A soft iterative multisensor array receiver for coded multiuser wideband code-division multiple-access wireless uplink channels is proposed. Such channels are typically both frequeney and time-selective, A new equival...
详细信息
A soft iterative multisensor array receiver for coded multiuser wideband code-division multiple-access wireless uplink channels is proposed. Such channels are typically both frequeney and time-selective, A new equivalent discrete-time synchronous representation is used to model asynchronous multiuser dispersive channels that employ, in general, random spreading. The proposed scheme suppresses multiuser interference over a wide range of user signal powers, by iteratively exchanging soft information between a minimum mean-square-error (MMSE) multiuser demodulator and a bank of single-user decoders, feeding back the outputs of the latter to aid in soft multiuser multisensor MMSE-Rake demodulation and subtractive interference cancellation, in the second and subsequent iterations, It displays near-far resistance since it behaves like a successive interference subtracter across iterations. The array responses are obtained via a multipass estimation scheme that uses both (temporal) pilot symbols and soft estimates fed back from the decoders to effectively provide multisymbol pilot signals and thence successively refined estimates with increasing iterations, while seeking neither to rely on the array geometry nor to estimate the directions from which users' signals arrive at the receiver. Simulation studies indicate that this scheme performs close to the single-user case with a two-sensor receiver array, and perfect channel state information, after four iterations;alternatively, it allows significantly increased user capacity compared with conventional receivers, and suffers only a modest loss with estimated array responses.
This paper presents a simple two-branch transmit diversity scheme. Using two transmit antennas and one receive antenna the scheme provides the same diversity order as maximal-ratio receiver combining (MRRC) with one t...
详细信息
This paper presents a simple two-branch transmit diversity scheme. Using two transmit antennas and one receive antenna the scheme provides the same diversity order as maximal-ratio receiver combining (MRRC) with one transmit antenna, and two receive antennas. It is also shown that the scheme may easily be generalized to two transmit antennas and M receive antennas to provide a diversity order of 2M. The new scheme does not require any bandwidth expansion any feedback from the receiver to the transmitter and its computation complexity is similar to MRRC.
This paper presents a robust technique for broadband beamforming in the presence of pointing error. Based on the fact that the output power of an optimized beamformer achieves a maximum if the steering vector coincide...
详细信息
This paper presents a robust technique for broadband beamforming in the presence of pointing error. Based on the fact that the output power of an optimized beamformer achieves a maximum if the steering vector coincides with that of the desired signal, the technique iteratively searches for the correct 'steering vector' of a broadband source with a known bandwidth. By approximating the 'steering vector' by its first order Taylor series expansion in terms of the steering angle, the maximization process reduces to a one-dimensional optimization problem. Numerical results are presented to illustrate the performance achievable.
This paper presents an alternative constraint system for implementing the quadratically constrained broadband beamformers. The resulting system involves a linear equality constraint and a quadratic inequality constrai...
详细信息
This paper presents an alternative constraint system for implementing the quadratically constrained broadband beamformers. The resulting system involves a linear equality constraint and a quadratic inequality constraint. It offers some savings in the computation load as compared to the original problem in the sense that the quadratic constraint will be used as and when necessary. The relationship that the new constraint system has to other constraint systems is explored. It is shown that the constraint system with linear constraint is equivalent to the CCMP method and the constraint system with linear and quadratic constraints is equivalent to the improved CCMP method. The alternative formulation provides several insights into the CCMP method and the improved CCMP method. In dieser Arbeit wird ein alternatives System von Nebenbedingungen für die Implementierung des formulierten Breitband-Beamformers mit quadratischen Nebenbedingungen vorgestellt. Das sich ergebende System mit Nebenbedingungen kann als die Methode der Leistungsminimierung mit Korrelationsnebenbedingungen und deren berichteten Verbesserungen interpretiert werden. Um den Rechenaufwand für die Berechnung des optimalen Gewichtsvektors zu reduzieren, werden numerische Techniken dargelegt, die auf einer Matrixfaktorisierung basieren. Anschließend approximieren wir die quadratische Nebenbedingung durch einen Satz von linearen Nebenbedingungen. Die Verwendung von linearen Nebenbedingungen ist sehr attraktiv, da sie den Rechenaufwand für die Bestimmung des optimalen Gewichtsvektors reduziert. Cet article présente un système avec choix de contrainte pour la formation de voie large bande à contrainte quadratique. Le système résultant implique une contrainte linéaire sous forme d'égalité et une contrainte quadratique sous forme d'inégalité. Cela permet de réduire la charge de calcul par rapport au problème original dans le sens où la contrainte quadratique n'est utilisée que quand elle est nécessaire. Le lien en
This paper presents a technique for designing a narrowband beamformer which is robust against array amplitude and phase perturbations. The approach taken in the paper is to constrain the mean-square-error between the ...
详细信息
This paper presents a technique for designing a narrowband beamformer which is robust against array amplitude and phase perturbations. The approach taken in the paper is to constrain the mean-square-error between the desired unity response and the response of the beamformer over variation in amplitude and phase to be less than or equal to a small quantity and obtain a quadratic constraint on the weight vector. The optimal weight is then obtained by minimizing the beamformer mean output power subject to the quadratic constraint. Subsequently, a linear constraint and a norm constraint are used to approximate the effect of the quadratic constraint. Based on the latter approximation, an alternative beamforming structure termed as partitioned beamformer is presented. The equivalent optimal vector for the partitioned beamformer has an interesting geometrical interpretation in the sense that signal suppression and the increase of length of the weighting vector of the beamformer are related. Numerical results are presented to illustrate the performance achievable. Dieser Beitrag stellt eine Entwurfsmethode für Schmalband-Beamformer,die robust bezüglich Amplituden-und Phasenfehlern des Empfängers sind, vor. Das hier benutze Verfahren zwingt den mittleren quadratischen Fehler zwischen der gewünschten Einheitssprungantwort und der Antwort des Beamformers durch Variation der Amplitude und Phase unter eine kleine Schwelle und liefert eine quadratische Nebenbedingung für den Gewichtsvektor. Den optimalen Gewichtsvektor erhält man dann durch Minimieren der mittleren Beamformer-Ausgangsleistung unter Berücksichtingung der quadratischen Nebenbedingungen. Anschließend approximieren wir die quadratische Nebenbedingung durch eine lineare und eine Norm-Nebenbedingung. Basierend auf dieser Approximation wird eine mit “aufgeteilter Beamformer” bezeichnete alternative Beamforming-Struktur präsentiert. Der äquivalente optimale Vektor für den aufgeteilten Beamformer besitzt eine interessante
暂无评论