We investigate gain transient responses of an automatic gain control (AGC) EDFA with fast electrical feed-forward pump control. Even if each of the AGC EDFAs can well suppress the gain transients for add/drop operations with various switch speeds, the cumulative transients in cascaded AGC EDFAs give rise to a non-negligible impact. We demonstrate that a high-speed variable optical attenuator (VOA) can suppress such cumulative transients. Error-free operation of a surviving channel under the instantaneous load and unload condition with six cascaded AGC EDFAs is confirmed. The burst mode signal is 7-ms duration with 16-dB range.
This letter proposes an IP traceback scheme based on the hop count. The proposed scheme solves the limitation of a storage capacity in a conventional scheme that stores all the packets passing through each router in an autonomous system. In the proposed scheme, each router detects spoofed packets, logs the hashes of only the detected packets, and stores them by using the Bloom filter. To detect spoofed packets, each router compares their time-to-live values with the expected values on our hop count table, which is maintained by a link-state routing protocol at each router. Numerical results show that the proposed scheme reduces the storage capacity effectively, compared with the conventional scheme.
This paper proposes a THP (Tomlinson-Harashima Precoding) scheme for DFT-spread MIMO-OFDM (Multi-Input Multi-Output Orthogonal Frequency Division Multiplexing) systems. In the proposed structure, the precoder is to be implemented in the frequency domain while the modulo operation, which is a non-linear process required to reduce the transmitter power enhancement, is carried out in the time domain. The feasibility of the proposed THP scheme will be shown by the computer simulation.
A new Unitary ESPRIT-MUSIC algorithm for joint direction of departure (DOD) and direction of arrival (DOA) in bistatic MIMO radar is presented. The received data matrix is extended to a new matrix which is a centro-Hermitian matrix. A unitary transformation can be applied which converts a complex-valued matrix into a real-valued matrix by taking the advantage of the property of centro-Hermitian matrix. Then the DODs and DOAs are estimated by Unitary ESPRIT and Unitary Root-MUSIC, respectively. Compared with the combined ESPRIT-MUSIC method, the proposed method provides better performance and lower computational complexity. Some simulation results are presented to verify the efficiency of the proposed method.