Chang Guang Satellite Technology Co., Ltd.

Composition Of Satellite Ground System

The satellite communication ground system generally adopts a star structure consisting of a gateway station, a user station, etc. The capacity of the gateway station is large, and it is generally equipped with a large aperture antenna to connect the ground network and satellite feed beam. The user station communicates with the gateway station through communication satellites. Generally, the traffic transmitted from the user station to the gateway station is small, while the backhaul data traffic is large. In addition, the satellite communication ground system also includes a network operation center for managing satellite networks and user services.

The gateway station is used to connect the satellite and the ground network. It is mainly composed of RF subsystem and baseband subsystem. The baseband subsystem also includes satellite modem, access service network, web accelerator, network routing and security system.

1. RF subsystem

The RF subsystem of the gateway station includes antenna, RF components, IF components, etc. The antenna size of the gateway station is relatively large, with a diameter of several meters to more than ten meters; RF components include filters, low noise amplifiers, power amplifiers, etc. Intermediate frequency components are mainly up and down converter components. The RF subsystem exchanges IF signals with the baseband subsystem, which is used to convert RF signals sent from satellites to IF, and up convert IF signals sent from the baseband subsystem to RF, amplify and radiate them to satellites.

2. Baseband subsystem

Modem system: manage and control the data flow between the user terminal and the gateway router and server, and also manage the power, frequency and satellite network bandwidth of forward and reverse links.

Access service network (ASN): ASN is responsible for authenticating and authorizing user access, and implementing quality of service (QoS) management.

Web accelerator: software used to improve the throughput and end-user performance of HTTP and TCP based applications. The accelerator server is located in the gateway, and the client software is embedded in the user terminal.

Network security and routing: This subsystem implements traffic security and QoS policies, and routes all management and data traffic to the target network destination. It includes routers, L2/L3 switches, firewalls, traffic shapers, and AAA, DHCP, TFTP, and NTP servers.

3. User station

Typical subscriber stations mainly include three parts: antenna, outdoor unit (ODU) and indoor unit (IDU). The outdoor unit is composed of feed source, receiving equipment (low noise amplifier and down converter) and transmitting equipment (high power amplifier and up converter). The outdoor unit is connected to the indoor unit through the intermediate frequency connecting cable. The indoor unit includes baseband receiving equipment (intermediate frequency down converter and demodulator), baseband transmitting equipment (intermediate frequency up converter and modulator), etc. The antenna of the subscriber station is generally about 1m, and the solid-state power amplifier is used.

4. Network operation control system

The network operation control system generally manages satellite networks and user services through the network management system (NMS), operation support system (OSS) and business support system (BSS). Its main functions include: customer subscription and billing, automatic non-contact resource allocation, ensuring that services are provided according to the end-user service level agreement, and implementing central control over multiple remote gateways and satellites.

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