Land Mobile Satellite Communication Channel Research Articles

Performance analysis of MC DS-CDMA with generalized selection combining over land mobile satellite communication channels

Performance analysis of MC DS-CDMA with generalized selection combining over land mobile satellite communication channels

Multiple-symbol differential detection of /4-DQPSK in land mobile satellite communication channels

Multiple-symbol detection of π/4-DQPSK in land mobile satellite communications (modelled as correlated Rician fading) is studied. Metrics for maximum likelihood detection are derived. For the no channel-information case, the generation of the metric can be implemented as a multiple-symbol differential detector. For the ideal channel-information case, however, the generation of the metric cannot be implemented as a multiple-symbol differential detector. The BER performances of this scheme are evaluated through the union bounds of pairwise bit error probabilities and Monte Carlo simulation for both cases. It has been found that in light or medium fading Rician channels, about 1.0 dB gain for Eb/No at BER = 10-4 can be achieved by using four-symbol detection instead of conventional two-symbol detection. The gain is greater than 1 dB when the BER is lower. It is also demonstrated that multiple-symbol differential detection actually increases the BER for severe fading Rician channels (K < 10.5 dB) or Rayleigh channels if no channel information is available. However, with ideal channel information, the multiple-symbol detection can reduce the BER at high Eb/No. The influence of different fading rates on the BER performance is also evaluated, showing a lower BER at a lower fading rate, as expected.

Satellite-PCS channel simulation in mobile user environments using photogrammetry and Markov chains

In this paper, we present a system that models the land-mobile satellite communication channel with a Markov chain approach supported by images of the mobile Earth station's (MES) environment. Our method employs a video camera with a fish-eye lens capturing image sequences of the user environment from the position of the moving MES, image and signal processing algorithms to recognize propagation path states and extract their duration and transition probabilities, and modeling of the communication channel characteristics using the theory of Markov stochastic processes combined with statistical fade distributions appropriate for given path states. The results demonstrate that the procedure provides a full statistical characterization of the narrow-band land-mobile satellite propagation channel in several environments.

Trellis‐coded dpsk with multiple‐symbol viterbi decoding over mobile satellite channel at K and L bands

AbstractMobile satellite communication systems at Ka/K band (30/20 GHz) are attractive because of their large bandwidth availability and potentiality to support smaller earth‐stations and satellite antennas compared with L‐band (1·6/1·5 GHz) systems. In this paper, multiple‐symbol Viterbi decoding and dual‐space equal‐gain diversity reception for trellis‐coded differential M‐ary phase‐shift‐keying (DPSK) modulation are investigated as two mitigation techniques for severe channel impairments expected from a land mobile satellite communication channel at K band and, for comparison purposes, at L band. The multiple‐symbol Viterbi decoder (MSVD) is a modified Viterbi decoder with inputs from multiple differential detectors. The channel is modelled as Rayleigh distributed multipath fading with a lognormally distributed line‐of‐sight (LOS) component due to shadowing. Four trellis‐coded modulation (TCM) schemes are studied. The dependency of the system performance improvement on the decoder structure, the TCM scheme, and the system RF frequency band is presented.

Land mobile satellite communication channel model for simultaneous transmission from A land mobile terminal via two separate satellites

AbstractThere are certain data services that could use transmit‐only land‐mobile satellite communication terminals. Such terminals would not be able to receive acknowledged messages and transmit them onward. Thus it is of interest to study alternative means of improving the system reliability. In this paper we propose the use of transmission to two satellites separated in azimuth and elevation in order to improve the reliability of throughput.We have investigated the improvements by building upon the model proposed by Lutz for land mobile satellite communications via one satellite, and extended this using measurements of the shadowing coefficient in different areas (suburban, countryside and city) to two separated satellites. The measured data is used to produce an empirical model of the equivalent shadowing coefficient variations with the separation angle variation between two satellites.The results show good agreement with the shadowing coefficients produced by the Lutz model for a single satellite. The degree of improvement produced by using two separated satellites in the different environments, in terms of bit rate and probability of the received power is given.

The land mobile satellite communication channel-recording, statistics, and channel model

The communication channel between the MARECS satellite at 26 degrees W and a cruising van was measured and recorded in European areas exhibiting satellite elevations from 13 to 43 degrees . Different environments and mobile antennas were tested. The results of an extensive statistical evaluation include spectra of the fading amplitude; probability density, and distribution of the received signal power; and the percentage of time for fade and nonfade periods. Based on the physical phenomena of multipath fading and signal shadowing, an analog model of the land mobile satellite channel which can readily be used for software and hardware fading simulation is developed. The most important parameter of this model is the time-share of shadowing. The Rice factor which characterizes the channel during unshadowed periods, can vary from 3.9 to 18.1 dB. Block error probability density, error gap distribution, and block error probability are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

PSK and DPSK trellis codes for fast fading, shadowed mobile satellite communication channels

The performance of 8-PSK and 8-DPSK trellis codes is presented for a class of fast fading, land mobile satellite communication channels. The fading model is Rician but, in addition, the line-of-sight path is subjected to a fast lognormal attenuation that represents tree shadowing. The fading parameters used in this study represent the degree of shadowing and are based on measured data. The primary application considered is for digital speech transmission and thus, bit error probabilities in the order of 10/sup -3/ are emphasized. Sensitivity of the bit error probability to amplitude fading, amplitude and phase fading, and decoding delay is presented. Performance is determined via digital computer simulation. Optimal four- and eight-state codes are determined and optimality is found to be dependent on the presence of lognormal shadowing. >