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Broadband power line communication (BPLC) network is an excellent infrastructure for high speed data transmission. In this paper, the Orthogonal Frequency Division Modulation (OFDM) system in the Broadband power line communication and the effects of the cyclic prefix (CP) in such an OFDM system are investigated. An expression of signal to interference and noise rate (SINR) is presented as a function of delay, OFDM symbol length and CP length. Simulation results demonstrate that in order to achieve an ideal SINR, CP and the OFDM symbol should be long enough compared with the delay of the channel.

The Fast Fourier Transform and Inverse Fast Fourier Transform (FFT/IFFT) are the most significant digital signal processing (DSP) techniques used in Orthogonal Frequency Division Multiplexing (OFDM)-based applications which include day-to-day wired/wireless communications, broadband access, and information sharing. The advancements in telecommunication technologies require an efficient FFT/IFFT processing device to meet the necessary specifications which depend on the particular application. A real-time implementation of high-speed FFT/IFFT processor with less area that operates in minimal power consumption is essential in designing an OFDM integrated chip. A comparative study of efficient algorithms and architectures for FFT chip design is presented in this paper. It is also recommended that mixed-radix/higher-radix algorithm combined with Single-path Delay Commutator (SDC) architecture is appropriate for massive MIMO in 5G, optical OFDM, cooperative MIMO and multi-user MIMO-based applications.

This work describes a new design approach for a four-stage ring Voltage-Controlled Oscillator (VCO) for Orthogonal Frequency Division Multiplexing (OFDM) systems, which is ideal for low-phase noise and low-power applications. The phase noise of the proposed ring VCO has been improved by limiting the delay cell’s output current to a relatively narrow portion of the output waveform, and the complementary nature of the delay cell prevents the power from increasing substantially. The proposed VCO is designed and simulated in GPDK 90nm CMOS technology using Cadence Virtuoso under 1.0V power supply. A tuning frequency range of 112–362MHz is obtained with control voltage ranges 0.0–1.0V. The proposed ring VCO consumes 1.07mW of power. At a 1MHz offset frequency, phase noise reduction is achieved to $-109.36$dBc/Hz. The proposed design is also validated by the Process–Voltage–Temperature (PVT) analysis. The proposed VCO has a Figure of Merit (FOM) of $-160.24$dBc/Hz and acquires a total area of 0.00085mm².

Digital watermarking is a process of embedding hidden information called watermark into different kinds of media objects. It uses basic modulation, multiplexing and transform techniques of communication for hiding information. Traditional techniques used are least significant bit (LSB) modification, discrete cosine transform (DCT), discrete wavelet transform (DWT), discrete Fourier transform (DFT), code division multiple access (CDMA) or a combination of these. Among these, CDMA is the most robust against different attacks except geometric attacks. This paper proposes a blind and highly robust watermarking technique by utilizing the basis of orthogonal frequency division multiplexing (OFDM) and CDMA communication system. In this scheme, the insertion process starts by taking DFT of host images, permuting the watermark bits in randomized manner and recording them in a seed as a key. Then PSK modulation follows inverse DFT (IDFT) that gives watermark information as OFDM symbols. These symbols are spread using spreading codes and then arithmetically added to the host image. Finally, scheme applies inverse DCT (IDCT) to get watermarked host images. The simulation results of the proposed scheme are compared with CDMA-based scheme in DCT domain. The results show that the robustness of the proposed scheme is higher than the existing scheme for non-geometric attacks.

The connection to the Internet by full-mobile users, is expected to be of crucial importance for the success of radio mobile systems as UMTS. Such systems must support services like Web Browsing, the most popular Internet application today, which is characterized by high bit rate bursty asymmetric traffic and like Video Call, evolution of traditional speech service, which are characterized by high sensitivity to delays and more symmetric traffic.

While the resulting traffic is highly asymmetric, mobile air interfaces like UTRAN FDD have been initially designed as systems supporting asymmetric user traffic in an overall system symmetric traffic scenario.

This paper, outcome of the ongoing EU founded project OverDRiVE, focuses on downlink enhancements of the UTRAN FDD air interface and proposes specific resource management of additional radio spectrum in order to handle efficiently asymmetric traffic.

In this paper, we focus on preamble-based time of arrival (TOA) estimation for orthogonal frequency division multiplexing (OFDM) systems in non-line-of-sight (NLOS) environments. Recent development in wireless communication-based positioning systems exploiting TOA methods faces a major challenge for the TOA estimation in NLOS condition. Because of the possible obstruction of the direct path, the signal component from direct propagation can be very weak and therefore, the performance of TOA estimation will be dramatically degraded. An accurate TOA estimation utilizing channel estimation is presented. The proposed approach consists of three stages. First, we obtain coarse integer TOA estimation by correlation detection. Second, Maximum-likelihood criterion is employed in channel impulse response estimation to get the fine integer TOA estimate. We exploit the multipath interference cancellation with channel equalization in frequency domain. Finally, to break the limitation by sampling interval, fractional TOA estimate by linear fit is obtained. Compared with the off-the-shelf method, the simulation results show that our method achieves more precise TOA estimation.