What are the needs and requirements for consistent in-building cellular and public safety signal converage in hospitals today? Ideally, digital signal processing and narrowband filtering should be used for obtaining quality cellular and PCS signals. The selection of the overall macro in-building design is important, together with the correct selection of the individual components. Together these choices will provide mission critical or life critical communications for cellular, PCS and public safety communications. There have been traditionally two ways to bring the cellular and PCS signals inside a building environment: either use a dedicated micro-cell base transmitter station (BTS), or a repeater. Most healthcare environments can get by with a traditional repeater due to capacity requirements. It is important to go to the technology that can take the signal or multiple signals from the macro (outside environment), to repeat and amplify this signal inside the building environment. It is this critical piece at the front end that determines the interplay of signals throughout. Carriers in some instances mandate digital repeaters, especially as far as the PCS band is concerned. They only want to be re-radiating their own spectrum. Many traditional in-building systems used broadband repeaters, which essentially applified all the carrier signals to include harmonics. The advantage of using digital repeaters is that they allow you to precislely control which frequecies you amplify and repeat. This actually provides better quality of signals without the risk of voice or data signal quality going down. Some broadband signal repeaters automatically take a broad range of frequencies and amplify all of them, thus including the undesired frequecies, such as harmonics and interfering frequencies. During a major emergency, often many first responders – ambulances, police, fire, and EMTs – could arrive at the healthcare facility at once and could be trying to communicate at the same time. In this case the signal strength form the broadband signal repeater may decrease when it is most required. There also have been instances when broadband singal repeaters interfered with mission critical requirements. These situations should be mitigated as many public safety and P25 networks move to the the new NPSPAC band 806-809/851-854MHz. How these changes affect you depends on which part of the country and which wave of re-banding that you are in. Frequency agility is the key here. Frequency agility includes the ability to change filter configurations to support virtually any passband combination within a specific set of wireless frequencies. This agility solves the problem of rebanding or augmenting of existing channels requiring a forklift repeater upgrade. Mitigation of adjacent channel interference should be provided by allowing the fine tuning of band edeges to eliminate or mitigate adjacent band interferers. There should be the ability to provide custom filter sets and filter plots prior to implementation of distributed antenna systems.
Pictured is a digital repeater designed for use within enclosed structures where sufficient signal strength from local cell sites to operate cell phone or data cards is limited or unavailable. Digital signal processing is utilized to achieve the highest level of performance and spectrum agility. DSP filtering provides unmatched selectivity, which helps to overcome difficult RF problems such as adjacent channel interference.
