Improvement of the Communication between RFID Sensor Network Devices Used to Control and Monitor a Building

In the RFID sensor network (RSN), the devices communicate with each other by RF waves using the antennas through a propagation channel. A poor communication between these devices results in either a significant economic loss or security threats. The communication problems can have several origins depending on the type of antenna used and the nature of the propagation channel. In this work, our objective is to limit the communication problems between the nodes of this network that are linked to the characteristics of an indoor propagation channel. The goal is to predict the channel characteristics using the 3D ray tracing method in order to select the appropriate transmission parameters such as transmission power and duration of a symbol. To achieve this, we have modeled a building that is sectioned as a propagation channel where network devices are deployed for control and monitoring. The communication was made at 915 MHz using the quasi-isotropic 3D cubic antenna that we designed as well as a conventional dipole antenna in order to compare the results. We have found that the use of the 3D cubic antenna gives several advantages to the RFID sensor network compared to the most commonly used conventional dipole antenna, such as a transmission power of 0 dBm which automatically leads to an increase in the lifetime of the devices, as well as a minimum symbol duration of around 219.78 ns which gives a high bit rate.

Inner-symbol Interference (INSI) reduction in OFDM system using distinctive characteristics of the pilot symbols

This research presents a wireless communication system using Quadrature Amplitude Modulation (16QAM) depending on using of the Orthogonal Frequency Division Multiplexing (OFDM). OFDM transmission system can effectively reduce inter symbol interference (ISI) caused by multipath fading, especially in the case of broadband data transmission. There are two kind of interference; inter symbol interference (ITSI) and inner symbol interference (INSI). ITSI is the interference caused by the delayed waves with larger than OFDM symbol duration, in order to avoid ITSI effectively, we insert guard interval every each OFDM symbol. On other hands, INSI is the interference caused by the delayed waves with less than OFDM symbol duration. To avoid INSI, this work proposes a new scheme in order to estimate the times of delayed waves by using distinctive characteristics of OFDM signal, which is inserted pilot signal periodically in frequency axis before IFFT at the transmitter. In this paper, we evaluate the estimation accuracy of the proposed estimation method and the BER performance of the proposed system under multipath fading environment by computer simulation with MATLAB.

Autocorrelation Method for Cyclic Prefix OFDM Estimation

A radio system design providing various data service needs becomes one of the Software Defined Radio (SDR) system advantages. SDR technology applies software functions further to be run in hardware platforms. The need for services with greater data rates can be resolved by using multi-carrier transmission techniques, one of which is the Orthogonal Frequency Division Multiplexing (OFDM) technique. This paper discusses the detection of OFDM signals and their parameters. Multi-carrier transmission can prevent Inter-Symbol Interference (ISI) occurrence due to multi-path fading effect. The recognition can classify the correctly received signals, including the signal conditions mixed with AWGN noise. The autocorrelation method was used to estimate the OFDM parameters, namely the one symbol duration and the cyclic prefix duration. The detected cyclic prefix durations were 1/2, 1/4, 1/8, and 1/16. This method is very simple, because with the cyclic prefix presence, a different signal peak will be detected to further estimate the cyclic prefix duration. The results show the correlation method performance can detect one symbol duration with 100%, accuracy, starting at SNR 0 dB, whereas the cyclic prefix duration accuracy rate is getting more accurate by using a less cyclic prefix duration, which is 1/16 of the total symbol duration.

An Improved Channel Estimation Method in OFDM System

In this paper, we will focus on channel estimation (CE) in orthogonal frequency-division multiplexing (OFDM) systems. The time-varying (TV) channelsare modeled by a basis expansion model (BEM). Due to the time-variation, the channel matrix in the frequency domain is no longer diagonal, but approximately banded.We use a pilot-aided algorithm for estimation of rapidly varying wireless channels in OFDM systems. Theperforms is goodwhen the channels vary on the scale of a single OFDM symbol duration, which occurs in mobile communication scenarios such as WiMAX, WAVE, and DVB-T.We recover Fourier coefficients of the channel taps by the pilot information.We then estimate the BEM coefficients of the channel taps from their respective Fourier coefficients using a recently developed inverse reconstruction method.We compare some BEM models in inverse methodsto find out the best ones in certain conditions.

OFDM Parameter Design of a Digital Broadcasting System in FM Band

A thorough OFDM parameter design method of a digital broadcasting system in FM band is presented in this paper. Key OFDM parameters are analyzed from their constraints. Cyclic prefix should satisfy the requirement of channel delay and formation of SFN. Design of system bandwidth should consider coherent bandwidth and existing frequency planning. Symbol duration is restricted by time selectivity and frequency selectivity of the channel, and also efficient SINR should be maximized. System simulation is performed to test and verify the parameters under typical FM band channels. A set of OFDM parameter is provided for future design.