English version

HiperLAN/2 : a Quality of Service enabling Wireless LAN

 

 

[ Introduction ]

[ H/2 Standard ]

[ TCL H/2 Prototype ]

[ Animated Tour ]

Prototype performances

[ TCL Activities ]

 

 

Throughput performances: an example with TCP

The brutal throughput drop experienced by TCP traffic when transmitting over an error-prone medium is a well known flaw. The efficiency of HiperLAN/2 ARQ error control mechanism, associated with short PDU size, allows the system to sustain a user throughput on top of TCP layer of more than 25 Mbit/s in harsh radio conditions, i.e. with a Packet Error Rate (measured at MAC level) as high as 5%.

 
       Delay performances
A HiperLAN/2 system is able to keep delivery delays short in very hard propagation conditions. Figures below give an example of the Automatic Repeat Request (ARQ) error control mechanism efficiency. Though no discard mechanism is implemented, delays remain short: the average delivery delay for 1514-byte packets is kept under 10 ms. HiperLAN/2 is therefore able to support real time applications requirements, in terms of latency and error rate.
This performance can be achieved thanks to the high reactivity of H/2 ARQ mechanism that is able to retransmit an erroneous packet within 2 ms. 

With a PER up to 7%, 70% of retransmissions induce an overall latency of less than 4 ms.

* List of Acronyms