Most recent works in device-to-device (D2D) underlay communications focus on the optimization of either power or channel allocation to improve the spectral efficiency, and typically consider uplink and downlink separately. Further, several of them also assume perfect knowledge of channel state information (CSI). In this paper, we formulate a joint uplink and downlink resource allocation scheme, which assigns both power and channel resources to D2D pairs and cellular users in an underlay network scenario. The objective is to maximize the overall network rate while maintaining fairness among the D2D pairs. In addition, we also consider imperfect CSI, where we guarantee a certain outage probability to maintain the desired quality-of-service (QoS). The resulting problem is a mixed integer non-convex optimization problem and we propose both centralized and decentralized algorithms to solve it, using convex relaxation, fractional programming, and alternating optimization. In the decentralized setting, the computational load is distributed among the D2D pairs and the base station, keeping also a low communication overhead. Moreover, we also provide a theoretical convergence analysis, including also the rate of convergence to stationary points. The proposed algorithms have been experimentally tested in a simulation environment, showing their favorable performance, as compared with the state-of-the art alternatives.

The NorNet testbed (https://www.nntb.no) is an Internet testbed platform for research on multi-homed systems. The particular property of multi-homed systems is to be connected to multiple Internet Service Providers (ISP) simultaneously. Its initial purpose is of course to still provide connectivity in case of ISP/network failures. But does it really work that well, also with current protocols and applications? And redundancy does not come for free. A user connected to multiple ISPs will also receive multiple Internet bills each month. So, is there a possibility to make further use of multi-homing in the usual case where nothing goes wrong? Obviously, there are a lot of interesting research questions, which need to be examined in realistic Internet setups! Therefore, we are building up the NorNet open Internet testbed platform as a Linux- and Open-Source-software-based infrastructure, which currently spreads over multiple sites in different countries.

NorNet makes extensive use of advanced Linux features like Kernel-based Virtualisation (KVM), Linux Containers (LXC), BTRFS file system features, IP routing rules, Stream Control Transmission Protocol (SCTP), Multi-Path TCP (MPTCP), and many more. The goal of this talk is therefore to present an overview of the testbed, its underlying Linux features, and how they are combined to provide the multi-homing features to the various testbed users. This particularly includes an overview of how to make use of multi-path transport with MPTCP – based on the Linux MPTCP implementation – in multi-homed environments. The idea is to provide guidelines for also utilising multi-homing features in own projects.