Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to co...Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to code the composite pack- channels efficiently. For the composite fading environ- ment with muhiple receivers, receivers experience different fading at any time. It＇ s very important to code the composite packet so that intended receivers are in good channel qualities, because in- tended receivers in deep fading have little opportunity to receive the composite packet correctly. Hence, we propose a novel composite packet coding principle of maximizing the total SNR of intend- ed receivers. Since the proposed principle is an NP-complete problem, an efficient heuristic algo- rithm with low complexity is given for finding a suboptimal solution. Simulation results show the heu- ristic based scheme achieves higher transmission efficiency than other network coding-based schemes due to the multi-user diversity gain.展开更多
The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the pe...The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the performance and identifying its bottleneck in such systems can shed light on the system design and performance optimization. TCP performance of a commercial crowdsourced live streaming system is examined by analyzing packet-level traces collected at streaming servers. TCP stalls that heavily hurt the Qo E of user have been identified. In particular,the TCP stalls account for as much as 31. 6% of the flow completion time for upload flows and result in abandonment of upload on the corresponding channels. Stalls caused by timeout retransmissions are further dissected and timeout retransmission characteristics are revealed to be dependent on the video encoding methods. These findings provide new insights in crowdsourced live streaming systems and can guide designers to improve the TCP efficiency.展开更多
In Cognitive radio ad hoc networks （CRAHNs）, the secondary users （SUs） or cognitive radio nodes （CRs） are always equipped with limited energy and have a high error probability of data transmission. To address th...In Cognitive radio ad hoc networks （CRAHNs）, the secondary users （SUs） or cognitive radio nodes （CRs） are always equipped with limited energy and have a high error probability of data transmission. To address this issue, we first describe the network utility under energy constraint as a max-min model, where the re-transmission strategy with network coding is employed. Additionally, the expression of retransmission probability is presented in terms of power and bit error rate （BER）. Moreover, since the max-min model is non-convex in both objective and constraints, we use a normal- form game to find a near-optimal solution. The simulation results show that the proposed approach could achieve a higher network utility than the compared approaches.展开更多
In this letter, a Function node-based Multiple Pairwise Keys Management (MPKMF) protocol for Wireless Sensor Networks (WSNs) is firstly designed, in which ordinary nodes and cluster head nodes are responsible for data...In this letter, a Function node-based Multiple Pairwise Keys Management (MPKMF) protocol for Wireless Sensor Networks (WSNs) is firstly designed, in which ordinary nodes and cluster head nodes are responsible for data collection and transmission, and function nodes are responsible for key management. There are more than one function nodes in the cluster consulting the key generation and other security decision-making. The function nodes are the second-class security center because of the characteristics of the distributed WSNs. Secondly, It is also described that the formation of function nodes and cluster heads under the control of the former, and five kinds of keys, i.e., individual key, pairwise keys, cluster key, management key, and group key. Finally, performance analysis and experiments show that, the protocol is superior in communication and energy consumption. The delay of establishing the cluster key meets the requirements, and a multiple pairwise key which adopts the coordinated security authentication scheme is provided.展开更多
文摘Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to code the composite pack- channels efficiently. For the composite fading environ- ment with muhiple receivers, receivers experience different fading at any time. It＇ s very important to code the composite packet so that intended receivers are in good channel qualities, because in- tended receivers in deep fading have little opportunity to receive the composite packet correctly. Hence, we propose a novel composite packet coding principle of maximizing the total SNR of intend- ed receivers. Since the proposed principle is an NP-complete problem, an efficient heuristic algo- rithm with low complexity is given for finding a suboptimal solution. Simulation results show the heu- ristic based scheme achieves higher transmission efficiency than other network coding-based schemes due to the multi-user diversity gain.
基金Supported by the National Basic Research Program of China(2012CB315801)the National Natural Science Foundation of China(No.6157060397)
文摘The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the performance and identifying its bottleneck in such systems can shed light on the system design and performance optimization. TCP performance of a commercial crowdsourced live streaming system is examined by analyzing packet-level traces collected at streaming servers. TCP stalls that heavily hurt the Qo E of user have been identified. In particular,the TCP stalls account for as much as 31. 6% of the flow completion time for upload flows and result in abandonment of upload on the corresponding channels. Stalls caused by timeout retransmissions are further dissected and timeout retransmission characteristics are revealed to be dependent on the video encoding methods. These findings provide new insights in crowdsourced live streaming systems and can guide designers to improve the TCP efficiency.
基金This work was supported in part by the Research Fund for the Doctoral Program of Higher Education of China under Grant 20122304130002,the Natural Science Foundation in China under Grant 61370212,the Fundamental Research Fund for the Central Universities under Grant HEUCFZ1213 and HEUCF100601
文摘In Cognitive radio ad hoc networks （CRAHNs）, the secondary users （SUs） or cognitive radio nodes （CRs） are always equipped with limited energy and have a high error probability of data transmission. To address this issue, we first describe the network utility under energy constraint as a max-min model, where the re-transmission strategy with network coding is employed. Additionally, the expression of retransmission probability is presented in terms of power and bit error rate （BER）. Moreover, since the max-min model is non-convex in both objective and constraints, we use a normal- form game to find a near-optimal solution. The simulation results show that the proposed approach could achieve a higher network utility than the compared approaches.
基金Supported by the National Natural Science Foundation of China (No. 60475012)
文摘In this letter, a Function node-based Multiple Pairwise Keys Management (MPKMF) protocol for Wireless Sensor Networks (WSNs) is firstly designed, in which ordinary nodes and cluster head nodes are responsible for data collection and transmission, and function nodes are responsible for key management. There are more than one function nodes in the cluster consulting the key generation and other security decision-making. The function nodes are the second-class security center because of the characteristics of the distributed WSNs. Secondly, It is also described that the formation of function nodes and cluster heads under the control of the former, and five kinds of keys, i.e., individual key, pairwise keys, cluster key, management key, and group key. Finally, performance analysis and experiments show that, the protocol is superior in communication and energy consumption. The delay of establishing the cluster key meets the requirements, and a multiple pairwise key which adopts the coordinated security authentication scheme is provided.
