Microwave ODU

Microwave ODU (Outdoor Unit)

The term ODU is used in Split-Mount Microwave systems where an Indoor Unit (IDU) is typically mounted in an indoor location (or weatherproof shelter) connected via a coaxial cable to the ODU which is mounted on a rooftop or tower top location.

CableFree Microwave ODU
CableFree Microwave ODU

Often the ODU is direct mounted to a microwave antenna using “Slip fit” waveguide connection.  In some cases, a Flexible Waveguide jumper is used to connect from the ODU to the antenna.

ODU functions

The ODU converts data from the IDU into an RF signal for transmission. It also converts the RF signal from the far end to suitable data to transmit to the IDU. ODUs are weatherproofed units that are mounted on top of a tower either directly connected to a microwave antenna or connected to it through a wave guide.

Generally, Microwave ODUs designed for full duplex operation, with separate signals for transmit and receive.  On the airside interface this corresponds to a “pair” of frequencies, one for transmit, the other for receive.  This is known as “FDD” (Frequency Division Duplexing)

ODU Power and data signals

The ODU receives its power and the data signals from the IDU through a single coaxial cable. ODU parameters are configured and monitored through the IDU.  The DC power, transmit signal, receive signal and some command/control telemetry signals are all combined onto the single coaxial cable.  This use of a single cable is designed to reduce cost and time of installation.

ODu Frequency bands and sub-bands

Each ODU is designed to operate over a predefined frequency sub-band. For example 21.2 – 23.6GHz for a 23GHz system, 17.7 – 19.7GHz for a 18GHz system and 24.5 – 26.5GHz for a 26GHz system as for ODUs.    The sub-band is set in hardware (filters, diplexer) at time of manufacture and cannot be changed in the field.

1+0, 1+1, 2+0 Deployments

Microwave ODUs can be deployed in various configurations.

Microwave ODU in 1+0 Configuration with Antenna
Microwave ODU in 1+0 Configuration with Antenna

The most common is 1+0 which has a single ODU, generally connected directly to the microwave antenna.  1+0 means “unprotected” in that there is no resilience or backup equipment or path.

 

 

 

Two Microwave ODUs in 1+1 HSB or 2+0 configuration with Coupler and Antenna
Two Microwave ODUs in 1+1 HSB or 2+0 configuration with Coupler and Antenna

For resilient networks there are several different configurations.  1+1 in “Hot Standby” is common and typically has a pair of ODUs (one active, one standby) connected via a Microwave Coupler to the antenna.  There is typically a 3dB or 6dB loss in the coupler which splits the power either equally or unequally between the main and standby path.

Other resilient configurations are 1+1 SD (Space Diversity, using separate antennas, one ODU on each) and 1+1 FD (Frequency Diversity)

The other non-resilient configuration is 2+0 which has two ODUs connected to a single antenna via a coupler.  The hardware configuration is identical to 1+1 FD, but the ODUs carry separate signals to increase the overall capacity.

Grounding & Surge Protection

Suitable ground wire should be connected to the ODU ground lug to an appropriate ground point on the antenna mounting or tower for lightning protection.  This grounding is essential to avoid damage due to electrical storms.

In-line Surge Suppressors are used to protect the ODU and IDU from surges that could travel down the cable in the case of extreme surges caused by lightning

The specification of a typical Microwave ODU is shown below.

Typical ODU Features and Specifications:

  • 4-42GHz frequency bands available
  • Fully synthesized design
  • 3.5-56MHz RF channel bandwidths
  • Supports QPSK and 16 to 1024 QAM.  Some ODUs may support 2048QAM
  • Standard and high power options
  • High MTBF, greater than 92.000 hours
  • Software controlled ODU functions
  • Designed to meet FCC, ETSI and CE safety and emission standards
  • Supports popular ITU-R standards and frequency recommendations
  • Software configurable microcontroller for ODU monitor and control settings
  • Low noise figure, low phase noise and high linearity
  • Compact and lightweight design
  • Very high frequency stability +/-2.5 ppm
  • Wide operating temperature range: -40°C to +65°C

For Further information

For More Information about Microwave ODUs, we will be delighted to answer your questions. Please Contact Us

Unlicensed Wireless Links

What is an Unlicensed Microwave link?

Unlicensed and light licence wireless links is the most cost effective of all links and can be deployed in a matter of days. Currently in most countries there are a few unlicensed ISM-band frequencies that are used for point to point links and a few light licensed frequencies that provide interference free operation.

What is a Light Licensed microwave link?

Regional regulators (typically, in each country) are responsible for Spectrum Management of the Radio Spectrum.  This naturally varies in each country due to different history of usage and allocation.

A Light License is where the licensee pays a small licence fee to register his/her radio link with regional regulators such as OFCOM  (UK).

The regulator (such as OFCOM in the UK) use the licence to inform other potential users of the spectrum that there is already a radio link or links in the area when they register their own link prior to deployment. This information is also used to resolve disputes should interference arise.

Frequencies used

Depending on which country you are in, these can include:

  • Licence free spectrum are the 5Ghz, 24Ghz, and 60GHz frequencies
  • Light licence spectrum operate in the 64-66GHz and 70/80GHz

Why consider unlicensed or light license links?

  • Low density areas not suffering from RF interference
  • Budget constraints
  • Non-critical data transmission

When are licensed links mostly used?

  • Organisations looking to create a LAN across multiple buildings on the same site
  • Organisations looking to reduce the cost of existing leased lines
  • In low density areas where RF interference is low or free

When to consider opting for a licenced over unlicensed?

  • High density areas suffering from RF interference
  • Mission-critical data transmission

Is unlicensed or light licenced microwave right for you?

If you are looking for the simple answer, please contact Wireless Excellence for details. Our very experienced team are happy to discuss your requirements and advise on the best solution whatever your needs.