The throughput of traditional TCP degrades drastically in high speed satellite links, where the characteristics of long round trip time (RTT) and high bit error rate (BER) happen together. Two typical improved algorithms, Hybla and Westwood, are designed to solve the problems of long RTT and high BER respectively. TCP-HW which combines the advantages of Hybla and Westwood is proposed in this paper, on the basis of consideration of both long RTT and high BER. At slow start and congestion avoidance phase, TCP-HW adopts a radical congestion window (cwnd) growth policy to eliminate the low data transmission rate bring by long RTT as Hybla does. At fast retransmit and fast recover phase, TCP-HW updates the cwnd according to the estimated available bandwidth in Westwood to avoid the frequently unnecessary reduction of cwnd due to high BER. There, the cwnd can be kept large enough to achieve high throughput. Simulation results in NS2 indicate that the change of RTT and packet error rate (PER) has little impact on TCP-HW and the bandwidth utilization of TCP-HW can reach more than fifty percent in the 1Gbps GEO satellite link with 500ms RTT and 0.001 PER. In addition, TCP-HW still have good fairness.

In order to solve the problems of the existing broadband power line carrier communication standard IEEE1901.1 data link layer protocol network, multiple primary nodes receiving the beacon will send connotation entreaty message, and CCO will send an association sanction message proximately after receiving the message to confirm their character the central coordinator CCO association confirmation message reply is not timely to reduce the success rate of network access, high network access delay and control overhead. Based on the characteristics of BPLC carrier network, Proficient networking instrument of broadband PLC built on adaptive multicast PNP-BPLC is proposed in this paper. The simulation results show that adaptive multicast is used when CCO replies to the primary station, which can excellently recover the success rate of low-voltage PLB carrier communication nodes, decrease the network access delay and cut the network control overhead. Finally we used to OPNET simulation software to prove simulation result.

In wireless sensor networks, data transmission quality and energy efficiency are closely related to link quality indicator. In order to improve the performance of Multipath Routing protocol, this paper proposes a LqiRings Routing protocol based on link quality and hops between nodes. In the routing discovery stage, LqiRings Routing does not take hops as the only factor in routing decision-making, but considers hops and link quality as two factors, and determines the optimal path by adjusting the weights between them. The LqiRings Routing protocol, Multipath Routing protocol and Hop Counts Routing protocol are simulated and analyzed in Castalia simulator. The experimental results show that the LqiRings Routing protocol proposed in this paper has higher packet delivery rate and lower average energy consumption under the same environment. 1

In order to improve the packet delivery rate of wireless sensor networks, this paper proposes a routing protocol based on path signal strength (PSSR) in wireless sensor networks. In the process of routing discovery, the node can get the link quality information through the radio signal strength received by the physical layer and calculate the path signal strength from sink to the current node to select a path with higher path signal strength and fewer hops. Omnet network simulation software and castalia simulation framework are used to simulate PSSR. The simulation results show that PSSR can effectively improve the packet delivery rate. 1