People search system

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People search systems are telecommunication facilities in buildings or closed areas. People search systems are usually intended as a protective device for people and safety equipment for the operational process to reduce the search times for the search for individual people for the purpose of team building or in service operations or even in emergencies. People search is therefore an aid in order not to restrict the mobility of people, but to quickly determine their current whereabouts in case of urgent need.

Search solutions that only search traces of people in documents or telecommunications networks that have arisen in the past are also referred to as people search systems. These tracing functions do not provide real-time information from a person search (tracing).

functionality

To search for people, information is required without delay (in real time ). The aim of the use is to establish a temporary communication between a person who is looking for, who moves freely in a known area or building, and a person who is looking for personal presence or his information.

The determination of the current location of the wanted should remain limited to the (effective, i.e. court-proof) agreed objectives in order to be able to meet the legal and supreme court requirements for informational self-determination and to help prevent those involved from undermining the system function.

Physical limitations

Alternative and technically similar solutions described are known for the search for things. Solutions using satellite systems and mobile radio systems are generally not sufficiently precise for searches in or between buildings. The search for people on the move makes high demands and excludes an exploratory search with repeated runs of a rather sluggish search process.

Technical restrictions

As a rule, a spontaneous search does not provide the desired reliable result, so that a search is prepared with a track formation that is always running along. The technically and economically feasible solutions for use in buildings do not all deliver satisfactory performance and are not necessarily economical in operation and investment. Clear technical specifications of the manufacturer for the runtime ( latency from search command to search success) or repeatable metric accuracies (resolution on rooms or levels) and selectivity (identification of all individuals in a group) are often lacking. In addition, legal restrictions for electronics and optics must be observed.

Legal framework

A track formation ( movement profile ) collides with the general requirements of the German Trade Union Confederation for employee data protection, for example: People search systems generally restrict informational self-determination. However, the operation of people search systems is required by statutory provisions on occupational safety (chemistry) or plant operation (power plants) and is therefore exempt from co-determination according to the BetrVerfG, but is subject to the involvement of employee representatives. Even setting up a people search system is subject to legal participation. The prerequisite for the use of person-searching devices is the express consent of the responsible body. Any other approach is a violation of the fundamental right to informational self-determination .

Use by employees requires the express consent of the individual users; the mere receipt of a personal identifier is not a sufficient form of expression of such consent. Anyone who does not want to be searched can explain this, but must adhere to the requirements of the professional associations (statutory accident insurance) as well as the trade supervisory authority and the fire brigade .

Technical and operational requirements

In Germany, call systems generally serve to transmit a request without delay, at least with central signaling and with a local display at the source. For this purpose, the state of the art is defined by the requirements of the DIN VDE 0834-1 standard and can be read there. Technical deviations from this requirement horizon can mean considerable consequences in the event of damage with regard to the insured liability up to and including simple negligence.

There are various wired and wireless system concepts for this. However, it can be seen that some of the known requirements of the standard are often not all supported by newer wireless solutions. The features are particularly affected:

  • Use of your own network
  • at least periodic monitoring at intervals of <30s
  • Feedback to the trigger point
  • Reliable assignment of an alarm to exactly one room
  • Functional reliability even in the event of a power failure
  • Self-test until battery exhaustion

In contrast, some of the newer solutions are considerably more robust in terms of the following features, which were treated as secondary in the case of wired solutions:

  • Detection of an alarm from any location
  • Localization of the alarm source in the entire operating area
  • automatic registration of attendance for individual rooms

Furthermore, some features are always critical in both wired and wireless solutions:

  • Protection against moisture and water (second digit in the degree of protection )
  • Functional reliability even in the event of a power failure
  • Detailing of the alarm recording (where from?) And the alarm acknowledgment (by whom?)
  • Recognizing the whereabouts of the person

A departure from the classic two-wire solutions will take place as soon as the wireless solutions are offered in a completely standard-compliant manner and offer substantial additional benefits, such as

  • Identification of the personnel when resetting the triggered calls
  • automatic registration of staff during security walks
  • Improvement of the resolution on individual persons
  • Extension of localization to traffic areas
  • Detection of passages at entrances and exits
  • Recognizing conspicuous situations or falls

In addition, an additional expansion undoubtedly brings the sensors of the person search system and their overall function directly into the category of medical technology devices:

  • Detection of critical sensor values

Technical system alternatives

People search systems offer the functions, for example, on the basis of the following infrastructures:

  • the wired triggering of light signals with a nurse call system with simple room binding, but without personal identity of the display (no industry standard)
  • the simple wireless audio signaling to individual devices (unicast) or device groups (multicast), for example at 433 MHz in the license-free ISM band
  • general signal transmission via GSM, GPRS, UMTS and variants (not generally permitted in clinics) after localization via GPS (only reliable outside of buildings)
  • connectionless (connectionless) and sessionless (sessionless) as well as wireless (wireless) signaling via broadcast
  • connectionless and session-oriented as well as wireless signaling via direct transmission (paging)
  • voice transmission similar to GSM voicemail with tone signal (unicast in DECT standard)
  • wireless telephony with handheld devices as a point-to-point connection (unicast in the DECT standard)
  • wireless telephony with handheld devices as a point-to-all connection (multicast in the WLAN standard)
  • short text transmission similar to GSM ShortMessage (SMS with or without tone signal, unicast in the DECT standard), also with protocols IETF-SNPP or IETF-WCTP, e.g. proprietary solution ASCOM
  • additional activation and / or identification in close proximity (RFID at 868 MHz in the license-free ISM band)
  • the unsharp localization of people using two-frequency systems (RF code with infrared, sonitor with ultrasound 40 kHz and WLAN or Visonic 800–900 MHz UHF and with infrared and high frequency 130 kHz)
  • the fuzzy localization of people through unilateration (RSSI and WLAN, Aeroscout or Ekahau at 2.45 GHz in the license-free ISM band)
  • precise localization via asynchronous multilateration (RTLS, Nanotron at 2.45 GHz according to ISO 24730-5 in the license-free ISM band)
  • the precise localization via synchronous multiangulation (RTLS, WhereNet at 2.45 GHz according to ISO 24730-2 in the license-free ISM band, Abatec and Symeo at 5.8 GHz in the license-free ISM band, Ubisense in the license-free band with UWB around 7 GHz)
  • the unsharp localization of people through multi-frequency systems (UWB, time domain in the license-free band range 3 to 10 GHz)
  • complex functions via central servers and mixed local radio networks

An infrastructure-free people search system can generally not be implemented.

Operational objective

People search systems should be able to address individuals or qualified groups as specifically as possible. Signaling in broadcast calls must be restricted to exceptional cases if interference or loss of attention is to be avoided.

A targeted search should be able to be triggered as decentrally as possible, with the only minimum requirement being a personalized signal transmitter that enables conclusions to be drawn about the triggering person and a known location. At the same time, this signal transmitter should also reveal the last detected location, or better still, the current whereabouts of the triggering person.

Technical characteristics

Modern people search systems are usually radio-based systems. Conventional systems e.g. B. according to VDE 0834 use wired signaling devices. A minority of offers use light or ultrasound for signal transmission.

All solutions have in common that the function can be prevented by simply switching off the devices or components or by using appropriate shielding. The transmission power used by the search signal generator is usually lower than the signals for mobile telephony. The transmission power of the personal license plates is limited by the built-in battery anyway very low.

Personal equipment for the wanted

The person who can be found must carry a personal identifier; this is usually a radio receiver ( receiver ) or radio transmitter ( transmitter ) or combinations ( transceiver ) that must be constantly active to support the search.

Personal equipment for the seeker

The people who are to find a wanted person can carry a device for information display, e.g. B. a smartphone . Mostly, however, light signals are used under ceilings or above doors or at least data display devices with map displays are set up in monitoring centers.

Autonomous process as a minimum requirement

The alarm can be triggered either autonomously (sensitive) or manually. However, a search must always work as an autonomous information process in order to give the searcher an indication of the whereabouts of the person sought. Even so, solutions that require concurrent cooperation with what is being sought are also consistently referred to as search systems.

standardization

There are a variety of technical standards and national or international standards of DIN or ISO for the used technological tools ( received signal strength indication , RSSI, Real-Time Locating System , RTLS, and Radio Frequency Identification, RFID ) and procedures. On the other hand, there is no standardization whatsoever for the functional content of people search systems or of localization systems. Therefore, a direct operational comparability of the technical offers of different manufacturers is not given until further notice and industry standards for the functions of these systems beyond the safety standard DIN VDE 0834-1 are hardly to be expected in the future either.

Positioning procedure

With regard to the interaction in the search, non-cooperative methods (see above) require a measurement method for the current location of the wearer of the personal radio device. For this purpose, the alternative methods of unilateration are known as unsharp localization in polar coordinates or triangulation or multilateration for precise localization ( real-time localization ) in absolute coordinates.

See also

Individual evidence

  1. ↑ IETF RFC1861 SNPP Drafted , 1995
  2. ↑ IETF_WCTP (PDF file; 1.31 MB), 2003
  3. ↑ http://www.id.uzh.ch/dl/telefonie/support/Dokumente/PSA_Empfaenger_Merkblatt_F.pdf (link not available)
  4. ↑ Standard: DIN VDE 0834-1: 2016-06 call systems - DGWZ. In: dgwz.de. September 4, 2010, accessed August 25, 2019 .