Wireline and wireless communications have become indispensable part of our daily life. A variety of devices, such as cellular phones and wireless laptops, have changed the way people communicate and interact. The demand for broadband internet and ubiquitous connectivity such as 3G/4G cellular telephony and wireless LANs has been steadily growing. However wireless devices are hampered by challenges such as fading, mobility, battery life, etc. Recently power line communication which exploits existing infrastructures has emerged as a medium that could overcome these challenges. The ultimate goal of such system is to support the required high data rates within limited resources. Hence, we propose to combine wireline and wireless technologies and investigate coding and modulation schemes that improve transmission date rates. This work consists of three major communication systems of wireline, wireless and hybrid scheme. First, we deal with a discrete time-varying block model that captures cyclostationary nature of power line channel response. In fact, power line channel is timevarying since appliances connected to power lines often exhibit input impedance that is a function of instantaneous amplitude of the mains voltage. Our timevarying block transmission model is suitable to simulate more realistically the effect of the medium, but also facilitates the design of precoders and bit loading methods to better cope with the periodically time-varying channel distortion. This analysis is essential for understanding how precoders deal with time variation of the channel. Second, we investigate wireless cooperative communications with randomized space-time coding, exploiting the advantages of co-located antenna systems. Starting with decentralized randomization schemes and their attainable diversity in flat fading channels, we show these schemes are desirable in the presence of time dispersion due to asynchronism among nodes and frequency selectivity. We then study packet transmission policies in the cross-layer perspective, which is called modified-linear-rule (MLR), that minimize the average power consumed by transmitter under average delay constraints. We generalize the scheme of MLR scheduler to multiuser wireless fading environment and compare it with the performance of the optimal scheduler and the log-linear scheduler. Third, we elaborate on a hybrid PLC/wireless link which is realizable in typical indoor communication networks. We derive analytic forms of single-user and multiuser MIMO channel capacities, and then evaluate relay channel capacities for two channel scenarios; one when channel is perfectly known to transmitter and the other when channel is unknown. We propose adaptive PLC-embedded relaying scheme which involves both decode-and-forward coding and OFDM modulation. We investigate the optimal allocation of transmit powers for the scheme at both source and relay nodes under total power constraints.