Showing papers on "Channel state information published in 1981"

More on the Multipath Fading Channel Model

Abstract: Selective fading due to muitipath on a typical narrowband line-of-sight microwave radio path is represented with a simplified three-ray model. This model provides a satisfactory description of the frequency transfer characteristics of almost all fades observed during three separate propagation experiments. Data were obtained for a 30 MHz bandwidth at 6 GHz using both a standard horn reflector and a parabolic dish, and for a 20 MHz bandwidth at 4 GHz using the horn. The statistics of the parameters of the model were found to be substantially the same for all three cases. The incidence of selective fading scales, within a factor of two, with the incidence of fading at a single frequency, for 1-month observation intervals.

Performance of a frequency-hopped differentially modulated spread-spectrum receiver in a Rayleigh fading channel

Abstract: The performance of a spread-spectrum receiver previously described by the authors is analyzed in detail. Performance curves are given for a wide range of mobile radio channel conditions, including multipath distortion and correlated fading. The use of optimal filters to combat the former and space diversity to combat the latter are investigated. Some errors in the authors' earlier papers are corrected. The form of space diversity suggested has the unusual feature that it can be employed at the fixed station site only and provide diversity in both communication paths, i.e., to and from the mobile. Degradation due to fading and other aberrations is shown to be in the range 3-6 dB for typical mobile channel conditions. In a nonfading channel the receiver is suboptimum by about 3 dB.

Modeling multlipath fading responses using multitone probing signals and polynomial approximation

Abstract: We show in quite a general way that highly accurate modeling of multipath fading responses is possible using low-order complex polynormals. This applies to all terrestrial radio systems in the channelized common carrier bands below 15 GHz, where channel widths are 40 MHz or less. The context of the study is a new multipath experiment being conducted in New Jersey over a 23-mile path at 11 GHz. The transmitted signal consists of up to nine tones in a 40-MHz bandwidth. These tones are coherently processed, sampled, and digitized in the receiver and recorded, during fading events, for later off-line reductions. Simple routines can be used to determine polynomial coefficients from these recorded data. This paper describes the signal processing and data reduction methods and analyzes them to assess the accuracy of polynomial fitting. The analysis uses a mean-square error measure and assumes a representative form for the underlying response function. Our results predict that the vast majority of multipath fading responses can be accurately approximated over bandwidths of 40 (62) MHz using first- (second-) order complex polynomials.

Spectrally Efficient Communication via Fading Channels Using Coded Multilevel DPSK

Abstract: This paper investigates the use of multilevel differential phase-shift keying with forward error-correcting coding as a technique for achieving limited bandwidth, yet reliable communication over a class of fading channels. Error rate bounds based on the cutoff rate are computed to show that multilevel modulation can be used to allow significant coding gains, while maintaining or reducing the bandwidth of the transmitted signal.

Probability distributions for ratios of fading signal envelopes and their generalization

Abstract: This paper describes statistical characteristics of the ratios of fading signal envelopes. The Rayleigh fading is contained as a special case. We derive the ratios of the fading signals following the m distribution, generalized Nakagami-Rice distribution and generalized Nakagami-Hoyt distribution. An extension to the case of multiple variable distribution is attempted under some conditions. The results in this paper are given in simple functional forms appropriate for theoretical analysis. The distributions of the ratios of fading signal envelopes can be applied to a wide range of problems of radio wave interference such as evaluation of the ratio of desired signal to unwanted interference signal (DU ratio) and of degradation of cross-polarization discrimination (XPD) in a microwave transmission channel, determination of frequency reuse distance and of modulation types for mobile communications, and analysis of ratio detection in radar technology.