18 research outputs found
Adaptive iterative multiuser detection for wireless communication systems
No full textWireless multi-user communication systems that operate in a low signal to interference noise ratio (SINR) region are studied in this thesis.
This thesis examines a class of wireless communication systems that employs an adaptive receiver for multi-user symbol detection that operates in a low SINR (< 5 dB) region. Since the knowledge of channel-parameter estimates is unavailable at the receiver, a pilot (training) sequence is applied in the communication system, to learn the channel state information (CSI) at the receiver.
In studying the classical view of a DFE, the mean square error (MSE) behaviour follows the bit error rate (BER) performance. Certain original results are obtained using the classical adaptive DFE to achieve minimum MSE, employing the least mean square (LMS) algorithm. The results thus obtained for an uncoded adaptive receiver system are applied to a coded system, transmitting either recursive systematic code (RSC) or turbo-code through a spread-spectrum multiuser multiple-path channel, which are referred to as two-stage and three-stage systems respectively in this thesis.
The following claims are made based on the findings of this thesis:
1. It is known that a receiver implementing DFE can mitigate symbol-interference completely at high SINR. An adaptive LMS DFE realizes this by adapting the forward and backward filter coefficients with respective step-size constants. The classical approach to realizing interference mitigation was to set the forward and backward adaptation constants as the same. While this approach has provided interference mitigation at high SINR, it has been shown in this thesis that such an approach does not yield complete interference mitigation, even at high SINR. Instead, using different step-size constants at the backward and forward step-size constants provides the required optimality.
2. A decision feedback detector (DFD) mitigates the effects of interference on the information symbols that are transmitted through this communication channel. This thesis shows that an adaptive (LMS) DFD, using unequal compared to equal step-size constants to update the forward and backward filter coefficients, has a steady-state MSE improvement for an uncoded frequency selective communication channel.
This thesis shows that, when the knowledge of CSI is not assumed to be known at a wireless receiver, a three-stage receiver has a BER performance improvement and operates at a lower SINR, without any additional computational complexity compared to a two-stage receiver
Adaptive Multiuser Turbo Asynchronous Receiver for Oversaturated MIMO Communication System
No full text
Adaptive ‘imperfect’ decision feedback equalizer for a frequency selective communication channel
No full textIn this paper, we show that, for an uncoded receiver system, the proposed least mean square (LMS) decision aided equalizer (DAE), with, the backward step-size constant greater than forward step-size constant, compared to classical equal-step size design, has a lower mean square error by upto 5 dB, for a frequency selective wireless communication channel. Classical LMS DAE with equal step-size constants, can be considered as perfect decision feedback system, compared to, the proposed unequal step-size, as a imperfect decision feedback system. We provide, Wiener DAE, considering imperfect decision feedback information, during training mode and provide analysis for LMS DAE with unequal step size constants
Combining signals by weighted least square error method for wireless communication networks
No full textIn this paper we presented weighted least square error method for signal combining for wireless communication in presence of unequal channels noise variance. The method has been commonly used for target tracking and in econometrics. System presented for signal combining by weighted least square error is a receiver with filters at each received branch for the error estimation (noise). The inverse of estimate of channels noise variance used as weights for signal combining to achieve wiener’s solution. The presented scheme of signal combining is particularly useful when wireless communication subject to unequal noise variance which is very common in present wireless communication systems. The performance of our scheme is shown by computer simulation in Gaussian, Rayleigh flat fading and frequrency selective wireless communication channel. The computer simulation performance of the system is about 10−3 bits at 8 dB SNR and about 10−4 at 16 dB SNR in wireless flat fading Raleigh channel with two receive antennas
The shortage of seafarers : developing industry/employer of choice and employment brand strategies
No full textThe New Economy is one of information, speed and extraordinary growth. This rate of growth in global economy is proportional to the demand for shipping; subsequently this growth in shipping will far exceed the current seafaring labor force. Soon the issue of seafaring shortage will be a global issue. Corrective measures must be administered now in order to meet the labor demands of the future. The reader will initially be given a brief update on the current seafaring labor market based on BIMCO/ISF 2005 report. Subsequently the author explores marketing strategies such as Employer of Choice to be a possible cure for this shortage. Simply put Employer of Choice is an organization that is able to meet the growth and profitability goals because it attracts and retains quality and quantity of it employees it needs
The aim of this study is to analyze how seafaring is marketed and campaigned in Singapore. After which the author explores into themes such as Employer of choice and branding strategies which have being proven to attract and retain talent in other industries. Based on the quantitative and qualitative studies conducted within the Singapore seafaring sector, the author believes there is a growth potential for the Singapore Seafaring Sector. With the right mix of marketing and human resource management strategies in place and greater synergy between Government, Employer and Union this study will inform readers on possible solutions to rectify the shortcomings of the future Seafarers.Bachelor of Science (Maritime Studies
-expansions
No full textIn this short note we partially answer a question of Fukaya and Kato by constructing a q-expansion with coefficients in a non-commutative Iwasawa algebra whose constant term is a non-commutative p-adic zeta function. The author is supported by EPSRC First Grant EP/L021986/
Foreign direct investment in a macroeconomic framework : finance, efficiency, incentives, and distortions
No full textDoes foreign direct investment (FDI) increase domestic investment, or does it provide additional foreign exchange for a pre-existing current account deficit, or some linear combination of the two? The author investigates this question for a group of five Pacific Basin countries and a control group of 11 other developing countries. For the sample of all 16 developing countries, the author finds that FDI does not provide additional balance of payments financing for a pre-existing current account deficit. In the control group of 11 developing countries, FDI is associated with reduced domestic investment - implying that FDI to those countries is simply a close substitute for other capital inflows. For the five Pacific Basin market economies, however, FDI raises domestic investment by the full extent of the FDI inflow. The author finds that FDI has a significantly negative impact on national saving in the sample of all 16 developing countries. For the control group, this negative effect is similar in magnitude to FDI's negative effect on domestic investment - implying a zero effect on the current account. But FDI's negative effect on national saving in the five Pacific Basin developing market economies implies that FDI could have more of a negative effect on the current account than through increased domestic investment alone. The author also investigates the impact of FDI on economic growth in these 16 countries, taking into account distortions in the economies. He estimates reduced-form current account equations, and presents an analytical framework for estimating FDI's effect on economic growth in the presence of incentive-disincentive packages and other economic distortions. He illustrates his framework using indicators of foreign trade and financial distortions. His main conclusion: the effect of FDI differs markedly from one group of countries to another. FDI has a negative effect on economic growth in the control group. It has the same positive effect on growth as domestically financed investment does in the Pacific Basin countries. The main cause for the different effect is the low level of distortion in the Pacific Basin countries.Environmental Economics&Policies,Economic Theory&Research,Foreign Direct Investment,International Terrorism&Counterterrorism,Macroeconomic Management
Higher moments of the pair correlation function for Sato-Tate sequences
No full textIn \cite{BS}, Balasubramanyam and the second named author derived the first
moment of the pair correlation function for Hecke angles lying in small
subintervals of upon averaging over large families of Hecke newforms of
weight with respect to . The goal of this article is to study
higher moments of this pair correlation function. For an integer , we
present bounds for its -th power moments. We apply these bounds to record
lower order error terms in the computation of the second and third moments. As
a result, one can obtain the convergence of the second and third moments of
this pair correlation function for suitably small intervals, and under
appropriate growth conditions for the size of the families of Hecke newforms.Comment: This is a significantly revised version incorporating a study of the
-th power moments of the above-mentioned pair correlation function for all
integers . The previous version only discussed the second moment.
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