Design of single-carrier frequency domain equalization (SC-FDE) with transmit diversity for wireless and optical communications
Department of Electrical and Computer Engineering
Doctor of Philosophy
Electrical Computer Engineering
Mandayam, Narayan B.
As the demand of wireless service is rising, there is a need to transmit high-speed packets over the wireless communication channel. Broadband data transmission over wireless channels commonly faces the challenges of multipath fading channels, which are both time and frequency selective. There is then a need to design transmission techniques that can combat the adverse effects of the channel, and enable reliable high data rate wireless services. Orthogonal frequency division multiplexing (OFDM) has become widely accepted primarily because of its robustness against frequency selective fading channels, but it suffers a number of drawbacks such as high peak-to-average power ratio (PAPR), a need for an adaptive or coded scheme to overcome spectral nulls in the channel, and high sensitivity to frequency oset and phase noise. Single carrier with frequency domain equalization (SC-FDE) transmission utilizes single carrier modulation at the transmitter, and it performs frequency domain equalization at the receiver. SC-FDE is a technique in which, similar to OFDM, equalization is performed in the frequency domain, but has the advantage of having lower PAPR. This is important especially in the uplink communications, where lower PAPR greatly benefits the mobile terminal in terms of transmit power efficiency and manufacturing cost. Transmit diversity systems, such space-time block coding (STBC) and space- frequency block coding (SFBC) have be proven to increase the performance of wireless system by exploiting the spatial diversity of the channel.
In this dissertation, the authors focus on a transceiver (transmitter and receiver) design for effective and efficient transmission and reception of single carrier transmission through radio-frequency (RF) and optical wireless (OW) communication dispersive channels. This dissertation is divided into five main sections.
In the first part, a physical layer hybrid automatic repeat request (HARQ) system that combines the advantages of the SC-FDE and transmit diversity on the uplink of wireless communication is presented. The proposed technique can achieve high throughput and high spectral efficiency in both time and frequency selective multipath channel. An analytical and numerical analysis of the proposed transmit diversity SC-FDE/HARQ in a single user system is provided. In general, redundant symbols are de facto transmitted in a space-time block coding system. It is shown that the system throughput can be optimized by sending the redundant symbol of a STBC block only if necessary. The performance of the proposed technique is analyzed in both slow and fast fading channel.
In the second part, the authors extend the proposed SC-FDE/HARQ to a multiuser system. This dissertation oers a new approach to designing a low complexity transmission scheme based on space-time block spreading technique that achieves a multiuser interference (MUI)-free detection at the receiver in a slow and fast fading dispersive channel. Two approaches respectively relying on chip-interleaving and chip-superimposition have been proposed to achieve the MUI-free detection.
In the third part the performance of multiuser space-time spreading system in a time varying channel is presented and a closed form expression for the average bit error rate as a function of the channel correlation coefficient is derived.
In the fourth part of this dissertation, a transmission technique for optical wire- less transmission using SC-FDE is proposed. While in RF systems, the power amplifier (PA) in the transmitter is the main component that cause non-linearity distortion due to large PAPR signals, in optical wireless systems, the main source of non-linearity is the light emitting diode (LED) that is used to convert the electrical signal into optical power to be transmitted using intensity modulated direct detection (IM/DD). Since in IM/DD, a real positive signal must be used to modulate the instantaneous power of the optical carrier, and since the LED is a non linear device, a new technique to generate low PAPR signal over a frequency selective optical channel is proposed.
Finally in the last part of this dissertation, a new technique to generation MIMO correlated fading channel impulse responses is proposed. The applicability of the proposed techniques is demonstrated by examples involving the accurate simulation of nonisotropic fading channel models.
njit-etd2011-001 (185 pages ~ 3,407 KB pdf)
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Created May 13, 2011