On the Power Spectral Density of the GSM Signaling Scheme

In this paper, the Power Spectral Density of encoded Gaussian Minimum Shift Keying (GMSK) which is the Signaling Scheme of the Global System for Mobile Communication (GSM) is derived by a combined approach of the autocorrelation method and Markov Process. In the analysis, the Amplitude Modulated Pulse decomposition proposed by P. Laurent is employed to ease computation. Encoding of the message data utilizes Convolutional Code of rate1/2. Results are for both the uncoded and coded waveform comparing variation in power spread over a range of frequency

A mixed-signal integrated circuit for FM-DCSK modulation

This paper presents a mixed-signal application-specific integrated circuit (ASIC) for a frequency-modulated differential chaos shift keying (FM-DCSK) communication system. The chip is conceived to serve as an experimental platform for the evaluation of the FM-DCSK modulation scheme, and includes several programming features toward this goal. The operation of the ASIC is herein illustrated for a data rate of 500 kb/s and a transmission bandwidth in the range of 17 MHz. Using signals acquired from the test platform, bit error rate (BER) estimations of the overall FM-DCSK communication link have been obtained assuming wireless transmission at the 2.4-GHz ISM band. Under all tested propagation conditions, including multipath effects, the system obtains a BER = 10-3 for Eb/No lower than 28 dB.Ministerio de Ciencia y Tecnología TIC2003-0235

Secure Coherent-state Quantum Key Distribution Protocols with Efficient Reconciliation

We study the equivalence between a realistic quantum key distribution protocol using coherent states and homodyne detection and a formal entanglement purification protocol. Maximally-entangled qubit pairs that one can extract in the formal protocol correspond to secret key bits in the realistic protocol. More specifically, we define a qubit encoding scheme that allows the formal protocol to produce more than one entangled qubit pair per coherent state, or equivalently for the realistic protocol, more than one secret key bit. The entanglement parameters are estimated using quantum tomography. We analyze the properties of the encoding scheme and investigate its application to the important case of the attenuation channel.Comment: REVTeX, 11 pages, 2 figure

Squeezing-enhanced quantum key distribution over atmospheric channels

We propose the Gaussian continuous-variable quantum key distribution using squeezed states in the composite channels including atmospheric propagation with transmittance fluctuations. We show that adjustments of signal modulation and use of optimal feasible squeezing can be sufficient to significantly overcome the coherent-state protocol and drastically improve the performance of quantum key distribution in atmospheric channels, also in the presence of additional attenuating and noisy channels. Furthermore, we consider examples of atmospheric links of different lengths, and show that optimization of both squeezing and modulation is crucial for reduction of protocol downtime and increase of secure atmospheric channel distance. Our results demonstrate unexpected advantage of fragile squeezed states of light in the free-space quantum key distribution applicable in daylight and stable against atmospheric turbulence.Comment: 10 pages, 3 figure

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

A selectable-bandwidth 3.5 mW, 0.03 mm(2) self-oscillating Sigma Delta modulator with 71 dB dynamic range at 5 MHz and 65 dB at 10 MHz bandwidth

In this paper we present a dual-mode third order continuous time Sigma Delta modulator that combines noise shaping and pulse-width-modulation (PWM). In our 0.18 micro-m CMOS prototype chip the clock frequency equals 1 GHz, but the PWM carrier is only around 125 MHz. By adjusting the loop filter, the ADC bandwidth can be set to 5 or 10 MHz. In the 5 MHz mode the peak SNDR equals 64 dB and the dynamic range 71 dB. In the 10 MHz mode the peak SNDR equals 58 dB and the DR 65 dB. This performance is achieved at an attractively low silicon area of 0.03 mm^2 and a power consumption of 3.5 mW

Shuttle S-band communications technical concepts

Using the S-band communications system, shuttle orbiter can communicate directly with the Earth via the Ground Spaceflight Tracking and Data Network (GSTDN) or via the Tracking and Data Relay Satellite System (TDRSS). The S-band frequencies provide the primary links for direct Earth and TDRSS communications during all launch and entry/landing phases of shuttle missions. On orbit, S-band links are used when TDRSS Ku-band is not available, when conditions require orbiter attitudes unfavorable to Ku-band communications, or when the payload bay doors are closed. the S-band communications functional requirements, the orbiter hardware configuration, and the NASA S-band communications network are described. The requirements and implementation concepts which resulted in techniques for shuttle S-band hardware development discussed include: (1) digital voice delta modulation; (2) convolutional coding/Viterbi decoding; (3) critical modulation index for phase modulation using a Costas loop (phase-shift keying) receiver; (4) optimum digital data modulation parameters for continuous-wave frequency modulation; (5) intermodulation effects of subcarrier ranging and time-division multiplexing data channels; (6) radiofrequency coverage; and (7) despreading techniques under poor signal-to-noise conditions. Channel performance is reviewed