2,549 research outputs found
Yaw Rate and Sideslip Angle Control Through Single Input Single Output Direct Yaw Moment Control
Electric vehicles with independently controlled drivetrains allow torque vectoring, which enhances active safety and handling qualities. This article proposes an approach for the concurrent control of yaw rate and sideslip angle based on a single-input single-output (SISO) yaw rate controller. With the SISO formulation, the reference yaw rate is first defined according to the vehicle handling requirements and is then corrected based on the actual sideslip angle. The sideslip angle contribution guarantees a prompt corrective action in critical situations such as incipient vehicle oversteer during limit cornering in low tire-road friction conditions. A design methodology in the frequency domain is discussed, including stability analysis based on the theory of switched linear systems. The performance of the control structure is assessed via: 1) phase-plane plots obtained with a nonlinear vehicle model; 2) simulations with an experimentally validated model, including multiple feedback control structures; and 3) experimental tests on an electric vehicle demonstrator along step steer maneuvers with purposely induced and controlled vehicle drift. Results show that the SISO controller allows constraining the sideslip angle within the predetermined thresholds and yields tire-road friction adaptation with all the considered feedback controllers
Multipath Multiplexing for Capacity Enhancement in SIMO Wireless Systems
This paper proposes a novel and simple orthogonal faster than Nyquist (OFTN)
data transmission and detection approach for a single input multiple output
(SIMO) system. It is assumed that the signal having a bandwidth is
transmitted through a wireless channel with multipath components. Under
this assumption, the current paper provides a novel and simple OFTN
transmission and symbol-by-symbol detection approach that exploits the
multiplexing gain obtained by the multipath characteristic of wideband wireless
channels. It is shown that the proposed design can achieve a higher
transmission rate than the existing one (i.e., orthogonal frequency division
multiplexing (OFDM)). Furthermore, the achievable rate gap between the proposed
approach and that of the OFDM increases as the number of receiver antennas
increases for a fixed value of . This implies that the performance gain of
the proposed approach can be very significant for a large-scale multi-antenna
wireless system. The superiority of the proposed approach is shown
theoretically and confirmed via numerical simulations. {Specifically, we have
found {upper-bound average} rates of 15 bps/Hz and 28 bps/Hz with the OFDM and
proposed approaches, respectively, in a Rayleigh fading channel with 32 receive
antennas and signal to noise ratio (SNR) of 15.3 dB. The extension of the
proposed approach for different system setups and associated research problems
is also discussed.Comment: IEEE Transactions on Wireless Communication
Bits About the Channel: Multi-round Protocols for Two-way Fading Channels
Most communication systems use some form of feedback, often related to
channel state information. In this paper, we study diversity multiplexing
tradeoff for both FDD and TDD systems, when both receiver and transmitter
knowledge about the channel is noisy and potentially mismatched. For FDD
systems, we first extend the achievable tradeoff region for 1.5 rounds of
message passing to get higher diversity compared to the best known scheme, in
the regime of higher multiplexing gains. We then break the mold of all current
channel state based protocols by using multiple rounds of conferencing to
extract more bits about the actual channel. This iterative refinement of the
channel increases the diversity order with every round of communication. The
protocols are on-demand in nature, using high powers for training and feedback
only when the channel is in poor states. The key result is that the diversity
multiplexing tradeoff with perfect training and K levels of perfect feedback
can be achieved, even when there are errors in training the receiver and errors
in the feedback link, with a multi-round protocol which has K rounds of
training and K-1 rounds of binary feedback. The above result can be viewed as a
generalization of Zheng and Tse, and Aggarwal and Sabharwal, where the result
was shown to hold for K=1 and K=2 respectively. For TDD systems, we also
develop new achievable strategies with multiple rounds of communication between
the transmitter and the receiver, which use the reciprocity of the forward and
the feedback channel. The multi-round TDD protocol achieves a
diversity-multiplexing tradeoff which uniformly dominates its FDD counterparts,
where no channel reciprocity is available.Comment: Submitted to IEEE Transactions on Information Theor
Optimized Scalable Image and Video Transmission for MIMO Wireless Channels
In this chapter, we focus on proposing new strategies to efficiently transfer a compressed image/video content through wireless links using a multiple antenna technology. The proposed solutions can be considered as application layer physical layer (APP-PHY) cross layer design methods as they involve optimizing both application and physical layers. After a wide state-of-the-art study, we present two main solutions. The first focuses on using a new precoding algorithm that takes into account the image/video content structure when assigning transmission powers. We showed that its results are better than the existing conventional precoders. Second, a link adaptation process is integrated to efficiently assign coding parameters as a function of the channel state. Simulations over a realistic channel environment show that the link adaptation activates a dynamic process that results in a good image/video reconstruction quality even if the channel is varying. Finally, we incorporated soft decoding algorithms at the receiver side, and we showed that they could induce further improvements. In fact, almost 5 dB peak signal-to-noise ratio (PSNR) improvements are demonstrated in the case of transmission over a Rayleigh channel
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