Optimization of latency-aware flow allocation in NGFI networks

Klinkowski, Mirosław

doi:10.1016/j.comcom.2020.07.044

Cited by 17 publications

(22 citation statements)

References 27 publications

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“…In a network in which the cost of using PPs is diversified at particular locations, for instance, due to different space rental prices or the availability of renewable energy sources, it is desirable to design the network in such a way that it would entail the lowest investment and operational costs for the network operator. However, in prior works concerning a similar problem [11], [12], the assumption was that all PPs involve the same cost and optimization of the use of PPs was not addressed. Therefore, to fill the research gap, this work focuses on the PP cost-aware DU placement and FH/MH flow routing (PPC-DUP-FR) problem.…”

Section: A Research Contributionmentioning

confidence: 99%

“…Therefore, to fill the research gap, this work focuses on the PP cost-aware DU placement and FH/MH flow routing (PPC-DUP-FR) problem. The problem is particularly challenging in packet-switched xHaul networks, where dynamic, non-deterministic latencies of data flows caused by buffering of packets in the switches have to be accounted for during DU placement and flow routing decisions [11]. In this regard, the network optimization process can be supported by applying analytical latency estimators.…”

Section: A Research Contributionmentioning

confidence: 99%

“…In this regard, the network optimization process can be supported by applying analytical latency estimators. In this work, we use a reliable worst-case flow latency model that assures a tighter estimation of flows latencies than the model used in our previous works [11], [12].…”

Section: A Research Contributionmentioning

confidence: 99%

“…Heuristic algorithms were developed in [33] and [34] to solve the problem of routing with latency and flow scheduling constraints in a packet-switched (bridged) network, but the algorithms did not consider the optimization of the DU/CU placement. In [11] and [12], MIP models were proposed to optimize the allocation of DU and DU/CU entities, respectively, in packet-switched xHaul networks. However, these works were oriented on straight minimization of the number of PP sites, which did not comprise a more realistic scenario in which PP activation and processing costs are diversified in the network.…”

Section: Related Workmentioning

confidence: 99%

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Cost-Aware DU Placement and Flow Routing in 5G Packet xHaul Networks

2023

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Packet-switched xHaul networks based on Ethernet technology are considered a promising solution for assuring convergent, cost-effective transport of diverse radio data traffic flows in dense 5G radio access networks (RANs). A challenging optimization problem in such networks is the placement of distributed processing units (DUs), which realize a subset of virtualized baseband processing functions on general-purpose processors at selected processing pool (PP) facilities. The DU placement involves the problem of routing of related fronthaul and midhaul data flows between network nodes. In this work, we focus on developing optimization methods for joint placement of DUs and routing of flows with the goal to minimize the overall cost of PPs activation and processing in the network, which we refer to as the PPC-DUP-FR problem. We account for limited processing and transmission resources as well as for stringent latency requirements of data flows in 5G RAN. The latency constraint makes the problem particularly difficult in a packet-switched xHaul network since it involves the non-linear and dynamic estimation of the latencies caused by buffering of packets in the switches. The latency model that we apply in this work is based on worst-case calculations with improved latency estimations that skip from processing the co-routed, but non-affecting flows. We use a mixed-integer programming (MIP) approach to formulate and solve the PPC-DUP-FR optimization problem. Moreover, we develop a heuristic method that provides optimized solutions to larger PPC-DUP-FR problem instances, which are too complex for the MIP method. Numerical experiments performed in different network scenarios indicate on the effectiveness of the heuristic in solving the PPC-DUP-FR problem. In particular, the heuristic achieves up to 63% better results than MIP (at the MIP optimality gap equal to 76%) in a medium-size mesh network, in which the MIP problem is unsolvable for higher traffic demands within reasonable runtime limits. In larger networks, MIP is able to provide some results only for the PPC-DUP-FR problem instances with very low traffic demands, whereas the solutions generated by the heuristic are at least 83% better than the ones achieved with MIP. Also, the analysis performed shows a significant impact of the PP cost factors considered and of the level of cost differentiation of PP nodes on the overall PP cost in the network. Finally, simulation results of a case-study packet xHaul network confirm the correctness of the latency model used.

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Section: A Research Contributionmentioning

confidence: 99%

Section: A Research Contributionmentioning

confidence: 99%

Section: A Research Contributionmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 99%

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Cost-Aware DU Placement and Flow Routing in 5G Packet xHaul Networks

2023

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“…Namely, in the analysis performed in this work, we consider that the one-way latency budget of latency-sensitive flows is equal to 100 µs (according to Reference [29]). Within this budget, we assume that 50 µs is reserved, among others, for the store-and-forward operations in the switch (a few µs, as mentioned in Annex B in Reference [9]), the transmission time of frames (not exceeding a few µs in a 100 Gbps optical link [30]), and queuing latency (up to some tens of µs), whereas the remaining 50 µs is left for signal propagation in the optical fiber. Note that, in the transmission system studied in this work, the buffering of frames in the xHaul network occurs once for each transmission direction, namely during aggregation of radio data flows into wavelength connections at the remote TSN switch and at the switch located in the hub, respectively, for uplink and downlink direction.…”

Section: Latency Constraintsmentioning

confidence: 99%

Planning of Optical Connections in 5G Packet-Optical xHaul Access Network

Klinkowski

Jaworski

2022

Applied Sciences

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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.

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