A rate-adaptive concatenated code, consisting of an outer staircase code and an inner polar code is proposed. Short blocklength inner polar codes offers rate-adaptivity and more than 0.35 dB gain compared to the 400ZR data-center-interconnect error-correcting code.

In this work, a multilevel coding (MLC) based coded modulation scheme with two degrees of freedom in rate flexibility is proposed and compared with a bit-interleaved coded modulation (BICM) scheme from a performance versus complexity perspective. The proposed MLC scheme is based on a rate flexible inner soft-decision polar code and utilizes an outer hard-decision staircase code structure as in the 400ZR concatenated forward error-correcting code. The performance of the MLC scheme is investigated for a range of inner code lengths, inner decoder list sizes, and signaling with 16 and 64 quadrature amplitude modulation, respectively. The MLC is designed such that a portion of the staircase encoded bits can bypass the inner code. The number of required inner soft-decision decoders can thus be reduced, thereby saving computational complexity. The proposed MLC scheme simultaneously offers up to a 53.7% reduction in the number of inner decoders and up to 0.55 dB of performance improvement when compared with the similar BICM approach.

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Fifth-generation communication demands seamless multi-giga-bit per second data transmission in its small-sized ultradense cells. The congestion-free millimeter-wave spectrum is the best option to be utilized for high data rate transmission. Generation and transmission of millimeter-wave signals in the electrical domain is challenging mainly owing to bandwidth limitation of electronic components. Therefore, optical generation and transmission of these high-frequency signals are a feasible option. In this work, we propose all-optical millimeter-wave signal generation and transmission in a centralized radio-over-fiber architecture. The proposed architecture performs all the major optical signal processing tasks at the central unit by eliminating the requirement of light sources and local oscillators at the multiple radio access units. Therefore, a potentially simplified and cost-effective solution for fifth-generation mobile networks is demonstrated through simulation results. Nonlinearity of the Mach-Zehnder modulator and of a highly nonlinear dispersion-shifted fiber is exploited to generate coherent optical carriers from a single centralized laser source instead of several separate laser sources. The coherent optical carriers are used to perform remote heterodyne detection at the radio access units and at the central unit to generate millimeter-wave signals. Each of the four radio access units receives data from the central unit at a rate of 512 Mbps over two subcarrier multiplexed signals. Each of the radio access unit transmits the uplink data received from the mobile units at a rate of 128 Mbps and centered at a frequency of 25 GHz. It has been demonstrated through simulations that the proposed system gives acceptable bit error rate results.