Based on the Distributed Coordination Function (DCF) and the Enhanced DCF (EDCF) mechanisms in IEEE 802.11 and 802.11e, a novel backoff scheme for Wireless Local Area Network (WLAN) is proposed. The scheme is to solve...Based on the Distributed Coordination Function (DCF) and the Enhanced DCF (EDCF) mechanisms in IEEE 802.11 and 802.11e, a novel backoff scheme for Wireless Local Area Network (WLAN) is proposed. The scheme is to solve the problem of the packet loss and the decrease of performance due to the increasing Contention Window (CW) when there are continuous collisions. In the proposed scheme, the CW of the packet will change dynamically with different delay for the different traffics. Mathematic formulas are presented to indicate the relationship between the CW and the delay character. ,The performance of the new scheme is also discussed with simulation results. The results show that it helps WLAN system handle multimedia simultaneously.展开更多
This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scal...This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scale, rotation, the shift and the carrier frequency offset between transmitter and receiver.The invariant property is proved theoretically.Through computer simulation the performance is evaluated and the results show that the improved classification algorithm is better and valuable in practice.展开更多
基金Supported by the National Natural Science Foundation of China (No.90304008) ShaanxiInternational Cooperation Project 2003KW-08.
文摘Based on the Distributed Coordination Function (DCF) and the Enhanced DCF (EDCF) mechanisms in IEEE 802.11 and 802.11e, a novel backoff scheme for Wireless Local Area Network (WLAN) is proposed. The scheme is to solve the problem of the packet loss and the decrease of performance due to the increasing Contention Window (CW) when there are continuous collisions. In the proposed scheme, the CW of the packet will change dynamically with different delay for the different traffics. Mathematic formulas are presented to indicate the relationship between the CW and the delay character. ,The performance of the new scheme is also discussed with simulation results. The results show that it helps WLAN system handle multimedia simultaneously.
基金Supported by China TRAPOYT,863 Project(2001AA123031)National Natural Science Foundation of China(No.69872028)
文摘This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scale, rotation, the shift and the carrier frequency offset between transmitter and receiver.The invariant property is proved theoretically.Through computer simulation the performance is evaluated and the results show that the improved classification algorithm is better and valuable in practice.
