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.

Algorithms for communications systems and their applications

Abstract: Preface. Acknowledgements. Elements of signal theory. The Wiener filter and linear prediction. Adaptive transversal filters. Transmission media. Digital representation of waveforms. Modulation theory. Transmission over dispersive channels. Channel equilization and symbol detection. Orthogonal frequency division multiplexing. Spread spectrum systems. Channel codes. Trellis coded modulation. Precoding and coding techniques for dispersive channels. Synchronization. Self--training equalization. Applications of interference cancellation. Wired and wireless network technologies. Modulation techniques for wireless systems. Design of high speed transmission systems over unshielded twisted pair cables. Index.

Method and apparatus for enabling group communication services in an existing communication system

Abstract: An apparatus to form a group of communication devices over a distributed network is claimed. A first node establishes a first channel with a first communication device. At least one second node establishes at least one second channel with at least one second communication device. A controller electrically connected to the first node and the at least one second node comprises a database module. The database module comprises identification information of each of the communication devices of the group. The controller is dynamically configurable such that any single communication device of the group is capable of sending packet data through its respective channel to the other communication devices of the group.

Capacity maximizing MMSE-optimal pilots for wireless OFDM over frequency-selective block Rayleigh-fading channels

Abstract: The location, number, and power of pilot symbols embedded in multicarrier block transmissions over rapidly fading channels, are important design parameters affecting not only channel estimation performance, but also channel capacity. Considering orthogonal frequency-division multiplexing (OFDM) systems with decoupled information-bearing symbols from pilot symbols transmitted over wireless frequency-selective Rayleigh-fading channels, we show that equispaced and equipowered pilot symbols are optimal in terms of minimizing the mean-square channel estimation error. We also design the number of pilots, and the power distributed between information bearing and pilot symbols, using as criterion a lower bound on the average capacity. Numerical results corroborate our theoretical findings.

Automatic Secret Keys From Reciprocal MIMO Wireless Channels: Measurement and Analysis

Abstract: Information theoretic limits for random key generation in multiple-input multiple-output (MIMO) wireless systems exhibiting a reciprocal channel response are investigated experimentally with a new three-node MIMO measurement campaign. As background, simple expressions are presented for the number of available key bits, as well as the number of bits that are secure from a close eavesdropper. Two methods for generating secret keys are analyzed in the context of MIMO channels and their mismatch rate and efficiency are derived. A new wideband indoor MIMO measurement campaign in the 2.51- to 2.59-GHz band is presented, whose purpose is to study the number of available key bits in both line-of-sight and nonline-of-sight environments. Application of the key generation methods to measured propagation channels indicates key generation rates that can be obtained in practice for four-element arrays.

A physical model of the wireless infrared communication channel

Abstract: A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht's integrating sphere. When a LOS component is also present, the transfer function depends upon the Rician factor K given by the ratio of the electrical power in the LOS and diffuse signals after the detector. For small K, the transfer function shows notches down to low frequencies, but due to the nature of light never for zero frequency. We confirm that a K-factor /spl ges/13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s. Increasing the directivity at the receiver and/or at the transmitter improves the effective value of K. Here, we show that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios.