Lars Dittmann

Cloud RAN for Mobile Networks—A Technology Overview

Cloud Radio Access Network (C-RAN) is a novel mobile network architecture which can address a number of challenges the operators face while trying to support growing end-users needs. The main idea behind C-RAN is to pool the Baseband Units (BBUs) from multiple base stations into centralized BBU Pool for statistical multiplexing gain, while shifting the burden to the high-speed wireline transmission of In-phase and Quadrature (IQ) data. C-RAN enables energy efficient network operation and possible cost savings on baseband resources. Furthermore, it improves network capacity by performing load balancing and cooperative processing of signals originating from several base stations. This paper surveys the state-of-the-art literature on C-RAN. It can serve as a starting point for anyone willing to understand C-RAN architecture and advance the research on C-RAN.

Flow enforcement algorithms for ATM networks

Four measurement algorithms for flow enforcement in asynchronous transfer mode (ATM) networks are presented. The algorithms are the leaky bucket, the rectangular sliding window, the triangular sliding window, and the exponentially weighted moving average. A comparison, based partly on teletraffic theory and partly on signal processing theory, is carried out. It is seen that the time constant involved increases with the increasing burstiness of the connection. It is suggested that the RMS measurement bandwidth be used to dimension linear algorithms for equal flow enforcement characteristics. Implementations are proposed on the block diagram level, and dimensioning examples are carried out when flow enforcing a renewal-type connection using the four algorithms. The corresponding hardware demands are estimated aid compared. >

Statistical multiplexing of identical bursty sources in an ATM network

The authors study the performance of a statistical multiplexer with a common buffer and bursty sources. A uniform arrival and service model has been used to calculate the loss probability as a function of several parameters. It is shown that the ratio of the number of cells in an average burst to buffer capacity per source is a more important parameter than burstiness. When this ratio is much greater than one, performance will be poor unless the load is very low. If the ratio is of the order of one or less, acceptable performance can be achieved. It is shown that combining small load with with multiplexing of many sources can be a very efficient way to lower cell loss probability.<<ETX>>

Load control in atm networks

This paper considers preventive load control in ATM networks. A one link performance evaluation based on on/off traffic sources is carried out. Approximative models are derived, and a specific admission control algorithm based on one of the models is presented and the obtained transfer efficiency is derived. A Flow Enforcement function to supervise each connection is suggested and the correspondence between modelling parameters, flow enforcement parameters and parameters used by the admission control algorithm is considered.

String mode-a new concept for performance improvement of ATM networks

A multilink concept, called string mode, that can be used in an asynchronous transfer mode (ATM) network to balance the load and thereby increase the efficiency of the network is introduced. The principle of the concept is to chop bursts into smaller subbursts, called strings, and distribute them onto a number of parallel links. Performance evaluation shows an efficiency improvement of more than 50% when the concept is used with bursty sources with a relatively high peak bit rate. The traffic shaping property and balancing of the load obtained in using the string mode protocol allow a simpler load control mechanism. The dissociation between service bit rate and link bit rate makes it possible to provide a high-bit-rate service using less advanced technology, and it will lower the blocking probability, as the total bandwidth does not have to be found on the same link. >

Green-aware routing in GMPLS networks

The increasing amount of traffic in the Internet has been accommodated by the exponential growth of bandwidth provided by the optical networks technologies. However, such a growth has been also accompanied by an increase in the energy consumption and the concomitant green house gases (GHG) emissions. Despite the efforts for improving energy efficiency in silicon technologies and network designs, the large energy consumption still poses challenges for the future development of Internet. In this paper, we propose an extension of the Open Shortest Path First - Traffic Engineering (OSPF-TE) protocol and a green-aware routing and wavelength assignment (RWA) algorithm for minimizing the GHG emissions by routing connection requests through green network elements (NE). The network behavior and the performance of the algorithm are analyzed through simulations under different scenarios, and results show that it is possible to reduce GHGs emissions at the expense of an increase in the path length, and, in some cases, in the blocking probability. The trade-off between emissions and performance is studied. To the authors knowledge, this is the first work that provides a detailed study of a green-aware OSPF protocol.

OWL Ontologies and SWRL Rules Applied to Energy Management

Energy consumption has increased considerably in the last years. How to reduce and make energy consumption more efficient in home environments has become of great interest for researchers. This could be achieved by introducing a Home Energy Management System (HEMS) into user residences. This system might allow the user to control the devices in the home network through an interface and apply energy management strategies to reduce and optimize their consumption. Furthermore, the number of devices and appliances found in users residences is increasing and these devices are usually manufactured by different producers and can use different communication technologies. This paper tackles this problem. A home gateway which integrates different devices with a HEMS based on set of semantic-web tools providing a common control interface and energy management strategies.

OSPF-TE extensions for green routing in optical networks

This paper proposes extensions to the OSPF-TE protocol to enable green routing in GMPLS-controlled optical networks. Simulation results show a remarkable reduction in CO2 emissions by preferring network elements powered by green energy sources in the connection routing.

Energy-aware routing optimization in dynamic GMPLS controlled optical networks

In this paper, routing optimizations based on energy sources are proposed in dynamic GMPLS controlled optical networks. The influences of re-routing and load balancing factors on the algorithm are evaluated, with a focus on different re-routing thresholds. Results from dynamic network simulations show that re-routing strategies can lower CO2 emissions compared to the basic energy source routing scheme, and a lower re-routing threshold achieves more savings. The increased blocking probability brought by using re-routing schemes can be compensated by applying load balancing criteria. A trade-off between blocking probability and obtained CO2 savings is studied.

Downlink resource management for QoS scheduling in IEEE 802.16 WiMAX networks

IEEE 802.16, also known as WiMAX, has received much attention recently for its capability to support multiple types of applications with diverse Quality-of-Service (QoS) requirements. Beyond what the standard has defined, radio resource management (RRM) still remains an open issue, which plays an important role in QoS provisioning for different types of services. In this paper, we propose a downlink resource management framework for QoS scheduling in OFDMA based WiMAX systems. Our framework consists of a dynamic resource allocation (DRA) module and a connection admission control (CAC) module. A two-level hierarchical scheduler is developed for the DRA module, which can provide more organized service differentiation among different service classes, and a measurement-based connection admission control strategy is introduced for the CAC module. Through system-level simulation, it is shown that the proposed framework can work adaptively and efficiently to improve the system performance in terms of high spectral efficiency and low outage probability.