Technology

Multiple Input Multiple Output (MIMO): Bias in Telecommunication

Executive Summary

Conventional multiple-input multiple-output (MIMO) transceivers need to process at the base band as many signals as antenna paths, thus increasing their cost, size and power consumption. Higher costs of MIMO partially explain the fiasco of conventional MIMO technologies and the application in RFID systems. This research proposal explains an alternative RF-MIMO architecture which characterizes the shifting of spatial signal processing from the base band to the radio-frequency (RF) front-end and in turn solves some of the problems. In essence, only a single stream of data must be down acquired, converted, and processed by the transceiver of RF-MIMO nature, which undertakes adaptive signal combining in the RF domain.

The research proposal focuses on two of the main challenges posed by the new architecture, namely (i) how to design RF circuits allowing precise amplitude and phase control in each branch and (ii) how to find the optimal complex weights to be applied by the RF combiner, especially when multicarrier modulations are used to cope with multipath channels typically encountered in RFID applications.

Table of Contents

Introduction4

Thesis Statement4

Purpose of the Study4

Research problems4

Research questions5

Research objectives5

Importance of Study5

Literature Review and Conceptual Framework5

RF-MIMO Transceiver Architecture5

RF-weighting topologies7

Research Methodology8

Analysis and Anticipated Results9

Limitations and directions for future research and conclusions9

References10

Multiple Input Multiple Output (MIMO): Bias in Telecommunication

Introduction

As compared to traditional Single-input single-output (SISO) systems, Multiple-input multiple-output (MIMO) wireless technology has attained considerable acknowledgement due to its capability to attain higher reliability and spectral efficiency. A full rank MIMO channel is equivalent to orthogonal SISO channels; therefore, to exploit all the benefits of the MIMO channel (multiplexing or diversity gain) parallel antenna paths must be independently processed and acquired at base band (Rashid et al., 2008, pp. 148-160).

Irrespective of several benefits of MIMO systems, the higher costs of the technology have thwarted the commercial deployment. The application is currently restricted to small cost terminals or handsets only. The demand of low cost, low power consumption and compact wireless transceivers is even more important for radio frequency identification (RFID) applications, which explains why conventional MIMO technologies have not found widespread application in RFID systems (Xiao lei Wang and Manikas A. 2007, pp:229-232).

This architecture is currently being studied to increase the rate, coverage and reliability of WLAN 802.11a systems, but the same concept can be applied to RFID applications. The system uses an orthogonal frequency division multiplexing (OFDM) modulation scheme due to its spectral efficiency as well as to its ability to cope with multipath channels typically encountered between RFID tags and readers. Also, we assume that perfect channel state information (CSI) is available at both the transmitter (e.g., an active RFID tag) and the receiver (e.g., an RFID reader). This can be achieved by sending training sequences in a time division duplex mode (Xiao lei Wang and Manikas 2007).

This novel MIMO concept faces two main challenges: one is the design of RF circuits allowing precise amplitude and phase control in each branch; the other is how to choose the optimal weights when OFDM transmissions are ...