SpectraLink IP-DECT Server 400, IP-DECT Server 6500, DECT Server 8000, DECT Server 2500 Synchronization And Deployment Manual

14169000-IG, Edition 11.0
January 2018, Original document
Spectralink IP-DECT Server 400/6500 and DECT Server 2500/8000
Synchronization and Deployment Guide
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Notice
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Contents
Introduction 5
Scope 5 Before You Begin 5 Related Documentation 6 Terminology and Acronyms 7
AboutSynchronization 10
Types of Synchronization 10
Off-site Planning, Prior to Visit 11
If Customer Wants to Replace Existing IP-DECT/DECT System 11
Is it an IP-DECT base station or a digital DECT base station? 11 Investigate Site 11 "Conclusion" 13
On-site Investigation 14
Aligning Expectations With Customers 14
On-site Deployment 15
Deployment Tools 15 Important Parameters 17 Deployment Rules of Thumb 19 IP-DECT Base Station using Radio Synchronization (Over The Air) 19
Deployment Procedure 20 Placement of Base Stations 22
IP-DECT Base Stations using LAN Synchronization and Digital DECT Base Stations 24
Deployment Procedure 25 Placement of Base Stations 27
LAN BasedSynchronization 29
Precision Time Protocol Background 29 Deployment of Base Stations 30 Network Requirements 30
Multicast 31 Timing and Jitter 31 Network Topology 32 Traffic Load 32 Quality and Configuration of the Switches 33
Configurations and Administrations 34
IP-DECT/DECT Server System Settings 34 Base Station Individual Settings 34
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Base Station Synchronization Status 35
Troubleshooting 36
Synchronization 36
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5
Introduction
This guide is intended for qualified technicians who will deploy Spectralink IP-DECT/DECT Server Solutions. To qualify to deploy a IP-DECT/DECT Server Solution, you must have understood and completed the technical training successfully. This guide covers both 1G8 and 1G9 deployment.
Scope
The Synchronization and Deployment Guide provides instructions and best practices for deployment of the following solutions:
l Spectralink IP-DECT/DECT Server 8000 and 2500
l Spectralink IP-DECT/DECT Server 6500 and 400
The purpose of this guide is to familiarize you with the procedures that are needed to carry out a site survey as well as understand the requirements to ensure synchronization is successfully imple­mented. At the completion of this guide you should be comfortable with the following:
l Using a handset to measure and record Q - and RSSI values (RF values).
l Selecting a proper mounting location for base stations and repeaters.
l Making sure that the company LAN meets the LAN Synchronization requirement limits, and
documenting the deployment.
Before You Begin
This guide assumes the following:
l You have a working knowledge of deployment in general
l You have completed the technical training
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Related Documentation
For information about Server IP-DECT/DECT Server Solutions not covered by this manual, refer to the following documentation:
Subject Documentation
Spectralink DECT Handset For more information about the handset,
refer to the user guide available online at
http://support.spectralink.com/products.
Site Survey Function in Handset For more information about the handset,
refer to the user guide available online at
http://support.spectralink.com/products.
Spectralink IP-DECT/DECT Server For more information about the server,
refer to the guide available online at
http://support.spectralink.com/products.
Spectralink Technical News Newsletter that describes software
changes, bug fixes, outstanding issues, and hardware compatibility considerations for new software releases. To subscribe, go to
www.spectralink.com.
Spectralink DECT Training material
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Terminology and Acronyms
The table below refers to common terms and acronyms that are related to the Spectralink IP­DECT/DECT solutions.
Term Definition
Deployment The act of locating the mounting location and installing base
stations and repeaters. System performance is dependant on the deployment made - and, therefore, the survey per­formed.
Handover A process initiated by the handset in which the speech chan-
nel carrying an active conversation is passed from one base station to another.
Erlang The erlang is a dimensionless unit that is used in telephony
as a measure of offered load or carried load on service­providing elements such as telephone circuits or telephone switching equipment.
LED Light Emitting Diode
LI-Ion Lithium-Ion
Ni-MH Nickel -Metal Hydride
Q Value Signal Quality Factor value. An expression of the bit failure
rate in the communication between the handset and a base station. The value has a max. of 64, equal to no bit errors measured.
LAN synchronization Method for synchronizing IP base stations over LAN
Synchronization Over the Air (OTA) Method for synchronizing IP base stations over Air (radio)
SUOTA Software Update Over The Air
RF Radio Frequency
RSSI Value Radio Signal Strength Indication value. A relative expres-
sion for the signal strength of a base station as measured by the handset at a given location.
Site survey A site survey comprises the act of locating the best places
for base stations by measuring RSSI levels with DECT handsets. Complete survey consists of measuring with mul­tiple base stations, combining RSSI and Q value reading in real surroundings.
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Term Definition
Speech channel A speech channel is used to carry communication between
the handset and the base station or repeater.
AC Authentication Code
ARI no. Access Rights Identity - Serial number of the (missing or
bad snippet).
CLI Command Line Interface
dB Decibels (deciBells)
DECT Digital Enhanced Cordless Telecommunications
DHCP Dynamic Host Configuration Protocol
DNS Domain Name System
e.i.r.p. Equivalent Isotropic Radiated Power
GAP Generic Access Profile
HW PCS Hardware Product Change Status - Hardware edition
IP Internet Protocol
IPEI International Portable Equipment Identity - Serial number
of the handset - SN
IWU Inter Working Unit
Spectralink IP-DECT Server Spectralink IP-DECT Server400/6500
Spectralink DECT Server Spectralink DECT Server2500/8000
LAN Local Area Network
MAC Media Access Control - hardware address of a device con-
nected to a network
MTU Maximum Translation Unit
MWI Message Waiting Indication
NIC Network Interface Card
NTP Network Time Protocol
PBX Private Branch eXchange
PCS Product Change Status (Edition)
PoE Power over Ethernet
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Term Definition
PP Portable Parts - wireless handset
RSSI Received Signal Strength Indicator
RTP Real-time Transport Protocol
SIP Session Initiated Protocol
SW PCS Software Product Change Status - Software edition
TFTP Trivial File Transfer Protocol
UDP User Datagram Protocol
VoIP Voice over Internet Protocol
WLAN Wireless Local Area Network
WRFP Wireless Radio Fixed Part - Wireless Repeater
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AboutSynchronization
In a multi-cell DECT system the base station radios must be synchronized to each other in order to achieve the optimum handover experience, when handsets are moving around among base sta­tions. Spectralink supports synchronization of digital DECT base stations via the wire and IP-DECT base stations via the radio. Further, IP-DECT base stations can use corporate LAN for syn­chronization as well.
Types of Synchronization
l LAN Based Synchronization (Server 400/6500/2500/8000)
l Radio Based Synchronization (Over The Air) (Server 400/6500/2500/8000)
l Digital DECT Base Stations (Server 2500/8000)
Note:
Synchronization of digital DECT base stations is controlled by the server and requires no configuration. Therefore, configuration of digital DECT base stations will not be described further.
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Off-site Planning, Prior to Visit
Below you will find at list of questions and considerations to take into account during the planning phase prior to visiting a site.
If Customer Wants to Replace Existing IP-DECT/DECT System
Is it an IP-DECT base station or a digital DECT base station?
l IP-DECT base station:
o
Consider PoE, Active equipment, Switch PoE.
o
Is this reusable for the new system?
o
Do LAN switches support LAN synchronization?
l Digital DECT base station:
o
Can the cabling be reused? (yes/no/partly)
Investigate:
o
Is all cabling twisted pair end to end (recommended equal to CAT5e)? Is cabling present where DECT coverage is needed?
o
Are all junction points of good quality?
o
From these investigations the costs to get cabling up to a satisfactory standard can be estimated.
Note:
Today new systems can be a combination of wired and IP.
Investigate Site
l What is the site?
o
Are there more buildings?
o
If there are more buildings - consider the distance between the buildings, and whether it is possible to establish synchronization between base stations.
o
Are there more sites (sub-sites)?
o
If there are several sites - the remote site(s) (i.e. those where it will not be possible to establish synchronization) must be IP-DECT/DECT system(s).
l Study blueprints of building
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o
Consider the building materials
o
More dense materials means less radio propagation and therefore more base stations
o
Environment
o
Moving interior (warehouse, production facility). Much equipment moving around will influence the propagation
o
Metal can cause reflections which will influence propagation (i.e. metal blinds, metal beams, metal shelves, rebars, shielding foils)
o
Where are fire doors/walls placed? These will influence propagation
l System usage
o
Where are people placed? (those that will use the IP-DECT/DECT system)?
o
Are there areas with (extra) high voice-traffic load like:
o
Canteen
o
Nurse office
o
Etc.
l Rough estimation of equipment (if possible)
A rough/budgetary estimate of equipment/base stations can be calculated according to below:
o
Open area (indoor)
o
Office area
o
DECT systems: [Size of area to cover in m2]/800 = number of digital DECT base sta­tions Necessity: approximately 25 m between the base stations and 15 m overlap to enable handover.
o
IP-DECT systems (Radio Synchronization): [Size of area to cover in m2]/600 = number of LAN base stations Necessity: approximately 22 m between the base stations and overlap from base station to base station.
IP-DECT system (LAN synchronization): [Size of area to cover in m2]/800 = number of LAN base stations Necessity: approximately 25 m between the base stations and 15 m overlap to enable handover.
Note:
Be aware that this will not be an exact figure. A deployment of the site will be necessary to get a correct number.
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"Conclusion"
Based on the above analysis, the installer must be able to determine whether to install a Spectralink DECT Server or Spectralink IP-DECT Server or a combination.
l IP-DECT/DECT systems with IP-DECT base stations can benefit from synchronization over
LAN
l Digital DECT base stations have 4/8 channels whereas IP-DECT base stations have 11 chan-
nels
l Digital DECT base stations and IP-DECT base stations with LAN synchronization can have
longer distance between base stations as opposed to IP-DECT base stations with Radio syn­chronization (Over The Air (OTA)).
Synchronization is essential for handing over calls from one base station to another.
Radio Synchronization (OTA)
LANSynchronization and Digital DECT Base Stations
Note:
Before going on a site, remember to have confirmation from the customer regard­ing accessibility to all areas where the customer needs IP-DECT/DECT to make measurements for deployments.
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On-site Investigation
Below you will find considerations to take into account when investigating a site.
Aligning Expectations With Customers
l Start your on-site visit with meeting the customer and align expectations to coverage (areas)
and dropped calls (expect 2-3-% dropped calls).
l Take a walk around the premises to create an overview and check that the information
uncovered during the pre-planning phase is correct/valid.
Consider:
o
internal structure material
o
moving interior
o
are there materials that affect/absorb propagation
o
is the interior as expected?
l Create a rough overall plan for how to execute the deployment.
l If deploying IP-DECT base stations with Radio synchronization, create a blueprint with base
station placement and synchronization chain.
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On-site Deployment
Deployment Tools
Bring the following tools on a site for deployment:
l 1 Spectralink IP-DECT Server 400
l 1 Battery pack min. 8V/max. 60V
l 1 Tripod (app 2m high)
l 1 Cable with RJ45 plug (pin 1 must be connected to pin 3, pin 2 must be connected to pin 6)
Note:
Preferably the tripod shall place the Spectralink IP-DECT Server 400 at the height where you will place the server/base stations/repeaters in the final installation.
If 2 people perform the deployment at IP-DECT sites, you shall also bring:
l Minimum 1 Spectralink DECT repeater (the repeater must be set up to synchronize on the
Spectralink IP-DECT Server 400 used for the deployment).
l 9V Battery pack
l 1 Tripod (app 2m high)
l 1 Cable to connect battery pack and Spectralink DECT repeater (with RJ11 plug in for the
repeater) For a description of pin connections, see the information on the Power Supply.
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Also bring:
l 2 handsets
o
1 Spectralink Standard Handset (7522/7532, 7622/7642, 7722/7742).
Note:
The handset can only measure correctly when off hook.
When measuring, carry the handset with your hands covering the antennas to assimilate normal user conditions (heads or surroundings blocking the radio sig­nals when holding the handset to the ear).
o
1 Spectralink DECT Handset of any type.
l Consider also to bring a device you can use to play sound in the handset.
l A good idea would be also to bring a laptop with network cable to connect with the Spectralink
IP-DECT Server 400.
l If you bring a repeater, you should also bring power supply for the repeater, and repeater pro-
gramming kit (Product ID: 02509210).
l When bringing a repeater, you must also bring a serial to USB converter to be able to connect
the repeater to the laptop.
l It could also be beneficial to bring a power supply for the Spectralink IP-DECT Server 400.
For more information about using the handset for deployment, see Site Survey Function in Handset User Guide.
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Important Parameters
When deploying, there are 3 parameters which are equally important:
l RSSI values: Value indicating signal strength
l Q value: Value indicating the signal quality (preferably steady at 64)
l Sound Quality: Measured by walking away from the base station with the handset and meas-
ure where the RSSI value drops below 75 and the Q value stays constant at 64.
Example and Description of Values (RPN, RSSI, Quality) (Only relevant to Spectralink Handset 7202/7212/7522/7532/7622/7642/7722/7742)
Descriptions of the values above:
l RPN (Radio Part Number) values range from 0 - 255.
l RSSI (Received Signal Strength Indicator) values range from 35 - 124. Counting down from
124.
l QV (Quality) values range from 0-64.
A signal quality of 64 is a connection without errors, this number will be reduced by one for each error (such as reflections or noise). Preferably this value should be steady at 64.
l FTS ( Frequency, Timeslot, State)
o
Time slot values range from 0 to B (there are 12 time slots)
o
State: E = Economy mode active. B, C indicates if last handover was a connection han­dover or a bearer handover.
Note:
To only see handover type, disable Economy mode in the handset menu (Set­tings > Advanced > Economy mode).
l First line shows that the actual base station has RPN number 14, signal strength (RSSI) 124,
signal quality of connection is 64, 99C means ninth frequency, time slot 9, and that the last han­dover was a connection handover (C).
l Last four lines are candidates for connection handover (if any). Only the RSSI value and the
RPN value is shown.
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Descriptions of RSSI colours:
RSSI
Green > 80 RSSI/- 70 dBm
Yellow < 80 RSSI/- 70 dBm and
> 70 RSSI/- 80 dBM
Red < 70 RSSI/- 80 dBM
Example and Description of Values (RPN, RSSI, Quality) (Only relevant to Spectralink Handset Butterfly)
Below is an example of RPN values:
l The hexadecimal numeral system is used to describe RPN values and time slots. RPN values
range from 00 to FF.
l Time slot values range from 0 to B (there are12 time slots)
l Third line shows that the actual base station has RPN number 8, signal quality of connection is
64, signal strength (RSSI) 108, 3BC means third frequency, time slot B, and that the last han­dover was a connection handover (C).
l A signal quality of 64 is a connection without errors, this number will be reduced by one for
each error (such as reflections or noise). Preferably this value should be steady at minimum
64.
l The value of signal strength range from 110 to 35. Counting down from 110.
To Check RSSI values in Handset
1. Press Menu to enter main menu.
2. Scroll to Status, and press Select.
3. Scroll to RSSI, and press Select. The bearer quality is shown in the display.
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Deployment Rules of Thumb
l Be systematic
l Document
l Do not assume - Measure
IP-DECT Base Station using Radio Synchronization (Over The Air)
Note:
It is recommended to deploy a system as a star system with the sync master placed in the middle.
Necessary overlap in synch chains Necessary overlap between synch chains
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Deployment Procedure
Start by placing your tripod with the Spectralink IP-DECT Server 400 (from your deployment tools) where you plan the first base station (the sync master) to be:
Take picture of the placement and note it on a blueprint of the building.
l Remember to consider that the first base station (sync master) shall be placed centrally in the
installation so the rest of the system can spread from it (remember to consider all 3 dimen­sions.
Note:
Take picture of the placement and note it on a blueprint of the building.
l Make a call between the two handsets. During the deployment there must always be an active
call established.
Note:
Measurements are only valid on handsets in a connected call!
l Play music/talk into the handset without headset. Wear the headset and listen to the sound
quality all the time.
l At the same time as listening to the sound quality, use your handset to measure how far the
base station will cover sufficiently.
This is done by walking away from the base station with the handset and measure where the RSSI value drops below 75 and the Q value stays constant at 64. Do this in all dir­ections from the base.
For a description of the parameters and RPN values, see "Important Parameters" on page 17.
Note:
The handset can only measure correctly when off hook.
When measuring, carry the handset with your hands covering the antennas to assimilate normal user conditions (heads or surroundings blocking the radio sig­nals when holding the handset to the ear).
l To perform a site survey using a Spectralink Standard Handset (7522/7532,7622/7642,
7722/7742), enter Survey mode on the handset. For more information about using the
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handset for deployment, see Site Survey Function in Handset User Guide.
Note:
It is important to measure all places where coverage is required.
Do not assume that there is coverage - it has to be measured!
l Consider where to place the next base station so that the handset gets opportunity to han-
dover to the next base station. Determine where to place the next base stations.
l Move your tripod with the Spectralink IP-DECT Server 400 to the next placement.
Note:
Take picture of the placement and note it on a blueprint of the building.
l Continue until the whole site is deployed.
Note:
Remember to document each placement for base stations (incl. sync master).
o
Take pictures of where exactly the base station must be placed.
o
Note it on a drawing of the premises.
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Placement of Base Stations
When determining where to place the base stations, following points must be considered:
l To get maximum coverage from a base station the base stations must be as visible as pos-
sible.
l A guideline can be to consider where a light bulb can be placed to light up the maximum area.
RSSI 75
l Traffic – how many simultaneous calls can be expected in an area.
o
In an assembly area e.g. in a canteen there will probably be many simultaneous calls dur­ing lunch.
o
To get an estimate of the simultaneous calls Erlang can be calculated.
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l Sync latency in sync chains.
l Propagation through building materials – dense materials influence propagation negatively.
Base stations shall be placed away from reflecting materials like metal.
l Base stations shall be placed away from other DECT base stations.
l “When in doubt deploy”, i.e. to ensure a good coverage place one more rather than one less
base station.
l A good documentation of the deployment is needed to build the synchronization chains.
Note:
Take picture of the placement and note it on a blueprint of the building.
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IP-DECT Base Stations using LAN Synchronization and Digital DECT Base Stations
In IP-DECT/DECT systems, it is important to ensure an overlap on the base stations at all timers of 15 m to ensure a call can be handed over at normal walking speed.
Note:
Synchronization between the digital DECT base stations is not an issue in these sys­tems, as synchronization between the base stations is handled automatically by the DECT servers.
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Deployment Procedure
Start by placing your tripod with the Spectralink IP-DECT Server 400 (from your deployment tools) where you plan the first base station to be:
l Place the first base station in a corner of the building so there is coverage in the corner.
Note:
Take picture of the placement and note it on a blueprint of the building.
l Make a call between the two handsets. During the deployment there must always be an active
call established.
Note:
Measurements are only valid on handsets in a connected call!
l Play music/talk into the handset without headset. Wear the headset and listen to the sound
quality all the time.
l At the same time as listening to the sound quality, use your handset to measure how far the
base station will cover sufficiently.
This is done by walking away from the base station with the Site Survey Handset and meas­ure where the RSSI value drops below 70 and the Q value stays constant at 64. Do this in all directions from the base stations.
For a description of the parameters and RPN values, see "Important Parameters" on page 17.
Note:
The handset can only measure correctly when off hook.
When measuring, carry the handset with your hands covering the antennas to assimilate normal user conditions (heads or surroundings blocking the radio sig­nals when holding the handset to the ear).
l To perform a site survey using a Spectralink Standard Handset (7522/7532,7622/7642,
7722/7742), enter Survey mode on the handset. For more information about using the
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handset for deployment, see Site Survey Function in Handset User Guide.
Note:
It is important to measure all places where coverage is required.
Do not assume that there is coverage - it has to be measured!
l Note how far the place is from the tripod with the Spectralink IP-DECT Server 400.
l Find the next place for the base station app 2 x the above distance from the first placement
l Consider where to place the next base so that the handset gets opportunity to handover to the
next base station.
l Move your tripod with the Spectralink DECT Server 400/2500. and measure whether this will
give sufficient overlay (i.e. RSSI value min 70, Q value stays constant at 64 and good sound quality) at the same place as measured at the previous placement.
l If necessary, move the base station to get sufficient overlay.
l When it is determined where to place the next base stations.
Note:
Take picture of the placement and note it on a blueprint of the building.
l Continue until the whole site is deployed.
Note:
Remember to document each placement for base stations (incl. sync master).
o
Take pictures of where exactly the base station must be placed.
o
Note it on a drawing of the premises.
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Placement of Base Stations
When determining where to place the base stations, following points must be considered:
l To get maximum coverage from a base station the base stations must be as visible as pos-
sible.
l A guideline can be to consider where a light bulb can be placed to light up the maximum area.
RSSI 70
l Traffic – how many simultaneous calls can be expected in an area.
o
In an assembly area e.g. in a canteen there will probably be many simultaneous calls dur­ing lunch.
o
To get an estimate of the simultaneous calls Erlang can be calculated.
l Propagation through building materials – dense materials influence propagation negatively.
Base stations shall be placed away from reflecting materials like metal.
l Base stations shall be placed away from other DECT base stations.
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l “When in doubt deploy”, i.e. to ensure a good coverage place one more rather than one less
base station.
l A good documentation of the deployment is needed to build the synchronization chains.
Note:
Take picture of the placement and note it on a blueprint of the building.
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LAN BasedSynchronization
Below you will find a description of how LAN based synchronization works, and what must be con­sidered when synchronizing.
Note:
LAN based synchronization only works when using a Spectralink Handset.
The latest generation of Spectralink IP-DECT Base Station s support the use of corporate Local Area Network (LAN) for synchronization of the DECT radios when running software release PCS15C or later.
In a multi-cell DECT system, the base station radios must be synchronized to each other in order to achieve the optimum handover experience, when handsets are moving around among base sta­tions. Spectralink supports the synchronization of digital DECT base stations via the wire and IP­DECT base stations via the radio. IP-DECT base stations can use the LAN for synchronization as well.
The LAN based synchronization has several advantagesover synchronizing via the radio. The con­figuration is much simpler because no synchronization chains need to be configured and maintained. The synchronization is self-healing, because the system itself can handle if any base station is failing. Finally, the system can be deployed with fewer base stations, because the base stations are no longer required to be in range of each other.
It may, however, not be the ideal solution in all cases. LAN based synchronization requires that the base stations involved in a handover are on the same network segment and the network deployment (including LAN switches) meets a number of quality criteria.
Precision Time Protocol Background
Precision Time Protocol version 2 (PTPv2) is used to synchronize the radios of the IP-DECT base station via the LAN. PTPv2 is defined in the standard IEEE 1588-2008 and a brief introduction can be found here: http://en.wikipedia.org/wiki/Precision_Time_Protocol.
PTPv2 is based on a master-slave architecture, where the active master is automatically selected among the base stations with the lowest serial number. Each network segment will have one active master and the remaining base stations will be slaves. If the current master is failing a new one will be automatically selected without disrupting the current synchronization state.
The PTPv2 datagrams are sent as multicast and transported via UDP on IPv4 or IPv6 or as raw Eth­ernet packets without IP.
The LAN based synchronization is administrated centrally from the web based Administration Page of the IP-DECT/DECT Server. The synchronization itself however is handled autonomously by the base stations, and the server is not involved and hence does not need to be on the same network segment.
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Deployment of Base Stations
When the base station radios are synchronized via radio, the base stations that synchronize to each other must be within radio coverage of each other. This is not required when LAN based syn­chronization is used. Here, the deployment requirements are the same as for the digital DECT base stations and the coverage overlap is only required for the handsets to be able to perform handovers. The figure below illustrates the difference in coverage requirementsfor radio and LAN based syn­chronization.
Radio synchronization LAN synchronization
It should be noted that depending on the deployment - Synchronization via LAN and radio can be combined in the same DECT installation. Even when a base station is configured to synchronize via LAN, it transmits the signal required for synchronization via radio. Therefore, base stations syn­chronizing via radio can retrieve their synchronization signal from a base station synchronizing via LAN. The other way around is not possible.
Network Requirements
For PTPv2 to work the requirements for the network are quite strict with regard to:
l multicast
l timing
Note:
LAN synchronization only works properly if multicast and timing requirements are met. An assessment of the corporate LAN network MUST be done to evaluate if the LAN net­work is suitable enough for LAN based synchronization.
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Multicast
The PTPv2 multicast packets cannot traverse routers and consequently the IP-DECT base stations that needs to be synchronized must be on the same switched network segment.
Regardless of the transport selected, IPv4, IPv6 or Ethernet, the network switches must allow mul­ticast traffic to and from all the LAN base stations. The multicast addresses used are listed below:
Protocol Multicast address
IPv4 224.0.1.129
IPv6 FF02::181
Ethernet 01:1B:19:00:00:00
If IPv4 or IPv6 is used as transport and IGMP snooping
(http://en.wikipedia.org/wiki/IGMP_snooping) is supported by the switch, the switch can utilize this to automatically configure on which ports the multicast packets should be sent. Note that this requires an IGMP querier to be present on the network segment (many IGMP snooping switches offers this functionality).
If multicast is not working properly on the network, the IP-DECT base stations will not be able to achieve LAN synchronization.
Timing and Jitter
For PTPv2 to be accurate enough to synchronize the DECT radios the network jitter must be low, that is the network packet delay must be close to constant.
The PTPv2 algorithms in the base stations have built-in filtering, which make them able to cope with some level of jitter. However, prolonged periods of large jitter can cause unstable or even loss of syn­chronization.
The corporate LAN must support the following specifications:
l Maximum of 500 nanoseconds jitter of multicast Ethernet packets between all IP-DECT base
stations being synchronized.
l Any single switch in the network cannot exceed 100nsec of jitter.
l PTPv2 event traffic must be given strict priority over all other network traffic.
l Multicast and the IGMP protocol (if used) must be configured per Spectralink requirements.
l Network topology
l The traffic patterns on the network
l The quality and configuration of the switches
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Network Topology
Every time a PTPv2 packet passes through a switch - jitter is potentially added. Therefore, the num­ber of switches between all base stations must be kept low. Because every individual base station can assume the role as PTPv2 master or slave regardless of its position in the network topology, a worst case position of master and slave must be considered when deploying the base stations in the network. The figure below illustrates this with a core switch with two access switchesconnected. Here the worst case path length is three switches.
Note:
In the lab, the IP-DECT base stations have successfully been synchronized with 5 enter­prise LAN switches between master and slave.
Traffic Load
The traffic load on the switches will also affect the jitter. High traffic load and especially a large num­ber of large packets will increase the jitter. For example, a 1500 bytes data packet introduces an immediate 120 usec delay on a 100 Mbps link.
It is recommended that the core network links provides higher bandwidth than the access links, i.e. if the access links are 100 Mbps, the uplink and core network should be at least 1 Gbps. This will alle­viate the probability of traffic saturating the network path used for the base station synchronization.
If the traffic load causes problems for the base station synchronization, it may be necessary to sep­arate the base stations from the data network. Be aware that separation via VLAN may not help as it is still using the same physical link.
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Quality and Configuration of the Switches
The LAN based synchronization is highly dependent on the quality and configuration of the deploy­ment network. The single most important property of the switchesin the network is their ability to for­ward multicast Ethernet packets with low jitter, i.e. close to a constant delay. The total forwarding jitter added by switches on any path through the deployment network should be less than one micro­second and preferably less than 100 nanoseconds.
Unfortunately, it is usually difficult to find the forwarding jitter specified for a given switch. Lab tests indicates that enterprise level switches generally has adequately low forwarding jitter, whereas SOHO and unmanaged switchesoften do not meet the requirements and thus must not be used.
When configuring the deployment network, multicast setup is critical for LAN synchronization to work. Multicast is usually either blocked, forwarded as broadcast to all ports, forwarded according to static configuration or forwarded to selected ports learned by IGMP snooping. The simplest option is to forward as broadcast to all ports, but this might create unwanted traffic on unrelated network parts. When using static configuration, the relevant multicast addresses listed earlier must be for­warded to the ports forming the deployment network. Enabling IGMP snooping on the switches allow them to automatically configure which ports the multicast packet should be forwarded to, min­imizing the network load caused by the LAN synchronization. In order to keep the multicast con­figuration updated, a IGMP querier must be present in the network – this functionality can be enabled in many enterprise class switches.
Traffic Priority:
All time critical PTPv2 packets sent by the LAN synchronization software is by default marked with either an Expedited Forwarding (EF) (46/0x2e) priority for IPv4 and IPV6 packets or a Class of Ser­vice value of 7 for VLAN encapsulated Ethernet packets. This is to allow the switches to give pref­erence to the LAN synchronization packets.
Since the Expedited Forwarding priority on IP packets is shared with voice RTP packets, this is not sufficient to ensure strict priority over all other traffic for the PTPv2 events packets.
There are two possible solutions to this:
l Give the highest priority to a custom IP priority and configure the server to apply this IP priority
to PTPv2 traffic.
l Give the highest priority to multicast UDP packets on port 319 with the destination address
224.0.1.129 (IPv4) or FF02::181 (IPv6).
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Configurations and Administrations
A few configuration settings on the Spectralink server's web based Administration Page are used to control base station synchronization via LAN.
IP-DECT/DECT Server System Settings
The system wide settings for synchronization via LAN are located under Configuration > Wireless Server > Base stations:
Field Setting
Default sync type This setting controls the default synchronization type for
new base stations. The following values can be selected:
l Free running
l Radio (default)
l LAN
LAN sync transport protocol This setting controls the protocol used as transport for
the PTPv2 packets used for synchronization. The fol­lowing values can be selected:
l Ethernet
l IPv4 (default)
l IPv6
IPv4 is the default and recommended in most networks.
Base Station Individual Settings
Field Setting
Type This setting controls the synchronization type for specific
base station. The following values can be selected:
l Free running
l Radio
l LAN
l Gateway
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Base Station Synchronization Status
The synchronization status is displayed on the Spectralink server'sweb based Administration Page under Administration > Base Stations.
The Sync column displays a green icon for base stations that are currently running as slaves and a blue one for the current master.
The Lost column displays the number of times the synchronization has been lost and a percentage which is the ratio of time the base station has been without synchronization. The lost counter must be low but is expected to grow slowly over time. The percentage will start high and must be zero after some time.
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Troubleshooting
In general, always check if there is newer software to be downloaded.
Synchronization
Symptom Problem Resolution
All base stations are syn­chronization masters.
Multicast traffic is blocked in the network.
Enable multicast traffic on all switches between the base stations.
Synchronization is OK at startup but fails after a short period.
IGMP snooping is active, but no IGMP querier is present on the network to refresh mul­ticast group memberships
Add an IGMP querier to the network or disable IGMP snooping.
Base stations do not synchronize or loose synchronization often.
The traffic between base sta­tions is being delayed a vary­ing amount of time due to traffic load, switch quality or configuration.
Reconfigure/replace switches or change the net­work topology to minimize the transmission time vari­ance.
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