There has been a lot of research focusing on optimizing the Long Term Evolution (LTE) networks performance. A large part of this research focused on how to optimize the LTE radio interface to efficiently distribute the scarce radio resources among the LTE users. Since LTE offers a diverse amount of services, the Quality of Service (QoS) differentiation is a major challenge. QoS is handled in LTE at different levels; the most important one is the radio scheduler. The QoS aware radio scheduler is designed to guarantee different service requirements. However, if the LTE radio interface is fully optimized towards QoS guarantees, what happen when the LTE transport network runs into congestion? Congestion can happen at any point in the network, and normally congested LTE backhaul tends to create large unfairness among the users, even among the ones with the same QoS class. The LTE transport congestion can occur at any router in the backhaul network. In this paper, we present two novel algorithms, which focus on the LTE transport congestion. The first algorithm is a congestion detection mechanism (CD) that identifies the transport network congestion as early as possible, and triggers the congestion control function. The second algorithm preserves and optimizes the QoS performance of each user over the transport to match the radio scheduler service differentiation, i.e., achieving fairness among the users in the same QoS demand and guaranteeing the enforced radio QoS weights for different service classes.

Switching systems based on the ATM principle have outgrown the experimental stage, and are already used today in private and corporate networks, as well as in public wide area networks to provide regular service. ATM has the inherent ability to provide a common basis for transmission and switching functionality in both local and wide area networks. With the potential to support all services available today as well as those envisaged for the future, ATM holds a strong promise for network operators and end customers. To fully exploit this potential, ATM switch architectures are required which provide versatility and modularity in supporting services and protocols, independent scalability of data throughput and control performance over a wide range, and also reliability features adaptable to the respective application scenario. This paper describes in some detail how the MainStreetXpress core services node, which has evolved from the prototype described by Fischer et. al. (1991) to a mature central office ATM switch, addresses these issues and provides a future-proof architecture incorporating all of the features required in the B-ISDN era.

A broadband ISDN switching network model is presented, switching the channel types H2, H3, and H4 envisaged by the CCITT. The synchronous time division multiplex technique is applied. The switching network operates at the basic bit rate of the H2-channel; H3and H4-connections are established via multichannel connections of up to four basic channels. H2-connections which are part of one H3- or H4-connection always have to use common interconnection links. This is a favorable solution to keep digit sequence integrity for multichannel connections, but influences blocking characteristics of the switching network. The implementation of an optimal path selection method plays a fundamental role. In such a multichannel switching network, blocking probabilities for H2-, H3-, and H4-connections must be distinguished. They do not only depend on the total offered load, but also on the proportions of H2-, H3-, and H4-connections (traffic mix). The simulation results presented in this paper prove that multirate switching via multichannel connections is feasible for the broadband channel types H2, H3, and H4, and that the proposed switching network has a sufficiently high traffic capacity whatever the traffic mix may be.