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Quadrature amplitude modulation (QAM) is applied extensive in the fields of broadcasting and satellite communication for its high efficiency on power consumption and bandwidth using. The paper introduces a novel circuit which makes use of CORDIC algorithm to implement QAM modulator. The CORDIC module can complete ASK function as well as export two-way orthogonal signal synchronously .By using this character, we can implement high speed QAM modulator with single filter.

Resilient Packet Ring (RPR) is a new technology has just been standardized as IEEE 802.17 for Metropolitan Area Networks (MAN). RPR is significantly more efficient than other technologies especially other ring technologies . But the ring topology is not suit for "Star" pattern traffic which exiting widely in WAN. And when there are too many nodes on a ring, it will risk more time delay and less throughput per node. In this paper, we introduce a novel star-ring architecture and analyse its key technology such as physical topology, logical topology, data path and scalability . The analysis show that the star-ring architecture has advantage than ring and is not hard to implement.

Resilient Packet Ring (RPR) is a new technology has just been standardized as IEEE 802.17 for Metropolitan Area Networks (MAN). RPR can be regarded as a buffer (or register) insertion ring. Thus, the buffer size configuration is very important to the performance of RPR. Currently, it is lacked for its theoretic analysis. In this paper, we initiated RPR'S queue length into queuing theory and investigated their relations with throughput and number of nodes. The results are very close to those of engineering. It also turns out some new points such as queue length does not increase linearly with number of nodes as in our imagination.