The inphase/quadrature (I/Q) amplitude and phase imbalance effects are studied in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. An analytical model for the I/Q imbalance is developed and supported by simulation results. The results indicate that the I/Q imbalance degrades the BER performance considerably. Keywords—Coherent detection, I/Q imbalance, OFDM, optical...

N-continuous orthogonal frequency division multiplexing (NC-OFDM) is a promising technique to obtain significant sidelobe suppression for baseband OFDM signals, in future 5G wireless communications. However, the precoder of NC-OFDM usually causes severe interference and high complexity. To reduce the interference and complexity, this paper proposes an improved time-domain N-continuous OFDM (TD-...

Introduction: In next generation mobile communications systems, a very high-speed data transmission under severe frequency selective fading environments is required, particularly on the down link (baseto-mobile) [1]. Recently, orthogonal frequency division multiplexing (OFDM), that transmits many narrowband data-modulated orthogonal subcarriers in parallel, has gained much attention. Meanwhile,...

This paper presents a new algorithm for the channel estimation of the OFDM system based on a pilot signal for the new generation of high data rate communication systems. In orthogonal frequency division multiplexing (OFDM) systems over fast-varying fading channels, channel estimation and tracking is generally carried out by transmitting known pilot symbols in given positions of the frequency-ti...

Two types of repetition preambles are compared concerning frequency synchronization in burst transmission. A near–optimum frequency estimation algorithm with scalable lock–in range is proposed in conjunction with a reduced–overhead synchronization preamble, the so–called sandamble. Even though the fundamental ideas are independent from the specific modulation scheme, we study the algorithms in ...

Themulticarrier orthogonal code divisionmultiplexing (MC-OCDM) introduced here has been designed for very wide bandwidth (VWB) point-to-point and point-to-multipoint transmission. In order to meet VWB transmission requirements, the MC-OCDM design has two components, the basic and the composite. The basic MC-OCDM is a generalized form of the standard orthogonal frequency division multiplexing (O...

Orthogonal Frequency Division Multiplexing (OFDM) is a key technique for achieving high data rates and spectral efficiency requirements for wireless communication systems. This paper presents a modeling and simulation of OFDM based on WLAN standard (IEEE 802.11a). Performance of OFDM is evaluated for different modulation schemes such as PSK, QAM, DQPSK, and OQPSK. The performance of OFDM is com...

In this paper a new approach is presented to alleviate the undesirable effects due to the high peak-to-average power ratio of orthogonal frequency division multiplexing. A class of signaling called OFDM angle modulation is presented. These constant envelope OFDM based signals guarantee a 0dB PAPR thus are well suited for efficient nonlinear power amplification. This paper focuses on binary OFDM...

In this paper we investigate the suitability and performance of space-frequency block coded Multi-band orthogonal frequency division multiplexing (MB-OFDM) system under UWB channel model. The employment of transmit diversity techniques based on block codes is expected to achieve enhancement in such systems since it greatly reduces the detrimental effects of multipath fading. In the proposed MB-...

In this paper we describe a coding, modulation, and spatial processing technique for fixed broadband wireless Internet access applications and provide examples of its performance. This technique is built on Orthogonal Frequency Division Multiplexing (OFDM) and is known as Vector OFDM (VOFDM). We compare VOFDM with conventional Single Carrier Modulation (SCM), and show that it provides substanti...