Number Of Information Bits Research Articles

Link Resource Adaptation for Multiantenna Bit-Interleaved Coded Multicarrier Systems

The availability of flexible radio interfaces capable of adapting their configuration to the time-varying operating environment is the key response to the demand encountered in modern wireless networks for high data rates under strict quality of service (QoS) constraints. To this end, this paper develops a novel link resource adaptation (LRA) scheme for soft-decoded multiantenna (MIMO) bit interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) transmissions employing automatic repeat request (ARQ) mechanisms. As the first step, a simple link performance evaluation model based on the effective signal-to-noise ratio (SNR) mapping concept is derived in a closed-form expression that it is shown to yield better accuracy than previous techniques. Then, an effective LRA strategy is formulated taking advantage of that framework. The aim is maximizing the goodput (GP) metric, that is to say, the number of information bits delivered without error to the user by unit of time, over the available radio resources, such as the power distribution on the subchannels, coding rate, modulation order and the MIMO configuration. The numerical results demonstrate considerable performance gains compared with nonadaptive transmissions, while keeping the computational complexity at affordable levels in view of the specific structure of the GP objective function.

Multiple Error-Correcting WOM-Codes

A Write Once Memory (WOM) is a storage medium with binary memory elements, called cells, that can change from the zero state to the one state only once. Examples of WOMs include punch cards and optical disks. WOM-codes, introduced by Rivest and Shamir, permit the reuse of a WOM by taking into account the location of cells that have already been changed to the one state. The objective in designing WOM-codes is to use the fewest number of cells to store a specified number of information bits in each of several reuses of the memory. An [n,k,t] WOM-code C is a coding scheme for storing k information bits in n cells t times. At each write, the state of each cell can be changed, provided that the cell is changed from the zero state to the one state. The rate of C, defined by R(C) = kt/n, indicates the total amount of information that is possible to store in a cell in t writes. Two WOM-code constructions correcting a single cell-error were presented by Zemor and Cohen. In this paper, we present another construction of a single-error-correcting WOM-code with a better rate. Our construction can be adapted also for single-error-detection, double-error-correction, and triple-error-correction. For the last case, we use triple-error-correcting BCH-like codes, which were presented by Kasami and more recently described again by Bracken and Helleseth. Finally, we show two constructions that can be combined for the correction of an arbitrary number of errors.

Supervisory control of uncertain systems with quantized information

SUMMARYThis work addresses the problem of stabilizing uncertain systems with quantized outputs using the supervisory control framework, in which a finite family of candidate controllers is employed together with an estimator‐based switching logic to select the active controller at every time. For static quantizers, we provide a relationship between the quantization range and the quantization error bound that guarantees closed‐loop stability. Such a condition also implies a lower bound on the number of information bits needed to guarantee stability of a supervisory control scheme with quantized information. For dynamic quantizers that can vary the quantization parameters in real time, we show that the closed loop can be asymptotically stabilized, provided that additional conditions on the quantization range and the quantization error bound are satisfied. Copyright © 2012 John Wiley & Sons, Ltd.

Variable Length Unordered Codes

In an unordered code, no code word is contained in any other code word. Unordered codes are all unidirectional error detecting (AUED) codes. In the binary case, it is well known that among all systematic codes with k information bits, Berger codes are optimal unordered codes with r=[log2(k+1)] ≅ log2k check bits. This paper gives some new theory on variable length unordered codes and introduces a new class of systematic (instantaneous) unordered codes with variable length check symbols. The average redundancy of the new codes presented here is r ≅ (1/2)log2k+c, where c ∈ (1.0470,1.1332) ⊆ IR and k ∈ IN is the number of information bits. When k is large, it is shown that such redundancy is at most 0.6069 bits off the redundancy of an optimal systematic unordered code design with fixed length information symbols and variable length check symbols; and, at most 2.8075 bits off the redundancy of an optimal variable length unordered code design. The generalization is also given for the nonbinary case and it is shown that similar results hold true.

Minimum Energy to Send $k$ Bits Through the Gaussian Channel With and Without Feedback

The minimum achievable energy per bit over memoryless Gaussian channels has been previously addressed in the limit when the number of information bits goes to infinity, in which case it is known that the availability of noiseless feedback does not lower the minimum energy per bit, which is -1.59 dB below the noise level. This paper analyzes the behavior of the minimum energy per bit for memoryless Gaussian channels as a function of k, the number of information bits. It is demonstrated that in this nonasymptotic regime, noiseless feedback leads to significantly better energy efficiency. In particular, without feedback achieving energy per bit of -1.57 dB requires coding over at least k=106 information bits, while we construct a feedback scheme that transmits a single information bit with energy -1.59 dB and zero error. We also show that unless k is very small, approaching the minimal energy per bit does not require using the feedback link except to signal that transmission should stop.

Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion

Bit-Error-Ratio (BER) of intensity modulated optical orthogonal frequency division multiplexing (OFDM) system is analytically evaluated accounting for nonlinear digital baseband distortion in the transmitter and additive noise in the photo receiver. The nonlinear distortion that is caused by signal clipping and quantization is taken into consideration. The signal clipping helps to overcome the system performance limitation related to high peak-to-average power ratio (PAPR) of the OFDM signal and to minimize the value of optical power that is required for achieving specified BER. The signal quantization due to a limited bit resolution of the digital to analog converter (DAC) causes an optical power penalty in the case when the bit resolution is too low. By introducing an effective signal to noise ratio (SNR) the optimum signal clipping ratio, system BER and required optical power at the input to the receiver is evaluated for the OFDM system with multi-level quadrature amplitude modulation (QAM) applied to the optical signal subcarriers. Minimum required DAC bit resolution versus the size of QAM constellation is identified. It is demonstrated that the bit resolution of 7 and higher causes negligibly small optical power penalty at the system BER=10⁻³ when 256-QAM and a constellation of lower size is applied. The performance of the optical OFDM system is compared to the performance of the multi-level amplitude-shift keying (M-ASK) system for the same number of information bits transmitted per signal sample. It is demonstrated that in the case of the matched receiver the M-ASK system outperforms OFDM and requires 3-3.5 dB less of optical power at BER=10⁻³ when 1-4 data bits are transmitted per signal sample.

Minimum energy-per-bit wireless multi-hop networks with spatial reuse

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

End-to-End Energy–Bandwidth Tradeoff in Multihop Wireless Networks

In this paper, energy-constrained wireless multihop networks with a single source-destination pair are considered. A network model that incorporates both the energy radiated by the transmitter and the energy consumed by the circuits that process the received signals is proposed. The rate of communication is the number of information bits transmitted (end-to-end) per coded symbol transmitted by any node in the network that is forwarding the data. The tradeoff between the total energy consumption and the end-to-end rate of communication is analyzed. The performance (either energy or rate) depends on the transmission strategy of each node, the location of the relay nodes, and the data rate used by each node. Communication strategies include the rate of transmission on each link, the scheduling of links, and the power used for each link. Strategies that minimize the total energy consumption for a given rate are found. Two communication strategies that capture the inherent constraints of some practical networks are also considered and compared with the optimum strategies. In the case of equispaced relays, analytical results for the tradeoff between the energy and the end-to-end data rate are provided. The minimum energy over all possible data rates is also obtained. Low rates incur a significant penalty because the receiver is on for a long time period while high rates require high transmission energy. At high rates routes with fewer hops minimize the energy consumption while at lower rates more hops minimize the energy consumption.

An overview of limited feedback in wireless communication systems

It is now well known that employing channel adaptive signaling in wireless communication systems can yield large improvements in almost any performance metric. Unfortunately, many kinds of channel adaptive techniques have been deemed impractical in the past because of the problem of obtaining channel knowledge at the transmitter. The transmitter in many systems (such as those using frequency division duplexing) can not leverage techniques such as training to obtain channel state information. Over the last few years, research has repeatedly shown that allowing the receiver to send a small number of information bits about the channel conditions to the transmitter can allow near optimal channel adaptation. These practical systems, which are commonly referred to as limited or finite-rate feedback systems, supply benefits nearly identical to unrealizable perfect transmitter channel knowledge systems when they are judiciously designed. In this tutorial, we provide a broad look at the field of limited feedback wireless communications. We review work in systems using various combinations of single antenna, multiple antenna, narrowband, broadband, single-user, and multiuser technology. We also provide a synopsis of the role of limited feedback in the standardization of next generation wireless systems.

BCH-based Compactors with Data Compression for Test Responses

This paper presents a novel approach to compacting a test response for a multiple scan chains design. The compactor design is based on an extended ( + 1; k) BCH code, where k is the number of information bits and + 1 is the number of bits in the block. It can detect any odd number of single bit errors or up to 2t single-bit errors, where t is a positive integer, - k mt, and + 1 = 2m. Also we use a controllable mask to handle any number of unknown logic values (Xs) on test responses. We show how extra control data can be reduced by proposed compression technique. Compared to augmenting previous space compaction techniques with additional circuitry to mask any number of Xs, our approach can detect more single-bit errors with minimum number of compactor outputs. This leads to fewer tester channels, shorter test application time, and smaller test data volumes regardless of the Circuit Under Test (CUT) and fault models.

Bit and Power Allocation for Goodput Optimization in Coded Parallel Subchannels With ARQ

This paper addresses the problem of adaptively allocating the bits and the power among a set of parallel subchannels. A frame-oriented transmission with convolutional coding, hard Viterbi decoding, and automatic repeat request (ARQ) retransmission protocol is considered. The objective is to maximize the number of information bits delivered without error to the user by unit of time, or goodput. This criterion is a tradeoff between the bit rate and bit error probability criteria. First, a mathematical expression for the goodput of the system is presented. Then, using that expression, different bit and power allocation strategies are derived and compared. It turns out that having an equal bit error rate (BER) on each subchannel is near-optimal in terms of goodput. Finally, we prove that the waterfilling solution with adequate signal to noise ratio (SNR) gap value (or equivalently adequate target BER value) is near-optimal. We analytically show how this SNR gap value depends on the convolutional code used, the frame length, the type of ARQ protocol used, the available transmit power, and the subchannel gains.

Bits-per-Joule Capacity of Energy-Limited Wireless Networks

For a wireless network in which every node is bounded in its energy supply, we define a new concept of network capacity called "bits-per-Joule capacity", which is the maximum total number of bits that the network can deliver per Joule of energy deployed into the network. For a fixed network size, a finite number of information bits is delivered for each source-destination pair, under a fixed end-to-end probability of error constraint. We prove that under the one-to-one traffic model in which every node wants to send traffic to a randomly chosen destination node, the bits-per-Joule capacity of a stationary wireless network grows asymptotically as Omega((N/logN) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(q-1)/2 </sup> ), where N is the number of nodes randomly deployed onto the surface of a sphere and q is the path loss exponent. Further, the length of the block codes used grows only logarithmically in N, which indicates manageable decoder complexity as the network scales. The fact that the bits-per-Joule capacity grows with the number of nodes contrasts sharply with the scaling laws that have been derived for throughput capacity and implies that large-scale deployments for energy-limited sensor and ad hoc networks may be suitable for delay-tolerant data applications

Lisibilité et densité d’information en recherche biomédicale

This study was performed in order to compare the lexicosyntactic readability, and the information density in the informed consent forms used in biomedical research, in comparison with standard scientific texts dedicated to the general population. In addition, we studied whether there is a correlation between information readability and density. Fifteen informed consent forms, 6 articles from "Sciences et Avenir" and 6 articles from "Sciences et Vie Junior" were analyzed. The lexicosyntactic readability was calculated using the Flesh score, and the information density using the number of information bits related to the number of words. The lexicosyntactic readability was lower in the informed consent forms (25, 17-32) compared with "Sciences et Avenir" (32, 29-38), but even higher in "Sciences et Vie Junior" (42, 38-57). Conversely, the information density was similar in "Sciences et Vie Junior" (0.24, [0.21-0.27]) and the informed consent forms (0.24, [0.22-0.26]), but higher in "Sciences et Avenir" (0.32, [0.26-0.38]). Informed consent forms are less readable, but paradoxically less dense than scientific papers dedicated to the general population. There is no correlation between density and readability.

Reduced-rate retransmissions for spread-spectrum packet radio multimedia networks

A reduced-rate retransmission (RRR) scheme is proposed for improving the throughput performance of spread-spectrum packet radio networks. The scheme takes advantages of the available multi-rate scalable source coding techniques. It assumes that several versions of a data packet with different sizes (number of information bits) are available. The transmission of a packet starts from its full-size version. If the full-size version is not correctly received, its half-size version is used in the retransmission. If further retransmissions are needed, the quarter-size version and so on are used. The shrunk packets are transmitted either in a minislot if the processing gain is kept the same, or occupying a slot duration by increasing the processing gain proportionally. In both cases, the effective signal to interference ratio for a packet is increased. As a result, the system throughput is improved. Theoretical and numerical results are provided in this paper which illustrate the throughput improvement. Another advantage of the proposed RRR scheme is that the packet-size reduction provides finer granules for link adaptation. Therefore, it is especially suitable for multimedia applications for which codes of variable rate for the source data are available and which can tolerate gracefully degraded quality of service. The performance of the proposed scheme in fading channels is also addressed.

On the Capacity of Write-Unidirectional Memories With Nonperiodic Codes

Write-unidirectional memories (WUMs) were introduced by Willems, Vinck, and Borden as an information-theoretic model for storing and updating information on a rewritable medium with the writing constraints: During the odd (resp., even) cycles of updating information, the encoder can only write 1's (resp., 0's) in selected bit positions of WUMs, and not change the contents of other positions. In this correspondence, motivated by the research works of Wolf, Wyner, Ziv, and Ko/spl uml/rner on write-once memories (WOMs), we study the problem of how to reuse a WUM for fixed T successive cycles with nonperiodic codes (i.e., all coding strategies are permitted for every cycle). For the situation where the encoder knows and the decoder does not know the previous content of the memory, we determine the zero-error capacity region, the average capacity, and the maximum total number of information bits stored in the WUM for fixed T successive cycles. Motivated by the research works of Heegard on WOMs with symmetric input noise, we introduce two models of WUMs with symmetric or asymmetric input noise. By using /spl epsiv/-error as performance criterion, we extend the above results for WUMs to the two models of WUMs with symmetric or asymmetric input noise.

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.

The effect of spreading gain control on a CDMA slotted ALOHA system

In a CDMA slotted ALOHA channel, the bit rate of user information is determined by a spreading gain. The large value of spreading gain enhances the packet throughput by increasing the probability of a successful packet transmission. However, it degrades the effective throughput by reducing the number of information bits carried via a packet. To solve the problem, we investigated the effect of spreading gain control (SGC) on both throughputs, and evaluated the throughput performance for various SGC schemes. The results show that variable SGC achieves considerably higher effective throughput by adjusting the value of spreading gain to interference level.

Turbo code frame synchronization

A novel frame synchronization technique for a turbo decoder is presented based on the concept of a probability surface metric within a modified maximum a posteriori decoder. Using a counter with a reflecting barrier to establish whether there is sufficient evidence to reject the existing synchronization state, theoretical expressions are derived for the performance of this technique for any channel signal-to-noise ratio. The probability of a false-alarm can be reduced to an extremely small value with a penalty of only a slight increase in the average number of information bits to be processed to reject an incorrect synchronization state. Simulation results are presented for the standard rate 1/2 (7,5) turbo code.

Trellis codes for periodic erasures

This paper describes techniques for the design and analysis of trellis codes that provide reliable communication over every channel in a specified set of possible channels, where each channel is characterized by additive white Gaussian noise with a distinct periodic variation in signal-to-noise ratio. An important practical application for such trellis codes is the periodic erasure channel produced by partial-band interference dispersed by a block interleaver. We present trellis codes that provide reliable communication over all periodic erasure patterns of a given period for which the number of unerased coded bits per period is at least equal to the number of information bits per period.

Adaptive multilevel code selection and MUI cancellation for DS/CDMA over fading channel

For transmission of speech or multimedia information in a time-varying mobile channel, fixed rate codes are normally used designed for average or worst channel conditions. However, fixed rate codes fail to explore the time-varying nature of the mobile channel. In their previous work the authors have shown that a multilevel code, when used in conjunction with multiuser interference (MUI) cancellation in cascade, yields better performance than a conventional coded modulation scheme applied to CDMA. They show that, when multilevel codes are changed with varying channel conditions (i.e. are chosen adaptively according to the channel state information (CSI)), throughput (average number of information bits per symbol duration) can be increased without too much performance degradation. Code selection criteria as well as some codes with appropriate thresholds are also presented.