(12) Unlted States Patent
`(10) Patent N0.:
`US 7,570,929 B1
`
`Trompower
`(45) Date of Patent:
`Aug. 4, 2009
`
`USOO7570929B1
`
`(54)
`
`802.11 NETWORKS USING DYNAMIC
`POWER CONTROL FOR RF TRANSMISSION
`
`(75)
`
`Inventor: Michael L. Trompower, Navarre, OH
`(US)
`
`.
`.
`.
`(73) ASSIgnee: Symbo' TeChI‘OIOg‘eS’ Inc" HOhSVIHe’
`NY (US)
`.
`.
`.
`.
`Subject to any d1sc1a1mer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`.
`( "‘ ) Notlce:
`
`(21) Appl. N0.: 09/483,399
`
`(22) Filed:
`
`Jan. 14, 2000
`
`(51)
`
`Int. Cl-
`(2006.01)
`H043 1/04
`(52) US. Cl.
`................................................... 455/1143
`(58) Field of Classification Search ................. 455/114,
`455/91, 522, 127, 575, 64, 114.3, 574, 1271,
`
`
`455/1275. 13.4 375/297 296. 295 370/318, a a , I
`
`
`
`s
`370/319, 321, 465, 337, 347, 338; 709/229,
`709/240
`See application file for complete search history.
`_
`References Clted
`U. S. PATENT DOCUMENTS
`
`(56)
`
`5.289.459 A
`51331175 A *
`322(1):; 2
`5553:316 A
`5,572,528 A
`5,636,140 A *
`
`2/1994 BI9WH1_ifi= ~~~~~~~~~~~~~~~~~~~~~ 370/17
`
`7/1994 Anyavmlakm cl a1
`" 349/38
`13133; $311516 """""""
`3740/9/56?
`
`9/1996 Diepstraten et a1.
`.
`455/69
`
`370/8513
`11/1996 Sheun .............
`.................... 364/514
`6/1997 Tee et a1,
`
`5,706,428 A *
`5,708,681 A
`5,768,695 A *
`
`59825807 A if
`5,987,011 A
`5,987,033 A
`6,301,231 B1 *
`6,463,042 B1 5
`
`.................. 370/342
`1/1998 Boer et a1.
`1/1998 Nialkemes et a1.
`375/297
`
`6/1998 Fischer et 31.
`.....
`455/127
`
`
`375/146
`11/ 1999 Snell """""
`
`370/331
`11/1999 Toh ........
`370/445
`.....
`11/1999 Boer et a].
`370/316
`10/2001 Hassan et al.
`..
`
`10/2002 Paatelma .................... 370/318
`
`* cited by examiner
`
`Primary ExamineriMelody Mehrpour
`(74)At10rney, Agent, or FirmiAmin, Turocy & Calvin, LLP
`
`(57)
`
`ABSTRACT
`
`
`
`A system and method is provided for adjusting transmission
`power of dif erent portions of a data packet. The system and
`
`method is especially useful when utilizing the 131313 802.11
`standard protocol due to the varying transmission data rates of
`a packet. A BEE 802.11 packet includes a preamble portion,
`a header portion and a data portion. The preamble portion has
`a data rate ofl Mbps, the headerhas a data rate ofl or2 Mbps
`
`and the data ortion has a data rate of], 2, 5.5 or 11 Mb s, AtP P
`
`a given fixed power level, a transmission at 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 transmission
`at higher ranges to remain idle during transmission of an
`entire frame. The system and method can be applied to both
`access points and mobile units in a cellular connnunications
`Syswm‘
`
`31 Claims, 10 Drawing Sheets
`
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`Page 1 of 19
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`SAMSUNG EXHIBIT 1033
`
`Page 1 of 19
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`SAMSUNG EXHIBIT 1033
`
`

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`Page 2 of 19
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`Page 2 of 19
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`

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`US. Patent
`
`Aug. 4, 2009
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`Sheet 2 of 10
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`

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`US. Patent
`
`Aug. 4, 2009
`
`Sheet 3 0f 10
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`us 7,570,929 B1
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`Page 4 of 19
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`

`US. Patent
`
`Aug. 4, 2009
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`Sheet 4 of 10
`
`US 7,570,929 B1
`
`POVVER
`MILLIWATTS
`
`70
`
`FEET
`
`2000
`
`PLCP
`PREAMBLE
`
`PLCP HEADER
`
`PSDU (DATA PORTION)
`
`Fig. 4a
`
`
`
`PLCP
`PREAMBLE
`
`PLCP HEADER
`
`PSDU (DATA PORTION)
`
`7°]
`
`Fig. 4b
`
`Page 5 of 19
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`Page 5 of 19
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`

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`US. Patent
`
`Aug. 4, 2009
`
`Sheet 5 of 10
`
`US 7,570,929 B1
`
`‘(r—SG
`
`PLCP
`
`PLCP HEADER
`
`PSDU (DATA PORTION)
`
`Fig. 4c
`
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`
`Page 6 of 19
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`Page 6 of 19
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`

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`US. Patent
`
`Aug. 4, 2009
`
`Sheet 6 of 10
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`US 7,570,929 B1
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`62
`
`
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`Wow-
`
`CONTROL
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`CONTROL
`
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`
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`
`Page 7 of 19
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`Page 7 of 19
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`

`

`US. Patent
`
`Aug. 4, 2009
`
`Sheet 7 0f 10
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`us 7,570,929 B1
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`

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`US. Patent
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`Aug. 4, 2009
`
`Sheet 8 of 10
`
`US 7,570,929 B1
`
`98
`
`TRANSMIT/
`
`RECEIVE
`
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`MODULE
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`TRANSMIT
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`
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`-K-K-KKI4l<
`
`Page 9 of 19
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`Page 9 of 19
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`

`

`US. Patent
`
`Aug. 4, 2009
`
`Sheet 9 of 10
`
`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
`
`
`
`PROCESSOR CONFIGURES DATA POWER
`WORDS
`
`
`
`150
`
`160
`
`170
`
`180
`
`190
`
`200
`
`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
`
`
`Page 10 of 19
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`210
`
`220
`
`Page 10 of 19
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`

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`US. Patent
`
`Aug. 4, 2009
`
`Sheet 10 of 10
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`US 7,570,929 B1
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`
`
`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
`
`250
`
`260
`
`270
`
`280
`
`290
`
`300
`
`
`
`PROCESSOR CONFIGURES DATA POWER
`WORDS
`
`
`
`
`
`PROCESSOR CONFIGURES DATA PACKET FOR
`TRANSMISSION
`
`
`
`
`
`
`
`
`
`PROCESSOR DOWLOADS POWER DATA TO
`D/A CONVERTER FOR BEGINNING OF
`
`TRANSMISSION
`
`
`
`
`ACCESS POINT BEGINS TRANSMISSION OF
`PACKET
`
`310
`
`320
`
`PROCESSOR DOWNLOADS N NUMBER OF
`
`POWER DATA WORDS DURING
`
`TRANSMISSION OF PACKET BASED ON N
`NUMBER OF DATA RATES
`
`Fig. 9
`
`Page 11 of19
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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 RF TRANSMISSION
`
`TECHNICAL FIELD
`
`The present invention generally relates to communication
`systems, and inparticular to a system and method for increas-
`ing throughput of a communication system.
`
`
`
`BACKGROUND OF THE INVENTION
`
`The use 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 cormnunications systems with
`mobile data terminals to track inventory and replenish stock.
`The transportation industry may use such systems at 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 systems are also utilized for cel—
`lular telephone communications to allow users with wireless
`telephones to roam across large geographical regions while
`retaining telephonic access. Paging networks also may utilize
`ccllular communications systcms which cnablc a user carry-
`ing a pocket sized pager to be paged anywhere within a
`geographic region.
`A typical cellular communications system includes a num—
`ber of fixed access points (also known as base stations) inter-
`connected by a cable medium often referred to as a system
`backbone. Also included in many cellular communications
`systems are intemrediate access points which are not directly
`connected to the system backbone but otherwise perform
`many of the same functions as the fixed access points. Inter-
`mediate access points, often referred to as wireless access
`points or base stations, increase the area within which access
`points connected to the system backbone can communicate
`with mobile devices.
`
`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 from a
`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 combined cell area
`coverage from each access point provides full coverage of a
`building or site.
`Mobilc devices such as tclcphoncs, pagcrs, pcrsonal digital
`assistants (PDA’s), data terminals etc. are designed to be
`carried throughout the system from cell to cell. Each mobile
`device is capable of communicating with the system back-
`bone via wireless communication between the mobile device
`and an access point to which the mobile device is registered.
`As the mobile device roams from one cell to another, the
`mobile device will typically deregister with the access point
`of the previous cell and register with the access point associ-
`ated with the new cell. In order to provide suflicient 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
`throughout an 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 WLANs is a standard for systems that operate in the
`2,400-2,483.5 MHz industrial, scientific and medical (ISM)
`
`10
`
`15
`
`20
`
`30
`
`35
`
`40
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`45
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`60
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`65
`
`2
`band. The ISM band is 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 powerlevel 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
`of during an entire frame or frame exchange. This causes
`stations that are outside an intended transmission range to
`remain idlc during thc framc transmission thcrcby reducing
`the entire throughput of the system.
`An attempt has been made to solve this problem by pro-
`viding multiple access stations at a single location operating
`on different frequencies. However, 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 expensive in 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 with idle access
`stations whcn all thrcc channcls are operating. Furthcrmorc,
`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 overcomes the aforementioned problems.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides for a system and method for
`adjusting transmission power level of different portions of a
`datapacket. The system and method is 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 has a data rate of
`1 Mbps (Megabits per second), the header has a data rate ofl
`or 2 Mbps andthe data portionhas a data rate of l, 2, 5.5 or 11
`Mbps. At a given fixed power level, a transmission at 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 Lmiform range. This eliminates the need for
`components in the system receiving a preamble portion of a
`transmission at the higher ranges to remain idle during trans-
`mission of an entire frame as is the standard in the IEEE
`802.11. Furthermore,
`the present
`invention allows
`for
`dynamic adjustment of the power transmission level, 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 a ccllular 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 coupled to the trans-
`mitter. The power control module is adapted to receive a data
`packet having a first portion and a second portion and transmit
`the first portion at a first transmission powcr lcvcl and the
`second portion at a second transmission power level.
`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
`
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`

`US 7,570,929 B1
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`
`
`3
`portion of the data packet at a first transmission power level
`and transmitting a second portion of the data packet at a
`second transmission power level.
`Another aspect ofthe present invention relates to an access
`point system in a cellular communication system utilizing an
`IEEE 802.11 standard protocol. The system includes a trans-
`mitter adapted to transmit data over an RF link and a power
`control module coupled to the transmitter. The power control
`mocule is adapted to receive a data packet having a PLCP
`preamble and PLCP header portion and a data portion. The
`power control module is also adapted to dynamically adjust
`the transmission power of the packet during transmission of
`the packet, such that the PLCP preamble portion begins trans-
`mitting at a first transmission power level and the data portion
`begins transmitting at a second transmissionpower level. 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 coupled to the proces-
`sor. The receiver is adapted to receive data over an RF link.
`Furthermore, 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 power level, of the first portion with respect to
`the second portion ofthe data packet coupled to the means for
`transmitting a data packet having a 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. The signal includes a first portion transmitted at a first
`power level and a second portion transmitted at a second
`power level.
`To the accomplishment of 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 drawings set forth in
`detail certain illustrative embodiments of the invention.
`These embodiments are indicative, however, of but a few of
`the various ways in which the principles 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
`
`
`
`F G. 1 illustrates a system diagram of a network commu-
`nication system in accordance with the present invention;
`
`F G. 2 illustrates a protocol of a IEEE 802.11 standard data
`packet in accordance with the present invention;
`F G. 3 illustrates a graph of a range of a transmission for
`different portions ofthe data packet ofFIG. 2 at a given power
`level in accordance with the present invention;
`F G. 4a illustrates a graph of a power of a transmission for
`different portions of the data packet of FIG. 2 at a reduced
`power level for the PLCP preamble in accordance with the
`present invention;
`F G. 4b illustrates a graph of a range ofa transmission with
`respect to the power graph of FIG. 4a in accordance with the
`present invention;
`F G. 40 illustrates a graph of a power of a transmission for
`different portions ofthe data packet of FIG. 2 at an increased
`power level for the PLCP data portion in accordance with the
`present invention;
`
`10
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`15
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`20
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`60
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`4
`FIG. 40/ illustrates a graph of a range ofa transmission with
`respect to the power graph of FIG. 40 in accordance with the
`present invention;
`FIG. 5a illustrates a block diagram of a hard wired access
`point system in accordance with the present invention;
`FIG. 5b 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 diagram of 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 meth-
`odology for configuring the power control 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
`
`The present invention will now be 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 now to FIG. 1, a cellular communication system
`50 illustrating an environment of the present invention is
`shown. The cellular connnunication 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 rmderstood that more than one hardwired access
`points 54a may be physically connected to the network back-
`bone 52. The access points 54 may be hardwired to the net-
`work 52 such as access point 54,, or may be wirelessly
`coupled to the backbone 52 such as access point 541,. 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-
`cation system 50. As is conventional, each wireless access
`point 54,, associates itself, typically by registration, with
`another access point or a host computer 60 coupled to the
`network backbone 52, whether hardwired or wireless, such
`that a link is formed between itself and other devices situated
`on the network backbone 52.
`Each access point 54 is capable ofwirelessly communicat-
`ing with other devices in the communication system 50 via
`respective antemias commonly denoted by reference numeral
`62. The antenna 62 for any particular device may be of any
`type suitable for use in a network cellular communication
`system, such as an omni-directional antenna, a yagi-type
`antenna, etc. A geographic cell (not shown) associated with
`each access point 54 defines a region of coverage in which
`successful wireless communication may occur. Depending
`on the type of antenna 62 selected and output power of the
`respective access point, the geographic cell may take one of
`several different forms and sizes. For example, the antenna 62
`
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`US 7,570,929 B1
`
`5
`could be an omni-directional antenna if a generally spherical
`cell area of coverage is desired. A directed yagi-type antenna
`could be used as the antelma 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 one cell 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
`backbone 52.
`Typically, access points 54 and mobile tmits 66 in different
`cells can communicate with each other during the same time
`period, such that simultaneous communicationis occurring in
`system 50. Howeve‘, 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 differentportions ofa packet being
`transmitted at different data rates and having different modu-
`lations. FIG. 2 illustrates portions of a packet 70 being trans-
`mitted at different data rates and thus having different trans-
`mission ranges. FIG. 2 is a block diagram depicting a Physical
`Layer Convergence Procedure (PLCP) frame or packet 70
`
`conforming to the IEEE standard 802.11 “Direct Sequence
`Spread Spectrum Physical Layer Specification”. Alterna-
`tively, the present invention may be employed utilizing the
`
`IEEE standard 802.1 1 “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 header portion 72, and a Protocol Data Unit
`(PDU) portion 73 (data portion). The PLCP preamble 71
`includes a RF SYNC field 74 and an Start Frame Delimiter
`
`(SFD) field 75. The sync field 74 is used by the radio to detect
`a signal to receive, and to reach steady state frequency offset
`correction and synchronization. The SFD field 75 is used to
`indicate the end of the PLCP preamble 71 and begimling of
`the PLCP header 72. The fields 74 and 75 of the PLCP
`preamble portion 71 are transmitted at a data rate of 1 Mbps.
`The PLCP header 72 includes a signal field 76, a service field
`77, a length field 78 and Cyclical Redundancy Correction
`(CRC) field 79. The fields 76, 77, 78 and 79 of the PLCP
`header are transmitted at a data rate of 1 Mbps for a long IEEE
`802.11 header and at 2 Mbps for a short IF.F.F, 802.1 1 header.
`The PDU portion 73 of the packet 70 can be transmitted at 1,
`2, 5.5 or 11 Mbps.
`FIG. 3 illustrates a graph 80 corresponding to a transmis-
`sion ofthe packet 70 with respect to range verses the data rate
`of the packet transmission at a constant power of 100 milli—
`watts. The PLCP header 71 transmitting at 1 Mbps at 100
`milliwatts can, for example, have a range of about 2000 feet
`depending on antenna range, receiver sensitivity, antemla
`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 same packet transmitting at 1 1 Mbps at 100 milliwatts can
`have a range of 125 feet. Any access point receiving a valid
`PLCP preamble may remain idle until the entire transmission
`
`5
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`10
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`15
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`20
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`30
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`35
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`6
`is complete because the access point will assume that the
`device transmitting the PLCP preamble is 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 within2000 feet
`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 remain idle
`while the one access point is transmitting.
`FIGS. 4a-4d are graphs illustrating the transmitting power
`and range versus the 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. 411 includes a graph 82
`illustrating adjustment of 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
`header portion of the packet is lowered, so that the transmis—
`sion range ofthe entire packet is unifonn. As can be seen from
`graph 82, the power is increased during the transmission of
`the PLCP header. Although this causes the transmission ofthe
`PLCP header to increase outside the desired range during the
`power adjustment, 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 interfer-
`ence or noise. This allows adjustment of power to be gradual
`as opposed to instantaneous. FIG. 417 includes a graph 84
`illustrating a uniform range of 125 feet corresponding to the
`power transmission graph of FIG. 4a.
`FIG. 46 includes a graph 86 illustrating an adjustment of
`power of transmission of a packet where the preamble and
`header are transmitted at 100 milliwatts and the transmission
`
`power of the data portion is increased, so that transmission
`range of the entire packet is more unifonn. FIG. 40’ includes
`a graph 88 illustrating a uniform range of 2000 feet corre-
`sponding to the power transmission graph of FIG. 40.
`It is to be appreciated that a uniform range can be achieved
`by decreasing transmission power during transmitting of the
`PLCP preamble with respect to transmitting power ofthe data
`portion, or increasing transmission power during the trans-
`mitting of the data portion of the packet with respect to
`transmission power of the PLCP preamble. It is to be further
`appreciated that numerous variations of transmit power can
`be selected for the PLCP preamble, the PLCP header and the
`data portion for many given ranges and data rates. Although
`the graphs 84 and 88 illustrate power adjustment for two data
`rates, it is to be appreciated that the same principle could be
`applied to a packet transmitting at three data rates or more. As
`long as a full valid PLCP preamble is not received by an
`access point, the remaining portion of the packet will be
`disregarded as noise allowing the access point system to
`communicate to other devices during transmission of the
`packet.
`FIG. 50 is a block diagram representative of each hard-
`wired access point 54“. Each hardwired access point 54,, is
`connected to the network backbone 52 via a connector 90
`such as DB-9 or RJ-45 connector. The connector 90 is con-
`nected to the network backbone 52 at one end and to a net-
`
`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-
`niques to allow the access point 54,, to communicate over the
`network backbone 52. The network adapter transceiver 92 is
`also connected to an intemal bus 94 included within the
`
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`US 7,570,929 B1
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`7
`access point 54“. The access point 54a 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 of a variety of 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 functions of the
`access points 54“ may be used and falls within the scope of
`this invention.
`
`The access point 54a 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 54a to carry out the functions
`described herein. It will be readily apparent to a person having
`ordinary skill in the art of microprocessor programming how
`to program the processor 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 over the
`network backbone 52 or those transmitted to or received from
`the mobile communication units 66 or wireless access points
`541,. Furthermore, the memory 100 may store tables relating
`to which ofthe mobile communication units 66 are registered
`to the network backbone 52 and/or the identification codes of
`the mobile communication units 66.
`Also connected to the bus 94 is a radio frequency (RF)
`section 110 included in 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 541, (FIG.
`51)) within the cell area of the access point 54a. Information
`transmitted from a mobile communication unit 66 or wireless
`access point 54b 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
`RF section 1 1 0, the RF transmitter also being connected to the
`bus 94. The processor 98 causes the RF transmitter 114 to
`modulate and transmit an RF signal which in turn carries the
`information packet to the appropriate mobile communication
`unit 66 or wireless access point 54b. A power control circuit
`115 is disposed between the antenna 62 and the RF transmit-
`ter 114. The power control circuit 115 controls the transmis-
`sion power of different portions of a data packet transmitted
`by transmitter 114. The processor receives range information
`from the mobile communication unit via the receiver 112. The
`processor then calculates the necessary transmission power
`values needed for transmission of different portion of a
`packet. The power values are loaded to the power circuit 115,
`which dynamically adjusts the transmission power according
`to the downloaded po