The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where...The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.展开更多
Recently some P2P systems have constructed the small world network using the small world model so as to improve the routing performance.In this paper,we propose a novel probabilistic cache scheme to construct the smal...Recently some P2P systems have constructed the small world network using the small world model so as to improve the routing performance.In this paper,we propose a novel probabilistic cache scheme to construct the small world network based on the small world model and use it to improve CAN,that is,PCCAN(Probabilistic Cache-based CAN).PCCAN caches the long contact.It uses the worm routing replacing mechanism and probabilistic replacing strategy on the cache.The probabilistic cache scheme proves to be an efficient approach to model the small world phenomenon.Experiments in both the static and the dynamic network show that PCCAN can converge to the steady state with the cache scheme,and the routing performance is significantly improved with additional low overheads in the network compared with CAN.展开更多
We start this paper by answering the questions： What requirements should a good Loss Differentiation Mechanism （LD） for 802.11 networks in loT meet？ Do the existing LDs work well in 802.11 networks when moving tow...We start this paper by answering the questions： What requirements should a good Loss Differentiation Mechanism （LD） for 802.11 networks in loT meet？ Do the existing LDs work well in 802.11 networks when moving towards loT？ Then we present the four properties that a LD used in loT should own and the two-folded factors that we should consider when designing such a LD. Thereby, a novel LD is proposed utilizing the back- off frozen event to reveal collision probability. Our mechanism works efficiently with standard 802.11 ; only practical statistics information is needed. In ad- dition, our mechanism can be done solely by the sender without introducing extra signaling overhead. Extensive simulations show that our mechanism can be applicable to different scenarios in 802. 11 WLANs.展开更多
A plastic surface-relief grating as a wavelength division multiplexer is designed and fabricated with the conventional mould pressing technique using the transmission-type fused quartz phase grating as mask pattern an...A plastic surface-relief grating as a wavelength division multiplexer is designed and fabricated with the conventional mould pressing technique using the transmission-type fused quartz phase grating as mask pattern and polycarbonate as basal material.The experiment results show that in an optimizing process,the plastic surface-relief grating has the highest firstorder diffraction efficiency under adequate groove depth and incident angle,and can be used as the best optical path for wavelength division multiplexing(WDM).We also establish the experiment setup for testing the WDM performance of the plastic surface-relief grating based wavelength division multiplexer.The results show that the proposed wavelength division multiplexer has the high-stability temperature characteristics,the low insertion loss of less than 5 dB,the large isolation of greater than 20 dB,the low polarization-dependent loss(PDL) of less than 0.4 dB and the relatively steep pass-band characteristics.It is a WDM device with good performance,which can be applied in short distance communication.展开更多
基金supported in part by National 973 Program(2012CB315705)NSFC Program(61302086,61271042,61107058, 61302016,and 61335002)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education(20130005120007)Program for New Century Excellent Talents in University(NCET-13-0682)Fundamental Research Funds for the Central Universities
文摘The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.
基金Sponsored by the Science & Technology Committee of Shanghai Municipality Key Technologies R&D Project(Grant No.03dz15027)the Science & Technology Committee of Shanghai Municipality Key Project(Grant No.025115032).
文摘Recently some P2P systems have constructed the small world network using the small world model so as to improve the routing performance.In this paper,we propose a novel probabilistic cache scheme to construct the small world network based on the small world model and use it to improve CAN,that is,PCCAN(Probabilistic Cache-based CAN).PCCAN caches the long contact.It uses the worm routing replacing mechanism and probabilistic replacing strategy on the cache.The probabilistic cache scheme proves to be an efficient approach to model the small world phenomenon.Experiments in both the static and the dynamic network show that PCCAN can converge to the steady state with the cache scheme,and the routing performance is significantly improved with additional low overheads in the network compared with CAN.
基金supported by the National Basic Research Program of China(No.2011CB302702)the Beijing Nova Program and the National Natural Science Foundation of China(Nos.60803140,60970133,61070187)
文摘We start this paper by answering the questions： What requirements should a good Loss Differentiation Mechanism （LD） for 802.11 networks in loT meet？ Do the existing LDs work well in 802.11 networks when moving towards loT？ Then we present the four properties that a LD used in loT should own and the two-folded factors that we should consider when designing such a LD. Thereby, a novel LD is proposed utilizing the back- off frozen event to reveal collision probability. Our mechanism works efficiently with standard 802.11 ; only practical statistics information is needed. In ad- dition, our mechanism can be done solely by the sender without introducing extra signaling overhead. Extensive simulations show that our mechanism can be applicable to different scenarios in 802. 11 WLANs.
基金supported by the Natural Science Foundation of Fujian Province of China (No.2011J01353)
文摘A plastic surface-relief grating as a wavelength division multiplexer is designed and fabricated with the conventional mould pressing technique using the transmission-type fused quartz phase grating as mask pattern and polycarbonate as basal material.The experiment results show that in an optimizing process,the plastic surface-relief grating has the highest firstorder diffraction efficiency under adequate groove depth and incident angle,and can be used as the best optical path for wavelength division multiplexing(WDM).We also establish the experiment setup for testing the WDM performance of the plastic surface-relief grating based wavelength division multiplexer.The results show that the proposed wavelength division multiplexer has the high-stability temperature characteristics,the low insertion loss of less than 5 dB,the large isolation of greater than 20 dB,the low polarization-dependent loss(PDL) of less than 0.4 dB and the relatively steep pass-band characteristics.It is a WDM device with good performance,which can be applied in short distance communication.
