QoS abstraction layer in 4G access networks

In the context of heterogeneous wireless networks, or 4G networks, a number of problems are yet to be solved. One of these problems is the lack of Layer 2 QoS provisioning in heterogeneous networks, mainly due to the non-uniform nature of the QoS models and service interfaces among different wireless technologies. In addition, 4G access networks may include Access Points with no dedicated channel to control their QoS capabilities. An even more demanding scenario involves concatenated Access Points and the need to control and coordinate the QoS provisioning among them. Other problems in need to be addressed include coordination of L3 QoS with L2 QoS and mobility, and L2 multicast with QoS. In order to help solving these problems, we propose a QoS Abstraction Layer, which is located between layers 2 (link) and 3 (network), in the control plane; it hides from the upper layers the QoS reservation details of the technologies in use, as well as the layer 2 network topology. An abstract QoS service interface is provided to L3 QoS management modules, supporting primitives to reserve or modify L2 QoS resources, represented as abstract QoS parameters. An associated signalling protocol makes the QoS requests be communicated to the relevant QoSAL-enabled L2 nodes; discovery of the correct path to the mobile node in an L2 access network, and translation of abstract QoS parameters into technology-specific QoS parameters are also properties of the QoSAL. The service interface also features primitives to query available resources in Access Points, as well as notifications when the free resources drop below a certain threshold, which can be used to trigger network initiated handover for purposes of load balancing. Moreover, asynchronous notifications of degradation in existing QoS reservations are also defined, allowing applications to adapt to changing link conditions, among other cross-layer optimisations. Also featured are primitives designed for integration with L3 mobility, and multicast QoS. Finally, the architecture follows a modular design, with technology-dependent aspects separated into their own “driver” modules, allowing simpler development of QoS support for new technologies, without changing any other part of the access network infrastructure. As proof of concept, a prototype implementation of the QoS Abstraction Layer was developed and tested. The results obtained show that the prototype is correctly implementing the QoS and mobility integration primitives, as well as automatic path discovery to the mobile node. The resulting work represents a contribution to QoS in packet switched wireless networks, as it is specifically designed to bridge the gap between L3 QoS and L2 QoS. The definition of the abstract QoS interface is by itself an important achievement; also relevant is the way in which the signalling protocol solves the problems associated with the forwarding algorithm of IEEE 802.1D learning bridges.