Traditional cellular networks provide a centralized wireless networking paradigm within the wireless domain with the help of fixed infrastructure nodes such as Base Stations (BSs). On the other hand, Ad hoc wireless networks provide a fully distributed wireless networking scheme with no dependency on fixed infrastructure nodes. Recent studies show that the use of multihop wireless relaying in the presence of infrastructure based nodes improves system capacity of wireless networks. In this paper, we consider three recent wireless network architectures that combine the multihop relaying with infrastructure support -namely Integrated Cellular and Ad hoc Relaying (iCAR) system, Hybrid Wireless Network (HWN) architecture, and Multihop Cellular Networks (MCNs), for a detailed qualitative and quantitative performance evaluation. MCNs use multihop relaying by the Mobile Stations (MSs) controlled by the BS. iCAR uses fixed Ad hoc Relay Stations (ARSs) placed at the boundaries to relay excess traffic from a hot cell to cooler neighbor cells. HWN dynamically switches its mode of operation between a centralized Cellular mode and a distributed Ad hoc mode based on the throughput achieved. An interesting observation derived from these studies is that, none of these architectures is superior to the rest, rather each one performs better in certain conditions. MCN is found to be performing better than the other two architectures in terms of throughput, under normal traffic conditions. At very high node densities, the variable power control employed in HWN architecture is found to be having a superior impact on the throughput. The mobility of relay stations significantly influences the call dropping probability and control overhead of the system and hence at high mobility iCAR which uses fixed ARSs is found to be performing better.

In this paper we analyzed possible capacity gains in transition from DVB-T to DVB-T2 standard. We compared minimum C/N ratio needed for quasi error free reception of DVB-T and DVB-T2 systems with similar transmitting parameters currently used in Croatia. C/N was calculated using simulations developed in Matlab for those standards, in three commonly used channel models: Gaussian, Ricean and Rayleigh. Results show bandwidth increase of about 63% without significant increase of the minimum C/N. By using newer compression techniques and statistical multiplexing in large pools, it can be concluded that up to 10 times more TV channels (with the same quality) can be transmitted in the same occupied frequency bandwidth.

No abstract

In this article we define a new technology acceptance research model which considers the comparison of two technology solutions that an individual can use. The model estimates the usage of the observed solution based on the cost of switching from the reference solution (typically a standard or older solution) to the observed solution, considering the fact that the cost of switching is caused by a difference of facilitating conditions, habit and the intention to use between the reference and observed solutions. For evaluation purposes, we observed the costs of switching from teletext use to the use of the electronic programme guide (EPG on the subset of n = 82 respondents and interpreted 77.2% of the variance, which demonstrates the high quality of the model. Evaluation results indicate that the primary obstacle to switching from teletext to EPG usage arises from the individuals’ perception whether they have more or less of the necessary resources to use the EPG in comparison to the resources they have at their disposition in case of teletext use, and the second ranked switching cost is caused by a difference in habit.