Graph-based joint channel estimation and data detection for large-scale multiuser MIMO-OFDM systems /

Download
2015
Tekin, Şeref Yaşar
In this thesis, a graph-based soft iterative receiver for large-scale multiuser MIMO-OFDM systems is proposed that performs joint channel estimation and data detection over time-varying frequency selective channel. In an uplink scenario, factor graph structures for the transmitter of users and the receiver of base-station are presented, which provide Gaussian message passing between nodes. Instead of LLR, reliability information of symbols are used to decrease complexity of the proposed algorithm. Training symbols, known at the receiver, are utilized to get channel state information at the initialization. Also a new training structure is proposed which enables channel estimation and data detection for numerous users. Soft channel estimation process is introduced which utilizes correlation information between channel coefficients. Transfer nodes bring reliability information of channel coefficients between coefficient nodes to converge actual value. Message passing schedule is rearranged to enhance performance of the graph based soft iterative receiver. Extrinsic information exchange is applied between nodes of the repeated symbols. Soft information of the channel coefficients and symbols are jointly refined in each iteration. The BER performance analysis of graph based soft iterative receiver is investigated by comparing non-iterative ML and MRC. Simulation results show that the proposed algorithm with channel knowledge has a similar performance with MRC and outperforms non-iterative ML. Performance of GSIR with different training symbol spacing, number of users, number of receive antennas, code rates and constellations are compared to provide an overview of the proposed algorithm. Also channel estimation performance of GSIR is analyzed by comparing with perfect channel knowledge case. A LDPC decoder is used in combination with GSIR to increase total performance.

Suggestions

Out-of-band radiation and CFO immunity of potential 5G multicarrier modulation schemes
Üçüncü, Ali Bulut; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2015)
In this study, generalized frequency division multiplexing (GFDM) and windowed cyclic prefix circular offset quadrature amplitude modulation (WCP-COQAM), which are candidate physical layer modulation schemes for the 5G systems, are compared to orthogonal frequency division multiplexing (OFDM) in terms of out-of-band (OOB) radiation levels and carrier frequency offset (CFO) immunity. GFDM and WCP- COQAM are shown to be superior to OFDM with respect to OOB emissions in some studies in literature. However, we c...
Blind channel estimation in OFDM systems
Ayas, Mehmet Akif; Diker Yücel, Melek; Department of Electrical and Electronics Engineering (2015)
In this thesis, we have studied blind channel estimation methods for single-input-multiple-output (SIMO) orthogonal frequency division multiplexing (OFDM) systems in time and frequency domain, in which the cross relation between the channel gains and a single snapshot of the received signal on each subcarrier is utilized. We have performed blind channel estimation for uncorrelated and correlated Rayleigh fading channel pairs using time and frequency methods in OFDM systems with one-transmitting, two-receivi...
Optimizing age of information on real-life TCP/IP connections through reinforcement learning
Sert, Egemen; Sonmez, Canberk; Baghaee, Sajjad; Uysal, Elif (2018-07-05)
Age of Information (AoI) has emerged as a performance metric capturing the freshness of data for status-update based applications ( e.g. , remote monitoring) as a more suitable alternative to classical network performance indicators such as throughput or delay. Optimizing AoI often requires distinctly novel and sometimes counter-intuitive networking policies that adapt the rate of update transmissions to the randomness in network resources. However, almost all previous work on AoI to data has been theoretic...
Broadband solutions of potential integral equations with NSPWMLFMA
Khalichi, Bahram; Ergül, Özgür Salih; Ertürk, Vakur B. (Institute of Electrical and Electronics Engineers (IEEE), 2019-06)
In this communication, a mixed-form multilevel fast multipole algorithm (MLFMA) is combined with the recently introduced potential integral equations (PIEs), also called as the A-phi system, to obtain an efficient and accurate broadband solver that can be used for the solution of electromagnetic scattering from perfectly conducting surfaces over a wide frequency range including low frequencies. The mixed-form MLFMA uses the nondirective stable planewave MLFMA (NSPWMLFMA) at low frequencies and the conventio...
Prospects of FMCW-based frequency diverse array radar
Cetiner, Ramazan; Cetintepe, Cagri; Demir, Şimşek; Hizal, Altunkan (2019-11-01)
The linear frequency modulated (LFM) frequency modulated continuous wave (FMCW)-based frequency diverse array (FDA) radar concept is investigated in detail. The radar operates as a linear pulsed FMCW/FDA in the transmission (TX) mode while it operates as a pulsed FMCW/phased array (PA) in the receiving mode. The issues such as low signal-to-noise ratio (SNR) of FDA, the time-angle scanning and time-range ambiguities are studied. It is shown that the local instantaneous frequency bandwidth is much smaller th...
Citation Formats
Ş. Y. Tekin, “Graph-based joint channel estimation and data detection for large-scale multiuser MIMO-OFDM systems /,” M.S. - Master of Science, Middle East Technical University, 2015.