United States Patent (19)
`Wright et al.
`
`54 SUBSCRIBER-ORIGINATED CALL
`DEFERRED QUEUING
`75 Inventors: Andrew S. Wright, Vancouver, Canada;
`ar Most it. E.
`Springs Colo.: RNG Kendrick
`
`Gibbs, Colorado Springs, Colo.
`
`73 Assignee: Opuswave Networks, Inc., Colorado
`Springs, Colo.
`
`21 Appl. No.: 09/015,379
`1-1.
`22 Filed:
`Jan. 29, 1998
`(51) Int. Cl. ................................................ G06F 15/16
`52 U.S. Cl. .......................... 709,227,709,219, 709/226.
`709/229; 370230. 370,280. 370283
`58) Field of Search
`s
`395/200 s 200.33
`39520049, 20056,200 59: 700327 200.
`219 226 229. 370230 280 2s2. 29 4.
`s
`s
`s
`s 295 33 3 47
`s
`s
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`1/1992 Nassehi et all
`370/85.2
`5,081,622
`8/1994 Ben-Michael et al... 370,85.13
`5.336,313
`5,404,353 4/1995 Ben-Michael et al. ................... 370/79
`
`USOO6078959A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,078,959
`Jun. 20, 2000
`
`5,408,468 4/1995 Petersen .................................. 370/377
`5,457,735 10/1995 Erickson ................................. 455/450
`5,493,651
`2/1996 Crouse et al. ......
`395/200.14
`55: 2.1. But t al. .................... Sh
`2- .
`.
`OSCOllel al. . . . . . . . . . . . . . . . . . . . . . . . . . . .
`5,596,572
`1/1997 Will-Fire et al. ....................... 370/360
`57.7 3. E. et al. .....
`32.3
`
`2
`
`a
`
`2
`
`OOO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Primary Examiner Zarni Maung
`Assistant Examiner Saleh Najjar
`57
`ABSTRACT
`57
`Methods and apparatus for queuing Subscriber-originated
`connection requests for respective calls at a Server System.
`A Server System in a telecommunications network receives
`Subscriber-originated connection requests for Subscriber
`pending call access to the Server System, and thus, the
`network. Subscriber-originated connection requests are
`queued at the receiving Server System. The Server System
`receiving the Subscriber-originated connection request trans
`mits a first message to the respective Subscriber originating
`the connection request upon the Server System's queuing of
`the connection request. Subsequently, upon the Server Sys
`tem allocating a connection resource to a queued Subscriber
`originated connection request, the Server System transmits a
`Second message to the respective Subscriber.
`
`20 Claims, 10 Drawing Sheets
`
`205
`N
`N
`N
`s
`N
`N
`N
`N
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`202
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`206 -->
`DOWnlink
`Frequency
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`207 -->
`Uplink
`Frequency
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`2O3
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`203
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`205
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`o o s 204
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`202
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`208
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`SS
`
`N
`N
`N
`s
`N
`N
`N
`N
`N
`N
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 1 of 21
`
`

`

`U.S. Patent
`US. Patent
`
`Jun. 20, 2000
`Jun. 20, 2000
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 2 of 21
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`Jun. 20, 2000
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 3 of 21
`
`

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`U.S. Patent
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`Jun. 20, 2000
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 4 of 21
`
`

`

`U.S. Patent
`US. Patent
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`Jun. 20, 2000
`Jun. 20, 2000
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 5 of 21
`
`

`

`U.S. Patent
`
`Jun. 20, 2000
`
`Sheet S of 10
`
`6,078,959
`
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 6 of 21
`
`

`

`U.S. Patent
`
`Jun. 20, 2000
`
`Sheet 6 of 10
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`6,078,959
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 7 of 21
`
`

`

`U.S. Patent
`
`Jun. 20, 2000
`
`Sheet 7 of 10
`
`6,078,959
`
`Call Blocking
`Subscriber Originated //
`Packet Data Traffic ly
`Subscriber Originated
`|
`A. CCT SWitched Traffic
`/ Network Originated
`Packet Data Traffic
`Z/
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`FIG. 7A (PRIOR ART)
`Call Blocking
`subscribe originated //
`tryA yggia
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`Packet Data Traffic
`1.
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`27 ||
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`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 8 of 21
`
`

`

`U.S. Patent
`
`Jun. 20, 2000
`
`Sheet 8 of 10
`
`6,078,959
`
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`ERICSSON v. UNILOC
`Ex. 1023 / Page 9 of 21
`
`

`

`U.S. Patent
`US. Patent
`
`Jun. 20, 2000
`Jun. 20, 2000
`
`Sheet 9 of 10
`Sheet 9 0f 10
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`6,078,959
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`ERICSSON V. UNILOC
`
`EX. 1023 /Page 10 of21
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 10 of 21
`
`

`

`U.S. Patent
`US. Patent
`
`Jun. 20, 2000
`Jun. 20, 2000
`
`Sheet 10 of 10
`Sheet 10 0f 10
`
`6,078,959
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`ERICSSON V. UNILOC
`
`EX. 1023 /Page 11 of21
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 11 of 21
`
`
`
`

`

`6,078,959
`
`1
`SUBSCRIBER-ORIGINATED CALL
`DEFERRED QUEUING
`FIELD OF THE INVENTION
`The field of this invention pertains to
`telecommunications, including a telecommunications net
`work Server that provides equity of access between network
`and Subscriber-originated connection requests for respective
`pending calls.
`DESCRIPTION OF THE TECHNOLOGY
`Circuit-Switched, i.e., Switch/router or Server, System pro
`viders provide connection resources, i.e., Servers, for con
`nection requests to a telecommunications network. A Service
`Supported by a telecommunications network, e.g., telephony
`or packet data, generally uses both network-originated and
`Subscriber-originated connection requests for access to the
`Server System. In addition, a Scheme of random acceSS
`Signalling is used to aid Subscriber devices in obtaining an
`available resource for a connection request on the Server
`System.
`Network-originated connection requests are generally
`queued at the respective receiving Server System if the Server
`System does not have an adequate number of connection
`resources to allocate to them at the time of their receipt. The
`network-originated connection requests remain queued at
`the Server System until they are either Serviced, i.e., allocated
`one or more connection resources, or until they are deleted
`from the respective queue because their associated lifetime,
`i.e., the time they are to be maintained waiting for allocation
`of one or more connection resources, expires. If a connec
`tion resource is deleted, the respective call is deemed
`dropped.
`In contrast, in the prior art, Subscriber-originated connec
`tion requests are not queued at a respective Server System.
`Upon receiving a Subscriber-originated connection request
`that it cannot allocate the necessary connection resources to,
`a Server System either transmits a message indicating that the
`connection request cannot be Serviced, or simply ignores the
`connection request. In either case, the Subscriber originating
`the connection request may begin an appropriate back off
`procedure before again attempting access to a Server System
`for its respective pending call. This, in turn, provides an
`advantage to network-originated connection requests, as
`they may simply be queued at the respective Server System,
`awaiting a connection resource allocation.
`When a connection resource does become available at a
`respective Server System, it will generally be allocated to a
`queued network-originated connection request. AS
`Subscriber-originated connection requests that cannot be
`Serviced upon receipt are not queued at the respective Server
`System, they must necessarily be re-transmitted to the Server
`System. The Server System, for its part, generally Services the
`queued network-originated connection requests already at
`the Server System over Subscriber-originated connection
`requests that are necessarily retransmitted to the Server
`System, and, thus, are not generally at the Server System
`when connection resources become available. The resultant
`preferential advantage to network-originated connection
`requests is undesirable if a goal of the network is to provide
`equity of access to both network and Subscriber-originated
`traffic.
`Execution of a back off procedure and Subsequent
`re-attempts to access connection resources for a pending call
`also results in additional Subscriber-originated connection
`requests being transmitted to a server System. Moreover,
`
`15
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`25
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`additional random access Signalling must be executed, to aid
`Subscribers in obtaining available connection resources on
`the Server System. The Subsequent higher rate of random
`acceSS Signalling which generally results leads to additional
`traffic congestion on the Server System. Additionally it can
`create an undesirable increase in co-channel interference at
`a Server System, which in turn can lead to a reduction in
`Server System capacity for traffic handling because of a
`corresponding increase in Server interchange activity.
`Thus, it would be advantageous to provide a network
`System that afforded equity of acceSS between network and
`subscriber-originated traffic. Additionally, it would be
`advantageous to provide a network System that required
`minimum random acceSS Signalling and minimum
`Subscriber-originated connection request transmissions for
`respective calls, especially those generated in the prior art
`during heavy traffic loading conditions.
`
`SUMMARY OF THE INVENTIONS
`The present inventions provide a network Server System
`that offers equity of access between network and Subscriber
`originated connection requests for respective pending calls.
`The inventions comprise methods and apparatus for queuing
`Subscriber-originated connection requests at a Server System,
`in order that they may be allocated applicable connection
`resources when the respective resources Subsequently
`become available.
`In a presently preferred embodiment, a network Server
`System queues a Subscriber-originated connection request if
`it correctly receives one at a time when the Server System has
`an inadequate number of connection resources to allocate to
`it. The Server System transmits a message to the respective
`Subscriber originating the connection request upon the queu
`ing of the Subscriber's connection request. Subsequently, if
`and when the Server System does allocate a connection
`resource to the queued Subscriber-originated connection
`request, it transmits a Second message to the respective
`Subscriber, generally indicating the allocation of connection
`resources for the respective connection request.
`Thus, a general object of the present inventions is to
`Support equity of access between network and Subscriber
`originated connection requests at a respective network
`Server System. Other and further objects, features, aspects
`and advantages of the present inventions will become better
`understood with the following detailed description of the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a presently preferred network
`embodying dual Service Server Systems.
`FIG. 2 is a presently preferred embodiment of a TDMA
`time frame/time slot Structure.
`FIG. 3 is a block diagram of a dual service server system.
`FIG. 4 illustrates the handling of an exemplary network
`originated connection request at a Server System.
`FIG. 5 is an illustrative random access Signalling
`Sequence between a Subscriber and a base Station.
`FIG. 6 is an exemplary Subscriber collision Scenario.
`FIGS. 7A and 7B are prior art call blocking graphs.
`FIG. 8 is an illustrative connection request Scenario in a
`prior art Server System.
`FIG. 9 illustrates the handling of an exemplary Subscriber
`originated connection request at a presently preferred
`embodiment base Station.
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 12 of 21
`
`

`

`3
`FIG. 10 is an illustrative connection request Scenario in a
`presently preferred embodiment base Station.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`A presently preferred network embodying dual Service
`Server Systems in accordance with the present inventions is
`described in copending U.S. patent applications Ser. No.
`08/886,853, entitled “Resource Controllers For Use in a
`Non-Unitary Service System”, and, entitled “Methods for
`Resource Control in a Non-Unitary Service System”, both
`hereby incorporated by reference as if fully set forth herein.
`In particular, in a presently preferred network 101 of FIG.
`1, both a primary and a Secondary Service are Supported. In
`a presently preferred embodiment, the primary Service is a
`circuit Switched Service, which may include Voice, i.e.,
`telephony, messages. The primary Service is generally char
`acterized by relatively low connection request arrival rates
`and relatively long connection in progreSS, i.e., call Service,
`times. When a primary Service connection request is allo
`cated a respective connection resource for communication
`on the network, it becomes a connection in progreSS.
`In a presently preferred embodiment, the Secondary Ser
`Vice is a packet data Service, which may consist of data
`messages. The Secondary Service is generally characterized
`by relatively high connection request arrival rates and rela
`tively short connection in progreSS Service times. AS with a
`primary Service connection request, when a Secondary Ser
`Vice connection request is allocated a respective connection
`resource, it becomes a connection in progreSS.
`In a presently preferred embodiment, network 101 is a
`wireless network. Alternative network embodiments include
`wireline or wireleSS/wireline, including local area networks
`(“LAN's) and wide area networks (“WAN's). Additionally,
`there is no requirement that the network Support two
`Services, or only two Services. For example, a Single-Service
`Server System could be used in a network Supporting, e.g.,
`Voice or data. AS another example, a tri-Service Server
`System could be used in a network Supporting, e.g., voice,
`data, and Video on demand.
`Network 101 is comprised of a plurality of server systems
`102. In a presently preferred embodiment, each server
`system 102 is a base station. Each base station 102 may
`communicate with a plurality of network Subscribers 103 via
`over-the-air communication linkS 145, e.g., radio airwaves.
`Each base station 102 has a primary Service interface (not
`shown) which connects the base station 102 to a base station
`controller 155, via a communication link 106. Each base
`station controller 155 is linked, via a communication link
`160, to a circuit Switched network 105. The circuit Switched
`network 105 may be, but is not limited to, a GSM network
`or a POTS network. The communication links 106 may
`include, but are not limited to, e.g., a coaxial cable, a fiber
`optic cable, a digital radio link, or a telephone line. The
`communication links 160 may include, but are not limited
`to, e.g., a coaxial cable, a fiber optic cable, a digital radio
`link, or a telephone line.
`Each base Station 102 also has a Secondary Service
`interface (also not shown) which connects the base Station
`102 to a packet data network 108, via a communication link
`109. Alternatively, each base station 102 may communicate
`with a base station controller 155 via a communication link
`106. The respective base station controller 155, in turn,
`communicates with the packet data network 108 via a
`communication link 150. The communication links 109 may
`include, but are not limited to, e.g., a coaxial cable, a fiber
`
`15
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`6,078,959
`
`4
`optic cable, a digital radio link, or a telephone line. The
`communication links 150 may include, but are not limited
`to, e.g., a coaxial cable, a fiber optic cable, a digital radio
`link, or a telephone line.
`Each base Station 102 may receive primary Service con
`nection requests from both subscribers 103 and from the
`circuit Switched network 105. Each base station 102 may
`also receive Secondary Service connection requests from
`both subscribers 103 and from the packet data network 108.
`In a presently preferred embodiment, each base Station
`102 of FIG. 1 employs a time division multiple access/
`frequency division duplex, i.e., TDMA/FDD, frame/slot
`Structure for transmission and reception of communications
`to and from Subscribers 103. In a presently preferred
`embodiment, each time frame 202 of FIG. 2 is equally
`divided between thirty-two full duplex time slots 203. Thus,
`in a presently preferred embodiment, there are thirty-two
`time slots 203, or connection resources, which collectively
`comprise a respective base station's over-the-air (“OTA)
`
`CSOUCC.
`A channel 204 is a collection, over a generally extended
`period of time, of the same time slot 203 (or time slots) in
`consecutive time frames 202. Generally, when a connection
`request is allocated a connection resource, it is allocated a
`channel 204, i.e., one or more time slots 203 over a plurality
`of time frames 202.
`In a presently preferred embodiment, a base station 102 is
`allocated a first frequency for its transmit function. This first
`frequency is generally deemed a downlink frequency. The
`base station 102 transmits to subscribers 103 of the respec
`tive network system 101 at the downlink frequency 206. In
`a presently preferred embodiment, the downlink frequency
`206 is within the PCS bands.
`In a presently preferred embodiment, the subscribers 103
`of the respective network system 101 are allocated a second
`frequency, different from the downlink frequency, for their
`transmit function. This Second frequency is generally
`deemed an uplink frequency. The subscribers 103 of the
`network system 101 transmit to a base station 102 at the
`uplink frequency 207. In a presently preferred embodiment,
`the uplink frequency 207 is within the PCS bands.
`For example, if a subscriber 103 requests a connection
`resource on a base Station 102, it may be allocated channel
`204 of FIG. 2, which consists of the thirty-second time slot
`205 at the downlink frequency 206 and the twentieth time
`slot 208 at the uplink frequency 207 for a plurality of time
`frames 202. Upon allocation of channel 204, the respective
`subscriber 103 transmits to the base station 102 at the uplink
`frequency 207 in each time slot 208 of each time frame 202
`for the duration of the connection in progress. Upon allo
`cation of channel 204, the base station 102 transmits to the
`respective subscriber 103 at the downlink frequency 206 in
`each time slot 205 of each time frame 202 for the duration
`of the connection in progreSS. AS depicted in FIG. 2, in a
`presently preferred embodiment, time slot(s) allocated to be
`used at the uplink frequency (e.g., time slot 208 at uplink
`frequency 207) generally differ from time slot(s) allocated to
`be used at the downlink frequency (e.g., time slot 205 at
`downlink frequency 206) of a respective channel (e.g.,
`channel 204).
`Referring to FIG. 3, a respective Server System, e.g., base
`Station 102, receives a plurality of Subscriber-originated
`primary Service connection requests 302, a plurality of
`network-originated primary Service connection requests
`303, a plurality of Subscriber-originated secondary service
`connection requests 304 and a plurality of network
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 13 of 21
`
`

`

`S
`originated Secondary Service connection requests 305. If the
`base Station 102 allocates one or more time slots. i.e.,
`Servers, or connection resources, to any primary Service
`connection request 302 or 303, the connection request
`becomes a primary Service connection in progreSS 306.
`Likewise, if the base station 102 allocates one or more time
`Slots to any Secondary Service connection request 304 or
`305, the connection request becomes a Secondary Service
`connection in progress 307.
`The arrival rates of the primary Service connection
`requests 302 and 303 and the service times of the primary
`Service connections in progreSS 306 at a respective base
`Station 102 are generally, but not necessarily, identical,
`irrespective of the originating Source, i.e., network
`originated or Subscriber-originated. The arrival rates of the
`secondary service connection requests 304 and 305 and the
`Service times for the Secondary Service connections in
`progress 307 at a respective base station 102 may also be,
`but are not necessarily, identical, irrespective of the origi
`nating Source. However, the connection request arrival rates
`and the connection in progreSS Service times associated with
`each Service, primary and Secondary, generally differ. In
`particular, the primary Service is characterized by generally
`lower connection request arrival rates and longer connection
`in progreSS Service times than the Secondary Service.
`Referring to FIG. 4, a typical network-originated connec
`tion request 402 arrives at a respective server system 410.
`Network-originated connection request 402 is a request from
`an associated network for a connection link, i.e., time slot
`allocation, on the Server System 410, for use in Subsequent
`communications with a Subscriber. Upon receiving the
`network-originated connection request 402, the Server Sys
`tem. 410 checks if it has available connection resources to
`Service it. If not, the Server System 410 queues the connec
`tion request 402 to either a network primary Service queue
`403 or a network secondary service queue 404, determined
`by whether the network-originated connection request 402 is
`for a circuit Switched or a packet data Service respectively.
`If there are available connection resources to allocate to
`the network-originated connection request 402, the Server
`System 402 checks to see if there are any queued, i.e.,
`pending, connection requests. If not, the Server System 410
`allocates the appropriate number of time slots 406 to the
`connection request 402, which is then designated a connec
`tion in progreSS 407. If, however, there are pending connec
`tion requests in the network primary Service queue 403
`and/or the network Secondary Service queue, the Server
`system 410 queues the connection request 402 to the net
`work primary Service queue 403, where is designated a
`pending connection request 405.
`The server system 410 interrogates queues 403 and 404
`periodically to determine if either have any pending con
`nection requests. For exemplary purposes, assume connec
`tion request 402 is for a circuit Switched Service, and has
`been queued in the Server System's network primary Service
`queue 403; thus, it is a pending connection request 405. The
`server system 410, if it has an appropriate number of
`available time slots 406 to allocate to the pending connec
`tion request 405 when it interrogates service queue 403,
`removes the pending connection request 405 from the Ser
`Vice queue 403 and allocates the necessary time slot(s) to it.
`At this time, the connection request 402 is designated a
`connection in progress 407.
`In a presently preferred embodiment, one or more time
`Slots, i.e., connection resources, may also be negotiated for
`and allocated, or assigned, to an individual Subscriber with
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`a connection request for a Server System, i.e., base Station.
`The negotiation for time slots on a base Station by a
`Subscriber can take place at any time through a random
`acceSS Signalling Sequence.
`In a random access Signalling Sequence a base Station
`transmits a message in a time slot at the downlink frequency
`indicating that a Subscriber can transmit the base Station a
`message for a connection request in a time slot at the uplink
`frequency. More particularly, the base Station transmits a
`poll message in a time slot at the downlink frequency to
`indicate that a Subscriber may transmit a resource request
`message in a time slot at the uplink frequency, for a
`connection request to the base Station. In a presently pre
`ferred embodiment, the poll message indicates one or more
`time slots in which a Subscriber may transmit a resource
`request message to the respective base Station. In an alter
`native embodiment, a Subscriber transmits a respective
`resource request message in the same time slot of the
`Subsequent time frame in which the base Station transmits a
`poll message.
`In a presently preferred embodiment, a base Station typi
`cally transmits two poll messages per time frame, i.e.,
`utilizes two time slots per time frame for poll message
`transmission, under generally low to moderate traffic con
`ditions. As a base Station experiences heavy traffic condi
`tions it can resort to transmitting only one or no poll
`messages per time frame, until traffic conditions return to
`moderate or low levels.
`When a call becomes pending at a Subscriber, the Sub
`Scriber listens at the downlink frequency for a poll message.
`Upon receipt of a poll message, the Subscriber examines it
`and then transmits a proper resource request message in an
`appropriate time slot at the uplink frequency to the respec
`tive base Station, requesting connection resources to the base
`Station. In a normal, Successful random access Signalling
`Sequence, the base Station, upon receipt of the resource
`request message from the Subscriber, responds by transmit
`ting a resource acknowledge message to the Subscriber,
`identifying the time slot(s) that are to be used by the
`Subscriber for transmitting and/or receiving its Subsequent
`circuit Switched or packet data messages to/from the base
`Station.
`In a presently preferred embodiment, a base Station allo
`cates one or more available time slots to random access
`Signalling, i.e., poll/resource request message transmission/
`reception, before it allocates time slots for either any pri
`mary Service connection request, network or Subscriber
`originated, or any Secondary Service connection request,
`network or Subscriber-originated. Similarly, in a presently
`preferred embodiment, a base Station allocates time slots for
`primary Service connection requests, network or Subscriber
`originated, before it Services any Secondary Service, network
`or Subscriber-originated, connection request.
`Referring to FIG. 5, a random acceSS Signalling Sequence
`between a Subscriber and a server System, e.g., base Station,
`is illustrated. In time slot 505 of time frame 501, a call
`becomes pending at a subscriber. In time slot 506 of time
`frame 501, the Subscriber receives a poll message from the
`base Station indicating that a resource request message may
`be sent by the subscriber in time slot 507. The subscriber
`transmits an appropriate resource request message in time
`slot 507 of time frame 501 and the base station responds
`with a resource acknowledge message for the Subscriber in
`time slot 508 of time frame 502. The resource acknowledge
`message in this exemplary Scenario indicates that the Sub
`scriber is to use time slots 510 of the present and Subsequent
`
`ERICSSON v. UNILOC
`Ex. 1023 / Page 14 of 21
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`7
`time frames, i.e., channel 510, for its Service traffic, i.e.,
`circuit Switched or packet data, transmissions.
`Should more than one subscriber respond to the same poll
`message from a base Station with respective resource request
`message transmissions, a collision occurs. In this case, the
`base Station generally does not respond to any Subscriber
`involved in the collision. The Subsequent lack of response
`from the base Station, i.e., no resource acknowledge message
`transmitted to any subscriber involved in the collision,
`causes the involved Subscribers to back off for a calculated
`time interval, before again attempting to acquire a connec
`tion link, i.e., one or more time slots, on a base Station.
`In a presently preferred embodiment, each Subscriber that
`feels it has been involved in a collision delays a random
`number of milliseconds before resuming the Search for a
`time slot in which a poll message is transmitted from a base
`Station. Determination of a collision delay time for a Sub
`Scriber takes into consideration the number of previous
`resource request message transmission attempts the respec
`tive Subscriber has made for the pending call. In a presently
`preferred embodiment, if any subscriber's number of
`resource request message transmission attempts for a respec
`tive pending call exceeds a specific, configurable, number of
`attempts, the Subscriber considers the respective pending
`call blocked, and drops it.
`In an exemplary Subscriber collision Scenario, as depicted
`in FIG. 6, a first Subscriber has a call become pending at time
`slot 605 of time frame 601. A second Subscriber has a call
`become pending at time slot 606 of time frame 602. At time
`slot 607 of time frame 602 a base station transmits a poll
`message 620, indicating a Subscriber may transmit a
`resource request message in time slot 608. Both the first and
`Second SubscriberS receive the poll message 620, and, thus,
`transmit respective resource request messages 621 and 622
`in time slot 608 of time frame 602, resulting in a collision.
`The first Subscriber backs off until time slot 609 of time
`frame 603, while the second Subscriber backs off until time
`slot 610 of time frame 604.
`The base Station transmits a Second poll message 623 in
`time slot 611 of time frame 604, indicating a subscriber may
`transmit a resource request message in time slot 612. The
`first Subscriber receives the poll message 623 because it has
`been listening for one since time slot 609 of the previous
`time frame 603. The second Subscriber, however, does not
`receive the poll message 623 because it does not begin to
`listen for any poll message until time slot 610 of time frame
`604.
`The first Subscriber, having received the poll message
`623, transmits a resource request message 624 for its respec
`tive pending call in time slot 612 of time frame 604. Because
`there is no other Subscriber transmitting a resource request
`message in this time frame/time slot, no collision occurs on
`the first Subscriber's Second attempt at a resource request
`message transmission to the base Station.
`Subscriber-originated traffic, circuit Switched or packet
`data, cannot be transmitted until the respective Subscriber
`Successfully transmits a resource request message in
`response to a poll message transmission from a base Station.
`Consequently, a portion of a base Station's time slots must
`be allocated for the transmission of poll messages if
`Subscriber-originated traffic is to be Supported.
`If a Subscriber does not receive a poll message from a base
`Station, it cannot begin a random acceSS Signalling Sequence
`to acquire a connection link on a base Station. In this case,
`in a presently preferred embodiment, after a Specified
`amount of time, the Subscriber deems its respective pending
`call blocked, and drops its.
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`Also, as previously indicated, if a Subscriber does not
`receive a response to its resource request message transmis
`Sion to a base Station, it assumes a collision has occurred. In
`this case, the Subscriber backs off for a calculated time
`interval, and then begins anew the random access Signalling
`Sequence. If the Subscriber is unsuccessful in receiving a
`base Station response after a predefined number of random
`acceSS Signalling Sequence attempts, it deems its respective
`pending call blocked, and drops it.
`In the prior art, if a Server System Successfully r