M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels," IEEE Trans. Inform. Theory, vol. 39, pp. 157--176, Jan. 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....filter multiplied by (assuming coherent reception) is (14) where and are the th elements of the inverse transforms of and , respectively. Since the decorrelating filter is noncausal, it is necessary to approximate it by appropriate long delay and truncation of the noncausal part in practice [5]. First, we assume that no channel state information (CSI) is available. Let be the set of all allowable paths in the trellis code. Then, the th user s metric of at epoch is (15) where and is the index of the signature waveform during the th symbol of the th path of the th user. Note that, ....

....or may not represent a real situation, we can get the lower and upper bounds of the performance from the analyses. A. The Asymptotic Diversity Order (ADO) and Asymptotic Gain (AG) As a measure of the performance of multiuser receivers, the asymptotic efficiency (AE) has been widely used [1] [5]. In coded systems, however, the asymptotic efficiency cannot be used directly since it does not reflect the effect of coding gain. Furthermore, coded systems with interleaving can provide a form of diversity in fading channels. Therefore, it is reasonable to measure the asymptotic performance of ....

M. Varanasi, "Noncoherent detection in asynchronous multiuser channels, " IEEE Trans. Inform. Theory, vol. 39, pp. 157--176, Jan. 1993.

....however, its performance is usually poorer than that of coherent reception. In the context of multiuser detection, the use of the DPSK is limited to the detectors which do not require channel estimation for the MAI reconstruction. For example, in our study, possible choices are the decorrelator [31], the SIC MF, and the PIC. The output of the decorrelator is identical to that of a single user system with enhanced noise. Therefore, the decision process does not involve interference reconstruction. The SIC MF and the PIC reconstruct the MAI, but they use the matched filter outputs and do not ....

M. Varanasi, "Noncoherent Detection in Asynchronous Multiuser Channels," IEEE Transactions on Information Theory, Vol. IT-39, No. 1, Jan. 1993, pp. 156-176.

....users and therefore it is undesirable for large K . To avoid the large computation, various efforts in designing sub optimum multiuser detection have been conducted, such as the decorrelating detector [6] multi stage detector [7] neural networks based detector [8] optimal bilinear detector [9], successive MAI cancellation [10] linear canceler [11] expectation maximization (EM) based iterative receiver [12] and adaptive approaches [13, 14] A comprehensive review of the recent multi user detectors can be found in the literature [15] Studies indicate that although these multiuser ....

M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels," IEEE Trans. Inform. Theo., vol. IT-39, pp. 157--176, Jan. 1993.

....receiver. Even with perfect power control, the performance can be improved by using a more sophisticated receiver. Among the near far resistant receivers, the decorrelating receiver [1 3] has gained considerable interest. The decorrelating receiver was generalized to non coherent channels in [4, 5]. Other proposed techniques for multi user detection are interference estimation and cancellation schemes [6] and multistage detectors [7] These structures are all dependent on substantial sideinformation, e.g. the number of users, each user s code waveform, received power, carrier phase and ....

M. K. Varanasi, "Noncoherent Detection in Asynchronous Multiuser Channels" IEEE Transactions on Information Theory, vol. 39, pp. 157-- 176, January 1993.

....= W . This detector is denoted the W MMSE I detector in the paper. 3.5 Differential Coding Previously the phases of the users of interest were assumed to be known. It is however a difficult task to estimate the phases for all the users. Another approach is to use differential coding. See e.g. [6]. A Gamma1 and a 1 is transmitted as a shift of the phase by , 0 radians, respectively. This is easily done when the data u k (m) 2 f Gamma1; 1g. Then the sent bits are obtained as d k (m) d k (m Gamma 1)u k (m) On the receiver side the data is estimated as u k (m) sgn(Re(y k (m)y ....

Mahesh K. Varanasi. "Noncoherent Detection in Asynchronous Multiuser Channels". IEEE Transactions on Information Theory, vol. 39, no. 1, pp. 157--176, January 1993.

....users and therefore it is undesirable for large K. To avoid such large computation, various efforts in designing sub optimum multiuser detection have been conducted, such as the decorrelating detector [5] multi stage detector [6] neural networks based detector [7] optimal bilinear detector [8], successive MAI cancellation [9] linear canceller [10] expectation maximization (EM) based iterative receiver [11] and adaptive approaches [12, 13] A comprehensive review of the recent multi user detectors can be found in the literature [14] Studies indicate that although these multiuser ....

M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels," IEEE Trans. Inform. Theo., vol. IT-39, pp. 157--176, Jan. 1993.

....receiver. Even with perfect power control, the performance can be improved by using a more sophisticated receiver. Among the near far resistant receivers, the decorrelating receiver [1 3] has gained considerable interest. The decorrelating receiver was generalized to non coherent channels in [4, 5]. Other proposed techniques for multi user detection are interference estimation and cancellation schemes [6] and multistage detectors [7] These structures are all dependent on substantial side information, e.g. the number of users, each user s code waveform, received power, carrier phase and ....

M. K. Varanasi, "Noncoherent Detection in Asynchronous Multiuser Channels" IEEE Transactions on Information Theory, vol. 39, pp. 157--176, January 1993.

....When the nonlinearly modulated symbols consist of linearly modulated subsymbols, total decorrelation may be viewed as separate decorrelation for each subsymbol. With this interpretation, total decorrelation had previously been applied to the specific case of differentially modulated systems in [9]: each differentially modulated symbol can be viewed as nonlinear modulation based on two linearly modulated subsymbols, and total decorrelation simply consists of applying decorrelation to each of these subsymbols prior to differential demodulation. The user subspaces in this case are of (small) ....

....2 = E b , i = 1; 2. By applying (13) and recognizing that in this case U j = u 1 and U j 0 = u 2 , we obtain the standard binary noncoherent detector i = arg max i=1;2 ju H i rj 2 (15) As a second example, consider noncoherent detection for a multiuser channel with DPSK modulation [9]. Example 2: Multiuser DPSK channel) Consider a linearly modulated synchronous CDMA in which the N dimensional received vector in the nth symbol interval is y[n] K X k=1 A k [n]t k [n]s k w 0 [n] where A k [n] is the (typically time varying) complex amplitude of user k, t k [n] is the ....

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M. K. Varanasi, "Noncoherent Detection in Asynchronous Multiuser Channels," IEEE Transactions on Information Theory, vol. 39, no. 1, pp. 157-176, December 1993.

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M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels," IEEE Trans. Inform. Theory, vol. 39, pp. 157--176, Jan. 1993.

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M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels," IEEE Trans. Inform. Theory, vol. 39, pp. 157--176, Jan. 1993.

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M.K. Varanasi, "Noncoherent Detection in Asynchronous Multiuser Channels," IEEE Trans. Inform. Theory, vol. 39, no. 1, 1993, pp. 157--176.

....channel by the standard Gaussian approximation; 10] considers the synchronous problem and derives the jointly optimum detector and various sub optimum approaches for the case of known envelopes but contains no results on performance analysis. Under the white Gaussian noise background regime, [11,12] derive the optimum (bi ) linear multiuser detectors for the synchronous and asynchronous channel, respectively, and [13, 14] introduce multistage receivers for these settings. II. THE GENERALIZED DIVERSITY RAYLEIGH FADING (GDRF) CHANNEL In this section the discrete time model for the multiuser ....

M. K. Varanasi, "Noncoherent detection in asynchronous multiuser channels, " IEEE Trans. Inform. Theory, vol. 39, no. 1, pp. 157--176, Jan. 1993.

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