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Multiple-Input Multiple-Output (MIMO) communication using multiple antennas has received significant attention in recent years, both in the academia and industry, as they offer additional spatial dimensions for high-rate and reliable communication, without expending valuable bandwidth. However, exploiting these promised benefits of MIMO systems critically depends on fast and accurate acquisition of Channel State Information (CSI) at the Receiver (CSIR) and the Transmitter (CSIT). In Time Division Duplex (TDD) MIMO systems, where the forward channel and the reverse channel are the same, it is possible to exploit this reciprocity to reduce the overhead involved in acquiring CSI, both in terms of training duration and power. Further, many popular and efficient transmission schemes such as beam forming, spatial multiplexing over dominant channel modes, etc. do not require full CSI at the transmitter. In such cases, it is possible to reduce the Reverse Channel Training (RCT) overhead by only learning the part of the channel that is required for data transmission at the transmitter. In this thesis, we propose and analyze several novel channel-dependent RCT schemes for MIMO systems and analyze their performance in terms of (a) the mean-square error in the channel estimate, (b) lower bounds on the capacity, and (c) the diversity-multiplexing gain tradeoff. We show that the proposed training schemes offer significant performance improvement relative to conventional channel-agnostic RCT schemes. The main take-home messages from this thesis are as follows: • Exploiting CSI while designing the RCT sequence improves the performance. • The training sequence should be designed so as to convey only the part of the CSI required for data transmission by the transmitter. • Power-controlled RCT, when feasible, significantly outperforms fixed power RCT.

Made available in DSpace on 2016-04-04T18:31:25Z (GMT). No. of bitstreams: 1 Marcia Maria Savoine.pdf: 2175715 bytes, checksum: 355bcfef34d422002fc47ef44d62e191 (MD5) Previous issue date: 2009-02-06 / This work presents the comparison made through simulations of discreet events, accomplished with the software ARENA, the techniques of Time Division Duplex (TDD) and Frequency Division Duplex (FDD). Techniques present in the pattern IEEE 802.16 and used by WiMAX in the bi-directional channels of uplink and downlink. The simulation model considered in the line of arrival of the services the concept FIFO (First-In, First-Out) and the simulations were accomplished considering five applications (Streaming, Download, Web, E-mail and Small-Transaction) for downlink and uplink. The number of channels in the Base Station varied from 4 to 60, with a throughput of 600 kbps. The regarded efficiency parameter was the minimum number of channels necessary in each one of the standard channels. The simulations were accomplished in three sceneries., In the first scenery it was considered the same profile of traffic for downlink and uplink, in the second scenery a traffic of downlink 2, 5, 10 and 15 times larger than the one of uplink. And, in the third scenery it was considered different proportions of traffics varying from 2 to 5 times more, 5 to 10 times more and from 10 to 15 times more. The analyses were done considering as efficiency parameter the converge of the waiting time of the users. ,It was verified that in asymmetric data traffic, the TDD technique was more efficient and there were spectrum idleness in the FDD technique. / Este trabalho apresenta a compara??o efetuada por meio de simula??es de eventos discretos, realizadas com o software ARENA, das t?cnicas de Duplexa??o por Divis?o no Tempo (TDD) e Duplexa??o por Divis?o da Freq??ncia (FDD), t?cnicas presentes no padr?o IEEE 802.16 e utilizadas pelo WiMAX nos canais bidirecionais de uplink e downlink. O modelo de simula??o considerou na fila de chegada dos servi?os o conceito FIFO (First-In, First-Out) e as simula??es foram realizadas considerando cinco aplica??es (Streaming, Download, Web, E-mail e Small-Transaction) para downlink e uplink. O n?mero de canais na Base Station variou de 4 a 60, com um throughput de 600 kbps. O par?metro de efici?ncia considerado foi o n?mero m?nimo de canais necess?rio em cada um dos canais padr?es. As simula??es foram realizadas em tr?s cen?rios, sendo que, no primeiro cen?rio se considerou o mesmo perfil de tr?fego para downlink e uplink, no segundo cen?rio com tr?fego de downlink 2, 5, 10 e 15 vezes maior que o de uplink. E, no terceiro cen?rio com propor??es variadas de tr?fegos variando de 2 a 5 vezes mais, 5 a 10 vezes mais e de 10 a 15 vezes mais. Realizadas as simula??es foram feitas as an?lises dos desempenhos, tomando como par?metro de efici?ncia a taxa de chegada e o tempo de espera do usu?rio perante aplica??es t?picas utilizadas na tecnologia de banda licenciada WiMAX, que segue este padr?o. A an?lise efetuada permitiu identificar, dada estas condi??es de tr?fego, qual das t?cnicas seria a mais indicada. Constatou-se ainda que em tr?fego de dados assim?tricos a t?cnica TDD se apresentou mais eficiente e, observou-se existir ociosidade de espectro na t?cnica FDD.

The master thesis deals with G.fast and G.mgfast transmission technologies, including their parameters. The work deals with the principle of vector DMT modulation and the possibility of time duplex TDD and full-duplex FDX in two-way communication used in these technologies. The following is a description of the line using the KHM model, which is suitable for simulations in the transmission band using G.fast and G.mgfast technologies. Subsequently, the disturbing effects of crosstalk at the near end of NEXT and the far end of FEXT and their elimination with these technologies are discussing. Part of the work explains supporting calculations to determine the SNR and bit allocation to calculate the baud rate. The work describes the methods of compensation of crosstalk FEXT and NEXT, which affect the resulting baud rate. The work also includes an application for simulation of transmission speed as a function of distance for G.fast and G.mgfast technologies, allowing changing input parameters and adjusting the transmission bandwidth based on G.9700 and G.9701 standards. Also, in work, an application is created to display the compensation of the influence of the transmitted signal crosstalk FEXT and NEXT, which allow the import of measured crosstalk between individual participants. The issue of influencing crosstalk for accurate measurements in the laboratory is also discussing. An application in the MATLAB environment is creating to display the measured characteristics.