Michael Schlosser

Backhaul requirements for inter-site cooperation in heterogeneous LTE-Advanced networks

In this paper, we provide an overview on backhaul requirements in mobile networks featuring inter-site cooperation. We consider a heterogeneous deployment, where small cells are embedded into macro-cells. For reducing inter-cell interference, we consider intra- and inter-site joint transmission (JT)-coordinated multi-point (CoMP) in fully flexible cooperation clusters. Backhaul traffic for a macro-cell site scales linearly with the number of small cells and multiplicative by introducing cooperation. All features in LTE-Advanced together push the backhaul traffic up to 100 Gbit/s per site. JT-CoMP is sensitive to the feedback delay.We consider an exemplary rural fiber to the home (FTTH) network as mobile backhaul and find that delays between adjacent sites are below 1 ms. Impairment effects due to the delay can be reduced by feedback compression, shorter delays in the air interface and Doppler-delay based channel prediction.

SDN-Enabled Sliceable BVT Based on Multicarrier Technology for Multiflow Rate/Distance and Grid Adaptation

We propose a sliceable bandwidth variable transceiver (S-BVT) architecture suitable for metro/regional elastic networks and highly scalable data center applications. It adopts multicarrier modulation, either OFDM or DMT, and a cost-effective optoelectronic front-end. The high-capacity S-BVT is programmable, adaptive, and reconfigurable by an SDN controller for efficient resource usage, enabling unique granularity, flexibility, and grid adaptation, even in the conventional fixed-grid networks. We experimentally demonstrate its multiple advanced functionalities in a four-node photonic mesh network. This includes SDN-enabled rate/distance adaptive multiflow generation and routing/switching, slice-ability, flexibility, and adaptability for the mitigation of spectrum fragmentation, as well as for a soft migration toward the flexi-grid paradigm.

Impact of deflection routing on TCP performance in optical burst switching networks

This work analyzes the behaviour of TCP connections in optical burst switching networks with deflection routing. A simplified model of an OBS network was implemented and a number of TCP based file transfer connections in the OBS network were simulated. Different TCP versions (Tahoe, Reno) in conjunction with different deflection ratios and burst loss probabilities were investigated and compared. The results show that deflection routing leads to a degradation of TCP performance, which is however much lower as in the case where the deflected bursts are dropped instead. The simulations were performed using the simulation program OPNET modeler.

Robust Optical Wireless Link for the Backhaul and Fronthaul of Small Radio Cells

This paper summarizes recent work on the use of optical wireless links as a robust outdoor backhaul solution for small radio cells, such as WiFi, LTE and 5G, over distances between 20 and 200 m. Results of a 5-month outdoor field trial in Berlin, Germany, indicate that the visibility range was never below 180 m, with more than 1 km in 99% of all times during this period. Rate-adaptive transmission proved to improve the availability remarkably in the occasional presence of fog or sunlight. A mathematical model of the backhaul link including these impairments is presented and implemented to obtain an optimized link design. A prototype was realized, accordingly, using low-cost optoelectronic components and a 1 Gb/s baseband chipset. Gross data rates of 800, 500, and 225 Mb/s have been achieved in real-time operation over 20, 100, and 215 m outdoor link distance, respectively, with 2 ms latency at 95% load. Finally, we discuss further evolution towards 5G mobile networks.

Performance of fixed-length, variable-capacity packets in optical packet-switching networks

We present the performance of fixed-length, variable-capacity (FL-VC) packets in optical packet-switching (OPS) networks. We show how FL-VC achieves an effective balance between implementation feasibility and performance of the applications using the network. Focusing on metropolitan area networks and real-world file distributions, we also show that an adequate selection of packet duration leads to nearly optimal application throughput with respect to conventional variable-length, fixed-bit-rate packets (VL-FBR), and that this optimal packet duration is robust against changes in the workload. Finally, we show that a single fiber delay line per OPS switch managed by a first-fit scheduler can increase throughput to levels similar to those obtained by random access buffers.

Optical wireless LED link for the backhaul of small cells

We demonstrate experimentally that optical wireless (OW) links using an infrared LED can meet the bitrate, distance and latency requirements for low-cost small-cell wireless backhaul in Long-Term Evolution (LTE) mobile networks.

Optical wireless communication for backhaul and access

We highlight new applications for optical wireless communication (OWC) as a mobile backhaul for WiFi, LTE and 5G and as a new access technology in the Internet of Things (IoT) where it enables secure and reliable communications at low latency.

Network virtualization, control plane and service orchestration of the ICT STRAUSS project

Emerging cloud applications such as real-time data backup, remote desktop, server clustering, etc. require not only more traffic being delivered between datacenters, but also dedicated and application-specific virtual optical network (VON) services to support each applications QoS and SLA level. On the other hand, another requirement is to support end-to-end network service provisioning across multiple VONs comprising different transport (e.g. Flexi-grid DWDM OCS, OPS, etc) and control plane technologies (e.g., centralized OpenFlow or distributed GMPLS). This paper presents the preliminary architecture of the network virtualization, control and orchestration layers proposed in the STRAUSS project.

SDN-enabled sliceable BVT based on multicarrier technology for multi-flow rate/distance and grid adaptation

We experimentally demonstrate multiple advanced functionalities of a cost-effective high-capacity sliceable-BVT using multicarrier technology. It is programmable, adaptive and reconfigurable by an SDN controller for efficient resource usage, enabling unique granularity, flexibility and grid adaptation, even in conventional fixed-grid networks.

Estimating the mobile backhaul traffic in distributed coordinated multi-point systems

Optical and microwave engineers ask for the required data rates when developing fourth generation (4G) mobile backhaul solutions. Backhauling emerges into an important question since advanced interference mitigation techniques are used to improve the performance at the cost of higher backhaul traffic. In this paper, we provide an efficient method for estimating the backhaul traffic when using joint transmission (JT) coordinated multi-point (CoMP). With this technique, a cluster of base stations (BSs) performs joint signal processing to cancel the mutual interference between adjacent cells. The information exchange between the BSs depends on the cluster size that can be very dynamic depending on the actual interference situation at the mobile terminal. We observe that, on average, 2/3 of the exchange requires inter-site links. This simplifies the analysis and we can refer to the cluster size distribution to compute the backhaul traffic. Results depend on a threshold in the mobility management and on the antenna down-tilt. During busy hours, operators can serve up to 1.3 Gb/s per cell in 50 MHz bandwidth. Backhaul traffic for JT CoMP can reach 5 and 20 Gb/s per triple-sector site for up- and downstream, respectively.