[en] Bit-rate and quality of service demands of new wireless communication standards are pushing signal theory and algorithm implementation to their limits. One of the main strategies which are being used to achieve the demanded rates is the multiple input-multiple output (MIMO) technique, which employs multiple antennas, both at transmission and reception. This PhD dissertation concentrates on the analysis of the e ects of channel estimation, specially complex due to the number of parameters to estimate, on the performance of MIMO detectors, focusing on both practical and theoretical aspects. The practical analysis has been addressed by designing and developing a real-time wireless MIMO communication platform. A whole 2 £ 2 system has been implemented which has allowed to evaluate the e ects of a real hardware implementation on the performance of the MIMO receiver. A zero-forcing (ZF) detector and a sphere decoder (SD) have been implemented in order to evaluate their degradation in bit error rate (BER) performance in a realistic environment including synchronization, channel estimation or quantization e ects. On the other hand, a simulation-based analysis has been carried out to evaluate the e ects of channel estimation on the comparative performance of the main detectors in fundamental MIMO systems, including narrowband, orthogonal frequency-division multiplexing (OFDM) and single-carrier with frequency-domain equalization (SCFDE) schemes. The e ects of channel estimation on iterative Turbo-MIMO systems have also been analyzed, proposing a performance prediction tool based on analytical extrinsic information transfer (EXIT) functions. Finally, a parallel decision-directed semi-iterative channel estimation architecture has been proposed which is specially designed to t in eld-programmable gate array (FPGA) devices and solves some of the problems of other iterative approaches with a moderate complexity.

[eu] Haririk gabeko komunikazio estandar berrien zerbitzu-kalitate eta abiadura eskaerek seinalearen teoria eta algoritmoen hardware inplementazioa euren mugetaraino daramatzate. Aipatutako abiadurak lortzeko erabiltzen ari diren tekniketako bat, garrantzitsuena agian, MIMO (multiple input-multiple output) delako sistema da, non antena anitz erabiltzen diren, bai igorlean baita hartzailean ere. Doktoretza-tesi honen gai nagusia MIMO kanalaren estimazioan datza eta honek MIMO hartzailean duen efektua ikertzea du helburu, bereziki garrantzitsua suerta baitaiteke estimatu beharreko parametro kopuru handia dela eta. Bi bide ezberdin jarraitu dira ikerketa jorratzeko: bata praktikan oinarritua eta bestea, aldiz, teorian. Atal praktikoan denbora errealeko prototipaia plataforma bat diseinatu eta sortu da. Honetaz gain, 2 £ 2 MIMO sistema oso bat ere gauzatu da, benetako inplementazio baten eragina ikertzeko balio izan duelarik. Dekodi katzaile esferikoa eta ZF (zero-forcing) detektoreak gauzatu dira, sistema erreal baten ondorioak (sinkronizazioa, estimazioa, zenbakapena, e.a) kontutan hartu ahal izateko. Bestalde, simulazioetan oinarritutako ikerketa teorikoa ere jorratu da, kanalaren estimazioak MIMO hartzaile garrantzitsuenetan daukan eragina aztertuz. MIMO sistema mota nagusienak hartu dira kontuan: banda estukoa, OFDM (orthogonal frequency-divison multiplexing) eta SCFDE (single carrier with frequency-domain equalization). Era berean, kanalaren estimazioaren erroreak Turbo-MIMO direlako sistema iteratiboetan daukan eragina ere aztertu da, EXIT (extrinsic information transfer) funtzio analitikoetan oinarritutako ebaluaketa tresna proposatu delarik. Azkenik, aurreko ataletatik ateratako ondorioetan oinarrituz kanalaren estimazio iteratiborako arkitektura paraleloa proposatu da. Proposaturiko arkitektura hau erraz gauza daiteke FPGA ( eld-programmable gate array) gailu programagarri batean eta beste estimazio tekniken hainbat akats saihes ditzake konplexutasuna neurriz kanpo gehitu gabe.