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BPSK
milstar: Missions not requiring a residual carrier and having modest data rates (20 ks/s - 200 ks/s) should consider BPSK/NRZ modulation first. ######################## nonreturn-to-zero (NRZ) to binary phase-shift keying It provides a good compromise between spectrum efficiency and simplicity of design. While data imbalance does not result in system losses as in the case of PCM/PM/NRZ modulation, the statistics of each application should be reviewed. Agencies employing a DTTL architecture in their symbol synchronizers, must ensure a sufficient transition density to acquire and maintain synchronization. Manchester encoding prior to BPSK modulation can ensure sufficient transitions. As with PCM/PM/Bi-N modulation, there is a 100% penalty in spectrum efficiency over the NRZ equivalent https://deepspace.jpl.nasa.gov/files/phase3.pdf https://deepspace.jpl.nasa.gov/dsndocs/810-005/208/208B.pdf
milstar: Typically, there were three situations in which the tradition ruled a mandatory usage of noncoherent or differentially coherent techniques ######################################################################################## in order to obtain high performance communications: 1) in the presence of jamming, ########################## 2) with short packets, ##################### and 3) in land mobile wireless communications. ############################# https://ieeexplore.ieee.org/document/6618624
milstar: From the communication channel and implementation aspects of communications, the transmission environment may be sufficiently degraded that introduces practical difficulties in acquiring and tracking a coherent demodulation reference signal. Coherent receivers require exact knowledge of the channel phase for optimum performance. Due to the difficult task of estimating the channel phase, non-coherent as well as differential detection is an attractive alternative to coherent detection. ################################################################################################# A conventional differential detector uses the signal received in the previous symbol interval as a phase reference for the received signal in the current interval. As long as the phase distortion introduced by channel varies slowly relative to the symbol rate, conventional differential detection will work quite well. ############################################################################################# This assumption is not always true, ########################### and, in addition, differentially coherent detection is based on the premise that there is no intersymbol interference (ISI) in the received signal. ################################################################## https://ieeexplore.ieee.org/document/6618624/figures#figures
milstar: https://www.nhk.or.jp/strl/publica/bt/bt14/pdf/le0014.pdf
milstar: Incoherent detection is frequently used in terrestrial mobile transmissions since large fluctuations in amplitude due to fading effects make it difficult to recover the carrier. #################################### Here, however, because the signal itself, which includes noise and distortion, is used as the reference phase in incoherent detection, the bit error characteristics are worse than those of coherent detection. https://www.nhk.or.jp/strl/publica/bt/bt14/pdf/le0014.pdf
milstar: https://pdfs.semanticscholar.org/f5f9/23a42826ef493e88ff6cd13d21ce28644bdc.pdf 18.3 Mobile-Radio Propagation: Large-Scale Fading and SmallScale Fading
milstar: https://www.gaussianwaves.com/2011/05/ebn0-vs-ber-for-bpsk-over-rayleigh-channel-and-awgn-channel-2/ https://www.gaussianwaves.com/2010/04/performance-comparison-of-digital-modulation-techniques-2/
milstar: https://cyberleninka.ru/article/v/modelnoe-issledovanie-pomehoustoychivosti-priema-radiosignalov-s-qpsk-bpsk-8psk-i-dbpsk
milstar: «Самое главное – это создание системы управления и системы неубиваемой связи», – цитирует вице-премьера Дмитрия Рогозина ТАСС.
milstar: https://megapredmet.ru/1-20464.html Методы манипуляции Цифровой радиосвязи Учебное пособие для студентов радиотехнических специальностей Разработчик: заведующий кафедрой СРС, профессор Мелихов С.В. Томск ‑ 2014 Содержание Содержание 1. Дифференциальная (относительная) бинарная (двоичная) фазовая манипуляция – Differential Binary Phase Shift Keying (DBPSK)............................................................................................. 3 1.1.Передатчик DBPSK‑радиосигнала................................................................................ 3 1.2. Когерентная демодуляция DBPSK–радиосигнала..................................................... 7 1.3. Блок восстановления несущей частоты (БВНЧ). Фазовая неоднозначность при формировании опорного колебания............................................................................................................... 9 1.4. Блок восстановления тактовой частоты (БВТЧ)....................................................... 10 1.5. Схема Костаса для квазикогерентной демодуляции DBPSK-радиосигнала........ 12 1.6. Некогерентная демодуляция DBPSK–радиосигнала............................................... 13 При невозможности формирования когерентного опорного колебания, например из‑за значительных фазовых возмущений, вносимых средой распространения радиоволн или аппаратурой приемо-передающего тракта, применяется некогерентная демодуляция. Как уже отмечалось, применение некогерентной демодуляции возможно только при дифференциальном кодировании информационной последовательности в передатчике.
milstar: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3383&context=smallsat
milstar: https://pdfs.semanticscholar.org/5873/693c56d04cd0a0a44ae6c5f3a15f214790ed.pdf Convolution coding, BPSK, QPSK, QAM-16, DS-CDMA, maximal ratio combining
milstar: Non-coherent modulations can be used by a communication system that does not maintain a phase lock between transmitter and receiver, or have knowledge of the amplitude change of the transmitted symbol caused by the channel. This means that the received symbols are rotated and scaled arbitrarily compared to the transmitted symbol. Therefore the ASK, PSK, or QAM modulations cannot be used because they require the received symbol phase and amplitude to be very close to that transmitted phase and amplitude. The solution is to use differential PSK (DPSK) or differential APSK (DAPSK) modulation. Differential modulations encode the transmitted information to a phase, or phase and amplitude change from one transmitted symbol to the next. This encoding introduces memory to the signal, because transmitted symbols depend on previous symbols. As a consequence, the demodulator has to consider two consecutive symbols when making decisions. The next two sections describe these two modulation methods. http://vig.pearsoned.com/samplechapter/0672321572.pdf The performance loss of DPSK compared to coherent modulation varies with the size of the modulation [11], for DBPSK it is between 1-2dB ############################# the system that does not use channel coding has to spend 5.5dB more energy for each FIGURE 3.11 transmitted bit than the system that uses channel coding
milstar: http://vig.pearsoned.com/samplechapter/0672321572.pdf The performance of channel codes is ultimately limited by the channel capacity formula, Equation 3.1. After about 50 years of research, Turbo-codes [7] have finally emerged as a class of codes that can approach the ultimate limit in performance. Another innovation, and a very active research area, are Low Density Parity Check (LDPC) codes, which also have performance very close to the capacity.
milstar: it uses Recursive codes and iterative soft decoders. Recursive codes for making short constraint length in convolution codes and iterative soft decoder is for improving estimated received message by reapplying the decoded words to the outer and repeats it many times until all reduce below the threshold point. It’s performance depends upon S/N ratio written below: If S/N ratio is low the iterative decoding is worse. If S/N ratio is in between low-medium then iterative decoding is very effective. If S/N ratio is high then iterative decoding converses in few iterations. Overall its performance increases as S/N ratio increases. In Turbo Codes bit error rate (BER) is achieved even for low S/N ratio as errors flow moderate. In Turbo codes high value of Eb / No is achieved. Actually Turbo Codes are Shannon limit error correction 2.2 DBPSK Differential Binary Phase Shift Keying is a signaling technique that conveys data by changing the phase of the carrier wave. It eliminates the need for phase synchronization of the coherent receiver with PSK. In this present value is depending upon past value so it determines the difference between ‘0’ and ‘1’. In DBPSK, input must be a discrete time binary valued signal https://www.researchgate.net/publication/281373596_TURBO_CODES_DBPSK_versus_QPSK
milstar: Turbo codes were recently proposed by Berrou, Glavieux, and Thitimajshima [2] as a remarkable step forward in high-gain, low-complexity coding. It has been claimed these codes achieve near-Shannon-limit error correction performance with relatively simple component codes and large interleavers. A required Eb/N0 of 0.7 dB was reported for a bit error rate (BER) of 10−5, using a rate 1/2 turbo code https://klevas.mif.vu.lt/~skersys/vsd/turbo/120D.pdf
milstar: Deep space exploration requires the use of powerful error correction codes, such as turbo codes [3], lower rate low-density-parity-check (LDPC) codes [4] and concatenated Reed-Solomon (RS) and convolutional codes. Since turbo codes have better performance than LDPC at low SNR [19], they have been chosen as IC. On the contrary, receiving the updated information from the inner decoder, the OC decoder, that is an LDPC code, can fully exploit its deep waterfall region and low error floor spacomm_2013_1_10_30012.pdf Concatenated Turbo/LDPC Codes for Deep Space Communications: Performance and Implementation Carlo Condo Department of Electronics and Telecommunications Politecnico di Torino Torino, Italy carlo.condo@polito.it
milstar: The DSN provides support for the turbo code specified in CCSDS Recommendation 131.0-B-1 for information block lengths (k) of 1784, 3568, 7136, 8920 bits and nominal code rates (r) of 1/2, 1/3, 1/4, and 1/6. The recommendation also permits an information block length of 16,384 bits however the encoder for this block length has not been completely specified and it is not supported by the DSN, The four supported block lengths are the same as would be required for Reed-Solomon encoding using an interleave factor (I) of 1, 2, 4, or 5. https://deepspace.jpl.nasa.gov/dsndocs/810-005/208/208B.pdf
milstar: Low-Density Parity-check (LDPC) Codes Low-Density Parity-Check (LDPC) codes have been developed that provide neartheoretical limit performance at high code rates to complement the similar performance provided by Turbo codes at low code rates. They promise to be especially useful in applications where the bandwidth required to use a Turbo code is not available or would complicate spacecraft equipment design https://deepspace.jpl.nasa.gov/dsndocs/810-005/208/208B.pdf
milstar: http://www.comtechefdata.com/files/appnotes-pdf/The%20Case%20for%20Turbo%20Product%20Coding%20in%20Satellite%20Communications.pdf
milstar: BPSK Rate 21/44 and Rate 5/16 (Flux density reduction modes) Two further code rates - Rate 21/44 BPSK (very close to Rate 1/2) and Rate 5/16 BPSK (very close to Rate 1/3) were then added for a military customer ================================================== and delivered in June 2000. These two rates were developed to address an entirely different case, namely that of transmission from very small antennas, with limited transmitter power. For a dish antenna, the gain is directly proportional to its area, and the lower the gain, the less directional the antenna becomes. Thus, in satellite transmission, even though the dish may be perfectly pointed at the desired satellite, if the beamwidth is wide enough, adjacent satellites will also be illuminated. This is a potential source of interference, and for this reason the ITU (International Telecommunications Union) place strict limits on the power spectral density (also referred to as flux density) of signals arriving at adjacent satellites. One obvious method to reduce the level is to spread the transmitted signal over as wide a bandwidth as possible. In the past, this has sometimes been achieved using Spread Spectrum modulation, but at the expense of demodulator complexity. However, by using BPSK modulation, and low FEC code rates (down to Rate 1/3, for example) the power spectral density may be reduced. Taking Rate 1/2 QPSK as a baseline, moving to Rate 5/16 BPSK Turbo Product Coding gives a reduction in power spectral density of 5 dB. Furthermore, the increased coding gain of this FEC method allows a further reduction in transmitter power. Using Rate 1/2 Viterbi with concatenated Reed-Solomon as a baseline example, Rate 5/16 provides 1.5 - 2.0 dB improvement in coding gain. Putting these two factors together yields an overall reduction in power spectral density of approximately 7 dB. This simultaneously permits a smaller antenna, and reduced transmitter power. The disadvantage is the increased spectral occupancy of the carrier, and it will depend on the particular satellite operator to determine if this poses a severe economic problem. http://www.comtechefdata.com/files/appnotes-pdf/The%20Case%20for%20Turbo%20Product%20Coding%20in%20Satellite%20Communications.pdf
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