Title :
On the Limitation of Linear MMSE Detection
Author :
Varanasi, Mahesh K. ; Mullis, Clifford T. ; Kapur, Ateet
Author_Institution :
Dept. of Electr. Eng., Colorado Univ., Boulder, CO
Abstract :
This correspondence highlights the performance limitation of linear minimum mean-squared error (mmse) detection in underdetermined vector Gaussian channels (as in overloaded code-division multiple-access (CDMA) systems) where the number of symbols (users) exceeds the signal space dimension (spread factor). It is shown that for such a simple receiver it is not possible to construct signal sets (or spreading codes) to even satisfy the basic requirement that every user´s symbol error probability decays exponentially as noise power vanishes. This result holds for arbitrary received energies, modulation schemes, and any strictly underdetermined system with a finite signal space dimension and a finite number of users
Keywords :
Gaussian channels; code division multiple access; error statistics; least mean squares methods; modulation; signal detection; CDMA; code-division multiple-access; error probability; finite signal space dimension; linear MMSE detection; minimum mean-squared error; modulation scheme; vector Gaussian channel; Digital signal processing; Extrapolation; Finite impulse response filter; Interpolation; Least squares methods; Process control; Rivers; Signal detection; Signal processing; Smoothing methods; Code-division multiple-access (CDMA); Gaussian multiple-access channels; minimum mean square error (mmse) detection; multiuser detection; signal design;
Journal_Title :
Information Theory, IEEE Transactions on
DOI :
10.1109/TIT.2006.880039
