Pilot Symbol Assisted Modulation (PSAM) is a good method to compensate for the channel fading effect in wireless mobile communications. In PSAM, known pilot symbols are periodically inserted into the transmitted data symbol stream and the receiver uses these symbols to derive amplitude and phase reference. <p> One aspect of this procedure, which has not received much attention yet, is the frame synchronization, i.e. the method used by the receiver to locate the time position of the pilot symbols. In this study, two novel non-coherent frame synchronization methods are introduced in which only the magnitude of received signal is used to obtain the timing of the pilot symbol. The methods are evaluated for both AWGN and frequency non-selective slow Rayleigh fading channels. <p> One synchronization technique is derived by standard maximum likelihood (ML) estimation formulation, and the other is obtained by using maximum a Posteriori probability (MAP) with a threshold test. Signal processing in the receiver uses simplifying approximations that rely on relatively high signal-to-noise ratio (SNR) as consistent with the reception of 16-QAM. Computer simulation has been used to test the acquisition time performance and the probability of false acquisition. Several lengths and patterns of pilot symbol sequences were tested where every 10th symbol was a pilot symbol and all other symbols were randomly selected data symbols. When compared with the other published synchronizers, results from this study show better performance in both AWGN and fading channels. Significantly better performance is observed in the presence of receiver frequency offsets.

Pilot Symbol Assisted Modulation (PSAM) is a good method to compensate for the channel fading effect in wireless mobile communications. In PSAM, known pilot symbols are periodically inserted into the transmitted data symbol stream and the receiver uses these symbols to derive amplitude and phase reference. <p> One aspect of this procedure, which has not received much attention yet, is the frame synchronization, i.e. the method used by the receiver to locate the time position of the pilot symbols. In this study, two novel non-coherent frame synchronization methods are introduced in which only the magnitude of received signal is used to obtain the timing of the pilot symbol. The methods are evaluated for both AWGN and frequency non-selective slow Rayleigh fading channels. <p> One synchronization technique is derived by standard maximum likelihood (ML) estimation formulation, and the other is obtained by using maximum a Posteriori probability (MAP) with a threshold test. Signal processing in the receiver uses simplifying approximations that rely on relatively high signal-to-noise ratio (SNR) as consistent with the reception of 16-QAM. Computer simulation has been used to test the acquisition time performance and the probability of false acquisition. Several lengths and patterns of pilot symbol sequences were tested where every 10th symbol was a pilot symbol and all other symbols were randomly selected data symbols. When compared with the other published synchronizers, results from this study show better performance in both AWGN and fading channels. Significantly better performance is observed in the presence of receiver frequency offsets.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes algorithms implemented by the Magellan High Rate Processor to recover radar data corrupted by the failure of an onboard tape recorder that dropped bits. For data with error correction coding, an algorithm was developed that decodes data in the presence of bit errors and missing bits. For the SAR data, the algorithm takes advantage of properties in SAR data to locate corrupted bits and reduce there effects on downstream processing. The algorithms rely on communication approaches, including an efficient tree search and the Viterbi algorithm to maintain the required throughput rate.

This research investigates the application of multiuser interference suppression to direct-sequence code-division multiple-access (DS-CDMA) for peer-to-peer packet radio networks. The emphasis of this work is to develop and validate efficient interference suppression techniques through selective cancellation of interference; next, the combination of interference suppression with error correction coding is studied. A decoder-assisted frame synchronization technique is proposed for future packet radio system. The performance of DS-CDMA in packet radio networks suffers from the near-far problem. This near-far problem can be alleviated by using either a multiuser receiver or a single-user adaptive receiver along with centralized or distributed power control. The first part of this dissertation compares the use of these receivers in a peer-to-peer environment. Next, we investigate how interference cancellation can be combined with forward error correction coding for throughput enhancement of the system. Although receivers using interference suppression are simple in structure, the performance degrades due to the lack of exact knowledge of the interfering signal in cancellation and also due to biased decision statistics for the parallel cancellation case. We consider a system that employs both partial parallel interference cancellation and convolutional coding. Information is shared between the operations of interference cancellation and decoding in an iterative manner, using log-likelihood ratios of the estimated coded symbols. We investigate the performance of this system for both synchronous and asynchronous CDMA systems, and for both equal and unequal signal powers. Finally, a new code-assisted frame synchronization scheme, which uses the soft-information of the decoder, is proposed and evaluated. The sync bits are placed in the mid-amble, and encoded as a part of the data sequence using the error correction encoder to resolve time ambiguities. This technique is applied for turbo decoder-assisted frame synchronization. The performance improvement of these proposed techniques over conventional synchronization techniques is explored via simulation. / Ph. D.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The UTTR (Utah Test & Training Range) offers the largest over land test and training airspace in the continental United States. It provides excellent telemetry data processing capability through a number of TM (telemetry) sites. Selecting the best source of telemetry data for optimum coverage from these many sites can be very involved and challenging for ground station personnel. Computer-based best source selection automates this process, thereby increasing accuracy and efficiency. This paper discusses the capabilities of the BTSS (Best Telemetry Source Selector), its background, design and development, applications, and future at the UTTR.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / To support initiatives for cheaper, faster, better ground telemetry systems, the Data Systems Technology Division (DSTD) at NASA Goddard Space Flight Center is developing a new Very Large Scale Integration (VLSI) Application Specific Integrated Circuit (ASIC) targeted to dramatically lower the cost of telemetry frame synchronization. This single VLSI device, known as the Parallel Integrated Frame Synchronizer (PIFS) chip, integrates most of the functionality contained in high density 9U VME card frame synchronizer subsystems currently in use. In 1987, a first generation 20 Mbps VMEBus frame synchronizer based on 2.0 micron CMOS VLSI technology was developed by Data Systems Technology Division. In 1990, this subsystem architecture was recast using 0.8 micron ECL & GaAs VLSI to achieve 300 Mbps performance. The PIFS chip, based on 0.7 micron CMOS technology, will provide a superset of the current VMEBus subsystem functions at rates up to 500 Mbps at approximately one-tenth current replication costs. Functions performed by this third generation device include true and inverted 64 bit marker correlation with programmable error tolerances, programmable frame length and marker patterns, programmable search-check-lock-flywheel acquisition strategy, slip detection, and CRC error detection. Acquired frames can optionally be annotated with quality trailer and time stamp. A comprehensive set of cumulative accounting registers are provided on-chip for data quality monitoring. Prototypes of the PIFS chip are expected in October 1995. This paper will describe the architecture and implementation of this new low-cost high functionality device.

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Frame synchronization is an important problem in digital communication systems. In frame synchronization, the main task is to find the frame start given the flow of the communication symbols. In this thesis, frame synchronization problem is investigated for both additive white Gaussian noise (AWGN) channels and frequency selective channels. Most of the previous works on frame synchronization consider the simple case of AWGN channels. The algorithms developed for this purpose fail in frequency selective channels. There is limited number of algorithms proposed for the frequency selective channels. In this thesis, existing frame synchronization techniques are investigated for both AWGN and frequency selective channels. Code-aided frame synchronization techniques are combined with the methods for frequency selective channels. Mainly two types of code-aided frame synchronization schemes are considered and two new system structures are proposed for frame synchronization. One of the proposed structures performs better than the alternative methods for frequency selective channels. The overall system for this new synchronizer is composed of a list synchronizer which generates the possible frame starts, a channel estimator, a soft output MLSE equalizer, and a soft output Viterbi decoder. A mode separation algorithm is used to generate the statistics for the selection of the true frame start. Several experiments are done and the performance is outlined for a variety of scenarios.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Jet Propulsion Laboratory’s (JPL) Advanced Multi-Mission Operations System (AMMOS) system processes data received from deep-space spacecraft, where error rates are high, bit rates are low, and every bit is precious. Frame synchronization and data extraction as performed by AMMOS enhance data acquisition and reliability for maximum data return and validity. Unique aspects of data phase determination, sync acquisition and sync loss and other bit-level topics are covered.

In this thesis, frame synchronization for iNET formatted SOQPSK-TG communications is considered. Frame synchronization for M-ary linear modulations (MQAM, MPSK, etc.) are known in the literature using pilot detection methods, but are based on a signal model that does not apply to SOQPSK-TG. Maximum likelihood frame synchronizers are derived for an SOQPSK-TG system following assumptions found in the literature. The analysis shows that a reinterpretation of known detectors operating on the samples of the received waveform and locally stored samples of the pilot is the optimum approach for this case. Simulation results for an AWGN channel and several multipath channels verify the performance of the synchronizers.