Packet-based fronthaul (FH) transport networks are promising for future centralized radio access networks (C-RANs), which support statistical multiplexing via flow scheduling. With stringent requirements on FH delay, the FH network is time sensitive. Targeting to minimize the maximum FH delay of all packets, this paper investigates the optimized flow scheduling in the packet-based FH network. Due to the high complexity of optimal solutions, a heuristic higher rate flow scheduled later (HRSL) scheme is proposed to achieve good performance with a low complexity. The main idea is to schedule the higher-rated flow with a lower priority, because packets in the higher-rated flow have a larger solution space to be scheduled with a smaller delay. It is proved that using HRSL, each packet must have a transmission position and no packet will be discarded during scheduling. Moreover, the asymptotic delay of HRSL is derived when the number of flows is sufficiently large. We show that the delay performance of HRSL approaches to the optimal one and yields a reduction of up to 92.6% compared to existing schemes. The properties of HRSL are also verified via simulations. If the required delay is larger than the asymptotic delay performance, the FH network with HRSL can always deliver packets in time, no matter how many flows are scheduled and what the rates of flows are.

Next generation fronthaul interface (NGFI) is a promising fronthaul (FH) interface for the future centralized radio access network (C-RAN), which is packet-based and supports statistical multiplexing via flow scheduling at the node in the FH network. However, FH delay may be increased by flow scheduling. Targeting to minimize the maximum FH delay, this paper investigates the optimized flow scheduling in NGFI. Due to the high complexity of optimal solution, an intuitive low rate scheduled first (LRSF) scheme is proposed to achieve the good performance with low complexity. The main idea is to schedule the flow of lower rate with higher priority, so that the maximum FH delay of packets in the flow with lower priority can be reduced. Simulation results show that the delay performance of LRSF approaches to the optimal one and outperforms existing schemes.