Course11:Advanced - IP-DECT

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The book about innovaphone IP-DECT based on innovaphone IP1202.

Contents

DECT Standard Basics

Radio Channels and Timeslots


The DECT Standard allocates 10 carrier radio frequencies – 2 MHz each. A carrier is subdivided into 24 time frames - each 10ms long. This time slots are used for up- and downlink so on each carrier in DECT we have 12 bidirectional channels.

The IP1202 uses only 8 bidirectional channels for voice. Remaining 4 channels are reserved for Sync. bearer (Air Sync between base stations) and broadcast messages.

The carriers and time slots are shared between all bases stations and handsets in the system. This means, it is essential to keep all base stations and handsets in sync with Air Sync master – a single IP1202 in the system providing Sync to all other radios.

Continuous Base Station Broadcast (Dummy Bearer)


A base station continuously transmits one or two so called dummy bearer when idle (i.e. when no calls or data are transmitted to or from the base station). The reason for continuously transmitting the dummy bearer is due to that the DECT handset listens to one dummy bearer and uses the information to lock-on to the system; synchronize, check base station identity, system capabilities, status and paging information for incoming voice and data call set-ups as well as for preparing handover, call setups etc.
This means that a base station is always transmitting information regardless of which type, residential or multiple base station system. Note: The dummy bearer is only transmitted in the base station to DECT handset direction.

Call Setup


A call in DECT is always initiated from a DECT handset. The handset synchronize to the base station by listening to the dummy bearer. The handset selects the best channel and makes call attempt. The base station listens periodically on all carriers and accepts a call attempt from the handset.

The call from DECT base station to the handset is initiated by sending a page message in the continuous broadcast. The handset will receive the message and setup a radio link to the base station.

Relevant Terms

RFP and RFPI



A Radio Fixed Part (RFP) is reffered to as DECT base station, especially its radio part.

Radio Fixed Part Identity (RFPI) is the broadcast identity which uniquely identifies a RFP in the DECT system.

PARI and SARI


An Access Rights Identity is an unique identification number for a DECT System.

In an IP1202 based DECT system we have two ARIs - Primary and Secondary. The Primary ARI (PARI) is always assigned to a single Radio of IP1202 by the PARI Master automatically. The Secondary ARI (SARI) is assigned to all Radios managed by the PARI Master and must be configured manually.

A SARI is provided by innovaphone with a "DECT SARI Certificate" that must be purchased for every DECT system that is installed in production environments.

For the training and test purposes a fish-help.png Test-SARI can be used.

Handover and Roaming


The process of moving of a DECT handset from one base station to another during an active call is Handover. In the DECT system based on IP1202 a handover is always performed as external handover between two PARI domains (two IP1202).

The Roaming is a process of logging in of a handset to a DECT system with different SARI domain or different Sync domain.

IP-DECT Overall System Design

The IP1202 based IP-DECT system have a modular structure that can be modelled as a number of network entities. The network entities defined are:
  • the entity offering the H323-DECT gateway functionality will be referred to as Radio
  • the entity acting as the proxy for the IP terminated DECT handsets within the coverage of the associated Radios will be referred to as Master
  • the entity offering support for finding home location information will be referred to as Mobility Master
  • the entity offering support for distribution of the DECT identity RFPI will be referred to as PARI Master. In other words, PARI Master knows which Radio runs on which IP1202.

System Overview

Radio

The DECT Radio is responsible for converting the signalling and voice data between DECT radio signals and IP network packets.

On every IP1202 one Radio can be activated. The Radio can serve up to 8 simultaneous calls to the DECT handsets locked to this Radio.

Master

The IP-DECT Master is responsible for managing signalling information between the H323 registrations of users to the innovaphone PBX and internal H323 signalling in the IP-DECT system (this means the signalling between IP-DECT Master and Radios).

The IP-DECT Master also maintains the Home Location Database (HDB) - the database containing the authentication information for the DECT handsets. The HDB is shared to the Mobility Master, if any configured.

Additionally the IP-DECT Master is responsible for the handling of the Feature Codes like Activate/Deactivate Call Forward etc.

One single Master can handle up to 1000 DECT users. It is possible to have more than one IP-DECT Master in the IP-DECT system for load balancing purposes.


PARI Master

The PARI Master is an additional function of the IP-DECT Master and manages the Radios of the base stations in the IP-DECT system. The PARI-Master maintains a database of RFPIs assigned to the Radios and associated MAC addresses of the IP1202 running this Radio.

The PARI Master enabled on IP1202 can manage up to 1023 Radios. There is only one PARI Master in the IP-DECT system.

Mobility Master

The Mobility Master connects multiple IP-DECT Masters to enable roaming of the DECT handsets between them.

It stores the HDBs of the Masters and “knows” about all DECT handsets subscribed to this Masters.

Redundancy

Each of the above-mentioned network entities (Master, PARI Master, Mobility Master) can be configured as a Standby instance.

The Air Sync Master also can be secured by an additional Air Sync Master referring to the first Air Sync Master.

Air Sync

The IP based DECT system of IP1202s uses radio channel to synchronise the radios.

Radios configured as sync master will report to the PARI Master that it wants to be a sync master. The PARI Master will select one of them to be the active sync master.

When a sync master has been assigned to be active it searches for other IP1202s within the same region during 30 seconds. If any IP1202 is found the values for slot, frame and multi frame are received and applied to the Sync Master. After receiving all these values or after the time-out of 30 seconds the Sync Master enters the master state.

With this method it will be possible to restart only the Master in the region. The remaining slaves will be able to maintain synchronization for a few minutes during restart of the Master. The Master will adjust itself to the other IP1202s at startup. The slaves will notice that the Master is back and the synchronization will be received from the Master.

In master state the values are updated locally during all further operation of the Master IP1202 and no synchronization to other IP1202s in the same region is done.

It is possible to configure the Sync Master to synchronize to a reference base station (another or same DECT system). In this case the Sync Master will try to synchronize to the reference system if the reference system is found but it will not require the reference system to be available. The Sync Master will operate even though the reference system is not available. During startup the Master will prefer to synchronize to a slave base in the same system before synchronizing to the reference base station.

Sync Regions


Sync regions are used when, for example, several buildings are located in the same coverage area and all radios are using same PARI Master but where the synchronization coverage between buildings is not good enough for a stable synchronization.

A solution may be to use separate synchronization regions for the buildings and have reference synchronization between the regions. Each region has its own Sync Master but can take reference sync from another region and handover between the buildings is possible. If a region should lose the reference synchronization with another region, the internal synchronization in respective region will still work but there can be no handover between the regions.

The max. number of Sync Regions that can be defined is 64 (from 0 to 63).

Note: For the synchronization to work, it is not allowed to configure reference sync in a ring.

DECT System Layout Examples

Depending on the number of PBXes, sites and deployed DECT handsets in the IP-DECT System different layouts of the DECT System can be implemented.

Considered grossly there are DECT systems with single IP-DECT Master and with multiple IP-DECT Masters.

One Master

Single Site


This layout may be used for customers with a single site installation.



In a single site installation, one of the IP1202 will have an active Master and PARI Master software component, and optionally have an active Radio. All other IP1202 will only have the software component Radio active. One of the active Radio components is the Air Sync Master.

The system capacity for this layout is:
  • Up to 1000 users (Note: Up to 500 users if SIP over TLS is used.)
  • When the number of system IDs used in the installation is between 1 to 36:
    • Max. 1023 IP1202 / PARI Master
  • When the number of system IDs used in the installation is between 37 to 292:
    • Max. 127 IP1202 / PARI Master

Multiple Sites


This layout is chosen if there is no need for local functionality in remote sites. If the WAN connection between the remote site and site with IP-DECT master is down, the remote site is without DECT support.



The same layout as in a single site can also be used for customers with an installation on several sites. The sites may have one or several IP1202 at each site. The PBX and the PARI Master and Master are centrally located. Each site has one IP1202 as Air Sync Master with own Sync Region.

With this solution the handset will be able to roam to a different site and it will be possible to receive incoming and make outgoing calls.

The system capacity for this layout is:
  • Up to 1000 users (Note: Up to 500 users if SIP over TLS is used.)
  • When the number of system IDs used in the installation is between 1 to 36:
    • Max. 1023 IP1202 / PARI Master
  • When the number of system IDs used in the installation is between 37 to 292:
    • Max. 127 IP1202 / PARI Master

Distributed PBX Systems



In a PBX System with a Master PBX and one or several Slave PBXes, the single IP-DECT Master points to the Master PBX. The registrations to the User Objects belonging to Slave PBXes will be redirected by the Master PBX. This enables to maintain single IP-DECT Master in the System of multiple Master-Slave PBXes.

Consider that in this case the registrations of all DECT users will have the Master PBX as physical location. This can be a problem, if Local Flag (refer to the Topic Distributed PBX) functionality is used.

Multiple Master

Single Site


This layout may be used for customers with a large single site installation, when the load must be distributed over a number of Masters to be able to cope with the load generated from a large number of handsets. It will be possible to do roaming and handover between all Radios.



In a single site installation one or several of the IP1202 will have an active Master software component, only one of the Masters will have an active PARI Master, and one IPBS/IPBL will have an active Mobility Master software component, and optionally have an active Radio. All others will only have the software component Radio active.

The system capacity for this layout is:
  • Up to 1000 users / Master (Note: Up to 500 users / Master if SIP over TLS is used.)
  • When the number of system IDs used in the installation is between 1 to 36:
    • Max. 1023 IP1202 / PARI Master
  • When the number of system IDs used in the installation is between 37 to 292:
    • Max. 127 IP1202 / PARI Master
  • Max. 100 Masters / Mobility Master

Multiple Sites


This layout is chosen if local functionality in remote sites is required, even if the WAN connection between the remote site and site with IP-DECT master is down.




In site A, one of the IP1202 will have an active IP-DECT Master, PARI Master and Mobility Master software component, and optionally have an active Radio. All others will only have the software component Radio active.

In site B the same configuration, but with out Mobility Master.

The system capacity for this layout is:
  • Up to 1000 users / Master (Note: Up to 500 users / Master if SIP over TLS is used.)
  • When the number of system IDs used in the installation is between 1 to 36:
    • Max. 1023 IP1202 / PARI Master
  • When the number of system IDs used in the installation is between 37 to 292:
    • Max. 127 IP1202 / PARI Master
  • Max. 100 Masters / Mobility Master

Multiple Mobility Master

This layout is chosen if there is a need for local functionality in a site with several Masters. This layout may be used for customers with large multiple site installations. Load must be distributed over a number of Masters to be able to cope with the load generated from a large number of handsets in one site. It will be possible to do roaming and handover between all Radios within each site. It will be possible to do roaming to all other and it will be possible to receive incoming and make outgoing calls.

A system can consist of several Masters where each Master is logically connected to a specific PBX. A Master dynamically makes H.323 registrations to the “home” PBX for each of the handsets within its coverage.

In each site one or several of the IP1202 will have an active Master software component, only one of the Masters will have an active PARI Master, and one IP1202 will have an active Mobility Master software component, and optionally have an active Radio. All others will only have the software component Radio active.

The system capacity for this layout is:
  • Up to 1000 users / Master (Note: Up to 500 users / Master if SIP over TLS is used.)
  • Max. 10 Mobility Masters / System
  • When the number of system IDs used in the installation is between 1 to 36:
    • Max. 1023 IP1202 / PARI Master
  • When the number of system IDs used in the installation is between 37 to 292:
    • Max. 127 IP1202 / PARI Master
  • Max. 100 Masters / Mobility Master

Configuration

Before starting the configuration of the DECT System we have to choose the system layout and define the number of network entities like Masters, PARI Masters etc.

For each Master unique System Name and Master ID must be defined.

For each PARI Master a unique System ID must be defined.

Additionally the SARI for this DECT System must be obtained. If you use the fish-help.png Test SARI for training purposes, make sure no other systems with the same SARI are running nearby.

In general following configuration steps must be completed:
  • PBX and Users
  • LDAP Replication
  • Master
  • PARI Master
  • Local Radio as Air Sync Master (optional Sync Region)
  • Additional Radios

PBX and Users

DECT System Object


In the first step a PBX object of type fish-help.png DECT System must be created. For every IP-DECT Master in the DECT System an own DECT System Object must be created, so there can be multiple DECT System Objects in one PBX, depending on the number of IP-DECT Masters.

Later, when we configure the IP-DECT Master, the Long Name of this Object will be used as the DECT System Name and will be visible on the screens of the DECT handsets, so select the Long Name accordingly (e.g. "Site A" or "Company HQ" etc.).

Assign DECT System to a User


To enable a User Object to use a DECT handset a DECT System Name must be configured at User Object (Tab DECT).

If you already know the IPEI of the DECT handset assigned to this user, you can provide it here together with the user specific Access Code. This will enable to subscribe the handset towards the DECT system and map it to the user in one step.

The IPEI of the DECT handset is printed on the box and under the battery on the handset. Also it is possible to use fish-help.png Service Codes to check the IPEI directly on the handsets menu.

In case the IPEI is configured directly into the user object, the last check digit should be omitted. E.g. if IPEI printed on the box or handset is 0123456789870 (13 digits) you should only enter 012345678987 (12 digits) under user object, otherwise the registration will fail.

LDAP Replication

LDAP Credentials on the LDAP Server


Since the IP-DECT Master replicates users from the PBX via LDAP credentials for this must be created on the device running the PBX LDAP database - this is usually Master PBX. The credentials must have write access permission, in order the DECT Master can write the DECT subscription information in to the PBX.

The LDAP credentials for the PBX LDAP Server are configured under fish-help.png Services/LDAP/Server.

Make sure not to use the ldap-guest/ipxxx credentials for this purposes!

LDAP Replicator


On every IP-DECT Master an LDAP Replicator must be configured to replicate Users belonging to this IP-DECT Master. The filed "DECT Gateway Name" must contain the Long Name of the DECT System Object, the User belongs to. The IP address points usually to the Master PBX. The DN is usually cn=PBX0 if no DynPBX is used.

Master

The configuration of the IP-DECT Master contains following mandatory settings:
  • System Name
  • Password
  • Master ID
  • Registration towards innovaphone PBX

Optionally the IP-DECT Master can be connected to a Mobility Master.

System Name

The System Name equals to the Long Name of the DECT System Object.

Password

The password for the DECT Master configured under DECT / Config / System , must be the same used in the PBX configuration. This PBX Password is configured in the PBX under PBX / Config / Secuity

Master ID

Enter a Master id in the Master ID field under DECT / Config / Master. The ID must be unique for each Master in a multiple Master system. The Standby Master must have the same ID as the Master.

Subscription Mode and Authentication Code

There 3 fish-help.png subscription modes possible:

  • Disabled - no new DECT handsets can be subscribed. This option can be used, if already all handsets are subscribed and no further should be able to subscribe.
  • Allowed - the handsets are subscribed using the Authentication Code configured here. After subscription this way, the hand set must be mapped to the PBX User.
  • With activation - requires manual activation of subscription, that will auto-disable after 120 seconds. The handsets are subscribed using Authentication Code configured under DECT Tab of the User Object in the PBX. The IPEI Number configured at User object and of the subscribing handset must match. After subscribing this way, the DECT handset is mapped to the PBX User immediately after subscription toward the DECT system. Also subscription of anonymous handsets is possible, using the Authentication Code configured here.

Registration towards innovaphone PBX

Each IP-DECT Master manages the registrations of handsets towards an innovaphone PBX.

The IP-Address of the PBX and other registration relevant settings like Gatekeeper ID are configured under DECT / Config / Master.

The option Registration with system password can be used to register the DECT-Handsets with the fish-help.png PBX password at the PBX, instead of User specific Password. Therefore the option PBX Pwd on the User Objects devices must be enabled.

PARI Master

Since PARI Master is an additional functionality of the IP-DECT Master, it must be activated on one of the already configured Masters. This is done by activating the check box "Enable PARI Function" under DECT / Config / Master.

System ID


Select a number between 1 and 292. If this is not done, the IP1202 will randomly select a number.

The number of system IDs will affect how many Radios/IP1202 that can be used per PARI Master in an installation, as shown below:
System ID = 1 to 36: Max. 1023 IP1202 / Pari Master
System ID = 37 to 292: Max. 127 IP1202 / Pari Master

Configure the System ID under DECT / Config / PARI of the PARI Master.

SARI


The PARI Master is also responsible for storing and distributung the SARI to the connected Radios.

Configure the SARI under DECT / Config / SARI of the PARI Master.

Air Sync Master

To configure an IP1202 as an Air Sync Master select "Master" in the Sync Mode drop-down list at DECT / Config / Air Sync.

To synchronize the sync master to a reference base station, enter the reference base station in the Reference RFPI text field. Enter an alternative reference base station in the Alternative reference RFPI text field (optional).

Enter a region ID between 0 and 63 in the Sync Region text field.

Also the strategy to recover from reference sync failure can be defined: if the reference sync is lost the system continues to run without reference sync. If you resync on command the radio part of the sync Master will restart and do an attempt to resync to its reference source. All other base stations depending on this sync Master will then resynchronize. If you have scheduled a resync and the reference sync is lost prior that, the system will run without reference synch until the scheduled resync time appears.

Standby Air Sync Master


Radios configured as sync master will report to the PARI Master that it wants to be sync master. The PARI Master will select one of them to be sync master and the others will be set to standby sync master.

Only one Sync Master needs to be configured for a synchronization region. But if this single IP-DECT Base Station fails, the entire synchronization region will fail. It is therefore possible to set several radios as sync masters to achieve standby sync master functionality. In case reference sync is used on the sync master remember to also configure reference sync on the standby sync masters. The actual RFPIs used as reference sync may differ on the different sync masters as they are positioned at different locations.

If the sync master goes down, the PARI Master will assign one of the standby sync master to be active sync master.

Additional Radios

Automatic Configuration


An IP1202 used only as Radio can be easily added to the DECT System by using automatic Radio registration mechanism.

Every IP1202 with not configured Radio will try to register at PARI Master using Gatekeeper Discovery mechanism. The PARI Master and Radio must be in the same broadcast domain of the local network.

The uninitialized Radios will appear under DECT / Devices Overview / Radios:

Uninitialized Radios

After click on "Add" and providing Device Name (also configured under General / Admin) for this IP1202, the Radio of IP1202 will be automatically configured. The Kerberos configuration in this step is optional.

Handset Deployment and Configuration

Deployment of the DECT Handsets


In general the deployment of a DECT handset is divided in two steps:
  • Subscribing of a DECT handset to the DECT system
  • Mapping of the subscribed DECT handset to the PBX User

Subscription of a DECT Handset

A brand new DECT handset like IP61 or IP63, or after a factory reset, will ask for the System Name, PARK, Access Code (AC) and Protection Mode after powering on.

You can input DECT System Name or PARK to identify the DECT System to subscribe in. It is also possible to leave System Name and PARK empty, if you are sure, that there no other DECT Systems.

The PARK of the particular DECT System can be found under DECT / Users of the IP-DECT Master.

The AC that must be provided is defined as Authentication Code on the IP-DECT Master, under DECT / Config / System.

By putting the Protection to On you can prevent the Users to unsubscribe the handset from the DECT System.

Login of the PBX User

After successful subscription the IPEI of the DECT Handset will be visible under DECT / Anonymous and login can be performed.

To login dial the following sequence on the DECT handset:

*<Master-ID>*<User-Number>*<Access-Code>#

The Master ID is configured under DECT / Config / Master and has default value 0. The User Number is the Number of User Object in the PBX. Depending on the configuration the Access-Code is system wide, configured under DECT / Config / System, or is configured for each user separately under DECT Tab of the User Object in the PBX.

This step can be omitted if the IPEI of the DECT handset is stored at the User Object, before subscribing the handset. In this case the login is performed automatically while subscribing toward the DECT System.

Display Name and Idle Display


The Idle Display is the string you see on the DECT Handset in idle state, which can be configured directly via the DECT Handset menu.

Usually, if the Display Name of the User Object in the PBX is configured, it will be used also as Idle Display of the DECT handset.

In case no Display Name is configured at the User Object, but an Idle Display on the DECT Handset is configured, the Idle Display will be replicated to the Display Name of the User Object, if the DECT Handset makes subscription at such User Object.

Phone Book

The IP-DECT Master can be configured as LDAP client for the LDAP based Corporate Directory like ESTOS MetaDirectory. This will enable to use the "Central Phonebook" function of the DECT handsets.

At this point we have to differentiate between searching for a number in the directory to make a call and searching for a name on an incoming call.

So, there are two different modes for this function:

  • Search for a name in the central phone book and call the found number
  • Resolve numbers of incoming external calls to names
    •  

Search for numbers to call



The IP-DECT Master provides the LDAP client functionality for the DECT handsets, to be able to search in the LDAP directory of the PBX. Additionally an external LDAP server like Estos MetaDirectory can be used to store the external numbers in the central phone book.

The settings for LDAP client can be configured under DECT / Config / Phone Book and are almost the same that are used for the LDAP client of the IP-phones (refer to the Topic Corporate Directory).

The first section of the LDAP client configuration is used for LDAP credentials of the PBX internal LDAP server. The second section is used for LDAP credentials of an external LDAP server.

The additional DECT specific settings are defined in the section fish-help.png Generall Settings. Here you have to make sure that the configured "Phone Book Number" (default value 999999) does not collide with existing numbers in the PBX.

Reverse Look Up - Resolve numbers on incoming Calls



For the internal calls from PBX users there is no need for resolving the numbers, since the calls are sent including the name of the PBX users. But if an external call is ringing on the DECT handset, there is no name information provided.

The section LDAP Directory Search DECT / Config / Master of the IP-DECT Master configuration provides the possibility to configure an external LDAP server for reverse number lookup. The settings here may be the same, you have used for usual number search under DECT / Config / Phone Book.

WinPDM Handset Management Software

In smaller installations with only few DECT handsets the deployment can be done directly on the DECT handset without any additional tools. For bigger installations with large number of handsets or if a firmware update of the handset is required, a programming charger and software WinPDM can be used to perform firmware updates of the handsets, apply configuration templates or change advanced settings of the handset.

You can find the WinPDM installation files together with DECT handset firmware under V9 Downloads, chapter Wireless.

Regarding the usage of the WinPDM Software please refer to the WinPDM Installation and Operation Manual from the innovaphone homepage, available under Services -> Downloads -> Data Sheets from other vendors (en).

Troubleshooting

LDAP Replication


While replicate users from Master PBX to IP-DECT Master, make sure to use LDAP credentials with write permissions, otherwise it is not possible to assign subscribed DECT handsets to users.

SARI


Make sure you use unique SARI in you DECT system. Otherwise, if two different DECT systems using the same SARI are installed nearby, subscribing and using handsets will fail on random basis.

The SARI configured on IP-DECT Master will be “lost” from configuration, if Master is disabled and IP1202 is rebooted. You have to configure the SARI again after this.

Handset Subscription


To subscribe a DECT handset you have to use Authentication Code, configured under DECT / Config / System. The IP1202 will suggest one if you activate IP-DECT Master – make sure you confirm and save this suggested Authentication Code by clicking on the OK button.

You can activate check the trace to see what happens while the handset tries to subscribe. Go to Maintenance / Diagnostics / Tracing and activate DECT Master and DECT Radio/PP-Manag. , than start continuous trace and monitor the output.

If this message appears:
DECTMASTER: no Mobmaster defined or master not active,
subscribing anonymous PPs is not allowed, reject request,
ipei 036470858703.
, following causes for this behaviour must be checked:
  • Subscription Method "With User AC" is selected, but IPEI of the subscribing DECT handset is not configured at any PBX User
  • the IPEI is assigned to a User on other IP-DECT Master

Handset Subscription


The registration from IP DECT MAster to the PBX is done for every DECT User and uses Name as Registration Credential. Therefore it is important to leave Nemo of the User Object under Devices as Hardware ID (
screenshot.png see an example).

Site Survey

When planning a new IP-DECT system we must do a site survey in the installation site to define the number of base-stations required to cover the area in a satisfactory level.

With a site survey we need to find answers for the following questions:
  • Find out the clients specific requirements of coverage and call capacity
  • Determinate the number of IP1202 necessary.
  • Decide base station positions for best Air sync and speech coverage possible.
  • Avoid/remove all radio interference on the site to have best performance/stability and call quality.
Without doing a site survey we could not guarantee that IP-DECT system will work properly for the costumer needs because different environments have different requisites.

That's why site survey must be a mandatory step for any IP-DECT implementation.

Note: On IP1202 we could have good Air Sync coverage but bad call speech coverage because Air Sync between base stations could be establish at higher distances than handset calls.
We must check always the speech coverage overlaps between IP1202 to avoid creating any no-coverage zones.

A Site Survey Kit for IP1202 could be order, more information on wiki for this Site Survey Kit

Things to consider:

  • When placing the base station, aim for free sight to the users
  • Do not mount the base station closer than 30cm to a metal construction
  • Analyse speech quality to check if it's a reflective environment.
  • Use the IP1202 in deployment mode to decide the distance between the base stations.
  • Good documentation of measurements.
  • Avoid unsynchronised alien DECT systems.

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A site survey is required to determinate the number of the IP-DECT base stations and their optimal placement.

After performing the site survey you will know:
• where to place the Base Stations
• coverage areas for the handsets
• areas with disturbances caused by reflective environments or rogue DECT systems

Speech and Air Sync Coverage

On a site survey we must determinate two different types of coverage:


  • Speech coverage - the radius of the circle (circular radiation patterns of the IP1202 antennas are assumed for reason of simplicity), around particular IP1202, in which portable parts can communicate with that IP1202, see figure below.
  • Air Sync coverage - the radius of the circle, around a particular IP1202, in which other IP1202 can synchronize with that Base Station with a given synchronization loss probability. This means that the size of the sync radius depends on requested probability of losing synchronization, see figure below.


Coverages Radius


  • Speech coverage higher -68 dBm - Area where a call can be done with a good voice quality.
  • Air sync coverage higher -83 dBm - Area where a sync slave can synchronize to another base station.


Adjacent cells must have a good overlap to ensure a proper handover and speech without disturbances (value less than 6 dBm).

coverage overlap

Different signal strengths effects:
  • -30 dBm, handset very close to the base station
  • -68 dBm, handset will start roaming (looking for better IP1202)
  • -75 dBm, speech affected
  • -90 dBm, risk for dropped calls

Base Station Coverage

This section describes how architecture, building elements, and special areas affect the coverage and the placing of the base stations.

The radio environment or the cell that is covered by a base station is not of a spherical shape as often suggested in figures. If a snapshot could be taken of its form, it would become clear that its shape is much more irregular. The momentary size and shape are dependant on the material of which walls and floors are made, the position and material of furniture, machines, air-conditioning and the position of the base station in such an environment.

Because of these unpredictable conditions it is not possible to give any hard rules on calculating the number of base stations in a given situation.

  • The in-house cell size in offices can have a radius of between 10 and 30 metres, see Example of the locations of base stations in a building.. The cell size in exhibition or production halls can have a radius of up to 200 metres.
  • The free space (outdoors) cell radius can be up to 300 metres.
  • Base stations may partially cover the floors immediately above and below. The useful range through floors and ceiling varies between 0 and 8 m (2 floors) radius; see Example of the locations of base stations in a building.

Architecture


This section describes how the architecture of the building can affect the coverage.

  • Central areas giving access to stairs and lifts may require extra base stations due to heavier constructions.
  • Coverage in lifts may require base stations closer to or in the lift shaft.
  • Corners and irregularities in the construction such as partial renovation, extensions of older buildings, and so on have influence.
  • Concentration of air-conditioning ducts or other technical installations may influence the field pattern and thus the coverage.

Coverage Architecture

Building Elements


This section describes how different building elements can affect the coverage.
  • The cell size is dependant on the material of which walls, ceilings and floors are made.
  • Plain, light or reinforced concrete, wood and plaster absorb and pass radio waves in different ways.
  • Metal walls and large metal cabinet rows reflect all signals, resulting in a greatly reduced coverage in areas behind these objects.
  • X-ray rooms in hospitals protected by lead walls and computer rooms in banking buildings protected against unwanted interference do not allow radio signals to enter.
  • Exhibition halls or production halls may give reflections due to large metal structures. This causes interference which reduces the capacity and coverage range of the base station.

Walls


Walls, ceilings and floors have large impact of the coverage range, different types of walls have different impact on the signal range. For list of the most common types and the approximate range achieved through these materials, see the table below.

Type
Examples
Range in meters
Stud wall Plaster 30-60
Concrete
10-30
Reinforced concrete Fire wall 0-10
Stone/brick
30-50
Metal A panel on brickwork 0-10
Wood
30-60
Wired glass Fire protection 0-10
Surface coated float glass Only of importance for coverage outside if the base station is installed inside 30-50
None Open-plan office or outdoors 150-300

Note: The values in this table are estimated values. Furniture (cupboards etc.), and the amount of movement in the area to be covered, for example, cranes in a production hall (see also Reflective Environment) are further factors that affect the coverage range.

Ceilings and Floors


The difference between ceilings and floors compared to walls lies in the materials used. Concrete and reinforced concrete are the main materials and it is important to determine the level of coverage of a base station on the floor above and below. For ‘normal’ concrete this coverage extends to a radius of approximately 15-20 metres which provides coverage for the floors below and above. An open stairwell or an atrium can in some cases be used to provide coverage to two floors at the same time, see Base station covering two floors.

Base station covering two floors


Fire-resistant walls/doors


The same facts applies for fire walls as for normal walls mentioned in the section above. However, fire doors are usually open during the site survey, it is important to close the fire doors before doing the final site survey measurement and before finalising the base station plan. Should a fire break out and the doors then be closed, there must of course still be sufficient coverage.

Special Areas


This section describes a number of special areas which must be considered when doing a base station planning, and how to ensure full DECT coverage in these areas.


Outdoors/car park


Coverage outdoors is usually not a problem since there are few or no obstacles. The base station location depends on the client and on the size of the area to be covered. If the client wishes to have as few base stations as possible installed outside (because of the costs of the outdoor housing), it is possible to install one or more base stations with the antennas in front of a window.


The base station must be able to ‘see’ as much as possible of the outdoor area to be covered (that is, there must be as few obstacles as possible between the base station and the covered area). Ensure that a measurement is carried out in order to check how much coverage a base station provides to the outdoor area, the intention is not to install all the base stations in front of windows, since this is not the ideally position to provide indoor coverage (normally 1-2 base stations are sufficient).


Type of glass
Range in meters
Normal glass 150-300
Surface coated float glass 30-50
Wired glass (fine-mesh) 0-20


Lift


If coverage in lifts are desired, locate the base station close to the lift, preferably at the front in a way that the base station can ‘see’ the front. This is because a lift is usually surrounded on three sides by a reinforced lift shaft, with the only opening being at the front. Locating a base station in front of a lift is usually not the most ideal position for the planning as a whole. It is usually the case that one or more extra base stations will be required to provide coverage for a lift. The base station will generally also provide coverage for the storey above and below the floor on which it is installed.

Stairwell


The major problem with stairwells is that they are often sited in a corner of the building. Coverage is not a problem in itself, but it must be seen in the context of the overall planning. There are various ways of providing coverage for a stairwell. Either the base station is installed directly in the stairwell as a dedicated base station for the stairwell, or it is installed in the close vicinity of a stairwell. The method depends on the type and location of the stairwell (is it an open or closed stairwell; is it sited in a corner of the building or in the centre and so on).

Toilet Rooms


Toilet rooms are generally in awkward positions for a site survey: behind or next to lifts, in or next to stairwells or in a corner of the building. A base station installation in the toilet room itself can be considered. If placed outside the toilet room it should be placed in the vicinity of the toilet room in a location where the base station can ‘see’ as much as possible of the toilet room (preferably the entrance because doors are generally made of wood and these damp the signal less than the walls).
If the base station is placed in the vicinity of the toilet room, locate it in a way that it provides coverage for as much of the rest of the floor as possible.

Maintenance Shaft


In larger buildings there is usually the requirement that coverage also be provided in maintenance rooms. The most common are the rooms for the lift and ventilation system. The lift maintenance room is often on the roof or in the basement. The ventilation maintenance room is usually on the roof. Do not omit these rooms they should be discussed with the client to avoid the client being faced with surprises. A well-positioned base station on the top floor (20 to 30 metres at most from the room where coverage is required) usually provides sufficient coverage for the maintenance rooms on the roof.

Basement and Indoor Car Park


It can be difficult to provide sufficient coverage in basements and indoor car parks due to the usually heavy constructions.

Use Site Survey Tool on IP63

We should use handset IP63 Site Survey tool function to make our site surveys and measure the Air Sync and Speech coverages of the IP1202 on the site.

How to use it:

First we should make subscription of the Handset on the IP1202 we are using, then Press *#77#.
This will give us the Site survey tool menu that have some options.

The most important to use will be Link, this option give us full details regarding the subscribed DECT system.

SurveyTool_Link

In the example:
C9 S3 - Current Carrier channel and TimeSlot
-34dBm - Received Signal Strength ( Should be less than -68 dBm to ensure good voice quality).
Error rate - show the amounts of bad frames per second which are received by handset (downlink).
Q2 Error rate - Shows the amounts of frames per second that Bad frames that are received by base station (uplink).
Bad frames occur when the received strength is low (<-68dBm) or in a reflective environment even if the signal strength is good.

Other informations are about the system and type of connection made so they are not relative to measure the coverage and signal quality.

Note: For speech quality test we can use IP61 together with included headset on Innovaphone Site Survey Kit. This will give us clear sound for better analyze of voice quality.

Possible disturbances

We could have disturbances on our Dect System caused by many factors. One of them are the Alien DECT (other Dect system on the area,ie Residential DECT) and reflective environments.


  • Alien and Residential DECT Effect
    • Unynchronised Alien DECT systems consume twice as much radio capacity compared to a synchronized system.
    • Difficulty for DECT users in all systems to make a call.
    • If possible, remove all Residential DECT sets (ie. Gigaset).
    • If other DECT system is present in the same coverage area a stronger sync signal is required (at least 6 dB stronger).

Coverages_Aliendect


  • DECT in Reflective Environments
    • Characteristics
      • Large open halls
      • Metal walls and ceiling
      • Metal machinery
    • Impact on DECT system
      • Bad speech quality despite high field strength, i.e. close to base station
      • High frame error rate
      • Dropped calls
      • Many hand-over attempts
      • Necessary to decrease the distance between base stations to have less bad frames.

Step by Step Site Survey

Now that we know all the possible disturbances and values that we need to obtain good speech and air sync coverage plus we have the tools, we can start the site survey.

Prepare the Base Station and Site Survey Kit


Before starting a site survey prepare the Site Survey Kit and one IP1202 gateway. The IP1202 must be configured as usual with IP-DECT Master, PARI Master and Radio - just the Mode for IP-DECT Master must be set to "Deployment". This mode will allow us to subscribe handsets without PBX, do loopback calls by dialing any number to analyse speech quality and measure the Signal Strength. Also make sure to configure a static IP-Address on ETH0 interface.

Prepare DECT Handsets


Subscribe one IP63 in Base Station and select Link on Site Survey tool options.

Optionally we can subscribe other IP61 with Headset to analyze speech quality doing loopback calls or just use the same IP63.

Perform Site Survey



The following steps must be performed while making a site survey:
  1. Place the deployment base station in the middle of the deployment area and on sight to have the most useful coverage area.

  2. Determinate the maximum distance from the base station to the IP63 where signal strength is -68 dBm and mark the radius. This will be speech coverage.

  3. Determinate the maximum distance from the base station to the IP63 where signal strength is -83 dBm and mark the radius. This will be sync coverage. Make sure to use different marker colours for Sync and speech radius.

  4. Move the IP1202 to a new position inside the sync coverage previous marked, following the same principles of middle area with most sight possible.

  5. Determinate the sync and speech coverage. Make sure to have speech coverage overlap to the previous position.



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