Ad hoc networks are becoming an interesting research area, as they inher-ently support unique network applications for the wireless communications in a rug-ged environment, which requires rapid deployment and is difficult to be provided by an infrastructure network. Many issues need to be addressed for the ad hoc networks. In this dissertation, we propose an efficient distributed coordination function, a dynamic rate adaptation and fragmentation scheme, and a simultaneous frame transmission scheme on the media access control protocol to enhance the power conservation of mobile hosts and to im-prove the network throughput of an ad hoc network. Extensive simulations are studied to evaluate the improvement of the proposed schemes. The results of the simulations exhibit significant improvement to the stan-dard access control protocol. Not only the improvement of the throughput of the ad hoc networks, but also the conservation of the battery power of the mobile hosts were achieved with our schemes.

Background: The concept of value perception is widely discussed in scientific literature and it is well-known, that channels deliver value to the customer. However, so far there has been no research about the efficiency of channels, especially the consumer´s perception of channel efficiency. Therefore, this study contributes to the current literature in channel management and it fills an existing research gap. The authors establish a definition of the term 'channel efficiency' and they develop a measuring instrument. For this thesis, the three criteria (1) shopping enjoyment, (2) interpersonal service quality and (3) price level are taken into consideration for the efficiency calculation. The two channels of interest are physical retail stores and the Internet. The target group is university students. Purpose: To measure and compare the efficiency of the channels 'physical retail store' and 'Internet' from the consumer´s view and thus, to find general patterns of rated channel efficiency. This will be achieved by investigating the individual channel value perception of certain channel specific criteria and by exploring the respective relevance of these criteria.   Research Questions: 1. What is the general channel efficiency of the channel physical retail store? 2. What is the general channel efficiency of the channel Internet? Method: A quantitative study in form of an online questionnaire has been conducted with German and Swedish students. 1 995 persons participated in the survey. The analysis has been carried out by using the computer software SPSS. Thus, the collected data could be edited with respect to the verification of the proposed hypotheses, the calculation and comparison of the respective channel efficiencies and additionally, the identification of patterns for gender and age groups. Research findings: The analysis of the collected data has shown that the three regarded criteria are of diverse importance and they are perceived differently for the channels physical retail stores and the Internet. Hence, the efficiency of those two channels is also unequal; physical retail stores reach a mean value of 46.8% and the Internet in turn achieves an average of 43.1%. This shows that both channels hold potential for improvement. When looking at patterns between gender and age groups, the authors could also identify interesting differentiations.