74 research outputs found
PAR-Aware Large-Scale Multi-User MIMO-OFDM Downlink
We investigate an orthogonal frequency-division multiplexing (OFDM)-based
downlink transmission scheme for large-scale multi-user (MU) multiple-input
multiple-output (MIMO) wireless systems. The use of OFDM causes a high
peak-to-average (power) ratio (PAR), which necessitates expensive and
power-inefficient radio-frequency (RF) components at the base station. In this
paper, we present a novel downlink transmission scheme, which exploits the
massive degrees-of-freedom available in large-scale MU-MIMO-OFDM systems to
achieve low PAR. Specifically, we propose to jointly perform MU precoding, OFDM
modulation, and PAR reduction by solving a convex optimization problem. We
develop a corresponding fast iterative truncation algorithm (FITRA) and show
numerical results to demonstrate tremendous PAR-reduction capabilities. The
significantly reduced linearity requirements eventually enable the use of
low-cost RF components for the large-scale MU-MIMO-OFDM downlink.Comment: To appear in IEEE Journal on Selected Areas in Communication
WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.
Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA
Study and implementation of a low complexity receiver using TCH codes
The use of coding in telecommunications systems reveals to be a technique with an essential
contribution to the improvement of the recovery of transmitted signals. Depending on the
circumstances to which a signal is subjected at transmission, by recurring to coding, it is
possible to attenuate the unfavorable effects that result from this process, obtaining a signal
with superior quality in comparison with a scenario where the presence of coding is absent.
This study aims to test the feasibility of a high-rate wireless communications system using
TCH codes being applied to an OFDM signal, subjected to noise components introduced by a
wireless AWGN channel, considering a free path propagation model. Due to their correlation
properties, the use of TCH codes reveals to be adequate since they allow the same codewords
to be used to realize both error correction and channel estimation, mitigating the channels
effects, leading to the realization of a receiver with lower complexity.
With the intent of performing a qualitative analysis to this system, a simple simulation is
executed in MATLAB where an OFDM signal is generated, being therefore applied various
TCH codes and, through channel estimation, obtain the BER for their respective code lengths
and, consequently, coding gains.
The results were obtained for the modulation indexes of 16, 64 and 256-QAM. These
demonstrate that the implementation of TCH codes is a viable option to reduce the rate of
recovered errors, enabling the reception of a signal with better reliability, especially for higher
code lengths and modulation indexes.O uso de codificação em sistemas de telecomunicações revela-se uma técnica com um
contributo essencial na melhoria da recuperação de sinais transmitidos. Dependendo das
circunstâncias às quais um sinal é submetido aquando a sua transmissão, com recurso à
codificação, é possível atenuar os efeitos adversos resultantes deste processo, obtendo uma
qualidade no sinal recebido superior face a um cenário com ausência da mesma.
Este estudo tem como objetivo testar a exequibilidade de um sistema de comunicações sem
fios para alto débito usando códigos TCH e aplicando-os a um sinal OFDM, sujeito a
componentes de ruído introduzidos por um canal sem fios AWGN, considerando um modelo
de propagação em espaço livre. Devido às propriedades de correlação destes códigos, a sua
utilização revela-se adequada pois permite que as mesmas palavras de código sejam utilizadas
para efetuar correção de erros, minimizando os efeitos do canal, possibilitando o
desenvolvimento de um recetor com menor complexidade.
Visando efetuar uma análise qualitativa do sistema, é realizada uma simulação simples em
MATLAB onde é gerado um sinal OFDM ao qual são aplicados diversos códigos TCH,
realizando estimação de canal com a finalidade de obter o BER para os diferentes comprimentos
dos códigos e, consequentemente, ganhos de codificação relativos aos mesmos.
Os resultados obtidos foram realizados para os índices de modulação 16, 64 e 256-QAM.
Estes demonstram que o uso destes códigos é uma opção viável para reduzir os erros detetados,
permitindo recuperar o sinal com maior fiabilidade, especialmente para comprimentos de
código e índices de modulação elevados
WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.
Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA
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