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scheduler and in section 4 we show the superiority of the proposed scheduler by
simulation. Finally, in section 5 we summarize the paper.
2 Related Work
IEEE 802.11e HCCA Protocol
IEEE 802.11e was proposed to guarantee QoS in Wireless LAN. It supports for
QoS based on prioritized and parameterized method, and is called HCF which
consists of EDCA and HCCA. The EDCA is the prioritized protocol which en-
hanced Distributed Coordination Function, and it provides differentiated and
distributed service for QoS with access categories(AC). AC is divided into four
priorities by the trac types, and its service is independent of others and com-
petes with others for channel occupancy.
Since HCCA controls the channel access directly, it can control the channel
access more precisely than EDCA. HCCA is the parameterized protocol which
enhanced Point Coordination Function, and allocates TXOP and SI to each sta-
tion in accordance with its TSPEC parameters. The main TSPEC parameters
are described below.
Delay Bound (
): The maximum time allowed between arrival time of MSDU
at the local MAC layer and start time of MSDU at the local MAC layer.
Nominal MSDU Size (
): Nominal size of the MSDU in octets.
Minimum Physical Rate (
): Physical bit rate assumed by the scheduler for
transmit time and admission control calculations, in units of bits per second.
Maximum size MSDU (
): Size of the MSDU in octets.
Mean data rate ( ρ ): Average bit rate for transfer of the packets, in units of
bits per second.
Maximum Burst Size (
): Maximum size of the data burst that can be
transmitted at the peak data rate, in octets.
Minimum Service Interval (
): Minimum time between the start of suc-
cessive TXOPs allocated to the station, in units of microseconds. Given a service
interval for each TSPEC (calculated as
/ ρ ), the mSI contained in the service
schedule is equal to the smallest service interval for any TSPEC.
Maximum service interval (
): Maximum time allowed between the start
of successive TXOPs allocated to the station, in units of microseconds.
Minimum TXOP duration (
): Minimum TXOP duration allocated to
the station. The
is equal to the maximum packet transmission time for any
of the stations TSPECs. The maximum packet transmission time of a TSPEC
is the time required to send a packet of size M at the minimum
PHY rate.
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