How ViBE Technology Helps
Vibe ( Voice over IP Broadband Enhancement ) solves these problems in several important ways:
- Future development of the technology will allow multiple links to be used as a single large bandwidth connection, offering a viable alternative to costly private circuits.
- Much more of the capacity of the link can be used.
- Backup links can be implemented which can be activated without losing calls in progress.
- Sites that have Vibe links can be joined together to form private networks, which means that security is easier to control.
- Voice and data can readily coexist on a single link. Data transfer rates are not compromised by the fact that voice is present. Classes of data can be given their own share of available bandwidth in a much more granular way than traditional QoS.
- The bandwidth budget required is reduced to that of the compression format used so that a G.729 call really does only use 8Kbit/s over the ADSL link rather than the 42Kbit/s which is more usual. Rather than a maximum of three calls, twenty-eight calls are now practical on a single broadband line.
- Voice is no longer treated as simply another type of data which happens to have a high priority. Instead, it is treated as a data stream with very specific requirements not only in terms of priority but also in terms of spacing between packets.
- Quality of Service is implemented in a completely different way to traditional methods, is much more suited to slower links.
The Problems Associated with Broadband ( ADSL ) Links and Voice
On the face of it, broadband should be a medium which is ideally suited for linking multiple sites for the purposes of voice and data, as well as VoIP links to external telephony providers. However, there are some very real problems associated with using voice and data over an ADSL network.
- The asynchronous nature of ADSL means that there is much lower bandwidth upstream when compared to down. Since voice calls are by their very nature symmetrical in terms of bandwidth requirements, the number of simultaneous conversations that can be maintained is limited by the much slower upload speed ( typically 256Kbit/s. )
- Voice information can be compressed ( using similar techniques to MP3 music compression ) to use only 8kbit/s per call. However, due to the way in which it is packaged to be sent over a broadband network, the reality is that each call will use at least 42kbit/s – significantly higher.
- In order to allow voice and data to share the same network, QoS has to be employed. Standard QoS techniques do not work very well for voice carried over links with less than about 1000Kbit/s and are not ideal even well above that. The effect of this is that voice information gets delayed because it has to wait for a free slot on the link in order to be sent – since peoples voices do not generally incorporate such delays this causes issues with voice quality.
- In addition, standard QoS techniques cannot allocate more than 70% of the available link bandwidth reliably. This means that on a standard broadband link, three calls is the absolute maximum that can sensibly be achieved, and the quality of those calls will still suffer where data is present.
- On a standard BT Wholesale broadband link, no QoS can be applied in the download direction.
- Broadband is usually part of a public or at least shared network, making security a concern.
