Color-shift keying (CSK) is a modulation scheme used in visible light communication (VLC) to transmit data by varying the intensity of red, green, and blue LEDs. We study the channel coding for VLC using CSK under constraints of no color shift and no illumination flicker during transmission and design codes over newly introduced symmetric symbol constellations over a triangle intensity plane. One class of codes contains the transmitted sequence based on finite-state machines, and the other is based on the concept of trellis-coded modulation for mitigating color shifts during transmission. The codes have a trellis structure which allows optimal soft-decision decoding using the Viterbi algorithm providing asymptotic coding gain improvements of 1.5 to 3.5 dB with respect to the uncoded transmission while complying with the color shift and flicker constraints.

The effective rate is an important metric that takes delay quality of service (QoS) requirements into consideration while analyzing the performance of wireless systems. In this paper we analyze the effective rate of multiple-input single-output (MISO) systems with transmit antenna selection (TAS) subject to Rayleigh fading. Specifically, we derive an analytical expression for the effective rate of MISO/TAS systems and closed form expressions for the effective rate in asymptotically high and low signal-to-noise ratio (SNR) regimes. Furthermore, we analyze the effective rate of MISO/TAS systems with large number of transmit antennas and derive an asymptotic analytical expression for it.

We analyze the asymptotic average throughput of a multiuser diversity (MD) scheme, in the limit of large number of users, for free space optical (FSO) communication systems over a gamma-gamma fading channel. It is assumed that the FSO system consists of an optical transmitter (central node) equipped with K transmit apertures to serve K users (one transmit aperture for each user). It is also assumed that each user is equipped with N receive apertures and equal gain combining (EGC) is employed at the user's receiver. In MD, the central node serves only one user which has the largest channel gain among the K users, while other users remain silent. Using extreme value theory (EVT), we derive a simple and tight upper bound on the asymptotic average throughput of the considered FSO system. Moreover, the asymptotic average bit error rate (BER) is investigated and a closed form approximation for the average BER of the FSO system with MD#x002F;EGC scheme is obtained.

The IEEE 802.15.7 standard for visible light communication (VLC) includes the use of run-length-limited codes to mitigate modulation-induced flickering and the further use of coding to improve bit error rate performance. In this paper, we introduce algorithms to design codes using finite-state machines, which provide simultaneously a coding gain while also mitigating flicker. The codes have the additional advantage of being optimally soft-decision decodable using the Viterbi algorithm. To compare the flicker mitigation performance of different codes, we further introduce a mathematical measure of flicker based on the power spectrum of the transmitted signals. We discuss tradeoffs between flicker mitigation, code rate, and coding gain, design several codes, and compare their error rate and flicker mitigation performance to some codes in the VLC standard.

The IEEE 802.15.7 standard on visible light communications (VLC) proposes color-shift-keying (CSK) as a way to increase data rate while keeping a constant optical power. In this paper, we propose two algorithms to design codes by finite state machines (FSM) using newly introduced CSK constellations. These codes ensure a constant perceived color eliminating the use of the scrambler proposed by the standard. Furthermore, they achieve about 1 to 3 dB of coding gain compared with the standard constellations and are optimally and efficiently softdecision decodable using the Viterbi algorithm.