of the desired SUN packet, average PER of the victim SUN receiver is obtained. Finally, the proposed analytical model is validated by simulations as an effort to evaluate PER performance of a SUN receiver under the WLAN interferences.

Multicarrier modulation (MCM) schemes have been intensively studied and developed, because of their numerous advantages, which include high data rate and immunity to multipath fading. Among MCM schemes, filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has attracted considerable interest in recent years. However, the FBMC-OQAM system exhibits a high peak-to-average power ratio (PAPR). In this paper, we investigate the FBMC-OQAM system and present a solution for the problem of high PAPR that involves two separate components: minimizing the PAPR of each data block and optimizing each segment based on the preceding result. Unlike conventional partial transmit sequence techniques, the new method uses fewer combinations of phase factors, thereby decreasing the complexity of the algorithm while still reducing PAPR. In addition, sparse clipping signals are recovered by compressed sensing, and the bit error rates were analyzed based on sparsity level. The reductions in PAPR were also numerically evaluated using simulations. The simulation results confirm that the proposed technique effectively reduces the high peaks in the FBMC-OQAM system.

This paper presents the design and implementation of novel decimation filter structure for high speed asymmetric digital subscriber line (ADSL). Existing ADSL circuits use comb-FIR-FIR decimation filter structures, which have low throughput, more hardware and high power consumption. Unlike existing ADSL circuits, we design a novel high speed filter architecture and implement it using the minimal signed digit (MSD) representation. The MSD representation is suitable for common subexpression elimination, and it significantly reduces the number of adders required for the filter synthesis. Each digital-filter structure is simulated using Matlab, and its complete architecture is captured using DSP Blockset and Simulink. The resulting filter architecture has higher throughput, less hardware and consumes less power than the comb-FIR-FIR and comb-IIR-FIR architectures. The filter has been implemented on Xilinx FPGA using Virtex-2 technology. Compared to the comb-FIR-FIR and the comb-IIR-FIR architectures, the designed decimation filter architecture contributes to a hardware saving of 82% and 74%, respectively; in addition, it reduces the power dissipation by 91% and 79%, respectively.

Multi-carrier code division multiple access (MC-CDMA), a novel, high capacity, multicarrier modulation scheme, is developing to a key radio transmission technology for future wireless local area networks (W-LANs). However in ad hoc code division multiple access (CDMA) networks near-far effects can block a receiver due to high interference. These effects occur when a receiving station is closer to an interferer than to its corresponding transmitter. Accordingly, the receiver cannot detect the intended signal out of the received one and the data transmission fails. In this work, we present an adaptive medium access control (MAC) protocol for ad hoc MC-CDMA based W-LANs, based on the IEEE 802.11 MAC protocol. The new protocol has the ability to overcome the near-far-problem by employing a frequency adaptation method. The key of the proposed method is an interference estimate built at each receiving mobile station (MS). Aided by its estimate, a MS can calculate whether the quality of service (QoS) expectations of the incoming link can be accomplished. If the interference is too high, the receiving MS initiates a frequency channel change and informs the corresponding transmitter over the control packets about the Id of the new channel. It is shown that this concept can deploy the high capacity characteristics of MC-CDMA in wireless environments

As an extension and complement of the terrestrial network, the space information network has attracted extensive attention and is expected to play a significant role in the human society. In this article, we introduce an architecture of the space information network and summarize the key technical issues in the satellite-ground transmission. Then, we present traditional modulation schemes that highly affect the performance of the satellite-ground transmission and analyze their shortcomings which limit the development of space information networks. As an urgent and necessary mission to deal with the above shortcomings and promote the transmission performance of space information networks, new multicarrier modulation based satellite-ground transmission schemes are proposed in this article. We compare new multicarrier modulation schemes with traditional modulation schemes for satellite-ground transmission in detail, and conduct simulations to verify the superiority of new multicarrier modulation schemes. Finally, possible future research directions are identified.

The ripple modulation (RM) is a technique that provides a variable output voltage by using the output voltage ripple of a switching-mode power converter. It was proposed to reproduce the communication signal of a visible light communication transmitter, thus avoiding the use of power inefficient linear power amplifiers. However, the RM has a major drawback: it has not been reported how to reproduce multicarrier modulation (MCM) schemes, which are the preferred modulation schemes due to their high performance in wireless communications. In this paper, it is demonstrated that the RM can be used to reproduce MCM schemes by considering the envelope and the instantaneous phase of the communication signal. Moreover, the control system of the power stage is described in detail, explaining how to modulate both the width and the phase of the gate signals, the calculation of the phase shift that is required for tracking the envelope, etc.

Multidimensional TCM schemes can be used to improve the performance of the asymmetrical digital subscriber line (ADSL). The operating principle of how M-D (multidimensional) TCM works in an ADSL channel is analysed and criteria for evaluating and choosing effective multidimensional TCM schemes are described. The results of a simulation for evaluating the performance is presented.

The purpose of the paper is to describe a model that has been developed to predict the undesired coupled voltage at the network interface of the customer premises, caused by an ambient electric field incident on the drop wire. The model considered the effects of ground reflection, angle of incidence of the incoming wave on the plane of the drop wire, and the coupling caused by common-mode induced voltage due to network unbalance. The model has been simulated and verified in experiments at Bellcore's Chester facilities. The predicted results have also been compared with the measurements taken during surveys in different parts of the country that measured the coupled voltages at the network interface caused by high-power transmitters (that is, LORAN-C). The measured results show good agreement with those predicted by the model. The model is used to study electromagnetic interference at the asymmetric digital subscriber line (ADSL) transceiver caused by coupled voltage at the customer premises. >

Echo cancellation technique enables full duplex transmission using the same transmission band and thereby increases the aggregate data throughput of a channel. This tutorial paper introduces high speed echo cancellation for Full Rate (ITU-T Recommendation G.992.1) and Splitterless (ITU-T Recommendation G.992.2, aliased G.Lite) ADSL Transceivers. Symmetric and multirate Asymmetric echo cancellation Transceiver structures based completely on time domain or frequency domain as well as both time and frequency domain echo cancellation have been analyzed using different algorithms for performance and computational complexity. Combined Time and Frequency Domain Echo Cancellation (TAFDEC) structure with the so called DMT algorithm appears to be most suitable to achieve lower complexity with better performance as compared to echo cancellation in either time or frequency domain using LMS algorithm.

The discrete multitone (DMT) modulation/demodulation scheme is the standard transmission technique in the application of asymmetric digital subscriber lines (ADSL) and very-high-speed digital subsc...