About Distributed Antenna Services
Distributed Antenna Services is a Division of PCM, Inc. PCM was established in April 1988 and formed the Distributed Antenna Services Division in 1999. PCM-DAS began primarily a turnkey contactor to companies like ADC and LGC for the first ten years. PCM-DAS has installed system in nearly all continental United States in a wide variety of venues. Hospitals are the primary focus of our efforts since we have all of the tools required by health care facilities such as HEPA tenting. But, installed projects also include enterprise office buildings, airports, manufacturing facilities, universities and public service buildings such as police and fire stations. Since the original turnkey contractor approach we have branched out into a more direct relationship with carriers such as AT&T, Verizon and T-Mobile with preliminary design and budgeting, final design, installation and commissioning offered.
About Distributed Antenna Systems (DAS)
Cellular technology has become the leading growth industry for the past couple of decades. Now, nearly everyone has a cellular telephone. In 1997 less than 20% of the adult population had cell phones compared to 97% today. The outside, or ‘Macro’, continues to expand to meet the needs of the subscribers. However, macro Radio Frequency (RF) coverage often cannot penetrate adequately into buildings and the result is no signal, or weak signal. That’s where the Distributed Antenna System (DAS) becomes important.
What is a DAS?
“Cellular” has become a general term for wireless communications but there are actually many different forms. CDMA, LTE, GSM, PCS, UMTS and iDEN are all wireless communication formats and fall into the licensed frequency spectrums. The right to broadcast on the licensed frequencies is regulated by the Federal Communications Commission (FCC) and frequency blocks are sold to carriers like AT&T, Verizon, T-Mobile, Sprint and others. Many Distributed Antenna Systems can accommodate multiple frequency spectrums but permission must be granted by the owner of the frequency block. Some Distributed Antenna Systems can also broadcast unlicensed frequencies like 2.4GHz or 5.6GHz wireless LAN or wireless broadband often used for wireless computer communications. Public safety frequencies are also often broadcasted with a DAS. Proper planning and design is critical for systems supporting multiple frequencies, or “neutral host systems” because each frequency propagates differently when passing through free space, walls or other obstructions.
The DAS basically distributes RF throughout a building using low power antennas. The source, or “head end” RF signal is obtained either by a “donor antenna” or a Base Transceiver Station (BTS). The donor antenna pulls the RF signal off of the Macro and is typically mounted on the rooftop with an orientation towards the Macro site desired. The BTS is typically located in the basement or lower part of the building where it has access to T-1 land lines via typical copper or fiber from the local telephone company.
Donor antennas are normally used in smaller sites. Since it adds traffic to the macro site, it is not desirable for larger, higher traffic sites. The BTS basically turns the DAS into its own cell site. Proper design and installation are critical to prevent degradation to the macro and overall network performance. Both systems are comprised of similar components within the building. Smaller systems generally are coax based throughout the system with a Bi-Directional Amplifier at the head end with coaxial cable to each low power antenna. Larger systems for campus environment or large buildings use fiber optic cabling to connect expansion units or remote units which then connect to the low power antennas using coaxial cable. Using the low power antennas actually lowers the RF radiation emitted from the individual cell phones. Net result to a subscriber is longer battery life and less RF radiation since their cell phone radio does not need to ‘power up’ to reach the cell site due to poor signal.