Fixed radio links are frequently used for various purposes within telecommunications and broadcast networks. Usually the justification for using a radio link instead of optical fibre link relates to geography, speed of deployment and/or economics. Fixed radio links are often used to provide high capacity communication links between stations in a network supporting a different service (such as mobile communications): an application known as ‘backhaul’.
Given the criticality of the backhaul, in e g a mobile network, any given radio link needs to exhibit a very high reliability. I e, taken into account the statistical nature of the radio channel (rain fading, reflections, interferences…), every individual link needs to be properly planned, dimensioned and implemented, taking the characteristics of the actual radio link equipment, as well as the local radio environment, into account.
Due to the above, the performance characteristics in terms of immunity against channel anomalies have become a key criterion when selecting radio link equipment for a network. Modern radio link equipment contains advanced signal processing, adaptive link optimization and support for a variety of link configurations – all with the aim to secure high capacity communication with the highest possible reliability.
A consequence of the ever increasing performance and functionality of radio link equipment is that the tools for test and verification need to keep a similar development pace: A product claim that can’t be verified by proper testing has little value and, as a minimum, the characteristics and performances of the radio link equipment must be demonstrated to be compliant with the standards and recommendations of national and international organizations such as ETSI, FCC, ITU and CEPT.
- Essential verifications that must be performed, includes the analysis of the detection capability of the receiver. Typical examples of these measurements are:
- Receiver sensitivity (carrier to noise characterization)
- Receiver performance in the presence of dynamic, flat fading (adaptive modulation, fast recovery)
- Immunity against disturbing signals (co-channel and adjacent channels as well as CW)
- Immunity against Multipath Fading (signature verification)
The Ranatec RI 241 is a multichannel, high performance, fading radio channel emulator, designed to fit into any general purpose, radio link test bench. It is intended as a generic test tool, all through the product lifetime of a radio link product:
- As an efficient evaluation tool during the design phase
- As an accurate verification instrument during product qualification
- As an integer part of a streamlined factory test set-up
- As a powerful troubleshooting tool in order to reproduce in-field events
The Ranatec RI 241 can be equipped with up to 4 completely independent fading channels. Each channel can emulate multipath fading according to the Rummler’s model. A built-in C/N generator with AWGN is available as an option. The modulator concept and the fact that the main functionality is digitally implemented by means of an FPGA allows for smooth upgrade of the installed base.
The RI 241 Fading Emulator is designed to replace the obsolete Agilent 11757B Multipath Fading Simulator. In addition to terrestial radio link testing, RI 241 may also serve as a verification tool for satellite communications.