Programmable digital modem

The design of the Programmable Digital Modem (PDM) is outlined. The PDM will be capable of operating with numerous modulation techniques including: 2-, 4-, 8- and 16-ary phase shift keying (PSK), minimum shift keying (MSK), and 16-ary quadrature amplitude modulation (QAM), with spectral occupancy from 1.2x to 2x the data symbol rate. It will also be programmable for transmission rates ranging from 2.34 to 300 Mbit/s, where the maximum symbol rate is 75 Msymbol/s. Furthermore, these parameters will be executable in independent burst, dependent burst, or continuous mode. In dependent burst mode the carrier and clock oscillator sources are common from burst to burst. To achieve as broad a set of requirements as these, it is clear that the essential signal processing must be digital. In addition, to avoid hardware changes when the operational parameters are changed, a fixed interface to an analog intermediate frequency (IF) is necessary for transmission; and, common system level architectures are necessary for the modulator and demodulator. Lastly, to minimize size and power, as much of the design as possible will be implemented with application specific integrated circuit (ASIC) chips

Development of universal software radio peripheral amplifier for underwater acoustic platform using software defined radio

First and foremost, the development of a modem using the USRP has applications in oceanographic monitoring and communication. Improved acoustic connecting would allow more efficient transfer of information between Underwater Acoustic (UWA) equipment such as autonomous vehicles, piloted vehicles, and underwater profilers. Therefore it can easily be modified in order to be employed for the testing of different UWA. This project describes the full system of an underwater acoustic modem with underwater wireless connection starting with the most critical component of the system which is the USRP amplifier for the receiver and the transceiver. In this project we focused on the development of the USRP amplifier. This amplifier is expected to enhance the signal of the transceiver to Universal Software Radio Peripheral (USRP) modem and the GNU radio. The platform that we proposed uses the Software Defined Radio (SDR) as the main controller. This is due to its flexibility in modulation and able to support coding. Since this is an initial stage, in this work we only use Gaussian Minimum Shift Keying (GMSK) as the modulation techniques. The performance of the UWA platform had been tested and we found that as the frequency increases the attenuation increased as well but with the USRP amplifier we have managed to decrease it. UWA communication research will benefit greatly from the adaption of the USRP as an underwater acoustic modem. The USRP amplifier amplifies the signal that has send by the transceiver and detected by the receiver will effectively demodulate the signal and analyze the received data in the USRP modem. GNU radio and USRP SDR has been successfully implemented. The results demonstrate that the objectives of this research are archived. It is proved that by implementing GNU radio and USRP SDR in the new generation of underwater acoustic communication technology, and improves the utilization of the underwater communication. We conclude that the proper design of the USRP Amplifier is crucial to obtain high quality performance. This project has successfully developed a USRP amplifier and the underwater acoustic communication testbed with expected results

Coded 16-CPFSK for downlink applications

A bandwidth-efficient constant-envelope Proof-of-Concept (POC) modem is described. The modem was developed on an Advanced Modulation Techniques Development contract for the NASA/Lewis Research Center. The POC modem employs 16-ary Continuous Phase Frequency Shift Keying (16-CPFSK) modulation. The 16 frequencies are spaced every 1/16th baud rate which produces a compact spectrum allowing 2 bits/sec/Hz operation. The modem is designed for 200 mb/s Time Division Multiple Access (TDMA) application with 100 MHz adjacent channel spacing. Overall rate 3.4 convolutional coding is incorporated. The demodulator differs significantly from typical quadrature phase detector approaches in that phase is coherently measured by processing the baseband output of a frequency discriminator. Baud rate phase samples for the baseband processor are subsequently decoded to yield the original data stream. The method of encoding onto the 16-ary symbol-ending phase nodes, together with convolutional coding gain, results in near Quadrature Phase Shift Keying (QPSK) theoretical performance. The modulated signal is of constant envelope; thus the power amplifier can be saturated for peak performance. The spectrum is inherently bandlimited and requires no RF filter for sidelobe containment. Two novel theoretical techniques are used in this 16-CPFSK modem: (1) coherent phase measurements are obtained by processing an FM discriminator baseband output; and (2) modulation is accomplished via a closed-loop-linearized voltage controlled oscillator (VCO)

An 8-DPSK TCM modem for MSAT-X

This paper describes the real-time digital implementation of an 8-differentiated phase-shift keying (DPSK) trellis-coded modulation (TCM) modem for operation on an L-band, 5 kHz wide, land mobile satellite (LMS) channel. The modem architecture as well as some of the signal processing techniques employed in the modem to combat the LMS channel impairments are described, and the modem performance over the fading channel is presented

Efficient implementation of pilot-aided 32 QAM for fixed wireless and mobile ISDN applications

This paper presents the design and performance of a pilot tone-aided 32 QAM modem developed for wireless ISDN applications. The modem is capable of transmitting a gross data rate of 70 kbit/s in a 20 kHz channel spacing. A low complexity receiver has been designed that allows the effects of fading and frequency offset to be removed digitally at a low IF using information extracted from the pilot tone. The design has been fully evaluated in narrowband Rayleigh and Rician fading channels. Computer simulations show that extreme Doppler shifts and frequency offsets have little effect on system performance. The design is suitable for mobile radio as well as fixed applications such as wireless in the local loop (WLL)

The Life of Aleksandr Men\u27: Hagiography in the Making

Hagiography is not an extinct genre in Russian literature, even though many believe that it was important in the history of early Russian literature but became irrelevant as Russian literature entered its modem period. The autobiography of priest A vvakum, written in the second half of the seventeenth century, is often considered to be the final work in the development of Russian hagiography. Russian spirituality has not died out, however, and holy men and women continue to display the same devotion to Christ that was admired in medieval saints. The biographies and memoirs of these modem saints retain some of the hallmarks of traditional hagiography. In this paper I propose to show that the memoirs written about one of these contemporary Christian heroes, Aleksandr Men\u27, draw upon traditional hagiographic elements in order to portray him as a saint. Furthermore, the literature written about Men\u27 contains the seeds for a full-length saint\u27s Life, one that could possibly be included among the works of a modem neo-hagiographic genre

Broadband: Europe needs more than DSL

Efficient broadband technologies such as DSL, fibre, cable modem, powerline communications, UMTS, WLAN or WiMax are powerful locational factors for an economy. Europe in particular should promote broadband communication further to tap into its growth potential. But given the prevailing ownership structures in fixed wire business, the promotion of broadband must not concentrate exclusively on DSL. Rather, its impact should be technology-neutral.communications, technology, broadband, DSL, cable modem, FTTH, regulation authority, liberalisation, deregulation, convergence

Programmable rate modem utilizing digital signal processing techniques

The engineering development study to follow was written to address the need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulation. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. Here design tradeoffs in each portion of the modulator and demodulator subsystem are outlined, and viable circuit approaches which are easily repeatable, have low implementation losses and have low production costs are identified. The research involved for this study was divided into nine technical papers, each addressing a significant region of concern in a variable rate modem design. Trivial portions and basic support logic designs surrounding the nine major modem blocks were omitted. In brief, the nine topic areas were: (1) Transmit Data Filtering; (2) Transmit Clock Generation; (3) Carrier Synthesizer; (4) Receive AGC; (5) Receive Data Filtering; (6) RF Oscillator Phase Noise; (7) Receive Carrier Selectivity; (8) Carrier Recovery; and (9) Timing Recovery

A B-ISDN-compatible modem/codec

Coded modulation techniques for development of a broadband integrated services digital network (B-ISDN)-compatible modem/codec are investigated. The selected baseband processor system must support transmission of 155.52 Mbit/s of data over an INTELSAT 72-MHz transponder. Performance objectives and fundamental system parameters, including channel symbol rate, code rate, and the modulation scheme are determined. From several candidate codes, a concatenated coding system consisting of a coded octal phase shift keying modulation as the inner code and a high rate Reed-Solomon as the outer code is selected and its bit error rate performance is analyzed by computer simulation. The hardware implementation of the decoder for the selected code is also described