Overview
Remote Radio Heads, short RRH, are becoming increasingly important in almost all wireless communication systems. Today, they are often designed and manufactured by companies with significant experience in designing and building RF components, but with little or no experience in the baseband processing and upper layer design of a wireless communication system. Such vendors typically have no baseband processing unit available and are thus significantly hindered when developing and testing their RRH solutions. But even major network equipment vendors require independent development of their baseband units and their RRH and require test facilities for the RRH without having to fall back on using the baseband unit as test vehicle.
One of the major drawbacks of using a real baseband unit for RRH testing is the lack of reproducability and predictability of the signals, making them unsuitable for many tests and calibration efforts.
NORI Introduction
NORI addresses this challenge by providing the capability of playing pre-defined baseband data for the downlink and capturing uplink baseband data through your RRH via the optical interface. NORI supports the following standards:
- CPRI
- OBSAI
In downlink, several test models can be stored and transmitted. Test data can be either taken from standard test models, or from self-designed test data for specific tests. Cyclic repetition of the downlink data enables infinite testing. Usually the downlink RF signal is captured by a VSA and then analyzed.
For uplink testing, the baseband data sent by the RRH is captured. Usually, an arbitrary waveform generator is used to create the RF signal, which is then received by the RRH and converted down to baseband data sent over the optical link. This data is captured by the NORI and can be analyzed by a VSA.
To match your fiber and interface speed requirements, the NORI optical interface accepts any standard SFP module from the front panel, accessible by the end-user without use of special tools or opening the enclosure.
OAM Challenge
One of the major challenges in testing RRH is the lack of standardization of the OAM channel. While the lower layer is specified in CPRI and OBSAI, the higher layers are not. Vendors fall back using proprietary OAM systems and for testing usually connect a management system or terminal to the RRH through a special interface like USB or Ethernet. Experience shows that the RRH may well behave different, even in signal processing where one would not expect such impact, when such an interface is used instead of the OAM link provided through the CPRI or OBSAI interface.
The NORI offers two options addressing this issue. In the default setup, the Ethernet OAM link of the CPRI/OBSAI is routed to the ethernet stack transparently. This allows connecting your OAM system and using the 'normal' operational interface. The second option is to include the OAM messaging into the NORI as a plug-in interface.
Your Contact
NORI Example Applications
Factory Testing
NORI is used sucessfully in post-production testing during volume production of RRH. The fast setup time is a major advantage to allow full coverage test and any necessary calibration.
It can also be used for quality assurance testing of selected samples with more elaborate testing cycles, including, for example, tests in climate chambers. This allows close supervision of the output quality.
R&D Testing
RRH testing during R&D requires playing a wide variety of test data. With NORI having the ability to store several test models and switching between them on the fly, testing becomes more flexible than ever before.
NORI is the optical counterpart to your ubiquitous arbitrary waveform generator.
Günter Wolf
Product Manager