Both technologies
could yield similar performance results yet only one could be selected. Until EFM
forced a decision, both technologies had progressed equally through ITU and ANSI T1
standards bodies, with no organization able to select a single solution.
After many months of debate, the EFM task force voted to use VDSL-DMT as the
physical layer for 10PASS-TS instead of VDSL-QAM. The hope that VDSL-DMT could
leverage the technology and volume of ADSL (which is also based on DMT technology)
was a key factor in the selection process.
Figure 5.1 IEEE 802.3ah architecture diagram
Media Access Control (MAC)
Reconciliation
MII
Rate matching
Loop aggregation
64/65-octet encapsulation
Physical layer
64/65-octet encapsulation
Physical layer
Traditional
ethernet layers
New ethernet
layers
Existing ITU
Physical layers
134 Chapter 5
Spectral Compatibility and International Applications
As an international standard, it is important for Ethernet to be deployable anywhere in
the world. EFM technologies are basis systems, which means they are universally deployable
throughout the world. These technologies are capable of operating under different
spectral guidelines depending on where in the world they are deployed.
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