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In this paper, a system based on time-hopping spread spectrum techniques for indoor visible light communications is studied via simulation. A 2-PPM modulation scheme is selected because it yields good results in wireless optical communications. Furthermore, the system allows for selecting the number of pulses per symbol to be transmitted and makes use of an optimum maximum-likelihood receiver for...
An improved normalized min-sum (IN-MS) algorithm is proposed for decoding low-density parity-check (LDPC) codes. In this algorithm, two normalized factors are used in check node computing, one for the minimum data and another for the second minimum data, and this algorithm achieves a better approximation to the BP algorithm. Simulation results show that the decoding performance of IN-MS algorithm...
A consensus approach can be exploited in order to maintain a desirable performance in ad-hoc networks which require low-power consumption. We show effects of interference on the consensus scheme for ad-hoc networks in terms of BER in this paper.
A Wireless Body Area network (WBAN) is a special purpose of Wireless Sensor Networks (WSNs) to connect various Biomedical Wireless Sensors (BWSs) located inside and outside of the human body to collect and transmit vital signals. The collected biomedical data send out via Gate Way (GW) to external databases at the hospitals and medical centers for diagnostic and therapeutic purposes. To increase the...
In the encoding of Luby transform (LT) codes, information bits (variable nodes) are randomly connected to the check nodes. Although the check-node degrees have been optimized for error-rate performance, the arbitrary connections in the code graph cannot guarantee efficient propagation of the channel information (intrinsic messages), and may slow down the convergence speed of the iterative decoding...
A cooperative communication system assisted by Turbo Trellis-Coded Modulation (TTCM) relying on Hierarchical Modulation (HM) is proposed, which invokes iterative soft decoding. Our results demonstrated that the performance of the single-relay aided cooperative system can be improved by at least 4 dB at a BER of 10−5.
In this paper, a resource allocation algorithm is proposed for different quality of service (QoS) guarantee, fair transmission and high data rate in orthogonal frequency division multiple access (OFDMA) and wireless local area network (WLAN) integrated system. First, different QoS requirements are converted into different rate requests for simplifying the optimization problem. Second, the sub-channels...
This paper investigates the resource allocation problem for multiple description coding (MDC) multicast in OFDM-based cognitive radio (CR) systems, where secondary users (SUs) share the primary spectrum under the interference constraints of primary users (PUs). The previous multicast model is usually based on the full buffer traffic in which there are sufficient data for multicast groups (MGs) to...
Low-density Parity-check (LDPC) coding is a class of advanced channel coding techniques. To improve the performance of LDPC codes, a simple and effective method to construct QC-LDPC codes without short cycles (cycles of length four and six) is proposed. The approach is especially effective when the parity-check matrix of QC-LDPC codes is composed of circulant permutation matrices. Firstly, we analyze...
In this paper, we extend the min-sum (MS) and its two improved algorithms (i.e., the normalized MS algorithm and the offset MS algorithm) to decode fountain codes over the binary input additive white Gaussian noise (BIAWGN) channel. We use Gaussian approximation method to analyze the asymptotic performance of fountain codes under various decoding algorithms and optimize the parameters of the two improved...
A non-binary LDPC codes whose parity check matrix has uniform column weight 2 is constructed in this paper. The approach derives a non-binary LDPC codes from a column-weight 2 binary LDPC codes which is designed according to a all one (2, k) matrix, We proposed a search algorithm for constructing a (2, k) LDPC codes with desired girth, and in this paper, we use the search algorithm twice to obtain...
Amplitude phase shift keying (APSK) constellation with Gray mapping was proposed recently. In this paper, a simplified soft demapping algorithm for Gray-APSK is developed. Simulation results show that the proposed algorithm decreases the soft demapping complexity considerably with little loss of SNR.
Radio resource management in multi-user LTE networks is considered in this paper. Subject to a transmission power constraint, genetic algorithm is firstly investigated to optimize the system transmission rate. However, result shows genetic algorithm has the flaws of slow convergence rate and cannot reach to the theoretical maximum transmission rate. Aiming at this point, ant colony algorithm (ACA)...
In this article a new method based on the function sinn(πt/2Tb) is proposed to obtain 2Tb-long base-band signal which can be applied to quadrature modulation to make the modulated signal constant-enveloped and phase-continuous. The power spectrum of the signal attenuates more quickly and the out-of-band radiation decreases. The general expression of the signal is given and the time-frequency property...
In the existing SCTP, an association is established by exchanging four initial chunks during four-way handshakes. What is serious is that the association establishment phase has to be backed off exponentially once any initial chunk gets lost or suffers random bit errors. This will result in a severe performance degradation of SCTP over wireless networks due to a very long waiting time. In order to...
Peak-to-average power ratio (PAPR) is a major problem for high rate communication systems, which employ e.g. quadrature amplitude modulation (QAM) with a large signal constellation set (SCS). We propose a novel and extremely simple scheme for PAPR reduction, which removes the critical channel symbols from the SCS and instead map the respective bit patterns to other existing channels symbols. This...
BER-aware-based light path setup approach is proposed for GMPLS-controlled optical networks. The approach takes BER parameter into consideration during the light path setup process, including two BER information distribution schemes and one BER-based routing calculation strategy. Among the two distribution schemes, Signaling-based BER Distribution (SBD) is based on RSVP-TE signaling protocol and Advertisement-based...
In the last years, Ultra Wideband (UWB) systems have received growing interest for their low-power consumption and low-complexity implementation. Because of the ultra-short emitted waveforms nature, timing acquisition presents a most important challenge for achieving good performance. In this paper, in order to address this task and to achieve this goal, we design and test a novel timing acquisition...
Although belief propagation (BP) algorithm can be used to solve the problem of LT decoding on noisy channels, the system performance turns out to be not very good. In this paper, we introduce one method to improve the system performance of LT soft decoding. The method is using different percent of systematic connections of encoded packets. Simulation results reveal the advantage of the proposed modified...
We present an efficiency analysis for the link-layer protocol that controls the operation of state-of-the-art 1 Gb/s optical wireless links when applied to 10 Gb/s communications. We utilize analytical and simulation results to demonstrate the impact of physical layer parameters, including the link turnaround time and the bit-error-rate, on the protocol efficiency. Based on the results, we discuss...
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