Transmitted Information Bits Research Articles

Medium Access Control and Rate Adaptation for Ultrasonic Intrabody Sensor Networks

The use of wirelessly internetworked miniaturized biomedical devices is promising a significant leap forward in medical treatment of many pervasive diseases. Recognizing the limitations of traditional radio-frequency wireless communications in interconnecting devices within the human body, in this paper, we propose for the first time to develop network protocols for implantable devices based on ultrasonic transmissions. We start off by assessing the theoretical feasibility of using ultrasonic waves in human tissues and by deriving an accurate channel model for ultrasonic intrabody communications. Then, we propose a new ultrasonic transmission and multiple access technique, which we refer to as Ultrasonic WideBand (UsWB). UsWB is based on the idea of transmitting information bits spread over very short pulses following a time-hopping pattern. The short impulse duration results in limited reflection and scattering effects, and the low duty cycle reduces the impact of thermal and mechanical effects, which may be detrimental for human health. We then develop a multiple access technique with distributed control to enable efficient simultaneous access by mutually interfering devices based on minimal and localized information exchange and on measurements at the receiver only. Finally, we demonstrate the performance of UsWB through a multiscale simulator that models the proposed communication system at the acoustic wave level, at the physical (bit) level, and at the network (packet) level. We also validate the simulation results by comparing them to experimental results obtained with a software-defined testbed.

A Low-Complexity ML Detection Algorithm for Spatial Modulation Systems With <inline-formula> <tex-math notation="TeX">$M$</tex-math></inline-formula>PSK Constellation

Spatial modulation (SM), which is a novel transmission scheme, is employed for active transmit antenna indexes and modulated signals to convey the information. To recover the transmitted information bits, the maximum likelihood (ML) joint detector is often used. However, its complexity linearly grows with the number of transmit antennas and the size of the signal set. A reduced-complexity ML optimal algorithm for SM systems with M-QAM has been proposed. However, for M-PSK modulation, there are not similar low-complexity ML detection algorithms yet to our knowledge. In this paper, a low-complexity ML detection algorithm for SM systems with M-PSK modulation is proposed. By exploiting the features of M-PSK constellation, we give the ML-estimated values of the transmitted symbols. Therefore, the ML search complexity is independent of the constellation size. Simulation results show that the proposed algorithm has the same performance as the ML-optimum detector and significant reduction in computational complexity compared with existing detectors for SM systems with M-PSK modulation.

DESIGN AND IMPLEMENTATION OF TURBO CODER FOR LTE ON FPGA

Recent wireless communication standards such as 3GPP-LTE, WiMax, DVB-SH and HSPA incorporates turbo code for its excellent performance. This work provides an overview of the novel class of channel codes referred to as turbo codes, which have been shown to be capable of performing close to the Shannon Limit. It starts with a brief discussion on turbo encoding, and then move on to describing the form of the iterative decoder most commonly used to decode turbo codes. Here, Turbo decoder uses original MAP algorithm instead of using the approximated Max log-MAP algorithm thereby it reduces the number iterations to decode the transmitted information bits. This paper presents the FPGA (Field Programmable Gate Array) implementation simulation results for Turbo encoder and decoder structure for 3GPP-LTE standard.

Cyclic redundancy check‐based detection algorithms for automatic identification system signals received by satellite

SUMMARYThis paper addresses the problem of demodulating signals transmitted in the automatic identification system. The main characteristics of such signals consist of two points: (i) they are modulated using a trellis‐coded modulation, more precisely a Gaussian minimum shift keying modulation; and (ii) they are submitted to a bit stuffing procedure, which makes more difficult the detection of the transmitted information bits. This paper presents several demodulation algorithms developed in different contexts: mono‐user and multi‐user transmissions, and known/unknown phase shift. The proposed receiver uses the cyclic redundancy check (CRC) present in the automatic identification system signals for error correction and not for error detection only. By using this CRC, a particular Viterbi algorithm, on the basis of a so‐called extended trellis, is developed. This trellis is defined by extended states composed of a trellis code state and a CRC state. Moreover, specific conditional transitions are defined to take into account the possible presence of stuffing bits. The algorithms proposed in the multi‐user scenario present a small increase of computation complexity with respect to the mono‐user algorithms. Some performance results are presented for several scenarios in the context of the automatic identification system and compared with those of existing techniques developed in similar scenarios. Copyright © 2013 John Wiley & Sons, Ltd.

Space shift keying with amplify‐and‐forward MIMO relaying

AbstractSpace shift keying (SSK) is a multiple‐input, multiple‐output system where the indices of the transmit antennas form the constellation symbols and no other data symbol is transmitted. In this paper, amplify‐and‐forward (AF) multiple‐input, multiple‐output relaying techniques with an SSK system are proposed and analysed. Single and multiple relays are located between the source and the destination and used to forward the transmitted messages from the source to the destination. Conventional AF relaying in which all relays amplify their received signal and forward it to the destination at specific time slot and opportunistic AF relaying where only the best relay is activated and all other relays are kept silent are considered. The receiver, with a single receive antenna, applies optimum detector to retrieve the transmitted information bits. Closed‐form bit error ratio expressions are provided for a source equipped with two transmit antennas. Additionally, a good approximate upper bound is derived for higher number of transmit antennas. The analytical results are validated through Monte Carlo simulation results. It is revealed that multiple relays can be considered to significantly enhance the performance of SSK system, and the diversity gain equals the number of existing relays. Copyright © 2013 John Wiley & Sons, Ltd.

Energy efficiency analysis of one-way and two-way relay systems

Relaying is supposed to be a low energy consumption technique since the long distance transmission is divided into several short distance transmissions. When the power consumptions (PCs) other than that consumed by transmitting information bits is taken into account, however, relaying may not be energy efficient. In this article, we study the energy efficiencies (EEs) of one-way relay transmission (OWRT) and two-way relay transmission (TWRT) by comparing with direct transmission (DT). We consider a system where two source nodes transmit to each other with the assistance of a half-duplex amplify-and-forward relay node. We first find the maximum EEs of DT, OWRT, and TWRT by optimizing the transmission time and the transmit powers at each node. Then we compare the maximum EEs of the three strategies, and analyze the impact of circuit PCs and data amount. Analytical and simulation results show that relaying is not always more energy efficient than DT. Moreover, TWRT is not always more energy efficient than OWRT, despite that it is more spectral efficient. The EE of TWRT is higher than those of DT and OWRT in symmetric systems where the circuit PCs at each node are identical and the numbers of bits to be transmitted in two directions are equal. In asymmetric systems, however, OWRT may provide higher EE than TWRT when the numbers of bits in two directions differ significantly.

Design And Implementation Of Error Correcting Codes For Transmission in Binary Symmetric Channel

Error Correcting codes are normally used for protecting transmitted information bits in a noisy channel. The information bits are encoded into error correcting codes which will be transmitted into the channel and on the receiver side, the received codes will be decoded back into the transmitted information bits. In this paper, a technique of generating binary error correcting codes that meet the Gilbert-bound and a simple encoding-decoding mechanism will be presented. To show the performance of the error correcting codes, a Binary Symmetric Channel is considered for transmission.

Performance Analysis of Space Shift Keying with Amplify and Forward Relaying

In this letter, dual-hop amplify and forward relaying using space shift keying (SSK) is introduced. In SSK, information bits are mapped into a spatial symbol. The spatial symbol is the index of the active transmit antenna, where a single antenna is activated at each time instance. The relay amplifies the data received from the transmitter and forwards it to the receiver without any further processing. The receiver applies optimum maximum-likelihood detector to retrieve the transmitted information bits. In particular, an exact closed-form expression for the average bit error probability is given for the case of two transmit antennas. In addition, an upper bound is derived for an arbitrary number of transmit antennas. The analytical results are validated through Monte Carlo simulation results.

Impact of FEC on different modulation formats in optical communication systems

The desire for higher per-fibre transport capacities and at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed transmission systems with higher spectral efficiencies. Among other enabling techniques that are used for the purpose, optical modulation formats with the application of some forward error correction techniques have become key to the design of modern optical transmission systems. In this paper we have analysed the optical communication system to evaluate the performance of different modulation formats with or without applying forward error correction techniques.

Advanced Optical Modulation Formats

Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically routed WDM networks. We discuss the generation and detection of multigigabit/s intensity- and phase-modulated formats, and highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multipath interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity

Further Results on Selection Combining of Binary NCFSK Signals in Rayleigh Fading Channels

In this paper, we provide an analytical performance comparison of various selection combining (SC) schemes for binary noncoherent frequency-shift keying (NCFSK) signals operating on independent and nonidentically distributed (i.n.d.) Rayleigh fading channels. With this motivation, we first derive the receiver structure for the optimum SC scheme, which combines one out of the available L diversity branches so as to minimize the probability of bit error. We show that the optimum SC scheme chooses the diversity branch having the largest magnitude of the logarithm of the a posteriori probability ratio (LAPPR) of the transmitted information bit. We also show that: 1) the optimum noncoherent diversity receiver, for binary NCFSK signals, is equivalent to combining the LAPPRs of all the diversity branches; 2) the SC scheme proposed by Neasmith and Beaulieu is a special case of the optimum SC scheme for independent and identically distributed (i.i.d.) Rayleigh fading; and 3) for i.n.d. fading with dual diversity (i.e., L=2), the performance of the optimum SC scheme is the same as that of the optimum noncoherent diversity receiver, whereas the Neasmith and Beaulieu SC scheme gives the performance of the suboptimum equal gain combining receiver. Bit-error rate (BER) results show that, at 10/sup -4/ BER, for i.i.d. Rayleigh fading, the proposed optimum SC scheme performs better than the existing SC schemes by 0.5-0.9 dB for L=3 and by 0.8-1.5 dB for L=5, and performs within 0.3 dB of the optimum noncoherent diversity receiver for L=3,5, and for i.n.d. Rayleigh fading with L=5, the optimum SC scheme gives an additional gain of about 2.0 dB over the Pierce SC scheme. Further, for i.i.d. Rayleigh fading, we derive the bit-error probability expression for a (3,L) selection scheme which combines three branches whose LAPPR magnitudes are the largest among the available L branches. Numerical results for this (3,L) selection scheme show that for L=5 at a BER of 10/sup -4/, combining the three branches with the largest LAPPR magnitudes yields almost the full performance of the optimum noncoherent diversity receiver, whereas, for L=7, it is just about 0.2 dB away from the latter.

Complexity analysis of multicarrier and single-carrier systems for very high-speed digital subscriber line

A complexity analysis of discrete multitone (DMT) and single-carrier modulation (SCM) in the context of a very high-speed digital subscriber line (VDSL) is presented in this paper. In addition to the traditional arithmetic complexity measures such as the number of multiply-and-accumulate (MAC) operations, we also compute the memory requirements. Furthermore, we normalize these metrics with respect to the number of information bits transmitted (rate normalized) and scale with respect to data path precision (precision scaled) in order to obtain more comprehensive metrics. The analysis shows that the number of MAC's per transmitted information bit (N/sub MACb/) for SCM is greater than that for DMT for all distances of interest in VDSL. The number of MACs per information bit and scaled with respect to precision (B/sub MAC/), i.e., NB/sub MACb/ = N/sub MACb/B/sub MAC/, was found to be clearly smaller for SCM in loops shorter than approximately 2 kft. This metric was found to be clearly smaller for DMT in loops longer than approximately 3.25 kft. At all lengths, DMT was found to have smaller memory requirements per information bit, as well as smaller precision-scaled memory requirements.

Multirate trellis coded modulation schemes in multimedia communications

Multirate multimedia information with different quality of service may be required at the same time in future communication systems. We propose a new class of trellis coded modulation (TCM) schemes, which can carry two different rates of multimedia information using only the same signal constellation. The transmitted information bit number per symbol in the proposed TCM is not an integer and is greater than that of the conventional TCM. An interesting character of the proposed multirate TCM is that it can provide different error protection for the two information rates. We also present the design criterion and the existence of noncatastrophic multirate TCM. Some theoretical and simulation results have shown that it can provide a certain coding gain compared with the corresponding uncoded modulation schemes.

Frequency-hopped multiple-access communication with nonorthogonal BFSK in Rayleigh fading channels

Nonorthogonal binary frequency-shift keying is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmitted information bits per unit time per unit bandwidth (called normalized throughput) is examined in Rayleigh fading channels. The tradeoff among tone spacing, code rate, and number of frequency slots in maximizing the normalized throughput is examined, keeping the total bandwidth fixed. The optimal tone spacing, code rate, and number of frequency slots in terms of the number of users and E~/sub b//N/sub 0/ is also discussed. The throughput gain attained by using the optimal tone spacing becomes more significant as the number of users is increased.

Optimal MFSK signalling for Reed-Solomon codedfrequency-hopped multiple-access communications

Frequency-hopped multiple-access communication systems employing Reed-Solomon (RS) coded M-ary FSK signalling is considered on a Rayleigh fading channel. The authors examine the optimal modulation alphabet size that maximises the average number of successfully transmitted information bits per dimension in connection with the channel traffic, the signal-to-noise ratio, and the required bit error probability.

Coherent homodyne optical communication receivers with photorefractive optical beam combiners

The principles of operation and the results of performance measurements are reported of a new type of coherent optical receiver that used a dynamic volume index of refraction grating formed inside a photorefractive material to coherently combine signal and local oscillator light prior to photodetection. Because the refractive index grating is formed by the interference pattern generated where mutually coherent optical beams overlap, the receiver can automatically adjust to changes in angle of arrival or optical wavefront profiles which occur on time scales longer than the grating formation time. The grating appears stationary to high-speed phase modulation imposed on the signal beam and coherently diffracts local oscillator light into the signal beam direction. Performance measurements are reported for a prototype system that used two independent Nd:YAG lasers at 1.064 /spl mu/m, an iron-doped indium phosphide photorefractive crystal, and a four-slot phase modulation signal format. A receiver BER of 10/sup -6/ was obtained at received signal powers that corresponded to an average of 70 detected signal photons per bit at a source data rate of 50 Mb/s, 130 detected signal photons/bit at 220 Mb/s, and about 400 detected signal photons/bit at a 325 Mb/s source data rate. Quantum-limited operation corresponds to an average of six detected signal photons per transmitted information bit for this signal format.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Medium Disturbance Sensing Techniques for FSK Modulation

This paper describes measurement techniques for rapidly characterizing frequency selective fading channels. The approach used involves estimating each of the parameters describing the transmitted signal and channel disturbances. This includes signal level, noise level, and multipath spread. While specifically applied to FSK modulation and HF channels, the techniques are applicable to other fading media such as troposcatter. The advantages of the proposed techniques are several: the measurement is performed by operating on the transmitted information bits and special test signals or redundancy are not required. Instrumentation is relatively simple and the techniques are applicable to practical communication media. Calculations are provided to determine the measurement time for stated accuracies and confidence levels. Results are obtained for several multipath distributions and as a function of the multipath-to-noise energy ratio.