Transcript Benefits of TETRA-over

Introduction TETRA over IP
Bert Bouwers
Rohill Technologies B.V.
Agenda
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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
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.
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
Conventional TETRA network
SwMI
Network
Management
Line
Dispatcher
Other TETRA
network
Intranet /
Internet
IP gateway,
Firewall
PABX, PSTN,
ISDN
TETRA-over-IP network
Other TETRA
network
ISI / IPI
gateway
Intranet /
Internet
Network
Management
Line
Dispatcher
Database Telephony
server
gateway
Ethernet LAN
IP gateway,
Firewall
PABX, PSTN,
ISDN
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
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
Benefits of TETRA-over-IP (3)
• Support of virtually any type of network
topology
Star topology
Ring topology
Meshed topology
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
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 (Synchronous V.35 / V.11, ISDN, DSL, Frame Relay)
– IP uses more bandwidth because of packet
headers (IP, UDP, TCP)
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
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
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
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, otherwise
benefits of using COTS will disappear
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
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 ?
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 ?
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 nonsequential arrival of packets
– Additional cost for router
equipment
– IP equipment and networks
not always suitable for
mission-critical applications
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
Thank you for your attention !
Questions ?
Glossary (1)
Abbrev.
Description
Definition
ACELP
Algebraic Code-Excited Linear Predictive
ETS 300 395-2
COTS
Commercial Off The Shelf
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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
Glossary (2)
Abbrev.
Description
Definition
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
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PC
Personal Computer
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PSTN
Public Switched Telephone Network
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QoS
Quality of Service
See RFC 2990
SDS
Short Data Service
EN 300 292-2
SIP
Session Initiation Protocol
RFC 3261
Glossary (3)
Abbrev.
Description
Definition
SNMP
Simple Network Management Protocol
RFC 1157
SwMI
Switching and Management Infrastructure
EN 300 392-1
TCP
Transmission Control Protocol
RFC 793
TETRA
Terrestrial Trunked Radio
EN 300 39x
ToIP
TETRA over Internet Protocol
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VoIP
Voice over Internet Protocol
See SIP/H.323
UDP
User Datagram Protocol
RFC 768
WLAN
Wireless Local Area Network
IEEE 802.11