Comparison of convolutional codes against turbo codes for a frequency hopped SDPSK receiver in partial-band jamming
DOI: 10.1109/MILCOM.1999.822743 Conference: Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE, Volume: 1
This paper analyzes the performance of a slow frequency hopping
waveform, using a new kind of turbo-code named `frame-oriented
turbo-code' with a SDPSK modulation, which could provide medium data
rates for a military satcom system. This turbo-code is derived from the
classical turbo-code but operates with blocks; the decoder uses a SOVA
decoding algorithm. Some results are also provided with a MAP decoder.
This concept could be applied to a transparent payload or to an onboard
processing system. The paper focuses on the gain of performance with
partial-band noise jamming (PBNJ) compared to a classical convolutional
encoder (7,1/2) for the same coding rate. Simulation results show a
significant gain under PBNJ with different block lengths
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- "Two such schemes are symmetric differential PSK (SDPSK), and Gaussian minimum shift keying (GMSK). These modulation schemes have been frequently referred to in tactical satellite applications  ; however, performance analyses of these waveforms have been mostly limited to the SDPSK, either under the tone jamming  or PBNJ  with complicated turbo coding. Little is also known on the application of 1-bit differential GMSK and its BER performance under PBNJ and BMTJ in the literature. "
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ABSTRACT: In this paper, SDPSK and 1-bit differential-detected GMSK are proposed for use in a tactical FH-FDMA on-board processing (OBP) satellite communication system. The proposed waveforms are modeled and their respective error performances are simulated under the effects of jamming. Both waveforms, known to be relatively robust for ACI and ISI, are convolutionally encoded and Fast Frequency Hopped (FFH) to mitigate the effects of jamming which is modeled as Partial Band Noise Jamming (PBNJ) or Band Multi-Tone jamming (BMTJ) with AWGN. Simulations are conducted at the modem level as a preliminary step towards assessing their performances in a multichannel FDMA OBP satellite system. Results are presented for the various modem configurations, several of which illustrate the effect of the different BT products on the FFH/GMSK waveform. A comparative assessment of FFH/GMSK and FFH/SDPSK under identical jamming is also presented. Based on the empirical results obtained herein, the feasibility of using FFH/GMSK in a mobile tactical FDMA OBP satellite communication system is strongly dependent on the specific BT product used and the severity of ISI. Furthermore, when considering BMTJ with AWGN impairment the modem performance is highly dependent upon the amount of thermal noise present in the jammed channel. On the contrary, FFH/SDPSK is fairly robust and insensitive to broadband noise and ISI, and is thus tentatively preferred for deployment in a mobile tactical FFH/FDMA OBP satellite communication system.
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ABSTRACT: A side information generating algorithm for iterative decoding in frequency-hopping spread-spectrum (FH-SS) is proposed. In the algorithm, the channel state probabilities are iteratively calculated with an extension of the Kang-Stark algorithm. Differential encoded phase shift keying (DPSK) is employed with the noncoherent expanded trellis based iterative receiver. The performance of the proposed algorithm with the convolutionally coded system is evaluated by simulation and compared with a system using a ratio threshold test (RTT) for PSK. The results show that the performance of the introduced algorithm is similar to the system with perfect jamming state information and provides better side information than RTT.
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