United States Patent (19)
`Hulyalkar et al.
`
`54 METHOD AND APPARATUS FOR
`RESERVATION-BASED WIRELESS-ATM
`LOCAL AREA NETWORK
`(75) Inventors: Samir N. Hulyalkar, Columbia, Md.;
`Chiu Y. Ngo, Ossining, N.Y.
`73) Assignee: Philips Electronics North America
`Corporation, New York, N.Y.
`
`21 Appl. No.: 656,803
`22 Filed:
`Jun. 3, 1996
`(51) Int. Cl. ...................... H04B 7/212: HO4L 12/28:
`HO4L 12/56
`52 U.S. Cl. ......................... 370/348; 370/395
`58) Field of Search ..................................... 370/310,321,
`370/322,328,329, 330, 337, 338, 347,
`348,395,396, 397, 398, 399, 409, 468
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,046,066 9/1991 Messenger.
`5297,144 3/1994 Gilbert et al.
`5,471469 11/1995 Flammer et al. .
`5,570,355 10/1996 Daid et al. .............................. 370/395
`5,572,517 11/1996 Safadi .............
`... 375/257
`5,633,869 5/1997 Burnett et al. ..........
`... 370/396
`5,638,371
`6/1997 Raychaudhuri et al.
`... 370/.395
`5,648,958 7/1997 Counterman ............................ 370/.458
`FOREIGN PATENT DOCUMENTS
`0483546A1 6/1992 European Pat. Off. .
`OTHER PUBLICATIONS
`"Hiperlan: The High Performance Radio Local Area Net
`work Standard", by G.A. Halls, Elec. & Comm. Eng.
`Journal. Dec. 1994, pp. 289-296.
`ICC Conference Record vol. 2 of 3, Jun. 19-22 1983, pp.
`754-759.
`
`USOO5787080A
`Patent Number:
`11
`45) Date of Patent:
`
`5,787,080
`Jul. 28, 1998
`
`ICC77 Conference Record vol. 2 of 3. Jun. 12-15 1977, pp.
`22.1-105 . . . 22.1-111.
`“Wireless Trends in 21st Century”, by D. Petras et al. 1995
`Wireless Communication Systems Symposium, Nov.28 and
`29, 1995.
`“ATM Local Area Networks Using Distributed Switch
`Architecture". Y. Du et al. IEEE, 1994, pp. 1832-1837.
`"ATM-Based Transport Architecture for Multiservices
`Wireless Personal Communication Networks". D. Ray
`chaudhuri, IEEE Journal on Selected Areas in Communica
`tions, vol. 12, No. 8. Oct. 1994, pp. 1401-1414.
`
`Primary Examiner-Ajit Patel
`Attorney, Agent, or Firm-Steven R. Biren
`57)
`ABSTRACT
`A reservation-based wireless asynchronous transfer mode
`(ATM) local area network includes a system architecture of
`mobile nodes (MNs), each MN for communicating with
`various ones of the other MNs. A plurality of services is
`supported wherein each service has respective quality-of
`service (QoS) requirements. A medium access control
`(MAC) layer using a reservation-based communications
`protocol is provided, wherein the protocol divides all MAC
`based communications between a control channel and a data
`channel, the control channel and the data channel together
`making up a control-data superframe (CDS). The protocol
`further utilizes the control channel for allocating a band
`width of the data channel to each service. The control
`channel includes a control frame during which an allocation
`of data payload slots of the data channel is determined
`according to (a) a long-term strategy corresponding to a time
`of service required to complete a service over multiple CDS
`frames and (b) a short-term strategy within a CDS frame
`corresponding to instantaneous data payload slot require
`ments for a particular service. Respective QoS requirements
`of each service are thus achieved.
`
`26 Claims, 4 Drawing Sheets
`
`52
`WIREDATM:
`TERMINAL
`A934;.
`O293
`A23 SAL
`ATMLAYER
`WIREDMAC
`s WIRED PHY
`
`
`
`
`
`54
`12
`BASESTATION: MOBILEAM:
`RESOURCEMANAGEMENT
`TERMINAL
`AND MOBILITY SUPPORT
`AP240AN2
`G2931
`O2931.
`O 2 9 3
`ADDRESSMAPPING SAA
`ATMLAYER
`ATMLAYER a F.
`WIRELESSMAC
`WIRELESSMAC
`A
`WIRELESSPHY
`WIREESSPHY
`777-7,
`50
`
`WIRED
`MEDIUM
`
`WIRELESS
`MEDIUM
`
`

`

`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 1 of 4
`
`5,787,080
`
`KEY:
`--> WRELESS CONNECTION
`- WIRELINE CONNECTION
`X SWITCH (ATM)
`
`
`
`
`
`KEY.
`MOBILE SWITCHING CENTER
`BASE-STATION
`MOBILETERMINAL
`GATEWAY
`
`FIG.1(b)
`
`

`

`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 2 of 4
`
`5,787,080
`
`
`
`WIREDATM
`NETWORK
`
`KEY:
`--> WIRELESS CONNECTION
`- WIRELINE CONNECTION
`- x - SWITCH (ATM)
`
`KEY:
`MN MOBILENODE
`(g) FORWARDING MOBILENODE
`
`

`

`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 3 of 4
`
`5,787,080
`
`54
`12
`52
`MOREAM:
`BASESTATION
`: WREAM,
`EN:
`: EMN: RESOURCEMANAGEMEN
`: APEAge
`AND MOBILITYSUPPOR; : ABE;
`:
`O2931 :
`0293
`O2931:
`: A2 SA: ; SAADDRESSMAPPING SAAL: :
`ATMLAYER::ATMLAYERz:
`WIRED MAC ?
`WIRELESSMAC
`WIRED PHY Af WIRELESSPHY
`
`
`
`
`
`WRED
`
`50
`
`WIRELESS
`MEDIUM
`
`
`
`
`
`
`
`RESOURCE MANAGEMENT
`AND MOBILITY SUPPORT
`Q2931
`Q293
`SAAL ADDRESSMAPPING
`ATMLAYER
`WRELESS MAC
`
`WIRED MAC
`WIRED PHY
`
`CONTRO-
`
`-CDS SUPERFRAME
`
`s ATM DAA
`F.G. 5
`
`s CONTROL
`
`

`

`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 4 of 4
`
`5,787,080
`
`IPS1
`IPS2
`IPS3
`--
`-le
`-1-
`H
`- - - - -
`CONNECTION
`SLOT ACCESS/RELEASE PHASE
`SLOT CONFIRMATION
`SETUP!RELEASE
`PHASE
`PHASE
`FI G 6
`IPS-INTER-PHASESPACE
`
`X (TX)
`
`X (FN1)
`
`X (FN2)
`
`X (Rx)
`
`1. REQ RESOURCE
`2. SEND ACK BACK
`TO FN1
`
`1, REO RESOURCE
`2. ASKFN1 TO REQ
`RESOURCE
`
`
`
`1, REO RESOURCE
`2. ASKFN2 TO
`REO RESOURCE
`
`3. SEND ACK BACK
`TO FN
`FIG.7
`
`CDSSUPERFRAME (CENTRALIZED ARCHITECTURE)
`| --
`-H-I-H
`-
`- - - - -
`CONTROL ATM DATA (VP-LINK)
`ATM DATA (DOWN-LINK
`CONTROL
`FIG. 8
`
`

`

`5,787,080
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`1
`METHOD AND APPARATUS FOR
`RESERVATION-BASED WIRELESS-ATM
`LOCALAREA NETWORK
`
`15
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`25
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`required QoS, the delay incurred in the wireless ATM
`network can actually increase exponentially in an over
`loaded network. Such a channel-access protocol regarding
`the blocking of a service for which a wireless ATM network
`cannot guarantee a required QoS is not addressed in the
`IEEE 802.11 and the HPERLAN standards.
`Services which are supported over an ATM network have
`certain characteristics with regard to a time-varying feature
`of the data rate of service. For instance, a service may
`include a variable data rate. In addition, for each service.
`corresponding QoS parameters are expected to be sustained
`by the ATM network. Typical characteristics and corre
`sponding QoS parameters for a given service may include
`the following:
`Constant Bit Rate (CBR): a bit rate is specified.
`Variable Bit Rate-Restricted Transmission time (VBR
`RT): a sustained cell rate, maximum burst size, and
`bounded delay are specified.
`Variable Bit Rate-Non-Restricted Transmission time
`(VBR-NRT): a sustained cell rate and maximum burst
`size are specified.
`Available Bit Rate (ABR): best effort service-no band
`width guarantees except for a minimum rate negotia
`tion (i.e., no specific bandwidth allocation).
`Unspecified Bit Rate (UBR): ABR without any guaran
`teed rate.
`An important issue for consideration in the design of a
`wireless-ATM system is that the Medium Access Control
`(MAC) protocol, which specifies the method of access to the
`wireless channel among multiple users. must satisfy the
`basic requirements of ATM. As discussed above. one of the
`ATM requirements is that a wireless network must provide
`a quality-of-service (QoS) in terms of guaranteedbandwidth
`(among other criterion of cell-loss probability, delay
`considerations, etc.) for services such as CBR and VBR. It
`would thus be desirable to for the MAC protocol to enable
`system users to reserve space for their respective services
`and transmissions within the wireless network. Furthermore,
`it would be desirable that the reserved space be present for
`the entire duration of the service for each user.
`In light of the above, two distinct channels should be
`available to each user. The first channel includes a "control"
`channel which serves for implementing a reservation
`method. The second channel includes a "data" channel
`where each user can send data without having conflicts with
`other users. Such a reservation-based MAC protocol is thus
`essential for delivery of ATM cells over a wireless network.
`One reservation method which has been proposed for wire
`less ATM is described in the article "ATM Based Transport
`Architecture for Multiservices Wireless Personal Commu
`nication Networks", by D. Raychaudhri and N. Wilson,
`IEEE JSAC, pp. 1401-1414, October 1994. In the cited
`article, the reservation method fails to teach or suggest a
`method by which different users can specify different "band
`widths" for different periods and/or various lengths of time.
`In addition to the above. implementation of control and
`data channels depends upon a chosen network architecture.
`Essentially, there are two kinds of wireless network
`architectures, that is, centralized (or base-station oriented)
`architecture and distributed (or ad-hoc oriented) architec
`ture. The two types of wireless network architectures shall
`be briefly described in the following with reference to FIGS.
`1(a) and 10b).
`Centralized (base-station based) architecture has been
`used for years in cellular communications, e.g., GSM. In the
`case of GSM, service areas are divided into small regions,
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention generally relates to a method and apparatus
`for a wireless asynchronous transfer mode local area
`network, and more particularly, to a method and apparatus
`for implementing a reservation-based wireless asynchronous
`transfer mode local area network.
`2. Discussion of the Related Art
`The success of Global Satellite Mobile (GSM) systems
`establishes wireless communications as indispensable in
`modern life. While GSM has targeted only voice
`communications, the future communications content is
`clearly multimedia in nature. With respect to multimedia
`communications, asynchronous transfer mode (ATM) tech
`nology has been developed over wired networks to deal with
`high-speed data with different data rates, different quality
`of-service (QoS) requirements, and different connection or
`connectionless paradigms, etc. QoS requirements may
`include, for example, data reliability, delay considerations,
`and/or other requirements. It is then natural to assume an
`emergence of a combination of wireless and ATM-based
`service at a consumer end of a wired network Such a
`combination has the potential to open up a major multimedia
`communications market for the home or business.
`Existing efforts of building a wireless local area network
`(LAN) are focussed around emerging standards of the IEEE
`802.11 in US and the HIPERLAN in Europe. It is noted that
`these standards are nearing maturity, however, their devel
`opment did not take into consideration ATM-based service
`requirements of QoS guarantees for both real-time and data
`traffic. Essentially, the ATM-based service requirements
`come about by multiplexing video, audio, and data services
`(i.e., multimedia) in the same medium. Audio data does not
`require the packet-error reliability required of data services,
`but audio data cannot tolerate excessive delay. Video data
`can in general suffer more delay than audio; however, video
`data is intolerant to delay jitter. These delay and packet-error
`rate considerations were essentially what forced ATM to
`adopt a connection-oriented service. The delay and packet
`error rate considerations also forced error-control to be done
`end-to-end, instead of implementing error-control between
`every two nodes within a specified connection. Error-control
`is a method of ensuring reliability of packets at a node,
`whereupon a detection of a packet error at a node results in
`a packet retransmission request being sent to the transmit
`ting node. Such a strategy was feasible with wired fiber
`optic networks which have a very small packet error rate. In
`contrast, wireless networks generally do not provide such
`low packet error rates.
`Delay considerations are also important for ATM service.
`For instance, a wired ATM network will operate to simply
`block any services for which it cannot guarantee a required
`QoS. On the other hand, wireless networks typically do not
`allow such a feature of blocking any service for which it
`cannot guarantee a required QoS. Consider for instance the
`example of telephone service. It would be desirable for the
`telephone service to be blocked if the required QoS require
`ments cannot be met, since it is believed that one would
`rather prefer to have a call blocked than to have a call
`interrupted by a wireless network's inability to meet the
`required QoS requirements. Absent the feature of blocking
`a service for which the network cannot guarantee the
`
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`3
`called "cells." Each cell is served by a specific base station
`(BS) 12. Communications between different mobile termi
`nals (MTs) 14 are done via BSs 12 and/or a mobile switching
`center (MSC) 16. Centralized architecture is further char
`acterized by two different topologies, namely, tree topology
`and ring topology, as exemplified in FIG. 1(a) and FIG. 1(b),
`respectively. In the tree topology 10, the switching function
`is performed in a "hierarchical” manner. While switching for
`intra-cell calls is done in the respective BS 12, switching for
`inter-cell calls is conducted in the respective MSC 16.
`Normally, the switch in the MSC 16 is more sophisticated
`and complex than those in the BSs 12. In the ring topology
`20, the switching function is performed in a "distributed”
`manner. That is, while switching for intra-cell calls is done
`in the BS 12 as in the tree topology, switching for inter-cell
`calls is conducted by passing the call to the destined BS
`switch around the ring. Unlike the tree topology, the ring
`topology 20 uses identical BSs 12 and switches which
`makes it much easier to be scalable. Such a ring topology is
`described, for instance, in the article "ATM Local Area
`Networks. Using Distributed Switch Architecture" by Y. Du,
`and R. Kraemer, Globecom'94 November 1994.
`Making reference now to FIGS. 2(a) and 20b), unlike the
`centralized architecture, a distributed (ad-hoc) architecture
`does not require any base station. Instead, each of the mobile
`nodes (MNs) 32 has its own capability to perform switching
`as well as communicate directly with other MNs 32 of the
`distributed architecture. All of the MNs 32 togetherforman
`ad-hoc network, such as described in the HPERLAN and
`IEEE 802.11 standards. In an ad-hoc network, there are
`essentially two types of topologies, namely, a fully
`connected topology (FCT) and a forwarding-node topology
`(FNT), as exemplified in FIG. 2(a) and FIG. 2(b), respec
`tively. In the fully-connected topology (FCT) 30, all devices
`at home are assumed to be able to talk to each other.
`Sufficient power is assumed to be used by a device such that
`it can maintain a link with every other device. In the
`forwarding-node topology (FNT)40, not all devices can talk
`to each other. The home is then partitioned into partially
`connected "cells" with some of the mobile nodes being
`designated as forwarding nodes 34.
`SUMMARY OF THE INVENTION
`An object of the present invention is to overcome the
`problems in the art discussed above.
`Another object of the present invention is to provide a
`MAC protocol which enables system users to reserve space
`for their respective services and transmissions within the
`wireless network, wherein the reserved space is present for
`an entire duration of a respective service for each user.
`According to the present invention, a method for imple
`menting a reservation-based wireless asynchronous transfer
`mode (ATM) local area network (LAN) includes the steps
`of: a) providing a system architecture of mobile nodes
`(MNs), each MN for communicating with various ones of
`the other MNs; b) supporting a plurality of services, each
`service having respective quality-of-service (QoS) require
`ments; and c) implementing a medium access control
`(MAC) layer using a reservation-based communications
`protocol, wherein the protocol (i) divides all MAC-based
`communications between a control channel and a data
`channel, wherein the control channel and the data channel
`together comprise a control-data superframe (CDS) and (ii)
`utilizes the control channel for allocating a bandwidth of the
`data channel to each service, the control channel having a
`control frame during which an allocation of data payload
`slots of the data channel is determined according to (a) a
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`long-term strategy corresponding to a time of service
`required to complete a service over multiple CDS frames
`and (b) a short-term strategy within a CDS frame corre
`sponding to instantaneous data payload slot requirements for
`a particular service, thereby achieving respective QoS
`requirements of each service.
`In addition, according to the present invention, a
`reservation-based wireless asynchronous transfer mode
`(ATM) local area network includes a system architecture of
`mobile nodes (MNs), each MN for communicating with
`various ones of the other MNs. A plurality of services is
`supported wherein each service has respective quality-of
`service (QoS) requirements. A medium access control
`(MAC) layer using a reservation-based communications
`protocol is provided, wherein the protocol divides all MAC
`based communications between a control channel and a data
`channel, the control channel and the data channel together
`making up a control-data superframe (CDS). The protocol
`further utilizes the control channel for allocating a band
`width of the data channel to each service. The control
`channel includes a control frame during which an allocation
`of data payload slots of the data channel is determined
`according to (a) along-term strategy corresponding to a time
`of service required to complete a service over multiple CDS
`frames and (b) a short-term strategy within a CDS frame
`corresponding to instantaneous data payload slot require
`ments for a particular service. Respective QoS requirements
`of each service are thus achieved.
`Still further, in accordance with the present invention, a
`mobile node (MN) for use in a reservation-based wireless
`asynchronous transfer mode (ATM) local area network
`(LAN) having a system architecture and supporting a plu
`rality of services, each service having respective quality-of
`service (QoS) requirements is disclosed. The mobile node
`includes a medium access control (MAC) layer using a
`reservation-based communications protocol, wherein the
`protocol (i) divides all MAC-based communications
`between a control channel and a data channel, wherein the
`control channel and the data channel together comprise a
`control-data superframe (CDS) and (ii) utilizes the control
`channel for allocating a bandwidth of the data channel to
`each service, the control channel having a control frame
`during which an allocation of data payload slots of the data
`channel is determined according to (a) a long-term strategy
`corresponding to a time of service required to complete a
`service over multiple CDS frames and (b) a short-term
`strategy within a CDS corresponding to instantaneous data
`payload slot requirements for a particular service, thereby
`achieving respective QoS requirements of each service.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The foregoing and other teachings and advantages of the
`present invention will become more apparent upon a
`detailed description of the best mode for carrying out the
`invention as rendered below. In the description to follow,
`reference will be made to the accompanying drawings in
`which like reference numerals are carried forward, and in
`which:
`FIG. 1(a) and 1(b) illustrate a wired ATM local area
`network having a centralized (base-station-based) architec
`ture in a tree topology and a ring topology, respectively;
`FIG. 2(a) and 20b) illustrate a wired ATM local area
`network having a distributed (ad-hoc) architecture in a
`fully-connected topology (FCT) and a forwarding -node
`topology (FNT), respectively;
`FIG. 3 shows a wired/wireless ATM layered model for
`centralized (base-station-based) architectures having a
`
`

`

`5
`medium access control (MAC) layer using a reservation
`based protocol according to the present invention;
`FIG. 4 shows a wired/wireless ATM layered model for
`distributed (ad-hoc) architectures having a medium access
`control (MAC) layer using a reservation-based protocol
`according to the present invention;
`FIG. 5 shows a control-data superframe (CDS) of the
`medium access control (MAC) layer using a reservation
`based protocol according to the present invention;
`FIG. 6 illustrates the control frame of the CDS frame in
`accordance with the present invention;
`FIG. 7 illustrates an ATM connection for an forwarding
`node topology of a distributed architecture in connection
`with the medium access control (MAC) layer using a
`reservation-based protocol according to the present inven
`tion; and
`FIG. 8 illustrates the control frame of the CDS frame for
`a centralized architecture in accordance with the present
`invention.
`DETALED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`A reservation-based MAC protocol according to the
`present invention is considered for two distinct types of
`network architectures, namely, the centralized (base-station
`based) architecture and the distributed (ad-hoc) architecture.
`Specifically, in the centralized architecture, both control and
`data channels are implemented in the centralized mode. In
`the distributed architecture, the control channel is imple
`mented in either the distributed or the centralized mode and
`the data channel is preferably in the distributed mode. A
`centralized control channel in a distributed network archi
`tecture may be preferable based on a significant simplifica
`tion of the MAC layer protocols, which may then be
`incorporated within every device with a method of choosing
`a "current" central controller. It is also possible that a
`centralized control facility in a distributed architecture may
`be implemented which is less expensive than a distributed
`control facility, and hence, both centralized and distributed
`control scenarios for the distributed architecture are dis
`cussed herein below,
`In accordance with the present invention, with respect to
`a distributed (ad-hoc) architecture, the control channel or the
`data channel of the ATM network can be implemented in
`either a centralized or a distributed mode. When the control
`channel is implemented in a centralized mode, all control
`messages from mobile users (i.e. MNs) must be sent to a
`designated central controller where control actions are deter
`mined and transmitted back to the user. In contrast, for a
`distributed control channel, no central controller is used and
`all control functions are distributed among the mobile users
`(i.e., MNs). In this later case, it is important to maintain a
`consistent control database among all of the mobile users.
`When the data channel is implemented in a centralized
`mode, transmission of packets between two users must be
`done through a designated central node. For a distributed
`data channel, no central node is assigned and transmission of
`packets between two users is done directly. In this later case
`of a distributed data channel, it is not necessary to transmit
`packets from the transmitter to a central node and then from
`the central node back to the receiver, thereby making effi
`cient use of valuable total wireless system bandwidth and
`thus consequently not wasting the same.
`In a preferred embodiment, the control channel is imple
`mented in a centralized mode and the data channel is
`implemented in a distributed mode. That is, in the preferred
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`embodiment, the reservation-based MAC protocol, to be
`discussed further herein below, forces the control channel to
`be centralized while the data channel is distributed. Such a
`reservation-based MAC protocol advantageously provides a
`more reliable access control and further provides data trans
`mission having high reliability and high data transmission
`throughput.
`An essential idea according to the method and apparatus
`of the present invention is two-fold. That is, first, to split all
`MAC-based communications within a control channel and
`the data channel in a reservation based scheme via a control
`data superframe (CDS), and, second, using the control
`channel, to be able to allocate a nominal bandwidth to every
`user (i.e., MN or MT) on a first-come-first-served basis until
`a maximum bandwidth allocation for the system is reached.
`To ensure that different ATM services are possible, at the
`moment of transmission, an actual allocation of bandwidth
`is requested by each MN requiring ATM service. Thus, there
`are two methods of allocation-one long-term (referred
`hereinafter as "call-level allocation") and another short-term
`or immediate allocation (referred hereinafter as "slot-level
`allocation").
`An advantage of the present invention is that the
`reservation-based MAC protocol is independent of the
`assumption of whether a distributed or a centralized archi
`tecture is used. As will be discussed hereinbelow, with minor
`modifications, the MAC protocol according to the present
`invention can be used for both centralized and distributed
`architectures.
`To place the Medium Access (MAC) protocol in
`perspective, a layered model for a wireless-ATM system
`with centralized architecture is shown in FIG, 3. Layered
`models, including various named layers as shown, are
`known in the art and thus only briefly described herein. At
`the base station 12, ATM switching is performed and
`resource and mobility management are handled. Using sepa
`rate MAC and PHY (physical) layers, the base station 12 can
`handle both wired-ATM traffic and wireless-ATM traffic as
`shown by the "shaded" application path 50 between a
`wired-ATM terminal 52 and a mobile ATM terminal 54 in
`FIG. 3.
`In regard to earlier discussion herein about the control and
`the data channels, the ATM layer is concerned only with the
`data channel and not with the control channel. In the layered
`model, the layer below does not know the layer above. It is
`the wireless MAC layer which essentially specifies how the
`user interacts with the control channel. Once a reservation is
`made for a particular amount of channel bandwidth, ATM
`cells from the output of the ATM layer are sent over the
`wireless channel. The "wireless control and management
`function" resides inside the "resource management and
`mobility support" block. Although not shown in the figure,
`the "ATM control and management function" interworks
`with the wireless control and management function, which,
`in turns, can communicate with the wireless MAC and PHY
`layers. This information exchange, as briefly discussed, is
`required to setup and tear down wireless physical
`connections, which is usually never done for a wired link.
`Mobility management also falls within this aspect, which is
`not further dealt with herein.
`In the distributed (ad-hoc) architecture, the layered model
`for each of the mobile nodes (MNs) is similar to that for the
`base station (BS) in the centralized scenario, except that the
`mobile node has to handle applications as well. The layered
`model for the mobile node of the distributed (ad-hoc)
`architecture is shown in FIG. 4.
`
`

`

`7
`With the above discussion regarding the location of the
`MAC layer, we can now discuss the implementation of the
`MAC layer in detail. Note that for the MAC reservation
`based communications protocol according to the present
`invention, it is not necessary to follow exactly the layering
`as discussed above.
`According to the present invention, several basic assump
`tions for the MAC reservation-based protocol are made. In
`particular, these basic assumptions are made for the wireless
`ATM network. They include the following:
`1. QoS must be guaranteed.
`2. A wide variation in data rates is expected, for example,
`from several Kbps (kilobits per second) to several tens
`of Mbps (mega bits per second).
`3. Both asynchronous (e.g., for file transfer) and isoch
`ronous (e.g., for video) services must be supported.
`4. ATM cells address many different receivers. These
`ATM cells are further multiplexed randomly. It is not
`known to the MAC layer which packets address which
`user, although it is possible to specify some local
`neighborhood information about the packet to the
`MAC layer.
`5. A user cannot both transmit and receive at the same
`time.
`6. A known preamble must be sent by every transmitter to
`25
`let the receiver equalizer adapt to the channel. The
`preamble is part of the transmitter turnaround time
`which is the time it takes for a transmitter to stop
`transmission and another transmitter to start transmis
`S10.
`7. The unit of information transfer is assumed to be an
`ATM cell and additional overhead of any other layers.
`This unit is called an ATM slot.
`In an ATM network, time slots are allotted for control
`purposes and data purposes. That is, essentially, any control
`or data packets are viewed as occupying time slots.
`In accordance with the present invention, a concept of a
`Control-Data Superframe (CDS) shall now be discussed. As
`mentioned earlier hereinabove, one aspect of the MAC
`protocol is a reservation-based policy. wherein, during the
`control phase, a certain number of ATM slots are reserved
`for a particular user. A Control-Data Superframe (CDS) is
`herein defined as consisting of a single control sequence
`followed by a data sequence. During the control sequence,
`multiple users (i.e., MNs or MTs) specify and request a
`number of ATM slots required for each of their respective
`use. Once this request is successful, each user then transmits
`its designated packets in a specified sequence during the data
`slots. The specified sequence is determined in accordance
`with an outcome of the control sequence. Hence, multiple
`access methods are used only during the control sequence
`with no contention over the data slots. The throughput of this
`method is based upon the ratio between the size of the data
`slots required to the total size of the superframe. A CDS
`frame is shown in FIG.S.
`With respect to the CDS frame, the number of data slots
`is allowed to be variable up to a maximum number.
`Similarly, the number of control slots are also variable up to
`a maximum number. The specific number of data slots and
`control slots for the data channel and the control channel,
`respectively, must be determined by realistic traffic studies
`within a wireless network. Note also that there will be a
`transmitter turnaround time associated with every user that
`transmits during a CDS. It is assumed that the transmitter
`turnaround time is a submultiple of an AM slot.
`There are essentially three kinds of users in an ATM
`network. The following definitions and terminology are
`65
`provided herein below for further use and understanding,
`which include:
`
`45
`
`35
`
`50
`
`55
`
`5,787,080
`
`10
`
`15
`
`20
`
`8
`1. Dormant Users (DU) and Networked Users (NU):
`among all possible users, there will always be some
`users who are connected to the wireless network at a
`specific time-these users are termed Networked Users
`(NU). The users which are not NU are called Dormant
`Users (DU).
`2. Inactive Networked Users (INU): among all NU, there
`are users who currently have no data to send, or cannot
`send data because the network is fully loaded. These
`users are termed INU.
`3. Active Networked Users (ANU): finally among all NU,
`those users which have been allocated a specific con
`nection are termed ANU.
`Turning now to FIG. 6, a control frame (i.e., the control
`channel) for use in the present invention shall be described.
`The control frame is composed of a number of phases,
`preferably to include, at a minimum, three phases as shown
`in FIG. 6. The three phases include a Connection Setup/
`Release Phase, a Slot Access/Release Phase, and a Slot
`Confirmation Phase. The Connection Setup/Release Phase is
`used for call-level allocations (i.e., long term allocations),
`whereas, the Slot Access/Release and Slot Confirmation
`Phases are used for slot-level allocations (i.e., short term
`allocations). A central controller allocates/arbitrates data
`slots for the data channel for each requested service. Each
`phase of the control frame can be of variable length.
`depending upon the number of MN users requesting service,
`up to a prescribed maximum as determined by overall
`system requirements. The control frame (i.e., control
`channel) within the CDS thus includes a minimum of three
`phases, and may include further phases or combinations of
`phases. Functionalities have to be done in some prescribed
`order, as determined, for example by the overall system
`requirements. The end of a given phase can be specified by
`an occurrence of no signal having been trans