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A Decorrelating Multiuser Receiver for TransmitReference UWB Systems ” to appear
 in Signal Processing, Volume 1, Issue 3
, 2007
"... Abstract—Transmitreference (TR) is known as a realistic but low data rate candidate for ultrawideband (UWB) communication systems. This paper proposes a new TRUWB scheme that uses a decorrelating receiver to enable higher data rates with only a reasonably small increase in complexity while still ..."
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Abstract—Transmitreference (TR) is known as a realistic but low data rate candidate for ultrawideband (UWB) communication systems. This paper proposes a new TRUWB scheme that uses a decorrelating receiver to enable higher data rates with only a reasonably small increase in complexity while still maintaining the ease of synchronization of the original. Integrate and dump with oversampling is used to derive an approximate signal processing data model in a multiuser context. An iterative and a blind receiver algorithm are introduced and tested in simulations. Multiple reference delays are used to further improve the system performance similar to the role of multiple antennas in communication systems. The receiver’s complexity and other practical issues in transceiver design are also discussed. Index Terms—Impulse radio, receiver algorithm, signal processing, transmitreference, ultrawideband (UWB). I.
Signal processing model and receiver algorithms for a higher rate multiuser TRUWB communication system
 in subm. Proc. IEEE ICASSP, (Honolulu (HI)), IEEE
, 2007
"... Transmitreference (TR) schemes are commonly used only in low data rate ultrawideband (UWB) systems because of many restrictions on the pulse spacing, frame and symbol periods (should be longer than the channel length). This paper extends our previous research that tries to remove these restriction ..."
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Cited by 2 (1 self)
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Transmitreference (TR) schemes are commonly used only in low data rate ultrawideband (UWB) systems because of many restrictions on the pulse spacing, frame and symbol periods (should be longer than the channel length). This paper extends our previous research that tries to remove these restrictions to enable a higher data rate application in a multiuser context. Based on the fact that most UWB channels are highly uncorrelated, we can formulate a CMDAlike signal processing model for an asynchronous multiuser system. Blind and iterative algorithms are derived, of which the performances are compared and veri�ed in simulations. Index Terms — UWB, multiuser separation, transmitreference 1.
Quasiseparability and hierarchical quasiseparability in stochastic signal processing
 In Proc of IEEE Workshop on Statistical Signal Processing (SSP
, 2005
"... Sochastic signal processing has reached the age of ’array processing’, where the various properties of the relevant system matrix play a predominant role in the efficiency of the filtering or estimation algorithm. Classical is the Toeplitz structure, and structures that are derived from it such as ’ ..."
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Cited by 1 (0 self)
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Sochastic signal processing has reached the age of ’array processing’, where the various properties of the relevant system matrix play a predominant role in the efficiency of the filtering or estimation algorithm. Classical is the Toeplitz structure, and structures that are derived from it such as ’quasistationarity’. In this paper we focus on a different structure of equally great importance, namely ’quasiseparabilty’. We start out with an introduction to basic properties and algorithms, foremost of which is an extension of the square root algorithm known from Kalman filtering. Although extremely important and useful when applicable, in many applications the notion of quasiseparability has to be extended. We discuss two main classes of extensions,
EURASIP Journal on Wireless Communications and Networking 2004:1, 98–112 c ○ 2004 Hindawi Publishing Corporation Joint Performance Study of Channel Estimation and Multiuser Detection for Uplink LongCode CDMA Systems
, 2004
"... Although numerous channel estimation and multiuser detection approaches have appeared for longcode uplink CDMA systems, joint performance study of channel estimators and symbol detectors remains largely open. In this paper, we construct three typical symbollevel linear receivers upon existing chan ..."
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Although numerous channel estimation and multiuser detection approaches have appeared for longcode uplink CDMA systems, joint performance study of channel estimators and symbol detectors remains largely open. In this paper, we construct three typical symbollevel linear receivers upon existing channel estimation method, known as zeroforcing (ZF), minimum meansquareerror (MMSE), and RAKE receivers, for symbol detection. Since the channel estimation error is rippled to the linear receivers, performance of all receivers is thus jointly analyzed with the channel estimator from a perturbation perspective. Extensive simulation examples involving different communication environments demonstrate high consistency between our analysis and experimental results.
EURASIP Journal on Wireless Communications and Networking 2004:1, 113–122 c ○ 2004 Hindawi Publishing Corporation A LowComplexity Blind Multiuser Receiver for LongCode CDMA
, 2004
"... Receivers for longcode systems are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but have not been widely studied due to the apparent complexity of the inver ..."
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Receivers for longcode systems are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but have not been widely studied due to the apparent complexity of the inversion of a large code matrix. Tong, van der Veen Dewilde, and Sung (IEEE Tr. Signal Proc., 2003) derived a blind decorrelating RAKE receiver (DRR) and channel estimation algorithm for longcode CDMA systems, and showed how it can be efficiently implemented. In this paper, we continue on that work. We propose both singleuser and multiuser blind sourcechannel estimation algorithms by making use of an iterative estimation scheme initialized by the DRR. Simulation results show significant improvement, even in heavily loaded systems. Moreover, with an implementation based on timevarying system theory, the proposed algorithm can be implemented efficiently at a cost similar to the RAKE.
EURASIP Journal on Wireless Communications and Networking 2004:2, 322–334 c ○ 2004 Hindawi Publishing Corporation Blind Channel Estimation for SpaceTime Coded WCDMA
, 2004
"... A new blind channel estimation technique is proposed for spacetime coded wideband CDMA systems using aperiodic and possibly multirate spreading codes. Using a decorrelating front end, the received signal is projected onto a subspace from which channel parameters can be estimated up to a rotational ..."
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A new blind channel estimation technique is proposed for spacetime coded wideband CDMA systems using aperiodic and possibly multirate spreading codes. Using a decorrelating front end, the received signal is projected onto a subspace from which channel parameters can be estimated up to a rotational ambiguity. Exploiting the subspace structure of the WCDMA signaling and the orthogonality of the unitary spacetime codes, the proposed algorithm provides a blind channel estimate via least squares. A new identifiability condition is established under the assumption that the system is not heavily loaded. The mean square error of the estimated channel is compared with the CramérRao bound, and the bit error rate (BER) performance of the proposed algorithm is compared with that of differential schemes.
COMPUTATIONALLY EFFICIENT BLIND MMSE RECEIVERS FOR LONG CODE WCMDA USING TIMEVARYING SYSTEMS THEORY
"... Abstract: UMTS systems will employ longcode wideband CDMA modulation schemes. Receivers for this system are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but ..."
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Abstract: UMTS systems will employ longcode wideband CDMA modulation schemes. Receivers for this system are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but, until now, were considered as too complex, due to the inversion of a large code matrix. As is shown in this paper, the code matrix can be interpreted as a timevarying system. Efficient implementations are then possible by carrying out the inversion using timevarying state space theory, yielding a complexity comparable to that of the conventional RAKE receiver. Keywords: Longcode WCDMA, decorrelating RAKE receiver, MMSE receiver, timevarying system theory, computational structures 1.
COMPUTATIONAL STRUCTURES FOR BLIND LONGCODE WCDMA RECEIVERS
"... Longcode wideband CDMA receivers are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. To mitigate this problem, we propose computationally efficient decorrelating RAKE and MMSE receivers for the uplink of longcode CDMA sys ..."
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Longcode wideband CDMA receivers are for computational reasons usually based on simple matchedfilter techniques, and hence suffer from multiaccess interference. To mitigate this problem, we propose computationally efficient decorrelating RAKE and MMSE receivers for the uplink of longcode CDMA systems. The decorrelating matched filter eliminates multiaccess interference by code matrix inversion. Channel parameters and data symbols are then estimated jointly via rankone decompositions. The feasibility of the proposed schemes hinges upon their efficient implementation in terms of timevarying state space realizations, with a complexity comparable to that of the conventional RAKE receiver. 1.
Proceedings of SPSDARTS 2007 (the 2007 The third annual IEEE BENELUX/DSP Valley Signal Processing Symposium) SIGNAL PROCESSING FOR TRANSMITREFERENCE UWB
"... Transmitreference (TR) is known as a realistic but low data rate candidate for ultrawideband (UWB) communication systems. Higher data rates are possible but give rise to interpulse, interframe, and intersymbol interference, and thus require some form of equalization. In this paper, we discuss a su ..."
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Transmitreference (TR) is known as a realistic but low data rate candidate for ultrawideband (UWB) communication systems. Higher data rates are possible but give rise to interpulse, interframe, and intersymbol interference, and thus require some form of equalization. In this paper, we discuss a suitable receiver algorithm and its complexity, and derive the associated maximal data rate. 1.
Efficient Matrix Computations in Wideband Communications
"... Modern telecommunications put increasing demands on the efficient use of bandwidth in a channel. This is especially true in the upcoming wideband channels, where a large number of users are spread across the same large frequency band. There are two main techniques to achieve the spreading, one works ..."
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Modern telecommunications put increasing demands on the efficient use of bandwidth in a channel. This is especially true in the upcoming wideband channels, where a large number of users are spread across the same large frequency band. There are two main techniques to achieve the spreading, one works 'in the time domain' and uses randomized codes to characterize users. It is called 'Code Division Multiple Access ', and in the case of a wide band channel  WCDMA. The other works in the frequency domain. It is called OFDM and utilizes orthogonal sinusoidal waveforms as carriers. In this paper we concentrate on WCDMA and show how new methods from the field of timevarying system theory can be applied to achieve efficient algorithms for signal separation of individual users. In particular, the efficient computation of different kinds of pseudoinverses of a matrix with a jagged blockstructure appear to be the main algorithms needed and they can be achieved using a statespace representation of the original matrix and keeping the statespace representation throughout the computation.