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Quality Assurance: Voice Quality Tests
Since its inception VoIP has been plagued with reports of poor
voice quality. This is the reason for the delayed acceptance of
this technology. Broadband and other improvement in technology has
improved the quality of voice. These have made VoIP an acceptable
alternative to PSTN and traditional telephones. Yet for all we still
possess many of the old equipment and would like to use them as
a means of saving costs on new equipment.
This creates a bottleneck in VoIP traffic and hence deteriorates
voice quality. Many times a lay person is at loss to understand
where the fault lies. He calls the customer care only to find the
blame being laid on equipment, ISP or some other factor. The customer
has no way to find the exact problem and has to depend on the service
provider or the equipment provider for fault location and service.
The solution is voip testing to find the fault.
Factors Influencing Voice Quality
The broad areas that are causes of concern in any network are
- Delay or latency, which is the time taken for a signal
to travel from the caller to the recipient. IP network delay is
caused by packets traveling through multiple hops. The traversal
of the packet is through a variety of equipment. The standard of
acceptance is below 100ms for delay.
- Jitter is a variable change of strength of the signal.
This causes jumbling and makes communication difficult. The standard
for jitter delay is below 40 ms
- Echo in the network is caused when the data/voice stream
changes the network. The transition from a 4 wire Electromagnetic
Circuit to a 2 wire Fiber optic line is a place it can occur. A
reflection of the user’s voice back to him can cause annoyance
and degraded voice quality. Many gateway products come with G.165
echo cancellation software, which lessens excessive echo.
- Clear voice is dependent on general signal strength and
fidelity. This can be affected by processes that are required in
the transmission of voice over the internet. Voice Compression,
Packet loss and Voice transcoding affect clarity of voice. Compression
is done so as to get more effective bandwidth for transmission.
- This usually shrinks the data by removing silence and redundant
bits. Packets are lost on the internet network when it cannot reach
the destination or if there is congestion in the network. Compression
algorithms determine the effect of packet loss in the quality if
the signal. G.729 A is efficient when there is Packet loss where
as G 726 is more susceptible to packet loss. Voice transcoding is
use of multiple compression algorithms on a single voice stream.
A compressed signal after one gateway is further compressed. This
can deteriorate the voice quality and add delay in the voice signal.
- Service Providers are in a way responsible for voice quality
as well. The voice stream travels on a network and the quality of
the circuit elements affect clarity of the voice. Also the number
of users in a given bandwidth if increased causes breaks and lower
bandwidth available to others on the network. In case of VoIP over
a WAN network limiting the installation and maintenance to s single
provider is wise.
Continue to : VOIP Tools for Voice Test
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