In order to meet the ever-growing demand for mobile data, a number of different technologies
have been adopted by the fourth generation standardization bodies. These include multiple access
schemes such as spatial division multiple access (SDMA), and efficient modulation techniques
such as orthogonal frequency division multiplexing (OFDM)-based modulation. The
specific objectives of this theses are to develop an effective feedback method for interference
management in smart antenna SDMA systems and to design an efficient OFDM-based modulation
technique, where an additional dimension is added to the conventional two-dimensional
modulation techniques such as quadrature amplitude modulation (QAM).
In SDMA time division duplex (TDD) systems, where channel reciprocity is maintained, uplink
(UL) channel sounding method is considered as one of the most promising feedback methods
due to its bandwidth and delay efficiency. Conventional channel sounding (CCS) only conveys
the channel state information (CSI) of each active user to the base station (BS). Due to
the limitation in system performance because of co-channel interference (CCI) from adjacent
cells in interference-limited scenarios, CSI is only a suboptimal metric for multiuser spatial
multiplexing optimization. The first major contribution of this theses is a novel interference
feedback method proposed to provide the BS with implicit knowledge about the interference
level received by each mobile station (MS). More specifically, it is proposed to weight the
conventional channel sounding pilots by the level of the experienced interference at the user’s
side. Interference-weighted channel sounding (IWCS) acts as a spectrally efficient feedback
technique that provides the BS with implicit knowledge about CCI experienced by each MS,
and significantly improves the downlink (DL) sum capacity for both greedy and fair scheduling
policies. For the sake of completeness, a novel procedure is developed to make the IWCS pilots
usable for UL optimization. It is proposed to divide the optimization metric obtained from the
IWCS pilots by the interference experienced at the BS’s antennas. The resultant new metric, the
channel gain divided by the multiplication of DL and UL interference, provides link-protection
awareness and is used to optimize both UL and DL. Using maximum capacity scheduling criterion,
the link-protection aware metric results in a gain in the median system sum capacity of
26.7% and 12.5% in DL and UL respectively compared to the case when conventional channel
sounding techniques are used. Moreover, heuristic algorithm has been proposed in order to
facilitate a practical optimization and to reduce the computational complexity.
The second major contribution of this theses is an innovative transmission approach, referred
to as subcarrier-index modulation (SIM), which is proposed to be integrated with OFDM. The
key idea of SIM is to employ the subcarrier-index to convey information to the receiver. Furthermore,
a closed-form analytical bit error ratio (BER) of SIM OFDM in Rayleigh channel
is derived. Simulation results show BER performance gain of 4 dB over 4-QAM OFDM for
both coded and uncoded data without power saving policy. Alternatively, power saving policy
maintains an average gain of 1 dB while only using half OFDM symbol transmit power
