Nunzio Aldo D'Andrea

Design and analysis of a jitter-free clock recovery scheme for QAM systems

Performance of the digital clock recovery scheme proposed by F.M. Gardner (1986), when applied to quadrature-amplitude-modulation (QAM) microwave radio communication systems is investigated. In particular, it is shown how to improve such a scheme by means of appropriate prefiltering of the incoming signal. The impulse response of the shaping filter is designed to achieve pattern-jitter-free clock recovery in the case of an ideal transmission channel. The impact of multipath fading on synchronizer performance is evaluated by means of computer simulation. >

A Simulation Study of Clock Recovery in QPSK and 9QPRS Systems

Computer simulation is employed to assess jitter performance of a clock recovery circuit as a function of the characteristics of the rectifier being used. Several types of rectifiers are compared, some operating at baseband, others at intermediate frequency (IF). It is shown that the best choice between them depends both on the modulation format and on the excess bandwidth factor of the pulse spectrum. In QPSK systems, fourth-law rectifiers outperform the others for rolloff factors up to 0.2 while, for higher values, baseband absolutevalue rectifiers are preferable. In the case of 9QPRS, baseband absolutevalue rectifiers provide jitter reductions of one order of magnitude at high signal-to-noise ratios.

Design of transmit and receive digital filters for data communications

This paper describes a design method for the synthesis of digital filters in data communication systems. The coefficients in the transmit and receive filters are optimized to meet specified requirements on (i) out-of-band emission, (ii) intersymbol interference, (iii) adjacent channel interference and (iv) thermal noise immunity. >

Power Allocation for Goodput Optimization in BICM-OFDM Systems

This paper deals with the power allocation problem for coded multicarrier transmission. Specifically, we focus on a bit interleaved coded modulation (BICM) packet transmission implemented with orthogonal frequency division multiplexing (OFDM) and in the presence of automatic repeat request (ARQ) protocol. Capitalizing on the binary-input output-symmetric (BIOS) nature of the BICM channel it is provided a simple upper-bound of the rate of information bits received without any error, the so called goodput. Based on this theoretical characterization, we develop a power allocation strategy among the different subcarriers so that the system goodput performance metric is maximized. The effectiveness of the proposed method is numerically testified for BICM-OFDM transmission in the context of the typical WLAN scenario.

Reduced-PAPR Code Allocation Strategy for MC-CDMA Transmissions

First, an approximate expression for the peak-to-average power ratio (PAPR) of a multi-carrier code-division multiple access (MC-CDMA) signal is analytically derived. Then, it is demonstrated that the PAPR of a MC-CDMA signal can be suitably reduced by resorting to a judicious strategy for the allocation of the signature codes. Based on such a result, a low-complexity implementation of the proposed strategy is presented and its performance gain over the random allocation strategy is numerically assessed in terms of PAPR and out-of-band emissions.

Optimum Goodput-Oriented Power Allocation Policy for BIC-OFDM Packet Transmissions

In this contribution we study the optimal power allocation scheme for a coded multicarrier transmission. Specifically, we focus on a bit interleaved coded modulation (BICM) packet transmission implemented with orthogonal frequency division multiplexing (OFDM) and in the presence of automatic repeat request (ARQ) protocol. Based on a simple lower-bound of the rate of information bits received without any error, the so called goodput, we develop a power allocation strategy among the different subcarriers so that the system goodput performance metric is maximized. We also demonstrate the optimality of the solution for the proposed objective function under the given power constraint. The effectiveness of the power allocation policy is numerically testified for BIC-OFDM transmission in the context of typical indoor environment.