Introduction TETRA over IP
description
Transcript of Introduction TETRA over IP
Introduction TETRA over IP
Bert BouwersRohill Technologies B.V.
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
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
PABX, PSTN,ISDN
Intranet /Internet
Other TETRAnetwork
NetworkManagement
LineDispatcher
IP gateway,Firewall
SwMI
TETRA-over-IP network
PABX, PSTN,ISDN
Intranet /Internet
Other TETRAnetwork
NetworkManagement
LineDispatcher
ISI / IPIgateway
Telephonygateway
IP gateway,Firewall
Databaseserver
Ethernet LAN
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)
NetworkManagement
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
Meshed topology
Ring 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 (Synchro-nous 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, otherwisebenefits 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 non-sequential 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)
ACELP Algebraic Code-Excited Linear Predictive
DefinitionAbbrev. Description
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
Glossary (2)
MGC Media Gateway Controller
DefinitionAbbrev. Description
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
Switching and Management Infrastructure
SNMP Simple Network Management Protocol
DefinitionAbbrev. Description
RFC 1157
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
Glossary (3)