User's Manual

RTL8187B
Datasheet
Wireless LAN Network Interface Controller
30
Track ID: JATR-1076-21 Rev. 1.0
11.5. Rx Decapsulation (With RTL8187B Internal Baseband
Processor)
The RTL8187B continuously monitors the network when reception is enabled. When activity is recognized
it starts to process the incoming data. After detecting receive activity on the channel, the RTL8187B starts
to process the PLCP preamble and header based on the mode of operation.
The RTL8187B checks CRC16 and CRC32, then reports if CRC16 or CRC32 has errors. When using the
40-bit WEP and 104-bit WEP module for decryption, the RTL8187B also checks the Integrity Check Value
(ICV) and reports if the ICV has errors.
11.6. QoS Functions
The RTL8187B supports WMM, WMM Scheduled Access, and IEEE 802.11e functions.
11.7. Contention-based Admission Control Functions
Refer to Section 9.9.3 of the IEEE 802.11e specification for greater detail.
The ATL (Admitted Time Limit) is a statically set value which determines the maximum transmission time
a class can have.
Software keeps track of admitted time per access that requires admission control. Upon receipt of a
successful response frame, the non-AP QSTA adds the admitted time variable for the specified EDCAF to
the value contained in the Medium Time field of the TSPEC element. The non-AP QSTA then starts a
five-second timer. The non-AP QSTA shall update the value of used time:
A. At five second intervals
used_time = max ((used_time-admitted_time), 0)
B. After each successful or unsuccessful MPDU (re)transmission attempt,
used_time = used_time + MPDUExchangeTime
If the used_time reaches or exceeds the admitted time value, the corresponding EDCAF sets the
corresponding bit in the ACM_CONTROL register to 1. The corresponding EDCAF may then choose to
temporarily replace the EDCA parameters for the EDCAF with those specified for an access category of
lower priority, if no admission control is required for those access categories.