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Published in Lal Chand Godara, Handbook of Antennas in Wireless Communications, 2018
In considering orthogonal FSK modualtion for fading channels, the use of MFSK with M = 8 or larger, is useful because its error performance is better than binary signaling. In slow Rayleigh-fading channels, binary DPSK and 8-FSK perform within 0.1 dB of each other [19]. At first glance, one might argue that a higher order orthogonal alphabet expands the transmission bandwidth, which at some point may cause the coherence bandwidth of the channel to be exceeded, leading to frequency-selective fading. However, for MFSK, the transmission bandwidth that must be available is much larger than the bandwidth of the propagating signal. For example, consider the case of 8-FSK and a symbol rate of 10,000 symbols per second. The transmission bandwidth is MRs = 80,000 Hz. This is the bandwidth that must be available for the use of the system. However, each time that a symbol is transmitted, only one single-sideband tone (having a spectral occupancy of 10,000 Hz) is sent — not the whole alphabet. In considering PSK modulation for fading channels, higher order modulation alphabets perform poorly. MPSK with M = 8 or larger should be avoided [19]. Example 2 that follows examines a mobile communication system to substantiate such avoidance.
Spread Spectrum Communications
Published in Jerry D. Gibson, The Communications Handbook, 2018
Laurence B. Milstein, Marvin K. Simon
where p(t) is again the basic pulse shape having a duration Th, called the hop time, and {0J is a sequence of random phases associated with the generation of the hops. FH modulation is traditionally used with multiple-frequency-shift-keyed (MFSK) information signals, which have the complex form exp{ j[2nfc + d(t))t]}, where d(t) is an M-level digital waveform (M denotes the symbol alphabet size) representing the information frequency modulation at a rate 1/TS symbols/s (sps). As such, an FH/MFSK signal is formed by complex multiplying the MFSK signal by c(t) resulting in the real transmitted signal
Design and Implementation of an Enterprise Credit Risk Assessment Model Based on Improved Fuzzy Neural Network
Published in Applied Artificial Intelligence, 2023
It is difficult to maintain phase coherence in the transmission of corporate financial credit data. Therefore, the information modulation technique adopted is usually Multi-ary Frequency Shift Keying (MFSK) or DPSK. MFSK modulation uses the mutual transformation between M carrier frequencies to transmit log2M-bit digital signals, which are generally expressed as