Communication channel

About: Communication channel is a research topic. Over the lifetime, 137411 publications have been published within this topic receiving 1715077 citations. The topic is also known as: communication channel & communications channel.

System and method for pushing information to a mobile device

Abstract: A system for pushing information to a mobile device includes a information source, a wireless network, and a proxy content server. The information source stores information. The wireless network sends and receives transmissions to and from the mobile device. The proxy content server is coupled to information source and the wireless network and receives information from the information source. In addition, the proxy content server stores information received from the information source to one of a plurality of channels based on pre-defined information categories, and automatically transmits information from a selected channel over the wireless network to the mobile device.

Blind Channel Estimation for MIMO-OFDM Systems

Abstract: By combining multiple-input multiple-output (MIMO) communication with the orthogonal frequency division multiplexing (OFDM) modulation scheme, MIMO-OFDM systems can achieve high data rates over broadband wireless channels. In this paper, to provide a bandwidth-efficient solution for MIMO-OFDM channel estimation, we establish conditions for channel identifiability and present a blind channel estimation technique based on a subspace approach. The proposed method unifies and generalizes the existing subspace-based methods for blind channel estimation in single-input single-output OFDM systems to blind channel estimation for two different MIMO-OFDM systems distinguished according to the number of transmit and receive antennas. In particular, the proposed method obtains accurate channel estimation and fast convergence with insensitivity to overestimates of the true channel order. If virtual carriers (VCs) are available, the proposed method can work with no or insufficient cyclic prefix (CP), thereby potentially increasing channel utilization. Furthermore, it is shown under specific system conditions that the proposed method can be applied to MIMO-OFDM systems without CPs, regardless of the presence of VCs, and obtains an accurate channel estimate with a small number of OFDM symbols. Thus, this method improves the transmission bandwidth efficiency. Simulation results illustrate the mean-square error performance of the proposed method via numerical experiments

Wavelet preprocessing for automated neural network detection of EEG spikes

Abstract: The purpose of this study was to investigate the feasibility of using a wavelet transforms (WT) as a preprocessor for an artificial neural network (ANN) based EEG spike detection system. The study aimed at decreasing the input size to the ANN detector, without decreasing the information content of the signal and degrading the detection performance. Since routine clinical EEG requires recordings from many channels (generally 32 or 64), input size becomes a critical design parameter for real-time multichannel spike detection systems. For a sliding window of 20 points, more than 600 input lines will be necessary for a 32-channel system, which is not easily manageable with current ANN technology. One approach to this problem is to use a single ANN module for each EEG channel and integrate the outputs across channel information with a second module. The authors have successfully developed a 16 channel prototype of such a system working in real-time. This system used a 20 point (100 ms) sliding time window and employed a floating point digital signal processor for real-time operation. Adding more channels to this system would be difficult for real-time operation. In addition, the authors' recent studies showed that the best detection performance is attained with a 30 point (150 ms) time window, further increasing the computational load. Thus, the development of a preprocessor to reduce the input size without significantly reducing the information content would be very helpful in developing large multichannel EEG spike detection systems. >

Distributed assignment algorithms for multihop packet radio networks

Abstract: New distributed dynamic channel assignment algorithms for a multihop packet radio network are introduced. The algorithms ensure conflict-free transmissions by the nodes of the network. The basic idea of the algorithms is to split the shared channel into a control segment and a transmission segment. The control segment is used to avoid conflicts among nodes and to increase the utilization of the transmission segment. It is shown how these algorithms can be used in order to determine time-division multiple access (TDMA) cycles with spatial reuse of the channel. >

Performance analysis of cellular mobile communication systems with dynamic channel assignment

Abstract: The traffic analysis of small-cell mobile networks with dynamic channel assignment is investigated to determine their blocking performance, using a hybrid method of analysis and simulation. The authors particularly focus on the performance problems presented by networks with heterogeneous cell traffic loads, the impact of traffic volatility among the cells, and the impact of multichannel traffic on the channel blocking probabilities. Significant improvement in network performance with dynamic channel assignment is established by numerical results. >