Differential Modulation is a non-coherent modulation technique which is used to solve the uncertainty channel problem. The most popular Differential Unitary Modulation technique uses a Space-Time Block Code (STBC) to improve the performance of Differential Modulation technique in multi-in multi-out (MIMO) system. However, using Differential Unitary Modulation technique in the multicarrier system become a big challenge because of the rising of the system complexity. In this paper, we introduce a low complexity differential modulation technique using the property of STBC. The proposed method is proven to provide high-quality performance with a low level of complexity.

The instantaneous throughput is evaluated based on the communication traffic volume per fixed unit time. Although the conventional method can roughly evaluate it within unit time, it is difficult to evaluate the communication situation of each packet in detail. Therefore, the authors propose a method of deriving the throughput based on the occupied duration for one packet transmission. In the proposed method, not only throughput per packet but also throughput of other signals such as beacon signals and variation of Back-off Time can be evaluated. In this paper, we define the occupation duration for deriving throughput during individual UDP transmission, and show analysis examples compared with the conventional method.

The use of watermarks to embed user information is expected to deter the unauthorized use of video content in VOD (Video On-Demand) streaming services. This requires that watermark embedding and video encoding for each video must be finished so rapidly as to not create excessive VOD delay between the user’s video request and video download to the user. This paper describes a watermark embedding and encoding process for a fast combined watermark embedding method, and proposes a new encoding technique that minimizes video quality degradation.