Note: Descriptions are shown in the official language in which they were submitted.
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FRAME CLASSIFICATION FOR QOS-DRIVEN WIRELESS LANS
Inventors: Jin-Meng Ho and Wei Lin
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is related to application Serial No. (Atiy docket IDS
2000-
0395), entitled An Architectural Reference Model for QoS-Driven Wireless LANs,
invented
by J.-M. Ho, and filed concurrently with the present application; and to
application Serial No.
(Atty docket IDS 2000-0396), entitled An In-Band QoS Signaling Reference Model
for QoS-
Driven Wireless LANs, invented by W. Lin and J.-M. Ho, and filed concurrently
with the
present application; and to application Serial No. (Atty docket IDS 2000-
0397), entitled
Virtual Streams for QoS-Driven Wireless LANs, invented by J.-M. Ho and W. Lin,
and filed
concurrently with the present application; and to application Serial No. (Atty
docket IDS
1 S 2000-0398), entitled Admission Control for QoS-Driven Wireless LANs,
invented by W. Lin
and J.-M. Ho, and filed concurrently with the present application; and to
application Serial
No. (Atty docket IDS 2000-0400), entitled Frame Scheduling for QoS-Driven
Wireless
LANs, invented by J.-M. Ho and W. Lin, and filed concurrently with the present
application;
and to application Serial No. (Atty docket IDS 2000-0401), entitled RSVP/SBM
Based
Down-Stream Session Setup, Modification, and Teardown for QoS-Driven Wireless
LANs,
invented by J.-M. Ho and W. Lin, and filed concurrently with the present
application; and to
application Serial No. (Atty docket IDS 2000-0402), entitled RSVP/SBM Based Up-
Stream
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Session Setup, Modification, and Teardown for QoS-Driven Wireless LANs,
invented by
J.-M. Ho and W. Lin, and filed concurrently with the present application; and
to application
Serial No. (Atty docket IDS 2000-0403), entitled RSVP/SBM Based Side-Stream
Session
Setup, Modification, and Teardown for QoS-Driven Wireless LANs, invented by J.-
M. Ho
and W. Lin, and filed concurrently with the present application; and to
application Serial No.
(Atty docket IDS 2000-0404), entitled Enhanced Channel Access Mechanisms for
QoS-
Driven Wireless LANs, invented by J.-M. Ho, and filed concurrently with the
present
application; and to application Serial No. (Atty docket IDS 2000-0405),
entitled Centralized
Contention and Reservation Request for QoS-Driven Wireless LANs, invented by
J.-M. Ho
and W. Lin, and filed concurrently with the present application; and to
application Serial No.
(Atty docket IDS 2000-0406), entitled Multipoll for QoS-Driven Wireless LANs,
invented by
J.-M. Ho and W. Lin, and filed concurrently with the present application; each
of which is
incorporated by reference herein. Additionally, the present application is
related to
application Serial No. (Atty docket IDS 1999-0408), entitled Voice-Data
Integrated
Multiaccess By Self Reservation and Blocked Binary Tree Resolution, invented
by J.-M. Ho
and filed June 19, 2000; and application Serial No. (Atty docket IDS 1999-
0409), entitled
Voice-Data Integrated Multiaccess By Self Reservation and Stabilized Aloha
Contention,
invented by J.-M. Ho, and filed June 19, 2000, each of which is incorporated
by reference
herein.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the fields of communications and networking.
More
particularly, the present invention relates to frame classification for QoS-
driven wireless
networks.
2. Description of the Related Art
With the advent of digital broadband networks, such as hybrid fiber-coaxial
networks
and 3G/4G cellular networks, packetized multimedia services to residential and
enterprise
environments are becoming not only a reality, but also a necessity. Wireless
delivery of, or
access to, multimedia applications, such as voice, video and data, is
considered viable for
helping accelerate this trend.
The transport of multimedia traffic over a shared network generally requires
specific
levels of quality of service (QoS) support for achieving predictable and
satisfactory network
service. Technically, QoS refers to the expectation of a session or an
application to receive,
as well as the ability of a network to provide, a negotiated set of service
values for data
transmission in terms of delay/jitter bound, mean/maximum data rate, and the
like. QoS is
enforced and supported by such techniques as effective congestion control,
adequate resource
reservation, proper traffic shaping, and prioritized bandwidth allocation.
With some degree
of QoS guarantees, shared channels furnish time-bounded and asynchronous
services that are
comparable to those of dedicated channels.
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Bandwidth utilization efficiency is another important consideration in the
design of a
multimedia network. High bandwidth utilization e~ciency leads to increased
channel
throughput and reduced access delay, thereby permitting the same channel
bandwidth to
serve more sessions/applications with given QoS levels. In the case of
bandwidth shortage,
maximizing bandwidth utilization efficiency minimizes the degradation of QoS
values
provided to active sessions/applications.
Unfortunately, wireless local-area networks (WLANs), such as currently
specified by
IEEE P802.11 /1999, do not support QoS transport and operate on a distributed
contention or
simplified polling basis. Consequently, only asynchronous and low-throughput
best-effort
data services are provided.
What is needed is a technique for transforming a WLAN into part of an end-to-
end
QoS network having enhanced channel access, thereby providing QoS support with
improved
bandwidth utilization.
SUMMARY OF THE INVENTION
The present invention provides a frame classifying technique for QoS support
in a
WLAN. The advantages of the present invention are provides by a frame
classification entity
(FCE) for a station in a basic service set (BSS) in a wireless local area
network (WLAI~.
The FCE includes a classification table. The classification table is logically
located at a
logical link control (LLC) sublayer of the station, and contains at least one
classifier entry.
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According to the invention, the station can include a point coordinator (PC)
or be a non-PC
station. Each classifier entry includes at Ieast a virtual stream identifier
(VSID), a search
priority value, and at least one classifier parameter. Each classifier entry
in the classification
table is arranged in a hierarchical order based on the search priority value
included in the
classifier entry. The FCE receives at least one data frame passed down to the
LLC sublayer
of the station from a higher layer in the station. The at least one data frame
is one of a
quality of service (QoS) data frame and a best-effort (asynchronous) data
frame. The QoS
data frame contains information included in at least one of the at least one
classifier
parameter of at least one of the classifier entries in the classification
table. The FCE then
classifies each received data frame to a VSID by examining the data frame
against the
classification table of the station. When the data frame is examined and the
VSID ofthe data
frame is contained in a classifier entry of the classif cation table, the VSID
is associated with
a QoS parameter set for transporting the data frame between peer LLC entities
of the BSS.
When the frame classification information contained in a received data frame
is not included
in any classifier entry in the classification table, result of classification
is expressed in a
special VSID that is not associated with a QoS parameter set and the data
frame is
transported between peer LLC entities of the BSS on a best-effort basis.
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BRIEF DESCRIPTION OF THE DRAWING
The present invention is illustrated by way of example and not limitation in
the
accompanying figures in which like reference numerals indicate similar
elements and in
which:
Figure 1 shows an architectural reference model for QoS support in a basic
service set
(BSS) over a WLAN according to the present invention;
Figure 2 shows an in-band QoS signaling reference model for QoS support over a
WLAN according to the present invention;
Figure 3 shows a diagram of virtual streams for QoS support over a WLAN
according
. 10 to the present invention;
Figure 4 shows a flow diagram for an admission control technique that can be
used
for QoS support in a WLAN according to the present invention;
Figure 5 depicts a process for classifying a frame that can be used in a QoS-
driven
WLAN according to the present invention;
Figure 6 shows an exemplary scheduling table that can be used for frame
scheduling
over a QoS-driven WLAN according to the present invention;
Figure 7 shows a signal path diagram for RSVPISBM-based down-stream session
setup, modification, and teardown over a QoS-driven WLAN according to the
present
invention;
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Figure 8 shows a signal path diagram for an RSVP/SBM-based.up-stream session
setup, modification, and teardown over a QoS-driven WLAN according to the
present
invention;
Figure 9 shows a signal path diagram for RSVP/SBM-based side-stream session
setup, modification and teardown over a QoS-driven WLAN according to the
present
invention;
Figure 10 shows a diagram for enhanced channel access mechanisms over a QoS-
driven WLAN according to the present invention;
Figures lla-llc respectively show exemplary arrangements of a super frame, a
contention control frame and a reservation request frame that can be used for
centralized
contention and reservation request over a QoS-driven WLAN according to the
present
invention; and
Figures 12a and 12b respectively show exemplary arrangements for a super&ame
and
a multipoll that can be used over a QoS-driven WLAN according to the present
invention.
DETAILED DESCRIPTION
The present invention provides an architectural reference model that
integrates the
lower layers (link and PHY layers) of a WLAN, as currently specified by IEEE
P802.11/1999, with the higher layers (network and higher layers) that appear
in the ISO/IEC
basic reference model of Open Systems Interconnection (0S1) (ISO/IEC 7498-1),
but not in
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IEEE P802.1 I/1999. Both the IEEE P802.1111999 and the ISO/IEC 7498-1
standards are
incorporated by reference herein. Additionally, the present invention provides
end-to-end
QoS mechanisms. Such integration instills the QoS parameter values from the
higher layers
into the lower layers, and enables the lower layers to provide QoS traffic
transport and
improved channel throughput.
Compared to the existing reference model, as specified in IEEE P802.11/1999,
the
present invention introduces an admission control entity (ACE), a QoS
management entity
(QME), a frame classification entity (FCE), and a frame scheduling entity
(FSE) for a point
coordinator/access point (PC/AP) station (STA). The.present invention also
introduces a
QoS signaling entity (QSE), a QoS management entity (QME), a frame
classification entity
(FCE), and an optional frame scheduling entity (FSE) for a non-PC/AP STA. The
ACE and
the QSE may each be part of the QME. Further, the present invention introduces
a Virtual
Stream (VS) Update management frame for exchange of VS management information
between a PC/AP STA and a non-PC/AP STA.
Figure 1 shows an architectural reference model for QoS support in a basic
service set
(BSS) over a WLAN according to the present invention. Figure 1 shows an
exemplary BSS
that includes a PCIAP STA and two non-PC/AP STAs x and y. While only two non-
PC/AP
STAB are shown in Figure l, it should be understood that any number of non-
PC/AP STAB
could be part of the BSS shown in Figure 1.
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The PC/AP STA shown in Figure 1 includes an admission control entity (ACE)
that
is part of a QoS management entity (QME). Alternatively, the ACE can be a
separate entity
that operates in conjunction with the QME. The PC/AP STA also includes a frame
classification entity (FCE) that is logically located in a logical link
control (LLC) sublayer of
the PCIAP STA. The QME interfaces with the FCE., which maintains a frame
classification
table containing frame classifiers that are used for identifying QoS parameter
values
associated with a frame. The PC/AP STA further includes a frame scheduling
entity (FSE)
logically located at a medium access control (MAC) sublayer of the PC/AP STA.
The QME
interfaces with the FSE, which maintains a frame scheduling table that
contains scheduling
information for scheduling transmission of frames. The PC/AP STA includes a
conventional
station management entity (SME), which is separate from the QME. The SME
interfaces
with a conventional MAC sublayer management entity (NIZ,ME) and a conventional
physicai
layer management entity (PLME). The MLME interfaces with the MAC sublayer,
whereas
the PLME interfaces with a physical layer. The physical layer comprises a
conventional
physical layer convergence protocol (PLCP) sublayer and a conventional
physical medium
dependent (PMD) sublayer.
Each non-PC/AP STA includes a local QME that interfaces with a local FCE. The
local FCE is logically located at the LLC sublayer of the non-PCIAP STA and
maintains a
local frame classification table. Each non-PCIAP STA optionally includes a
local FSE
(shown in a dotted border) that, when included in the non-PC/AP STA, is
logically located at
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the MAC sublayer of the non-PC/AP STA, and maintains a local frame scheduling
table for
the non-PC/AP STA. Each non-PC/AP STA includes a conventional station
management
entity (SME), which is separate from the local QME. The SME of the non-PC/AP
STA
interfaces with a conventional MLME and a conventional PLME. The MLME
interfaces
with the MAC sublayer, whereas the PLME interfaces with a physical layer. The
physical
layer comprises a conventional physical layer convergence protocol (PLCP)
sublayer and a
conventional physical medium dependent (PMD) sublayer.
End-to-end QoS signaling messages of a session or an application
(sessionlapplication) are generated by the QSEs of STAB in a BSS of a WLAN
and/or from
outside the BSS. The end-to-end QoS signaling messages may indicate whether a
session/application is being set up, modified, or torn down. The ACE of the
PC/AP STA,
which may include a module for resource control and a module for policy
control (not
separately shown in Figure 1 ), exchanges end-to-end QoS signaling messages
with the QSEs
in the BSS and/or other QoS signaling counterparts outside the BSS that are
transparent to
the lower layers. Based on the end-to-end QoS signaling messages and local
policy, the ACE
makes an admission control decision for a session/application that is being
set up.
When a session/application is admitfed, the resource reserved for the
admission will
be reflected in the ACE, whereas the QME of the PC/AP STA establishes virtual
streams
(VSs) for transporting the session/application traffic from a local LLC
sublayer entity to one
or more peer LLC entities. Established VSs become active V Ss and are
identified by virtual
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stream identifiers (VSIDs). The QME of the PC/AP STA further extracts a frame
classifiers) from the end-to-end QoS messages for each admitted
session/application, where
a frame classifier is a set of classification parameters that can be used for
identifying the QoS
parameter values associated with the frame. Exemplary classification
parameters include IP
S classification parameters, LLC classification parameters and IEEE1~02.1 P/Q
parameters.
The QME of the PC/AP STA passes to the FCE of the PC/AP STA the VSID and the
corresponding frame classifier that are defined for the down-stream traffic
(traffic from
PC/AP STA to non-PC/AP STA) of a newly admitted session/application. The FCE
adds the
V SID and classifier that are defined for the down-stream, up-stream (from non-
PC/AP STA
to PC/AP STA) and side-stream (from non-PC/AP STA to non-PC/AP STA) traffic to
the
classification table, which is a table of all active classifiers that are
paired with or contain
VSIDs arranged in a defined order. The QME ofthe PC/AP STA also passes to the
FSE of
the PC/AP STA the VSID and the corresponding QoS parameter values. Logically,
the FSE
maintains the VSIDs and associated QoS parameter values, plus other
information, such as
data size, in a scheduling table.
Further, the QME of the PC/AP STA causes the PC/AP STA to send a management
frame, referred to as a VS Update frame, to each non-PCIAP STA participating
in a newly
admitted sessionlapplication. The V S Update management frame contains
information, such
as VS1Z7, frame classifier, VS Action (i.e., Add VS) and QoS parameter values,
that defines
the down-stream, up-stream' or side-stream traffic of the session/application.
After a non-
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PC/AP STA receives the information contained in a VS Update management frame
and
passes the information to its local QME, the local QME relays to the local FCE
of the non-
PC/AP STA the VSID and classifier, and to the local FSE (if any) of the non-
PC/AP STA the
VSID and QoS parameter values, for the up-stream or side-stream traffic.
An FCE, whether located within the PC/AP STA or a non-PC/AP STA, classifies
frames passed down to the LLC sublayer to a VSID. The FSE of the PC/AP STA
schedules
transmission opportunities (TOs) for frames classified to specific VSIDs based
on the QoS
parameter values associated with the VSIDs. The FSE of a non-PC/AP STA chooses
data
frames from its active VSs based on the QoS parameter values of those
particular VSs for
transmission over the TOs scheduled by the PC/AP STA.
When the QME of the PC/AP STA detects from end-to-end QoS signaling messages
received by the ACE a change of QoS parameter values for an admitted
session/application,
the ACE makes a new admission control decision regarding the "changed" QoS
parameter
values. When the change cannot be accepted, the QME takes no action for the
PC/AP STA
and the non-PC/AP STAs participating in the session/application. When the
change is
accepted, the resource reserved for the modified QoS parameter values will be
reflected in
the ACE, and the QME updates the FSE of the PC/AP STA with the new QoS
parameter
values using the admitted VSIDs for the session/application. The QME further
causes the
PC/AP STA to send another VS Update management frame to each non-PC/AP STA
participating in the modified session/application. The VS Update frame
contains information
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relating to the admitted VSID, the VS Action (i.e., Modify VS), and the new
QoS parameter
values. After a participating non-PC/AP STA receives a second type of VS
Update frame,
and the non-PC/AP STA passes the information contained therein to its local
QME. The
local QME updates the local FSE (if any) of the non-PC/AP STA with the VSID
and the
modified QoS parameter values for the up-stream or side-stream traffic of the
session/application. Subsequently, the FSEs of both the PC/AP STA and the non-
PC/AP
STA (if any) schedule VS transmissions based on the modified QoS parameter
values.
When the QME of the PC/AP STA detects from end-to-end QoS signaling messages
received by the ACE a termination of an admitted sessionlapplication, the
resource released
by the termination will be reflected in the ACE, whereas the QME identifies
the particular
VSIDs established for the session/application. The QME of the PCIAP STA
instructs the
FCE of the PC/AP STA to remove from the classification table the VSID and the
corresponding frame classifier associated with the down-stream traffic of the
session/application. The QME of the PC/AP STA also instructs the FSE of the
PC/AP STA
to remove from the scheduling table the VSIDs and the corresponding QoS
parameter values
associated with the session/application. Further, the QME of the PC/AP STA
causes the
PC/AP STA to send another VS Update management frame to each non-PCIAP STA
participating in the session/application. The VS Update management frame now
contains
information relating to VSID and a VS Action (i_e., Delete VS) that defines
the down-stream,
up-stream, or side-stream traffic of the session/application. After a non-
PC/AP STA receives
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the information contained in the VS Update management frame and passes the
information to
its local QME, the local QME instructs the local FCE of the non-PC/AP STA to
remove from
the local classification table the entry containing the VSID admitted for the
up-stream or
side-stream traffic of the session/application. The QME also instructs the FSE
(if any) of the
S non-PC/AP STA to remove from the local scheduling table the entry containing
the VSID.
The present invention also allows a non-PC/AP STA to send a VS Update
management frame to the PCIAP STA for requesting a setup, modification or
termination of
a session/application, while keeping admission/policy control and central
scheduling at the
PC/AP STA. The local QME of the non-PC/AP STA causes the transmission of such
a VS
Update frame, which does not contain a VSID, or contains a special VS117, in
the case of
setup request. The PC/AP STA receives the VS Update management frame and
passes the
information contained therein to the QME of the PC/AP STA. The ACE takes
appropriate
action based on the information contained in the VS Update management frame,
whereas the
QME of the PC/AP STA causes the PC/AP STA to send a VS Update management frame
back to the non-PC/AP STA. When the request is granted, the return VS Update
management frame contains the same information as the VS Update management
frame
originated by the PC/AP STA as if the request were initiated by the PC/AP STA
itself.
When the request is rejected, the return VS Update management frame contains
the
information that the VSID indicated in the original request, in addition to a
VS Action (i.e.,
Rej ect V S). The ability that a non-STA can initiate such a request is
especially useful when
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end-to-end QoS messages and session/application traffic go to or come from a
non-PC/AP
STA through a portal or a bridge, but not through the PC/AP STA.
The present invention also provides an in-band QoS signaling reference model
that
can be incorporated into the architectural reference model of the present
invention for
enabling a WLAN to support conventional network in-band QoS signaling
protocols, such as
IETF Diffserv and IEEE 802.1P/Q. Such in-band signaling provides QoS support
through
layer 3 (as in IETF Diffserv) or Iayer 2 (as in IEEE 802.1 P/Q)
tagging.mechanisms.
Generally, tagging does not reserve network resources in advance, and is
effected through
standardized combination patterns of certain bits in a data packet or frame.
These
combination patterns identify a reduced set of QoS parameters such as flow
type and priority
level associated with the data traffic.
Figure 2 shows an in-band QoS signaling reference model for QoS support over a
WLAN according to the present invention. More specifically, Figures 2 shows a
STA that
includes a QME, an FCE that is logically located in the LLC sublayer of the
STA and an FSE
that is logically located in the MAC sublayer of the STA. The FSE may be
optional in a non-
PC/AP STA. The QME interfaces with the FCE and the FSE, when present.
End-to-end QoS values expected by a new in-band QoS signaling session,
together
with the corresponding frame classifier, are extracted directly from a data
frame of the new
session., In particular, when the FCE of a STA finds a data frame-the first
data frame-of a
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new session that cannot be classified using the current classification table,
the FCE passes the
frame to the QME of the STA.
In the case of a PC/AP-STA, as applicable to down-stream traffic (traffic from
a
PC/AP STA to a non-PC/AP STA), the QME examines the frame for obtaining the
QoS
S parameter values and classifier characterizing the new down-stream session.
The QME also
establishes a virtual down-stream (VDS) for transporting the session traffic
from the local
LLC sublayer entity to one or more peer LLC entities, and assigns a VSID to
the newly-
established VDS. The QME then passes to the FCE the VSID and the corresponding
frame
classifier defined for the new down-stream session. The FCE adds the VS1D and
classifier to
its classification table. The QME also passes to the FSE such VSID and the
corresponding
QoS parameter values. Logically, the FSE maintains the VSID and associated QoS
parameter values, plus other information such as data size, in an entry of its
scheduling table.
Further, the QME of the PC/AP STA causes the PC/AP STA to send a management
frame,
such as a VS Update management frame, to each non-PC/AP STA participating in
the new
session in the BSS of the PC/AP STA. The VS Update management contains
information,
such as VS)D, VS Action (i.e., Add VDS), that defines the down-stream session.
In the case of a non-PC/AP-STA, as applicable to up-stream and side-stream
traffic
(tragic from a non-PC/AP STA to a PC/AP STA or a non-PC/AP STA), the QME
examines
the frame for obtaining the QoS parameter values and classifier characterizing
the new up-
stream or side-stream session. The QME of the non-PC/AP STA then causes the
non-PC/AP
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STA to send a management frame, such as a VS Update management frame, to the
PC/AP
STA of the BSS containing the non-PC/AP STA. The VS Update management frame
contains information, such as special VSID, VS Action (i.e., Add VUS or VSS),
frame
classifier, and QoS parameter values, that defines the up-stream or side-
stream session. After
S the PC/AP STA receives the information contained in the VS Update management
frame and
passes the information to the QME of the PC/AP STA, the QME establishes a
virtual up-
stream (VLTS) or a virtual side-stream (VSS) for transporting the session
tragic between LLC
entities, and assigns a VSID to the established VUS or VDS. The QME then
passes to the
FSE of the PC/AP STA the VSID and the corresponding QoS parameter values.
Further, the
QME of the PC/AP STA causes the PC/AP STA to return a management frame, such
as a VS
Update management frame, to the non-PC/AP STA starting the new up-stream or
side-
stream session in the BSS. The VS Update management contains information, such
as
assigned VSID, VS Action (i.e., Add VUS or VSS), frame classifier, and QoS
parameter
values, that defines the up-stream or side-stream session. After the non-PC/AP
STA receives
the information contained in the VS Update management frame from the PC/AP STA
and
passes the information to the local QME of the non-PC/AP STA, the QME relays
to the local
FCE of the non-PC/AP STA the VSID and classifier; and to the local FSE (if
present) of the
non-PC/AP STA the VSID and QoS parameter values, defined for the up-stream or
side-
stream session.
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The FCE shown in Figure 2 classifies frames passed down to the LLC sublayer to
a
VSID using its classification table. The FSE of the PC/AP STA schedules
transmission
opportunities (TOs) for frames classified to specific VSIDs based on the QoS
parameter
values associated with the VSIDs. The FSE of a non-PCIAP STA chooses data
frames from
its active VSs based on the QoS parameter values of those VSs for transmission
over the TOs
scheduled by the PC/AP STA.
Besides the classification function, the FCE also maintains a timer for each
entry of
its classification table for detecting termination of a session. When a data
frame is classified
successfully using a specific entry, the FCE resets the corresponding timer to
a predetermined
value. When the timer expires before the entry is used for classifying another
data frame, the
FCE passes that particular entry to the QME of the same STA and then deletes
the entry from
its classification table. The QME obtains the VSID contained in the entry, and
instructs the
local FCE of the same STA to remove the VSID together with the corresponding
QoS
parameter values from the scheduling table. In the case when the timeout event
occurs at the
PC/AP STA, as applicable to a down-stream session, the QME of the PC/AP STA
further
causes the PC/AP STA to send a VS Update management frame to each non-PC/AP
STA
participating in the session in the BSS. The VS Update management frame
contains
information such as VSID and VS Action (i.e., Delete VDS) that defines the
down-stream
session. After an addressed non-PC/AP STA receives the information contained
in the VS
Update management frame and passes the information to its local QME, the local
QNfE
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causes the non-PC/AP STA to remove any information related to this VDS. In the
situation
when the timeout event occurs at a non-PC/AP STA, as applicable to an up-
stream or side-
stream session, the QME of the non-PC/AP STA further causes the non-PC/AP STA
to send
a VS Update management frame to the PC/AP STA. The VS Update management frame
contains information such as VSID and VS Action (i.e., Delete VUS or VSS) that
defines the
up-stream or side-stream session. After the PC/AP STA receives the information
in the VS
Update management frame from the non-PC/AP STA and passes the to the QME of
the
PC/AP STA, the QME instructs the FSE of the PC/AP STA to remove from the
scheduling
table the entry containing the VSID.
The present invention also provides virtual streams (VSs) over a QoS-driven
WLAN
that can be set up by the QME of a PC in a BSS of a WLAN for transporting,
under defined
QoS constraints, the traffic of an admitted session/application from a local
LLC entity to one
or more peer LLC entities in the same BSS. VSs are torn down by the QME of the
PC/AP
STA when the underlying session or application is terminated.
Logically, a VS is a unidirectional path between a STA sourcing the VS and one
or
more other STAs receiving the VS in the BSS. A VS amounts to an identifiable,
ordered
sequence of data frames for transport within a BSS using a specified set of
QoS parameter
values. A V S identifier (V SID) is assigned by the QME of a PC/AP STA for
identifying the
VS upon the setup of the VS. A VS1D is local to, and unique within, a given
BSS. A VS is
defined by a triple of VSID, VS source station address, VS destination station
address, and is
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characterized by a set of QoS parameter values. A VS has no predefined
relationship to
higher-layer concepts, such as stream, flow, connection or session. A VS
exists solely within
a BSS, or more precisely, within the MAC sublayer of a WLAN. An appropriate
VSID is
inserted into each QoS data frame passed down to the LLC sublayer for
transmission via a
FCE, which is logically located in the LLC sublayer, and removed upon
reception at the
receiver LLC sublayer before the frame is passed up to the higher layer. Each
VSID is
associated by the QME of the PC/AP STA with a set of QoS parameter values for
the
scheduling of frame transmission by an FSE logically located in the MAC
sublayer.
Figure 3 shows a diagram of different types of virtual streams for QoS support
over a
WLAN according to the present invention. A VS can be a unitcast VS or a
multicast VS. A
unitcast VS is used for transporting data frames from one STA to another STA
within the
same BSS, while a multicast VS is used for transporting data frames from one
STA to
multiple STAB within the same BSS. A VS can further be a virtual down-stream
(VDS), a
virtual up-stream (VUS), or a virtual side-stream (VSS). A VDS is used for
transporting data
from the PC/AP STA in a BSS to one or more non-PC/AP STAB in the same BSS. A
WS is
used for transporting data from a non-PC/AP STA in a BSS to the PC/AP STA in
the same
BSS. A VSS is used for transporting data from a non-PC/AP STA in a BSS to at
least
another non-PC/AP STA in the same BSS.
The QoS parameter values associated with each VSID, that is, the QoS parameter
values expected by the session/application traffic to be served by the VS, may
be changed in
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the course ofthe session/application, as signaled by end-to-end QoS messages
and approved
by the QME of the PC/AP STA. V Ss are allocated bandwidth by the FSE ofthe
PC/AP STA
in terms of transmission opportunities (TOs) in accordance with the associated
QoS
parameter values for transporting data frames classified to the VSs.
A QoS parameter set may be defined by parameters, such as acknowledgment
policy,
flow type (continuous/periodic or discontinuouslbursty), priority level,
privacy information,
delay bound, fitter bound, minimum data rate, mean data rate, maximum data
burst, with the
latter two parameters further relating to the token replenishment rate and
bucket size of a
token bucket often used in describing or shaping incoming tragic. A STA may
support
multiple VSs with different sets of QoS values. In response to a TO, a non-
PC/AP STA may
transmit data from different VSs that the non-PC/AP station sources other than
the VS
specifically assigned bandwidth, as seen fit by its Iocal FSE based on the QoS
values of the
active VSs sourced by the STA.
The present invention also provides a technique for implementing admission
control
over a QoS-driven WLAN that does macro bandwidth management for QoS traffic
transport
over the MAC subIayer on a session-by-session basis. According to this aspect
of the
invention, admission control is performed by an ACE that is logically part of
a QME of a
PC/AP STA. The QME in tum interfaces with an FCE that is logically located in
the LLC
sublayer of the PC/AP STA and an FSE that is logically located in the MAC
sublayer of the
PC/AP STA.
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Admission control is based on new bandwidth request and current bandwidth
availability and accounts for the MAC and PHY overheads. Bandwidth is
partitioned into
two spaces, one space for sessions/applications of a continuous/periodic flow
type and the
space for sessions/applications of a discontinuous/bursty flow. In general,
the
continuous/periodic flow type is time sensitive and requires real-time
service, while the
discontinuous/bursty flow type is time tolerant and has a relatively lower
priority. The FSE
of the PC/AP STA of a given BSS provides feedback for every superfi~me through
a channel
status service primitive to the ACE, similar to a DSBM used with the RSVP QoS
protocol,
providing information with respect to the current contention-free period
(CFP), such as the
useable bandwidth and the used bandwidth, respectively, for both the
continuous and
discontinuous flow types of traffic.
When a new bandwidth request is received for a session/application of a
continuous
flow type, the request will be granted only when there is adequate bandwidth
still unused so
that admission of the new session/application will meet its QoS requirement
and while not
1 S degrading the performance of already admitted sessions/applications. When
the unused
bandwidth is not sufficient for supporting the new session/application, but
adequate
bandwidth that is being used for the discontinuous flow type can be preempted
for serving
the new session/application, then the new request can also be granted with the
consequence
of degrading some or all existing sessions/applications of a discontinuous
flow type. When a
new bandwidth request is received for a session/application of a discontinuous
flow type, the
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request will be granted provided that the sum of the unused bandwidth plus the
used
bandwidth for a discontinuous flow type having a lower priority level than the
priority level
of the new session/application is sufficient for honoring the new request.
In any case, bandwidth reservation may be based on the bursty characteristics
of the
traffic concerned, as quantified by the token rate and bucket size of the
token bucket
mechanism, or on the mean data rates using only the taken rate of the token
bucket. For
example, suppose that the effective channel rate (accounting for the MAC and
PHY
overheads) is C; that the time duration of each superFrame, which comprises of
a CFP and a
contention period (CP) as defined by IEEE P802.11/1999, is T; that the mean
data rate of a
session is represented by the token rate R; and the maximum data burst of a
session is given
by the bucket size B. The bandwidth requirement in terms of the channel time
per CFP for
such a session will be (R*T + B)/C for traffic burstiness based admission, and
R*T/C for
mean rate based admission, assuming appropriate units for C, T, R and B.
Figure 4 shows a flow diagram 400 for an admission control technique that can
be
1 S used for QoS support in a WLAN according to the present invention. At step
401, the type of
tragic flow is determined in response to a request for bandwidth for a new
sessionlapplication. If, at step 401, the traffic type is a continuous flow
traffic type, flow
continues to step 402 where it is determined whether there is sufficient
unused bandwidth
available for allocating to the requesting session/application. If, at step
402, there is
sufficient unused bandwidth, flow continues to step 403 where the request is
granted.
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If, at step 402, there is not sufficient unused bandwidth available for
allocating to the
requesting session/application, flow continues to step 404 where it is
determined whether
there is sufficient bandwidth being used by existing discontinuous flow type
sessions/applications that can be preempted. If, at step 404, there is
insufficient bandwidth
that can be preempted from existing discontinuous flow type
sessions/applications, flow
continues to step 405 where the request is rejected. If, at step 404, there is
sufficient
bandwidth that can be preempted from discontinuous flow type
sessions/applications, flow
continues to step 406 where some or all of the existing sessions/applications
of a
discontinuous flow type are degraded. Flow continues to step 407 where the
request is
granted.
If, at step 401, the requesting session/application is of a discontinuous
traffic flow
type, process flow continues to step 408 where it is determined whether the
sum of the
unused bandwidth plus the bandwidth for a discontinuous flow type having a
lower priority
than the priority of the requesting session/application is sufficient. If, at
step 408, there is not
sufficient bandwidth for the requesting session/application, flow continues to
step 409 where
the request is rejected If, at step 408, there is sufficient bandwidth for the
requesting
session/application, flow continues to step 410 where the request is granted.
The present invention also provides a technique for implementing frame
classification
over a QoS-driven WLAN that enables the QoS information to pass from higher
layers
(above link layer) to lower layers (LLC and MAC sublayers) once per session or
per session
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change. According to this aspect of the present invention, frame
classification is performed
by a frame classification entity (FCE) that is logically located in the LLC
sublayer of a
station. After a frame has been classified, frame scheduling of the classified
frame is
performed by a frame scheduling entity (FSE) that is logically located in the
MAC sublayer.
Both the FCE and the FSE are interfaced to a QoS management entity (QME) that
contains
an ACE or a QoS signaling entity (QSE).
Frame classification fords appropriate virtual stream identifiers (VSIDs) to
label
frames passed down to the LLC sublayer by examining frames against classifiers
in a
classification table. The VSIDs are linked by the QME to specific sets of QoS
parameter
values for use by the FSE to schedule the transfer of frames between LLC
entities. Via a
QME or a VS UPDATE management frame, VSIDs are established to correspond with
classifiers and sets of QoS parameter values for an admitted
sessionlapplication. Priorto the
start of the session/application, paired V SIDs and classifiers are provided
to the classification
table of the FCE, while paired VSIDs and sets of QoS parameter values are
provided to the
scheduling table of the FSE.
Classifier entries are placed in the classification table in the order of
descending
search priority values. A classifier entry in the classification table is
comprised of a VSID, a
search priority, and classifier parameters. The classifier parameters may be
IP classifier
parameters, LLC classifier parameters, or IEEE X02.1 P/Q parameters. The IP
classifier
parameters are parameters such as IP TOS R.ange/Mask, IP Protocol, IP Source
CA 02415428 2003-O1-08
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Address/Mask, IP Destination Address/Mask, TCP/UDP Source Port Start, TCP/IJDP
Source
Port End, TCPlIIDP Destination Port Start, and TCP/UCP Destination Port End.
The LLC
classifier parameters are parameters such as Source MAC Address, Destination
MAC
Address, and EthertypelSAP. The IEEE 802.1 P/Q parameters are such parameters
as 802.1 P
Priority Range and 802.1 Q VLAN ID. When a frame is classified successfully in
the order of
descending search priorities using one or more of the classifier parameters
contained in an
entry, the V SID value contained in the first matched entry provides the VSID
to designate the
QoS parameter set for the resulting MAC service primitive used for passing the
classified
frame to the MAC sublayer, or otherwise the frame is indicated as a best-
effort
(asynchronous) frame.
Figure 5 depicts a process for classifying a frame that can be used in a QoS-
driven
WLAN according to the present invention. A frame 501 that has been passed down
to the
LLC sublayer of a station, from a higher layer in the station is received by
the QME of the
station. The QME examines the frame for information included in the received
fi~ame that is
included in at least one of the classifier parameters in at least one of the
classifier entries in a
classification table 502. The QME examines the entries in the classification
table in the
order of descending search priorities when classifying the received frame. The
VSID value
contained in the first matched entry is used for identifying the VS 503 and
the corresponding
QoS parameter set for transporting the data frame between peer LLC entities of
the BSS.
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The present invention also provides a technique for implementing frame
scheduling
over a QoS-driven WLAN that does micro bandwidth management for QoS trafFc
transport
over the MAC sublayer in all directions of a given basic service set (BSS) on
a superframe-
by-superframe basis. According to this aspect of the invention, frame
scheduling is
performed by a frame scheduling entity (FSE) that is logically located in the
MAC sublayer
of a PC/AP, which can be possibly assisted by a FSE of a non-PC station, in
the BSS. Frame
scheduling is based on the classification results, as expressed in a virtual
stream identifier
(VSID) for a QoS frame or in a best-effort priority value for a non-QoS frame,
of an FCE that
is logically located in the LLC sublayer of the PC/AP or a station associated
with the PC.
Frame scheduling is thus guided by the QoS parameter values associated by the
QME of the
PC/AP with each classified VS117, the QoS parameter values being null for a
best-effort
priority value.
Frame scheduling schedules transfer during the contention-free period (CFP),
between peer LLC entities, of frames passed down to the MAC sublayer of all
the stations,
including that the LLC entity within a PC/AP, in the BSS. A virtual central
queue or
scheduling table is formed at the PC/AP so that a QoS queuing or scheduling
algorithm can
be adapted for scheduling the service (i.e., transfer) of the frames queued in
actuality or by
prediction at the PC/AP or non-PC stations associated with the PC/AP. Figure 6
shows an
exemplary scheduling table that can be used for frame scheduling over a QoS-
driven WLAN
according to the present invention. The table includes entries for queuing the
traffic of
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admitted down-stream sessions (i.e., traffic to be transmitted from the PC/AP)
and the traffic
of admitted up-stream and side-stream sessions (i.e., traffic to be
transmitted from non-PC
stations) in the BSS.
An entry for the PC/AP is always present for the transfer of the tragic from
the
PC/AP to non-PC stations associated with the PCIAP. An entry for each non-PC
station in
the BSS is automatically created when the non-PG station is associated with
the PC/AP for
serving the best-effort traffic from that station. An entry is also created
for each VS when the
VS is set up by the QME of the PG/AP for transporting the traffic of a newly-
admitted
session. When a VS is torn down by the QME because the session is terminated,
the entry
corresponding to the torn-down VS is removed from the frame scheduling table.
For QoS
traffic, each entry includes the VSID and QoS parameter values supporting the
session, as
well as a size for the data on the corresponding VS. QoS entries in the table
may be ordered
in descending priority levels associated with the VSIDs corresponding to the
entries.
For a virtual down-stream (VDS) (or for the PG/AP); the size value of an entry
is
updated when the size on the VDS (or for the best-effort down-stream traffic
from the PC)
waiting for transmission is changed. For a virtual up-stream (VLTS) or a
virtual side-stream
(V S S) of continuouslperiodic flow type, as indicated in the corresponding
QoS parameter set,
the size value of the entry is derived from the appropriate QoS values for the
VUS or VSS,
such as mean data rate and maximum data burst as defined by the token bucket
mechanism.
The size value of an entry may be changed to reflect the real size as
piggybacked bythe
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transmitting station in a frame. For a VUS or a VSS of discontinuous/bursty
flow type (or
for the best-effort traffic of a non-PC station), the size value of the entry
is provided and
updated by the sending station through either a reservation request or a
piggybacking. For
traffic policing or for congestion control, the maximum data size transmitted
from a VS over
a certain time interval, such as a superframe time, T may be restricted by the
token bucket
mechanism to R*T + B, assuming appropriate units for R, T and B, where R and B
are the
token rate and bucket size of the token bucket.
With a central scheduling table, the FSE of the PC/AP can schedule
transmission
opportunities (TOs) in the CFP for queued traffic based on the data size in
each entry and
based on other QoS parameter values stored in each entry, such as priority
level, delay bound,
and fitter bound. A TO is defined by a nominal start time and a maximum
duration time. A
non-PC station may also form a local scheduling table pertaining to traffic
that is to be
transmitted from the station, so that the local FSE of the non-PC station can
choose data from
appropriate VUSs or VSSs under it for transmission in response to a given TO.
When
allocating TOs for queued traffic, the FSE of the PC/AP will also consider a
allocation of
centralized contention opportunities (CCOs) used in centralized contention by
non-PC
stations in the BSS for sending a reservation request when a new burst of
frames arrives in an
empty buffer at the station. Such consideration is based on a centralized
contention
algorithm.
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The present invention also provides RSVP/SBM-based down-stream session setup,
modification and teardown over a QoS-driven WLAN and the corresponding service
interfaces. A down-stream session is defined herein to be a data flow,
supported by a
particular transport-layer protocol, originating from a user outside a given
BSS of a wireless
LAN, passed through a PC/AP of the BSS, and destined to one or more stations
within the
BSS. Figure 7 shows a signal path diagram for RSVP/SBM-based down-stream
session
setup, modification, and teardown over a QoS-driven WLAN according to the
present
invention.
A user outside a BSS initiates a down-stream session by having its RSVP agent
send
out Path messages of the RSVP signaling protocol. The Path messages are
propagated to a
designated subnet bandwidth manager (DSBM) located in the PC/AP of the BSS.
The
DSBM in turn sends Path messages to the subnet bandwidth manager (SBM) of each
station
to receive the session inside the BSS. After the SBM of a destination station
receives the
messages, the SBM of the destination station begins resource reservation by
sending Resv
messages of the RSVP signaling protocol back to the DSBM. The DSBM then
performs
admission control with respect to the down-stream traffic transfer in the BSS
of the down-
stream session. The DSBM further sends appropriate Resv messages back to the
session
sender based on the outcome of its admission decision. Path messages and Resv
messages
for a given session are sent periodically by the session sender and
receiver(s), and may be
changed in the course of a session. The DSBM also responds to the change by
sending~out
CA 02415428 2003-O1-08
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appropriate Resv messages. Path messages and Resv messages are transparent to
the LLC
and MAC sublayers.
In particular, when the DSBM detects new Path/Resv messages of the RSVP
signaling protocol for a down-stream session to be set up, the DSBM extracts
the QoS
parameter values and the classifier from the messages. The DSBM then makes an
admission
decision on the session based on such factors as policy control and resource
control, with
resource availability information being provided periodically by the FSE of
the PC/AP,
which is logically of the MAC sublayer. When the session fails to pass the
admission
control, the DSBM rejects the session. When the session is admitted, the QME
ofthe PC/AP
sets up a new virtual down-stream (VDS) for transporting the down-stream
session traffic.
That is, the QME establishes a VSID for the VDS. The QME then instructs the
FCE to
create an entry for the VSID and classifier defining the session in the
classification table of
the FCE. The QME also instructs the FSE to create an entry for the VSID and
QoS
parameter values defining the session in the scheduling table of the FSE.
Further, the QME
instructs the MAC sublayer management entity (MLME) to issue a management
frame, V S
Update, for transmission to each of the stations to receive the session in the
same BSS. The
VS Update frame in this situation contains information such as VSID and VS
Action (Add
VDS) for the down-stream session.
When the DSBM detects a change of an admitted down-stream session from the
Path/Resv messages of the RSVP signaling protocol for the session, the DSBM
extracts the
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new QoS values defining the session from the messages, and decides whether to
honor the
modified QoS request. When the modification cannot be accepted, the session
remains
active under the previous QoS values. When the modification is accepted, the
QME of the
PC/AP modifies the VDS serving the session to reflect the changed QoS values
associated
S with the VDS. That is, the QME instructs the FSE to update the scheduling
table with the
new QoS values for the entry created for the session as identified by the
established VSID.
When the DSBM detects a termination of an admitted down-stream session from
either the Path/Resv messages of the RSVP protocol or a timeout indication for
the session,
the QME of the PC/AP tears down the VDS established for the
session/application. That is,
the QME matches the classifier defining the session/application to the VS>D
for the VDS.
The QME then instructs the FCE to delete the entry for the VSID and classifier
defining the
~sessionlapplication from the classification table. The QME also instructs the
FSE to delete
the entry of the VSID and QoS values defining the session/application from the
scheduling
table. Further, the QME instructs the MLME to send another VS Update frame to
each
station receiving the session/application in the same BSS. The VS Update
contains
information such as VSID and VS Action (i.e., Delete VDS) for the session.
The present invention also provides an RSVP/SBM-based up-stream session setup,
modification and teardown over a QoS-driven WLAN and the corresponding service
interfaces. An up-stream session is defined herein to be a data flow,
supported by a
particular transport-layer protocol, that originates from a station inside a
given BSS of a
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wireless LAN, passed through a PC/AP of the BSS, and destined to one or more
users
outside the BSS. Figure 8 shows a signal path diagram for an RSVP/SBM-based up-
stream
session setup, modification, and teardown over a QoS-driven WLAN according to
the
present invention.
A station inside a given BSS initiates an up-stream session by having its SBM
send
out Path messages of the RSVP signaling protocol. The Path messages are sent
to the DSBM
located in the PC/AP of the BSS. The DSBM in turn sends the Path messages to
the RSVP
agent of each user that is to receive the session outside the BSS. After a
destination RSVP
agent receives the messages, the destination RSVP agent begins resource
reservation by
sending Resv messages of the RSVP signaling protocol back to the DSBM. The
DSBM then
performs an admission control operation with respect to the up-stream traffic
transfer in the
BSS of the up-stream session on behalf of the SBM of the session sender. The
DSBM
further sends appropriate Resv messages back to the session sender based on
the outcome of
the admission decision. The Resv messages sent back to the session sender are
for
confirmation only, and do not require the recipient, i.e., the SBM of the
sending station, to
perform resource reservation for the up-stream traffic of the station, as
would be the case
with the conventional RSVP signaling protocol. Path messages and Resv messages
for a
given session are sent periodically by the session sender and receiver(s), and
may be changed
in the course of a session. The DSBM also responds to a change by sending out
appropriate
Resv messages, to which the recipient (again the SBM of the sending station)
will not take
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any resource reservation action in response. Path messages and Resv messages
are
transparent to the LLC and MAC sublayers.
In particular, when the DSBM detects new PathlResv messages of the RSVP
signaling protocol for an up-stream session to be set up, the DSBM extracts
the QoS
parameter values and the classif er from the messages, and makes an admission
decision on
the session based on factors such as policy control and resource control, with
resource
availability information being provided periodically by the FSE that is
logically located in the
MAC sublayer of the PC/AP. When the session fails to pass the admission
control, the
DSBM rejects the session. When the session is admitted, the QME of the PC/AP
sets up a
new virtual up-stream (VUS) for transporting the up-stream session traffic.
That is, the QME
establishes a virtual stream identifier (VSID) for the VUS. The QME then
instructs the FSE
of the PC/AP to create an entry for the V SID and QoS parameter values
defining the session
in the scheduling table of the FSE. Further, the QME instructs the MLME (MAC
sublayer
management entity) of the PC/AP to issue a management frame, VS Update, for
transmission
to the station initiating the session. The VS Update frame in this case
contains information
such as VSID, frame classifier, VS Action (i.e., Add VUS), and QoS parameter
values for the
up-stream session. Once the addressed station receives the VS Update frame,
its local QME
instructs the local FCE to create an entry for the VSID and frame classifier
defining the
session in the local classification table. The local QME also instructs the
local FSE to create
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an entry for the VSID and QoS parameter values defining the session in the
local scheduling
table.
When the DSBM detects a change of an admitted up-stream session from the
Path/Resv messages of the RSVP signaling protocol for the session, the DSBM
extracts the
new QoS parameter values defining the session from the messages, and
determines whether
to honor the modified QoS request. When the modif cation cannot be accepted,
the session
will remain active under the previous QoS parameter values. When the
modification is
accepted, the QME of the PC/AP modifies the VUS serving the session to reflect
the changed
QoS parameter values associated with the VUS. That is, the QME ofthe PC/AP
instructs the
FSE of the PC/AP to update the scheduling table with the new QoS parameter
values for the
entry created for the session, as identified by the established VS)D. The QME
further
instructs the MLME of the PC/AP to issue another VS Update frame to the
station initiating
the session. The VS Update frame in this situation contains information such
as VSID, VS
Action (i.e., Modify VUS), and new QoS parameter values for the session. Once
the station
initiating the session receives the VS Update frame, its local QME instructs
the local FSE to
update the entry of the VSTD defining the session in the local scheduling
table with the new
QoS parameter values.
When the DSBM detects a termination of an admitted up-stream session from
either
the Path/Resv messages of the RSVP protocol or a timeout indication for the
session, the
QME of the PC/AP tears down the VUS established for the session. That is, the
QME of the
CA 02415428 2003-O1-08
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PC/AP matches the classifier defining the session to the VSID forthe VUS. The
QME ofthe
PC/AP then instructs the FSE of the PC/AP to delete the entry of the VSID and
QoS
parameter values defining the session from the scheduling table. Further, the
QME instructs
the MLME of the PC/AP to send another VS Update frame to the station
initiating the
session. This particular VS Update contains.information such as VSID and VS
Action (i.e.,
Delete VUS) for the session. Once the station initiating the session receives
the VS Update
frame, its local QME instructs the local FCE to delete the entry of the VSID
and classifier
defining the session from the local classification table. The QME also
instructs the local FSE
to delete the entry of the VSID and QoS parameter values defining the session
from the local
scheduling table.
The present invention also provides RSVP/SBM-based side-stream session setup,
modification and teardown over a QoS-driven WLAN and the corresponding service
interfaces. A side-stream session is defined herein to be a data flow,
supported by a
particular transport-layer protocol, that originates from a station inside a
given BSS of a
wireless LAN and destined directly to one or more stations within the BSS. The
data flow
may also be destined to any user outside the BSS through a PC/AP of the BSS.
Figure 9
shows a signal path diagram for RSVP/SBM-based side-stream session setup,
modification,
and teardown over a QoS-driven WLAN according to the present invention.
A station inside a given BSS initiates a side-stream session by having its SBM
send
out Path messages of the RSVP signaling protocol. The Path messages are sent
to the DSBM
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located in the PC/AP of the BSS. The DSBM in turn sends Path messages to the
RSVP
agent of each user intended to receive the session outside the BSS, and to the
SBM of each
station intended to receive the session inside the BSS. After a destination
RSVP agent
receives the messages, the destination RSVP agent begins resource reservation
by sending
Resv messages of the RSVP signaling protocol back to the DSBM of the PClAP.
The SBM
of each destination station within the BSS also begins resource reservation by
sending its
own Resv messages back to the DSBM of the PC/AP. The DSBM of the PC/AP then
performs an admission control operation with respect to the side-stream
traffic transfer imthe
BSS of the side-stream session on behalf of the SBM of the session sender. The
DSBM
further sends appropriate Resv messages back to the session sender based on
the outcome of
the admission decision. The Resv messages are for confirmation only, and do
not require the
recipient, i.e., the SBM of the sending station, to perform resource
reservation for the side-
stream tragic of the station, as would be the case with the conventional RSVP
signaling
protocol. Path messages and Resv messages for a given session are sent
periodically by the
session sender and receiver(s), and may be changed in the course of a session.
The DSBM of
the PC/AP also responds to the change by sending out appropriate Resv
messages, to which
the recipient (again, the SBM of the sending station) will not take any
resource reservation
action in response. Path messages and Resv messages are transparent to the LLC
and MAC
sublayers.
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In particular, when the DSBM detects new Path/Resv messages of the RSVP
signaling protocol for a side-stream session to be set up, the DSBM extracts
the QoS
parameter values and the classifier from the messages, and makes an admission
decision on
the session based on factors such as policy control and resource control, with
resource
availability information being provided periodically by the FSE of the MAC
sublayer in the
PC/AP. When the session fails to pass the admission control, the DSBM rejects
the session.
When the session is admitted, the QME of the PC/AP sets up a new virtual side-
stream
(VSS) for transporting the side-stream session traffic. That is, the QME of
the PC/AP
establishes a virtual stream identifier (VSID) for the VSS. T'he QME then
instructs the FSE
of the PC/AP, which is logically part of the MAC sublayer, to create an entry
for the VSID
and QoS parameter values defining the session in the scheduling table of the
FSE. Further,
the QME instructs the MLME of the PC/AP to issue a management frame, VS
Update, for
transmission to the station initiating the session. The VS Update frame in
this situation
contains information such as VSID, frame classifier, VS Action (i.e., Add
VSS), and QoS
parameter values for the side-stream session. Once the station initiating the
session receives
the frame, its local QME instructs the local FCE to create an entry for the
VSID and frame
classifier defining the session in the local classification table. The local
QME also instructs
the local FSE to create an entry for the VSID and QoS parameter values
defining the session
in the local scheduling table. Additionally, the QME of the PC/AP instructs
the MLME of
the PCIAP to issue a management frame, VS Update, for transmission to each
station
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intended to receive the session in the same BSS. The VS Update frame in this
situation
contains information such as VSID and VS Action (i.e., Add VSS) for the side-
stream
session.
When the DSBM detects a change of an admitted side-stream session from the
Path/Resv messages of the RSVP signaling protocol for the session, the DSBM
extracts the
new QoS parameter values defining the session from the messages, and
determines whether
to honor the modified QoS request. When the modification cannot be accepted,
the session
will remain active under the previous QoS parameter values. When the
modification is
accepted, the QME of the PC/AP modifies the V S S serving the session to
reflect the changed
QoS parameter values associated with the VSS. That is, the QME ofthe PC/AP
instructs the
FSE of the PC/AP to update the scheduling table with the new QoS values for
the entry
created for the session, as identified by the established VSID. The QME of the
PC/AP
further instructs the MLME of the PC/AP to issue another VS Update frame to
the station
initiating the session. The VS Update frame in this situation contains
information such as
VS>D, VS Action (i.e., Modify VSS), and new QoS parameter values for the
session. Once
the addressed station receives the frame, its local QME instructs the local
FSE to update the
entry of the VSID defining the session in the local scheduling table with the
new QoS
parameter values.
When the DSBM detects a termination of an admitted side-stream session from
either
the Path/Resv messages of the RSVP protocol or a timeout indication for the
session,~the
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QME of the PC/AP tears down the VSS established for the session. That is, the
QME of the
PC/AP matches the classifier defining the session to the VSID for the VSS. The
QME of
the PC/AP then instructs the FSE of the PC/AP to delete the entry of the VSID
and QoS
parameter values defining the session from the scheduling table. Further, the
QME instructs
the MLME of the PC/AP to send another VS Update frame to the station
initiating the
session. In this situation, the VS Update frame contains information such as
VSID and VS
Action (i.e., Delete VSS) for the session. Once the addressed station receives
the VS Update
frame, its local QME instructs the local FCE to delete the entry of the VSID
and classifier
defining the session from the local classification table. The local QME also
instructs the
local FSE to delete the entry of the VS117 and QoS parameter values defining
the session
from the local scheduling table. Additionally, the QME of the PC/AP instructs
the MLME of
the PC/AP to send another VS Update frame to each station receiving the
session in the same
BSS. The VS Update frame contains information such as VSID and VS Action
(i.e., Delete
VSS) for the session. .
The present invention also provides enhanced channel access mechanisms over a
QoS-driven WLAN that greatly improve QoS capability and channel utilization on
a wireless
LAN over simple polling and distributed contention schemes as defined by IEEE
P802.11/1999. Channel access according to the present invention is driven by
QoS
parameter values that are associated with admitted sessions/applications.
Specifically, down-
stream traffic (from a PC/AP STA to at least one non-PC/AP STA) is given TOs
directly by
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the FSE of the PC/AP STA in a given BSS of a WLAN based on the corresponding
set of
QoS parameter values, such as delay bound and mean data rate for the down-
stream traffic.
Up-stream and side-stream traffic (from a non-PC/AP STA to the PCIAP STA or a
non-
PC/AP STA) of a continuous/periodic flow type is allocated TOs periodically by
the FSE of
the PC/AP STA also in accordance with the corresponding set of QoS parameter
values for
the up-stream and side-stream traffic. Up-stream and side-stream traffic of a
discontinuous/bursty flow type is allocated TOs only when there is data
buffered at non-
PC/AP stations for ~ transmission, with the allocation fiu~ther being subject
to the QoS
parameter values. Consequently, channel bandwidth is not idled away due to
inactive
stations, as would be the case when all the stations associated with the PC/AP
STA were
polled for data transmission, regardless of the respective flow type of their
traffic. QoS
based channel access according to the present invention also allows higher
priority traffic to
be transferred, an important mechanism, especially in the case of inadequate
bandwidth.
The channel access mechanisms of the present invention include a centralized
contention and reservation request scheme that is carried out under the
control of a point
coordination function (PCF) contained in the PC/AP STA, in addition to a
conventional
distributed contention scheme that is under the control of a conventional
distributed
coordination function (DCF) contained equally in every STA, as described in
IEEE
P802.11/1999. The channel access mechanisms of the present invention further
include a
multipoll scheme that announces multiple TOs in a single frame under the PCF,
in contrast to
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the simple poll scheme that announces one TO in one frame, as provided by IEEE
P802.11/1999.
According to this aspect of the invention, non-PC/AP stations use centralized
contention for sending a reservation request (RR) to the PC for channel
bandwidth allocation
when a non-PC/AP stations have a new burst of data frames to transmit (to the
PC/AP STA
or/and other stations). In each "contention-free period" (CFP) under the PCF,
zero, one or
multiple centralized contention intervals (CCIs) may be selected by the PC for
centralized
contention. The length of each CCI is expressed in units of centralized
contention
opportunities (CCOs), and is also determined by the PC. The number of
available CCIs and
the length of each CCI are announced by the PC/AP STA in a contention control
(CC) frame.
A station, if permitted to send an RR, sends an RR into any one of the
available CCOs
following a CC frame. Stations that successfully sent an RR frame in a given
CCI will be
identified in the next CC frame sent by the PC/AP STA. Such positive
indication may also
be effected in the form of a TO given to the transmission of the data burst
for which an RR
was sent. Stations that did not successfully send an RR frame in a given CCI
may retry in the
next CCI.
The phrase "contention-free period" loosely corresponds to a conventional
"contention period" (CP), as defined in IEEE P802.11/1999. In contrast to the
present
invention, CP refers to distributed contention as operating under the DCF of
IEEE
P802.11/1999, whereas CFP of the present invention implies no such contention,
but can
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have centralized contention under the PCF. Centralized contention enables a
PC, or an FSE
inside the PC/AP STA, to have complete control of channel bandwidth such that
the period
seized by non-PC/AP STAs for contention is determined by the PC in advance, as
opposed to
distributed contention by which STAB can seize the channel for an
unpredictable duration
and thereby may lock up channel access for other contending
sessions/applications. The
centralized contention of the present invention also allows the PC to optimize
the bandwidth
allocation for such contention so that channel throughput is increased while
access delay is
reduced, compared to distributed contention. This is. because the PC can
maintain a global
history of the contention outcome of all the stations, and thus can optimally
estimate the
bandwidth need for centralized contention and conflict resolution for previous
contention,
whereas a station using distributed contention contends based on the local
knowledge of its
own contention history and thus cannot optimize the overall contention
algorithm.
Moreover, with centralized contention, stations send only RRs of very short
length and only
once for a new burst, while with distributed contention stations send data
frames of much
larger length and may have to contend several times for each data burst
because a data burst
generally needs to be decomposed into a number of data frames that do not
exceed a
predefined size. Therefore, the present invention yields much less contention
intensity and,
hence, much higher channel throughput and lower access delay, than a
conventional
distributed contention technique.
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A multipoll is sent by the PC/AP STA for conveying a sequence of TOs to one or
more non-PC/AP stations for up-stream and/or side-stream transmission. A
multipoll also
specifies the length of each TO. This technique of the present invention is
particularly useful
when direct station-to-station communication is involved, thereby avoiding the
situation that
S data frames need to be sent to the PC/AP STA first and then back to the
destination non-
PC/AP STA(s).
Figure 10 is a diagram showing enhanced channel access mechanisms over a QoS-
driven WLAN according to the present invention. Figure 10 shows a superframe
having a
contention free period (CFP), a conventional contention period (CP) and
exemplary frames
illustrating the enhanced channel access mechanisms of the present invention.
A super&ame
is demarcated by a target beacon transmission time (TBTT). Subsequent to the
TBTT, a
PC/AP STA transmits a beacon frame, as defined by IEEE P802.11/1999. A short
inter-
frame space (SIFS) occurs after the transmission of each frame in the CFP,
also as defined by
IEEE P802.11/1999.
Next in Figure 10, a down-stream frame D2 is sent from a PC/AP STA to a non-
PC/AP STA. The down-stream frame includes a poll for the destination non-PC/AP
STA for
sending upstream traffic to the PC/AP STA. The polled non-PC/AP STA responds
with an
up-stream frame U2 that contains user or management data and an
acknowledgement to the
poll.
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An exemplary multipoll frame is shown next that conveys a sequence of TOs for
non-
PC STA(s) to send traffic. In this case, there is a sequence of four TOs that
are identified by
the multipoll. The first TO has been allocated to VS 13 or a different VS
sourced by a non-
PCJAP STA and is used for sending data frames classified to VS13. The second
TO has
been allocated to VS31 or a different VS sourced by a non-PC/AP STA and is
used for
sending data frames classified to VS31. The third TO has been allocated to a
non-PC/AP
STA and is used by the non-PC/AP STA to send a delayed acknowledgement (Dly-
Ack) that
acknowledges receipt of frames identified in the Dly-Ack frame by the non-
PC/AP STA at
some previous time. The fourth TO has been allocated toVS28 or a different VS
sourced by
a non-PC/AP STA and is used for sending data frames classified to VS28.
Traffic is sent
into each respective TO. Subsequent to the TOs, the PCIAP STA sends an
acknowledgement
frame with a poll. The acknowledgement frame acknowledges correct reception of
a frame
sent immediately before the acknowledgement frame by a non-PC/AP STA (i.e.,
the frame
from VS28 according to the illustration in Figure 10), and the poll polls a
destination non-
1 S PC/AP STA for sending upstream or sidestream traffic. The polled non-PC/AP
STA, STA 4,
responds by sending a data frame to STA 5 (S45).
The CFP then includes a CC frame identifying three CCOs that can be used by
non-
PC STAB having new bursts of traffic of a discontinuous/bursty flow type or of
a best
effort/asynchronous nature to transmit for sending an RR. The CC frame also
includes
information relating to the identification ofnon-PC/AP STAs that successfully
sent an RR in
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a preceding CCI to the PC/AP STA, so that these non-PC STAB can determine
whether an
RR needs to be re-sent in the next CCI. An RR is sent for having bandwidth
allocated for
transmitting the burst of traffic, as defined above, that arrives at a non-
PC/AP STA for
transmission. In the exemplary arrangement of Figure 10, a single RR is sent
into the first
CCO, no RR is sent into the second CCO, and two colliding RRs are sent into
the third CCO.
Following the CCOs, the PC/AP STA sends a down-stream frame D1 with a poll,
and the
polled non-PC/AP STA responds with an up-stream frame U1 in which an
acknowledgement
is included.
In the exemplary arrangement of the superframe shown in Figure 10, a second CC
frame is sent from the PC/AP STA indicating available CCOs and acknowledging
receipt of
a frame immediately prior to the transmission of the CC frame. As shown in
Figure 10, a RR
is sent into the first available CCO whereas another RR is sent into the
second available
CCO. In the illustration of Figure 10, these two RRs collided in the third CCO
of the
preceding CCI, but they are now sent without collision and each received
correctly by the
PC/AP STA, thereby successfully resolving a collision. Lastly, a contention
free (CF) end
frame is sent indicating the end of the CFP and the beginning of the
conventional CP in the
current superframe.
The present invention also provides a technique for implementing centralized
contention and reservation request over a QoS-driven WLAN that enables
stations of a given
BSS to report to a PC/AP of the BSS in an efficient way arrivals of new QoS or
best-effort
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traffic bursts awaiting transmission. The FSE of the PC/AP can then place such
information
in its scheduling table for allocating transmission opportunities (TOs) for
sending the data
bursts.
Centralized contention is controlled by the PC/AP, and occurs in the
"contention-free
S period" (CFP) of a superframe, as shown in Figure 11 a, in contrast to a
conventional
contention-period (CP) that is used for conventional distributed contention.
According to the
invention, centralized contention occurs in well defined centralized
contention intervals
(CCIs). Each CCI is always preceded by a contention control (CC) frame that is
broadcast by
the PC/AP (or by a CC frame containing an acknowledgment to the last data
frame received
by the PC). Each CCI contains a number of centralized contention opportunities
(CCOs) for
sending reservation request (RR) frames. Subject to certain centralized
contention rules,
stations send their respective RR frames using CCOs. There may be zero, one,
or more CCIs
in a given CFP, with the number of CCOs in each CCI selected, as seen fit by
the FSE in
consultation with the scheduling table maintained by the FSE of the PG/AP and
the
centralized contention algorithm in use. A centralized contention algorithm
determines the
desired length of the following CCI in units of CCOs, based on the contention
outcome (i.e.,
the number of idle, successful, and colliding CCOs) in the preceding CCI and
on the estimate
of the number of stations generating a new RR frame since the last CCI.
A CC frame, such as shown in Figure 11 b, contains information, such as a
priority
limit, a CCI length, a permission probability (PP), and feedback entries. The
priority limit
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specifies the minimum priority IeveI of a virtual up-stream or a virtual side-
stream having a
new data burst for transmission that has a privilege to trigger its sourcing
station to send an
RR frame on its behalf in the following CCI. A CCI length is expressed in
terms of the
CCOs contained in the CCI. A PP is used for reducing contention when the
available CCI
length is shorter than the optimum CCI length, and is calculated in such cases
by dividing the
available CCI length by the optimum CCI length. Otherwise, the PP is set to
unity. Stations
having an obligation and a privilege to send an RR frame first check against
the PP to test
whether they are permitted to contend for sending an RR frame. These
particular stations
independently generate a number from a random variable uniformly distributed
over the
interval (0,1). When a station generates a number smaller than the PP, the
station is
permitted to contend, and not otherwise. Permitted stations independently and
in a random
fashion select one of the available CCOs and send their RR frames using their
selected
CCOs. The feedback entries contain the VSlDs or AIDS for which an RR frame was
correctly received by the PCIAP during the last CCI. Stafions that find no
such positive
feedback during the CC frame will retry to send an RR frame during the next
CCI under the
centralized contention rules applied to that the next CCI, unless a station is
offered prior to
the start of the next CCI a transmission opportunity (TO) for the virtual
stream (VS),
resulting in the sending of the RR frame.
An RR frame, such as shown in Figure 11 c, primarily contains information,
such as a
~ data size of the V S for which the RR frame is being sent, and a VSID
identifying the VS, or a
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data size of the best-effort tragic and the AID of the sending station. A
station generates an
RR frame when a new burst of data is classified to one of its sourced VSs for
transmission.
A station may also send an RR frame using a TO allocated to the station. RR
frames are
generally much shorter than data frames, and hence considerably reduce
contention and
improve channel performance in comparison with cases where all data frames are
sent by
contention as under the conventional distributed contention function (DCF) of
IEEE
P802.11/1999.
The present invention provides a technique for implementing multipoll over a
QoS-
driven WLAN that allows for transmissions from a sequence of virtual up-
streams (VIlSs)
and virtual side-streams (VSSs) at one or more stations by a single poll.
According to the
invention, such a muItipoll scheme extends the conventional simple poll scheme
that allows
for transmission from only one station per poll, as defined by IEEE
P802.11/1999, thus
greatly improving bandwidth utilization efficiency of wireless medium. The
approach'of the
present invention is particularly useful when direct station-to-station
communication is
involved because data frames need not to be sent to a PC/AP first and then
back to the
destination station(s).
A multipoll is sent by a PC/AP during the CFP of a superframe when it is
desirable to
allocate a sequence of transmission opportunities (TOs) to various stations
for sequential up-
stream and/or side-stream data transmissions. A multipoll frame is primarily
formed based
on poll records arranged in the order of their occurrence, with each poll
record further
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comprised of a VSID (or AID, association ID) and a duration time. The VSID
identifies a
VUSNSS sourced by the station that is receiving a TO from a particular poll
record, or the
AID of the station in situations when the TO is for a station sourcing no
active VUSs/VSSs.
The duration time of a TO specifies the maximum length of the TO. The first TO
starts a
SIFS period after the multipoll frame ends, and each successive TO starts when
the preceding
TO limit expires. Alternatively, a TO starts a SIFS period after the station
using the
preceding TO sends a data frame that is indicated to be the final frame from
that station for
its poll record, when the station using the second-in-time TO detects such an
indication.
That is, when a station does not detect the transmission termination, as
indicated by the
preceding station, the station starts its transmission within TO allocated to
the station. When
a station detects such a termination before the preceding TO is fully
utilized, the station may
start early, but cannot use the leftover duration time in addition to the full
duration of TO
allocated to the station. In such a situation, the PCIAP does not take any
action to reclaim
the unused channel time. When some stations do not completely use their TOs
allocated in a
multipoll, the last station may end its transmission prior to the nominal
expiry time, and the
unused channel time is then returned to the PC/AP for reallocation.
A station, in response to a poll record containing a VSID, may transmit data
from the
indicated VUS/VSS or, alternatively, from a different one, as determined by
its local FSE
based on the QoS parameter values of the active VUSs/VSSs sourced by the
station. When a
poll record contains an AID, the station having the AID transmits data
completely based on
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the decision of its local FSE, again, in accordance with the QoS parameter
values of the
active VUSs/VSSs.
Figure 12a shows an exemplary arrangement of a superframe having a contention
free
period (CFP), a conventional contention period (CP) and an exemplary
arrangement of
frames. The superframe of Figure 12a is demarcated by a target beacon
transmission time
(TBTT). Subsequent to the TBTT, a PC/AP STA transmits a beacon frame, as
defined by
IEEE P802.11/1999. A short inter-frame space (SIFS) occurs after the
transmission of each
frame in the CFP, also as defined by IEEE P802.I1/1999.
Next in Figure 12a, a down-stream frame D2 is sent from a PC/AP STA to a non-
PC/AP STA. The down-stream frame includes a poll for the destination non-PC/AP
STA for
sending upstream traffic to the PC/AP STA. The polled non-PC/AP STA responds
with an
up-stream frame U2 that contains user or management data and an
acknowledgement to the
poll.
An exemplary multipoll frame is shown next that conveys a sequence of TOs for
non-
PC STA(s) to send traffic. In this case, there is a sequence of five TOs that
are identified by
the multipoll. The first TO has been allocated to VS 13 or a different VS
sourced by a non-
PC/AP STA and is used for sending data frames classified to VS13. The second
TO has
been allocated to VS31 or a different VS sourced by a non-PC/AP STA and is
used for
sending data frames classified to VS31. The third TO has been allocated to a
non-PC/AP
STA and is used by the non-PC/AP STA to send a delayed acknowledgement (Dly-
Ack) that
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acknowledges receipt of frames identified in the Dly-Ack frame by the non-
PC/AP STA at
some previous time. The fourth TO has been allocated toVS28 or a different VS
sourced by
a non-PC/AP STA and is used for sending data frames classified to VS28. The
fifth TO has
been allocated to VS4 or a different VS sourced by a non-PC/AP STA and is used
for
sending data frames classified to VS4. Traffic is sent into each respective
TO. Subsequent
to the TOs, the PCIAP STA sends an acknowledgement frame with a poll. The
acknowledgement frame acknowledges correct reception of a frame sent
immediately before
the acknowledgement frame by a non-PC/AP STA (i.e., the frame from STA 4
according to
the illustration in Figure 12a), and the poll polls a destination non-PC/AP
STA for sending
up-stream or side-stream traffic. The polled non-PC/AP STA, STA 4, responds by
sending a
data frame to STA 5 (S45). Lastly, a contention free (CF) end frame is sent
indicating the
end of the CFP and the beginning of the conventional CP in the current
superframe.
While the present invention has been described in connection with the
illustrated embodiments, it will be appreciated and understood that
modifications may be
1 S made without departing from the true spirit and scope of the invention.
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