Design and performance analysis of a space-time block coding scheme for single band UWB

Abstract

Abstract-Ultra wide-band (UWB) systems have recently attracted much research interest owing to their appealing features in short-range mobile communications. These features include high data rates, low power consumption, multiple access communications, and precise positioning capabilities. Space-time coding techniques, such as the block coding scheme or the trellis coding scheme, are known to be simple and practical ways to increase both the spectral efficiency and the capacity in wireless communications. So far, few contributions have looked over multiple inputs multiple outputs UWB systems. In this paper, a method to adapt the space-time block coding technique to single band UWB signalling is proposed. A space-time block codec, based on orthogonal pulses to achieve spatial diversity and collect the multipath diversity is developed. A theoretical analysis is conducted to enlighten the performance enhancements provided by the proposed scheme compared to the classic single link scheme. Simulations support analysis, for various numbers of transmit and receive antennas, several types of channel scenarios, and different detection techniques. In a typical studied UWB environment, the results revealed that our proposed scheme improves the bit error rate performances compared to those of a single link scheme and it provides a strong immunity against timing jitter.

A tight closed-form approximation of the log-normal fading channel capacity

“…Thus, the effect of the log-normal fading channel upon any communication system can be modeled by using an equivalent log-normal RV. For instance, it has been shown in [23] that the effect of several independent log-normal multipath attenuation factors of the IEEE 802.15.3a channel model can be appropriately combined into an equivalent lognormal RV. Numerical values of the mean m α and standard deviation σ α of the equivalent log-normal RV α have been obtained considering either MRC or EGC, various numbers of multipath, and different numbers of transmit antennas, in Tables 4.2, 4.3, 5.1 and 5.2 of [23].…”

“…Numerical values of the mean m α and standard deviation σ α of the equivalent log-normal RV α have been obtained considering either MRC or EGC, various numbers of multipath, and different numbers of transmit antennas, in Tables 4.2, 4.3, 5.1 and 5.2 of [23]. These values have been first derived by using a theoretical approach and then verified Number of antenna elements n Ergodic Capacity (nats/s/Hz) Inserting the values of m α and σ α from the Tables 4.2, 4.3 of [23] in (13), the ergodic capacity of a SISO-UWB system over various channel scenarios of the IEEE 802.15.3a channel model, i.e., CM1-4 [2], is plotted in Fig. 5, by applying either EGC or MRC, for N f = 20, N t = 1, and N r = 1.…”

“…6, the ergodic capacity of a MIMO-UWB system over various channel scenarios, i.e., CM2-4, is plotted against the number of antenna elements n which is considered at the transmitter or at the receiver, by applying MRC with N f = 20, and for γ dB = 10 dB. Using (15) and the same method as in [23], we have obtained values of m α and σ α for the different antenna configurations considered in Fig. 6 beforehand.…”

“…In a MIMO-UWB system, assuming perfect channel estimation and accurate timing synchronization, the receiver output SNR associated with equal gain combining (EGC) and maximum ratio combining (MRC) can be expressed as γ = γα, with α defined as follows [23] …”

“…The parameter σ y , known as the dB spread, is between 6 and 12 dB for medium-scale fading [19], between 3 and 5 dB for the SISO indoor UWB channel [2], and between 1 and 4 dB for the MIMO indoor UWB channel as computed in Tables 5.1 and 5.2 of [23]. Without loss of generality, its range of values can be aggregated as σ y ∈ [1,12] dB for most communication systems operating over log-normal fading channels.…”