Topic
Modulation
About: Modulation is a research topic. Over the lifetime, 56045 publications have been published within this topic receiving 578873 citations.
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TL;DR: Simulations show that OFDM systems using the proposed ICI self-cancellation scheme perform much better than standard systems while having the same bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies.
Abstract: For orthogonal frequency-division multiplexing (OFDM) communication systems, the frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI). This paper studies an efficient ICI cancellation method termed ICI self-cancellation scheme. The scheme works in two very simple steps. At the transmitter side, one data symbol is modulated onto a group of adjacent subcarriers with a group of weighting coefficients. The weighting coefficients are designed so that the ICI caused by the channel frequency errors can be minimized. At the receiver side, by linearly combining the received signals on these subcarriers with proposed coefficients, the residual ICI contained in the received signals can then be further reduced. The carrier-to-interference power ratio (CIR) can be increased by 15 and 30 dB when the group size is two or three, respectively, for a channel with a constant frequency offset. Although the redundant modulation causes a reduction in bandwidth efficiency, it can be compensated, for example, by using larger signal alphabet sizes. Simulations show that OFDM systems using the proposed ICI self-cancellation scheme perform much better than standard systems while having the same bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies.
788 citations
TL;DR: In this article, a technique for transmitting digital information using a chaotic carrier is described, in which each symbol to be transmitted is coded as an attractor in Chua's circuit.
Abstract: Describes a technique for transmitting digital information using a chaotic carrier. Each symbol to be transmitted is coded as an attractor in Chua's circuit. The symbols are detected at the receiver by cascaded self-synchronizing Chua's circuit subsystems. A proof of the synchronization effect is demonstrated using weak assumptions on the statistical behavior of the chaotic carrier to be transmitted. Furthermore a bound for the average time of synchronization is given. Results of both practical experimentation and simulations are presented which verify the approach. >
787 citations
TL;DR: With this approach and coordinated processing at a common receiver, it is shown that the aggregate data rate of all simultaneous users can approach the Shannon capacity of the Gaussian noise channel.
Abstract: A spread-spectrum multiple-access (SSMA) communication system is treated for which both spreading and error control is provided by binary PSK modulation with orthogonal convolution codes. Performance of spread-spectrum multiple access by a large number of users employing this type of coded modulation is determined in the presence of background Gaussian noise. With this approach and coordinated processing at a common receiver, it is shown that the aggregate data rate of all simultaneous users can approach the Shannon capacity of the Gaussian noise channel. >
784 citations
TL;DR: The author examines the practical design criteria for implementing oversampled analog/digital converters based on second-order sigma-delta ( Sigma Delta ) modulation and applies these criteria to the design of a modulator that has been integrated in a 3- mu m CMOS technology.
Abstract: The author examines the practical design criteria for implementing oversampled analog/digital converters based on second-order sigma-delta ( Sigma Delta ) modulation. Behavioral models that include representation of various circuit impairments are established for each of the functional building blocks comprising a second-order Sigma 2gD modulator. Extensive simulations based on these models are then used to establish the major design criteria for each of the building blocks. As an example, these criteria are applied to the design of a modulator that has been integrated in a 3- mu m CMOS technology. An experimental prototype operates from a single 5-V supply, dissipates 12 mW, occupies an area of 0.77 mm/sup 2/, and has achieved a measured dynamic range of 89 dB. >
779 citations
TL;DR: It is shown via computer simulations that the proposed OFDM with index modulation scheme achieves significantly better error performance than classical OFDM due to the information bits carried in the spatial domain by the indices of OFDM subcarriers.
Abstract: In this paper, a novel orthogonal frequency division multiplexing (OFDM) scheme, called OFDM with index modulation (OFDM-IM), is proposed for operation over frequency-selective and rapidly time-varying fading channels In this scheme, the information is conveyed not only by M-ary signal constellations as in classical OFDM, but also by the indices of the subcarriers, which are activated according to the incoming bit stream Different low complexity transceiver structures based on maximum likelihood detection or log-likelihood ratio calculation are proposed and a theoretical error performance analysis is provided for the new scheme operating under ideal channel conditions Then, the proposed scheme is adapted to realistic channel conditions such as imperfect channel state information and very high mobility cases by modifying the receiver structure The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors For the mobility case, several interference unaware/aware detection methods are proposed for the new scheme It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions
752 citations