Codes for rank modulation have been recently proposed as a means of protecting flash memory devices from errors. We study basic coding theoretic problems for such codes, representing them as subsets of the set of perm...
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Codes for rank modulation have been recently proposed as a means of protecting flash memory devices from errors. We study basic coding theoretic problems for such codes, representing them as subsets of the set of permutations of n elements equipped with the Kendall tau distance. We derive several lower and upper bounds on the size of codes. These bounds enable us to establish the exact scaling of the size of optimal codes for large values of n. We also show the existence of codes whose size is within a constant factor of the sphere packing bound for any fixed number of errors.
This work presents an effective IPTV channel control algorithm that improves the subscribers' QoE for mobile IPTV service over WiMAX network. We consider video quality of TV channels and channel zapping time as th...
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This work presents an effective IPTV channel control algorithm that improves the subscribers' QoE for mobile IPTV service over WiMAX network. We consider video quality of TV channels and channel zapping time as the QoE metrics. The proposed algorithm controls the channel distribution state and the target bit rate of TV channels based on the channel preference information to pursue an effective trade-off between channel zapping time and video quality. Finally, experimental results are provided to demonstrate the performance of proposed system.
A digital baseband receiver ASIC that supports GSM/GPRS/EDGE and Evolved EDGE is implemented in 0.13 ¿m CMOS technology. The design centers around two main blocks: an adaptive channel equalizer processes GMSK/8PS...
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A digital baseband receiver ASIC that supports GSM/GPRS/EDGE and Evolved EDGE is implemented in 0.13 ¿m CMOS technology. The design centers around two main blocks: an adaptive channel equalizer processes GMSK/8PSK/16QAM and 32 QAM modulated signals and a flexible channel decoder supports convolutional and turbo codes, as required for Evolved EDGE. The receiver occupies 2.0 mm 2 and the average power consumption during burst reception and processing is less than 5 mW in each of the modes.
Iterative Decision Directed Channel Estimation (DDCE) scheme is proposed in this paper for bit interleaved coded modulation (BICM)-based MIMO-OFDM systems. The proposed scheme employs Variable Step Size Normalized Lea...
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Iterative Decision Directed Channel Estimation (DDCE) scheme is proposed in this paper for bit interleaved coded modulation (BICM)-based MIMO-OFDM systems. The proposed scheme employs Variable Step Size Normalized Least Mean Square (VSSNLMS) algorithm to implement its temporary Channel Transfer Function (CTF) Estimator and Adaptive Channel Impulse Response (CIR) predictor modules, while Fast Data Projection Method (FDPM) algorithm is employed to track the time domain CIR of the MIMO channel. The proposed iterative DDCE operates in an iterative mode in conjunction with MIMO demappers and the Turbo decoder at receiver of the MIMO-OFDM system. The achievable performances of the proposed scheme in terms of both mean square error (MSE) and bit error rate (BER) are presented. Comparative performances between the DDCE scheme employing FDPM algorithm and another one employing deflated Projection Approximation Subspace Tracking (PASTd) algorithm are also given. The simulations results presented indicate better performances of the proposed scheme.
Link evaluation is very important to system level simulation. Current algorithms for link evaluation show pretty good accuracy for wireless system with linear detections. However, when it comes to MIMO-OFDM system wit...
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Link evaluation is very important to system level simulation. Current algorithms for link evaluation show pretty good accuracy for wireless system with linear detections. However, when it comes to MIMO-OFDM system with ML Detection, problems still exists. This paper proposes an Extended Received Block Information Rate algorithm for link evaluation, which is deduced from the view of information and detecting theory. Accuracy and universality of this algorithm for MIMO-OFDM system with ML detection are highlighted. Simulation results show that, comparing to current algorithms for link evaluation, the proposed ERBIR algorithm obtains better accuracy and universality.
This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaN-HEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band...
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This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaN-HEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band-pass delta-sigma modulation with 1.68 Gbps sampling frequency. The respective efficiency is 34%. We find that these values strongly vary with coding efficiency of the modulation and reach 19 W with 59% for square-wave excitation. In order to clarify the potential of the PA in more detail, the S-class characteristics at power back-off and with varying oversampling ratio are presented as well.
The IEEE 802.11 standard supports a variety of modulation and coding schemes (MCSs). In 802.11-based wireless mesh networks (WMNs) it is hence possible to adapt the link rate to the channel conditions. In particular, ...
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The IEEE 802.11 standard supports a variety of modulation and coding schemes (MCSs). In 802.11-based wireless mesh networks (WMNs) it is hence possible to adapt the link rate to the channel conditions. In particular, smaller link rates may be accepted for an increased spatial reuse. In an earlier study, we showed that this effect is suitable for increasing the max-min fair share throughput in a WMN operating with a TDMA channel access scheme. In this work, we investigate if the use of smaller link rates is also suitable for increasing the throughput of a WMN using a contention-based channel access mechanism. For this purpose, we analytically derive a guideline for link rate assignment as protection against hidden nodes and compute the costs and benefits of this mechanism in terms of MAC layer efficiency. A simulation study shows however that in a medium-sized WMN this strategy is less advantageous than assumed and allows to give advices for practical mesh network deployments.
This paper assesses the spectral efficiencies that can be achieved in theory and simulation for several channel models, and where the same spectral efficiencies can result from different combinations of the signal con...
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ISBN:
(纸本)9781424444618
This paper assesses the spectral efficiencies that can be achieved in theory and simulation for several channel models, and where the same spectral efficiencies can result from different combinations of the signal constellation and channel code rate. A trade-off analysis is presented both for satellite and terrestrial channels for the impact on the spectral efficiency G of increasing the modulation order and at the same time reducing the code rate.
The introduction of physical layer network coding gives rise to the concept of turning a collision of transmissions on a wireless channel useful. In the idea of physical layer network coding, two synchronized simultan...
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ISBN:
(纸本)9781424451753;9781424451760
The introduction of physical layer network coding gives rise to the concept of turning a collision of transmissions on a wireless channel useful. In the idea of physical layer network coding, two synchronized simultaneous packet transmissions are carefully encoded such that the superimposed transmission can be decoded to produce a packet which is identical to the bitwise binary sum of the two transmitted packets. This paper explores the decoding of superimposed transmission resulted by multiple synchronized simultaneous transmissions. We devise a coding scheme that achieves the identification of individual transmission from the synchronized superimposed transmission. A mathematical proof for the existence of such a coding scheme is given.
This paper considers a novel error-correcting scheme exploiting chaotic dynamics for noncoherent chaos communication. In our proposed system, two successive chaotic sequences are generated from the same chaotic map; t...
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This paper considers a novel error-correcting scheme exploiting chaotic dynamics for noncoherent chaos communication. In our proposed system, two successive chaotic sequences are generated from the same chaotic map; the second sequence is generated with an initial value which is the last value of the first sequence. In this case, successive chaotic sequences having the same chaotic dynamics are created. This feature gives the receiver additional information to correctly recover the information data and thus improves the bit error performance of the receiver. Further, enhanced efficiency also comes from operating on successively modulated data; by involving less redundancy in the error correction system, it can be designed with high coding rate. In this paper, we analyze the scheme's capability, by examining computational times and accuracy rates of error correction, bounds on its capability.
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