In this paper a new partial power and rate adaptation scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO). The conventional adaptive scheme is shown to be a special case of the partially adaptive scheme technique which enables the resulting non-convex optimization problem solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using M-ary ...

In this paper we investigate the performance of an amplify-and-forward multi-input multi-output two way relay network where two sources are equipped with multiple antennas employing maximal ratio transmission and the communication is carried through the selected relay resulting in the largest received power. Assuming the fading channel coefficients are Nakagami-m distributed we derive the sum symbol error rate (SSER) outage probabilities for each user and the overall system. In addition diversity ...

As the analog TV broadcasting channels have become less frequently used in the last decade there has been a great interest in these frequency bands for the deployment of metropolitan local and personal area networks. Among them the local area network standard IEEE 802.11af defines PHY and MAC layer implementation of such networks in these unused frequency bands also named television white space (TVWS). According to the standard the systems may use contiguous or non-contiguous channels during their ...

Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems realistic indoor optical channel modeling becomes an important issue to be handled. In this paper first we obtain new realistic indoor VL channel characterizations and models in a multiple-input multiple-output (MIMO) transmission scenario using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical ...

Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems realistic indoor optical channel modeling becomes an important issue to be handled. In this paper first we obtain new realistic indoor VL channel characterizations and models in a multiple-input multiple-output (MIMO) transmission scenario using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical ...

We deal with transmit antenna selection for space-time coded (STC) systems over multiple input multiple output (MIMO) channels. Using pairwise error probability analysis and simulation results we show that transmit antenna selection based on received power levels does not reduce the achievable diversity order for full rank STCs. Initially we prove the results for Rayleigh flat fading channels and then we state our expectations for the case of frequency selective (FS) fading. In addition to the ...

In this paper the performance of the low complexity modified stack equalizer over frequency-selective fading channels is inspected. With the help of simulation results it is illustrated that by sacrificing the computational complexity insignificantly the performance of the modified equalizer can be made closer to optimum. This equalizer can be used at the receiver of uncoded systems or bit interleaved coded systems with iterative receivers.

This letter considers the effect of channel estimation errors on the performance of space-time coded (STC) systems with transmit and receive antenna selection over quasi-static flat fading channels. By performing pairwise error probability analysis and presenting numerical examples we show that the diversity order achieved with perfect channel state information (CSI) is still achievable with imperfect CSI used both at the antenna selection and the space-time decoding processes. We note that our ...

Optical wireless communications (OWC) and its potential to solve physical layer security (PLS) issues are becoming important research areas in 6G communications systems. In this paper, an overview of PLS in visible light communications (VLC), is presented. Then, two new PLS techniques based on generalized space shift keying (GSSK) modulation with spatial constellation design (SCD) and non-orthogonal multiple access (NOMA) cooperative relaying are introduced. In the first technique, the PLS of the ...

The Visible Light Communication(VLC) has drawn significant attention recently for wireless communication in addressing the performance limitations of wireless systems due to the scarcity of bandwidth. In VLC system the visible lights is used not only for illuminating rooms but also for an optical data transmission. Asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) has been proposed for VLC systems to provide optically power efficient solution in the optical domain. ...