Utilizing Hilbert-pair-based digital filtering, intensity modulation and passive optical coupling, DSP-enabled flexible ROADMs are reported, which are free from both optical filters and O-E-O conversions and also offer excellent flexibility, colorlessness, gridlessness, contentionlessness, adaptability and transparency to physical-layer network characteristics. In this paper, the ROADM performance robustness against variations in numerous network design aspects is, for the first time, extensively explored in IMDD-based optical network nodes. Numerical results show that DSPs not only enable the ROADMs to dynamically and flexibly perform add/drop operations at wavelength, subwavelength and spectrally overlapped orthogonal sub-bands levels, but also considerably improve the ROADM performance robustness against variations in modulation formats, transmission system characteristics/impairments, as well as terminal equipment configurations. Index Terms-Digital filtering, digital signal processing (DSP), intensity modulation, reconfigurable optical add/drop multiplexer (ROADM), performance robustness.
A novel physical layer (PHY) transmission technique for increasing the channel capacity of transmission, termed as Orthogonal Generalized Frequency Division Multiplexing (OGFDM), has been proposed, investigated and evaluated in this paper. A combination of the Digital Hilbert Filter (DHF) with Generalized Frequency Division Multiplexing (GFDM) has been shown to double wireless channel capacity for each transmitted frequency sub-carrier at acceptable Bit Error Rate (BER) limits. By making use of the great properties of Hilbert transforms, orthogonality is achieved between the traditionally non-orthogonal GDFM subcarriers improving the BER and wireless channel capacity of the transmission. The OGFDM seems to combine the attributes of GFDM and Orthogonal Frequency Division Multiplexing (OFDM) in one sustainable system. The proposed solution achieves orthogonality between the filters of adjacent frequencies of subcarriers instead of between the frequencies of subcarriers themselves. Also, an OGFDM system model is presented, based on which, the relation between the main filter parameters and the system BER and channel capacity performance is specified in a wireless electrical back-to-back transmission system. Finally, by means of simulations, the impact of applying the proposed advanced filters on the aggregated system performance of the BER and channel capacity is shown in an Additive White Gaussian Noise (AWGN) wireless channel.
In this paper, a new multi-carrier candidate waveform for the future generation of mobile (5G) is introduced, explored and evaluated. The newly developed design of the Orthogonal Generalized Frequency division multiplexing (OGFDM) can improve the performance in terms of the channel capacity and Bit Error Rate (BER) for the wireless transmission of the multi-carrier system. In addition, compared to the most candidate waveform, Generalized Frequency Division Multiplexing (GFDM), the innovative multi-carrier OGFDM can double, boost and even maximize the capacity of wireless channel at the acceptable level of the BER. This is essentially achieved due to major adaptations have been made on the Filtration level, Oversampling level and Modulation level of the currently recommended GFDM. Thus, depending on the Digital Hilbert Filter (DHF), the presented solution can attain the orthogonality between the un-orthogonal filtered subcarriers of the multicarrier GFDM technique. Moreover, by utilizing an adjustable oversampling factor, the examined system can stay reliable even in the worst conditions of the wireless channel. Furthermore, employing the adaptive bit loading instead of the fixed modulation format, the announced waveform can reach the maximum rate of transmission with the venial limit of error. The main parameters of each promoted level are precisely specified in accordance with the optimum system performance. Besides, the different levels of the multi-carrier OGFDM are presented in the physical layer (PHY) of a wireless electrical back-to-back transceiver system. A MATLAB simulation was introduced to evaluate the system performance (BER & channel capacity) in presence of the Additive White Gaussian Noise (AWGN).
The Orthogonal Generalized Frequency Division Multiplexing (OGFDM) with Intra-Channel Interference Avoidance (ICIA) approach is, for the first time, proposed, explored and evaluated. Since the interference manipulation currently represents a hot topic for wireless mobile communication, the conventional approach of mitigating the interference is no longer acceptable. As a result, a novel method for addressing the interference between adjacent filtered sub-carriers (inphase/out-phase) is comprehensively investigated herein. The proposed approach utilises the oversampling factor to effectively avoid interference and improve the quality of service of affected filters under bad transmission states. Thus, this supportive method which is essentially aware of propagation conditions is employed for removing the roll-off (α) impact yet improving the level of Bandwidth (BW) efficiency for applied filters of the OGFDM waveform. Besides, in terms of the system performance, the trade-off relation between the channel capacity and the key Hilbert filter parameter is theoretically and practically discussed. This requires investigation of the influence of α factor on the maximum achieved bitrate at the acceptable limit of the Bit Error Rate (BER). A MATLAB simulation was introduced to test the performance characteristics of the proposed system in the physical layer (PHY) of an electrical back-to-back wireless transmission system.
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