US007570929B1
`
`United States Patent
`(12)
`(10) Patent No.:
`US 7,570,929 B1
`Trompower
`(45) Date of Patent:
`Aug. 4, 2009
`
`
`(54)
`
`802.11 NETWORKS USING DYNAMIC
`POWER CONTROL FOR RF TRANSMISSION
`
`(75)
`
`Inventor: Michael L. Trompower, Navarre, OH
`(US)
`(3) Assignee: Symbol TechnologIn, Holivil,
`NY (US)
`.
`.
`.
`co
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`5,706,428 A *
`LI998 Boeretal. oo. 370/342
`5,708,681 A
`375/297
`1/1998 Malkemesetal.
`
`5,768,695 A *
`6/1998 Fischeret al.
`.....
`-- 455/127
`
`
`5,982,807 A *
`++ 375/146
`.........
`11/1999 Snell
`
`5,987,011 A
`we. 370/331
`11/1999 Toh...
`5,987,033 A
`.....
`.. 370/445
`11/1999 Boeretal.
`
`«30023 BLY SOQ001 Manat aorc: SO
`* cited by examiner
`
`Primary Examiner—Melady Mehrpour
`(74) Attorney, Agent, or Firm—Amin, Turocy & Calvin, LLP
`
`(57)
`
`ABSTRACT
`
`
`
`A system and methodis provided for adjusting transmission
`powerof different portions of a data packet. The system and
`
`methodis especially useful when utilizing the IEEE 802.11
`standardprotocoldueto the varying transmissiondata rates of
`a packet. A IEFE 802.11 packet includes a preambleportion,
`a headerportion and a data portion. The preamble portion has
`a data rate of 1 Mbps, the headerhasa data rate of 1 or 2 Mbps
`and the data portion hasa data rate of 1, 2, 5.5 or 11 Mbps. At
`a given fixed powerlevel, a transmission at a higher data rate
`has a lowertransmission range than a transmission at a lower
`data rate. Therefore, the present invention provides for a
`system and method that adjusts the powerlevel of different
`portionsof a data packet, so that the entire data packethas a
`more uniform range. This eliminates the need for components
`in the system receiving a preamble portion of a transmission
`at higher ranges to remain idle during transmission of an
`entire frame. The system and method can beapplied to both
`access points and mobile units in a cellular communications
`system.
`
`
`
`(21) Appl. No.: 09/483,399
`
`(22) Filed:
`
`Jan. 14, 2000
`
`(51)
`
`Int. CL.
`(2006.01)
`HO4B 1/04
`(52) US. CL.ec cecnsecsesereneneeags 455/114.3
`(58) Field of Classification Search.
`................. 455/114,
`455/91, 522, 127, 575, 64, 114.3, 574, 127.1,
`455/127.5, 13.4; 375/297, 296, 295; 370/318,
`370/319, 321, 465, 337, 347, 338; 709/229,
`709/240
`See application file for complete search history.
`,
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`*
`:
`
`AAA
`
`AAA
`
`5,289,459
`2/1994 Brownlie wc. eee 370/17
`5:333,175
`7/1994 Ariyavisilakul elal.
`....... 338
`
`
`3,450,616
`SIL99S ROM vrcrerreens
`yboe
`5,461,627 A
`10/1995 Rypinski
`.........
`
`5,553,316
`9/1996 Diepstraten et al.
`.
`« 455/69
`
`5,572,528
`11/1996 Sheun .........
`370/85.13
`
`5,636,140A* 6/1997 Teeetal. oe. 364/514 31 Claims, 10 Drawing Sheets
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`Page 1 of 19
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`SAMSUNG EXHIBIT 1033
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`SAMSUNG EXHIBIT 1033
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`U.S. Patent
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`Aug. 4, 2009
`
`Sheet 1 of 10
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`US 7,570,929 B1
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`LINA
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`Page 2 of 19
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`U.S. Patent
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`Aug. 4, 2009
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`Sheet 2 of 10
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`US 7,570,929 B1
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`Page 3 of 19
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`U.S. Patent
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`Aug. 4, 2009
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`Sheet 3 of 10
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`US 7,570,929 B1
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`U.S. Patent
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`Aug.4, 2009
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`Sheet 4 of 10
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`US 7,570,929 B1
`
`POWER
`MILLIWATTS
`
`100
`
`8
`
`PLCP
`PREAMBLE
`
`|PLCP HEADER
`
`PSDU (DATA PORTION)
`
`Fig. 4a
`
`x 84
`
`
`
`”
`
`FEET
`
`2000
`
`125
`
`0
`
`Fig. 4b
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`Page 5 of 19
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`U.S. Patent
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`Aug.4, 2009
`
`Sheet 5 of 10
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`US 7,570,929 B1
`
`ye
`
`PLCP
`
`reeiae[rortearen]—renvioararonmon
`Fig. 4c
`
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`x. 88
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`
`Fig. 4d
`
`POWER
`
`WATTS
`
`100
`
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`
`FEET
`
`2000
`
`125
`
`°
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`Page 6 of 19
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`U.S. Patent
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`Aug.4, 2009
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`Sheet6 of 10
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`US 7,570,929 B1
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`CIRCUIT
`
`112
`
`62
`ae]CONTROL
`
`MEMORY
`
`
`
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`100
`
`XCEIVER
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`aaCONTROL
`
`
` MEMORY 98,
`
`XCEIVER
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`Page 7 of 19
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`U.S. Patent
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`Aug. 4, 2009
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`Sheet 7 of 10
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`US 7,570,929 B1
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`/AINSNVELL
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`Page 8 of 19
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`U.S. Patent
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`Aug. 4, 2009
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`Sheet 8 of 10
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`US 7,570,929 B1
`
`TRANSMIT/
`
`RECEIVE
`
`SWITCH
`
`Fig.7
`
`TRANSMITTER
`
`RECEIVER
`
` 98
`
`in
`
`PROCESSOR
`
`TRANSMIT
`
`POWER
`
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`
`126
`
`MODULE
`
`
`
`POWERCONTROL
`
`Page 9 of 19
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`Page 9 of 19
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`

`

`U.S. Patent
`
`Aug.4, 2009
`
`Sheet 9 of 10
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`US 7,570,929 B1
`
`
`ACCESS POINT SYSTEM RECEIVES
`REGISTRATION REQUEST FROM MOBILE
`COMMUNICATION UNIT
`
`
`
`
`ACCESS POINT SYSTEM EVALUATES THE
`TRANSMISSION POWER OF THE REQUEST
`
`
`
`
`
`PROCESSOR CALCULATES DESIRED
`
`RESPONSE RANGE OF TRANSMISSION
`
`160
`
`170
`
` 150
`
`
`
`
`
`
`PROCESSOR CONFIGURES DATA POWER
`WORDS
`
`
`
`180
`
`190
`
`200
`
`210
`
`220
`
`PROCESSOR CONFIGURES DATA PACKET FOR
`TRANSMISSION
`
`
`
`
`
`
`PROCESSOR DOWLOADS POWER DATA TO
`D/A CONVERTER FOR BEGINNING OF
`TRANSMISSION
`
`
`ACCESS POINT BEGINS TRANSMISSION OF
`PACKET
`
`
`
`
`
`
`PROCESSOR DOWNLOADS N NUMBER OF
`POWER DATA WORDS DURING
`TRANSMISSION OF PACKET BASED ON N
`
`NUMBER OF DATA RATES
`Fig. 8
`
`Page 10 of 19
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`Page 10 of 19
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`

`

`U.S. Patent
`
`Aug.4, 2009
`
`Sheet 10 of 10
`
`US 7,570,929 B1
`
`
`
`
`HOST SYSTEM TRANSMITS DESIRED RANGE
`INFORMATION TO EACH ACCESS POINT
`SYSTEM
`
`
`
`ACCESS POINT SYSTEM EVALUATES THE
`RANGE DATA OF THE HOST SYSTEM REQUEST
`
`
`
`
`
`PROCESSOR CALCULATES DESIRED
`RESPONSE RANGE OF TRANSMISSION
`
`PROCESSOR CONFIGURES DATA POWER
`
`
`
`
`
`
`
` WORDS
`
`
`PROCESSOR CONFIGURES DATA PACKET FOR
`TRANSMISSION
`
`
`
`
`
`
`
`
`250
`
`260
`
`270
`
`280
`
`290
`
`300
`
`
`PROCESSOR DOWLOADS POWER DATA TO
`D/A CONVERTER FOR BEGINNING OF
`TRANSMISSION
`
`
`ACCESS POINT BEGINS TRANSMISSION OF
`PACKET
`
`PROCESSOR DOWNLOADS N NUMBER OF
`POWER DATA WORDS DURING
`TRANSMISSION OF PACKET BASED ON N
`NUMBER OF DATA RATES
`
`310
`
`320
`
`Fig. 9
`
`Page 11 of 19
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`Page 11 of 19
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`

`

`US 7,570,929 B1
`
`1
`802.11 NETWORKS USING DYNAMIC
`POWER CONTROL FOR RE TRANSMISSION
`
`TECHNICAL FIELD
`
`The present invention generally relates to communication
`systems, and in particular to a system and methodfor increas-
`ing throughput of a communication system.
`
`
`
`BACKGROUND OF THE INVENTION
`
`10
`
`Theuse of cellular communication systems having mobile
`devices which communicate with a hardwired network, such
`as a local area network (LAN) or a wide area network (WAN),
`has become widespread. Retail stores and warehouses, for
`example, may use cellular communications systems with
`mobile data terminals to track inventory and replenish stock.
`The transportation industry may use such systemsat large
`outdoor storage facilities to keep an accurate account of
`incoming and outgoing shipments. In manufacturing facili-
`ties, such systems are useful for tracking parts, completed
`products and defects. Such systemsare also utilized for cel-
`lular telephone communications to allow users with wireless
`telephones to roam across large geographical regions while
`retaining telephonic access. Paging networksalso may utilize
`cellular communications systems which cnable a user carry-
`ing a pocket sized pager to be paged anywhere within a
`geographic region.
`Atypical cellular communications system includes a num-
`berof fixed access points (also knownas basestations) inter-
`connected by a cable medium often referred to as a system
`backbone. Also included in many cellular communications
`systemsare intermediate access points whicharenotdirectly
`connected to the system backbone but otherwise perform
`manyof the same functionsasthe fixed access points.Inter-
`mediate access points, often referred to as wireless access
`points or basestations, increase the area within which access
`points connected to the system backbone can communicate
`with mobile devices.
`
`40
`
`45
`
`Associated with each access point is a geographic cell.The
`cell is a geographic area in which an access point has suffi-
`cient signal strength to transmit data and receive data froma
`mobile device such as a data terminal or telephone with an
`acceptable error rate. Typically, access points will be posi-
`tioned along the backbones such that the combinedcell area
`coverage from eachaccess point provides full coverage of a
`building orsite.
`Mobile devices such as telephones, pagers, personaldigital
`assistants (PDA’s), data terminals etc. are designed to be
`carried throughout the system from cell to cell. Each mobile 5
`device is capable of communicating with the system back-
`bonevia wireless communication between the mobile device
`and an access point to which the mobile deviceis registered.
`As the mobile device roams from one cell to another, the
`mobile device will typically deregister with the access point
`of the previouscell and register with the access point associ-
`ated with the new cell. In order to provide sufficient cell area
`coverage, access points(or the antennas associated with each
`access point) within the cellular communications system
`typically are distributed at
`separate physical
`locations
`throughoutan entire building or set of buildings.
`Recently a standard for wireless local area networks
`(WLANs) known as the IEEE 802.11 standard has been
`adopted and has gained acceptance among the industrial,
`scientific and medical communities. The IEEE 802.11 stan-
`
`dard for WLANsis a standard for systemsthat operate in the
`2,400-2,483.5 MHzindustrial, scientific and medical (ISM)
`
`Page 12 of 19
`
`2
`band. The ISM bandis available worldwide and allows unli-
`censed operation of spread spectrum systems. ‘The IEEE
`802.11 RF transmissions use multiple signaling schemes
`(modulations) at different data rates to deliver a single data
`packet between wireless systems. Current wireless imple-
`mentations employ a single power level for transmission ofan
`entire packet. As a result, different portions of the packet are
`capable of reception at different ranges. Therefore, default
`operation results in a longer preamble range as compared to
`the other portions of the frame. Once a preamble is correctly
`received by other access stations, they often need to remain
`off during an entire frame or frame exchange. This causes
`stations that are outside an intended transmission range to
`remain idle during the frame transmission thereby reducing
`the entire throughput of the system.
`An attempt has been madeto salve this problem by pro-
`viding multiple accessstationsat a single location operating
`on different frequencies. Ilowever, this requires that each
`station in a single location be different with respect to hard-
`ware and software required to operate the station. This has
`proven to be complicated and expensivein actual implemen-
`tation. In addition, there is typically only three non-overlap-
`ping channels available in such types of systems. Therefore,
`this solution does not overcome the problem withidle access
`stations when all three channels are operating. Furthermore,
`these transmissions along the three channels still do not guar-
`antee access points will not receive interference.
`Accordingly, there is a strong need in the art for a system
`and method that overcomesthe aforementioned problems.
`
`SUMMARYOF THE INVENTION
`
`Thepresent invention provides fora system and methodfor
`adjusting transmission powerlevel of different portions of a
`data packet. The system and methodis especially useful when
`utilizing the IEEE 802.11 standard protocol due to the vary-
`ing transmission data rates of a packet. An IEEE 802.11
`packet includes a preamble portion, a header portion and a
`data portion. The preamble portion typically hasa data rate of
`1 Mbps (Megabits per second), the header hasa data rate of1
`or 2 Mbpsand the data portion has a data rate of 1, 2,5.5 or 11
`Mbps. Ata givenfixed powerlevel, a transmissionat a higher
`data rate has a lower transmission range than a transmission at
`a lower data rate. Therefore, the present invention provides
`for a system and method that adjusts the power level of
`different portions of a data packet, so that the entire data
`packet has a more uniform range. This eliminates the need for
`components in the system receiving a preamble portion of a
`transmissionat the higher ranges to remain idle during trans-
`mission of an entire frame as is the standard in the TRFF
`802.11. Furthermore,
`the present
`invention allows
`for
`dynamic adjustment of the power transmissionlevel, so that
`range reductions can be implemented to mitigate interference
`problems and reduce battery consumption. The system and
`method can be applied to both access points and mobile units
`in acellular communications system.
`In accordance with one aspect of the invention, a commu-
`nication unit in a cellular communication system is provided.
`The unit includes a transmitter adapted to transmit data over
`an RF link and a power control module coupledto the trans-
`mitter. The power control moduleis adapted to receive a data
`packet havinga first portion and a secondportion and transmit
`the first portion at a first transmission power level and the
`second portionat a second transmission powerlevel.
`Another aspect of the invention relates to a method of
`transmitting a data packet in a cellular communication sys-
`tem. The method includes the steps of transmitting a first
`
`Page 12 of 19
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`

`

`US 7,570,929 B1
`
`4
`FIG.4dillustrates a graph of a range ofa transmission with
`respect to the power graph of FIG. 4c in accordance with the
`present invention:
`FIG.5aillustrates a block diagram of a hard wired access
`point system in accordance with the present invention;
`FIG. 56 illustrates a block diagram of a wireless access
`point system in accordance with the present invention;
`FIG.6 illustrates a detailed block schematic diagram ofthe
`RF section of the access point system of FIG. 5a in accor-
`dance with the present invention;
`FIG.7 illustrates a detailed block schematic diagramof an
`alternate embodiment of the RF section of the access point
`system of FIG. 5a in accordance with the present invention;
`FIG.8 is a flow diagram illustrating one particular mcth-
`odologyfor configuring the power contro] module in accor-
`dance with the present invention; and
`FIG. 9 is a flow diagram illustrating an alternate method-
`ology for configuring the power control module in accor-
`dance with the present invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`
`
`3
`portion of the data packetat a first transmission powerlevel
`and transmittmg a second portion of the data packet at a
`second transmission powerlevel.
`Anotheraspect ofthe present invention relates to an access
`point system in a cellular communication system utilizing an
`IELE 802.11 standard protocol. The system includesa trans-
`milter adapted to transmit data over an RF link and a power
`control module coupled to the transmitter. The power control
`module is adapted to receive a data packet having a PLCP
`preamble and PLCPheader portion and a data portion. The
`powercontrol module is also adapted to dynamically adjust
`the transmission powerof the packet during transmission of
`the packet, such that the PLCP preamble portion beginstrans-
`mitting at a first transmission powerlevel and the data portion
`begins transmitting at a second transmission powerlevel. The
`system further includes a processor coupled to the power
`adjustment module. The processor is adapted to provide
`power adjustment information to the power control module.
`Finally, the system includes a receiver coupledto the proces-
`sor. The receiver is adapted to receive data over an RF link.
`Turthermore, the access point system is coupled to a network.
`Yet another aspect of the present invention relates to a
`cellular communication system. The system includes means
`for transmitting a data packet having a first portion and a
`second portion and means for dynamically adjusting the
`transmission powerlevel, of the first portion with respect to
`the secondportion ofthe data packet coupledto the meansfor
`transmitting a data packet havinga first portion and a second
`portion.
`In yet another aspect of the present invention a signal
`transmitted over a wireless communication system is pro-
`vided. Thesignal includesa first portion transmitted ata first
`power level and a second portion transmitted at a second
`powerlevel.
`To the accomplishmentof the foregoing and related ends,
`the invention, then, comprises the features hereinafter fully
`described and particularly pointed out in the claims. The
`following description and the annexed drawingsset forth in
`detail certain illustrative embodiments of the invention.
`These embodiments are indicative, however, of but a few of
`the various ways in which theprinciples ofthe invention may
`be employed. Other advantages and novel features of the
`invention will become apparent from the following detailed
`description of the invention when considered in conjunction
`with the drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`45
`
`60
`
`The present invention will nowbe described with reference
`to the drawings. The present invention will be described with
`reference to a system and method for dynamically adjusting
`transmission power of different portions of a data packet
`transmitting at different data rates. It should be understood
`that the description of these aspects of the invention are
`merely illustrative and that they should not be taken in a
`limiting sense.
`Referring nowto FIG. 1, a cellular communication system
`50 illustrating an environment of the present invention is
`shown. The cellular communication system 50 includes a
`local area network (LAN) 52. The LAN or network backbone
`52 may be a hardwired data communication path made of
`twisted pair cable, shielded coaxial cable or fiber optic cable,
`for example, or may be wireless or partially wireless in
`nature. Coupled to the LAN 52 are a stationary communica-
`tion unit 53 and several access points 54. Only one access
`point 54, is shown hardwired to the network backbone 52,
`however, it is understood that more than one hardwired access
`points 54, may be physically connected to the network back-
`bone 52. The access points 54 maybe hardwiredto the net-
`work 52 such as access point 54, or may be wirelessly
`coupled to the backbone 52 such as access point 54,. Each
`access point serves as an entrance point through which wire-
`less communications may occur with the network backbone
`52. The wireless access point 54, may be employed to expand
`the effective communication range of the cellular communi-
`FIG.1 illustrates a system diagram of a network commu-
`cation system 50. As is conventional, each wireless access
`nication system in accordance with the present invention;
`point 54, associates itself, typically by registration, with
`
`FIG. 2 illustrates a protocol of a IEEE 802.11 standard data
`another access point or a host computer 60 coupled to the
`packet in accordance with the present invention;
`network backbone 52, whether hardwired or wireless, such
`that a link is formed betweenitself and other devices situated
`FIG.3 illustrates a graph of a range of a transmission for
`on the network backbone 52.
`different portions ofthe data packet ofFIG.2 at a given power
`level in accordance with the present invention;
`Eachaccess point 54 is capable ofwirelessly communicat-
`IG.4a illustrates a graph of a powerof a transmission for
`ing with other devices in the communication system 50 via
`different portions of the data packet of FIG. 2 at a reduced
`respective antennas commonlydenoted by reference numeral
`powerlevel for the PLCP preamble in accordance with the
`62. The antenna 62 for any particular device may be of any
`present invention;
`type suitable for use in a network cellular communication
`FIG.46 illustrates a graph ofa range ofa transmission with
`system, such as an omni-directional antenna, a yagi-type
`respect to the power graph of FIG. 4a in accordance with the
`antenna, etc. A geographic cell (not shown) associated with
`present invention;
`each access point 54 defines a region of coverage in which
`
`FIG.4c illustrates a graph of a powerofatransmission for successful wireless communication may occur. Depending
`different portions ofthe data packet of FIG.2 at an increased
`on the type of antenna 62 selected and output powerofthe
`powerlevel for the PLCP data portion in accordance withthe
`respective access point, the geographic cell may take one of
`present invention;
`several different forms and sizes. For example, the antenna 62
`
`
`
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`US 7,570,929 B1
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`6
`is complete because the access point will assume that the
`device transmitting the PLCP preambleis transmitting within
`their cell. However, the access point may not receive the
`actual data because the range of the data is much less than the
`range of the preamble. If an access point transmits the data
`portion 73 at 11 Mbps,all other access points within 2000feet
`of the access point will remain idle during the full transmis-
`sion, while only access points within 125 feet ofthe transmit-
`ting access point will be able to receive data. In some indoor
`systems, all access points are within 2000 feet from one
`another and thus all but one access point will remainidle
`while the one access pointis transmitting.
`FIGS. 4a-4d are graphsillustrating the transmitting power
`and range versusthe time during transmission of a packet in
`accordance with the present invention. The graphs illustrate
`that by adjusting power during, a packet transmission a more
`uniform range can be achieved. FIG. 4a includes a graph 82
`illustrating adjustmentof transmission of a packet where the
`data portion of the packet is transmitted at a power of 100
`milliwatts and the transmission power of the preamble and
`headerportion of the packet is lowered, so that the transmis-
`sion rangeofthe entire packet is uniform. As can be seen from
`graph 82, the poweris increased during the transmission of
`the PLCP header. Although this causes the transmission ofthe
`PLCPheaderto increase outside the desired range during the
`poweradjustment, access points outside the desired range
`will not receive a valid PLCP preamble, and therefore will
`ignore the portions of the header received as being interter-
`enceor noise. This allows adjustment of powerto be gradual
`as opposed to instantaneous. FIG. 46 includes a graph 84
`illustrating, a uniform range of 125 feet corresponding to the
`powertransmission graph of FIG. 4a.
`T'IG. 4c includes a graph 86 illustrating an adjustment of
`powerof transmission of a packet where the preamble and
`headerare transmitted at 100 milliwatts and the transmission
`
`40
`
`45
`
`powerof the data portion is increased, so that transmission
`range of the entire packet is more uniform. FIG. 4d includes
`a graph 88 illustrating a uniform range of 2000 feet corre-
`sponding to the power transmission graph of FIG. 4c.
`It is to be appreciated that a uniform range can be achieved
`by decreasing transmission power during, transmitting, of the
`PLCPpreamble with respect to transmitting powerofthe data
`portion, or increasing transmission power during the trans-
`(SED)field 75. ‘Uhe sync field 74 is used by the radio to detect
`mitting of the data portion of the packet with respect to
`a signal to receive, and to reach steady state frequency offset
`transmission power of the PLCP preamble.It is to be further
`correction and synchronization. The SFD field 75 is used to
`appreciated that numerousvariations of transmit power can
`indicate the end of the PLCP preamble 71 and beginning of
`the PLCP header 72. The fields 74 and 75 of the PLCP
`be selected for the PLCP preamble, the PLCP header and the
`preamble portion 71 are transmitted at a data rate of 1 Mbps.
`data portion for many given ranges and data rates. Although
`
`The PLCPheader 72 includesasignalfield 76, a servicefield the graphs 84 and 88illustrate power adjustment for two data
`77, a length field 78 and Cyclical Redundancy Correction 5
`rates, it is to be appreciated that the same principle could be
`(CRC) field 79. The fields 76, 77, 78 and 79 of the PLCP
`applied to a packet transmitting at three data rates or more. As
`headerare transmittedat a data rate of 1 Mbpsfor a long IEEE
`long as a full valid PLCP preamble is not received by an
`802.11 header and at 2 Mbpsfor a short IEFF 802.11 header.
`access point, the remaining portion of the packet will be
`The PDUportion 73 of the packet 70 can be transmittedat 1,
`disregarded as noise allowing the access point system to
`2, 5.5 or 11 Mbps.
`communicate to other devices during transmission of the
`FIG.3 illustrates a graph 80 corresponding to a transmis-
`packet.
`sion ofthe packet 70 with respect to range versesthe data rate
`FIG. Sa is a block diagram representative of each hard-
`ofthe packet transmission at a constant power of 100 milli-
`wired access point 54,. Each hardwired access point 54, is
`connected to the network backbone 52 via a connector 90
`watts. The PLCP header 71 transmitting at 1 Mbps at 100
`such as DB-9 or RJ-45 connector. The connector 90 is con-
`milliwatts can, for example, have a range of about 2000 feet
`nected to the network backbone 52 at one end andto a net-
`depending on antenna range, receiver sensitivity, antenna
`gain, cable loss etc. The PLCP 72 header 72 of the same
`packet transmitting at 2 Mbps at 100 milliwatts can have a
`range between 125 feet and 2000 feet. The data portion 73 of
`the samepacket transmitting at 11 Mbps at 100 milliwatts can
`have a range of 125 feet. Any access point receiving a valid
`PLCPpreamble mayremainidle until the entire transmission
`
`work adapter transceiver 92 included in the access point 54,
`at the other end. The network adapter transceiver 92 is con-
`figured according to conventional adapter transceiver tech-
`niquesto allowthe access point 54, to communicate overthe
`network backbone 52. The network adapter transceiver 92 is
`also connected to an internal bus 94 included within the
`
`5
`could be an omni-directional antenna if a generally spherical
`cell area of coverageis desired. A directed yagi-type antenna
`could be used as the antenna 62 for a more directed elliptical
`cell area of coverage.
`The cellular communication system 50 also includes one or
`more mobile communication units 66. The mobile commu-
`nication units 66 each include an antenna 67 for wirelessly
`communicating with other devices. Each mobile communi-
`cation unit 66 communicates with devices on the network
`
`backbone 52 via a selected access point 54 and/or with other
`mobile communication units, and/or directly with the host
`computer 60 if within cell range of the host computer 60.
`Upon roaming from onecell to another, the mobile commu-
`nication unit 66 is configured to associate itself with a new
`access point 54 or directly with the host computer 60 ifwithin
`range. A mobile communication unit 66 registers with a par-
`ticular access point which provides the particular mobile
`communications unit with wireless access to the network
`backbone52.
`Typically, access points 54 and mobile units 66 in different
`cells can communicate with each other during the same time
`period, such that simultaneous communicationis occurring in
`system 50. However, access points 54 and mobile units 66
`
`complying to the IEEE 802.11 protocol have cell ranges that
`are different with respect to different portions of a packet
`transmitted from an access point to a mobile unit or another
`access point. This is due to different portions ofa packetbeing,
`transmitted at different data rates and having ditterent modu-
`lations. FIG.2 illustrates portions of a packet 70 being trans-
`mitted at different data rates and thus having different trans-
`missionranges. FIG.2 is a block diagram depicting a Physical
`Layer Convergence Procedure (PLCP) frame or packet 70
`
`conforming to the IELE! standard 802.11 “Direct Sequence
`Spread Spectrum Physical Layer Specification”. Alterna-
`tively, the present invention may be employed utilizing the
`
`JEEEstandard 802.11 “Frequency Hopping Spread Spectrum
`Physical Layer Specification”or any other protocol transmit-
`ting portions ofpackets at varying modulations and data rates.
`The packet 70, for example, includes a PLCP preamble por-
`tion 71, a PLCP headerportion 72, and a Protocol Data Unit
`(PDU)portion 73 (data portion). The PLCP preamble 71
`includes a RF SYNCfield 74 and an Start Frame Delimiter
`
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`US 7,570,929 B1
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`7
`access point 54,. The access point 54, further includes a
`processor 98 connected to the bus 94 for controlling and
`carrying out the operations of the access point 54,. The pro-
`cessor 98 may include any ofa varietyof different micropro-
`cessors, such as the Motorola 68360 or Intel 80486 micro-
`processors.
`It
`is understood that any suitable processor
`capable of carrying out the herein described functionsofthe
`access points 54, may be used and falls within the scope of
`this invention.
`
`The access point 54, also includes a memory 100 con-
`nected to the bus 94. The memory 100 stores program code
`executed by the processor 98 for controlling the other ele-
`ments within the access point 54, to carry out the functions
`described hercin.It will be readily apparentto a person having
`ordinary skill in the art of microprocessor programming, how
`to program the pracessor 98 to carry out the operations
`described herein using conventional programming tech-
`niques based on the flowcharts and descriptions provided
`herein. Accordingly, additional detail as to the specific pro-
`gram code has been omitted. The memory 100 also serves to
`buffer packets of information such as those received overthe
`network backbone52or those transmitted to or received from
`the mobile communication units 66 or wireless access points
`54,. Furthermore, the memory 100 maystoretables relating
`to which ofthe mobile communication units 66 are registered
`to the network backbone 52 and/ortheidentification codes of
`the mobile communication units 66.
`Also connected to the bus 94 is a radio frequency (RF)
`section 110 includedin the access point 54,. The RF section
`110 includes the aforementioned antenna 62 for receiving,
`radio signals from the transmitting radio signals to mobile
`communication units 66 and wireless access points 54, (FIG.
`58) within the cell area of the access point 54,. Information
`transmitted from a mobile communication unit 66 or wireless
`access point 54, is received via the antenna 62 and is pro-
`cessed by an RF receiver 112 which is connected to the bus 94
`and demodulates and decodes the signal and converts the
`signal to a digital signal having a specific packet format. The
`processor 98 controls an RF transmitter 114 included in the
`RFsection 110, the RF transmitter also being connectedto the
`bus 94. The processor 98 causes the RF transmitter 114 to
`modulate and transmit an RF signal which in turn carries the
`information packetto the appropriate mobile communication
`unit 66 or wireless access point 54,. A powercontrol circuit
`115 is disposed between the antenna 62 and the RF transmit-
`ter 114. The power control circuit 115 controls the transmis-
`sion powerofdifferent portions ofa data packet transmitted
`by transmitter 114. The processorreceives range information
`from the mobile communication unitvia the receiver 112. The
`processor then calculates the necessary transmission power
`values needed for transmission of different portion of a
`packet. The powervaluesare loadedto the powercircuit 115,
`which dynamically adjusts the transmission power according
`to the downloaded powervalues during the transmission of a
`packct.
`FIG. 50is a block diagramrepresentative of each wireless
`access point 54, in the system 50. For the most part, the
`construction and operation of the components within the
`wireless access point 54,are identical to those described with
`respect lo the access points 54,. Hence, similar components
`are denoted simply by the addition of a. For example, the
`processor 98 in access point 54,is similar to the processor 98,
`in the wireless access point 54, . [lowever, the wireless access
`point 54, is not connected directly to the network backbone
`52 and therefore does not include a networktransceiver 92 or
`
`connector 90 as in each access point 54,. Rather, the wireless
`access point 54, communicates with mobile communication
`
`40
`
`45
`
`5
`
`8
`units