Space-Time Coding for Aeronautical Telemetry: Part I—Estimators

A Soft-Output STBC Decoder for Aeronautical Telemetry

“…where s 0 (t) and s 1 (t) are two SOQPSK-TG signals containing the bit streams b 0 and b 1 and are affected by complexvalue attenuations h 0 and h 1 , respectively. Parameter ∆ε is a differential delay which is generally considered in aeronautical telemetry [2], f 0 is the frequency offset and u(t) is an additive complex white Gaussian noise (AWGN). The received signal is filtered to reduce the noise level and sampled at the bit rate at t = nT and t = nT + ∆ε.…”

“…To do so, it is necessary to estimate the channel parameters and then to feed them to the decoder. In the remaining sections of the paper, we assume that these parameters are perfectly estimated using the estimators described in [2] and are denoted byĥ 0 ,ĥ 1 and ∆τ. Thus, the maximum likelihood (ML) of b performs:…”

“…If the same signals are transmitted simultaneously, the received signal could suffer from severe interference due to the considerable phase angle differences between them. This phenomenon is known in aeronautical telemetry [2] as the "two-antenna problem". Jensen et al showed, in [3], that by applying Alamouti encoding [4], this problem is overcome without the expansion of the re-quired bandwidth.…”

“…This encoding technique was originally developed for MPSK-type modulations to improve the received signal quality while keeping the receiver side processing simple. However, application of this idea in practical aeronautical telemetry systems is not obvious, as emphasized in [2]. This is essentially due to the peculiar nature of aeronautical telemetry modulation (SOQPSK-TG), as described above, and to the fact that the signals are received at each antenna with different delays.…”

“…In this paper, we focus on decoding algorithms and we assume that the necessary parameters listed above are perfectly estimated using the estimation algorithms introduced in [2] for Alamouti encoded SOQPSK-TG signals. Several decoding algorithms have been explored in [5], [6] taking into account the CPM-like nature of SOQPSK-TG at first and then the presence of differential delays.…”