Semiblind ML OSTBC-OFDM detection in block fading channels

[[abstract]]This paper presents a semiblind maximum-likelihood (ML) detector for the orthogonal space-time block coded orthogonal frequency division multiplexing (OSTBC-OFDM) system. Many existing blind/ semiblind OSTBC-OFDM receivers typically require that the channel is static over a multitude of OSTBC-OFDM blocks. The proposed method is specifically for detection over one OSTBC-OFDM block only, and hence is well suited to block fading channels. The presented identifiability analysis shows that the data can be uniquely identified in a probability one sense by using one pilot code only, in contrast to the pilot-based least-squares channel estimator which requires at least L pilot codes where L is the channel length. Simulation examples are then presented to show the efficacy of the proposed detector.[[fileno]]2030157030006[[department]]電機工程學

Performance of the MIMO CS-PRP-OFDM Systems with Complementary Codes

Proposed new scheme for ST-BC MIMO-OFDM systems,[[abstract]]This paper presents a new transceiver framework of the MIMO-OFDM systems, with the space-time block code (STBC). Unlike the conventional Pseudo-Random Postfix (PRP) - OFDM in our proposed framework the null samples of zero-padding (ZP)-OFDM is replaced by known cyclic postfix sequence (CPS), weighted by a pseudo-random (PR) scalar. Since the CPS is implemented by the cyclic-shift (CS) complementary code (CC) sequences, the proposed transceiver scheme is referred to as the MIMO CS-PRP-OFDM systems. By exploring the useful property of CC sequences, convolved with channel formation, the receiver design associated with the semi-blind channel estimation of the proposed MIMO CS-PRP-OFDM systems is affected only by the background noise. It avoids the interference of the transmitted signals, and yields achieving better system performance, in terms of symbol error rate, compared with the conventional PRP-OFDM based systems, with less complexity. This is especially true when the signal-to-noise ratio is increased.[[incitationindex]]EI[[conferencetype]]國際[[conferencedate]]20111207~20111209[[conferencelocation]]Chiang Mai, Thailan

Performance of the MIMO PRCP-OFDM System with Orthogonal Cyclic-Shift Sequences

[[abstract]]Unlike the conventional Pseudo-Random Posfix (PRP) orthogonal frequency division multiplexing (OFDM) or PRP-OFDM approach, recently we proposed a new transceiver framework for OFDM system, named as the Pseudo Random Cyclic Postfix (PRCP)-OFDM, with complementary codes (CC). Also, it wa MIMO PRCP-OFDM system the performance is investis extended to the multiple-input multiple-output (MIMO) antennas system, equipped with the space-time block code (SP-BC). In this paper, the cyclic postfix (CP) sequence is implemented with the Orthogonal Cyclic-shift (OCS) sequences to substitute the CC. By exploring the useful property of OCS sequences, convolved with channel information, at receiver side it can be employed to perform semi-blind channel estimation without incurring the signal interference to the desired postfix sequences. It is affected only by the background noise, and yields achieving better system performance. To demonstrate the merits of proposed ST-BCgated and further compared with the ST-BC MIMO PRP-OFDM system and ST-BC MIMO CP-OFDM system with optimal training pilots, under various channel environments.[[sponsorship]]ISPACS[[incitationindex]]EI[[conferencetype]]國際[[conferencedate]]20121104~20121107[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Tamsui, Taiwa

A semi-blind channel estimation method for multiuser multiantenna OFDM systems

A subspace-based blind method is proposed for estimating the channel responses of a multiuser and multiantenna orthogonal frequency division multiplexing (OFDM) uplink system. It gives estimations to all channel responses subject to a scalar matrix ambiguity and does not need precise channel order information (only upper bound for the orders is required). Furthermore, the scalar ambiguity matrix can be easily resolved by using only one pilot OFDM block, given that the number of users is smaller than the number of symbols in the pilot symbol block. Equalization methods are discussed based on the estimated channels. By using partial knowledge of the channels, a multipath subspace method is proposed that reduces the computational complexity. Simulations show that the methods are effective and robust.published_or_final_versio