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Recently, very large multiple-input multiple-output (MIMO) systems have been actively studied for 5G mobile radios. Belief propagation based detection is known as a technique reducing the computational complexity for uplink signal detection. When we consider an LDPC coded MIMO system, it is possible to combine both factor graphs of MIMO detection and LDPC decoding. In the paper, two types: bipartite...
In recent years, several progresses have been made in belief propagation (BP) based signal detection with large scale factor graphs. When we apply the BP algorithm to equalization in a SIMO multipath channel, the factor graph has many short loops where the edge strengths have a fixed pattern. Thus, the proper convergence is not always expected. In general, the LLR oscillates in ill-converged cases...
This paper proposes a normalized belief with the aid of node selection (NS) method in Gaussian belief propagation (GaBP) detection especially for a large multiuser multiple-input multiple-output (MU-MIMO) configurations in bands below 6 GHz. GaBP is known as an efficient detector regarding low computational complexity as well as high detection capability only if the BS has hundreds of receive antennas...
A compressed sensing technique can be used for scatterer detection with less antenna elements. The detection accuracy, however, degrades when scatterers exist also in the outside of a search area. In this paper, we propose a preprocessing scheme for compressed sensing based scatterer detection. The scheme uses a gating technique in a cross range, and suppresses scattering waves from the outside of...
A compressed sensing technique has been studied for accurate scatterer detection. It has many kinds of algorithms, and the features are different. In this paper, we evaluate the performance of compressed sensing algorithms for scatterer detection. We examine three algorithms, OMP, OIHT, and FISTA. We investigate the performance of the algorithms for a single-target and two-target scenarios. It is...
Studies on a massive Multiple-Input Multiple-Output (MIMO) system have been studied in recent years. In a massive MIMO system, antenna elements are arranged not in one dimension but in two dimensions because very large number of antenna elements are used, and the system is called a full-dimension MIMO. In this paper, we generate channel matrices between a transmitter at a base station and user equipments...
Much attention has been paid to precise direction of arrival (DOA) estimation techniques using compressed sensing. We have been investigating DOA estimation of multi-band signals using the half-quadratic regularization method, one of the compressed sensing techniques. Use of multi-band signals provides more precise estimation than that of single-band signals even if the multi-band signals have frequency...
A massive multiple-input multiple-output (MIMO) system using a couple of hundred antenna elements has been arising as an important technology to keep the communication range in higher frequency bands. A further enhancement to increase the number of both transmit and receive antennas will be the next step. It requires the complexity proportional to at least the third power of the number of antenna...
In a wireless mesh network (WMN), the interference from active links in the vicinity of the node of interest is frequently not negligible and thus degrades the area spectral efficiency. An adaptive array is capable to control not only beams but also nulls. Thus, it is expected to help new link establishment. Moreover, the alternative routing boosts such spatial link multiplexing by decreasing the...
In downlink multi-user multiple-input multiple-output (MIMO) systems, a base station needs downlink channel state information (CSI) for each user to eliminate inter-user interference and inter-stream interference. In wireless communication, however, signal propagation environments change over time, and CSI obtained at the base station is different from the channel at the actual transmission time because...
In recent years, much attention has been paid to direction of arrival (DOA) estimation using a compressed sensing technique. In our previous study, we have proposed a method to estimate DOAs of multi-band signals with frequency characteristics. However, we have assumed that all the arrival waves have the same amplitude. In this paper, we propose DOA estimation of signals with frequency characteristics...
Regarding linear estimation theory, the equivalence of the Wiener and Kalman filters is a well-known topic; however, the difference in a practical environment has not been thoroughly discussed. This paper compares the Kalman smoother to the Wiener smoother in terms of practical orthogonal frequency division multiplexing channel estimation on the receiver side. First, conditions for fair comparison...
This study develops the preprocessing theory for time-reversal multiple signal classification (TR-MUSIC) imaging from the one-dimensional (time-domain) gating proposed in earlier papers to a two-dimensional one. Although the one-dimensional gating technique for TR-MUSIC mitigates the effect of noise as well as reduces the required number of antenna elements, the resulting image is subject to focusing...
A massive multiple-input multiple-output (MIMO) system, which has a very large number of antenna elements at the base station (BS), is a promising technology for future high-speed, high-capacity communication systems. However, it faces a serious issue of limited installation space. To cope with this limitation, a full-dimension MIMO (FD-MIMO) system has been proposed. This system can save installation...
A distributed antenna system, where antennas at a base station are spatially distributed over the cell, can improve throughput at the cell edge compared to a centralized antenna system. However, the peak capacity degrades when a remote antenna unit has a few antenna elements due to rank deficiency. In general, the number of antennas at the base station is limited by the number of pilot sequences....
A novel estimation method for direction of arrival angle is introduced. A compressed sensing technique is applied to this application. The resolution of the proposed method is superior to conventional methods such as the MUSIC. Furthermore, we show that the performance can be enhanced when the source signal is multi-band.
Direction-of-arrival (DOA) estimation problem for wideband signals with an array antenna is considered in this report. History of the DOA estimation for wideband signal has several decades. Many techniques have been proposed. However, several problems still remains to be solved or to be developed to make use of wideband signal properties. Much more attention has been paid to wideband DOA estimation...
Much attention has been paid to direction of arrival (DOA) estimation using a compressed sensing technique. In our previous study, we have proposed a method to estimate DOAs of multi-band signals using an array antenna at a receiver. As a result, we have produced an improvement of the probability of correct estimation. Moreover, the method can deal with waves exceeding the degrees of freedom of the...
The near Shannon capacity approaching low-density parity-check (LDPC) linear block codes are now in widespread use in modern systems including the long term evolution advanced (LTE-A) cellular, 802.11η Wi-Fi and DVB-S2 satellite communications standards. The decoders based on the iterative belief propagation algorithm provide near optimum performance but also have very high computational complexity...
The easiest way to improve the throughput performance of multiple-input multiple-output (MIMO) systems is to increase the number of both transmit and receive antennas. Thus, a massive MIMO concept has been proposed recently. In general, however, algorithms detecting spatially-multiplexed signals require the complexity to be proportional to the cubed power of the number of antenna elements at least...
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