A physical layer encryption scheme based on population evolution iteration (PEI) and nonlinear companding is proposed to improve the security and reduce peak-to-average power ratio of the coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Simulation conducted in a 28Gbaud 16QAM system proves that the scheme can reduce the PAPR by 4dB, while the bit error rate of eavesdropper is about 0.5, which indicates that the scheme can guarantee the security on the premise of ensuring efficient transmission.

In this paper, a security enhanced physical layer encryption scheme is proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. This scheme is based on a concatenated inter-domain joint scrambling (CIJS) method, while adopting the three-dimension logistic sine cascading mapping (3D-LSCM) as a chaos key system to improve the security. Thrice inter-domain cat mappings are implemented, which fully exploits the characteristic domains of OFDM data and greatly increases the possible permutations. An experiment of the encryption scheme is realized successfully in a 16QAM CO-OFDM system at a symbol rate of 40 Gbaud over an 80 km standard single mode fiber. The experiment shows that no bit error rate (BER) and peak to average power ratio (PAPR) penalties are introduced in this scheme. The proposed 3D-LSCM chaos system shows superior properties of high sensitivity to initial values and improved uniform distribution, which guarantees the large entropy and further the system's security. This scheme can effectively prevent against a chosen-text attack which is the most effective attack method due to the extremely small tolerabledeviation and the large key space of 1.12 × 10 207 .

In this paper, we propose an optical physical layer encryption method to encrypt the signal of polarization division multiplexing (PDM) coherent optical communication system by introducing an artificially controlled fast rotation of the state of polarization (RSOP) into the signal. Simulations conducted in a 40 Gbps PDM-QPSK system show that the authorized user can successfully decrypt the received signal, while the eavesdroppers cannot derive useful information with bit error rates (BER) at 0.38~0.48, which shows that the method effectively improves the security of the system.

A physical-layer encryption scheme is proposed in coherent OFDM system using a two-dimensional chaotic mapping and Brownian motion. Simulations show that no OSNR penalty is introduced and the PAPR can be decreased by 1dB. © 2020 The Author(s).

One of the objectives of METIS-II project is to facilitate discussion on scenarios, use cases, KPIs and requirements for 5G, building upon the comprehensive work conducted in the METIS-I project and taking the work of other European projects as well as other bodies such as ITU-R, NGMN, etc. into account. This paper analyses the landscape of 5G use cases and presents METIS-II 5G use cases that cover the main 5G services, have stringent requirements and whose technical solutions are expected to serve other similar use cases as well. It also links these use cases to the business cases defined by 5G PPP so that requirements of vertical industries can be taken into account when designing the 5G Radio Access Network (RAN).

The base station (BS) density configuration is a crucial factor in improving energy efficiency (EE) in cellular networks, particularly when the sleeping strategy is used to reduce energy consumption. In this paper, the optimization of BS density for enhancing EE through traffic-aware sleeping strategies in both one- and two-tier cellular networks is researched, where the BS location is modeled as a Poisson point process. In the one-tier scenario, the EE optimization objective function is proved to be quasi-concave, and the optimal BS density solution is derived, where the maximum achievable EE is demonstrated to be independent of user density. In the two-tier scenario, both the activation probability of BSs and the coverage probability are analyzed, where the EE optimization objective function is proved to be not necessarily quasi-concave. To handle this nonconvex issue, an equivalent optimization problem that jointly optimizes the ratio and weighted sum of BS densities is proposed and solved by a dynamic gradient iterative algorithm. Meanwhile, a data fitting method is utilized to quantitatively analyze EE performances, in which the relationship between the optimal BS density and the user density is approximately linear when the user density is sufficiently high. Simulation results verify the relevant derivations and reflect that the sleeping strategy can not only save energy but improve the quality of radio links as well.