SMART ANTENNA PATTERN BEAMFORMING IN THE DESIGN OF MODULATION, CODING AND MULTIPLE ACCESS TECHNIQUES

Abstract

Smart antenna systems hold promise to meet the projected demand for increased channel capacity in future wireless communications services. This dissertation is concerned with the design of signal Index Modulation for switched beam antenna systems, which benefit from the energy efficiency of the antenna gain, in addition to improved bandwidth efficiency. In this research, the latter is accomplished through transmitting spatial streams by indexing beams representing the directions of signal arrival. In particular, this dissertation develops a common framework based on beamforming patterns for the design of modulation, coding, and multiple access techniques. First, this dissertation contributes three schemes that embed information in the radiated beam patterns. As a starting point, beam angle shift keying (BASK) is introduced, where a spatial symbol selects a single active beam for the unmodulated carrier signal. This scheme is then extended to beam angle channel modulation (BACM), where in addition to a spatial stream, an amplitude and phase-modulated (APM) carrier signal is considered. Finally, a generalized BACM (G-BACM) is devised, where the spatial symbol selects two or more simultaneously transmitted beams. In all these modulation schemes, when the transmitter selects one of the M_s beamforming patterns, this increases the spectral efficiency of a spatial stream by log_2(M_s) A key point is that M_s can be much larger than the number of antennas. This contrasts with traditional multiple-input multiple-output (MIMO) systems, where the increase in spectral efficiency is governed by the minimum number of transmit and receive antennas. Secondly, this dissertation extends BASK modulation into a multi-user version referred to as beam angle multiple access (BAMA). Specifically, multiple access on the uplink is achieved by assigning subsets of beams to individual users signaling with BASK. At the base station, over the duration of the spatial symbol, the receiver decides on a subset of possible multiple angles of arrival (AOA) corresponding to spatial symbols from different users. Thirdly, this dissertation proposes a multibeam version of space-time block coding (STBC). By utilizing simultaneous transmissions of two or more beams in G-BACM, this work introduces diversity for the QAM/PSK symbols and increases the reliability of the spatial (beam angle) symbols by providing replicas for the group of beam angle signatures (repetition coding). This dissertation advances efficient spectrum and power utilization in wireless transceivers by exploiting beamforming pattern switching in smart antenna systems. The motivation behind this work is to allow future wireless transceivers operating at higher frequencies to combat high signal attenuation through digital beamforming. BASK is an IM technique where the corresponding index modulation building block is the beam angle of transmit antenna beam pattern (radiation power). BASK is a novel way to transmit information by means of the radiation pattern beam angle or angle of departure (AOD) and consequently angle of arrival (AOA).