In the HSDPA (High-Speed Downlink Packet Access) Iub Transport Network (TN) which connects the Radio Network Controller with base stations (Node Bs), congestion control is needed. Because of the TN's often narrow resources, fairness of resource sharing is an important issue. Basic Additive Increase Multiplicative Decrease (AIMD) congestion control guarantees convergence to fairness in the long run; all flows converge to an equal share of resources in steady state, where no flows join or leave. However, incoming flows decrease the level of fairness, that is why transient fairness should be taken into account as well. This paper proposes a method which provides fairness-optimal initial rate for incoming HSDPA flows. The proposed method improves average fairness. The method can be applied in a rate based congestion control where flows share the same bottleneck. The paper also gives a general solution for fairness-optimal initial rate in case of second-order fairness measures.

SUMMARY We consider a multi‐rate system where stream and elastic flows receive service. Both the stream and the elastic classes are associated with peak rate limitation. In contrast to the constant bit rate stream flows, the elastic flows tolerate bandwidth compression while in service. Because of the occasional bandwidth compression, the holding time of elastic flows depends on their perceived throughput. Although this model is Markovian under quite non‐restrictive assumptions, the model's state space grows exponentially with the number of traffic classes. The model is not quasi‐reversible, and therefore, it cannot be evaluated by efficient recursive formulae. We propose a method whereby the original state space is mapped to a two‐dimensional one, independently of the number of the stream and the elastic traffic classes. The special structure of the two‐dimensional model allows us to develop an efficient method that approximates the average throughputs of elastic flows. The state space reduction together with the proposed approximation provides a powerful tool for the performance analysis of this model as it allows the approximation of the average throughputs of elastic flows reasonably accurately in large models as well. Copyright © 2012 John Wiley & Sons, Ltd.

In the High-Speed Downlink Packet Access (HS-DPA) Iub Transport Network (TN) which connects the Radio Network Controller (RNC) with base stations (Node Bs), congestion control is needed. This paper reviews existing congestion control solutions and describes a novel, non-standardized, cross-layer, window-based HSDPA Transport Network Congestion Control which uses the standardized congestion detection and signalling framework. This solution is based on the idea of extending the Radio Link Control (RLC) protocol with congestion control functionality. This idea originates from the interesting duality between the TCP and the RLC protocols. TCP was originally designed for wired networks, therefore many extensions have been proposed to make TCP to be efficiently used over wireless networks. RLC was originally designed exclusively for handling radio link failures and no RLC extensions have been proposed to make RLC to be efficiently used over congested wired links. This paper proposes such an RLC extension where the RLC transmission window size is used to control the bitrate of the flow. Simulation analysis of this window-based solution is performed and it is shown that the proposed method is a possible solution for and efficient Iub Transport Network congestion control.

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