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.

Reduced Complexity Detectors for Continuous Phase Modulation Based on a Signal Space Approach

Abstract: Optimum detectors for CPM use in general a large number of filters in order to calculate the optimum metrics. In this paper, we propose correlation detectors that calculate its metrics in a subspace of the signal space. The subspace is selected such that the asymptotic error performance is optimized for the given dimensionality. We focus on noncoherent detectors but show also some results for coherent detectors. The subspace metric calculation is combined with previously published reduced complexity decoding algorithms such as the SAN(B) and RSSD algorithms. Optimum subspace correlation detectors with different number of filters are found for both binary and quaternary CPM schemes. Their error performance on an AWGN channel is derived analytically through the use of a minimum Euclidean distance approach and is also simulated through the symbol error probability. Comparison is done with the optimum detectors. A close agreement between minimum distance and simulated symbol error probability is found for all considered detectors. We find that in most cases only 4 to 6 matched filters are needed in order to obtain a performance that is close to optimum. This corresponds to at least a five-fold reduction in number of filters and with the reduced complexity search algorithms for making symbol decisions this leads to a dramatic reduction in overall complexity.

1.5- $\mu{\rm m}$ 10-Gb/s VCSEL Link for Optical Access Applications

Abstract: We experimentally demonstrate the power budget improvement of a 10-Gb/s vertical-cavity surface-emitting laser (VCSEL) link by utilizing continuous-phase frequency-shift keying (CPFSK)/amplitude-shift keying (ASK) modulation format. We first measure the frequency modulation (FM) response of the VCSEL from 10 kHz to 10 GHz and then exploit dc-balanced line coding to utilize the flat region of the FM response. The CPFSK/ASK signals are generated by directly modulating the VCSEL and utilizing a delay interferometer (DI) for FSK-to-ASK conversion. We successfully transmit the signals over a 50-km dispersion-uncompensated link by optimizing the free-spectral range of the DI. Using the proposed scheme, we achieve > 5-dB improvement in the power budget compared with a conventional VCSEL link.

Trellis-coded 8PSK with embedded QPSK

Abstract: A coded eight-phase-shift-keying (C8PSK) method is described that is characterized by a quaternary phase-shift-keyed signal embedded in the modulated sequence. This method is a double-trellis-coded modification of the well-known C8PSK and is referred to as MC8PSK. Five coded bits are generated from four user bits in a single coding step and then mapped to an 8PSK symbol followed by a QPSK symbol. Given comparable decoder or receiver complexity, the coding gains of C8PSK and MC8PSK are comparable. Advantages of MC8PSK concern carrier synchronization. With C8PSK, problems with carrier phase tracking are encountered. With MC8PSK, these can be avoided, since carrier phase control can be based on the embedded QPSK. For some codes, error-free decoding is achievable in any locking condition of a QPSK-dependent PLL (phase locked loop), making synchronization and decoding especially simple. The partitioning of the channel symbol set, the associated bit mapping, and the code design are treated in order to describe MC8PSK. Aspects of receiver synchronization are discussed for C8PSK and for MC8PSK, focusing on QPSK phase-detection principles. The implementation of a four-state MC8PSK modem for an information rate of 2.048 Mb/s is described, and experimental results demonstrating the very robust carrier synchronization are presented. >

Sliding window-frequency domain equalization for multi-mode communication systems

Abstract: Future wireless communications should be designed efficiently to support multi-mode operations for different types of applications, such as machine-to-machine, video streaming, web browsing and voice. In the physical layer multi-mode operation could include the coexistence of single carrier and multicarrier modulations. To reduce overall complexity and power consumption, it is highly desirable to design the receiver such that some of the components are shared or reused by multiple modulation schemes. In this paper we propose a receiver architecture which is composed of a common channel equalizer for all carrier modulation schemes. Furthermore, we investigate the feasibility of using a well-studied time domain equalizer designed for single carrier modulation, i.e., the sliding window-frequency domain equalizer (SW-FDE) for general multicarrier modulation (MCM) receivers. As a specific illustration of the concept, we present the application of this equalizer to an OFDM-offset QAM system.

Improving the bandwidth efficiency and of CPM signals via shaping and iterative detection

Abstract: In this paper, we investigate the effects of shaping on the bandwidth efficiency and performance of continuous phase modulated (CPM) signals. We show that, theoretically, by properly shaping the unmodulated signal, better bandwidth efficiency and performance can be obtained. We then develop the soft-input soft-output (SISO) de-shaper for trellis shaping and block shaping schemes. For a coded, shaped CPM system, the SISO de-shaper enables joint decoding and de-shaping via iterative detection. We demonstrate that using the SISO deshaper, together with iterative decoding and de-shaping, the theoretical advantage of shaping can be realized with practical complexity