QPSK

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. Space-time wireless technology that uses multiple antennas along with appropriate signalling and receiver techniques offers a powerful tool for improving wireless
performance. More advanced MIMO techniques are planned for future mobile networks in wireless Local Area Network (LANs) and Wide Area Network (WANs). Multiple antennas when used with appropriate Space-Time Coding (STC) techniques can achieve huge performance gains in multipath fading wireless links. The Space Time Coding has evolved as a most vibrant research area in wireless communications. Recently, Space-Time Block Coding (STBC) has been trying to incorporate in the forthcoming generation of mobile communication standard which aims to deliver true multimedia capability. This paper presents the Space-Time Block Codes (STBC) for wireless networks that uses multiple numbers of antennas at both transmitter and receiver. The simulations have been done in MATLAB. The STBC which includes the Alamouti Scheme as well as an orthogonal STBC for 4 transmit antenna case has been simulated and studied.

Software defined radio (SDR) technology enables implementation of wireless devices that support multiple air-interfaces and modulation formats, which is very important if consider proliferation of wireless standards. To enable such functionality SDR is using reconfigurable hardware platform such as Field Programmable Gate Array (FPGA). In this paper, we present design procedure and implementation result of SDR based QPSK modulator on Altera Cyclone IV FPGA. For design and implementation of QPSK modulator we used Altera DSP Builder Tool combined with Matlab/Simulink, Modelsim and Quartus II design tools. As reconfigurable hardware platform we used Altera DE2-115 development and education board with AD/DA daughter card. Software and Hardware-in-the-loop (HIL) simulation was conducted before hardware implementation and verification of designed system. This method of design makes implementation of SDR based modulators simpler ad faster.

This paper presents performance evaluation of the different Modulation Schemes (BPSK, QPSK, GMSK) in terms of Bit
error rate (BER) in cellular mobile environment with GSM standard parameters. The main objective of this paper is to investigate the
factors that go into selection of the particular modulation scheme in the wireless environment. To analyze the cellular mobile
environment GSM standard is selected. There are a number of factors that enter into the choice of a modulation scheme for use in a
wireless application. Performance of a cellular system is dependent on the efficiency of the modulation scheme in use. Gaussian
channel model was used. The various modulation schemes like BPSK, QPSK, and GMSK will be simulated in SystemVue software.
After simulation of the all this, BER was carried out. Then using these parameters, the various modulation techniques were compared.

White LEDs are set to penetrate many areas of everyday life. An interesting property of these devices (in addition to their lightening capabilities) is that they can be utilised for data transmission. In the past, primarily OOK (on-off keying) has been used for digital data modulation of such devices. OOK imposes limitations on the achievable data rates. Therefore, in this paper OFDM is considered in combination with higher order modulation schemes. A hardware demonstrator with an entire link chain (transmitter and receiver) is developed and measured BER (bit error ratio) results are reported. The system uses pilot sub-carriers to correct frequency synchronisation errors, training sequences for channel estimation and time synchronisation routines. Forward error correction (FEC) coding is used. It is shown that for COFDM (coded OFDM) with QPSK (quadrature phase shift keying) modulation and a single LED, a BER of 2 times 10-5 is achieved for a distance of 90 cm between transmitter and...

ABSTRACT The paper presents the design and performance of a baseband modem for wireless LAN systems. The modem fully complies with the IEEE 802.11g standard draft 4.0. It is capable of operating in any of available modes such as ERP-DSSS/CCK, ERP-OFDM, Extended Rate PBCC, and CCK-OFDM. It offers different data rates from 1 Mbps to 54 Mbps and handles DBPSK, DQPSK, QPSK, 8-PSK, BPSK, 16-QAM, and 64-QAM modulation schemes. We show the BER performance of the presented modem as the result of simulation under AWGN and multipath channels.

This straightforward design shows how to assemble commercial components into a low-noise 14.4-to-15.5-GHz frequency synthesizer with 625-kHz tuning steps for digital microwave radio systems. ______________________________________________________________________________ Frequency synthesizers are an essential part of modern digital-microwave-radio (DMR) communications systems. With new ITU-R recommendations for DMR communications bands at 15, 18, 23, 38, and 55 GHz, frequency synthesizers are needed for use as local oscillators (LOs) for the frequency upconversion chores in transmitters and the frequency downconversion in receivers for a variety of different frequency architectures. The design of a Ku-band (14.4 to 15.5 GHz) frequency synthesizer offers practical benefits for several of these bands, since with multiplication by four it can be made to provide frequency coverage as high as 60 GHz. The programmable frequency synthesizer, which switches in 625-kHz steps and can be used with quadrature phase-shift-keying (QPSK) and quadrature-amplitudemodulation (QAM) transmission schemes, is a straightforward design that features low phase noise and reliable operation using commercially available oscillator and phase-lockloop (PLL) integrated circuits (ICs). The PLL concept was developed in the 1920s. 1 The technology has been widely used in a variety of communications systems but until recently, has been too costly and complicated for use in many consumer and industrial applications. But with the growing availability of PLL ICs, the technology is economical enough for most systems. One main area of interest for applying PLLs is in oscillators, to stabilize output frequencies and lower noise levels. 2-4 In addition, DMRs represent a growing market for PLLs. DMRs and other high-capacity digital communications systems require low-cost but high-quality frequency sources. Frequency synthesizers provide stable local oscillator (LO) signals for microwave transceivers, supporting frequency upconversion for transmit operation and frequency downconversion for receive operation. Synthesizer noise is particularly critical in such applications since a digital radio link is sensitive to phase noise. 5-7 The phase noise is detected in such a system along with desired modulated signals. Excessive phase noise degrades the DMR system's biterror-rate (BER) performance.

Mobile WiMAX standard defines air interface for mobile broadband wireless access (BWA) systems and aimed to provide high data rate with seamless mobility while maintaining the quality of service (QoS). However, QoS of real - time applications depends on the link quality, which necessitate the channel -aware
connection admission control (CAC) and scheduling schemes. In this paper Modulation aware CAC scheme and base station (BS) uplink scheduling algorithm are proposed to improve the system capacity and QoS performance respectively. The proposed CAC scheme aims to increase the admission of higher priority real time services by degrading the bandwidth of admitted lower priority connections on the basis of their channel status without deteriorating their QoS performance much. The performances of proposed algorithms are evaluated through simulation by considering the metrics like throughput, delay and number of connections admitted
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In this paper we propose the method for the detection of Carrier-in-Carrier signals using QPSK modulations. The method is based on the calculation of fourth-order cumulants. In accordance with the methodology based on the Receiver Operating Characteristic (ROC) curve, a threshold value for the decision rule is established. It was found that the proposed method provides the correct detection of the sum of QPSK signals for a wide range of signal-to-noise ratios and also for the different bandwidths of mixed signals. The obtained results indicate the high efficiency of the proposed detection method. The advantage of the proposed detection method over the "radiuses" method is also shown.

This paper presents a tool for the analysis, and simulation of direction-of-arrival estimation for MIMO OFDM signal over the Rayleigh fading channel. The performance of the proposed technique is tested for wavelet denoising based CYCLIC MUSIC algorithm. Simulation results demonstrate that the proposed system not only has good ability of suppressing interference, but also significantly improves the DOA estimation of the system. In this paper, it is proposed to find DOA of the received MIMO OFDM signal, and the performances are analyzed using matlab simulation by the Monte Carlo computer iteration. This paper provides a fairly complete image of the performance and statistical efficiency with QPSK signal model for coherent system at a lower SNR(18dB) and interference environment.

Worldwide Interoperability for Microwave Access (WiMax), standardized asIEEE 802.16d is a popular technology for broadband wireless communication system. Orthogonal Frequency Division Multiplexing (OFDM) is the core of this technology.OFDMreduces Inter-symbol Interference (ISI) and hence improves system performance (i.e., Bit Error Rate (BER)). To improve system performance further error correction coding schemes have been included in WiMax. It is widely accepted thata coded system outperforms an uncodedsystem. But, the performance improvement of a coded system depends on the channel conditions. In this paper, we investigated and compared the performances of a coded and an uncoded WiMaxsystem under a practical channel model called Stanford University Interim (SUI). Different modulation schemes namely BPSK, QPSK, 16-QAM, and 64-QAM have been considered in this work. It is shown that the selection of codedoruncoded WiMaxsystem should depend on the channel condition as well as on the modulation used. It is also shown that anuncoded system outperforms a coded system under some channel conditions.

This paper presents a comparative performance analysis of wireless orthogonal frequency division multiplexing (OFDM) system with the implementation of comb type pilot-based channel estimation algorithm over frequency selective multi-path fading channels. The Minimum Mean Square Error (MMSE) method is used for the estimation of channel at pilot frequencies. For the estimation of channel at data frequencies different interpolation techniques such as low-pass, linear, and second order interpolation are employed. The OFDM system simulation has been carried out with Matlab and the performance is analyzed in terms of bit error rate (BER) for various signal mapping (BPSK, QPSK, 4QAM, 16QAM, and 64QAM) and channel (Rayleigh and Rician) conditions. The impact of selecting number of channel taps on the BER performance is also investigated.

Future wireless communication system have to be designed to integrate features such as high data rates, high quality of service and multimedia in the existing communication framework. Increased demand in wireless communication system has led to demand for higher network capacity and performance. Higher bandwidth, optimized modulation offer practically limited potential to increase the spectral efficiency. Hence MIMO systems utilizes space multiplex by using array of antenna’s for enhancing the efficiency at particular utilized bandwidth. MIMO use multiple inputs multiple outputs from single channel. These systems defined by spectral diversity and spatial multiplexing. The aim of this paper is to design and implement of channel estimation method and modulation technique for MIMO system. The design specifications are obtained using MATLAB. The RTL coding is carried for the design to be implemented on Xilinx FPGA.

Starting with an ordinary parallel concatenated turbo encoder in a block fading Rayleigh channel, we introduce bit-interleaving of the outputs, not for time diversity, but to increase the coding gain. We develop a guideline metric for designing QPSK space-time codes which reveals both the coding and diversity advantage of the systems as well as showing that it is unnecessary to guarantee full space diversity to achieve good performance in Rayleigh fading. Using channel a priori information in the MAP iterations for decoding, we achieve frame error rates within 1 dB of the outage probability with only modest increases in decoding complexity.

This paper presents a tool for the analysis, and simulation of direction-of-arrival (DOA) estimation in wireless mobile communication systems over the fading channel. It reviews two methods of Direction of arrival (DOA) estimation algorithm. The standard Multiple Signal Classification (MUSIC) can be obtained from the subspace based methods. In improved MUSIC procedure called Cyclic MUSIC, it can automatically classify the signals as desired and undesired based on the known spectral correlation property and estimate only the desired signal’s DOA. In this paper, the DOA estimation algorithm using the de-noising pre-processing based on time-frequency conversion analysis was proposed, and the performances were analyzed. This is focused on the improvement of DOA estimation at a lower SNR and interference environment. This paper provides a fairly complete image of the performance and statistical efficiency of each of above two methods with QPSK signal.

Abstract-This paper concerns the Cramer-Rao lower bound (CRB) for the data-aided (DA) , the DA parameter esti- mation, the CRB typically varies with the training sequence. This indicates that different training se- quences offer fundamental different performance. In this manuscript, we derive a closed-form formula of the CRB for timing and phase recovery with respect to any particular training sequence.

Orthogonal Frequency-Division Multiplexing (OFDM) is essentially identical to coded OFDM (COFDM) and discrete multi-tone modulation (DMT). It is a frequency-division multiplexing (FDM) scheme, which is used as a digital multicarrier modulation method. The paper is aimed at analyzing the BER performance of the MIMO (Multi-Input Multi-Output) OFDM system for AWGN (Additive White Gaussian Noise) Channel, Rayleigh Fading Channel along with a simulation channel using different modulation technique. Also the result of the analysis suggest for the better technique in order to improve the BER characteristic of the MIMO-OFDM system.

In this thesis paper, first build up a wireless communication simulator including Gray coding, modulation, different channel models (AWGN, flat fading and frequency selective fading channels), channel estimation, adaptive equalization, and demodulation. Next, test the effect of different channel models to the data and image in receiver with constellation and BER (bit error rate) plots under 4QPSK modulation which is a high data rate then QPSK. For Image data source, we also compare the received image quality to original image in different channels. At last, give detail results and analyses of the performance improvement with channel estimation and adaptive equalization in slow Rayleigh fading channel. For frequency selective fading channel, use linear equalization with both LMS (least mean squares) and RLS (Recursive Least Squares) algorithms to compare the different improvements. We will see that in AWGN channel, the image is slight degraded by random noise; in flat fading channel,...

A comprehensive set of acoustic communication data is analyzed using a complete receiver algorithm which includes a Doppler pre-processor, equalizer configuration algorithm and the decision feedback equalizer (DFE). The signal used for the tests is 1250 symbol per second QPSK (2500 bps) transmitted at a carrier of 2.25 kHz. Source-receiver ranges of up to 44 km were achieved at this data rate. The test environments include the New England Continental Shelf (less than 200 m), the shelf break (200-1200 m) and deep water (2500 m). In each environment the impulse response, the ambiguity function and the performance level of the receiver are presented. The link was very reliable to the maximum test range of 44 km on the shelf and to 20 km at the shelf break. In deep water the performance was good at less than 10 km and also at 35-44 km