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Calculators
In this section Infostream will provide a set of calculators to assist network planners and system integrators to plan, deploy and evaluate emergency services networks.

Network Bandwidth Calculator

Calculators

This calculator provides network administrators with a convenient planning tool to consider network peak performance and contractual issues. The model behind this calculator uses the Erlang C calculation to determine the probability that a set of messages will be delivered to the end consumer within a certain threshold time period and at a certain contractual percentage confidence.  The underlying mathematical distribution assumes that the arrival rate of messages follows a Poisson distribution.  With emergency services networks, the real arrival rates in practice are more extreme than the Poisson model, as the messages are often triggered by extreme, sudden and cataclysmic events.  As such, the forecasts below for contractual performance should be taken as approximations only, and in extreme events (which are often the events for which emergency services networks are designed), will deliver outcomes that could be significantly worse than this theoretical model.

Nevertheless the model demonstrates the significant advantages of the simulcast network model, and also the key performance role played by paging terminals and devices that can support multiple concurrent network transmission channels.

Infostream has more sophisticated modelling and analytical techniques to model real world queuing scenarios, and can provide these as part of its network planning and advisory services.

{Please note that at present this calculator works on Firefox, Chrome, Internet Explorer (7 and higher versions) and Safari browsers only. We anticipate extending to Opera in the near future}

Network Performance

Percent Delivered

within Threshold

Average Message Rate per Hour

Bandwidth Calculator

Number of Characters in Message Number of Overhead Characters for Frame & Sync

Baud Rate of Each Channel
Threshold Message Delivery Performance in Seconds Number of Transmitter Channels at Each Location
Type of Transmission System

Contract Threshold


Explanation of Terms

Number of  Characters in Message

  -> This is the average number of letter characters that form the actual message sent. This will vary significantly from network to network, but a typical emergency services network has around 150 characters in a message

Number of Overhead Characters for Frame and Sync -> Each message includes a set of characters to identify the message and manage its transmission.  In a POCSAG network this typically adds around 15-21 characters as an overhead in the message sequence
Average Message Rate per Hour -> The calculator iterates this variable - it is the message throughput of the network and is the resultant design parameter.  The calculator answers the question "if xx% of all messages have to delivered within yy seconds, then what is the effective bandwidth of the network using this criteria?"  In this paragraph, xx% refers to the Contract Threshold, yy refers to the Threshold Message Delivery Performance and effective bandwidth is the Average Message Rate per Hour at the point where the graph turns from green to red.
Percent Delivered within Threshold -> The percentage of messages at a particular Average Message Rate per Hour that will be delivered within the Threshold Message Delivery Performance.
Baud Rate of Each Channel  -> The number of bits per second that each transmitter channel can physically deliver.
Threshold Message Delivery Performance in Seconds  -> The required performance criteria used in assessing whether a network is performing to specifications.  It is expressed in terms of "xx% of messages must be delivered within yy seconds"  where xx is the Contract Threshold and yy is the Threshold Message Delivery Performance.
Number of Transmitter Channels at Each Location -> A new technique that can be used for agile frequency hopping pagers (such as the X5) is to introduce multiple transmission channels, and to spread the load dynamically across these channels. This variable is the number of transmitter channels at each transmission location.
Type of Transmission System -> There are two main types of network transmission system - simulcast and sequential.  In  a simulcast network the transmission is sent at exactly the same time across all transmitters, and interference is dealt with by small frequency offsets.  In a sequential network, messages are delivered from one transmitter and then from the next transmitter, to avoid overlap, and the pagers must differentiate the existence of duplicate messages.  Sequential networks can also be set up as a mesh of master-slave-slave cells.
Number in Sequence -> For sequential networks, it is necessary to specify the number of transmitters or cells in a sequence.  The calculation model does not take into account the different population densities that may occur in master slave style networks, but simple assumes an even distribution of the user population.
Contract Threshold -> The Contract Threshold is the percentage of messages that contractually must be transmitted within the Threshold Message Delivery criteria - as in "The network bandwidth is the number of messages arriving in an hour such that 99.8% of these messages are delivered within 30 seconds"