The coloring of disk graphs is motivated by the frequency assignment problem. In 1998, Malesinska et al. introduced double disk graphs as their generalization. They showed that the chromatic number of a double disk graph G is at most 33 D(G) - 35, where D(G) denotes the size of a maximum clique in G. Du et al. improved the upper bound to 31 D(G)-1. In this paper we decrease the bound substantially; namely we show that the chromatic number of G is at most 15 D(G) - 14.
COBISS.SI-ID: 2048330259
The assurance of quality of experience (QoE) and provisioning of high throughput of the system represent the main goals of future wireless and mobile networks. This paper presents novel and practical cross-layer QoE-aware radio resource allocation (RRA) algorithms for the downlink of a heterogeneous orthogonal frequency division multiple access (OFDMA) system. The objective of the proposed algorithms is to assure the appropriate level of QoE for each user of the system by incorporating application-layer parameters and subjective human perception of quality into the RRA process. We propose two user-oriented joint subcarrier and power allocation algorithms with low complexity for real-time and interactive services. The first algorithm dynamically allocates resources by assuring the same level of QoE to all users of the system, whereas the second algorithm introduces the efficient trade-off between the user’s QoE and the spectral efficiency of the system. By considering application-layer parameters and user’s perception of quality, high users’ QoE and explicit control of data rates can be achieved. The numerical results show that the proposed algorithms achieve significant increase in the level of QoE compared to previous works, a fair distribution of capacity among users and near to optimal solution of QoE for the OFDMA system.
COBISS.SI-ID: 10775636
The notion of user perception has grown in terms of its importance and complexity. This paper presents results of an experimental study focused on predictive modeling of the relations between the user perception, user satisfaction and objective technical parameters in data communication services. A new model for prediction of user satisfaction was devised using probability theory based on Markov chain. Two experiments were completed for web browsing scenarios. The results of the first experiment have confirmed that previous user experience has significant effect on the user perception of quality and should represent a vital element of future predictive user models. The result of the second experiment is a user satisfaction prediction model, which presents a novel insight and deeper understanding of user perception of quality. This model can significantly improve level of user satisfaction with services in telecommunications systems if implemented within advanced system design, optimization and quality assurance procedures.
COBISS.SI-ID: 10322772