IPTV Limitations
IPTV is sensitive to packet loss and delays if the streamed data is unreliable. IPTV has strict minimum speed requirements in order to facilitate the right number of frames per second to deliver moving pictures. This means that the limited connection speed/bandwidth available for a large IPTV customer base can reduce the service quality delivered.
Although a few countries have very high speed broadband-enabled populations, such as South Korea with 6 million homes benefiting from a minimum connection speed of 100Mbps, in other countries (such as the UK) legacy networks struggle to provide 3-5Mbps and so simultaneous provision to the home of TV channels, VOIP and Internet access may not be viable. The last mile delivery for IPTV usually has a bandwidth restriction that only allows a small number of TV channels – typically from one to three – to be delivered.
The same problem has also proved troublesome when attempting to stream IPTV across wireless links within the home. Improvements in wireless technology are now starting to provide equipment to solve the problem.
Latency
The latency inherent in the use of satellite internet is often held up as reason why satellites cannot be successfully used for IPTV, but in practice latency is not an important factor for IPTV. An IPTV service does not require real-time transmission, as is the case with telephony or videoconferencing services.
It is the latency of response to requests to change channel, display an EPG, etc that most affects customers’ perceived quality of service, and these problems affect satellite IPTV no more than terrestrial IPTV. Indeed, command latency problems, faced by terrestrial IPTV networks with insufficient bandwidth as their customer base grows, may be solved by the high capacity of satellite distribution.
Satellite distribution does suffer from latency – the time for the signal to travel up from the hub to the satellite and back down to the user is around 0.25 seconds, and cannot be reduced. However, the effects of this delay are mitigated in real-life systems using data compression, TCP-acceleration, and HTTP pre-fetching.
Satellite latency can be detrimental to especially time-sensitive applications such as on-line gaming (although it only seriously affects the likes of first-person shooters while many MMOGs can operate well over satellite internet), but IPTV is typically a simplex operation (one-way transmission) and latency is not a critical factor for video transmission.
Existing video transmission systems of both analogue and digital formats already introduce known quantifiable delays. Indeed, existing DVB TV channels that simulcast by both terrestrial and satellite transmissions, experience the same 0.25s delay difference between the two services with no detrimental effect, and it goes unnoticed by viewers.
A small number of companies supply most current IPTV systems. Some, such as Imagenio, were formed by telecoms operators themselves, to minimise external costs, a tactic also used by PCCW of Hong Kong. Some major telecoms vendors are also active in this space, notably Alcatel-Lucent (sometimes working with Imagenio), Ericsson (notably since acquiring Tandberg Television), NEC, Thomson, Logic Innovations, and ZTE, as are some IT houses, led by Microsoft. California-based UTStarcom, Inc., Tennessee-based Worley Consulting and Tokyo-based The New Media Group also offer end-to-end networking infrastructure for IPTV-based services, and Hong Kong-based BNS Ltd. provides turnkey open platform IPTV technology solutions. Global sales of IPTV systems exceeded 2 billion USD in 2007.
Many of these IPTV solution vendors participated in the biennial Global MSF Interoperability 2008 (GMI) event which was coordinated by the MultiService Forum (MSF) at five sites worldwide from 20- to 31-October 2008. Test equipment vendors including Empirix, Ixia, Mu Dynamics and Spirent joined solution vendors such as the companies listed above in one of the largest IPTV proving grounds ever deployed.