Networking scheme based on 3G wireless IP network
In an emergency scenario, a mobile cluster base station can quickly expand communication coverage or enhance network capacity at the location of an event. Due to the high mobility and ease of deployment of wireless links, they have become the preferred choice for setting up mobile base stations. This paper examines and compares the advantages and disadvantages of using microwave, satellite, and 3G networks as links for clustered mobile base station networking, based on the specific needs of different organizations. It concludes that the 3G wireless IP network offers significant benefits over other methods and provides a detailed explanation of its implementation, along with real-world application examples.
I. Overview
In recent years, TETRA systems, led by manufacturers like Motorola, have gained widespread recognition among public security, transportation, enterprise, and government users in China. Following successful support during the Beijing Olympics, the Armed Police Forces have further promoted the development of such technologies. Mobile cluster base stations help address signal blind spots or sudden events, enabling rapid response wherever needed. They serve as a crucial complement to fixed cluster network infrastructure for public safety users. Typically, TETRA base stations use TDM (Time Division Multiplexing) links to connect to the network. However, telecom operators usually only provide TDM framing services within their backbone networks, making it difficult for mobile base stations to access these networks through standard connection methods. Therefore, achieving fast and stable networking for mobile base stations has become a critical challenge for cluster system builders.
[Image: TETRA mobile base station development through 3G wireless IP network networking]
2. Introduction and Comparison of Current Networking Methods
Mobile cluster base stations often rely on microwave or satellite links, but both approaches come with notable limitations (see Table 1 for details). As shown in Table 1, microwave and satellite equipment tend to be large and cumbersome, making them difficult to transport and deploy on vehicles. In contrast, the 3G network offers better penetration capabilities, smaller and more cost-effective equipment, and long-term stable operation. However, the 3G network uses the TCP/IP protocol at the end, which is incompatible with traditional TDM-based cluster base stations. Therefore, protocol conversion is required to enable compatibility.
Three Networking Solutions Based on 3G Wireless Networks
Personnel from the Communications Department of the Hainan Corps of the Armed Police proposed a TDM line solution based on a 3G wireless IP network.
Basic Principle: A protocol conversion device is used to convert data packets between the IP network and the private network's TDM frame structure. Adjusting the parameters of the mobile base station and the 3G device allows the cluster networking equipment to adapt to wireless transmission delays, enabling the mobile cluster base station to interconnect with the fixed cluster network.
Implementation Conditions: The base station must have 3G wireless network coverage, and the telecom operator should provide a dedicated VPN channel between the WCDMA wireless DTU and the PCM aggregation device. The setup includes one integrated communication vehicle equipped with a cluster base station, two RAD IPMUX units, and one 3G wireless Internet access device with a SIM card.
Equipment Connection Plan:
Install Unicom WCDMA wireless DTU equipment on the integrated communication vehicle and use WCDMA VPDN technology to create a dedicated VPN channel between the WCDMA wireless DTU and the PCM aggregation device. Between the mobile cluster base station and the wireless DTU equipment, WCDMA APN equipment and PCM multiplexing devices are connected, with a protocol conversion device installed between them. This enables the in-vehicle cluster base station to access the PCM device and finally connect to the Virtual Chassis Center (MSO).
The device connection scheme is illustrated in Figure 1:
[Image: TETRA mobile base station development through 3G wireless IP network networking]
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