A. L. Swindlehurst, S. Daas, and J. Yang, "Analysis of a decision directed beamformer," IEEE Trans. on Signal Processing, vol. 43, pp. 292092.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... the last years, such as: the Temporal Reference Beamforming (TRB) 10] which implies a loss of spectral and channel bandwidth efficiency due to the transmission of the reference signal) possibly combined with a decision directed approach, which regenerates the reference signal at the receiver [11]. More sophisticated methods have been devised without the need of side information, such as [12] where the steering vector of the desired user is estimated using a subtraction of two matrices in which only the desired component survives; 13] in which a phased array is used after the MAT has ....

....utilization due to the transmission of the training sequence. During the transmission of the data bits, a decision directed approach can be used to continue adapting the beamformer. It basically exploits the finite alphabet restoral property to use the decided symbols as a training sequence [11]. The structure of this algorithm for a DS CDMA system is depicted in Figure 1, where the decided symbols are spread again to be used as a reference at a chip level. It is important to note that this method requires PN synchronization. 3. SELF REFERENCE BEAMFORMER The self reference beamformer ....

A. L. Swindlehurst, S. Daas, and J. Yang, "Analysis of a decision directed beamformer," IEEE Trans. on Signal Processing, vol. 43, pp. 292092.

....PROCESSING, VOL. 48, NO. 11, NOVEMBER 2000 reached. The only truly optimal algorithm is pure enumeration over all possible , which is exponential in the product and, hence, impractical. Concluding this section, note that a decision directed MMSE FA separation approach has been pursued in [7]; it requires side information for initialization purposes, and its convergence analysis is asymptotic in . III. PROPOSED ALGORITHM The core idea behind the novel algorithm proposed herein can be summarized as follows. Instead of updating suboptimally as a whole (like ILSP) or optimally one ....

A. Swindlehurst, S. Daas, and J. Yang, "Analysis of a decision directed beamformer," IEEE Trans. Signal Processing, vol. 43, pp. 2920--2927, Dec. 1995.

....as those encountered in wireless communications, these signal properties are often known with great accuracy, leading to robust algorithms. Some of the most representative deterministic properties, Constant Modulus (CM) 2, 3] and Finite Alphabet (FA) exploited by decision directed methods [4]) are properties exhibited by many modulation schemes. Other Int. J. Electron. Commun. AE U) 54 (2000) No. 5, 267 276 1434 8411 2000 54 5 267 15.00 0 268 D. P erez Palomar, M. N ajar, M. A. Lagunas: Self reference Spatial Diversity Processing for Spread Spectrum Communications signals, known ....

Swindlehurst, A. L.; Daas, S.; Yang, J.: Analysis of a decision directed beamformer. IEEE Trans. on Signal Processing 43 (December 1995), 2920--2927.

....is generally ill posed, and is only considered in the context of separating orthogonal or Chapter 1. Introduction 10 pseudo orthogonal signals (CDMA) 24] Most of the techniques in this class use multiple antennas in combination with the constant modulus [25, 26] or finite alphabet property [27, 28, 29] to separate multiple signals transmitted over a coherent multipath (memoryless) channel. The MIMO VC problem for general multipath channels has not received much attention. An adaptive antenna combining and equalizing algorithm is proposed in [30] and the algorithms proposed in [27] are extended ....

....array response vectors is small. In contrast, the data matrix X in (3.3.3) becomes poorly conditioned for high SNR s. The MMSE algorithm is computationally less expensive. However, we have found the performance of the ML algorithm to be more favorable in a blind multiple signal scenario. In [29], a decision directed technique for digital signals using both the MMSE and ML beamformers (latter one is similar to ILSP) is proposed. It is assumed that a rough estimate of the signal of interest is available. It is shown that the asymptotic symbol error rate for the MMSE beamformer W = RSXR ....

A. Swindlehurst, S. Daas, and J. Yang. Analysis of a Decision Directed Beamformer. Submitted to IEEE Trans. on Signal Processing, October 1993.

.... has been exploited in decision directed adaptive algorithms [11 14] and also in joint channel estimation and sequence detection [15, 16] Several iterative algorithms for the separation of instantaneous superpositions ( I MIMO ) of finite alphabet signals were originally proposed by Talwar et al. [17 19]; an algorithm based on expectation maximization appeared in [20] The two properties are in fact readily combined into one algorithm to solve the FIR MIMO problem, as was discovered independently by Liu and Xu [21, 22] and the present authors [1 3] Related work on blind FIR MIMO identification ....

.... noise level, ILSE and ILSP usually converge to a fixed point in less than 5 10 iterations [17] As mentioned in the introduction, several other I MIMO source separation algorithms are described in the literature, some based on different properties such as source independence or constant modulus [19, 20, 36 39]. Alternatively, we can minimize the MMSE criterion min T full rank;SW kS TY k 2 ; 15) which essentially fits the subspace Y to a FA matrix S. An iterative algorithm to solve this problem is called Iterative Least Squares with Subspace Fitting (ILSF) and is listed in table 1. It is very ....

A. Swindlehurst, S. Daas, and J.Yang, "Analysis of a Decision Directed Beamformer," Submitted to IEEE Trans. Signal Processing, October 1993.

....setting. In the recent past, several property restoral techniques have been developed which exploit the temporal structure of communication signals, while assuming no prior spatial knowledge. These techniques take advantage of signal properties such as constant modulus (CM) 9] discrete alphabet [10, 11], self coherence [12] and high order statistical properties [13, 14] In this paper, we propose a new property restoral approach that takes advantage of the discrete as well as the finite alphabet (FA) property of digital signals. Our approach is termed blind since it does not require any ....

....between array response vectors is small. In contrast, the data matrix X in (21) becomes poorly conditioned for high SNR s. The MMSE algorithm is computationally less expensive. However, we have found the performance of the ML algorithm to be more favorable in a blind multiple signal scenario. In [10], Swindlehurst et al. have proposed a decision directed technique for digital signals using both the MMSE and ML beamformers (similar to ILSP) assuming a rough estimate of the signal of interest is available. They have shown that the asymptotic symbol error rate for the MMSE beamformer W = R SX ....

A. Swindlehurst, S. Daas, and J.Yang. Analysis of a Decision Directed Beamformer. Submitted to IEEE Trans. on Signal Processing, October 1993.

.... been exploited in decision directed adaptive algorithms [10 13] and also in joint channel estimation and sequence detection [14, 15] Several iterative algorithms for the separation of instantaneous superpositions ( I MIMO ) 2 of finite alphabet signals were originally proposed by Talwar et al. [16 18]; an algorithm based on expectation maximization appeared in [19] The two properties are in fact readily combined into one algorithm to solve the FIR MIMO problem, as was discovered independently by Liu and Xu [20, 21] and the present authors [1, 2] Related work on blind FIR MIMO identification ....

.... noise level, ILSE and ILSP usually converge to a fixed point in less than 5 10 iterations [16] As mentioned in the introduction, several other I MIMO source separation algorithms are described in the literature, some based on different properties such as source independence or constant modulus [18, 19, 35 38]. Alternatively, we can minimize the MMSE criterion min T full rank;S W kS TY k 2 ; 16) which essentially fits the subspace Y to a FA matrix S. An iterative algorithm to solve this problem is called Iterative Least Squares with Subspace Fitting (ILSF) and is listed in table I. It is very ....

A. Swindlehurst, S. Daas, and J.Yang, "Analysis of a Decision Directed Beamformer," IEEE Tr. Signal Proc., vol. 43, pp. 2920--2927, Dec. 1995.

....substantial capacity increases over current wireless system implementations. In [2, 13, 28, 26, 31, 32] efficient use of the spatial dimension by employing antenna arrays at the base stations of wireless communication systems is explored. The up link problem has receive substantial attention [2, 26, 19, 20, 24] whereas the down link problem more recently has drawn interest [13, 28, 32] Of course, the hardware requirements are more demanding when employing antenna arrays with multiple receivers and transmitters, but this permits a sparser infrastructure and will often be more cost effective. In ....

....individual transmitted signals may be separated by exploiting the finite alphabet property. In [21] the detection is achieved by alternatively making symbol decisions (from an estimated channel) and then estimating the channel (based on a known symbol sequence) A similar concept is described in [20] where initial symbol decisions are used to reconstruct a reference signal which in turn is used to estimate the channel and so on. The problem of blind signal separation in this application is difficult although it may be relevant when there is large uncertainty surrounding the transmitted ....

A. Swindlehurst, S. Daas, and J. Yang. "Analysis of a Decision Directed Beamformer. IEEE Trans. on Sig. Proc., 43(12):2920--2927, December 1995.

....[6] or a combination thereof) In both cases, the co channel interference in the system is increased. Therefore, interference rejection capabilities can improve the capacity of the system. On the reverse link, several interference rejection methods based on spatial processing have been proposed [1, 4, 9, 10, 11]. On the forward link, interference rejection is more difficult in frequency division duplex (FDD) systems [6] The fading caused by local scattering around the terminal (or the base station) is observable in the reverse link but unobservable in the forward link since the fading processes are ....

A. Swindlehurst, S. Daas, and J. Yang, "Analysis of a Decision Directed Beamformer, IEEE Trans. on Sig. Proc., 43(12):2920--2927, December 1995.

....with the transmitted symbols. So, the averaged rotation angle is computed for the estimated symbols and used for compensation. We can also take advantage of the finite alphabet (FA) property after the symbol estimation. A decision directed (DD) post processing step is adopted here as proposed in [26]. After mapping the estimated symbol to the FA, we re calculate the filter WMSE = R y xx R xs dec which consequently produce a new signal estimate s 0 dec = W H MSE x. Iterations are conducted until s dec converges. The additional computation burden is slight as R y xx is already computed ....

A. L. Swindlehurst, S. Daas, and J. Yang, "Analysis of a decision directed beamformer," IEEE Trans. Signal Process., vol. 43, pp. 2920--2927, Dec. 1995.

....equal to or longer than the symbol period, then then channel is said to have memory and received copies of the same signal are incoherent. Blind equalization of memoryless channels reduces to separating co channel sources which are not corrupted by ISI (the instantaneous mixture problem) 1] 2] [3]. The present work is devoted to the more general problem of equalizing channels with memory. Recently, much work in the area of blind equalization has focused on channel identification by exploitation of the second order cyclostationary statistics of received data oversampled in space and or time ....

A. Swindlehurst, S. Daas, and J. Yang, ""Analysis of a Decision Directed Beamformer"," IEEE Trans. on Sig. Proc., vol. 43, pp. 2920--2927, December 1995.

....LS CMA method [7] and the CM factorization (CMF) approach [8] Finite alphabet (FA) signals Algorithms from this class assume that the sources transmit digital communications signals with known modulation. Of the available FA techniques, only the decision directed (DD) beamformer presented in [9] was implemented. Higher order statistics (HOS) A number of algorithms for blind source separation based on HOS have also been developed, but only the JADE algorithm of [10] was considered here. JADE assumes only that the signals are uncorrelated and non Gaussian, and uses the structure of the ....

A. Swindlehurst, S. Daas, and J. Yang, "Analysis of a Decision Directed Beamformer", IEEE Trans. on Sig. Proc., 43(12):2920--2927, December 1995.

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A. Swindlehurst, S. Daas, and J. Yang, "Analysis of a decision directed beamformer," IEEE Trans. Signal Proc., vol. 43, no. 12, pp. 2920--2927, Dec. 1995.

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