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Based on a hierarchical cloud-fog computing-enabled paradigm, fog radio access networks (F-RANs) can provide abundant resource to support the future mobile artificial intelligent services. However, due to the differences of computation and communication capabilities at the cloud computing center, the fog computing based access points (F-APs), and the user devices, it is challenging to propose efficient computation offloading strategies to fully explore the potential of F-RANs. In this paper, we study the design of computation offloading in F-RANs to minimize the total cost with respect to the energy consumption and the offloading latency. In particular, a joint optimization problem is formulated to optimize the offloading decision, the computation and the radio resources allocation. To solve this non-linear and non-convex problem, an iterative algorithm is designed, which can be proved to converge a stationary optimal solution with polynomial computational complexity. Finally, the simulation results are provided to show the performance gains of our proposed joint optimization algorithm.

Fog radio access network (F-RAN) is a promising paradigm for the future wireless networks, it shows a trend of integrating communication and computation. In this paper, we study resource allocation for computation offloading in F-RANs, in which the computation and radio resources are considered. To minimize the total cost with respect to the energy consumption and the offloading latency, a joint optimization problem is formulated to optimize the offloading decision, the CPU-cycle frequency and the transmit power control. To solve this non-linear and non-convex problem, we propose an iterative algorithm, which can be proved to converge a stationary optimal solution. Finally, we provide the simulation results to show the convergence performance and the total cost performance gains of our proposed joint optimization algorithm.

Fog radio access networks (F-RAN) is used to meet high requirements of the fifth-generation (5G) mobile communication. With scale of terminals expanded, frequency spectrum becomes a bottleneck of developing F-RANs, and traditional orthogonal multiple access (OMA) is not highly effective on resource utilization. To improve spectrum efficiency, sparse code division multiple access (SCMA) is presented as a promising technique. In this paper, the performance of a SCMA-based scheme in F-RANs is evaluated. In particular, a lower bound of the average outage probability of a typical user is provided based on stochastic geometry, which can give some insights on how to improve the transmission reliability of SCMA. Meanwhile, a lower bound of capacity on a subcarrier is derived. Simulation results are provided to validate the accuracy of analysis and show the performance gain of SCMA compared with OMA.

System synchronization between the user equipment (UE) and the base station (eNodeB) is a fundamental physical layer procedure in the cellular system and performed by synchronization signal. New Radio (NR) synchronization signal is expected to have the wider band reserved, which enables the use of the longer sequence than that in Long Term Evolution (LTE). This paper simulates the downlink (DL) initial synchronization procedure for NR in 5G and evaluates the NR primary synchronization signal (NR-PSS) design with various lengths. To accomplish the DL initial synchronization at the UE, the NR-PSS is firstly detected in the time domain using a matched filter, and then the carrier frequency offset (CFO) is the sum of the integer frequency offset (IFO) and the sum of the fractional frequency offset (FFO). After compensating the CFO of the received signal, we detect the NR second synchronization signal (NR-SSS) in the frequency domain. To evaluate the NR-PSS design with various lengths, the performance of the residual timing offset and residual frequency offset is considered. The simulation results show that the performance of the residual timing offset with the longer sequences is better and the length of the NR-PSS has no impact on the performance of the residual frequency offset. Thus we propose longer sequences in the NR-PSS design when the performance of the residual timing offset and the residual frequency offset is only considered.