This paper presents a method for estimating the time of arrival (ToA) of long term evolution (LTE) signals received on multiple separate transmission bands by the same base station (BS) mast. By exploiting the overall bandwidth occupied by the different signals and the correlation between the corresponding channel impulse responses, a higher precision is achieved with respect to the usually adopted single-band approach whenever the time-correlation among the bands is sufficiently high. The ToA estimation is carried out by generalizing the space-alternating generalized expectation-maximization (SAGE) algorithm to the multi-band context, proving that the availability of multiple bands provides a reduced standard deviation for the estimated ToA, with a limited increase of the computational cost. The main analyzed issue consists in the management of the asynchrony between transmitters belonging to distinct cellular operators, which is addressed by developing a suitable method to combine the contributions provided by the different bands. The method is validated by simulations in dual- and tri-band scenarios, and is further applied to real dual-band signals measured through a portable setup and experimentally acquired from an LTE BS mast covering multiple cells.

This paper discusses the use of the Space-Alternating Generalized Expectation-maximization (SAGE) algorithm for Time of Arrival (ToA) estimation in Orthogonal Frequency Division Multiplexing (OFDM) systems. This algorithm, which is an extension of the expectation-maximization approach, can exploit the intrinsic properties of a multi-carrier OFDM system to achieve the estimation of a number of parameters of each incoming signal replica, such as its amplitude, ToA, Doppler shift, and angle of arrival. The SAGE method can also be easily tailored to estimate only a desired subset of these parameters. Accordingly, this study focuses on the sole ToA estimation, but extending the SAGE functionalities to dual-band OFDM systems. This extension is achieved by exploiting the availability at the receiver of more than one band from the same transmitter, and combining the derived channel information to increase the bandwidth available for estimation. It will be shown that, in highly correlated scenarios, the performance of the SAGE algorithm for ToA estimation in a dual-band system is comparable to that of a single-band system with equivalent total bandwidth.

The main concern in nowadays digital communications standards, such as IEEE802.11n, 802.16e (Wi-MAX), 100BaseT Ethernet, and Digital Video Broadcasting (DVB), is the need of adaptive and flexible communication techniques. The request for higher efficiency, both in bandwidth use and power consumption, increases the need for limit-achieving, flexible techniques of channel coding. Low Density Parity Check (LDPC) Codes are very interesting because of their high performances and potential flexibility introduced by puncturing. In this paper, the design of rate-compatible LDPC is addressed. A class of punctured LDPC codes is defined through their equivalent parity check matrices. A formal analysis is provided, based on a simplified approach on the decoding belief propagation algorithm, i.e., considering a Gaussian approximation for message densities under density evolution. A suitable design criterion for the puncturing patterns is then addressed.