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EDITORIAL |
Case study: How to upgrade a TDM based infrastructure to Voice over IP
Present scenario of the customer
The present infrastructure of the customer is built on a TDM exchange with maximum capacity of 3500 subscribers and 3 linksets.
Actually the customer almost reached the maximum capacity achieving 3460 subscribers and 3 linksets. The interconnection between TDM Exchange and the PSTN network is made through 5-7 E1 interfaces (3 SS7 linksets).
Upgrade needs
The maximum system capacity is almost reached and the customer need an additional upgrade of 2000 SIP users. The customer needs are translated in a capacity of 2000 users and 12 E1 interfaces. The E1 interfaces will be used such as:
- 5 E1 for the connection to the PSTN network
- 5 E1 for the connection to the TDM exchange
- 2 E1 for the connection of the 2000 SIP users to PSTN
TOPEX solution suitable to accomplish the customer requirement is composed from a carrier grade multiSwitch solution and an EoneS signaling converter.
TOPEX multiSwitch achieves the call control function of the calls between the PSTN network, TDM exchange and SIP users. Also the multiSwitch features the SIP Registrar module which allows the registration of the SIP users - in that case 2000 SIP users.
The Softswitch performs multiple functions, such as:
- Controls connection services for a media gateway, and/or native IP endpoints
- Provides the ability to select processes that can be applied to a call
- Provides routing for a call within the network based on signaling and customer database information
- Has the ability to transfer control of the call to another network element
- Takes care of management functions such as provisioning, fault, billing, etc
TOPEX EoneS allows the interconnection between SIP users and TDM Exchange users, SIP users and PSTN network and maintain the connection between TDM Exchange users and PSTN network.
Proposed solution by TOPEX
TOPEX considers that the 5 E1 between PSTN and EoneS and 5E1 between EoneS and TDM Exchange are enough for assuring the proper capacity for the analog users.
For the SIP users we consider that the customer will need more that 2E1to connect to PSTN or TDM Exchange for the SIP users. 2E1 means 60 simultaneous calls and for 2000 SIP users a proper number of simultaneous calls will be 10%*2000 = 200. This is a statistically value.
So we propose additional 4E1 to assure a maximum capacity of 6E1 to VoIP meaning 180 simultaneous calls.
This upgrade is translated only in the addition of several E1 and VoIP boards in the EoneS and not an additional equipment.
Some key advantages of TOPEX are that:
- TOPEX offers complete solution for VoIP implementation,
- TOPEX Softswitch is scalable allowing for implementation of VoIP networks with a capacity varying 500 subscribers and going up to possibly thousands of subscribers, going even higher to hundreds of thousands and millions of users when clustering multiple Softswitches,
- TOPEX offers full assistance during the interconnection trials with other PSTN carriers and helps in configuration of the Softswitch and gateways.
In the end TOPEX solution for the initial customer is composed of TOPEX multiSwitch - which is the name of TOPEX Softswitch and TOPEX EoneS signaling and media gateways. This solution works either with SIP (Session Initiation Protocol) telephones or with ATA (Analog Telephony Adapter) - for the cases when the users do not want to change their telephones and an adapter between analogue phone and VoIP is needed. This solution is the best choice for the small-medium operators that would like to upgrade their services.
The advantage with this solution is that it offers much faster Return Of Investment then the classical TDM voice solutions. TOPEX Softswitch architecture allows starting with a small number of VoIP users, upgrading in future when you have more subscribers and the prices for the equipments and their maintenance is significantly lower then in the case of classic PSTN infrastructure.
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