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PN sequence blind estimation in multiuser DS‐CDMA systems with multipath channels based on successive subspace scheme
Author(s) -
Mirzadeh Sarcheshmeh Hossein,
Khaleghi Bizaki Hossein,
Alizadeh Sajjad
Publication year - 2018
Publication title -
international journal of communication systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.344
H-Index - 49
eISSN - 1099-1131
pISSN - 1074-5351
DOI - 10.1002/dac.3591
Subject(s) - computer science , multipath propagation , algorithm , code division multiple access , finite impulse response , channel (broadcasting) , subspace topology , additive white gaussian noise , spread spectrum , sequence (biology) , telecommunications , artificial intelligence , biology , genetics
Summary In this paper, we proposed a new method based on expanding subspace algorithm and finite alphabet characteristics, for blind estimation of the users' spreading sequences in the multiuser direct sequence code division multiple access system in the presence of the multipath channels. In the proposed scheme, we show that the estimation of the users' overall channels in the direct sequence code division multiple access system is equivalent to the impulse response estimation of the multi‐input multi‐output finite impulse response channels. Our proposed approach is based on the successive estimation of the columns of the equivalent multi‐input multi‐output finite impulse response channels from the lowest degree columns to the highest degree ones. Accordingly, each user's overall channel that is the convolution of the original multipath channel and the spreading sequence is estimated. Then we extract PN sequences from the overall channel using finite alphabet characteristics of the spreading sequence chips for each user. According to simulation results, our proposed scheme outperforms the conventional methods in that it does not require symbol synchronization and does not have channel constraints (for example, AWGN and single user system) in the multipath channels.