Steam Packet Radio Logo  
company  | contact us  | products  | support  | solutions  | press  | mail us  | mail page

Air-Frame Operations FAQ

The following information provides background information about the technology used in the Air-Frame range, its operation and planning information.

Questions:

What is a Cell Number?

What is a Frequency Hopping Pattern?

How does Frequency Hopping Spread Spectrum technology work?

Do I need a license for the Air-Frame equipment?

Will Air-Frame work in any country?

The 2.4 GHz band contains 83 1 MHz channels but Air-Frame uses only 79, Why?

What is the 2.4 GHz band.

How many co-located cells can I operate with Air-Frame?

Answers:

What is a Cell Number?

A. A Cell Number is a Steam Packet Radio term, which defines a Frequency Hopping pattern. All systems, which use this Frequency Hopping pattern, are said to be in the same Cell. Up to 25 Cells may be co-located at a single central antenna location.

All Air-Frame 10 products are pre-configured for Cell Number 0.

What is a Frequency Hopping Pattern?

A. A Frequency Hopping pattern (or Cell Number) is a pseudo random pattern which defines the sequence in which the 77 1 MHz channels within the 2.4 GHz band are used by the Air-Frame. Each Cell Number (or Frequency Hopping Pattern) starts on a different channel.

How does Frequency Hopping Spread Spectrum technology work?

A. Frequency Hopping Spread spectrum (FHSS) technology divides the available spectrum into a large number (79) of 1 MHz channels. The radio system then uses these channels in a pseudo random sequence (a Cell Number or Frequency Hopping pattern) and literally hops from channel to channel (staying a maximum of 400 ms on any single channel and visiting every channel every 30 seconds). Wireless signals are prone to interference, which is essentially random in space and time. Frequency Hopping is a robust technology precisely because it uses different channels all the time. The statistical probability of interference on any channel is the same but the probability of interference on more than one non-adjacent channels is very low. Frequency Hopping is most likely to communicate most of the time. Technologies such as Direct Sequence Spread Spectrum (DSSS) on the other hand while offering higher data rates have a much higher probability of failure since they occupy much wider channels (typically 20 MHz) and hence are prone to interference in any ‘part’ of the channel. Direct Sequence technology has a statistically significant possibility of never communicating in ‘noisy’ environments.

Do I need a license for the Air-Frame equipment?

A. No. Air-Frame uses the license-free 2.4 GHz ISM band. If the equipment is to operate in Japan, Spain or France you will require a country specific model.

Will Air-Frame work in any country?

A. The standard Air-Frame will work in all countries except for Japan, France and Spain in which case country specific models will be required.

The 2.4 GHz band contains 83.5 1 MHz channels but Air-Frame uses only 79, Why?

A. The channels at the beginning and end of the spectrum are not used to minimize interference from adjacent bands (called a ‘guard band’). This leaves 79 operational channels (in most of the world) for use by Air-Frame.

What is the 2.4 GHz band.

A. The 2.4 GHz band operates in most of the world from 2.400 to 2.4835 GHz. It is a license-free band which is sometimes referred to as an ISM band (Industrial, Scientific and Medical). In the case of Japan the band operates from 2.471 to 2.497 GHz, in France from 2.4465 to 2.4835 GHz and in Spain from 2.445 to 2.475 GHz.

How many co-located cells can I operate with Air-Frame?

A. Air-Frame 100 allows complete control over cell allocation and in theory allows you to operate 79 co-located cells from any single mast or antenna farm. In practice the risk of adjacent cell interface becomes high above 12. However if your cells are all low volume (e.g. Telemetry or SCADA) then you can go well beyond 25 co-located cells. We recommend you never exceed 40 even in the lowest cell usage environment.


Copyright © 1994 - 2018 ZyTrax, Inc.
All rights reserved. Legal and Privacy
 
site by zytrax
web-master at steampacketradio.com
Last modified: July 11 2011.

support home
faqs
ethernet
installation
documentation
configurations
technology
calculators