In this paper, the performance of a non-binary turbo coded ultra wide band (UWB) system is analyzed and simulated in multi-user environments. A binary pulse position modulation-time hopping (BPPM-TH) UWB system is con...
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In this paper, the performance of a non-binary turbo coded ultra wide band (UWB) system is analyzed and simulated in multi-user environments. A binary pulse position modulation-time hopping (BPPM-TH) UWB system is considered. The performance is evaluated in terms of bit error probability. Simulation results demonstrate that the performance of such a UWB system can be substantially improved by increasing the number of iterations in the decoding process. Also, it is confirmed that non-binary turbo coding is very effective in increasing the number of simultaneous users for a given bit error probability requirement.
Recently, researches on space-time codes deploying multiple transmit and receive antennas have abruptly emerged due to its potential to greatly improve spectral efficiency. Particularly, space-time bit-interleaved cod...
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Recently, researches on space-time codes deploying multiple transmit and receive antennas have abruptly emerged due to its potential to greatly improve spectral efficiency. Particularly, space-time bit-interleaved coded modulation (ST-BICM) gives rise to very reliable bit error rate (BER) performance with quite flexible rate compatibility. In this paper, we propose an iterative linear minimum-mean-squared-error (LMMSE) channel estimation, detection, and decoding for ST-BICM systems over block fading channels in order to resolve more practical problems concerned with the performance degradation due to imperfect channel state information (CSI). The LMMSE channel estimation and detection are performed using a priori information fed back from the soft-input / soft-output (SISO) channel decoder in a computational efficient manner. The simulation results demonstrate that the performance of our proposed algorithm approaches to the matched filter bound (MFB) with an SNR loss of less than 1 dB at BER of 10 -6 , and its convergence of behavior is presented with the extrinsic information transfer (EXIT) charts.
In this paper, we consider a primary and a cognitive user transmitting over a wireless fading interference channel. The primary user transmits with a constant power and utilizes an adaptive modulation and coding (AMC)...
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In this paper, we consider a primary and a cognitive user transmitting over a wireless fading interference channel. The primary user transmits with a constant power and utilizes an adaptive modulation and coding (AMC) scheme satisfying a bit error rate requirement. We propose a link adaptation scheme to maximize the average spectral efficiency of the cognitive radio, while a minimum required spectral efficiency for the primary user is provisioned. The resulting problem is constrained to also satisfy a bit error rate requirement and a power constraint for the cognitive link. The AMC mode selection and power control at the cognitive transmitter is optimized based on the scaled signal to noise plus interference ratio feedback of both links. The problem is then cast as a nonlinear discrete optimization problem for which a fast and efficient suboptimum solution is presented. We also present a scheme with rate adaption and a constant power. An important characteristic of the proposed schemes is that no negotiation between the users is required. Comparisons with underlay and interweave approaches to cognitive radio with adaptive transmission demonstrate the efficiency of the proposed solutions.
In this paper we study the capacity of the OFDMA- based IEEE802.16 WiMAX network in the presence of two types of traffic: real-time and non-real-time, including adaptive modulation and coding (AMC) with user intra cel...
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In this paper we study the capacity of the OFDMA- based IEEE802.16 WiMAX network in the presence of two types of traffic: real-time and non-real-time, including adaptive modulation and coding (AMC) with user intra cell mobility. Our work deals with the performance of the connexion admission and resource allocation algorithm over a general ranging arrival process: it has been recently proved that the exponential distribution is inappropriate. Based on the generalized traffic processes, we develop a resource allocation that maintains the bit rate of real time connections independently of the user position in the cell. Moreover, we enhance the CAC algorithm with a mecanism designed for the mobility management. Using a novel discrete time Markovian analysis we evaluate the impact of our resource allocation for mobility behavior on the RT and NRT connections as the blocking and dropping probabilities, mean sojourn time and throughput.
A technique is presented here in the 60 GHz band for implementation of side-band suppression with simultaneous frequency up-conversion of a 64-level and 16-level quadrature amplitude modulated (64-QAM, 16-QAM) Wireles...
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A technique is presented here in the 60 GHz band for implementation of side-band suppression with simultaneous frequency up-conversion of a 64-level and 16-level quadrature amplitude modulated (64-QAM, 16-QAM) Wireless Local Area Network (WLAN) IEEE 802.11a signal with 54 Mbps and 36 Mbps bit rates, respectively and 3/4 code rate. It is based on the use of a Fiber Bragg Grating (FBG). Filtering technique will demonstrate suppression by up to 25 dB of the upper side band. The feasibility of our system is then verified through experimental results of signal 64-QAM and 16-QAM modulations over 25 Km of propagation along a Single Mode Fiber (SMF) with good error vector magnitude Root Mean Square (EVM rms) performance of 5.82% and 6.31% at minimum, respectively.
This paper presents a dual mode fast performance prediction method for iterative minimum-mean square error interference cancellation based joint decoding in a very general multiuser MIMO setting, considering a transmi...
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This paper presents a dual mode fast performance prediction method for iterative minimum-mean square error interference cancellation based joint decoding in a very general multiuser MIMO setting, considering a transmission over block-fading frequency-selective channels. The symbolic mode relies on a signal to interference-plus-noise ratio compression at symbol level, by means of the mutual information effective signal-to-noise metric (MIESM), bridging the gap between the extrinsic information transfer (EXIT) charts and the compression methods developed for link-to-system interface. The binary mode follows the classical EXIT chart approach relying on a new analytical formula of the bit interleaved coded modulation average mutual information in presence of non-uniform a priori on input bits. This paper demonstrates the superiority of the symbolic mode for high order modulation.
NASA is presently overseeing a project to create the world's first free-space laser communications system that can be operated over a range ten times larger than the near-earth ranges that have been demonstrated t...
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NASA is presently overseeing a project to create the world's first free-space laser communications system that can be operated over a range ten times larger than the near-earth ranges that have been demonstrated to date. To be flown on the lunar atmosphere and dust environment explorer (LADEE), which is planned for launch by NASA in 2012, it will demonstrate high-rate laser communications from lunar orbit to a transportable ground terminal on the Earth. To support up to 622 Mbps over the approximately 400 thousand kilometer link, the system will make use of a high peak power doped fiber transmitter, a hybrid pointing and tracking system, high efficiency modulation and coding techniques, superconducting photon counting detectors, and a scalable optical collector architecture. It also will support up to 20 Mbps on the optical uplink, plus a highly accurate continuous two-way time of flight measurement capability with the potential to perform ranging with sub-centimeter accuracy to the moving spacecraft. The project is being undertaken by MIT Lincoln Laboratory (MIT/LL) and the NASA Goddard Space Flight Center (GSFC.).
We propose a new framework to analyze performance considering finite-length queuing and adaptive modulation and coding (AMC) for multi-user VoIP services in wireless communication systems. We formulate an uplink VoIP ...
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We propose a new framework to analyze performance considering finite-length queuing and adaptive modulation and coding (AMC) for multi-user VoIP services in wireless communication systems. We formulate an uplink VoIP system as two-dimensional discrete-time Markov chain (DTMC) based on a Markov modulated Poisson process (MMPP) traffic model and MCS (modulation and coding scheme)-level set transition reflecting users' channel variations. We extend transition modeling of MCS-level for single-user to transition modeling of MCS-level set for multi-user. Throughout our DTMC formulation, we present various performance metrics, such as average queue-length, the average number of arrived and serviced packets, and packet dropping probability.
In this contribution we jointly optimize the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power under the constraint of a given fixed data thr...
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In this contribution we jointly optimize the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power under the constraint of a given fixed data throughput and integrity. However, non-frequency selective MIMO links have attracted a lot of research and have reached a state of maturity. By contrast, frequency selective MIMO links require substantial further research, where spatio-temporal vector coding (STVC) introduced by Raleigh seems to be an appropriate candidate for broadband transmission channels. In analogy to bit-interleaved coded irregular modulation, we introduce a MIMO-BICM scheme, where different signal constellations and mappings are used within a single codeword. Extrinsic information transfer (EXIT) charts are used for analyzing and optimizing the convergence behaviour of the iterative demapping and decoding.
The paper presents an implementation of continuous time analog filter dedicated for nonuniform sampling delta modulator (NSDM) based audio codec. The circuit is also suited for low voltage application-it is based on C...
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The paper presents an implementation of continuous time analog filter dedicated for nonuniform sampling delta modulator (NSDM) based audio codec. The circuit is also suited for low voltage application-it is based on CMOS inverter working in weak inversion region. System considerations, filter synthesis as well as simulation results of the chip sent for manufacturing are presented.
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