(12) United States Patent
`Barnett
`
`USOO621.6009B1
`(10) Patent No.:
`US 6,216,009 B1
`(45) Date of Patent:
`Apr. 10, 2001
`
`(54) METHOD AND APPARATUS FOR
`RESOLVING MULTIPLE CALL ACCESSES
`NAWIRELESS COMMUNICATION
`SYSTEM
`
`(*) Notice:
`
`(75) Inventor: Charles Barnett, Sterling, VA (US)
`(73) Assignee: Hughes Electronics Corporation, El
`Segundo, CA (US)
`-
`0
`Subject to any class the st & tly
`patent is extended or adjusted under
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 08/838,586
`(22) Filed:
`Apr. 10, 1997
`(51)
`
`7
`
`:
`
`9/1994 Buchenhorner ...................... 455/450
`5,345,596
`10/1994 Herold et al. ........................ 455/510
`5,355,516
`3/1995 Patsiokas et al. .................... 455/515
`5,396,648
`5,559,866 * 9/1996 O'Neill ...........
`... 455/447
`5,561,847
`10/1996 Kataoka ..............
`... 455/509
`5,613,208
`3/1997 Blackman et al. ................... 455/434
`5,687,171
`11/1997 Shin et al. ........................... 455/509
`5,946,612
`8/1999 Johansson ............................ 455/446
`* cited by examiner
`Primary Examiner Dwayne D. Bost
`Assistant Examiner-Quochien Vuong
`(74) Attorney, Agent, or Firm-John T. Whelan; Michael
`W. Sales
`ABSTRACT
`(57)
`A base transceiver station has a signal strength receiver and
`is capable of transmitting a directed retry Signal. A processor
`
`51
`
`Int. C. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - HO4B 7/00
`
`COnnectS to the Signal Strength receiver and compares
`
`455/510; 455/515; 455/453
`(52) U.S. Cl. ..................
`(58) Field of Search ..................................... 455/510,515,
`455/517,434, 424, 439, 450, 509, 522,
`447, 446, 453, 513, 514, 437
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`3/1979 Frenkiel ............................... 455/447
`4,144,411
`6/1987 Brody et al. ..
`... 455/453
`4,670,899
`5,203,011 * 4/1993 Bane et al.....
`... 455/510
`5,293,641
`3/1994 Kallin et al. ......................... 455/510
`
`received signal Strength to a predefined threshold. The
`processor causes the base transceiver Station to Send the
`directed retry Signal if the received signal Strength is leSS
`than the predefined threshold. A method is provided where
`a characteristic of a signal received at a base transceiver
`Station is measured and compared to a predefined threshold.
`A directed retry is Sent if the Signal characteristic is less than
`the predefined threshold, and a communication channel is
`established if a response to the directed retry is received at
`the base transceiver Station.
`
`20 Claims, 2 Drawing Sheets
`
`RECEIVE
`REQUEST FOR
`ACCESS
`
`IOO
`
`O2
`
`DETERMINE
`SIGNAL
`STRENGTH
`
`
`
`IO6
`
`
`
`
`
`SIGNAL
`COMPARISON
`
`BELOW
`THRESHOLD
`
`DRECTED
`RETRY
`
`
`
`
`
`
`
`ABOVE
`THRESHOLD
`
`2
`
`
`
`ESTABLISH
`coMMUNICATION RECEIVED
`CHANNEL
`
`NOT
`RECEIVED
`CANCEL
`REQUEST
`
`
`
`IO
`
`IPR2020-00038
`MM EX1010, Page 1
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`ERICSSON v. UNILOC
`Ex. 1039 / Page 1 of 7
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`

`

`U. S. Patent
`U.S. Patent
`
`Apr. 10, 2001
`Apr. 10, 2001
`
`Sheet 1 of 2
`Sheet 1 of 2
`
`US 6,216,009 BÍ
`US 6,216,009 B1
`
`
`
`FIG. I
`FG.
`
`PSTN
`PSTN
`
`14
`
`MSC
`
`OTHER
`MSC
`
`16-、一
`
`OMC
`
`20
`
`-BIS
`
`BTS
`
`BTS
`
`BSC
`
`BSC
`
`18
`MTSO
`
`22
`
`Î
`
`zi□［스놓。，
`FIG. 2
`TO MSC< E1 LINES, D < T1 LINES DTO BTSs
`
`TO MSC
`
`<
`
`El LINES
`
`><
`
`T1 LINES
`
`>
`
`TO BTSs
`
`4O
`40
`
`42
`42
`
`rZQ VME BUS
`(38 VME BUS
`z~30
`.• . CAP-5
`CAP-1
`BSC LAN
`
`STM-1 • • • STM-21
`
`CCP-1 ••• CCP-4
`32 —乂
`
`36
`
`GRP-1
`34 y
`
`GRP-2
`BSC
`
`FIG.3
`거
`42
`C T LINE D CFM
`< T1 LINE
`TO/FROM
`TO/ FROM
`BSC
`BSC
`20
`2O
`
`CFM
`
`
`
`
`
`BTS
`
`T1 BUS
`
`50
`
`BTS LAN ^52
`
`CU-1
`
`CU-2
`
`CU-30
`
`18
`
`RF
`
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`

`

`U.S. Patent
`
`Apr. 10, 2001
`
`Sheet 2 of 2
`
`US 6,216,009 B1
`
`FIG 4
`
`
`
`RECEIVE
`REQUEST FOR
`ACCESS
`
`IOO
`
`O2
`
`
`
`DETERMINE
`SIGNAL
`STRENGTH
`
`
`
`O4
`
`IO
`6
`
`
`
`
`
`SIGNAL
`COMPARISON
`
`BELOW
`THRESHOLD
`
`
`
`DIRECTED
`RETRY
`
`
`
`ABOVE
`THRESHOLD
`
`
`
`2
`
`ESTABLISH
`COMMUNICATION RECEIVED
`CHANNEL
`
`O8
`
`
`
`NOT
`RECEIVED
`CANCEL
`REQUEST
`
`O
`
`IPR2020-00038
`MM EX1010, Page 3
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`ERICSSON v. UNILOC
`Ex. 1039 / Page 3 of 7
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`

`

`1
`METHOD AND APPARATUS FOR
`RESOLVING MULTIPLE CALL ACCESSES
`NAWIRELESS COMMUNICATION
`SYSTEM
`
`BACKGROUND OF THE INVENTION
`The present invention relates to wireleSS communications,
`and more particularly to a method and apparatus for pro
`Viding access in a cellular communication System.
`Wireless mobile telecommunications systems utilize
`radio signals to exchange information between base trans
`ceiver Stations and mobile Subscribers. Each base trans
`ceiver Station transmits from an antenna throughout a pre
`determined area referred to as a cell. In order to provide
`Service to mobile Subscribers over a particular geographic
`region, many cells are positioned over the region or cover
`age area.
`The Service area of a cellular communication System is
`usually divided into cells of various sizes. Within each cell,
`a plurality of frequencies are allocated to communicate with
`a mobile Subscriber. Each cell usually operates on a different
`Subset of frequencies than neighboring cells to minimize the
`density of the used spectrum in a particular geographic area.
`Because the frequency band allocated for telecommuni
`cations is limited, cellular Systems may reuse the same
`frequencies at other cells. Reuse of the same frequencies
`may cause a mobile Subscriber to access the cellular System
`at a number of cells having the same channel and digital
`color code. When a mobile subscriber accesses multiple
`cells, the call may be rejected or the mobile Subscriber may
`receive a busy Signal. Furthermore, multiple accesses usu
`ally result in resources being unnecessarily allocated to
`Support “phantom' calls.
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`SUMMARY OF THE INVENTION
`The present invention provides an apparatus and method
`for resolving multiple call accesses in a cellular System. The
`present invention prevents a mobile Subscriber from access
`ing the System at multiple cells. In one aspect of the
`invention, a base transceiver Station is provided. The base
`transceiver Station has a Signal Strength receiver and is
`capable of transmitting a directed retry Signal. A processor
`connects to the Signal Strength receiver and compares a
`received signal Strength to a predefined threshold. The
`processor causes the base transceiver Station to Send the
`directed retry Signal if the received signal Strength is leSS
`than the predefined threshold.
`In another aspect of the invention, a characteristic of a
`Signal received at a base transceiver Station is measured and
`compared to a predefined threshold. A directed retry is sent
`if the Signal characteristic is less than the predefined
`threshold, and a communication channel is established if a
`response to the directed retry is received at the base trans
`ceiver Station.
`In another aspect of the invention, a cellular System
`capable of resolving multiple cell acceSS requests is
`provided, comprising at least a first and Second base trans
`ceiver Station. Each base transceiver Station has a signal
`Strength receiver and a base Station controller. The base
`Station controllers have received signal Strength thresholds.
`A first request for access Signal is received at both base
`transceiver Stations. The base transceiver Stations both mea
`Sure the Signal Strength of the first request for access Signal
`and the Signal Strength at the first base transceiver Station is
`below the received signal strength threshold for that base
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`US 6,216,009 B1
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`2
`transceiver Station. The first base transceiver Station Sends a
`directed retry Signal. A communication channel with the first
`base transceiver Station is established if a response to the
`directed retry is received by the first base transceiver Station.
`In yet another aspect of the invention, a first request for
`acceSS Signal is received at both a first and Second base
`transceiver Station. The first base transceiver Station trans
`mits a directed retry Signal if the first signal Strength of the
`first request for access is below a first received signal
`Strength threshold, and the Second base transceiver Station
`establishes a communication channel if the Second Signal
`Strength of the first request for access is above a Second
`received signal Strength threshold.
`It is to be understood that both the foregoing general
`description and the following detailed description are exem
`plary and explanatory and are intended to provide further
`explanation of the invention as claimed.
`The invention, together with further objects and attendant
`advantages, will best be understood by reference to the
`following detailed description of the presently preferred
`embodiment of the invention, taken in conjunction with the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a digital cellular network;
`FIG. 2 is a block diagram of the base station controller of
`FIG. 1;
`FIG. 3 is a block diagram of the base transceiver station
`of FIG. 2; and
`FIG. 4 is a block diagram of a Scheme for resolving
`multiple call accesses in a cellular System in accordance
`with the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`Referring now to the drawings, and more particularly to
`FIG. 1, a preferred embodiment of a cellular network 10 is
`illustrated. The cellular network 10 may be utilized to
`implement the method and apparatus of the present inven
`tion. The cellular network 10 preferably determines the
`Strength of an access request by a mobile Subscriber. When
`the access request is less than a predefined threshold, a direct
`retry is sent to the mobile subscriber. If the mobile Sub
`Scriber responds, Service is provided. The direct retry allows
`the cellular System to perform more efficiently by reducing
`the amount of resources for Setting up a call.
`In a preferred embodiment, the cellular network 10
`includes at least one base transceiver station (BTS) 20, at
`least one mobile Subscriber 22, and a mobile telephone
`switching office (MTSO) 12. The MTSO 12 includes a
`mobile Switching center (MSC) 14, an operations and main
`tenance center (OMC) 16, and a plurality of base station
`controllers (BSCs) 18. The MTSO 12 is in communication
`with a terrestrial telephony carrier, Such as the public
`switched telephone network (PSTN), and may also commu
`nicate with Satellite Systems and other mobile Switching
`CenterS.
`The MSC 14 is in communication with the OMC 16, and
`is also in communication with at least one BSC 18. The BSC
`18 is connected through a communication channel to one or
`more of the base transceiver stations (BTS) 20. Each BTS 20
`includes an antenna (not shown) and defines an individual
`cell of the cellular network 10. Each BTS 20 includes
`hardware and Software required to communicate over the
`channels of the cellular system 10. Each BTS also includes
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`3
`a plurality of individual Scanning receivers for Scanning
`Selected traffic channels and includes digital multiplex
`equipment for transmission of audio traffic to its associated
`BSC 18.
`A mobile Subscriber 22 may communicate over a control
`channel with a BTS of a particular cell in which it is located.
`The mobile subscriber 22 is preferably either a hand held
`phone or a vehicle mounted unit. It is also contemplated that
`the mobile subscriber 22 may include fixed terminals. The
`mobile Subscriber 22 may also include a Scanning receiver
`for Scanning Selected channels of the Serving and neighbor
`ing cell.
`A call may be originated from the mobile Subscriber 22 by
`transmitting initialization data over the control channel
`assigned to the BTS 20 serving the mobile Subscriber 22.
`Preferably, control channel Signals are received in a time slot
`within a predetermined frequency assigned to the cell. From
`the BTS 20, the call is routed to the BSC 18, and then to the
`MSC 14. From the MSC 14, the call is routed outside of the
`MTSO 12 to either another MSC or the PSTN. Thereafter,
`a communication channel is established through the entire
`digital cellular network 10, and the mobile subscriber 22
`may communicate over the established communication
`channel. The communication channel comprises a pair of
`frequencies. The Slot pair of frequencies for a communica
`tions channel may be in a time division multiple acceSS
`format.
`The mobile Subscriber 22 may also receive calls originat
`ing from a terrestrial facility, such as the PSTN or another
`MSC, by connecting the call through the system 10 at the
`MSC 14. From the MSC 14, the call is routed to one of the
`BSCs 18. The BSC 18 then sends a message to the mobile
`subscriber 22 via the appropriate BTS 20 to announce the
`incoming call. After the mobile Subscriber 22 responds to the
`page from the BTS 20, a communication channel is estab
`lished.
`Referring to FIG. 2, a preferred component layout for the
`BSC 18 is illustrated. The BSC 18 preferably implements
`audio compression/decompression and handles call
`establishment, disconnect, and handoff procedures. The
`BSC 18 also allocates system resources of the BTS 18
`associated with a particular BSC 18. The BSC 18 commu
`nicates with the MSC 14 over E 1 transmission lines 40, and
`communicates with the BTS 20 over T1 transmission lines
`42. The BSC 18 also communicates with the OMC 16.
`Preferably, the BSC 18 has several processors including a
`global resource processor (GRP) 34, a call control processor
`(CCP) 32, and a channel access processor (CAP) 30. The
`BSC 18 also includes a BSC local area network (LAN) 36
`and a VME bus 38. The VME bus 38 is used to communicate
`between the various CAPs 30, while the BSC LAN 36
`allows communication between the CCPs 32.
`The CAP 30, CCP 32, and GRP 34 shown in FIG. 2 are
`preferably 32 bit microprocessors, such as an Intel 960. The
`processors (30, 32, and 34) are preferably operated with a
`multi-tasking Software operating System Such as UNIX or
`the VX WORKS operating system available from Wind
`River Systems. The processors (30, 32, and 34) are also
`usually programmed with application Software and commu
`nication software. Preferably, the Software is written in C
`language or another conventional high level programming
`language. Each of the processors (30, 32, and 34) commu
`nicates with the other processors using either the BSC LAN
`36 or the VME bus 38. Preferably, the processors (30, 32,
`and 34) communicate with each other using a network
`configuration and communication techniques well-known in
`the art.
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`Calls originating from the mobile subscriber 22 are
`received over the T1 line 42 and processed by the GRP 34.
`The GRP34 then determines, based on loading conditions,
`which CCP32 should handle the call. The call is then handed
`off to the selected CCP.32 assigned to the call. The CCP32
`then determines which CAP 30 should be used. In the case
`of a call originating from the PSTN or another MSC, the call
`is received by the MSC 14 and is then routed to a GRP 34
`over an E1 line 40. The GRP34 allocates a CCP32, which
`then allocates a CAP 30.
`Referring to FIG. 3, a block diagram of a preferred
`component layout for the BTS 20 is illustrated. The BTS 20
`communicates with the BSC 18 over T1 communication
`lines 42. A channel unit (CU) 50 receives data from the T1
`lines 42 and generates a signal to be sent over a communi
`cation link 52. The communication link 52 is used to
`communicate with the mobile subscriber 22 in a cell (not
`shown) via a radio frequency signal transmission.
`The CU 50 is preferably either an analog channel unit, a
`dual mode channel unit, or a digital channel unit. Each CU
`50 contains a plurality of communication channels available
`for transmissions. These channels may be analog control
`channels, analog traffic channels, digital traffic channels,
`analog Scanning receiver channels, or digital Scanning
`receiver channels. The control channels are used to com
`municate between the BTS 20 and the mobile unit 22 before
`the mobile unit 22 has been assigned a voice channel for
`communication. An analog traffic channel may be used for
`voice communication between the BTS 20 and the mobile
`Subscriber 22. Each analog traffic channel is associated with
`a specific predefined frequency used for radio transmission
`over the communication link 52. The allocation of frequen
`cies to traffic channels is defined in detail by U.S. Cellular
`Standard IS-54. Alternatively, in a digital communication
`System, a digital traffic channel may be used instead of the
`analog traffic channel.
`Each CU 50 includes its own processor, such as an Intel
`960 32-bit microprocessor unit, along with a hardware
`circuit for transmitting information over each of the chan
`nels. Each CU 50 communicates with other CUS 50 in the
`Same BTS 20 over the BTS LAN 36.
`In a preferred embodiment, the mobile subscriber 22
`employs a time division multiple access (TDMA) method of
`communicating digital information to the BTS 20. The
`formatted information transmitted from the mobile Sub
`scriber 22 to the BTS 20 is arranged in frames having time
`slots. Preferably, there are six time slots. The mobile Sub
`scriber 22 broadcasts information onto one of the time slots
`in transmission bursts. The transmission bursts are Synchro
`nized to correspond with the appropriate time slot reserved
`for the particular transmission. The transmission bursts are
`Separated by an inter-burst guard time to avoid interference
`between bursts.
`The cells of the cellular network are preferably color
`coded by a two bit symbol, called the digital color code
`(DCC), assigned to the control channels. The DCC assists
`the cellular network to manage frequency or time slot
`assignment of clusters of cells.
`Referring to FIG. 4, a preferred embodiment of a scheme
`for accessing a cellular communication System is shown.
`When a call is originated by the mobile Subscriber 22, it will
`Send out a signal Over a particular control channel. The
`Signal may be received by multiple base Stations having the
`same channel and DCC 100. In order for the appropriate cell
`of the system to be assigned to the mobile Subscriber 22, the
`BTS 20 of the cell determines 102 the strength of the signal
`transmitted from the mobile Subscriber 22.
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`S
`The BTS 20 is preferably equipped with a signal strength
`receiver to measure the Signal Strength of a mobile Sub
`scriber. The signal strength of the mobile subscriber 22 is
`compared to a predetermined threshold value 104.
`Preferably, the threshold value is above a value determined
`from the size of the cell and the co-channel access level. If
`the signal is below the predetermined threshold value, the
`BSC 18 requests (106) the mobile subscriber 22 to again
`access the BSC 18. This request is referred to as a directed
`retry. If the mobile subscriber 22 does not respond 108 to the
`directed retry message sent from the BSC 18, the commu
`nication access request will be canceled 110. For the mobile
`subscriber 22 to respond, the mobile Subscriber 22 will send
`a signal to the BSC 18. Preferably, the signal will contain
`information indicating that the mobile subscriber 22 previ
`ously attempted to access the BSC 18. After the directed
`retry and a response 108, the BSC 18 will then process the
`call and a communication channel will be set up (112) at the
`BTS 20.
`The present invention preferably prevents a mobile Sub
`Scriber 22 from accessing the cellular communication SyS
`tem in multiple cells. For example, if a mobile subscriber 22
`attempts to originate a call and the call is received by
`multiple cells with the same channel and DCC, the BTS 20
`of each cell will compare the Signal Strength from the mobile
`subscriber 22 with the predetermined threshold value. In one
`of the cells, the signal from the mobile subscriber 22 will
`usually be above the predetermined threshold value and
`access will be allowed by the BTS 20. In the other cells, the
`signal from the mobile subscriber will usually be below the
`predetermined threshold valve and a directed retry will be
`sent by the BTS 20. However, the mobile subscriber will not
`respond because the mobile subscriber will be tuned to BTS
`20 of the cell where the signal was greater than the prede
`termined value.
`Although the present invention has been described in
`detail by way of illustration and example, it should be
`understood that a wide range of changes and modifications
`can be made to the preferred embodiment described above
`without departing in any way from the Scope and Spirit of the
`invention. Furthermore, the described embodiments are to
`be considered in all respects only as illustrative and not
`restrictive, and the Scope of the invention is, therefore,
`indicated by the appended claims rather than the foregoing
`description.
`What is claimed is:
`1. A method of resolving multiple cell accesses in a
`cellular System comprising the Steps of:
`receiving a signal at a base transceiver Station;
`measuring a characteristic of the Signal;
`comparing the Signal characteristic to a predefined thresh
`old associated with cell size and co-channel acceSS
`level;
`Sending a request to Send another Signal if the Signal
`characteristic is less than the predefined threshold; and
`automatically establishing a communication channel if a
`response to the request is received at the base trans
`ceiver Station.
`2. The method of claim 1 further comprising the step of
`establishing a communication channel if the Signal charac
`teristic is greater than the predefined threshold.
`3. The method of claim 1 wherein the step of receiving a
`Signal comprises receiving a request for a communication
`channel Signal.
`4. The method of claim 3 further comprising the step of
`canceling the request for the communication channel if the
`response is not received at the base transceiver Station.
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`5. The method of claim 1 wherein the step of automati
`cally establishing a communication channel if a response is
`received at the base transceiver Station comprises automati
`cally establishing the communication channel if the response
`is received at the base transceiver Station, Said response
`indicating that the Signal was previously sent.
`6. The method of claim 1 wherein the step of receiving a
`Signal at a base transceiver Station compriseS receiving the
`Signal over a control channel at the base transceiver Station,
`the base transceiver having a specific identification code.
`7. The method of claim 1 wherein the step of establishing
`a communication channel comprises establishing an analog
`transmission frequency pair.
`8. The method of claim 1 wherein the step of measuring
`a characteristic of the Signal comprises measuring the
`received signal Strength.
`9. An apparatus for resolving multiple cell accesses in a
`cellular communication System comprising:
`a base transceiver Station comprising a signal Strength
`receiver, the base transceiver Station capable of trans
`mitting a request to Send another signal;
`a processor operatively connected to the Signal Strength
`receiver, the processor comparing a received signal
`Strength to a predefined threshold associated with cell
`Size and co-channel acceSS level and causing the base
`Station transceiver to Send the request if the received
`Signal Strength is less than the predefined threshold; and
`a communication channel which is automatically estab
`lished if the base transceiver Station receives a response
`to the request.
`10. The apparatus of claim 9 wherein the communication
`channel comprises an analog frequency pair in a TDMA
`System.
`11. The apparatus of claim 9 wherein the response com
`prises a Second request for access and data indicating a
`previous request for acceSS.
`12. The apparatus of claim 9 wherein the received signal
`Strength comprises a measurement of a first request for
`acceSS received on a control channel.
`13. The apparatus of claim 12 wherein the request to Send
`another signal comprises an instruction to make a Second
`request for access.
`14. The apparatus of claim 13 wherein the instruction to
`make the Second request for access comprises a signal
`addressed to a mobile unit that made the first request for
`CCCSS.
`15. The apparatus of claim 14 wherein the response
`comprises the Second request for access.
`16. The apparatus of claim 9 wherein the processor
`comprises a base Station controller.
`17. A cellular system capable of resolving multiple cell
`access requests comprising:
`at least a first and Second base transceiver Station, each
`base transceiver Station having a signal Strength
`receiver;
`at least a first and Second base Station controller opera
`tively connected to the first and Second base transceiver
`Stations, respectively, the first and Second base Station
`controllers having a first and Second received signal
`Strength threshold associated with cell Size and
`co-channel access level, respectively;
`a first request for acceSS Signal received at both the first
`and Second base transceiver Stations,
`first and Second Signal Strength of the first request for
`acceSS Signal at the first and Second base transceiver
`Station, respectively, the first signal Strength being
`below the firs received signal threshold;
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`ERICSSON v. UNILOC
`Ex. 1039 / Page 6 of 7
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`US 6,216,009 B1
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`7
`a request to Send another Signal communicated by the first
`base transceiver Station; and
`a communication channel with the first base transceiver
`Station which is automatically established if a response
`to the request to Send another Signal is received by the
`first base transceiver Station.
`18. The apparatus of claim 17 wherein the first and second
`base transceiver Stations comprise the identification code.
`19. A method of resolving multiple cell acceSS requests in
`a cellular communication System comprising the Steps of:
`receiving a first request for access Signal at both a first and
`Second base transceiver Station;
`transmitting a request to Send another Signal from the first
`base transceiver Station if a first signal Strength of the
`first request for access at the first base transceiver
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`8
`Station comprises a level below a first received signal
`Strength threshold associated with cell Size and
`co-channel access level; and
`automatically establishing a communication channel at
`the Second base transceiver Station if a Second Signal
`Strength of the first request for acceSS at the Second base
`transceiver Station comprises a level above a Second
`received signal Strength threshold associated with cell
`size.
`20. The method of claim 19 comprising the further step of
`establishing a communication channel at the first base
`transceiver Station upon receipt of a response to the request
`to Send another signal.
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`k
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`k
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`IPR2020-00038
`MM EX1010, Page 7
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`ERICSSON v. UNILOC
`Ex. 1039 / Page 7 of 7
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