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In this paper, we propose a method to minimize the Multi-User Interference (MUI) caused by multiple access (MA) in a Time Hopping Ultra Wide Band (TH-UWB) system with line-of-sight (LOS) multi-path channel in a residential environment IEEE 802.15.4a channel model. We considered synchronous case over an Additive White Gaussian Noise channel (AWGN). The problem is formulated as a combinatorial optimization...
Space-time focusing transmission in impulse-radio ultra-wideband (IR-UWB) systems resorts to the large number of resolvable paths to reduce the inter-pulse interference as well as the multiuser interference, and to simplify the receiver design. In this paper, we study the spatial user capacity of IR-UWB systems with space-time focusing transmission where the users are randomly distributed. We will...
Recently, a block spreading code division multiple access (BS-CDMA) technique was presented whereby user-specific preceding along with orthogonal spreading codes are used to achieve multi-user interference (MUI) free when all users arrive at the base station simultaneously. In practice however, imperfect synchronization destroys the orthogonality among users and MUI occurs. This paper investigates...
In this paper, a time and frequency (TF) domain spreading multicarrier direct sequence code division multiple access (MC-DS-CDMA) scheme employing zero correlation zone (ZCZ) sequences, designed specifically for quasi-synchronous uplink transmissions, is proposed to exploit frequency and temporal diversity in frequency-selective block-fading channels. This is in contrast to previously proposed schemes...
Recently, attention on wireless communications has been shifted from multiple-input multiple-output (MIMO) systems to multiuser MIMO (MU-MIMO) systems, which serve several users simultaneously in frequency and time. For a system with multiantenna users, block diagonalization (BD) is a technique, where multiuser interference can be completely canceled. For realizing the BD algorithm, the base station...
In this paper, a comparative analysis of the performance of the non-synchronized initial random access channel in mobile WiMAX and E-UTRA systems under different conditions (fast fading, multiuser interference) is carried out. The analysis is focused on the correlation properties of the code sequences used in each case. We evaluate their ability to provide low values for false alarm and erroneous...
In this paper, we propose a communications receiver architecture composed of a time-reversal approach to simplify the shallow underwater acoustic channel and to suppress multiuser interference followed by an iterative, successive interference cancellation (SIC) scheme to cancel the remaining interference. The SIC process is the multiuser interference equivalent of the decision-directed, feedback equalizer...
This paper investigates the effect of introducing cognitive mechanisms in the routing module of a wireless network. A routing cost function that incorporates measurements of both internal network status and instantaneous behavior of external world is described. The proposed cost function is analyzed by simulation in the framework of IEEE 802.15.4a-like low data rate and low cost networks for mixed...
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