Because of limitation of channel state information (CSI) feedback resource, multiuser (MU) MIMO-OFDM system usually divides all usable subcarriers into several subbands and the CSI of middle subcarrier of each subband is fed back. This feedback style generates CSI error among each subband. Due to this CSI error, a MU MIMO-OFDM system based on vector perturbation (VP) yields inefficient perturbation vectors (PVs) and mismatched spatial filters, which cause severe performance degradation. In this letter, we show that the performance degradation is mainly caused from the mismatched spatial filters rather than the inefficient PVs. This result is useful to design of a computational complexity reduction for the VP based system by reducing the matrix operations for PV search.
This letter proposes a routing scheme both that balances traffic load to avoid network congestion in the stationary state and that recovers a network failure quickly, in corporation with the IP fast reroute, in the unusual state. To balance traffic load, each router forwards packets to the primary and backup ports, which are defined in the IP fast reroute, with suitable distribution ratios. We develop a heuristic algorithm to get distribution ratios that decreases network congestion ratio. We confirm that our scheme decreases network congestion ratio 31% in average at the stationary state while keeping the fast recovery capability, compared to the conventional IP fast reroute scheme.
In recent years, Radio Frequency Identification (RFID) systems are expected to be used in the medical field. Therefore we have come to suggest a simple urination detection system by the RFID system. In our presented system a tag is embedded into a diaper worn by a care-receiver and the care-personnel bring a reader close to the tag. Thus, in a dry diaper, the tag can communicate with the reader. However, in a wet diaper, the presented tag cannot communicate with the reader, because the characteristics of the tag antenna are changed by urination. So urination is detected by weather the presented tag can communicate with the reader or not. In this paper, we have designed the tag antenna and analyzed it by numerical calculations. In addition, we fabricated the tag and measured it in a real situation. As a result the presented system can be applied in urination detection.
It has been previously proved that multi-channel blind source separation (BSS) can separate the deterministic sinusoidal signals by using independent component analysis (ICA) technique. In this paper, we derive a single channel BSS method for deterministic sinusoidal signals with ICA. The proposed single channel BSS method achieves separation by utilizing additional filters to virtually provide a mixture matrix for BSS. Simulation results showed the effectiveness of the proposed method.
Underlay cognitive radio allows simultaneous primary and secondary transmissions over the same band given that the secondary interference is below an acceptable level. This paper proposes an interference alignment (IA) based joint optimization design for the single secondary transceiver. To regulate the secondary interference on the primary receiver and maximize the secondary rate, the precoding and power allocation matrices are jointly optimized in both perfect and imperfect channel knowledge. Numerical results show that the proposed methods are able to protect the licensed user and support higher secondary rates due to the interference allowance on the primary receiver.
This paper proposes a new upgrading method of the existing passive optical network (PON) by hybrid amplification, which uses a distributed Raman amplifier (DRA), a lumped Raman amplifier (LRA) and Er-doped fiber amplifier (EDFA). Properties of hybrid amplification determine the realization of the proposed upgrading method. For estimating the gain and OSNR (optical signal noise ratio) of EDFA with 980 and 1480nm pumping, we have developed new equations. Calculated gain and OSNR values of EDFA and LRA are compared with experimental results and they show in good agreement.