Hi All ,
Find below a brief comparison of various voice technologies.
PLEASE REMEMBER FOR A PUR VOICE NETWORK TDM IS THE BEST CHOICE IN TERMS OF QOS, BANDWIDTH EFFICIENCY ETC. USING VARIOUS COMPRESSION ALGORITHMS .
G729A BEING THE BEST CHOICE FOR A PURE VOICE NETWORK.
Cheers !!!!!
Sanjay
NETWORK DELAY AND JITTER
Key ingredient for good voice is
low delay
Delay can be measured as
Average length of time for packet to move
Variability in the arrival of packets
A jitter buffer nullifies the effect of variation
Latency is sum of above two
A latency of 200 – 250 msec makes a bad voice
Example consider network with 50 ms avvg delay but some part goes as high as 200-250 msec
A Jitter buffer of 10 msec will have low delay but will miss delayed packets
A jitter buffer of 200 msec will compensate for late packets but increase latecy
Hence Dynamic Jitter Buffering is a must criterion for Bandwidth Managers
COMPARING TECHNOLOGIES
TDM
Quality of Voice : HIGHEST
Provides predictable and consitent quality of voice
Does not suffer from effects of Latency, Jitter
Bandwidth Efficiency :
Very High for a pure voice network
Poor for a multiservice network
Cost : Cheapest
Effictive support for Multiservices: Poor
FRAME RELAY
Quality of Voice :HIGH
Provides very good quality of voice under optimal conditions
Does not lower efficiency on implementing solutions for Latency, Jitter
Bandwidth Efficiency :
High for a pure voice network
Very efficient for a voice/ data network
Cost :Medium
Effictive support for Multiservices: Good
VOIP
Quality of Voice : Optimal to poor
Provides very good quality of voice under optimal conditions
lowest efficiency on implementing solutions for Latency, Jitter
Bandwidth Efficiency :
Very Low for a pure voice network
Not very efficient for a voice/ data network
Most efficient for data Networks
Cost : Medium
Effictive support for Multiservices: Low
TECHNOLOGY FOR PURE VOICE NETWORK
Dynamic Bandwidth Allocation is not an issue
Voice Quality is of paramount importance
Bandwidth efficiency is significantly important
TDM is the best choice to meet the above requirement
TECHNOLOGY FOR VOICE /DATA NETWORK
Dynamic Bandwidth Allocation is an important issue
Voice Quality is of significant importance
Bandwidth efficiency is paramount importance important
FRAME RELAY is the best choice to meet the above
DELAY OR LATENCY
Caused By:
algorithmic processing delay
frame delay (size of frame)
transmission delay
General Rule:
Delay approaching 32 ms requires echo cancellation
Delay is a function of transport technology also
Choice of Technology has bearing on
1.Bandwidth Efficiency
2.Delay
3.Jitter
AND HENCE ON VOICE QUALITY
Choice of Technology is also governed by
Type of traffic running viz voice only or multiservices
Whether Dynamic Bandwidth allocation desired
QOS Requirement in multiservices
SOLUTIONS FOR JITTER
Variation in delay for Packet voice due to Network Congestion
Does not apply to Circuit Switched TDM
Happens when a large packet has already transmitted resulting in a voice packet waiting
Solved using techniques like fragmentation etc.
BUT
EFFECTS OF FRAGMENTATION ON EFFICIENCY
Fragmentation results in creation of large no. of data packets
Each packet has to have a packet overhead
Packet overhead of FR is much lesser than IP
IP overhead reduces WAN Efficiency by 10 – 15 %
FR overhead reduces by 2-4 %
COMPARING PACKET TECHNOLOGIES ON QOS :
FR offers higher levels of prioritization
ATM offers highest levels
IP is very limited in this aspect
TECHNOLOGY FOR PURE VOICE NETWORK
Dynamic Bandwidth Allocation is not an issue
Voice Quality is of paramount importance
Bandwidth efficiency is significantly important
TDM is the best choice to meet the above requirement
SANJAY BANGROO