Ternary ZCD-UWB communication system having novel interference-cancellation property

Time-hopping ultra wideband (TH-UWB) and direct-sequence ultra wideband (DS-UWB) systems are among the standards proposed for UWB communications scenarios. A general unified mathematical approach has been proposed for calculating the bit error rate (BER) for both TH-UWB and DS-UWB systems in the presence of multiple-user interference and a strong narrow-band interference in a multi-path scenario. Unlike many other mathematical models that provide upper or lower bounds for BER, this model calculates the exact values for BER in given scenarios. A partial rake receiver has been chosen as the receiving terminal. The modified Saleh-Valenzuela channel model has been used in this analysis. The model can asses the effect of any given narrow-band interfering systems. For the purpose of simulation, the narrow-band interfering system used is a Wi-Max transceiver based on IEEE 802.16-2004 standard. The validity of the model has been checked by comparing the mathematical results with numerical values achieved trough simulation. It is important to notice that this method can simultaneously be applied to both TH-UWB and DS-UWB.

An adaptive multiuser detector (MUD) is proposed for direct-sequence ultra-wideband (DS-UWB) multiple access communication systems to suppress both multiple access interference (MAI) and inter-symbol interference (ISI). In this contribution, considering the MUD from a combination viewpoint, we proposed a MUD based on electromagnetism-like (EM) method, which applied the concept of EM search to Hopfield neural network (EMHNN) for solving optimization problems. We analyze the performance of the EMHNN MUD in multipath fading channel, and compare it with the optimum detector and several suboptimum schemes such as conventional, decorrelator detector (DD), minimum-mean-squared error (MMSE) and HNN MUD. Simulation results will demonstrate that the proposed EMHNN MUD, which alleviates the detrimental effects of the MAI problem, can significantly improve the system performance.

In this paper, we evaluate the computational complexity and the performance of the RAKE receivers for the Direct Sequence---Ultra Wideband (DS-UWB) with considering the accuracy of channel estimation in a multipath channel. As RAKE receivers for DS-UWB, we consider the maximal-ratio combining (MRC)-RAKE, the minimum mean square error (MMSE)-RAKE, and the MRC-RAKE-Equalizer that is the MRC-RAKE followed by a liner equalizer. Generally, if the channel estimation is perfect, as the number of fingers or taps increases, the performance of each receiver is improved, however the computational complexity of each receiver increases. In practice, the channel estimation is not perfect. The channel estimation error makes their performances degraded. Therefore, the performances of the RAKE receivers depend on the accuracy of channel estimation. Consequently, we evaluate the computational complexities and the Bit Error Rates (BERs) of MRC-RAKE, MMSE-RAKE, and MRC-RAKE-Equalizer with considering the accuracy of channel estimation for DS-UWB. We show that the accuracy of channel estimation affects the BER of each receiver significantly. We also show that when the accuracy of channel estimation is high, MRC-RAKE-Equalizer can achieve the better BER than MMSE-RAKE with less computational complexity, while MMSE-RAKE can achieve the better BER than MRC-RAKE-Equalizer when the accuracy of channel estimation is low.

This paper discusses the IVC (Inter Vehicle Communication) system using the UWB (Ultra Wideband) radar. DSUWB (Direct Sequence - UWB) signal is used for this IVC system because it has CDMA (Code Division Multiple Access) Capability. However, there is the near-far problem due to difference of signal power from each vehicles, it becomes the cause of degradation of communication characteristics and detection accuracy of the signal. In this paper, we propose the iterative detection system using the SIC (Successive Interference Cancellation) to improve detection rate of the signal and the bit error rate (BER) performance. The signals except the desired signal detected by the SIC is subtracted from the original received signal. As the result, the performance was improved.

In previous works, the performance of DS-UWB (Direct Sequence- Ultra Wide Band) systems in a multiuser scenario with binary pulse amplitude modulation has been studied. In most of these works, independent identically distributed (i.i.d) random sequences have been considered and no optimization of the DS-UWB performance with respect to the choice of spreading sequences has been done. In this paper, we investigate an analysis of multi-user interference (MUI) term in three different families of traditional spreading sequences; i.i.d, Gold and Kasami sequences on Rayleigh and AWGN (additive white gaussian noise) channel. Then, we evaluate the bit error rate (BER) performance of conventional receiver on both channels to confirm the results found about MUI.

We consider a single user direct sequence impulse radio (DS-IR) system operating with a QPSK constellation over a deterministic, frequency selective channel and affected by additive white Gaussian noise (AWGN). We present a method to obtain a fast and accurate estimation of the symbol error rate (SER) when the receiver is a correlation receiver with perfect synchronization and channel knowledge. The method is based on the estimation of the Inter Symbol Interference (ISI) distribution by means of the characteristic function (CF) approach. The results also apply to direct sequence ultra wideband (DS-UWB) modulation since it is a special case of DS-IR. The accuracy of the method is verified by comparing the SER prediction with that obtained by means of Monte Carlo (MC) simulation.

In this paper, the performance of parallel interference cancellation (PIC) multiuser detector in orthogonal frequency division multiple access (OFDMA) mobile communication systems is investigated. In multiuser systems, the multi-user interference (MUI) degraded the system performance, especially in near-far effect environments. The PIC scheme is proposed to reduce the MUIs and to improve the bit error rate (BER) performance for uplink OFDMA systems. Simulation results show that under the near far problems for both block sub carrier assignment scheme (BCAS) and block-interleaved sub carrier assignment scheme (ICAS), the PIC scheme can improve the BER performance for all users.

To achieve high system capacity over frequency-selective fading channel, multi-carrier code-division-multiple-access (MC-CDMA) system with spatial diversity using space-time block coding (STBC) is considered. We present a subspace-based semi-blind channel estimation method under multiuser environment to resolve the inherent scalar ambiguity when blind estimation technique is used. Mean-square-error (MSE) expression for the proposed channel estimation technique is derived. Bit-error-rate (BER) when using linear zero-forcing (ZF) and minimum-mean-square-error (MMSE) multiuser detection techniques taking the channel estimation error into consideration are obtained through simulation. The correctness of the BERs is further verified through estimating the signal-to-interference and noise-ratio (SINR) at the multiuser detectors.

Multi-user detection (MUD) techniques are applied to the GPS interference suppression/rejection problem, such that recovery of GPS satellite signals out of an environment contaminated with one or more correlated interference sources is afforded. In modeling the narrowband digital interference as a set of multiple users it is shown that recovery is possible via any of several MUD algorithms, including the conventional detector, the decorrelating detector, the optimum linear detector, and the minimum mean square error (MMSE) detector. The relationship between the underlying structure of the GPS symbol (C/A code) and the performance of these detectors is studied such that bit error rate (BER) and signal-to-interference ratio (SIR) are developed analytically.

In the wireless communication systems, the classic Multi-User Detection (MUD) techniques such as the Minimum Mean Square Error (MMSE) detector have some limitations and imperfections due to Multi-Access Interference (MAI) especially in overloaded scenarios when the number of users is more than the number of receiving antennas. The optimal Maximum Likelihood (ML) detector gives an excellent result to estimate the transmitted data but suffers from a computational complexity that grows exponentially with the number of users. In this paper, we propose a new metaheuristic approach for multiuser detection based on Honey Bees Mating Optimisation (HBMO) hybridised with Tabu Search (TS) for an uplink Space Division Multiple Access-Orthogonal Frequency Division Multiplexing (SDMA-OFDM) system in a flat Rayleigh fading channel. Indeed, the HBMO algorithm provides a good estimation for TS while exploring the largest regions, while the TS algorithm uses this estimation to find the best solution of the problem. The simulation results show that the proposed algorithm HBMO-TS-MUD provides the best trade-off between performance and computational complexity comparing to the conventional detector and the other MUD detectors proposed as Genetic Algorithm hybridised with the Tabu Search (GA-TS).

In this contribution a novel invasive weed optimization (IWO) based multi user detector (MUD) aided time-hopping ultra-wide band (TH-UWB) system has been investigated in the indoor channel model. In this approach, the IWO based MUD employs the output of the Rake receiver as its initial value to search for the best solution which results on a formulated optimization mechanism. By taking advantage of the heuristic values and the collective intelligence of IWO technique, the proposed detector offers almost the same bit error rate (BER) performance as the full-search-based optimum multi-user detector does, while greatly reducing the potentially computational complexity. The good behavior of the proposed approach is demonstrated by means of comparisons in terms of BER performance and implementation complexity with the classical Rake receiver and different multi-user receivers previously proposed in the literature of this subject. Simulation results have been provided to examine the evolutionary behavior and the detection performance of the proposed IWO based MUD in both the additive white Gaussian noise (AWGN) and the multi-path fading channel.

Ultra wideband (UWB) radio is a promising technology for short range wireless communications. It can be used for both high rate and low rate transmissions. High data rate can be achieved by using multiband (MB)-UWB approach whereas low data rate with robust system performance can be obtained by employing time hopping (TH)-UWB radio systems Majhi et al. (2006); Win & Scholtz (1998a). Nowadays, applications of UWB are spreading to various fields such as vehicle communications, wireless sensor networks, ad hoc wireless networks, and controller area networks. The most of the systems require low to moderate (1 kbs-100 mbs) data rates with an acceptable implementation cost. However, due to the presence of fast Fourier transform (FFT) and inverse FFT (IFFT), MB-UWB may not be a cost effective procedure for low data rate systems. Therefore, one needs an efficient system which adaptively changes the data rate from low to moderate with robust system performance. TH-UWB with OOK-PSM modulation provides low data rate with robust system performance Majhi, Madhukumar, Premkumar & Richardson (2008). However, it is possible to scale the TH-UWB radio system for low to moderate data rates by incorporating higher level modulation schemes with an adaptive method. For TH-UWB systems, various M-ary modulation schemes such as pulse positionmodulation (PPM), pulse amplitude modulation (PAM), pulse shape modulation (PSM), and their combined forms have been proposed to improve data rates and system performance with low complexities Bin et al. (2003); Durisi & Benedetto (2003); Ghavami et al. (2002); Michell et al. (2003); Usuda et al. (2004). However, due to the increase of inter symbol interference (ISI) in the presence of multipath channel, M-ary PPM or M-ary orthogonal PPM (OPPM) are not effective for TH-UWB systems with RAKE reception when M is high Foerster (2003); Win & Scholtz (1998b). High-level M-ary PAM is rarely used in short range and low power consumption communications systems Guvenc & Arslan (2003). This is because that the Euclidian distances between constellations become small with increase in M. Due to its robustness against ISI and multiple access interference (MAI), pulse-based modulation such as PSM has become an interesting research topic in TH-UWB, direct sequence UWB (DS-UWB) and transmitted referenceUWB (TR-UWB) radio systemsChu M de Abrue et al. (2003); Gezici et al. (2006); Hwang et al. (2007); Kim & Womack (2007); Parr et al. (2003). However, high-level M-ary PSM cannot be used due to the limited auto correlation properties 2

One of the most crucial challenges in large-scale quantum communication systems is how to simultaneously transmit quantum information among multiple users via a common channel. In this paper, a novel non-orthogonal iterative quantum multiuser communication system is proposed. Based on the beam splitter network (BSN), we combine the independent quantum-state signals of different users into a single transmission channel. Furthermore, using photon-number-resolving detectors (PNRDs) based quantum adaptive feedback positive operator valued measurement, a chip-interleaved quantum iterative parallel interference cancellation (Iter-PIC) multiuser detection is developed. From the simulation results, the proposed quantum multiuser communication system can easily achieve 10e-7 bit error rate (BER) performance at 42 photons per bit for 6 users transmitting simultaneously. Also, from the extrinsic information transfer trajectories (EXIT) analysis results, this quantum chip interleaved Iter-PIC system is verified to have robust and fast convergence property in tough conditions, e.g. extra low receiving signal energy and quantum mode mismatch. Moreover, we show that the throughput of proposed quantum Iter-PIC system is 66.7% higher than that of the existing quantum wavelength division multiple access (q-WDMA) communication systems.

Background/Objectives: Tremendous growth in the mobile communication services in this technology driven era has made possible for the people to exchange information (data, voice or image) with each other while they are on the move. These wireless systems have brought a revolution in the current market for their high data rates and performance enhanced features. Methods/Statistical Analysis: One of the key issues affecting the performance of a wireless channel is the random variations in the signal strength which may be resulted due to some obstructions like buildings, trees, etc. or due to the movement of the mobile user. This leads to stochastic behavior of the radio channel.. A highly faded Two-Wave with Diffuse Power (TWDP) environment is discussed along with hybrid diversity combining technique. The effectiveness of this scheme is further evaluated by analyzing the system performance in terms of Bit Error Rate (BER) vs Signal to Noise Ratio (SNR). Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) modulation techniques were employed. Findings: It has been shown clearly that TWDP forms the poorer link when compared with other fading channels as BER is higher in this case. Moreover, TWDP fading environment can serve as the worst case scenario in wireless communication system. Also it has been shown as the diversity order increases system’s performance is improved in terms of BER and reduction in SNR requirement to achieve a constant BER value. Application/Improvement: This paper presents the need to obtain a clear perception of channel characteristics and to model a system for combating fading and improving the system performance by considering a TWDP fading channel instead of Rayleigh channel while designing a wireless communication system in worst channel conditions..

This paper proposes a multi-code interference (MCI) cancellation scheme employing multi-user detection (MUD) techniques for VSF-OFCDM system. The MCI cancellation structure is composed of minimum mean square error (MMSE) multi-user detector as the time domain MUD (TMUD) and parallel interference cancellation multi-user detector (PIC- MUD) as the frequency domain MUD (FMUD), i.e., TFMUD. Simulation results show that the TFMUD detector is more robust to different channel conditions and system parameters than the conventional detector.