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On the Design of Channel Shortening Demodulators for Iterative Receivers in Linear Vector Channels

Hu, Sha LU and Rusek, Fredrik LU (2015) In IEEE Transactions on Information Theory
Abstract
We consider the problem of designing demodulators for linear vector channels with memory that use reduced-size trellis descriptions for the received signal. We assume an overall iterative receiver, and use interference cancellation (IC) based on the soft information provided by the outer decoder, to mitigate the parts of the signal that are not covered by the reduced-size trellis description. In order to reach a trellis description, a linear filter is applied as front-end to compress the signal structure into a small trellis. This process requires three parameters to be designed: (i) the front-end filter, (ii) the feedback filter through which the IC is done, and (iii) a target response which specifies the trellis. Demodulators of this... (More)
We consider the problem of designing demodulators for linear vector channels with memory that use reduced-size trellis descriptions for the received signal. We assume an overall iterative receiver, and use interference cancellation (IC) based on the soft information provided by the outer decoder, to mitigate the parts of the signal that are not covered by the reduced-size trellis description. In order to reach a trellis description, a linear filter is applied as front-end to compress the signal structure into a small trellis. This process requires three parameters to be designed: (i) the front-end filter, (ii) the feedback filter through which the IC is done, and (iii) a target response which specifies the trellis. Demodulators of this form have been studied before under then name channel shortening (CS), but the interplay between CS, IC and the trellis-search process has not been adequately addressed in the literature. In this paper, we analyze two types of CS demodulators that are based on the Forney and Ungerboeck detection models, respectively. The parameters are jointly optimized based on a generalized mutual information (GMI) function. We also introduce a third type of CS demodulator that is in general suboptimal, but has closed-form solutions. Moreover, signal to noise ratio (SNR) asymptotic properties are analyzed and we show that the third CS demodulator asymptotically converges to the optimal CS demodulator in the sense of GMI-maximization. (Less)
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Contribution to journal
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submitted
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IEEE Transactions on Information Theory
publisher
IEEE--Institute of Electrical and Electronics Engineers Inc.
ISSN
0018-9448
language
English
LU publication?
yes
id
5ac36030-4b95-4c5c-a2a6-7fcca6971d35
date added to LUP
2017-08-25 16:36:01
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@article{5ac36030-4b95-4c5c-a2a6-7fcca6971d35,
  abstract     = {We consider the problem of designing demodulators for linear vector channels with memory that use reduced-size trellis descriptions for the received signal. We assume an overall iterative receiver, and use interference cancellation (IC) based on the soft information provided by the outer decoder, to mitigate the parts of the signal that are not covered by the reduced-size trellis description. In order to reach a trellis description, a linear filter is applied as front-end to compress the signal structure into a small trellis. This process requires three parameters to be designed: (i) the front-end filter, (ii) the feedback filter through which the IC is done, and (iii) a target response which specifies the trellis. Demodulators of this form have been studied before under then name channel shortening (CS), but the interplay between CS, IC and the trellis-search process has not been adequately addressed in the literature. In this paper, we analyze two types of CS demodulators that are based on the Forney and Ungerboeck detection models, respectively. The parameters are jointly optimized based on a generalized mutual information (GMI) function. We also introduce a third type of CS demodulator that is in general suboptimal, but has closed-form solutions. Moreover, signal to noise ratio (SNR) asymptotic properties are analyzed and we show that the third CS demodulator asymptotically converges to the optimal CS demodulator in the sense of GMI-maximization.},
  author       = {Hu, Sha and Rusek, Fredrik},
  issn         = {0018-9448},
  language     = {eng},
  publisher    = {IEEE--Institute of Electrical and Electronics Engineers Inc.},
  series       = {IEEE Transactions on Information Theory},
  title        = {On the Design of Channel Shortening Demodulators for Iterative Receivers in Linear Vector Channels},
  year         = {2015},
}