Development of Communications Shelters

A communications shelter is a box that provides a suitable working environment for telecom equipment. A good shelter should be wind-proof, water-proof, and dust-proof. It should also be secure from theft, and easy to pack. Shelters are widely used for base station deployment as they have advantages such as fast construction, low cost, modular design, and easy installation that make them preferable to equipment rooms. Several systems and sub-systems usually comprise a shelter box, including the cabin system, alternating current (AC) distribution system, and monitoring system (shown in Figure 1).

Development Trends

Customization

Traditionally, shelters have been applied to BTS sites but not MSC sites (due to size limitations). However, when used for small-sized base stations such as the BS8800, there is often room to spare. To better fit specific base stations, shelters need to have a customized design.

In a wireless network project for Orange Madagascar, ZTE customized a “Super Shelter” according to the actual conditions and requirements of the site (see Figure 2). With approximate dimensions (7600×5700×3000mm), the “Super Shelter” boasts simple and elegant shape, modular design, and is easy to transport and install. Air conditioners and fans are automatically controlled according to indoor/outdoor temperature changes, and this reduces OPEX.

Function division

In a traditional shelter, infrastructure equipment and battery packs are often located together. With technological development, infrastructure equipment has been designed to be more energy-efficient and more adaptive to harsh temperatures (50˚C). Battery packs, however, cannot endure such high temperatures because of technical constraints.

Ambient temperature greatly impacts the service life of batteries, especially lead-acid batteries which are in widespread use today. To extend battery life, traditional shelters are usually equipped with air-conditioners. But this results in increased OPEX because air-conditioners are configured according to the size of shelter body and the heat generated by infrastructure equipment. There are different temperature requirements for batteries and infrastructure equipment.

To effectively reduce OPEX, ZTE has launched a “Diet Shelter” that provides different temperature control solutions for infrastructure equipment and batteries. As shown in Figure 3, the diet shelter has three cabinets, each with a separate door. Temperature controllers such as heat exchanger, air-conditioner, and thermal electric coolers (TEC) can be installed on the door of a separate function area. These can be configured to meet different temperature requirements.

The diet shelter can reduce energy consumption at a base station site by between 20% and 60%. It can be lifted or carried as a whole—or assembled on site—and with side and back expansion capability, it is flexible to various spacial constraints. The “Diet Shelter” is the best choice for operators wanting to extend battery life and reduce energy consumption at base station sites.

Emergency communications

Communications shelters are designed for fast construction of base station sites. Although shelters have distinct advantages over equipment rooms, they must also be assembled onsite. It takes time to wire and install control systems inside a shelter body. Traditional shelters are therefore not optimal for emergency communication scenarios. For emergency situations, integrating all systems inside the shelter and reducing onsite installation and wiring time is imperative.

ZTE has developed a “Container Shelter” that integrates the cabin system, AC distribution system, and monitoring system, as well as communications equipment, generator set, and lifting pole (holding pole or guyed tower). During the Yushu earthquake in April 2010, China Telecom adopted ZTE’s container shelter to rapidly restore communications services (see Figure 4).

Cost Reduction Options

Communications shelters are widely used in base station deployment, and reducing shelter costs means saving costs in base station construction. The following cost-saving options are available.

Material selection

ZTE’s shelters are constructed using three types of materials: fiberglass-reinforced plastic-skinned polyurethane; prepainted galvanized steel-skinned polystyrene; and prepainted galvanized steel-skinned polyurethane. Plastic-skinned polyurethane foam sandwich panels are designed for use in harsh environments; for example, by the seaside, or in moist, acidic, or alkaline environments. So they are the most expensive option. Steel-skinned polystyrene foam panels are used in areas with moderate temperatures and a dry climate. They are the cheapest option. The price of steel-skinned polyurethane foam panels lies between these two. Materials for shelter construction are selected according to the specific environmental and budget constraints of operators.

Internal layout

For equipment that requires rear-end operation and maintenance, the shelter must allow some space for operation and maintenance. But for equipment that requires front-end operation and maintenance, the shelter can be placed with its back against a wall. In this case, space needed for operation and maintenance can be saved, and a smaller sized shelter constructed.

Function division

From perspective of OPEX, a diet shelter with function divisions is attractive. It provides different temperature control solutions for different equipment, and this reduces equipment OAM costs.

Combination

Combining the shelter and tower makes efficient use of site area. For example, a co-based tower and shelter solution allows the shelter and tower to share the same ground space (see Figure 5). Minimizing site area reduces site construction costs.

Conclusion

Communications shelters have become the preferred choice in base station deployment. Fast construction, low energy consumption, and environmental protection will become development trends for future communications shelters.