Graph based iterative detection and channel estimation for sparse frequency selective channels

Download
2013
Kaygusuz, Ahmet Baran
The wireless channel is not only susceptible to noise and interference but also other channel impediments like multipath spread, Doppler spread, Doppler shift, and these impediments may change over time. Iterative receiver structures are commonly studied and utilized as they can be very effective in mitigating detrimental effects of the wireless channel. Iterative detection that performs decoding and estimation jointly can be realized in various ways. However, some methods depend on the memory of the channel and hence become computationally complex especially for sparse frequency selective channels. In this thesis, a factor graph based iterative detection is investigated with channel estimation for sparse channels. The sum-product algorithm applied on a factor graph attains optimum or near-optimum performance while its complexity increases linearly with the number of nonzero channel taps in such channels. We study the performance of graph based detection with different channel estimation schedules. Our results indicate that the method studied here enables operation at higher Doppler spreads and possibly with shorter training sequences.

Suggestions

Blind channel estimation based on the Lloyd-Max algorithm innarrowband fading channels and jamming
Dizdar, Onur; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2011)
In wireless communications, knowledge of the channel coefficients is required for coherent demodulation. In this thesis, a blind channel estimation method based on the Lloyd-Max algorithm is proposed for single-tap fading channels. The algorithm estimates the constellation points for the received signal using an iterative least squares approach. The algorithm is investigated for fast-frequency hopping systems with small block lengths and operating under partial-band and partial-time jamming for both detecti...
Interference suppression capability of faster than symbol rate sampling and frequency domain oversampling
Balevi, Eren; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2016)
Detection of symbols in the presence of many interference sources is a difficult task in wireless channels. It is obligatory to reduce the interference for reliable communication. In this dissertation, minimum mean square error (MMSE) detection is investigated to suppress interference. Faster Than Symbol Rate (FTSR) sampling and Frequency Domain Oversampling (FDO) methods are proposed to enhance the interference suppression level of MMSE detection for both single user and multiuser communication. The aim of...
Sum Capacity of General Deterministic Interference Channel with Channel Output Feedback
Sahai, Achaleshwar; Aggarwal, Vaneet; Yüksel Turgut, Ayşe Melda; Sabharwal, Ashutosh (2010-01-01)
In a two-user interference channel, there are four possible feedback paths - two from each receiver to the transmitters. This leads to 16 possible models of feedback. In this paper, we derive the sum capacity of two user deterministic interference channel for all sixteen cases. We find that whenever any of the direct link feedback from a receiver to its own transmitter is present, the sum-capacity is the same as when all four feedback links are present. Further when no direct link feedback is present, the s...
Electronically tunable microwave bandstop filter design and implementation
Oruç, Sacid; Yıldırım, Nevzat; Department of Electrical and Electronics Engineering (2010)
In modern broadband microwave applications, receivers are very sensitive to interference signals which can come from the system itself or from hostile emitters. Electronically tunable bandstop filters can be used to eliminate these interference signals with adaptation to changing frequency conditions. In this thesis, electronically tunable bandstop filter design techniques are investigated for microwave frequencies. The aim is to find filter topologies which allow narrowband bandstop or ‘notch’ filter desig...
Dimension reduced robust beamforming for towed arrays
Topçu, Emre; Candan, Çağatay; Department of Electrical and Electronics Engineering (2015)
Adaptive beamforming methods are used to obtain higher signal to interference plus noise ratio at the array output. However, these methods are very sensitive to steering vector and covariance matrix estimation errors. To overcome this issue, robust methods are usually employed. On the other hand, implementation of these robust methods can be computationally expensive for arrays with large number of sensors. Reduced dimension techniques aim to lower the computational load of adaptive beamforming algorithms w...
Citation Formats
A. B. Kaygusuz, “Graph based iterative detection and channel estimation for sparse frequency selective channels,” M.S. - Master of Science, Middle East Technical University, 2013.