Glossary(19)
Terms used as applied to Data (and some Voice) Transmission over Copper Wire
  Q

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QAM
QoS

 

 

 

QAM (Quadrature Amplitude Modulation) -- A two dimensional modulation used in cable, analogue (voice grade) and xDSL modems.

QoS - Quality Of Service - A group of service classes defined by the ATM forum in terms of different QoS parameters:

  • Class 0 refers to the best effort service (UBR).
  • Class 1 specifies the parameters for circuit emulation, and the transport of CBR uncompressed video and for VPNs. AAL1 supports this kind of delay sensitive connection oriented service.
  • Class 2 specifies the parameters for the transport of VBR (low speed or compressed packetized) audio and video. AAL2 supports this delay sensitive, connection oriented class.
  • Class 3 specifies the parameters for connection oriented data transfer. AAL3/4 and mostly AAL5 supports this delay tolerant class which is intended to provide interoperability with SMDS and IP.
  • Class 4 specifies the parameters for connectionless data transfer. AAL3/4 or AAL5 can be used to support this delay tolerant class which is also intended to provide interoperability with SMDS and IP.
  • Class X refers to the connection oriented transport service where the traffic type (CBR or VBR) and timing requirements (delay sensitive or non-sensitive) are defined by the user. It is known as an unrestricted service class and which is supported by AAL5.

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