Abstract
One of the main challenges in dense 5G radio access networks (RANs) is provisioning of low-cost connectivity between a large number of antennas, located at remote sites, and a central site (hub) in which baseband processing functions are performed. Packet-switched Ethernet and wavelength division multiplexing (WDM) are two principal transport network technologies enabling the reduction of the demand for direct optical fiber connections between the antennas and the hub. Whereas Ethernet allows for statistical multiplexing of multiple xHaul (fronthaul/midhaul/backhaul) flows and their aggregation in a high-capacity transmission link, WDM makes it possible to establish a number of such links (using different wavelengths) in a single optical fiber. Additional savings in the amount of fibers required can be achieved by means of optical add-drop multiplexers (OADMs) that allow for obtaining access to unused wavelengths by intermediate remote nodes, whenever the capacity on the WDM system is not fully utilized by the end remote node. In this work, we focus on the problem of planning optimal fiber connections, including the placement of OADMs for a set of wavelength demands at remote sites, with the aim of minimizing the amount of fibers used in a packet-optical xHaul access network carrying 5G traffic. We consider a passive WDM system in which the maximum transmission distance, estimated using an optical power-budget model, depends on the number of OADMs that are present on the transmission path. To formulate and solve the optimization problem, we make use of integer linear programming (ILP). We apply the ILP model in network analysis. In particular, by means of numerical experiments performed for two different network topologies, we study the impact of traffic load (in terms of the number of requested wavelengths) and optical multiplexer loss on the number of transmission paths that have to be established in the network. Obtained results show that the savings in fiber connections of up to 65% can be achieved in a packet-optical xHaul network if OADMs are used when compared to the scenario without OADMs.
Highlights
Telecommunication networking is undergoing a profound transformation related to the deployment of 5G networks [1]
The distributed unit (DU) and central unit (CU) may be placed at different network locations in accordance with particular requirements of diverse 5G services, which can be classified as enhanced mobile broadband, ultra-reliable and low-latency communications (URLLC), and massive machine-type communications
We have studied the problem of planning optimal transmission paths, realized using optical fiber connections and optical add-drop multiplexers, in a 5G packet-optical xHaul access network
Summary
Telecommunication networking is undergoing a profound transformation related to the deployment of 5G networks [1]. The application of an OADM at an intermediate site increases utilization of the WDM link, and, at the same time, it releases from the need to establish a dedicated transmission path between the hub and the site It leads to the reduction of the number of fiber connections and installed WDM equipment, which translates into lower network deployment costs [14,15,16]. A commercial solution available under the trade name flexiHaul has been proposed for a 5G packet-optical xHaul access network This solution consists of a TSN Ethernet switch [17] and a passive WDM system xWave 400G [16], which allows for the aggregation of wavelengths on optical paths by means of OADMs. In a 5G access transport network based on a transmission system with the above discussed features, a basic network design problem concerns planning of optical connections between remote sites and a hub site.
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