Introduction TETRA over IP

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Introduction TETRA over IP

• Bert Bouwers
• Rohill Technologies B.V.

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Agenda

• TETRA-over-IP (ToIP) basics
• Benefits of TETRA-over-IP
• Myths about TETRA-over-IP
• Potential difficulties and concerns
• Guidelines for ToIP system evaluation
• Summary of facts

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TETRA-over-IP basics

• Use the Internet Protocol (IP) to connect Base
  Stations and SwMI together
• Real TETRA-over-IP requires efficient mechanisms
  to transport both call setup signalling and
  speech / data traffic
• ToIP is a compromise solution. There is a
  considerable debate whether IP is the best
  solution or should be avoided.

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TETRA-over-IP networking

• Can be deployed over any IP network
• Internet
• Intranet
• Local Area Network (LAN) using Ethernet
• Transparent operation over
• Routers
• Switches
• Hubs

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Conventional TETRA network
Network Management
Line Dispatcher
SwMI
IP gateway, Firewall
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TETRA-over-IP network
Network Management
Line Dispatcher
ISI / IPI gateway
Telephony gateway
Database server
Ethernet LAN
IP gateway, Firewall
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Benefits of TETRA-over-IP (1)

• One architecture for multiple purposes
• Transport of TETRA traffic and signalling
• Exchange of Status, SDS and Packet Data
• Integrated platform for Network Management (SNMP,
  HTTP)

Network Management
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Benefits of TETRA-over-IP (2)

• Large part available as COTS

• Routers and switches

• PC based platforms for database servers and
  telephony gateways

• System software Windows or Linux

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Benefits of TETRA-over-IP (3)

• Support of virtually any type of network topology

Star topology
Ring topology
Meshed topology
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Benefits of TETRA-over-IP (4)

• Resilience for link failures
• If proper network topology is selected

• Resilience for network component failures
• If distributed and replicated databases and
  redundant TETRA network components are used

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Does ToIP save costs ?

• NO, not really, because
• A separate, private IP network is needed for ToIP
  to prevent delays and ensure security
• Additional routers are needed to interconnect the
  IP components to line circuits (Synchro-nous V.35
  / V.11, ISDN, DSL, Frame Relay)
• IP uses more bandwidth because of packet headers
  (IP, UDP, TCP)

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Is ToIP a standard ?

• NO, not really, because
• Current ToIP solutions are not compatible with
  industry-standard Voice-over-IP (VoIP) standards,
  such as H.323 and SIP
• Each manufacturer has defined its own protocols
  for call establishment, transport of speech,
  database synchronization, etc.
• IP is not the same as Ethernet optimizations on
  the Ethernet level may prevent the use of
  standard IP router equipment

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Why not use H.323 or SIP ?

• Additional call setup delay because of
  negotiation through MGC or Gatekeeper
• Additional speech delay due to increased packet
  length and session control
• No TETRA ACELP gateways available on the market,
  thus transcoding is needed to realise an open
  solution, resulting in degradation of speech
  quality

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Potential difficulties of ToIP

• Extra speech and call setup delay caused by
  serialisation of data packets within radio sites
  and IP routers
• Jitter caused by queuing of packets in IP
  infrastructure requires additional buffering of
  speech packets
• Risk of packet loss or delayed packets due to
  network congestion

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Additional concerns

• Prioritisation of different packets
• TETRA speech traffic needs higher priority then
  call setup, SDS and Network Management
• Should be based on open standards,
  otherwisebenefits of using COTS will disappear

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How to deal with these difficulties

• Use plenty of extra bandwidth to ensure low
  serialisation delays and reduction of packet
  delay and packet loss typically four times
  minimum required bandwidth
• Establish a separate IP network for networking
  TETRA system components
• Use QoS mechanisms such as MPLS to allow
  prioritisation of IP packets

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Criteria for system evaluation (1)

• Required bandwidth for IP links
• Is it available and also cost effective ?
• Are the proposed IP routers and links suitable
  for mission-critical applications ?
• Evaluate reliability of equipment (MTBF)
• Observe link reliability avoid DSL and WLAN !
• Level of resilience in case of link failures
• Is the network topology designed in such a way
  that continuous operation is ensured in case of
  link failures ?

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Criteria for system evaluation (2)

• Level of system resilience
• Are databases replicated for redundancy ?
• Are the proposed link bandwidths sufficient for
  database synchronisation all over the network ?
• Is the system based on open standards and
  platforms ?
• Multi-vendor availability of routers, switches
• Hardware platform and operating systems
• Can the equipment be networked with standard IP
  routers, not only on Ethernet level ?

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Summary of Pros and Cons

• Offers a convergent network for TETRA speech,
  signalling, messaging and network management
• Potential to use COTS equipment and software
• Potential to provide resilience in case of link
  failures
• Networking flexibility find optimum balance
  between link cost and resilience

• Extra bandwidth required for overhead of IP
  packets
• Extra call setup and speech delay caused by
  serialisation of data over low-speed links
• Risk of packet loss and non-sequential arrival of
  packets
• Additional cost for router equipment
• IP equipment and networks not always suitable for
  mission-critical applications

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Conclusion

• IP is a proven solution for data transport, and
  maturing for real-time voice transport
• For mission critical use, including encryption,
  protocols and platforms have to be
  substantionally optimized
• Use of IP will increase price and require
  sufficient bandwidth on each site
• Increase of call setup time and speech delay is
  unavoidable

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• Thank you for your attention !
• Questions ?

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Glossary (1)
Definition
Abbrev.
Description
ACELP
Algebraic Code-Excited Linear Predictive
ETS 300 395-2
COTS
Commercial Off The Shelf
-
DSL
Digital Subscriber Line
TS 101 388
HTTP
Hyper Text Transfer Protocol
RFC 2616
IP
Internet Protocol
RFC 791
IPI
Internet Protocol Interworking
EN 301 747
ISDN
Integrated Services Digital Network
TBR 003
ISI
Inter System Interface
EN 300 392-3
LAN
Local Area Network
IEEE 802.3
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Glossary (2)
Definition
Abbrev.
Description
MGC
Media Gateway Controller
RFC 3054
MPLS
Multiprotocol Label Switching
In progress
MTBF
Mean Time Between Failure
MIL-HDBK-217
PABX
Private Automated Branch Exchange
-
PC
Personal Computer
-
PSTN
Public Switched Telephone Network
-
QoS
Quality of Service
See RFC 2990
SDS
Short Data Service
EN 300 292-2
SIP
Session Initiation Protocol
RFC 3261
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Glossary (3)
Definition
Abbrev.
Description
SNMP
Simple Network Management Protocol
RFC 1157
Switching and Management Infrastructure
SwMI
EN 300 392-1
TCP
Transmission Control Protocol
RFC 793
TETRA
Terrestrial Trunked Radio
EN 300 39x
ToIP
TETRA over Internet Protocol
-
VoIP
Voice over Internet Protocol
See SIP/H.323
UDP
User Datagram Protocol
RFC 768
WLAN
Wireless Local Area Network
IEEE 802.11