TDMA Burst Research Articles

Doppler Frequency Shift Tolerance Extension in Burst Spread Spectrum Communication System

A method to extend Doppler frequency discrimination tolerance is proposed for quick acquirement PN-code and Doppler frequency in TDMA burst spread spectrum communication system. According to Doppler’s different impacts on the correlation Peak and data demodulation, PN-code is acquired through single channel matched-filters, and parallel multi-channel correlators are used in the data demodulation branch channel. Thus, with using frame head prior information in data channel instead of traditional Cross-Product Automatic Frequency Control (CPAFC), the Doppler frequency shift discrimination tolerance is extended. Simulation and experiment show that frequency and PN-code can be acquired in several data periods, and synchronous time and the resources consumption are effectively reduced.

622 Mbps High-speed satellite communication system for WINDS

WINDS is the experimental communications satellite currently under joint development by Japanese Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT). The high-speed satellite communication system is very effective for quick deployment of high-speed networks economically. The WINDS will realize ultra high-speed networking and demonstrate operability of satellite communication systems in high-speed internet. NICT is now developing high-speed satellite communication system for WINDS. High-speed TDMA burst modem with high performance TPC error correction is underdevelopment. Up to the DAC on the transmitter and from the ADC on the receiver, all modem functions are performed in the digital processing technology. Burst modem has been designed for a user data rate up to 1244 Mbps. NICT is developing the digital terminal as a user interface and a network controller for this earth station. High compatibility with the Internet will be provided.

Design optimization of a TDMA burst modem for small earth stations in a channel containing two nonlinear devices

AbstractThe conventional TDMA satellite communication system generally involves operations in which a sufficient amount of back‐off is provided by using a large‐scale high‐power amplifier (HPA) in the earth station. However, if the HPA in the earth station can be operated at the saturation point, the earth station can be downsized and rendered into a low‐power consumption station, with considerable benefits in terms of earth station installation and economy of operation. The authors have proposed a system combining an optimized transmission system and error‐correction code, using burst modem filters and other devices, in a transmission system including two nonlinear devices of an earth station HPA and a satellite traveling‐wave tube amplifier (TWTA), and have confirmed by computer simulations and experiments that it is feasible to operate the earth station HPA at its saturation point. The authors have also demonstrated that adequate performance characteristics can be attained in terms of burst‐to‐burst interference and cycle‐skipping characteristics in the carrier recovery system. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(8): 47–62, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10149

Performance evaluation of a carrier recovery scheme for satellite TDMA symbol synchronous burst transmissions

This paper presents and evaluates the performance of an open-loop scheme for carrier-phase estimation with Doppler compensation which independently operates on each TDMA burst without requiring any training sequences. The approach is based on two known open-loop algorithms independently used for phase and frequency error estimation. The paper shows how to properly interface these two algorithms and how they can be extended also to include Doppler rate estimation. Copyright © 1999 John Wiley & Sons, Ltd.

An equalizer with carrier‐acquisition‐during‐training (CAT) algorithm for mobile radio

AbstractThis paper investigates an adaptive equalizer with carrier frequency offset compensation for digital mobile radio transmission over several tens kbit/s. The performance of conventional adaptive equalizers for mobile radio severely degrades for receiving signals having carrier frequency offset which is caused by local oscillator frequency offset due to misadjustment, temperature dependence, and aging.Carrier frequency offset compensation for TDMA burst signaling requires both accurate and short‐time measurements. However, both requirements have a tradeoff relationship and must be optimized.This paper proposes the carrier‐acquisition‐during‐training (CAT) algorithm for transmissions allowing a training signal. First, two basic configurations and their equivalence are discussed. Next, computer simulations and real‐time experiments with one‐chip DSP show the effectiveness of CAT by demonstrating training convergence, optimum parameter characteristics, and average BER performance under two‐path selective fading with one‐symbol delay difference and independent Rayleigh components.

Fiber-optic local area passive network using burst TDMA scheme

A fiber-optic loop-configured passive network using burst TDMA scheme which features high reliability and efficient communication capability is presented. The basic analysis for the passive network design including the level diagram, dynamic range, and TDMA burst synchronization are discussed. It is calculated that about 20 stations can be installed if the output peak power of laser diode is +20 dBm and the connector pair loss of optical access coupler is 1 dB. Efficient data transmission of nearly 80 percent with a frame length of 1 ms can be obtained in the TDMA system for 20 stations. The station equipment designs concerning to the burst-mode optical transmission and the unique word detection are also described. An experimental system model with three stations using 51.2-Mbit/s bit rate is constructed, and the feasibility of this passive loop-configured network has been confirmed.

Modulation Transfer from TDMA On-Off Bursting to FM Carriers in Memoryless Nonlinear Devices: Part I--Power Spectra

The modulation transfer noise caused by the bursts of TDMA signals is modeled and analyzed in detail. Expressions of the power spectra of the RF and the baseband modulation transfer noise have been obtained for the most general case of L TDMA and N FM carriers in a zero-memory nonlinear amplifier such as a helix-type TWTA. From these general expressions, the RF power spectrum and the baseband modulation transfer noise onto the FM carriers can be readily computed. It is shown that there are only line spectra and no continuous spectrum in the modulation transfer noise caused by the TDMA on-off bursting. The separation of the spectral lines is equal to the TDMA frame rate. The maximum of the power spectrum of the modulation transfer noise is inversely proportional to the square of the TDMA frame duration and is independent of the separation between TDMA and FM carriers. The modulation transfer noise is in general a complicated function of TDMA burst levels, burst patterns, burst lengths, FM carrier levels, carrier sizes, device nonlinearities, and operating points.

Modulation Transfer from TDMA On-Off Bursting to FM Carriers in Memoryless Nonlinear Devices, Part II-Baseband Performance

When TDMA and FM carriers are commonly amplified by a memoryless device with nonlinear amplitude and phase characteristics, modulation transfer noise induced by the on-off bursting of the TDMA signals will be present at the FM carriers. In Part II of this paper, closed form expressions of the power spectra of the modulation transfer noise are derived for many special carrier configurations of interest. Numerical examples are also provided in terms of the signal-to-modulation transfer noise ratio, SNR, in the baseband of the FM carriers. It is shown how SNR varies as a function of TDMA burst levels, burst patterns, burst lengths, FM carrier levels, carrier sizes, and device nonlinearities and operating points. With these detailed analyses and numerical examples, insight can be gained into the mechanism of modulation transfer from TDMA on-off bursting to the FM signals. Results presented in this part of the paper should be useful for transmission systems planning and evaluation, and for TDMA burst scheduling.

A Scanning Spot-Beam Satellite System

We propose a satellite with a high gain, movable spot beam to communicate with individual earth stations time-sharing a single channel in the tdma (Time-Division Multiple Access) mode. It is estimated that this approach could readily save some 20 dB in the link budget while still providing full U.S. coverage. When this 20 dB is apportioned with the objectives of reducing the earth-station antenna size, increasing the satellite capacity, and reducing transmitter power, the effects are dramatic. This technique can be combined with a fixed-spot beam system serving major traffic areas. This combination can provide both full area coverage as well as multiple reuse of the frequency band. A tdma burst organization is proposed, and estimates of burst lengths, beam switching intervals, and buffer storage size are made for a 100-earth-station network operating on a 600 Mb/s channel. A phased array antenna with each element irradiating the entire U.S. is employed to form the movable spot-beam. This provides an attractive solution even though a closed-loop beam-forming algorithm may be required. It appears feasible to construct such an antenna with nearly 50-dB gain capable of forming a spot beam toward any position within the continental United States with a switching time of a few nanoseconds.