Orthogonal Frequency Division Multiplexing Based Air Interfaces and Multiple Input Multiple Output Techniques in Cooperative Satellite Communications for 4th Generation Mobile Systems

Recently, wireless network technology has grown at such a pace that scientific research has become a practical reality in a very short time span. One mobile system that features high data rates and open network architecture is 4G. Currently, the research community and industry, in the field of wireless networks, are working on possible choices for solutions in the 4G system. The researcher considers one of the most important characteristics of future 4G mobile systems the ability to guarantee reliable communications at high data rates, in addition to high efficiency in the spectrum usage. On mobile wireless communication networks, one important factor is the coverage of large geographical areas. In 4G systems, a hybrid satellite/terrestrial network is crucial to providing users with coverage wherever needed. Subscribers thus require a reliable satellite link to access their services when they are in remote locations where a terrestrial infrastructure is unavailable. The results show that good modulation and access technique are also required in order to transmit high data rates over satellite links to mobile users. The dissertation proposes the use of OFDM (Orthogonal Frequency Multiple Access) for the satellite link by increasing the time diversity. This technique will allow for an increase of the data rate, as primarily required by multimedia applications, and will also optimally use the available bandwidth. In addition, this dissertation approaches the use of Cooperative Satellite Communications for hybrid satellite/terrestrial networks. By using this technique, the satellite coverage can be extended to areas where there is no direct link to the satellite. The issue of Cooperative Satellite Communications is solved through a new algorithm that forwards the received data from the fixed node to the mobile node. This algorithm is very efficient because it does not allow unnecessary transmissions and is based on signal to noise ratio (SNR) measures.

The sexual division of labor : the impact of organizational change upon group cohesion and the creation of occupational identity

The purpose of this research is to identify the impact of recent organizational change upon the culture of firefighting. The experiences of female firefighters were utilized as a measure of cultural change. A purposive sample of twenty-seven male and female firefighters were interviewed in a semi-structured format about their experiences in the fire service. This research found that the culture of firefighting has adjusted to the presence of previously excluded groups by forging a division among the identities and roles of male and female firefighters. The white, male firefighters, who have traditionally constituted a majority of the workforce, have continued to identify with traditional firefighter roles and reported high levels of cohesion. In contrast, the female firefighters showed a greater variance in their identification with traditional roles and decreased levels of cohesion with the main body of the group.