One of the critical issues of systems utilizing Orthogonal Frequency Division Multiplexing (OFDM) is the high peak to the average power ratio of OFDM signals. We have used Precoding as a way to mitigate the PAPR problem. Furthermore the performance of Precoded OFDM in fading multi-path channels has been studied. This thesis is based on an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a Precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this Precoding scheme is an attractive solution to the PAPR problem of OFDM signals.

Development of high average power lasers has historically been limited by the properties of available gain media. As a result it is either too costly or impractical to employ lasers in many applications for which they would otherwise be well suited. We have synthesized a new type of colloidal laser gain material that should possess many of the advantages of solid state media without their primary disadvantage: poor thermal performance. The colloid consisted of an emulsion of 20% Nd+3 doped phosphate glass nanoparticles suspended in nonanoic acid. The spectroscopic properties of the material were found to be consistent with those of bulk Nd+3 doped materials and suitable for laser development. / text

Syftet med denna studie var att undersöka om vistelse på hög höjd påverkar den anaeroba arbetsförmågan. Sex aktiva universitetsstudenter, fyra män och två kvinnor, deltog frivilligt i studien. Expeditionen till Nepal varade i 40 dagar och under den perioden sov och vandrade försökspersonerna mellan 1400 och 5100 meter över havet. Före och efter expeditionen genomförde försökspersonerna ett anaerobt wingatetest där peak power, average power, minimum power and power drop uppmättes. Resultatet visade en signifikant sänkning av average power efter den genomförda expeditionen på hög höjd, med ett medelvärde på 8.44 ± 0,84 w/kg före expeditionen och 7.81 ± 0,87 w/kg efter expeditionen. Inga signifikanta förändringar sågs hos övriga uppmätta parametrar. Konklusionen är att average power försämras efter 40 dagars vistelse på hög höjd.

In the past decade, there has been great motivation to improve the efficiency of power amplifiers (PAs) in handset transmitter systems in order to address critical issues such as poor battery life and excessive heat. Currently, the focus lies on high data rate applications such as wideband code division multiple access (WCDMA) and long term evolution (LTE) standards due to the stringent efficiency and linearity requirements on the PA. This thesis describes a simulation-based study of techniques for enhancing the efficiency of a CMOS power amplifier for WCDMA and LTE applications. The primary goal is to study the concepts of envelope and average power tracking in simulation and to demonstrate the effectiveness of these supply modulation techniques on a CMOS PA design. The P1dB and IMD performance of a Class A/AB CMOS PA has been optimized to operate with high peak-to-average modulation with WCDMA and LTE signals. Behavioral models of envelope and average power tracking are implemented using proposed algorithms, and a system-level analysis is performed. Envelope tracking is seen to offer a peak PAE improvement of 15% for WCDMA, versus a fixed voltage supply, while average power tracking renders a maximum efficiency gain of 9.8%. Better than -33dBc adjacent channel leakage-power ratio (ACLR) at 5MHz offset and EVM below 4% are observed for both supply tracking techniques. For LTE, envelope and average power tracking contribute to a peak PAE enhancement of 15.3% and 7%, respectively. LTE ACLR begins failing the -30dBc specification above 22.5dBm output power during envelope tracking operation in the PA implementation described here. / text

The main objective of the thesis is to implement different architectures of 16-bit adders such as; Ripple CarryAdder (RCA), Manchester Carry Chain Adder (MCCA) and Kogge Stone Adder (KSA), in 65nm CMOS technology and to study their performance in terms of power, operating frequency and speed at near threshold operating regions. The performance of these adders are evaluated and compared with each other and a final conclusion is made as to which adder structure is more suitable for implementation in a 65nmtechnology for low power applications. Several optimisation techniques are performed for the adders to reduce the delay and power consumption. Propagation delay is the most critical or essential parameter to be considered, hence, to minimise the delay of the adder, a technique called sizing and ordering are required for the transistors. The purpose of the thesis is to make a fair comparison among adders over several metrics which include linearity, delay and power. Simulation results of MCCA achieved a greater significant performance upon or over RCA and KSA, and proved it is the best suitable adder for low power applications.

En mars 1947, le gouvernement australien dirigé par Joseph Chifley présente devant le Parlement une liste des priorités en matière de politique étrangère et de sécurité pour le Commonwealth d’Australie : « en premier, un soutien plein et entier aux Nations Unies, en second le maintien des liens avec le Commonwealth, en troisième les accords de sécurité avec les Etats-Unis et d’autres Etats [et] en quatrième la participation à la politique régionale ». En 1994, selon le Livre Blanc de la Défense, la politique étrangère de l’Australie a considérablement évolué. Elle repose désormais en priorité sur l’Asie Pacifique : « la sécurité future de l’Australie – comme [sa] prospérité économique – est liée inextricablement à la sécurité et à la prospérité de l’Asie Pacifique ». / N March 1947 the Australian government led by Joseph Chifley present to Parliament a list of priorities in foreign policy and security for the Commonwealth of Australia: "First, a full support to the United Nations, in the second maintaining links with the Commonwealth, in the third security agreements with the United States and other countries [and] in the fourth participation in regional policy. "In 1994, the White Book of Defence, the Australian foreign policy has evolved considerably. She is now based primarily on the Asia Pacific, "the future security of Australia - as [its] economic prosperity - is inextricably linked to security and prosperity of Asia Pacific."

High peak to average power ratio (PAPR) is one of the major drawbacks in orthogonal frequency division multiplexing (OFDM) systems. In recently years, various methods have been proposed to reduce the PAPR performance. The selected mapping (SLM) scheme is perhaps the most popular one because it provides outstanding PAPR reduction performance. In addition, the subcarrier magnitude remains the same in the SLM scheme. However, there are two major shortcomings in the SLM scheme. First of all, it requires a number of inverse fast Fourier transforms (IFFTs) to produce candidate signals, dramatically increasing the computational complexity. In addition, side information has to be transmitted to the receiver to indicate the candidate signal that results in the best PAPR, leading to the decrease in bandwidth utilization. To overcome these two drawbacks, this thesis proposes a novel SLM scheme that does not need side information. The proposed scheme is based on a low complexity SLM scheme [C.-P. Li, S.-H. Wang, and C.-L. Wang, ¡§Novel low-complexity SLM schemes for PAPR reduction in OFDM systems,¡¨ IEEE Trans. Signal Process., vol. 58, no. 5, pp. 2916¡V2921, May 2010] in pilot-aided OFDM system. Simulation experiments are conducted to verify the performance of the proposed scheme. It is shown that the bit error rate (BER) performance of the proposed scheme is very similar to that of the traditional SLM scheme with perfect knowledge of the side information. Therefore, the proposed scheme not only has the advantages of low complexity and high bandwidth utilization, but also has a superior BER performance.

High peak-to-average power ratio (PAPR) is a serious drawback in orthogonal frequency division multiplexing (OFDM) systems. Various methods have been proposed to reduce PAPR, active constellation extension (ACE) scheme has excellent performance. There are two schemes were proposed in traditional ACE, the one of which is ACE-Smart Gradient-Project (SGP) which can significantly reduce PAPR through first iteration. In fact, optimal solution is not obtained in ACE-SGP, we find the scheme can be formulated as convex optimization problem, that is, we can find out optimal solution to minimize PAPR by convex optimization algorithm. Two proposed schemes are based on two low complexity schemes, respectively, and they were proved to satisfy convex optimization problem. Although the power of transmission and complexity of optimization algorithm in the proposed schemes are higher than that of the traditional ACE-SGP scheme, but proposed schemes has proper improvement in PAPR reduction.

In recent years, the development of OFDM system has received a lot of attention. Some examples of existing systems where OFDM system is used are digital audio broadcasting, high-definition television terrestrial broadcasting, asymmetric digital subcarrier lines and so on. There are several reasons for using OFDM systems. First, OFDM system is an efficient way to deal with multipath effect. Under a fixed amount of delay spread, the implementation complexity of OFDM system is much less than that of single-carrier system. The reason is that OFDM system can simply use guard time to process delay spread without a complex equalizer. Second, OFDM system can achieve high data rate to transmit by using large number of subcarriers. Third, OFDM system can also efficiently combat with narrow band interference. On the other hand, OFDM system also has two main drawbacks. One is more sensitive to frequency offset, the other is higher PAPR. This thesis focuses on the PAPR problem. Pulse shaping method is an effective way to solve this problem. It can be used for any number of subcarriers of OFDM systems, so it is very flexible. It doesn¡¦t have any additional IFFTs in comparison to the selected mapping or partial transmit sequence method. Its implementation is simpler. And because it also doesn¡¦t distort the OFDM symbols, its bit error performance should be better than the clipping method. According to the pulse shaping method, we get a better waveform that can make the PAPR of OFDM symbols do not exceed about 2.

Selected mapping (SLM) schemes are commonly employed to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It has been shown that the computational complexity of the traditional SLM scheme can be substantially reduced by adopting conversion vectors obtained by using the inverse fast Fourier transform (IFFT) of the phase rotation vector in place of the conventional IFFT operations [21]. Unfortunately, however, the elements of these phase rotation vectors of the conversion vectors in [21] do not generally have an equal magnitude, and thus a significant degradation in the bit error rate (BER) performance is incurred. This problem can be remedied by utilizing conversion vectors having the form of a perfect sequence. This paper presents three novel classes of perfect sequence, each of which comprises certain base vectors and their cyclic-shifted versions. Three novel low-complexity SLM schemes are then proposed based upon the unique structures of these perfect sequences. It is shown that while the PAPR performances of the proposed schemes are marginally poorer than that of the traditional SLM scheme, the three schemes achieve an identical BER performance and have a substantially lower computational complexity.