Nov. 30, 2020
Combined with the performance characteristics of the VSAT PLus3 system, the current full mesh network technology has the following development directions:
With the rapid popularization of the TCP/IP communication protocol, PolarSat Communications in Canada launched an all-IP-based VSAT Network satellite communication terminal in 2008. Both the user interface and the satellite link adopt the IP protocol, and the TCP/IP acceleration technology is used in the satellite link to solve the TCP protocol delay problem. VSATPlus3 can be regarded as a wide area wireless router. It can support many IP-based protocols and functions, including: static routing, dynamic routing, QoS, VPN, SNMP, etc.
VSAT Plus3 satellite terminal adopts a large number of design concepts of software instead of hardware, which greatly reduces the volume and cost of the hardware platform, and improves the reliability of the equipment. Because the new coding algorithm and modulation method can be realized through software download, the service life of the hardware platform is greatly extended. For example, when the modulation mode is upgraded from QPSK to 8PSK, the hardware platform is not redesigned. The most advanced Mesh-ACM function is also achieved through software upgrades.
In the all-IP network, the previous on-demand distribution technology based on circuit switching is no longer suitable for business applications based on packet switching. The reason is that the satellite channel established by DAMA is symmetrical and the channel bandwidth is fixed during one setup. Therefore, DAMA technology is not suitable for IP data transmission based on packet switching. The reason is that IP data has obvious transceiving asymmetry and data rate instability. The solution is to adopt the dynamic bandwidth adjustment or BOD technology. BOD can dynamically adjust the channel bandwidth according to the actual data transmission rate after the satellite channel is established. In the VSAT Plus3 network, BOD is a full mesh network and two-way, CIR and EIR can be set by a single site. Because the BOD adjusts the bandwidth in the MF-TDMA network by increasing or decreasing the time slot, there is no need to cancel and establish the carrier, so it is seamless, so no instant data loss phenomenon will occur.
The VSAT Plus3 system realizes the real "0" network management hardware design for the first time, that is, there is neither network control center hardware equipment nor network management center hardware equipment in the network. Therefore, the terminal equipment of each site in the VSAT Plus3 network is the same. The network management terminal is an ordinary PC, without any special software, and can be connected to any VSAT Plus3 terminal in the network through the Ethernet interface to complete the network management task. Each VSAT PLus3 terminal has network management software, and all terminals in the network jointly complete the network control function. Because there is no special hardware, there can be multiple network management terminal PCs in the network at the same time, so as to realize the functions of hierarchical network management and sub-network management. The level of network management operations is identified by a password.
The VSAT Satellite uses a pseudo-synchronization method and uses a reference node to provide a network timing reference. The specific method is to first designate a node as the clock reference node, and the clocks of other nodes will track and lock the clock of the reference node, and always keep the error within the allowable range. It can be seen that the absolute accuracy of the clock of the reference node does not have to be very high, but the relative accuracy of the clock between each node and the reference node must be very high. After the MF-TDMA technology is adopted, the rate of each TDMA carrier is relatively reduced. At the same time, the VSAT Plus3 terminal uses the highest-level clock source in the industry, so the clock synchronization interval can reach about 20 milliseconds, which is also the frame length of TDMA The reason is usually 20 milliseconds. Further testing and statistics on the VSATPLus3 network found that its system clock synchronization is very stable and still has enough margin. Therefore, the VSAT Plus3 system has officially provided an option of 40 millisecond frame length to further improve the efficiency of TDMA.
At present, the cost performance of VSAT network equipment has reached a good level. Relatively speaking, the satellite bandwidth lease fee of the VSAT network has gradually become a significant part of the operating cost of the VSAT network. Therefore, how to further save space resources has become the main direction of VSAT technology development. The VSAT Plus3 system comprehensively adopts TPC coding, full mesh BOD, Mesh-ACM technology, ULPC and 40 millisecond frame length and other technologies, reaching an advanced level in terms of saving satellite resources.
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