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Ultra-wideband (UWB) radios are expected to be the next generation of the transmission systems that can support high data rate and power-constrained applications. Since the UWB signals have wide bandwidth, two problems arise, namely the high speed analog-to-digital-converter (ADC) required at the receiver side and the coexistence with other narrowband interference (NBI) systems that share the same...
In this paper, we present a low complexity Time Of Arrival (TOA) estimator for direct-sequence ultra-wideband (DS-UWB) ranging system. With the assumption that TOA is the integer multiples of chip duration, our decoupled multiuser ranging (DEMR) estimator employs integrate-and-dump filter (IDF) in chip sampling rate instead of matched filter (MF) as the front-end to reduce sampling rate and to simplify...
We propose a null sub-carrier based carrier frequency offset (CFO) estimation technique for OFDMA uplink systems. We discuss the effect of multi-user interference and channel nulls on the identifiability of CFO estimation. We also derive the CFO acquisition range of the algorithm and the optimum location of the null sub-carriers. We prove that the identifiability due to multi-user interference is...
Fast and accurate Carrier Frequency Offset (CFO) estimation is a problem of significance in many multi-carrier modulation based systems, especially in uplink Orthogonal Frequency Division Multiple Access (OFDMA) where the presence of multiple users exacerbates the inter-carrier interference (ICI) and results in multi-user interference (MUI). In this paper, a new technique called partial FFT demodulation...
This paper addresses the effect of timing synchronization errors for two different multicarrier techniques CPOFDM and FBMC. Such errors degrade the performance of the reference receiver by causing multi user interference. This interference occurs when the signals from different transmitters arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of orthogonality...
The multi-access orthogonal frequency division multiplexing (OFDMA) technology has drawn a lot of attention in next generation wireless mobile communications. It is well-known that carrier frequency offsets in OFDMA systems can destroy the orthogonality among subcarriers and produce intercarrier interference (ICI) and multiuser interference (MUI). In our previous works, we proposed a common carrier...
This is a recent research on Space-Division-Multiple-Access-Orthogonal frequency Division Multiplexing (SDMA-OFDM) for channel estimation based on iterative joint channel estimation and a new Genetic Algorithm (GA). Assisted iterative joint channel estimation and Multi-User Detection (MUD) is the most recent approach for MTMO SDMA-OFDM systems and GA-aided MUD techniques for providing the best capacity...
The effect of a common carrier frequency offset (CFO) at the OFDMA receiver is explored in this paper. In conventional CFO compensation methods for OFDMA systems, the CFOs are usually compensated for by directly eliminating the intercarrier interference (ICI) caused by the residual CFOs for individual users. Besides the ICI, the multiuser interference can be also introduced at the OFDMA receiver due...
This paper presents a novel blind method to estimate carrier frequency offsets (CFOs) in OFDMA uplink. The major idea is employing a linear precoder to establish time correlation, which offers a second-order moments based blind CFO estimation for each user. With a careful precoder design, the interference from adjacent users can be considerably mitigated in CFO estimation. Since the majority of interference...
Energy-detection receivers are appealing to IEEE 802.15.4a low data-rate networks because of their low complexity. With a reasonable energy consumption, these receivers can exploit the ranging capabilities and multipath resistance of impulse-radio UWB (IR-UWB). However, the performance of energy-detection receivers can be severely degraded by multi-user interference (MUI). One solution may be to coordinate...
This paper presents positioning results determined by a multi-layer, packet based OMNet++ simulator for communication and positioning in an autonomous wireless sensor network. The simulator includes an IR-UWB physical layer model considering the impact of multi-user interference, a highly flexible MAC layer which performs physical layer adaptations to optimize the total link performance, and a ranging...
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