A small terminal for satellite communication systems

A small portable, low-cost satellite communications terminal system incorporating a modulator/demodulator and convolutional-Viterbi coder/decoder is described. Advances in signal processing and error-correction techniques in combination with higher power and higher frequencies aboard satellites allow for more efficient use of the space segment. This makes it possible to design small economical earth stations. The Advanced Communications Technology Satellite (ACTS) was chosen to test the system. ACTS, operating at the Ka band incorporates higher power, higher frequency, frequency and spatial reuse using spot beams and polarization

A study of the minimum shift keying modulation scheme

This thesis concerns itself with the study of the Minimum Shift Keying (MSK) modulation scheme. The aspects considered are its operation under non-linear conditions as well as an investigation into the hardware implementation of both coherent and non-coherent MSK modems. The literature on digital data transmission and MSK in particular is surveyed, and a comprehensive theoretical description of MSK is given. In addition, papers on the operation of MSK under non-linear conditions were studied, and their major findings are presented. Due to the lack of theory on the effects of incorrect modulation index on the error performance of MSK, an investigation into this avenue was performed. The design of a correction mechanism for maintaining the modulation index at its correct value is described, and aspects of its implementation are considered. Using the available literature, various modules of which a coherent MSK modem is comprised were developed, and their design is discussed. The design of a non-coherent MSK demodulator is also described

Low-complexity Noncoherent Iterative CPM Demodulator for FH Communication

In this paper, we investigate the noncoherent iterative demodulation of coded continuous phase modulation (CPM) in frequency hopped (FH) systems. In this field, one important problem is that the complexity of the optimal demodulator is prohibitive unless the number of symbols per hop duration is very small. To solve this problem, we propose a novel demodulator, which reduces the complexity by applying phase quantization and exploiting the phase rotational invariance property of CPM signals. As shown by computational complexity analysis and numerical results, the proposed demodulator approaches the performance of the optimal demodulator, and provides considerable performance improvement over the existing solutions with the same computational complexity

New System Design for Serial-MSK Based On Laurent Decomposition

Abstract-In this paper, a new approach to coding, modulation, and detection design for serial minimum-shift keying (MSK) modulation scheme is presented. The design of the new linear modulator is based on the Laurent decomposition of a well-known modified MSK scheme termed duobinary MSK. It is shown that a simple linear receiver can be designed to optimally detect the coded symbols. The detection problem for the recovery of the symbols sequence from the decision variable sequence is one corresponding to memoryless linear modulation. It is also demonstrated that the Euclidean distance between different signals is directly related to the Hamming distance between corresponding coded sequence. Therefore, optimum encoders (for a given rate and constraint length) that maximize the minimum Hamming distance can be applied

Receiver Performance for an Enhanced DGPS Data Channel

The Coast Guard currently operates a maritime differential GPS service consisting of two control centers and over 85 remote broadcast sites. This service broadcasts GPS correction information on marine radiobeacon frequencies to improve the accuracy and integrity of GPS. The existing system provides differential corrections over a medium frequency carrier using minimum shift keying (MSK) as the modulation method. MSK is a version of the Continuous Phase Frequency Shift Keying (CPFSK) modulation technique that is spectrally compact, meaning that it is a narrow band modulation scheme. In a binary signaling channel, the two instantaneous frequencies for this modulation method are chosen in such a way so as to produce orthogonal signaling with a minimum modulation index. Current DGPS corrections are transmitted at a relatively low data rate, with message structures designed in an era when Selective Availability was in full operation. Greater demands for accuracy coupled with current operations in a post SA environment have prompted a reexamination of the DGPS data and signal structure, with an eye towards improving information rate while minimizing legacy user impact. A two-phased plan for a new generation of DGPS capability can be envisioned. In the first phase (near-term) new ionospheric messages would be introduced to allow greater DGPS accuracy at larger distances from the beacons. This capability could support both double (LI/L2) and triple (L1/L2/L5) frequency operation. This phase requires only the definition of the new message type(s) and the commitment of receiver manufacturers to implement the usage of the new data. In the second phase (intermediate future) a new signal would come on line to support RTK using two and three frequencies and homeland security messaging. This signal would have the capacity to send 500 bps or so without disrupting the legacy signal or legacy receiver performance. This new signal could be one of the new modulation techniques that we have been investigating; phase trellis overlay and orthogonal frequency division multiplexing. Preliminary examinations of both of these techniques have shown the potential for increased bandwidth usage (ION NTM Jan. 2004), the effects on legacy receiver performance through a modulator test-bed (ION AM June 2004), and some effects of an actual transmitter (including antenna and coupler) on the signal (ION GNSS Sept 2004). The current paper describes recent investigations into the architecture of the receivers for these modulation methods including details of the demodulation and decoding methods. We also establish receiver performance measures and present preliminary performance results. Reprinted with permission from The Institute of Navigation (http://ion.org/) and The Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, (pp. 788-800). Fairfax, VA: The Institute of Navigation

Integrated Sensing and Communication Signals Toward 5G-A and 6G: A Survey

Integrated sensing and communication (ISAC) has the advantages of efficient spectrum utilization and low hardware cost. It is promising to be implemented in the fifth-generation-advanced (5G-A) and sixth-generation (6G) mobile communication systems, having the potential to be applied in intelligent applications requiring both communication and high-accurate sensing capabilities. As the fundamental technology of ISAC, ISAC signal directly impacts the performance of sensing and communication. This article systematically reviews the literature on ISAC signals from the perspective of mobile communication systems, including ISAC signal design, ISAC signal processing algorithms and ISAC signal optimization. We first review the ISAC signal design based on 5G, 5G-A and 6G mobile communication systems. Then, radar signal processing methods are reviewed for ISAC signals, mainly including the channel information matrix method, spectrum lines estimator method and super resolution method. In terms of signal optimization, we summarize peak-to-average power ratio (PAPR) optimization, interference management, and adaptive signal optimization for ISAC signals. This article may provide the guidelines for the research of ISAC signals in 5G-A and 6G mobile communication systems.Comment: 25 pages, 13 figures, 8 tables. IEEE Internet of Things Journal, 202

Joint symbol and chip synchronization for a burst-mode-communication superregenerative MSK receiver

In this paper we describe a superregenerative (SR) MSK receiver able to operate in a burst-mode framework where synchronization is required for each packet. The receiver is based on an SR oscillator which provides samples of the incoming instantaneous phase trajectories. We develop a simple yet effective technique to achieve joint chip and symbol synchronization within the time limits of a suitable preamble. We develop some general results and focus on the case of the IEEE 802.15.4 MSK physical layer. We provide details on a VHDL implementation on an FPGA where the most complex digital processing block is an accumulator. Simulation and experimental results are provided to validate the described technique.Peer ReviewedPostprint (published version