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Adaptive modulation is a technique which alters constellation size depending on channel condition to achieve highspeed data transmission. However, the well-known modulation schemes transmitting odd bits per symbol, such as 8-ary phase shift keying (PSK) and cross quadrature amplitude modulation (cross QAM), are generally not considered as a candidate for the adaptive use due to their inherent power...
We have designed and implemented an underwater modem using a general-purpose waterproof ultrasonic sensor which is appropriate for UWSN owing to its low-power property and extremely low cost. As a succeeding work, we will try to improve the performance of the underwater modem in terms of data rate and communication distance by adopting state-of-art transmission technology.
Underwater sensor networks (USN) for ocean development and disaster prevention have been emerged as one of interesting research topics recently. Since low-power, high-speed and inexpensive communication modem is a prerequisite for deployment of USN, in this paper we design and implement an underwater modem by utilizing general-purpose waterproof ultrasonic sensors. Also, we make some experiments in...
The recently suggested triangular quadrature amplitude modulation (TQAM) provides considerable power gain over square quadrature amplitude modulation (SQAM) at the expense of slight increase in detection complexity. However, power gain of the TQAM is limited on account of the constraint that signal points are regularly distributed at the vertexes of contiguous equilateral triangles. In this paper,...
It is well known that the square quadrature amplitude modulation (QAM) has been widely used as a modulation technique for digital communication systems due to its simple detection in spite that the power efficiency of the square QAM is not optimum. The newly proposed 16-ary triangular QAM provides considerable power gain while keeping low detection complexity. In this paper, we propose two 64-ary...
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