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To evaluate the effects of wall motion asynchrony on left ventricular (LV) relaxation, we performed atrioventricular sequential pacing with the second stimulation at six epicardial sites in open-chest anesthetized dogs. Myocardial segment lengths in the basal, mid, and apical LV free wall were measured by ultrasonic crystals. The standard deviation of interval from the onset of the QRS complex to that of elongation in each segment length was used as a quantitative index for asynchrony (asynchrony index, AI). The AI increased significantly in all sequential pacing modes compared with the control right atrial pacing. The time constant (T) of LV relaxation derived from exponential fit with zero-asymptote was prolonged significantly in all sequential pacing modes except for pacing at the LV base. In each dog there was a good correlation between changes in AI and T [r = 0.61 - 0.98 (mean = 0.84)]. Since the regional inactivation process of the myocardium is considered to be unchanged during these interventions, we concluded that asynchronous wall motion plays an important role in the impairment of LV relaxation.

This paper proposes two cyclostationarity-inducing transmission methods that enable the receiver to distinguish among different systems that use a common orthogonal frequency division multiplexing-(OFDM-) based air interface. Specifically, the OFDM signal is configured before transmission such that its cyclic autocorrelation function (CAF) has peaks at certain preselected cycle frequencies. The first proposed method inserts a specific preamble where only a selected subset of subcarriers is used for transmission. The second proposed method dedicates a few subcarriers in the OFDM frame to transmit specific signals that are designed so that the whole frame exhibits cyclostationarity at preselected cycle frequencies. The detection probabilities for the proposed cyclostationarity-inducing transmission methods are evaluated based on computer simulation when optimum and suboptimum detectors are used at the receiver.

We propose a QoS control architecture for mobile multimedia streaming in which RTP monitoring agents report QoS information to media servers. The RTP monitoring agents lie midway between wired networks and radio links, monitor RTP packets sent from media servers to mobile terminals, and report quality information to media servers so that the servers can realize network-adaptive QoS control. By analyzing the information sent from the agents, the servers can distinguish quality degradation caused by network congestion from that caused by radio link errors, and can improve service quality by controlling the transmission rate and robustness against packet loss. Simulation results show our implemented QoS control schemes that use the feedbacks from the agent and control transmission rate and robustness provide better video quality than a simple rate control mechanism. 2513 0-7803-7400-2/02/$17.00 © 2002 IEEE