An IP tunneling design scheme to reduce advertising delay in open shortest path first (OSPF) networks, in which the link load is required for traffic maintenance, is proposed. A controller and nodes are consisted in a network. A node sends an OSPF traffic engineering (OSPF-TE) advertisement when either link load or topology is changed. The controller determines and adjusts the routes in the network to avoid traffic congestion. The controller may experience delay in receiving advertisements due to OSPF forwarding delay. Therefore, route adjustment may be delayed. In the proposed scheme, an IP tunneling technique is used instead of the OSPF mechanism.
A low complexity Quality-of-Service (QoS)-aware sub-carrier allocation/user-selection technique for the downlink of Multiple-Input Single-Output Orthogonal Frequency Division Multiple-Access (MISO-OFDMA) system is proposed. The algorithm allows simultaneous transmission to multiple users on the same sub-carrier through zero-forcing beamforming (ZFBF). The proposed algorithm enhances QoS by preserving minimum rate for each user while providing high bandwidth data services. Simulation results reveals that our algorithm outperforms other reference algorithms in terms of average sum-rate per sub-carrier and QoS, while lower complexity is attained by the proposed algorithm in terms of execution time needed compared to reference algorithms.
Necessary conditions of a digital modulation signal are investigated in order to estimate its maximum bit error probability (BEP) by using the amplitude probability distribution (APD) of an interfering noise. It was found that the waveform difference between any two symbols needs to be able to be normalized to have an identical APD and amplitude spectrum. Moreover, the spectrum needs to match the frequency selectivity for the APD measurement with a tolerable deviation. Some modulation schemes are discussed with respect to the conditions.
Link metric optimization is crucial for load balancing in a shortest path bridging MAC (SPBM) network. Link metrics and traffic assignment proportions can be optimized by solving a linear programming problem using traffic demand. However, how to assign actual flows so that they are consistent with the optimized proportions has yet to be discussed. This paper proposes a rate-based path selection scheme. The concept is to assign flows to each path so that the total rates of the assigned flows approach the planned rates. With computer simulations, we confirmed that with the proposed scheme flows were assigned to each path so that they were consistent with the optimized proportions.
We propose an optical multipath network system that improves transmission performance by performing diversity reception of the signals from different paths used as working, protection, and reservation paths in an optical mesh network. Long transmission delays occur among the signals from the different paths. Thus, we also propose a diversity reception technique that compensates for the transmission delays by using digital buffer memories at a transmitter side and the estimation of the delays using tap coefficients of digital adaptive equalizers at a receiver side. Numerical simulation shows the validity of the diversity reception technique and improvement in transmission performance.
We present a new approach for the broadband characterization of dielectric materials in the waveguide-penetration method. The new approach uses only two sets of uncalibrated S-parameter measurements: when the dielectric material is loaded into the waveguide, and when it is unloaded. The theory behind the new approach is based on the properties of similar matrices arising during the measurement. Compared to the previous methods, a network analyzer calibration is not required anymore, resulting in a great measurement simplification. We perform measurements in the X-band to validate the new approach.