Inhalt des Dokuments
Software-Defined Wireless Networking
In the area of Software-Defined Wireless Networking (SDWN) we work on the following topics:
Orchestration of Virtual Wireless Network Functions
Today's demand for flexibility in WiFi network deployments along with more stringent requirements on performance and management stand in stark contrast to today's ossified, expensive, and vertically integrated solutions. In particular, the current WiFi architecture ties wireless network functions either to a single Wireless LAN Controller or to a single Access Point (AP). In the first case, a controller typically manages a set of APs through a standardized (CAPWAP or LWAPP) or proprietary (RESTful APIs) control protocol. Unfortunately, today's standardised are inflexible and limited (and have hardly been implemented and updated (to support newer amendments to the 802.11 standard) due to legal issues.
Research goes in the direction of a modularized Software-Defined Wireless Network that follows the trend of NFV, i.e., realizing function blocks as virtual network functions (VNFs). Specifically, we research on an WiFi architecture which follows a functional decomposition of the WiFi building blocks where individual (virtualized and programmable) WiFi function blocks are allocated (and composed) where and when they are most useful. This includes research in the direction of the decomposition of the wireless building blocks, proper abstractions for the wireless building blocks and virtual network functions orchestration.
Odin: Programmatic Orchestration of WiFi Networks
With wireless technologies becoming prevalent at the last hop, today’s network operators need to manage WiFi access networks in unison with their wired counterparts. However, the non-uniformity of feature sets in existing solutions and the lack of programmability makes this a challenging task. With Odin, we present an SDN-based solution to bridge this gap. With Odin, we make the following contributions: (i) Light Virtual Access Points (LVAPs), a novel programming abstraction for addressing the IEEE 802.11 protocol stack complexity, (ii) a design and implementation for a Software-Defined Wireless Network (SDWN) architecture based on LVAPs, and (iii) a prototype implementation on top of commodity access point hardware without modifications to the IEEE 802.11 client, making it practical for today’s deployments. To highlight the effectiveness of the approach we have demonstrated six WiFi network services on top of Odin including load-balancing, mobility management, jammer detection, automatic channel-selection, energy management, and guest policy enforcement.
Please visit sdn.inet.tu-berlin.de  for more information.
OpenSDWN: Programmatic Control over Home and Enterprise WiFi
OpenSDWN combines the benefits of WiFi, SDN, and NFV, i.e, , a novel Software-Defined Wireless Networking architecture. OpenSDWN exploits datapath programmability to enable service differentiation and fine-grained transmission control, facilitating the prioritization of critical applications. OpenSDWN implements per-client virtual access points and per-client virtual middleboxes, to render network functions more flexible and support mobility and seamless migration. OpenSDWN can also be used to out-source the control over the home network to a participatory interface or to an Internet Service Provider.
Please visit opensdwn.com  for more information.
Applying the concept of SDN to WiFi networks is challenging, since wireless networks feature many peculiarities and knobs that often do not exist in wired networks: obviously, WiFi communicates over a shared medium, with all its implications, e.g., higher packet loss and hidden or exposed terminals. Moreover, wireless links can be operated in a number of different regimes, e.g., transmission rate and power settings can be adjusted, RTS/CTS mechanisms can be used.
Indeed, due to the non-stationary characteristic of the wireless channel, permanently adjusting settings such as transmission rate and power is crucial for the performance of WiFi networks and brings significant benefits in the service quality, e.g., through reducing the packet loss probability. Today’s rate and power control is mainly done on the WiFi device itself. But it is rarely optimized to the application-layer demands and their diverse traffic requirements, e.g., their individual sensitivity to packet loss or jitter. Therefore, if SDN for wireless can provide mechanisms to control the WiFi-specific transmission settings on a per-slice, per-client, and per-flow level, traffic and application-aware optimizations are feasible.