INTRODUCTION
ULTRA wideband impulse radio (UWB-IR) technology is an attractive choice to support high-rate data communications and low-rate precise location and ranging. Time-hopping M-ary pulse position modulation (TH-MPPM) has been considered as the main modulation format to meet the demand for higher data rates. In the conventional implementation of MPPM, a single pulse is transmitted in one of the fixed M consecutive pulse positions. In a multipath channel, energy collected from consecutive pulse locations may be interfered by a large portion of multipath-delayed received pulses. This may generate noticeable interference components for the M decision variables, and hence may affect the system performance. To reduce the effect of interference components, one approach is to randomize the consecutive pulse transmit locations using M orthogonal TH codes.
With this approach, (i) the separation between consecutive pulse positions can be increased while the data rate is fixed, and (ii) multiple-access capability can still be maintained with the random selection of user specific TH codes. We refer to this new modulation format as M-ary code shift keying (MCSK) impulse modulation. We initially proposed MCSK as a combined modulation with binary PPM (BPPM) in order to increase the data rate of the conventional TH-BPPM. Combined MCSK/BPPM provided improved system performance at higher data rate if the system design parameters were properly selected.
In this project, MCSK impulse modulation is considered by itself, and studied in detail for comparison to TH-MPPM. MCSK is considered here for both single- and multi-user cases. In the study of single-user case, the effect of multipathdelayed pulses on M decision variables is explicitly provided in terms of channel impulse response coefficients. In the study of multi-user case, an accurate semi-analytic symbolerror rate (SER) expression is derived by considering the generalized Gaussian distribution (GGD) presented in for multi-user interference (MUI) modelling.
Some approximations to MUI modelling are provided in the Results Section. These approximations increase the computational efficiency of numerical analysis significantly with respect to simulations, while still providing accurate results. For both single- and multi-user cases, it is shown that MCSK can provide about 2 dB performance gain over MPPM as it reduces the effects of multipath delays on the decision variables by randomizing locations of the transmit pulse. This performance gain is mainly a result of separatedM decision variables experiencing less interference due to the decaying power delay profile.
ULTRA wideband impulse radio (UWB-IR) technology is an attractive choice to support high-rate data communications and low-rate precise location and ranging. Time-hopping M-ary pulse position modulation (TH-MPPM) has been considered as the main modulation format to meet the demand for higher data rates. In the conventional implementation of MPPM, a single pulse is transmitted in one of the fixed M consecutive pulse positions. In a multipath channel, energy collected from consecutive pulse locations may be interfered by a large portion of multipath-delayed received pulses. This may generate noticeable interference components for the M decision variables, and hence may affect the system performance. To reduce the effect of interference components, one approach is to randomize the consecutive pulse transmit locations using M orthogonal TH codes.
With this approach, (i) the separation between consecutive pulse positions can be increased while the data rate is fixed, and (ii) multiple-access capability can still be maintained with the random selection of user specific TH codes. We refer to this new modulation format as M-ary code shift keying (MCSK) impulse modulation. We initially proposed MCSK as a combined modulation with binary PPM (BPPM) in order to increase the data rate of the conventional TH-BPPM. Combined MCSK/BPPM provided improved system performance at higher data rate if the system design parameters were properly selected.
In this project, MCSK impulse modulation is considered by itself, and studied in detail for comparison to TH-MPPM. MCSK is considered here for both single- and multi-user cases. In the study of single-user case, the effect of multipathdelayed pulses on M decision variables is explicitly provided in terms of channel impulse response coefficients. In the study of multi-user case, an accurate semi-analytic symbolerror rate (SER) expression is derived by considering the generalized Gaussian distribution (GGD) presented in for multi-user interference (MUI) modelling.
Some approximations to MUI modelling are provided in the Results Section. These approximations increase the computational efficiency of numerical analysis significantly with respect to simulations, while still providing accurate results. For both single- and multi-user cases, it is shown that MCSK can provide about 2 dB performance gain over MPPM as it reduces the effects of multipath delays on the decision variables by randomizing locations of the transmit pulse. This performance gain is mainly a result of separatedM decision variables experiencing less interference due to the decaying power delay profile.
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