Continuous phase modulation

About: Continuous phase modulation is a research topic. Over the lifetime, 3199 publications have been published within this topic receiving 37245 citations. The topic is also known as: CPM.

Capacity-Achieving CPM Schemes

Abstract: The pragmatic approach to coded continuous-phase modulation (CPM) is proposed as a capacity-achieving low-complexity alternative to the serially concatenated CPM (SC-CPM) coding scheme. In this paper, we first perform a selection of the best spectrally efficient CPM modulations to be embedded into SC-CPM schemes. Then, we consider the pragmatic capacity (a.k.a. BICM capacity) of CPM modulations and optimize it through a careful design of the mapping between input bits and CPM waveforms. The so obtained schemes are cascaded with an outer serially concatenated convolutional code to form a pragmatic coded-modulation system. The resulting schemes exhibit performance very close to the CPM capacity without requiring iterations between the outer decoder and the CPM demodulator. As a result, the receiver exhibits reduced complexity and increased flexibility due to the separation of the demodulation and decoding functions.

Multiuser Serially Concatenated Continuous Phase Modulation

Abstract: A multiuser communication system using serially concatenated and randomly interleaved continuous phase modulation (SCCPM) over the additive white Gaussian noise (AWGN) channel is investigated. The users, which may be asynchronous, are allowed to have individual energy levels as well as carrier frequencies and phases. This model incorporates multiple-access signaling similar to direct-sequence code division multiple-access (DS-CDMA), trellis-coded multiple-access (TCMA), and frequency division multiple-access (FDMA) with arbitrary spectral overlap, as well as non-intentional co-channel or adjacent channel interference of the same signaling type. First, the system is analyzed through analytical upper bounds on the average bit error probability for a given user under maximum-likelihood (ML) detection, where the R> average is over the ensemble of systems over all sets of interleavers. It is shown that in a properly designed system, the bit error probability vanishes for infinite interleaver sizes and a sufficiently large channel signal-to-noise ratio (SNR), regardless of the signal correlation between the users. Thus, even with equal modulation, energy levels, and carrier frequencies and phases, the users can be detected adequately provided they employ random interleaving. The second part of the analysis concerns iterative decoding of multiuser SCCPM. A convergence analysis based on EXIT charts is presented, along with decoding threshold estimates. It is observed that in systems with no frequency offset, the performance of ML detection does not always carry over to iterative decoding. On the other hand, for many other systems excellent performance can be obtained both in terms of power efficiency (bit error rate as a function of SNR) and spectral efficiency (bandwidth). In particular, systems are demonstrated with performance within 1 dB of the average-power limited Shannon capacity at 1 bit/s/Hz, and within 2.3 dB at 2 bits/s/Hz.

A 13 pJ/bit 900 MHz QPSK/16-QAM Band Shaped Transmitter Based on Injection Locking and Digital PA for Biomedical Applications

Abstract: This paper presents a 900 MHz highly digital transmitter capable of providing band shaped QPSK/16-QAM modulation for high data-rate applications with high energy efficiency. Injection-locked ring oscillator is used for multi-phase carrier generation which eliminates the use of power-hungry phase-locked loop. It also provides fast settling time that enables heavy duty cycling to maximize energy conservation. Direct modulation at power amplifier is adopted to simplify the transmitter architecture. Fabricated in 65 nm CMOS, the transmitter achieves maximum data rate of 50 Mbps/100 Mbps for QPSK/16-QAM with effective sideband suppression more than 38 dB. The chip occupies an active area of 0.08 mm and achieves a settling time of less than 88 ns. Under 0.77 V supply, it achieves an energy efficiency of 26 pJ/bit and 13 pJ/bit with and without band shaping respectively. The measured EVM is better than 6% for QPSK (at 50 Mbps) and 16-QAM (at 100 Mbps) while delivering -15 dBm of output power.

Noncoherent detection of convolutionally encoded continuous phase modulation

Abstract: The authors consider the error probability at large signal-to-noise ratios of rate-1/2 convolutionally encoded CPFSK (continuous-phase frequency-shift keying) with an optimum noncoherent detector on an additive white Gaussian noise channel. The performance is given in terms of a parameter called the minimum squared normalized equivalent Euclidean distance which plays the same role mathematically as the minimum squared normalized Euclidean distance used for coherent detectors. It is shown that by introducing convolutional coding the error performance is significantly improved. The authors propose a decoding algorithm for these convolutionally encoded CPM schemes which is based on a limited tree search algorithm and uses the maximum-likelihood decision rule for noncoherent detection. Computer simulations show that the degradation in error performance compared to the performance of the optimum coherent Viterbi detector is less than 1 dB with a relatively simple noncoherent detector on an additive white Gaussian noise channel for most of the schemes considered. >

Non data-aided estimation of the modulation index of continuous phase modulations

Abstract: In this paper, a new non data-aided estimator of the modulation index of continuous phase modulated (CPM) signals is proposed. It is based on the observation that the inverse of the index is the smallest positive real number a CPM signal should be raised to in order to generate a sinusoid of period 2T, where T is the symbol period. The asymptotic behavior of the estimator is studied. If N is the sample size, the estimation error is shown to converge to a non-Gaussian distribution at a rate of 1/N. Simulation results sustain the conclusions of the theoretical asymptotic analysis.