60 research outputs found
Soft handover issues in radio resource management for 3G WCDMA networks
PhDMobile terminals allow users to access services while on the move. This unique
feature has driven the rapid growth in the mobile network industry, changing it from a
new technology into a massive industry within less than two decades.
Handover is the essential functionality for dealing with the mobility of the mobile
users. Compared with the conventional hard handover employed in the GSM mobile
networks, the soft handover used in IS-95 and being proposed for 3G has better
performance on both link and system level.
Previous work on soft handover has led to several algorithms being proposed and
extensive research has been conducted on the performance analysis and parameters
optimisation of these algorithms. Most of the previous analysis focused on the uplink
direction. However, in future mobile networks, the downlink is more likely to be the
bottleneck of the system capacity because of the asymmetric nature of new services,
such as Internet traffic.
In this thesis, an in-depth study of the soft handover effects on the downlink
direction of WCDMA networks is carried out, leading to a new method of optimising
soft handover for maximising the downlink capacity and a new power control
approach
INTERFERENCE MANAGEMENT IN LTE SYSTEM AND BEYOUND
The key challenges to high throughput in cellular wireless communication system are interference, mobility and bandwidth limitation. Mobility has never been a problem until recently, bandwidth has been constantly improved upon through the evolutions in cellular wireless communication system but interference has been a constant limitation to any improvement that may have resulted from such evolution. The fundamental challenge to a system designer or a researcher is how to achieve high data rate in motion (high speed) in a cellular system that is intrinsically interference-limited.
Multi-antenna is the solution to data on the move and the capacity of multi-antenna system has been demonstrated to increase proportionally with increase in the number of antennas at both transmitter and receiver for point-to-point communications and multi-user environment. However, the capacity gain in both uplink and downlink is limited in a multi-user environment like cellular system by interference, the number of antennas at the base station, complexity and space constraint particularly for a mobile terminal.
This challenge in the downlink provided the motivation to investigate successive interference cancellation (SIC) as an interference management tool LTE system and beyond. The Simulation revealed that ordered successive interference (OSIC) out performs non-ordered successive interference cancellation (NSIC) and the additional complexity is justified based on the associated gain in BER performance of OSIC. The major drawback of OSIC is that it is not efficient in network environment employing power control or power allocation. Additional interference management techniques will be required to fully manage the interference.fi=OpinnÀytetyö kokotekstinÀ PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=LÀrdomsprov tillgÀngligt som fulltext i PDF-format
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility
Modelação comportamental da camada fĂsica de NB-IoT em downlink
Mestrado em Engenharia Eletrónica e TelecomunicaçÔesThe Internet of Things (IoT) paradigm de nes a fully connected network of
devices enabling new forms of interaction between users and devices. The
constant growth of these networks, as well as an increasing demand for
more reliable, low bit rate and massive communication data
ows lead to
the emergence of new technologies and set of standards, such as, the Low
Power Wide Area Networks (LPWAN).
In June 2016, 3GPP, the consortium responsible for LTE development and
standardization, released a new licensed band based standard, named Narrow
Band (NB) IoT. NB-IoT was designed based on the same principles
of other LPWAN standards, providing better coverage and additionally an
easier integration on existing cellular systems.
In this dissertation a study on the NB-IoT Physical Layer is presented along
with an open source behavioral implementation in MATLAB of the downlink
transmission and reception chains.
The system generates and recovers one radio frame successfully performings
procedures such as MIB and SIB1-N extracting along with scheduling
and recovering data scheduled through control channels by higher layer
paramenters. The project models and executes the downlink transmission
(eNodeB) and reception (terminal) PHYs either in a pure simulation environment
using di erent channel models, as well as integrated with an USRP
software de ned radio device for co-simulation.
The simulation and co-simulation results are presented evaluating the transmission's
quality and performance of the implemented Zero Forcing equalizer.O paradigma da Internet of Things (IoT) define uma rede interligada de
dispositivos que permite o surgimento de novas formas de interacção entre
utilizadores e dispositivos. O constante crescimento destas redes assim
como a crescente demanda por uma fiabilidade maior, bit rates mais baixos
e circulação massiva de informação insurgiu o aparecimento de novas tecnologias
tais como as Low Power Wide Area Networks (LPWAN).
Em Junho de 2016 a 3GPP, o órgão responsåvel pelo LTE, lançou um novo
standard para bandas licenciadas o Narrowband (NB) -IoT. O NB-IoT foi
desenhado com base nos mesmos princĂpios que as outras LPWAN com o
acréscimo de uma maior cobertura assim como uma mais fåcil integração
em sistemas celulares existentes.
Nesta dissertação aborda-se um estudo da sua camada fĂsica (PHY Layer)
juntamente com uma implementação comportamental open source em Matlab
das cadeias de transmissão e recepção em downlink. O projecto modela
e executa transmissÔes em downlink (eNodeB) e sua recepcção (terminal)
tanto em ambiente simulado como integrado com um dispositivo de software
defined radio, USRP, para validação laboratorial.
Os resultados obtidos tanto de simulação como co-simulação são apresentados
avaliando a qualidade de transmissĂŁo assim como o comportamento
do equalizador Zero Forcing implementado
A STUDY ON WIRELESS COMMUNICATION ERROR PERFORMANCE AND PATH LOSS PREDICTION
One channel model that characterises multipath fading eïŹect of a wireless channel is
called Flat Rayleigh Fading channel model. Given the properties of Flat Rayleigh Fading
channel, an equation to ïŹnd the capacity of a Flat Rayleigh fading channel with hard
decision decoding is derived. The diïŹerence of power requirement to achieve the Additive
White Gaussian Noise (AWGN) capacity over a Flat Rayleigh Fading channel fading is
found to increase exponentially with Es /N0 . Upper and lower bounds of error performance
of linear block codes over a Flat Rayleigh Fading channel are also studied.
With the condition that the excess delay of a channel is known earlier, it is shown that a
correlator with shorter length, according to excess delay of the channel, can be constructed
for use in wireless channel response measurements. Therefore, a rule of construction
of a shorter length correlator is deïŹned, involving concatenation of parts of a Constant
Amplitude Zero Auto-Correlation (CAZAC) sequence.
Simulation of [136,68,24] Double Circulant Code with Dorsch List Decoding is also
done in order to evaluate error performance of the channel coding scheme over one of the
IEEE Wireless Metropolitan Area Network (WirelessMAN) channel models, the Stanford
University Interim Channel Model No. 5 (SUI-5) channel. Performance of the channel cod-
ing was severely degraded over the SUI-5 channel when it is compared to its performance
over the AWGN channel.
Indoor path losses within three multiïŹoor oïŹce buildings were investigated at 433
MHz, 869 MHz and 1249 MHz. The work involved series of extensive received signal
strength measurements within the buildings for all of the considered frequencies. Results
have shown that indoor path loss is higher within a square footprint building than indoor
path loss in a rectangular building. Parameters of Log-Distance Path Loss and Floor
Attenuation Factor Path Loss models have been derived from the measurement data. In
addition, a new indoor path loss prediction model was derived to cater for path loss pre-
diction within multiïŹoor buildings with indoor atriums. The model performs with better
prediction accuracy when compared with Log-Distance Path Loss and Floor Attenuation
Factor Path Loss models.Ministry of Higher Education of Malaysia, Universiti Teknologi Malaysi
Study Of Code Division Multiple Access (CDMA) Technique For Mobile Communication Systems
This report presents details study of CDMA technique for mobile
communication systems. The objective of this project is to understand the spread
spectrum techniques including DS-CDMA and also to explain IS-95A system. The test
results for simulation on the IS-95A Reverse traffic channel are included to evaluate the
performance of the channel under various traffic conditions. Various conditions are
applied to the system to decide on the best performance. The performance of the channel
was measured in terms of BER. Reasonable Doppler shift frequency is determined. It is
found that performance of the system vary with the reduced of data rate. Amount of
AWGN added to the signal represents the interference generated by other base station
nearer. Therefore changes of SNR in the AWGN Channel provoke the system
performance. The detection performance improves with an increase in the SNR
Blind iterative multiuser detection for error coded CDMA systems.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.Mobile communications have developed since the radio communications that were in use 50 years ago. With the advent of GSM, mobile communications was brought to the average citizen. More recently, COMA technology has provided the user with higher data rates and more reliable service, and it is apparent that it is the future of wireless communication. With the introduction of 3G technology in South Africa, it is becoming clear that it is the solution to the country's wireless communication requirements. The 3G and next-generation technologies could provide reliable communications to areas where it has proven difficult to operate and maintain communications effectively, such as rural locations. It is therefore important that the se technologies continue to be researched in order to enhance their capabilities to provide a solution to the wireless needs of the local and global community. Whilst COMA is proving to be a reliable communications technology, it is still susceptible to the effects of the near-far problem and multiple-access interference. A number of multiuser detectors have been proposed in literature that attempt to mitigate the effects of multiple-access interference. A notable detector is the blind MOE detector, which requires only the desired user 's spreading sequence , and it exhibits performance approximating that of other linear multiuser detectors. Another promising class of multiuser detector operate using an iterative principle and have a joint multiuser detection and error-correcting coding scheme. The aim of this research is to develop a blind iterative detector with FEC coding as a potential solution to the need for a detector that can mitigate the effects of interfering users operating on the channel. The proposed detector has the benefits of both the blind and iterative schemes: it only requires the knowledge of the desired user ' s signature, and it has integrated error-correcting abilities. The simulation results presented in this dissertation show that the proposed detector exhibits superior performance over the blind MOE detector for various channel conditions. An overview of spread-spectrum technologies is presented, and the operation of OS-COMA is described in more detail. A history and overview of existing COMA standards is also given . The need for multiuser detection is explained, and a description and comparison of various detection methods that have appeared in literature is given. An introduction to error coding is given , with convolutional code s, the turbo coding concept and method s of iterative detection are described in more detail and compared, as iterat ive decoding is fundamental to the operation of an iterative COMA detector. An overview of iterative multiuser detection is given , and selected iterative methods are described in more detail. A blind iterative detector is proposed and analysed. Simulation results for the propo sed detector, and a comparison to the blind MOE detector is presented, showing performance characteristics and the effects of various channel parameters on performance. From these results it can be seen that the proposed detector exhibits a superior performance compared to that of the blind MOE detector for various channel conditions. The dissertation is concluded, and possible future directions of research are given
Técnicas de equalização e pré-codificação para sistemas MC-CDMA
Mestrado em Engenharia EletrĂłnica e TelecomunicaçÔesO nĂșmero de dispositivos com ligaçÔes e aplicaçÔes sem fios estĂĄ a aumentar exponencialmente, causando problemas de interferĂȘncia e diminuindo a capacidade do sistema. Isto desencadeou uma procura por uma eficiĂȘncia espectral superior e, consequentemente, tornou-se necessĂĄrio desenvolver novas arquitecturas celulares que suportem estas novas exigĂȘncias.
Coordenação ou cooperação multicelular Ă© uma arquitectura promissora para sistemas celulares sem fios. Esta ajuda a mitigar a interferĂȘncia entre cĂ©lulas, melhorando a equidade e a capacidade do sistema. Ă, portanto, uma arquitectura jĂĄ em estudo ao abrigo da tecnologia LTE-Advanced sob o conceito de coordenação multiponto (CoMP). Nesta dissertação, considerĂĄmos um sistema coordenado MC-CDMA com prĂ©-codificação e equalização iterativas.
Uma das tĂ©cnicas mais eficientes de prĂ©-codificação Ă© o alinhamento de interferĂȘncias (IA). Este Ă© um conceito relativamente novo que permite aumentar a capacidade do sistema em canais de elevada interferĂȘncia. Sabe-se que, para os sistemas MC-CDMA, os equalizadores lineares convencionais nĂŁo sĂŁo os mais eficientes, devido Ă interferĂȘncia residual entre portadoras (ICI). No entanto, a equalização iterativa no domĂnio da frequĂȘncia (FDE) foi identificada como sendo uma das tĂ©cnicas mais eficientes para lidar com ICI e explorar a diversidade oferecida pelos sistemas MIMO MC-CDMA. Esta tĂ©cnica Ă© baseada no conceito Iterative Block Decision Feedback Equalization (IB-DFE).
Nesta dissertação, Ă© proposto um sistema MC-CDMA que une a prĂ©-codificação iterativa do alinhamento de interferĂȘncias no transmissor ao equalizador baseado no IB-DFE, com cancelamento sucessivo de interferĂȘncias (SIC) no receptor. Este Ă© construĂdo por dois blocos: um filtro linear, que mitiga a interferĂȘncia inter-utilizador, seguido por um bloco iterativo no domĂnio da frequĂȘncia, que separa eficientemente os fluxos de dados espaciais na presença de interferĂȘncia residual inter-utilizador alinhada. Este esquema permite atingir o nĂșmero mĂĄximo de graus de liberdade e permite simultaneamente um ganho Ăłptimo de diversidade espacial. O desempenho deste esquema estĂĄ perto do filtro adaptado- Matched Filter Bound (MFB).The number of devices with wireless connections and applications is increasing exponentially, causing interference problems and reducing the systemâs capacity gain. This initiated a search for a higher spectral efficiency and therefore it became necessary to develop new cellular architectures that support these new requirements.
Multicell cooperation or coordination is a promising architecture for cellular wireless systems to mitigate intercell interference, improving system fairness and increasing capacity, and thus is already under study in LTE-Advanced under the coordinated multipoint (CoMP) concept. In this thesis, efficient iterative precoding and equalization is considered for coordinated MC-CDMA based systems.
One of the most efficient precoding techniques is interference alignment (IA), which is a relatively new concept that allows high capacity gains in interfering channels. It is well known that for MC-CDMA systems standard linear equalizers are not the most efficient due to residual inter carrier interference (ICI). However, iterative frequency-domain equalization (FDE) has been identified as one of the most efficient technique to deal with ICI and exploit the inherent space-frequency diversity of the MIMO MC-CDMA systems, namely the one based on Iterative Block Decision Feedback Equalization (IB-DFE) concept.
In this thesis, it is proposed a MC-CDMA system that joins iterative IA precoding at the transmitter with IB-DFE successive interference cancellation (SIC) based receiver structure. The receiver is implemented in two steps: a linear filter, which mitigates the inter-user aligned interference, followed by an iterative frequency-domain receiver, which efficiently separates the spatial streams in the presence of residual inter-user aligned interference. This scheme provides the maximum degrees of freedom (DoF) and allows almost the optimum space-diversity gain. The scheme performance is close to the matched filter bound (MFB)
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