Tag Direction

Introduction

AdvanNet can provide an estimate of tag direction.

  • Antennas are placed into a virtual line connecting a logical IN and OUT areas.

  • Tag direction estimates whether a tag moves from IN --> OUT or OUT --> IN.

  • Tag direction estimate works only in Autonomous modes.

Tag Direction estimation is heavily affected by the following:

  • Number of tags to be detected

  • Number of antennas

  • Environment

  • Type of tags

  • Type of products

  • Etc

Tag Direction uses a generic algorithm based on read data. For the algorithm to work:

  • AdvanNet version 2.3.x

  • More than one antenna must be used

  • The intersection of the antennas radiation pattern should be smaller as possible.

  • Detect only a little amount of tags. Ideally less than 5.

  • To work in Autonomous mode

Tag Direction estimate requires EPCGen2 (Session 0 and Target AB) settings that may affect negatively read rate.

This means Tag Direction estimate does not match good with scenarios were box level or item level is required.

Tag Direction estimate represents a best effort to resolve goods pass direction.

It has proven to be successful in some scenarios and has failed in some others.

Tag Direction estimate is an estimate!

Any system using it must be prepared to manage incorrect values for the pass direction.

The better the system manages error conditions the better a system will be.

Tag Direction estimate is implemented using a general purpose algorithm. That means that every particular scenario will have potential better ways to resolve pass direction.

Requirements

To estimate the tag direction, the following requirements are needed:

    1. AdvanNet version 2.3.x

    2. The read mode has to be Autonomous.

    3. More than one antenna must be used

    4. The intersection of the antennas radiation pattern should be as small as possible.

    5. Antennas must face inwards and outwards directions. There are two options

      • There has to be a minimum separation between the antennas in the travel direction.

The distance d depend on the installation: it is generally between 0.5 meters to 1.5 meters.

      • The antennas have to be a tilted in a way each antenna points to an opposite directions.

Configuration

Follow the steps in order to enable it:

  • Add configuration to enable direction estimate: to enable the direction estimate it is required to use static devices and modify the device definition file.

Add the following into the device definition file:

...

</reader>

<enableTagDirection>true</enableTagDirection>

<directionTracker>

<class>TAG_DIRECTION_ALG1</class>

<enabled>true</enabled>

<maxTime>5000</maxTime>

<minSamples>3</minSamples>

</directionTracker>

</antennas>

...

Parameters:

  • maxTime (ms): time taken to estimate tag direction after first tag read.

  • minSamples: minimum samples required to apply tag direction algorithm. if after maxTime the number of samples for a certain tag are less than minSamples, the UNSPECIFIED_NOT_ENOUGH_TAGS is generated.

  • Add direction orientation to antenna.

      • Positive numbers mean the antenna is oriented to the logical IN area.

      • Negative numbers mean the antenna is oriented to the logical OUT area.

      • The bigger the absolute value of a number means that antenna is facing more clearly one LOGICAL area.

  • Configure EPCGen2 Session to 0 and EPCGen2 Target to AB

The tag direction estimate will work with Autonomous mode only.

Socket 3177

Once the tag direction estimate is enabled, events will be received on port 3177.

Events include:

  • EPC

  • Direction

Alternatives

As previously said, the used algorithm is very generic, for the cases where the tag direction estimate does not provide good results, it is possible to process raw data to improve results.

The socket 3177 provides real-time raw data that can be post-process in any programming language.