No abstract

The propagation channel is the principal contributor to many of the problems and limitations that degrades the performance of mobile radio systems. One obvious example is multipath propagation which is a major characteristic of the mobile radio channels, which severely affects the performance of digital systems by reducing the carrier-to-interference ratio. Thus accurate characterization of the propagation channel is very important for cost effective planning of Land Mobile Communication System. This paper presents a simplified technique for modeling radio propagation channel applicable for microcellular environment. Two propagation channel models have been considered. These are statistical theory based Suzuki Model and deterministic Uniform Theory of Diffraction (UTD) based Ray Tracing model, to predict received signal in the microcellular environment. The various statistical parameters such as, cumulative distribution function (cdf), level crossing rate (lcr) and average duration of fade (adf) were obtained from the total received signal to characterize the propagation channel using both the models. The comparison of these characteristics is summarized which indicates the good agreement of statistical and deterministic models.

Selecting an appropriate substrate material for the design of microstrip patch antenna for various applications is a very important step in antenna design. This paper presents a work of various substrates materials used for the design of low cost inset feed rectangular microstrip antenna for WLAN, WiMax, LTE, C-band and X-band applications. The substrates used are FR-4 epoxy, foam, polyethylene terephthalate (PET) and polydimethylsiloxane (PDMS). The antennas were designed, optimized and simulated using HFSS 15.0. Return loss, voltage standing wave ratio and gain analysis is carried out for these antennas. The measurement of reflection coefficient of the fabricated antennas is done using Agilent PNA-L series vector network analyzer. The simulated and measured results are well in agreement. The analysis show that antenna with foam substrate offers the lowest return loss of - 41.28 dB. Larger bandwidth and gain of 4.38 dB is observed with PET substrate.

The mobile radio channel places strong limitations on the performance of wireless communication systems because the transmission principle in wireless communication is more complex than those of the wired networks. In this paper we discuss the radio propagation with an objective to provide an overview of various characteristics of radio channel and an understanding of the process and factors that influences these characteristics. Section I describe a typical outdoor scenario for terrestrial mobile radio channel and principle causes of information loss (multipath fading). Section II presents the various radio channel characteristics like path loss which is used to denote the local average received signal power relative to the transmit power and helps in providing the information on coverage area. Other higher order statistical characteristics such as level crossing rate (lcr) and average duration of fade (adf), which relates the time rate of change of the received signal to the signal level and velocity of the mobile, are also considered to study the influence of short term fading on the performance of the wireless system. Section III contains the observed path loss and its comparison with the simulated path loss propagation models. Lcr and adf are obtained from the received signal envelop in section IV to study the system performance. The simulated results obtained in section III and section IV provide valuable information on coverage area, and choice of suitable data rate, word length, modulation, and coding schemes as stated in table1. General TermsRadio wave propagation, Mobile communication.

In this paper we have emphasized on the short term fading of the mobile communication channel and made an attempt to investigate its influence on the performance of mobile communication system. Level crossing rate and average duration of fade are considered to characterize the fast fading nature of channel. Other factors like carrier frequency, speed of the mobile have been investigated and found that BER performance of the system is greatly influenced by multipath fading.