IP telephony, which accounted for 44% of Sweden’s fixed line subscriptions by the end of June 2014 according to regulator PTS’ biannual survey, has seen significant improvements in quality in recent years leading to the number of customer complaints related to IP voice services now standing at the same level as traditional PSTN telephony, according to the latest report findings published by the watchdog this week.
The Swedish study notes that, to achieve adequate quality of voice-over-internet protocol (VoIP) telephony, basic requirements include a ‘bare minimum’ data transfer rate of 256kbps, whilst a high proportion of Swedes now have access to networks with speeds of over 20Mbps (download) and 6Mbps upload. Good quality VoIP also requires that the delay (latency) of the data packets is at an acceptable level, not normally exceeding 0.3 seconds, while other factors include: the Quality of Service (QoS – i.e. the prioritisation of voice traffic); the conversion of analogue to digital data and vice versa (including the ‘voice code’, e.g. G.711); an optimised design of the network; tailored customer premises equipment (CPE); custom administrative systems; and operational organisation of the service providers.