Q. What is the difference between a RRH and a RRU?
A. These are two names for the same thing – ‘Remote Radio Head’ and ‘Remote Radio Unit’. In older telecommunication systems all of the conversion of information from some sort of digital form to an RF signal which could be transmitted through the air was done at the ‘base’ of the mast containing the antenna. RF cables would then send the RF signal up the mast to the antenna. In newer systems this conversion is done in an RRH or RRU at the top of the mast. This means that the long cable up the mast is a relatively cheap and lightweight fibre optic cable, and then only a very short RF cable is needed to link the RRU to the antenna
Q. What is the difference between a TMA and a MHA?
A. These are two names for the same thing – ‘Tower Mounted Amplifier’ and ‘Mast Head Amplifier’. This is a low noise amplifier which is situated as close as possible to the antenna, and which improves the overall sensitivity of the system (i.e. it enables the system to successfully process weaker received signals than without a TMA). The benefit is either increased cell coverage area, or increased throughput for the same cell size.
Q. What is the difference between a quadruplexer and a QPV?
A. A quadruplexer is one of a family of ‘multiplexers’ which split one RF path into ‘n’ paths with different frequency bands. A diplexer has two paths, triplexer three paths, quadruplexer four paths, pentaplexer five paths etc… The acronym ‘QPV’ stands for ‘QuadruPlexer Variant’ and is a term that is only used within Radio Design – it is not an ‘industry’ term.
Q. What is AISG?
A. The acronym ‘AISG’ stands for ‘Antenna Interface Standards Group’ and is a communications system used to control some components which are traditionally sited at the top of a telecommunication system system mast. Examples of these components are antennas which can be steered by AISG signals, and TMAs which can report alarms via AISG signals. These signals are often routed along the same RF cables that the main mobile phone signals use, and Radio Design products need to handle these signals as well as the mobile phone signals.
Q. What is the difference between a Passive RF Router and an Active RF Router?
A. A Passive RF Router is a multiplexer with configurable junctions at both ends. This gives many more combining possibilities than just using standard combiners (which have many inputs but just one output). An Active RF Router adds the low noise amplification functionality of a TMA to one or more paths, all in the same unit. A single Active RF Router can replace a number of combiners, TMAs, and associated cabling in a lower cost, size, and weight solution with far fewer interconnections.
Q. What is O-RAN?
A. The acronym ‘O-RAN’ stands for ‘Open (standard) Radio Access Network’ and refers to the language used by the various components in a telecommunication system to communicate with each other. Traditionally these have been proprietary, so a Nokia RRU (remote radio unit) would need to be connected to a Nokia BBU (base band unit) and could not communicate with an Ericsson BBU for example. O-RAN is a shared open source standard which can be used by any manufacturer and will enable customers to pick and choose components from different manufacturers to best suit their needs, knowing that they are all compatible. The analogy is Android phones and the compatibility of apps, regardless of who manufactures the handset.
Q. What is a filter?
A. A filter is any device that removes ‘thing A’ from ‘thing B’. For example an oil filter in a car engine stops debris from getting where it shouldn’t, and sunglasses are a filter – they let certain frequencies through (visible light) while stopping harmful UV and IR light. RF filters do the same thing with radio waves – they let signals of certain frequencies pass through, while stopping signals of other frequencies.
Q. What is the difference between a cross band combiner, and an auto bypass cross band combiner?
A. A cross band combiner is an arrangement of filters, multiplexed or combined onto a common antenna, which each allow a certain frequency band to pass through while stopping all other frequency bands. For example an ‘1800 / 2100 cross band combiner’ passes signals from an 1800MHz band RRU or base station through one filter, and signals from a 2100MHz band RRU or base station through another filter. As well as the RF signals, radio systems often route DC power and AISG signals through the RF cables, as a convenient way to avoid having extra wiring. An autobypass cross band combiner contains some additional electronics, which monitor these DC and AISG signals, and also the components at each end of the combiner, and automatically send the signals where they need to go.
