SlingSecure 2G and 3G technology transmission channels depend on the type of product: 2G or 3G.

Transmission Delay:

  • SlingSecure 2G CSD: v32 and v110 0,8 sec
  • SlingSecure 3G GPRS: 3 sec
  • SlingSecure 3G EDGE: 1.5 sec
  • SlingSecure 3G UMTS: 0.5-1 sec
  • SlingSecure 3G WIFI: 0.5-1 sec

Latency depends approximately on:

  • Audio Coding (1%)
  • Encryption/Decryption Routines (1%)
  • Serialization and Queuing (20%)
  • Network Processing (78%)

SlingSecure 2G 2G technology means that SlingSecure for establishing the secure connection uses a CSD data connection with a maximum of 9.6 Kbps of throughput channel. Circuit Switched Data (CSD) is the original form of data transmission developed for the time division multiple access (TDMA)-based mobile phone systems like Global System for Mobile Communications (GSM). CSD uses a single radio time slot to deliver 9.6 kbit/s data transmission to the GSM Network and Switching Subsystem where it could be connected through the equivalent of a normal modem to the Public Switched Telephone Network (PSTN) allowing direct calls to any dial-up service.

In order for SlingSecure 2G to work properly, the SIM card operator should activate the CSD data channel for sending and receiving data calls (Mobile Originated/Mobile Terminated). Some operators limit such service to just postpaid/business contracts while refusing activation requests which involve prepaid cards. When enabling CSD data channel, the operator usually assigns two additional numbers to the SIM card: the first number is reserved for voice calls (and it’s the one the SIM card gets issued with), the second number is reserved for data transmission, the third for faxes. Even if three numbers have been assigned to the SIM card being employed for encrypted calls, usually the main number can be used for all purposes (voice and crypto). SlingSecure 2G uses the modem of the phone to establish the communication by means of the standard protocol v32 or v110; those two operation mode differ in handshake duration and information transmitted at the beginning of the connection. With v32 protocol, almost 20 additional seconds are required for the voice channel to get open; moreover some operators require that the call gets directly routed to the data number assigned to the SIM card. The v32 protocol is rather old and used only in few countries in the world. On the other hand, with the v110 protocol (the same used in ISDN modems for Internet browsing) the connection is almost immediate. It usually doesn’t require to dial the data number, it is enough to dial the voice number of the SIM and the data call get automatically routed to the SIM. SlingSecure 2G enables the user to set two additional modem settings: Transparent and Non Transparent.

Those settings refer to the transport layer of the modem. Non transparent involves a data flow control and a retransmission of the data that arrive with wrong timing or corrupted. This retransmission causes an increase of the delay of the communication but less audio gaps during the communication. Transparent is usually preferred because in real time communication such as voice conversations it is a better choice that of having low delay and eventually lose some fractions of seconds when data are corrupted rather than hearing empty gaps lasting seconds. Standard default settings of SlingSecure 2G is v110 and Transparent and this is the optimal setting for most European operators. SlingSecure 2G can be used all over the word but some operators (mainly in Africa or South/Central America) do not implement the CSD data service in their networks because it is normally not used by normal customers and it is – from their low level point of view, not customer’s – more expensive than GPRS/EDGE connection because they have to reserve a full timeslot on the network as if it was a voice call instead of using a best effort politic like in GPRS/EDGE that usually have high delay.1.3 SlingSecure 3G3G technology involves the use of all kind of internet connection available to the phone. With the UMTS technology it is possible to take advantage of the broadband capabilities of new networks and having a voice encoding quality higher than 2G while keeping the delay as low as possible. Using an internet connection involves the use of a server that acts as a switch between the users.

The call is no more routed by operator between voice and data number, it is no more necessary to ask for any service activation/number but only the normal internet connection is needed. The encrypted voice connections between users are made possible through the use of SlingSecure Server that blindly routes the encrypted data without any elaboration or manipulation. The communication is always encrypted end-to-end straight from user to user. SlingSecure has developed a proprietary VoIP protocol not compatible with SIP or any other industry standard because of the need of a fast, light, secure and efficient protocol designed to be used in mobility and in NATted networks. With this approach, the communication is not easily identified so it can bypass filters in networks that do not allow SIP connections. SlingSecure 3G can indifferently use mobile network like UMTS or WIFI, in this way it is possible to use freely the connectivity available in office/home/airport/public hotspot . The communication can start with WIFI and pass automatically to the mobile network as soon as the user is out of the WIFI range without interrupting the conversation.

The protocol was designed for mobility so the codec adapts dynamically the voice coding quality to the bandwidth available. This means that on GPRS/EDGE connections, the quality will be a little lower but still sufficient to have good clearness. The delay and the jitter vary dynamically depending on the performances of the network for having the best tradeoff between delay and quality. Best performances are available under UMTS or WIFI coverage so 3G technology is recommended to customers that uses the SlingSecure devices mainly in big cities (with good UMTS coverage) or in office/home or for international/intercontinental connections because of better performances/quality/usability/cost efficiency. SlingSecure 3G important feature is the complete anonymity of the connection between users because endpoints cannot be traced from the bill of the operator. What can be gathered from the operator receipt or detailed phone bill is simply the connection to an internet server. One additional benefit is that customers – with the aid of technical aids – can test the strength of the encrypted stream and check that is really secure without the need for special instruments for the interception of the stream.