DTS Communications, Inc. is a company dedicated in providing RF engineering services that create reliable, high-quality wireless networks that adhere to stringent design procedures and project timelines. The complete process involves working with site acquisition and zoning restrictions, evaluating site design configurations, and detailing all site parameters to allow for rapid construction and installation. DTS Communications provides several services to help with the design with RF Engineering your fixed and mobile networks:
Reliability Analysis
A reliability analysis predicts the operational performance of a link or system of links. Statistical models are used to predict the annual outage time, unavailability percentage, and reliability percentage. The analysis provides critical verification that the selected link budget parameters are sufficient to support the intended communications. Microwave paths are often designed for "five nines" reliability, or a reliability of 99.999%. This reliability corresponds to an annual outage time of only about 315.5 seconds. Depending on the requirements of your system's application, however, the required reliability could be higher or lower than 99.999%. Service outages can be caused by mulitpath conditions and rain. Multipath propagation occurs when copies of a signal arrive at a receiver at different times as a result of having followed different paths through the atmosphere.
If they are out of phase, these signals may cancel at the receiver causing an outage. Rain outages occur when raindrops attenuate the microwave signal power below a usable level. The attenuation becomes significant as the size of the raindrops becomes comparable to the wavelength of the signal. Rain attenuation increases as raindrops become larger, rain becomes more frequent, and the frequency of the link becomes higher (the wavelength becomes smaller). Typically, rain outages are only a concern in frequency bands above 10 GHz. Multipath outage, which occurs independently in each direction of a path, is calculated for each direction, and the two results are added to produce the two-way outage. Rain outage, which affects both directions of a path at the same time and is therefore already a two-way result, is calculated once for the path direction with the lower fade margin.
Intermodulation Study
Aesthetic and cost concerns make it desirable for multiple operators to share communications sites.
Unfortunately, radio systems at shared sites may cause harmful interference to each other. Potential interference mechanisms are: Transmitter Intermodulation, Receiver Intermodulation, Transmitter Noise, Receiver Desensitization, Harmonic Interference, and Spurious Interference.
Whenever a radio system is added to a site, a collocation analysis should be performed to determine whether the new system will cause or suffer from harmful interference. The principal component of a collocation analysis is an intermodulation study. The mixing of transmitter frequencies at a site produces intermodulation Interference. As a result of system nonlinearities, these frequencies mix to produce other "intermodulation" frequencies that are potential sources of interference to the receivers at the site. The first step in the intermodulation analysis is the generation of an intermod "hit list". Using stored formulas, the analysis software combines the frequencies of the transmitters at the site to determine the intermod frequencies that may be generated. When an intermod frequency is sufficiently close to the frequency of one of the receivers at the site, the program reports a "hit". These intermod "hits" are then analyzed further to calculate predicted interference levels and determine whether or not harmful interference will occur. Transmitter Intermodulation occurs when signals enter a transmitter and mix, and the resulting intermod frequencies are re-radiated by the transmitting antenna. Receiver Intermodulation occurs when signals enter a receiver and mix, and the resulting intermod products then appear at the receiver's demodulator input. In addition, Transmitter Noise and Receiver Desensitization are interference mechanisms to be studied. Transmitter Noise is the name given to a transmitter radiating power outside its assigned channel bandwidth and causing co-channel interference to a nearby receiver.
Receiver Desensitization is the name given to interference power from a nearby adjacent channel transmitter passing through a receiver's filters and degrading the noise floor. Transmitter Noise and Receiver Desensitization are usually only a problem when transmitters and receivers are operating on adjacent frequencies. Also considered in the collocation analysis are Transmitter Harmonics which are integer multiples (2, 3, 4...) of the transmitter frequency. Produced by non-linearity of the transmitter system, primarily the RF power amplifier, these harmonics are potential sources of interference to nearby receivers. Finally, any known spurious emissions of the transmitters at a site are analyzed as possible interference sources to the receivers sharing the site.
Propagation Study
A propagation study predicts the RF Signal Strength from a proposed transmitter site to points in its vicinity. Path Loss prediction calculations are performed using one of several propagation models that characterize the area around the site based on terrain and morphology characteristics. The RF Signal Strength is then calculated based on transmit parameters of the site. The study is used to determine the reliable service area of a site or system, and it is an important step in the site selection or site evaluation process. The results of the study are displayed on coverage maps depicting RF Signal Strengths over the area of interest. DTS Communications, Inc. provides customized coverage maps based on customer-defined parameters, signal level thresholds, and confidence levels. Customer-defined parameters that affect signal strength include:
Signal strength thresholds are used to identify different types of service requirements (in-car portable, mobile, in-building portable, etc.). Confidence level refers to the statistically determined percentage of time the received signal is at a level at or above the calculated signal strength.
The predicted signal levels are displayed as a coverage map with different colors representing the desired signal level thresholds for the various types of service. Coverage maps can be produced for an individual site or a composite of multiple transmitter sites on the same map. Additionally, maps can be provided to compare different design scenarios. For example, different antenna centerlines or antenna types can be modeled for the same site, or different candidates can be modeled for the same desired coverage area. The resulting maps can be compared to determine the best candidate or RF design scenario.