Florian Liers

Increasing spectrum capacity for ad hoc networks using cognitive radios: an analytical model

In this letter, an analytical model to evaluate the performance of ad hoc devices equipped with cognitive radio capabilities, is investigated. By applying cognitive radio technology, the ad hoc devices will utilize the unused spectrum of the existing legacy systems in an opportunistic manner in addition to using the unlicensed spectrum. Therefore, the network throughput will be increased. The results show that the performance is improved in terms of blocking and dropping probabilities.

UMTS data capacity improvements employing dynamic RRC timeouts

The management of radio and code resources of UMTS radio systems is a crucial issue in order to optimize the cell capacity, especially for packet-switched services. In UMTS the Radio Resource Control (RRC) protocol employs static timeouts to decide on the time when idle radio and code resources are released. Unfortunately, the optimal timeout values depend on many parameters, which are not necessarily under full control of the operator. Most important are the characteristics of packet traffic and the current system utilization. This paper presents detailed results for a new scheme based on the Simplex method initially introduced in Brosch and Mitschele-Thiel (2005). The scheme automatically adapts to the current situation. The scheme releases resources hold by inactive mobiles based on the demand and the current load situation instead of using static timeouts. In the paper we also propose an improvement of the initial Simplex method to minimize call setup delays. In addition we study the impact of the adaptive method on the signaling traffic. Simulation results show that the scheme allows for a reduction of the blocking and dropping rate by more than 31% without negative impacts on other parameters. Considering identical blocking and dropping rates, the system capacity can be improved by about 20%

Static RRC Timeouts for Various Traffic Scenarios

The operator of an UMTS radio access network has to define timeout thresholds for the radio resource control protocol. These timeouts have a strong influence on the quality of service of the user traffic. In general long timeouts favour the call setup time over the outage probability. For short timeouts it is the other way around. Furthermore the reached quality of service level depends on the load in the system. The load consists of the number of users in the system and the services they are using. This paper investigates the relationship between these both parameters and the previously mentioned quality of service parameters. We present results of five different timeout settings, tested in various network settings. Simulations show that very high timeout values have an insignificant influence on call setup time but increase the outage. We highlight two timeout settings which fits the requirements on user experience and operators expectations best.

Requirement driven prospects for realizing user-centric network orchestration

The Internet’s infrastructure shows severe limitations when an optimal end user experience for multimedia applications should be achieved in a resource-efficiently way. In order to realize truly user-centric networking, an information exchange between applications and networks is required. To this end, network-application interfaces need to be deployed that enable a better mediation of application data through the Internet. For smart multimedia applications and services, the application and the network should directly communicate with each other and exchange information in order to ensure an optimal Quality of Experience (QoE). In this article, we follow a use-case driven approach towards user-centric network orchestration. We derive user, application, and network requirements for three complementary use cases: HD live TV streaming, video-on-demand streaming and user authentication with high security and privacy demands, as typically required for payed multimedia services. We provide practical guidelines for achieving an optimal QoE efficiently in the context of these use cases. Based on these results, we demonstrate how to overcome one of the main limitations of today’s Internet by introducing the major steps required for user-centric network orchestration. Finally, we show conceptual prospects for realizing these steps by discussing a possible implementation with an inter-network architecture based on functional blocks.

Self-optimizing Mechanism for Prediction-Based Decentralized Routing

In this paper, we introduce an adaptive traffic prediction approach for self-optimizing the performance of a Prediction-based Decentralized Routing (PDR) algorithm. The PDR algorithm is based on the Ant Colony Optimization (ACO) meta-heuristics in order to compute the routes. In this approach, an ant uses a combination of the link state information and the predicted available bandwidth instead of the ant’s trip time to determine the amount of deposited pheromone. A Feed Forward Neural Network (FFNN) is used to build adaptive traffic predictors which capture the actual traffic behavior. Our contribution is a new self-optimizing mechanism which is able to locally adapt the prediction validity period depending on the prediction accuracy in order to efficiently predict the link traffic. We study three performance parameters: the rejection ratio, the percentage of accepted bandwidth and the effect of prediction use. In general, our new algorithm reduces the rejection ratio of requests, achieves higher throughput when compared to the AntNet and Trail Blazer algorithms.

Performance analysis of mobility management protocols using a generic mathematical model

An important challenge for All-IP wireless networks is the development of solutions for fast and seamless mobility. Many mobility management protocols have been developed to match real-time requirements in All-IP networks. In addition, lots of performance studies have been performed. In order to estimate the performance of a certain mobility management protocol compared to some others, a mathematical model for each protocol should be developed or each protocol should be simulated or implemented. In general, the simulation and the implementation take a long time and deliver detailed and accurate results. The mathematical model can be developed faster and results in a good estimation of the performance. Until now there is no generic mathematical model that can be used for a wide range of mobility management solutions. In this paper we propose a model that allows for the evaluation of the performance of a large set of mobility management protocols with respect to the handoff latency and the expected number of dropped packets. Our model takes the dropping of control messages, mobility patterns and network topology into account. The parameters of the generic model are set according to the characteristics of the studied protocols. Mobile IP Fast Authentication protocol (MIFA) and Handoff-Aware Wireless Access Internet Infrastructure (HAWAII) are compared to each other in this paper using the developed model.

Optimal placement of anchor points within large telecommunication networks

Classical micro-mobility solutions focus on accelerating local handovers and on minimizing signalling traffic. However, the micro-mobility components also slow down the service times in the user traffic domain. This is a critical drawback in terms of the hard delay requirements of future IP-based radio access networks. Network operators need algorithms to determine the optimal number and placement of anchor points within his network to balance both handover latency and user traffic delay. This paper presents a very fast and exact mathematical method for selecting the optimal number and placement of nodes supporting micro-mobility functionality for telecommunication networks. The method is in particular applicable for large networks, which is demonstrated by means of an optimization of a real wireless access network with more than 150 nodes. In order to ensure the applicability in real network scenarios we additionally provide a solution to estimate the stability of the optimal configuration. The presented method allows the autonomous and optimal configuration of the networks micro-mobility functionality as described in concepts of zero-touch networks. Due to the optimization network operators can reduce the administration cost and maximize the quality of service as well.

Limiting UMTS Dropping Rate with Control-Based CAC Algorithm

The resource consumption of mobile users within a UMTS communication system fluctuates over time due to their communication behavior and the link quality. Due to the limited resources of UMTS systems congestion may occur. The rising needs for resources may even force the system to drop active calls. In order to prevent such dropping events, permission requests for new calls may by rejected, if the system load is high or is expected to be high in the future. In this paper we present a control theory approach for adjusting the UMTS RRC call admission control threshold according to the current traffic situation in a UMTS cell. This algorithm prevents the dropping rate to exceed a predefined limit, as shown by our simulation results

Recursive layering of Forwarding on Gates and Traffic Engineering Middleware for Ethernet

Quality of Service (QoS) for inter-networks requires a two-tier approach to separate the end-to-end communication from the QoS provisioning within each autonomous system. However, the interaction between both is not standardized. Furthermore, the solutions for both tiers lack either scalability, flexibility, or QoS guarantees. Our paper presents a combination of “Forwarding on Gates” (FoG) as inter-network and “Traffic Engineering Middleware for Ethernet” (TEME) as intra-network techniques. This combination incorporating a recursive layer model separates the layers based on their scope and not on their functionality. This paper proposes a single interface used by all layers. Furthermore, the same interface is used by applications in order to signal their QoS requirements. This design allows supporting QoS in a more consistent way as compared to the ISO/OSI layer model. The paper outlines the proposal theoretically and demonstrates the advantages with an example.