The problem faced by wireless devices is that in a facility or campus, each wireless application usually needs its own wired infrastructure access point and other wireless transmission sources. The result is fragmented and redundant infrastructure. This infrastructure creates a chaotic RF environment and hinders wireless applications. An indoor passive distributed antenna system (DAS) enjoying broadband brings a new order to this chaotic environment, thus making high-quality wireless service possible. The antenna system can support various wireless technologies provided by different manufacturers in a wide frequency range. The core of passive antenna is integrated access equipment (IAD). Cellular /PCS, two-way radio and paging systems are connected to IAD through base stations or wireless repeaters. Various services are combined and filtered, and then transmitted through wired trunk lines or trunk lines (usually 7/8-inch coaxial cables) connecting all floors of the building. The carefully designed antenna array is led out from the main line of each floor to transmit RF energy. Antenna array includes radiation coaxial cable, standard coaxial cable, directional antenna and omnidirectional antenna. Antenna arrays are arranged layer by layer to cover specific areas and keep RF signals in the facility. Applications such as WLAN, building automation and security systems usually serve local areas, so they are added to passive DAS layer by layer. Local applications connect through application portal devices such as IAD. The application portal integrates RF energy from multiple sources and adds these signals to the antenna array. This method requires detailed field investigation and in-depth understanding of building structures and materials. Passive DAS can handle multiple frequencies for voice and data integration, building automation and security services. Base stations and/or wired repeaters from multiple service providers are centralized in the main telecommunications room. Access points are centrally placed in the locked middle distribution facility area on each floor. The stacking area can cover 500,000 square feet of sites. As needed, optical fiber repeaters provide signals for more areas that need larger IAD facilities. In fact, passive DAS is a huge and efficient antenna, which can distribute RF energy evenly to all corners of the building. DAS does not require amplifiers or repeaters. All components of the system are passive: they are non-mechanical and do not need power. Therefore, the system does not need monitoring and has high reliability. It is a public system, just like power distribution and HVAC (heating, ventilation and air conditioning) power distribution system. DAS follows the IEEE 802. 1 1 standard. They also support standards such as CDMA, GSM, IDEN (Integrated Digital Enhanced Network), TDMA, GPRS and UMTS. They can support a continuous broadband frequency range from 400MHz to 2.5GHz. This frequency range covers most indoor wireless applications and emerging technologies. At the same time, a single infrastructure supporting multiple applications will reduce interference and provide reliable wireless coverage in buildings.