465 research outputs found
Channel Tracking for AF MIMO Relaying Systems
In this paper, we consider the problem of channel
estimation in multiple-input multiple-output (MIMO) amplifyand-
forward (AF) relaying systems operating over time varying
channels. Only data at the receiving end are assumed available
for the estimation. By employing a first-order autoregressive
(AR) model for characterizing the time-varying nature of the
channels to be estimated, we derive an expectation-maximization
(EM) Kalman filter (KF) that utilizes the received signal at the
destination to track the individual channel links. The extended
KF algorithm is also derived and compared to the proposed
EM-based KF. Our simulation results show that the proposed
EM-based KF offers better estimation performance with less
complexity when compared to the EKF algorithm
Improving Bandwidth Efficiency in E-band Communication Systems
The allocation of a large amount of bandwidth by regulating bodies in the
70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges
for providing affordable and reliable Gigabit per second wireless
point-to-point links. This article first reviews the available bandwidth and
licensing regulations in the E-band. Subsequently, different propagation
models, e.g., the ITU-R and Cane models, are compared against measurement
results and it is concluded that to meet specific availability requirements,
E-band wireless systems may need to be designed with larger fade margins
compared to microwave systems. A similar comparison is carried out between
measurements and models for oscillator phase noise. It is confirmed that phase
noise characteristics, that are neglected by the models used for narrowband
systems, need to be taken into account for the wideband systems deployed in the
E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed
continuous aperture phased (CAP)-MIMO, is presented. Simulations show that
CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs.
Finally, it is argued that full-duplex relaying can be used to greatly enhance
the coverage of E-band systems without sacrificing throughput, thus,
facilitating their application in establishing the backhaul of heterogeneous
networks.Comment: 16 pages, 6 Figures, Journal paper. IEEE Communication Magazine 201
Full-Duplex Relaying in MIMO-OFDM Frequency-Selective Channels with Optimal Adaptive Filtering
In-band full-duplex transmission allows a relay station to theoretically
double its spectral efficiency by simultaneously receiving and transmitting in
the same frequency band, when compared to the traditional half-duplex or
out-of-band full-duplex counterpart. Consequently, the induced
self-interference suffered by the relay may reach considerable power levels,
which decreases the signal-to-interference-plus-noise ratio (SINR) in a
decode-and-forward (DF) relay, leading to a degradation of the relay
performance. This paper presents a technique to cope with the problem of
self-interference in broadband multiple-input multiple-output (MIMO) relays.
The proposed method uses a time-domain cancellation in a DF relay, where a
replica of the interfering signal is created with the help of a recursive least
squares (RLS) algorithm that estimates the interference frequency-selective
channel. Its convergence mean time is shown to be negligible by simulation
results, when compared to the length of a typical orthogonal-frequency division
multiplexing (OFDM) sequences. Moreover, the bit-error-rate (BER) and the SINR
in a OFDM transmission are evaluated, confirming that the proposed method
extends significantly the range of self-interference power to which the relay
is resilient to, when compared with other mitigation schemes
Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years
Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions
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