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Microwave Radio Basics

Microwave radio basics

What is microwave radio?

Availability, 1+0, 1+1, 2+0, rain attenuation,
multi path propagation – what is this?

We offer all services required for the successful use of microwave radio systems, as more than 1,000 realised microwave radio links can attest. Our employees make good use of their many years of experience and their vendor-neutral expertise in all project phases.

Any questions? We’d be happy to help.

General information on microwave radio:

How does microwave radio work and what is microwave radio anyway?

Microwave radio allows wireless message transmission between two fixed points. In general, radio waves spread out in straight lines in the frequency ranges used. That is why the two locations must be in each other’s lines of sight. Directional antennas concentrate the transferable data to a great extent, which is why large distances can be bridged with very little transmission power. Larger distances without direct line of sight can be realised using relay stations.

Why microwave radio?

Microwave radio links can be commissioned very quickly, so that with good project planning and installation, you can use the link after about six weeks. The investment in microwave radio equipment justifies and pays for itself quickly, as there are no high running costs such as with leased lines. Radio connection availability in professionally planned microwave radio links is over 99.99%, with almost no weather-related losses.

What microwave radio solutions does Kapsch Carrier Solutions have?

Kapsch Carrier Solutions offers a wide range of microwave radio systems with data rates ranging from 2 to 2,000 Mbit/s. Ethernet, fast Ethernet, gigabit Ethernet as well as E1, E3 and STM-1 ports are available as interfaces; they are suitable for many applications and can also be combined in some cases. Our microwave radio overview will help you select the ideal system for your application. We are happy to help with any questions you may have when preparing your site network.

Availability

The availability of a microwave radio link is specified as a percentage and describes the proportion of time in which a desired signal can be transmitted. Availability of 99.99% therefore means an average downtime of around one hour per year. Two key components should be considered in calculating the availability of a microwave radio link :

  1. Availability of the hardware
  2. Availability of the radio link

The availability can be raised to the desired level by means of suitable measures.

  1. Redundant components can increase hardware availability
  2. Rain attenuation is addressed by selecting suitable antennas
  3. If necessary, disturbances due to multi-path propagation can be compensated for with diversity

Some Ceragon systems are able to increase the availability of the transmission link using automatic and uninterrupted modulation changes: in the case of adverse weather conditions, they switch to a less sensitive modulation.

Increase availability by switching modulation

Prioritising the data streams ensures that all critical data is transmitted despite a lower data rate; four QoS levels are possible.

Redundancy concepts

Redundant components can be used to increase availability across the entire transmission link and to intercept hardware failures without interrupting the data stream. The type of redundancy is shown in the notation ‘n+m’, where n is the number of transmission links and m is the number of redundancy systems. The most common systems are:

1+0
Single transmission link with no redundancy

Single transmission link with no redundancy

1+1
Single transmission link with redundancy

Single transmission link with redundancy

2+0
Two transmission links with no redundancy

Two transmission links with no redundancy

Rain attenuation

Radio signals are influenced by the presence of water in the atmosphere. The attenuation here is related to the frequency of the signal on the one hand, and the size of the water droplets on the other.

Multi-path propagation

A radio signal can get from the transmitter to the receiver using various paths. With microwave radio systems, these reflections occur both on solid surfaces (the ground) and on atmospheric layers. The different lengths of transmission paths mean that a radio signal can arrive at a receiver more than once and at different times. This can have negative effects on the transmission link. At frequencies above 13 GHz, however, these effects play a more minor role in comparison to rain attenuation.

Richtfunk Mehrwegeausbreitung Multipath

Diversity

Diversity refers to the diversification of the transmission paths, i.e. a signal being routed to its destination via different paths. The availability of the link can be increased using the option of either individually evaluating or combining these signals.

Space diversity

The use of an additional receiving antenna mounted higher or lower is a very effective measure to reduce the effects caused by multi-path propagation. This is called space diversity. As the degree of interference caused by multi-path propagation depends on the difference in length between the main and the reflection path, this can be minimised by a suitable distance between the two antennas.

Space diversity

This results in a usable signal from at least one of the antennas, since the difference in length is not identical for both receiving antennas. The link can be optimised through continuous evaluation of both received signals.

Frequency diversity

If no second antenna can be mounted, frequency diversity can also be used to achieve an improvement in transmission quality. Two frequencies should be selected that are as far apart as possible for this.