## 1 Introduction
Moreover, Ethernet supports the virtualization techniques and OAM (operations, administration, and management) functionalities, which make them more suitable to connect the RRHs with the BBU pool through the fronthaul bridged networks. However, the Ethernet networks that use the legacy quality of service (QoS)-aware routing [15] and packet forwarding schemes [16] yield the per-hop latency of about one millisecond and PDVs of up to hundreds of microseconds, which are much higher than the eCPRI traffic requirements [10; 17]. A major cause in Ethernet systems for not complying with the eCPRI requirements is the non-consideration of frame-level queuing delays at the bridging nodes, which are caused by the globally synchronized eCPRI bursts flowing to and from the RRHs at different line rates. Despite the utilization of the  
Figure 1: Cloud radio access networks (C-RANs) architecture for envisioned 5G cellular systems. QoS-aware forwarding schemes in the optical fronthaul bridged networks, the queuing delays among the burst of eCPRI streams are high, which increases the E2E latencies to an unacceptable level [18]. The queuing delays and E2E latencies become more critical in capacity-constraint Ethernet-based fronthaul bridged networks (EFBNs) [13]. For enhancing the capability of economically affordable and ubiquitously deployed Ethernet networks to transport the eCPRI streams at tolerable latencies, a novel packet forwarding mechanism that would efficiently utilize the limited Ethernet bandwidths and yield the low queuing delays at intermediate bridges is vital. Therefore, this paper proposes the E2E latency-aware path selection and packet transmission schemes that guarantee the low queuing delays in the EFBNs and retain the E2E latencies of maximum eCPRI streams closer to the threshold by taking advantage of the virtualization and OAM capabilities of the Ethernet systems. The proposed latency-aware path selection scheme assures the lowest E2E latencies in the fronthaul bridged networks by considering the frame-level queuing delays of eCPRI bursts. The proposed packet forwarding scheme mitigates the delays of eCPRI streams that experience high latency by slightly increasing the queuing delays of traffic streams that experience low latency. As a result, for all traffic streams, tolerable E2E latencies can be realized in the EFBNs. The computer simulations are undertaken on varied and realistic scenarios. The simulation results confirmed that the proposed schemes maximize the simultaneous transmissions of eCPRI streams of up to 100 Gbps without violating the QoS requirements as well as improve the link distances, whereas such performance is not guaranteed with the existing schemes. Moreover, the transmissions of time-sensitive eCPRI streams at tolerable latencies with the proposed schemes through the leveraging Ethernet links significantly reduced the CAPEX and OPEX of deploying extortionate optical links in fronthaul bridged networks. Hence, without hardware upgradations, the performance of low-cost Ethernet networks can be improved with the proposed schemes, which can be programmed at the intermediate nodes of the EFBNs using the OpenFlow protocols and software-defined networking (SDN) techniques [19]. The rest of the manuscript has the following organization. Section 2 introduces the state-of-the-art work on the CPRI and Ethernet-based fronthaul networks. Section 3 formulates the measurement procedures for the end-to-end latencies and distances in the EFBNs. Section 4 introduces the proposed transport schemes for the EFBNs. Section 5 presents the simulation setup for evaluating the proposed schemes. The results of the proposed schemes and comparison with the existing techniques are presented in Section 6. Finally, conclusions are provided in Section 7.