The maritime satellite communication network is a globally covered communication network. Comparatively, the emergency traffic broadband VSAT satellite system corresponds to a dedicated network under the maritime satellite communication network, with stronger personalization. The maritime satellite communication network and the emergency traffic broadband VSAT satellite communication network can be vividly compared as follows: A maritime satellite is equivalent to entering an incident site with a mobile phone, whereas VSAT is equivalent to moving a base station to the site.
As a means of communication, maritime satellites use standardized bandwidth allocation, while VSAT satellite system is used for trunk transmission. The main difference between the two lies in bandwidth. The communication functions of maritime satellites include voice communication, fax communication, message communication, and high-speed data communication. Abroad, its high-speed data communication has now entered theISDN communication stage, which is the Integrated Services Digital Network phase. However, since the terrestrialISDN communication phase in China was leapfrogged, there is a lack of coordination in linking maritime satellites with terrestrial networks, resulting in limitations on the use of maritime satellites. Even theBGAN maritime satellite, which claims unrestricted calling and Internet functionality, can reach a maximum speed of only 492 kilobytes per second. Compared to the standardized bandwidth allocation of maritime satellites,VSAT offers greater bandwidth flexibility, allowing for adaptable bandwidth allocation based on communication needs. The bandwidth can reach up to1M, or even2M, making concurrent data communication possible.
Maritime satellite hardware investment is low, but communication costs are high. In contrast, VSAT satellite system requires significant hardware investment, but has relatively low communication costs. Although the hardware construction cost of maritime satellites is lower than that of VSAT, the usage cost of maritime satellites is far higher than that of VSAT for long-term video monitoring, data transmission, and Internet access. The cost of using maritime satellites for large volumes of data transmissions and Internet services may become astronomical. In comparison, the "annual" or "monthly" service plans of VSAT are much cheaper than the per-traffic and per-time charges of maritime satellites.
In terms of application range, there is a complementary relationship between maritime satellites and the VSAT satellite system. The maritime satellite service range has already achieved global coverage, whereas VSAT does not cover as extensively as maritime satellites. Thus, from the most economical and practical perspective, it is recommended to use VSAT within its coverage area and maritime satellites outside its coverage. The VSAT satellite segment uses Asia-Pacific 6Ku andC band satellite resources to meet the communication needs of the transportation industry, including highways, ships, and land vehicles. Ku band can cover land areas and near-sea regions up to 12-13 kilometers, with higher satellite signal power but is prone to interruption by adverse weather conditions such as rain and snow; C band has a broader coverage range, with fewer requirements for maritime usage but is more susceptible to interference when used on land. Therefore, generally, C band is used at sea, andKu band is used on land.
In other words, the VSAT entire network small stations are online 24 hours a day, thus forming a normalized emergency communication network state. To ensure this normalization operation, the VSAT satellite system not only has Ku and C bands, but also has one primary and one backup for the antennas of both Ku and C bands in its hardware construction. Each pair of antennas has primary and backup power amplifiers and low-noise amplifiers, ensuring sufficient hardware resources, whether during use or when expanding more resources.
