A novel method is proposed to analyze the capacity of future Code Division Multiple Access （CDMA） systems carrying multimedia services. The power level allocation is firstly investigated to meet each call＇s Bit Err...A novel method is proposed to analyze the capacity of future Code Division Multiple Access （CDMA） systems carrying multimedia services. The power level allocation is firstly investigated to meet each call＇s Bit Error Rate （BER） requirement, then the system capacity is defined from the conditions lbr the existence of the physical meaning of these power levels. Simulation results have shown that the capacity analyzing methods can be well used in the performance evaluation of the system accommodating heterogeneous services and the spectral efficiency of this scheme is higher than the existing ones.展开更多
The characteristics of underwater acoustic channel such as long propagation delay and low bit rate cause the MAC(Medium Access Control) protocols designed for radio channels to be either inapplicable,or have low effic...The characteristics of underwater acoustic channel such as long propagation delay and low bit rate cause the MAC(Medium Access Control) protocols designed for radio channels to be either inapplicable,or have low efficiency for UWSN(Underwater Sensor Network).We propose a hierarchical and distributed code assignment algorithm based on divisive probability function which can avoid conflict between spread codes with high probability,and provide a statebased MAC protocol for UWSN.Without RTS/CTS(Request To Send/Clear To Send) handshaking,each node maintains a neighbor table including state field,and packages are forwarded according to the state of the receiver,so it can avoid the interference caused by transmitting to a sending node in a half-duplex system and improve channel utilization.The design of power control minimizes the nearfar effect inherent in CDMA.Simulation results reveal that state-based CDMA protocol shows outstanding performance in throughput,delivery ratio and resource-consumption.展开更多
An object segment similarity function is taken into account from the continuous media frames to measure the individual streaming profit of certain segment versions of a media object.Therefore,a new segment version-bas...An object segment similarity function is taken into account from the continuous media frames to measure the individual streaming profit of certain segment versions of a media object.Therefore,a new segment version-based transcoding(SVT)mechanism is derived for a quality of service(QoS)of client-centric media streaming in wireless mobile networks.The derived function utilizes the fuzzy similarity of certain segment versions of an object.This mechanism provides the effectiveness of reduction of the stream startup latency among segment versions,and the average access of each version.Thus,the proposed segment version transcoding mechanism reduces packet loss which in turn increases streaming performance and throughput.The performance of the partitioned segment versions is simulated and some segment versions are completed.The simulation results show that the proposed mechanism outperforms the other mechanisms in average cache hit ratio and in average startup latency ratio.展开更多
基金Supported by the open research fund of the National Mobile Communications Key Lab of the Southeast Uni-versity and by the Hong Kong Research Council.
文摘A novel method is proposed to analyze the capacity of future Code Division Multiple Access （CDMA） systems carrying multimedia services. The power level allocation is firstly investigated to meet each call＇s Bit Error Rate （BER） requirement, then the system capacity is defined from the conditions lbr the existence of the physical meaning of these power levels. Simulation results have shown that the capacity analyzing methods can be well used in the performance evaluation of the system accommodating heterogeneous services and the spectral efficiency of this scheme is higher than the existing ones.
基金supported by the Program for New Century Excellent Talents in University of China(NCET-11-1025)the NationalNatural Science Foundation of China(No.61162003,61163050,6126104)+1 种基金Qinghai office of science and technology(grant No.2012-Z-902)the Natural Science Foundation of Tianjin(No.10JCYBJC00600)
文摘The characteristics of underwater acoustic channel such as long propagation delay and low bit rate cause the MAC(Medium Access Control) protocols designed for radio channels to be either inapplicable,or have low efficiency for UWSN(Underwater Sensor Network).We propose a hierarchical and distributed code assignment algorithm based on divisive probability function which can avoid conflict between spread codes with high probability,and provide a statebased MAC protocol for UWSN.Without RTS/CTS(Request To Send/Clear To Send) handshaking,each node maintains a neighbor table including state field,and packages are forwarded according to the state of the receiver,so it can avoid the interference caused by transmitting to a sending node in a half-duplex system and improve channel utilization.The design of power control minimizes the nearfar effect inherent in CDMA.Simulation results reveal that state-based CDMA protocol shows outstanding performance in throughput,delivery ratio and resource-consumption.
基金Project(2011)financially supported by Research Funds of Chonbuk National University,Korea
文摘An object segment similarity function is taken into account from the continuous media frames to measure the individual streaming profit of certain segment versions of a media object.Therefore,a new segment version-based transcoding(SVT)mechanism is derived for a quality of service(QoS)of client-centric media streaming in wireless mobile networks.The derived function utilizes the fuzzy similarity of certain segment versions of an object.This mechanism provides the effectiveness of reduction of the stream startup latency among segment versions,and the average access of each version.Thus,the proposed segment version transcoding mechanism reduces packet loss which in turn increases streaming performance and throughput.The performance of the partitioned segment versions is simulated and some segment versions are completed.The simulation results show that the proposed mechanism outperforms the other mechanisms in average cache hit ratio and in average startup latency ratio.
