This paper presents the flip-flop tone （FFT） DMAC protocol, a tone based MAC protocol using di- rectional antennas to solve the deafness problem, hidden terminal and exposed terminal problems simulta- neously. It us...This paper presents the flip-flop tone （FFT） DMAC protocol, a tone based MAC protocol using di- rectional antennas to solve the deafness problem, hidden terminal and exposed terminal problems simulta- neously. It uses two pairs of flip-flop tones. The first pair of tone is to send omni-directionally to reach every neighboring node to announce the start and the end of communication, and therefore to alleviate the deafness problem. The second pair of tone is to send directionally towards the sender. It is used to solve the hidden temlinal problem as well as the exposed terminal problem. Evaluation shows that FFT-DMAC can achieve better performance compared to the 802.11 and ToneDMAC protocol.展开更多
We propose a distributed closedloop power control scheme for a cognitive radio network(CRN) based on our developed state space model of the CRN. The whole power control process is separated into outer control loop and...We propose a distributed closedloop power control scheme for a cognitive radio network(CRN) based on our developed state space model of the CRN. The whole power control process is separated into outer control loop and inner control loop in order to solve different problem. In outer loop, the interference temperature(IT) constraint is transformed to a performance index minimized by a state feedback controller to obtain an appropriate target signal to interference plus noise ratio(SINR) of secondary user(SU). For ideal channel model and random time-varying channel model, our designed controller is a linear quadratic regulator(LQR) and a linear quadratic Gaussian(LQG) regulator respectively. While in inner loop, SU controls its transmit power to make the instantaneous SINR track the corresponding target and ensure the IT constraint under the limited threshold. The closed-loop stability of the CRN is proved and the performance of proposed control scheme is presented by computer simulations, which shows that this scheme can effectively guarantee both the requirement of SINR and IT constraint for all SUs.展开更多
Speech coding techniques have been studied not truly to reduce the complexity and bit rate but also to improve the sound quality. CELP type vocoder, used as standard, supports the great stead quality even low bit rate...Speech coding techniques have been studied not truly to reduce the complexity and bit rate but also to improve the sound quality. CELP type vocoder, used as standard, supports the great stead quality even low bit rate. In this paper, the preprocessing of input speech to reduce the bit rate is different from the conventional vocoder. Different kinds of parameter are used for the preprocessing compared with the other parameters to t＇md the more appropriate parameter for the vocoder. The Parameters are used to synthesize the speech not to encode or decode for coding technique so we proposed the simple algorithm not to have the influence on the processing time or the computation time. The parameters in the preprocessing step are speaking rate, duration, and PSOLA technique.展开更多
基金Supported by the National High Teehnology Research and Development Programme of China （No. 2006AA01Z172）；the Provincial Key Laboratory of Computer Information Processing Technology of Jiangsu Province （No. KJS0605）；Natural Science Foundation of China （No. 60573138） ；the National Key Basic Research and Development Progranane of China （No. 2006CB303000）.
文摘This paper presents the flip-flop tone （FFT） DMAC protocol, a tone based MAC protocol using di- rectional antennas to solve the deafness problem, hidden terminal and exposed terminal problems simulta- neously. It uses two pairs of flip-flop tones. The first pair of tone is to send omni-directionally to reach every neighboring node to announce the start and the end of communication, and therefore to alleviate the deafness problem. The second pair of tone is to send directionally towards the sender. It is used to solve the hidden temlinal problem as well as the exposed terminal problem. Evaluation shows that FFT-DMAC can achieve better performance compared to the 802.11 and ToneDMAC protocol.
基金supported by the National Natural Science Foundation of China (Grant No. 61571209)
文摘We propose a distributed closedloop power control scheme for a cognitive radio network(CRN) based on our developed state space model of the CRN. The whole power control process is separated into outer control loop and inner control loop in order to solve different problem. In outer loop, the interference temperature(IT) constraint is transformed to a performance index minimized by a state feedback controller to obtain an appropriate target signal to interference plus noise ratio(SINR) of secondary user(SU). For ideal channel model and random time-varying channel model, our designed controller is a linear quadratic regulator(LQR) and a linear quadratic Gaussian(LQG) regulator respectively. While in inner loop, SU controls its transmit power to make the instantaneous SINR track the corresponding target and ensure the IT constraint under the limited threshold. The closed-loop stability of the CRN is proved and the performance of proposed control scheme is presented by computer simulations, which shows that this scheme can effectively guarantee both the requirement of SINR and IT constraint for all SUs.
基金supported by the Brain Korea 21 Project in 2010,and the MKE(The Ministry of Knowledge Economy,Korea)the ITRC(Information Technology Research Center)support program(NIPA-2010-(C1090-1021-0010))
文摘Speech coding techniques have been studied not truly to reduce the complexity and bit rate but also to improve the sound quality. CELP type vocoder, used as standard, supports the great stead quality even low bit rate. In this paper, the preprocessing of input speech to reduce the bit rate is different from the conventional vocoder. Different kinds of parameter are used for the preprocessing compared with the other parameters to t＇md the more appropriate parameter for the vocoder. The Parameters are used to synthesize the speech not to encode or decode for coding technique so we proposed the simple algorithm not to have the influence on the processing time or the computation time. The parameters in the preprocessing step are speaking rate, duration, and PSOLA technique.
