I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US007158493Bl
`
`c12) United States Patent
`Uhlik et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 7,158,493 Bl
`Jan.2,2007
`
`(54) RADIO COMMUNICATIONS SYSTEM WITH
`A MINIMAL BROADCAST CHANNEL
`
`(75)
`
`Inventors: Christopher Richard Uhlik, Danville,
`CA (US); Michael Youssefmir, Portola
`Valley, CA (US); Mitchell D. Trott,
`Mountain View, CA (US); Craig H.
`Barratt, Redwood City, CA (US)
`
`(73) Assignee: ArrayComm, LLC, San Jose, CA (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 668 days.
`
`(21) Appl. No.: 09/675,748
`
`(22) Filed:
`
`Sep. 29, 2000
`
`(51)
`
`Int. Cl.
`H04Q 7100
`(2006.01)
`(52) U.S. Cl. ....................................... 370/329; 370/320
`(58) Field of Classification Search ................ 370/320,
`370/322,329,330,431,436,437,468,311,
`370/328,331,335,336,339,338,348,349,
`370/350
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,430,761 A * 7/1995 Bruckert et al ............. 375/144
`
`5,806,003 A *
`6,366,602 Bl *
`6,400,695 Bl *
`6,539,237 Bl *
`
`9/1998 Jolma et al ................. 455/522
`4/2002 Raitola ....................... 375/135
`6/2002 Chuah et al.
`............... 370/310
`3/2003 Sayers et al. ............... 455/555
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`WO
`WO
`WO
`WO
`
`0 928 119 A2
`0928119 A
`WO 98/14024
`W09814024 A
`WO 98/53561
`W09853561 A2
`
`7 /1999
`7 /1999
`4/1998
`4/1998
`11/1998
`11/1998
`
`* cited by examiner
`
`Primary Examiner-Doris H. To
`Assistant Examiner-Thien D. Tran
`(74) Attorney, Agent, or Firm-Blakely Sokoloff Taylor &
`Zafman LLP
`
`(57)
`
`ABSTRACT
`
`In one embodiment, the present invention comprises trans(cid:173)
`mitting a broadcast burst in a broadcast channel from a base
`station of a radio communications system. The invention
`further comprises receiving a request burst from a user
`terminal, and transmitting a message burst from the base
`station to the user terminal from which the request was
`received. The message burst includes a description of the
`channels available on the radio communications system for
`receiving messages from user terminals.
`
`72 Claims, 6 Drawing Sheets
`
`------------------- ------------,
`
`4
`
`4
`
`4X4
`
`RF TRANSMIT
`MODULES
`
`233
`
`4
`
`245
`
`237
`
`231
`
`HOST
`OSP
`
`HIGHER LEVEL PROCESSING
`
`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan. 2, 2007
`
`Sheet 1 of 6
`
`US 7,158,493 Bl
`
`20
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`68
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`
`64
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`Modulators
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`I
`____________________________ J
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`: Wide Area:
`l Network :
`561-------
`
`F ! G. 1
`
`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan.2,2007
`
`Sheet 2 of 6
`
`US 7,158,493 Bl
`
`24
`
`/
`
`48
`
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`D
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`
`68
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`
`64
`
`From
`Signal Modulators
`
`FIG.2
`
`74
`
`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan.2,2007
`
`Sheet 3 of 6
`
`US 7,158,493 Bl
`
`72
`
`SOMA
`Controller
`
`182
`
`r·---------
`
`164
`
`184
`----------------------
`SDMAP
`162
`
`~48
`------------.
`160
`
`44
`
`From
`Rocalvo~
`
`Data
`Compressor
`
`Source
`Tracker
`
`/176
`
`Signal
`Detector
`
`168
`
`Parameter
`Estimator
`
`170
`
`174
`
`"\.
`172
`
`80
`
`To
`Spdaf
`Mulllp&aler
`
`.
`:74
`
`Multiplexer
`Controller
`
`178 .
`.
`76;
`
`To
`Spaoal
`
`Demultiplexer
`Controller
`
`-------------------------------------------------~
`FIG. 3
`
`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan.2,2007
`
`Sheet 4 of 6
`
`US 7,158,493 Bl
`
`r - - - - - -
`
`- - - - -
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`
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`
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`MODULES
`
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`
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`
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`
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`
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`PROCESSORS
`
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`
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`
`HOST
`DSP
`
`HIGHER LEVEL PROCESSING
`
`Figure 4
`
`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan.2,2007
`
`Sheet 5 of 6
`
`US 7,158,493 Bl
`
`SI 1 µs
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`Intel, Exhibit 1004
`
`

`

`U.S. Patent
`
`Jan.2,2007
`
`Sheet 6 of 6
`
`US 7,158,493 Bl
`
`Remote Tenninal
`
`Scan BCH channels
`Acquire Frame Timing
`Acquire Synchronization
`Build Map of Base
`Stations BCHs and
`BSCCs
`Select Base Station
`Build CR using UTID and
`transmit power
`Scramble CR using BSCC
`
`Adjust timing and power
`
`Base Station
`300 Acauire GPS Tirnin~
`302 Determine BCH slot time
`304
`306
`308
`310
`312
`
`BCH=>
`
`314
`316
`
`318
`320
`
`322 Unscamble CR using
`BSCC
`324 Determine Spatial
`Signature of Remote CR
`
`326
`
`328
`330
`332
`334
`336
`338
`340
`342
`
`<= Configuration
`Reauest
`
`Configuration Message
`=>
`
`<= Traffic Reauest
`Traffic Assismment =>
`<:::: Traffic =>
`Send packet =>
`<:::: Send DA and packt
`Send DA and packet=>
`<:::: Send DA and packet
`
`Figure 8
`
`Intel, Exhibit 1004
`
`

`

`US 7,158,493 Bl
`
`1
`RADIO COMMUNICATIONS SYSTEM WITH
`A MINIMAL BROADCAST CHANNEL
`
`BACKGROUND OF THE INVENTION
`
`2
`In another embodiment the present invention comprises
`receiving a plurality of timing sequences on a broadcast
`channel from at least one base station, determining network
`timing using the received timing sequences, determining a
`5 network access request transmission time using the network
`timing, transmitting a network access request at the deter(cid:173)
`mined time, and receiving a message burst from a base
`station. The message burst includes a description of the
`channels available on the wireless network.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention is illustrated by way of example,
`and not by way of limitation, in the figures of the accom(cid:173)
`panying drawings in which like reference numerals refer to
`similar elements and in which:
`FIG. 1 is a diagram illustrating an exemplary architecture
`of a wireless communication system according to one
`embodiment of the present invention;
`FIG. 2 is a diagram illustrating transmission patterns of a
`multi-channel spatial diversity transmitter according to one
`embodiment of the present invention;
`FIG. 3 is a block diagram illustrating a spatial diversity
`multiple access processor according to one embodiment of
`25 the present invention;
`FIG. 4 shows a simplified block diagram of a base station
`on which an embodiment of the invention can be imple(cid:173)
`mented;
`FIG. 5 is a diagram illustrating an example of a broadcast
`30 burst structure according to one embodiment of the present
`invention;
`FIG. 6 is a diagram illustrating an example of a Configu(cid:173)
`ration Request burst structure according to one embodiment
`of the present invention;
`FIG. 7 is a diagram illustrating an example of a Configu(cid:173)
`ration Message burst structure according to one embodiment
`of the present invention; and
`FIG. 8 is a diagram illustrating a connnunications
`sequence according to one embodiment of the present inven-
`40 tion.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`1. Field of the Invention
`The present invention applies to radio connnunications
`systems in which several remote terminals connnunicate
`voice or data with a base station and, in particular, to such
`systems in which the base stations use a broadcast channel 10
`with a very low data rate.
`2. Description of the Prior Art
`Mobile radio communications systems such as cellular
`voice radio systems typically have a base station available
`for use by mobile remote terminals, such as cellular tele- 15
`phones or wireless web devices. The base station typically
`transmits a broadcast channel (BCH) The BCH is broadcast
`to all remote terminals whether they are registered on the
`network or not and informs the remote terminals about the
`network. In order to access the network, a remote terminal 20
`must normally tune to and listen to the BCH before access(cid:173)
`ing the network. A remote terminal will typically scan a
`range of likely frequencies when it wants to access the
`network until it finds the strongest BCH, it will then use the
`information in the BCH to access the network.
`The BCH is typically filled with data about the network in
`order to reduce the amount of information that must be
`transmitted to any particular remote terminal in the access(cid:173)
`ing, registering, authenticating or logging-on process. As a
`result, after registration, the remote terminal does not require
`any further information other than a specific channel assign(cid:173)
`ment from the already known channel set in order to initiate
`a call.
`The broadcast channel is typically transmitted at a rela(cid:173)
`tively high power level so that any remote terminal in any 35
`location within the range of the base station can receive it
`clearly. The high power level and the high data rate in
`combination make it likely that the broadcast channel will
`interfere with other traffic channels of the radio connnuni(cid:173)
`cations system. When there are several different base sta(cid:173)
`tions transmitting on one or more broadcast channels, the
`possibility of and amount of interference is greater.
`The present invention reduces the interference caused by
`the broadcast channel. This allows less of the channel
`resources to be dedicated to the broadcast channel and more 45
`of the channel resources to be dedicated to the traffic
`channels. In one embodiment, the broadcast channel is
`transmitted to all remote terminals that enter within the
`range of the base station while other connnunications are
`transmitted directly to the intended remote terminal on a 50
`channel that creates much less interference with other
`remote terminals. In such an embodiment, the present inven(cid:173)
`tion, by transmitting less data on the broadcast channel and
`more data on a specifically directed channel, reduces broad(cid:173)
`cast channel interference still more.
`
`Basic Structure
`FIG. 1 shows an example of a wireless connnunications
`system or network in which a number of subscriber stations,
`also referred to as remote terminals or user terminals,
`(symbolically shown as handsets) 20, 22, 24, are being
`served by a base station 100 that may be connected to a wide
`area network (WAN) 56 for providing any required data
`services and connections external to the innnediate wireless
`system. The present invention relates to wireless connnuni-
`55 cation systems and may be a fixed-access or mobile-access
`wireless network using spatial division multiple access
`(SDMA) technology in combination with multiple access
`systems, such as time division multiple access (TDMA),
`frequency division multiple access (FDMA) and code divi-
`60 sion multiple access (CDMA). Multiple access can be com(cid:173)
`bined with frequency division duplexing (FDD) or time
`division duplexing (TDD). A switching network 58 inter(cid:173)
`faces with a WAN 56 for providing multi-channel duplex
`operation with the WAN by switching incoming WAN data
`65 to lines 60 of the base station 100 and switching outgoing
`signals from the base station 100, on lines 54 to the WAN.
`Incoming lines 60 are applied to signal modulators 62 that
`
`BRIEF SUMMARY OF THE INVENTION
`
`In one embodiment, the present invention comprises
`transmitting a broadcast burst in a broadcast channel from a
`base station of a radio connnunications system. The inven(cid:173)
`tion further comprises receiving a request burst from a user
`terminal, and transmitting a message burst from the base
`station to the user terminal from which the request was
`received. The message burst includes a description of the
`channels available on the radio connnunications system for
`receiving messages from user terminals.
`
`Intel, Exhibit 1004
`
`

`

`US 7,158,493 Bl
`
`25
`
`3
`produce modulated signals 64 for each subscriber station to
`which the base station is transmitting. A set of spatial
`multiplexing weights for each subscriber station are applied
`74 to the respective modulated signals in spatial multiplex(cid:173)
`ers 66 to produce spatially multiplexed signals 68 to be
`transmitted by a bank of multi-channel transmitters 70 using
`a transmit antenna array 18. The SDMA processor (SD(cid:173)
`MAP) 48 produces and maintains spatial signatures for each
`subscriber station for each conventional channel, calculates
`spatial multiplexing and demultiplexing weights for use by
`spatial multiplexers 66, and spatial demultiplexers 46, and
`uses the received signal measurements 44 to select a channel
`for a new connection. In this manner, the signals from the
`current active subscriber stations, some of which may be
`active on the same conventional channel, are separated and
`interference and noise suppressed. When communicating
`from the base station to the subscriber stations, an optimized
`multi-lobe antenna radiation pattern tailored to the current
`active subscriber station connections and interference situ(cid:173)
`ation is created. An example of a transmit antenna pattern
`that may be created is shown in FIG. 2. Suitable technolo(cid:173)
`gies for achieving such a spatially directed beam are
`described, for example, in U.S. Pat. No. 5,828,658, issued
`Oct. 27, 1998 to Ottersten et al. and U.S. Pat. No. 5,642,353,
`issued Jun. 24, 1997 to Roy, III et al.
`Returning to FIG. 1 spatial demultiplexers 46 combine
`received signal measurements 44 from the multi-channel
`receivers 42 and associated antenna array 19 according to
`spatial demultiplexing weights 76, a separate set of demul(cid:173)
`tiplexing weights being applied for each subscriber station
`communicating with the base station. The outputs of the
`spatial demultiplexers 46 are spatially separated signals 50
`for each subscriber station communicating with the base
`station. In an alternate embodiment, the demultiplexing and
`demodulation processing are performed together in a non(cid:173)
`linear multidimensional
`signal processing unit. The
`demodulated received signals 54 are then available to the
`switching network 58 and the WAN 56. The multi-channel
`receivers also receive timing signals from GPS (Global
`Positioning System) satellites or some other radio precision
`timing signal which is then provided to the SDMAP for
`precise timing that is synchronized across all base stations in
`the system.
`In an FDMA system implementation, each multi-channel
`receiver and each multi-channel transmitter is capable of
`handling multiple frequency channels. In other embodi(cid:173)
`ments, the multi-channel receivers 42 and multi-channel
`transmitters 70 may instead handle multiple time slots, as in
`a TDMA system, multiple codes, as in a CDMA system, or
`some combination of these well-known multiple access
`techniques.
`FIG. 3 shows a breakdown of a Spatial Division Multiple
`Access signal Processor (SD MAP) 48. The function of the
`SD MAP includes determining how many signals are present 55
`in a particular channel, estimating signal parameters such as
`the spatial location of the transmitters (i.e., directions-of(cid:173)
`arrival (DOAs) and distance from the base station), and
`determining the appropriate spatial demultiplexing and mul(cid:173)
`tiplexing schemes. The inputs 44 to the SDMAP include
`outputs of base station receivers, one for each receiving
`antenna. In one embodiment, the receivers perform quadra(cid:173)
`ture detection of the signals as in current systems, in which
`case there are in-phase (I) and quadrature (0) components
`(signals) output from each channel behind each antenna. In 65
`another embodiment, a single down-converted component, I
`or Q or any combination thereof, is used. In one embodi-
`
`4
`ment, the receivers digitize the data before passing it to the
`SDMAP. In another embodiment, digitization is performed
`in the data compressor 160.
`In one embodiment of the invention, the SDMAP accom-
`5 plishes its task by first obtaining estimates of important
`signal related parameters such as their directions-of-arrival
`(DO As) without exploiting temporal properties of the signal.
`This is appropriate, for example, in situations where analog
`modulation schemes are employed and little is known about
`10 the signal waveform. In a second embodiment, known
`training sequences placed in digital data streams for the
`purpose of channel equalization can be used in conjunction
`with sensor array information to calculate signal parameter
`estimates such as DOAs and signal power levels. This
`15 information is then used to calculate appropriate weights 76
`for a spatial demultiplexer, implemented in this embodiment
`as a linear combiner, i.e., a weight-and-sum operation. In a
`third embodiment, time-of-arrival (TOA)-related parameters
`from the parameter estimator are used in conjunction with
`20 signal correlation parameters to ascertain which signals are
`multi-path versions of a common signal. Relative delays are
`then calculated such that the signals can be coherently
`combined, thus further increasing the quality of the esti-
`mated signals.
`However, in another embodiment of this invention, the
`function of the spatial demultiplexer is performed in con(cid:173)
`junction with the estimation of other source parameters such
`as the DOAs. As an example of one such embodiment of this
`type, the constant modulus property (i.e., constant ampli-
`30 tude) of various communication signals such as digital
`phase-shift-keyed (PSK) and analog FM waveforms can be
`exploited along with properties of the array of receiving
`antennas to simultaneously estimate the source waveforms
`as well as their DOAs using multi-channel constant-modulus
`35 algorithms (CMA) which are well-known in the art.
`In another embodiment, extended Kalman filters, also
`well-known in the art, can be used to exploit these and
`similar properties. In these and similar embodiments, the
`function of the spatial demultiplexer 46 is assumed by the
`40 SDMAP 48, and the outputs 76 of the SDMAP are the
`spatially demultiplexed signals to be sent to the demodula(cid:173)
`tors.
`Referring again to FIG. 3, data compression 160 is
`performed to reduce the amount of data, and, in one embodi-
`45 ment, consists of accumulation of a sample covariance
`matrix involving sums of outer products of the sampled
`receiver outputs in a particular channel. Hereafter, these
`sampled outputs are referred to as data vectors, and there is
`one such data vector at each sample time for each of the
`50 channels assigned to a particular base station. In another
`embodiment, the compressed data are simply the unproc(cid:173)
`essed data vectors. Ifl and Q signals 44 are output from the
`receivers, each data vector is a collection of mr complex
`numbers, one for each of the mr receiver/antenna pairs.
`In a third embodiment, data compression also includes
`using known signal information such as training sequences
`present in wireless digital systems and mobile unit transpon(cid:173)
`der responses in current analog systems to calculate time(cid:173)
`of-arrival (TOA) of a distinct periodic signal feature, a
`60 parameter containing valuable information related to the
`distance between cell sites and the wireless transmitter
`which is exploited in this embodiment.
`Compressed data 162 are passed to a signal detector 164
`for detection of the number of signals present in the channel.
`In one embodiment, statistical detection schemes are
`employed in conjunction with information from a SDMA
`controller 72 to estimate the number of sources present in the
`
`Intel, Exhibit 1004
`
`

`

`US 7,158,493 Bl
`
`5
`channel. This information and the ( compressed) data 168 are
`sent to a parameter estimator 170 where estimates of signal
`parameters including those related to the source locations
`(e.g., DOAs and range) are obtained.
`Location-related parameter estimates 172 are passed to a 5
`source tracker 17 4. In one embodiment, the function of the
`source tracker is to keep track of the positions of each of the
`transmitters as a function of time. This is implemented by
`known nonlinear filtering techniques such as the aforemen(cid:173)
`tioned extended Kalman filter (EKF). In another embodi- 10
`ment, velocities and accelerations of each of the wireless
`units in a particular channel are tracked as well. Inputs to the
`EKF in one embodiment include the DOAs and TOAs from
`the local base station. In another embodiment, DOA and
`TOA measurements from other nearby cell sites also receiv(cid:173)
`ing transmissions from the mobile units are incorporated
`along with known locations of the cell sites to further
`improve the estimation accuracy of the EKF as is well(cid:173)
`known in the art. The tracker 17 4 outputs are sent along with
`the (compressed) data 176 to a spatial demultiplexer con- 20
`trailer 178, to control the function of the spatial demulti(cid:173)
`plexer, and to a spatial multiplexer controller 180 to control
`the function of the spatial multiplexer.
`FIG. 4 shows an alternative embodiment of a wireless
`communications system suitable for implementing the
`present invention. This system is typically coupled to a
`switching network and WAN similarly to the system of FIG.
`1 such as switching network 58 and WAN 56. In FIG. 4, a
`plurality of antennas 103 is used, for example four antennas,
`although other numbers of antennas may be selected. The 30
`outputs of the antennas are connected to a duplexer switch
`107, which in this TDD system is a time switch. Two
`possible implementations of switch 107 are as a frequency
`duplexer in a frequency division duplex (FDD) system, and
`as a time switch in a time division duplex (TDD) system. 35
`When receiving, the antenna outputs are connected via
`switch 107 to a receiver 205, and are mixed down in analog
`by RF receiver ("RX") modules 205 from the carrier fre(cid:173)
`quency (for example around 1.9 GHz) to an FM intermediate
`frequency ("IF") of, for example, 384 kHz. This signal then 40
`is digitized (sampled) by analog to digital converters
`("ADCs") 209 at, for example, 1.536 MHz. Only the real
`part of the signal is sampled. Thus, in complex phasor
`notation, the digital signal can be visualized as containing
`the complex valued IF signal at 384 kHz together with an 45
`image at -384 kHz. Final down-converting to baseband is
`carried out digitally by multiplying the 1.536 megasamples
`per second real-only signal by a 384 kHz complex phasor.
`The result is a complex valued signal that contains the
`complex valued baseband signal plus an image at, for
`example, -2x384=-768 kHz. This unwanted negative fre(cid:173)
`quency image is filtered digitally to produce the complex
`valued baseband signal sampled at 1.536 MHz. GrayChip
`Inc. GC2011 digital filters can be used to implement the
`down-converting and the digital filtering, the latter using 55
`finite impulse response (FIR) filtering techniques. This is
`shown as block 213. The particular frequencies suggested
`above are provided by way of example. The invention can be
`adapted to suit a wide variety of RF and IF carrier frequen(cid:173)
`cies and bands.
`There are, in the present example, four down-converted
`outputs from each antenna's GC2011 digital filter device
`213, one per receive timeslot. The particular number of
`timeslots can be varied to suit network needs. While the
`present example uses four uplink and four downlink
`timeslots for each TDD frame, desirable results have also
`been achieved with three timeslots for the uplink and
`
`6
`downlink in each frame. For each of the four receive
`timeslots, the four down-converted outputs from the four
`antennas are fed to a digital signal processor (DSP) device
`217 (hereinafter "timeslot processor") for further process(cid:173)
`ing, including calibration, according to one aspect of this
`invention. Four Motorola DSP56303 DSPs can be used as
`timeslot processors, one per receive timeslot.
`The timeslot processors 217 perform several functions
`including the following: received signal power monitoring;
`frequency offset estimation and time alignment; smart
`antenna processing including determining weights for each
`antenna element to determine a signal from a particular
`remote user; and demodulation of the determined signal.
`The output of the timeslot processor 217 is demodulated
`15 burst data for each of the four receive timeslots. This data is
`sent to a host DSP processor 231 whose main function is to
`control all elements of the system and interface with the
`higher level processing, which is the processing which deals
`with what signals are required for communications in all the
`different control and service communication charmels
`defined in the system's communication protocol. The host
`DSP 231 can be a Motorola DSP56303. In addition, timeslot
`processors send the determined receive weights to the host
`DSP 231. The main functions of the host DSP 231 specifi-
`25 cally include:
`maintaining state and timing information;
`receiving uplink burst data from the timeslot processors
`217;
`programming the timeslot processors 217;
`processing the uplink signals, including de-encrypting,
`de-scrambling, error correcting code checking, and
`burst deconstruction of the uplink;
`formatting the uplink signal to be sent for higher level
`processing in other parts of the base station;
`formatting service data and traffic data for further higher
`processing in the base station;
`receiving downlink messages and traffic data from the
`other parts of the base station;
`processing of downlink bursts (burst construction, encod(cid:173)
`ing, scrambling and encryption);
`formatting and sending downlink bursts to a transmit
`controller/modulator, shown as 237;
`programming the transmit controller/modulator 237,
`including determining and sending transmit weight
`vectors to the transmit controller/modulator 237;
`controlling the RF controller shown as 233; and
`maintaining and reporting modem status information, and
`controlling synchronization.
`The RF controller 233 interfaces with the RF system,
`50 shown as block 245 and also produces a number of timing
`signals that are used by both the RF system and the modem.
`The specific tasks performed by the RF controller 233
`include:
`producing timing signals for the RF system (RX and TX)
`and other parts of the modem;
`reading transmit power monitoring values;
`writing transmit power control values;
`producing the duplexer 107 switch box control signal; and
`reading automatic gain control (AGC) values.
`the RF controller 233 receives timing parameters and
`other settings for each burst from the host DSP 231.
`The transmit controller/modulator 237, receives transmit
`data from the host DSP 231, four symbols at a time. The
`transmit controller uses this data to produce analog IF
`65 outputs which are sent to the RF transmitter (TX) modules
`245. The specific operations transmit controller/modulator
`237 performs are:
`
`60
`
`Intel, Exhibit 1004
`
`

`

`US 7,158,493 Bl
`
`7
`converting data bits into a complex modulated signal;
`up-converting to an IF frequency using, for example, a
`GrayChip 2011;
`4-times over-sampling the IF signal;
`multiplying this 4-times over-sampled complex signal by
`transmit weights obtained from host DSP 231; and
`converting the real part of the resulting complex valued
`waveforms via digital to analog converters ("DACs")
`which are part of transmit controller/modulator 237 to 10
`analog transmit waveforms which are sent to the trans(cid:173)
`mit modules 245.
`The transmit modules 245 up-convert the signals to the
`transmission frequency and amplify the signals. The ampli(cid:173)
`fied transmission signal outputs are sent to antennas 103 via 15
`the duplexer/time switch 107.
`
`5
`
`8
`user terminal to request a configuration message from the
`base station. They also provide information to guide user
`terminal handover decisions.
`Each broadcast message is mapped into a broadcast burst
`with the information shown below in Table 2.
`
`TABLE 2
`
`Broadcast Message
`
`Field
`
`BStxPwr
`BSCC
`BSload
`
`Total
`
`# of Bits
`
`5
`7
`3
`
`15
`
`25
`
`Broadcast Channel (BCH)
`The system of the present invention is initiated for each
`user terminal or remote terminal from the broadcast channel 20
`BCH which is transmitted as a burst from the base station to
`all potential user terminals. The BCH burst, unlike the traffic
`channel bursts, is transmitted in all directions where user
`terminals may be, typically omnidirectionally but the spe(cid:173)
`cific beam pattern will depend on the network. Accordingly,
`the BCH burst will create more interference on the system
`than spatially directed or lower power traffic channels TCH.
`For this reason, the data and modulation properties of the
`BCH channel are selected to minimize interference. An
`example of a broadcast burst structure is shown in FIG. 5.
`Some of the important BCH burst properties are as follows.
`The BCH is computationally easy to find by scanning in real
`time having no knowledge of time-slot boundaries. It com(cid:173)
`municates enough basic information to enable a subsequent
`exchange of configuration request CR and configuration 35
`message CM between the base station and the user terminal.
`The BCH also provides good frequency offset and timing
`update information to all user terminals, even when the BCH
`is not specifically directed toward any one user terminal in
`particular.
`Table 1, below summarizes the content of an example of
`a BCH burst, as shown in FIG. 5.
`
`BStxPwr is the effective isotropic radiated power of the
`broadcast message. This number indicates the power trans(cid:173)
`mitted by the base station taking into account the number of
`amplifiers and diversity antennas available at the base sta(cid:173)
`tion. For a 10 antenna broadcast channel, base station
`power=(2-BStxPwr+10) dBm.
`BSCC is the base station color code, used by the user
`terminal to select training data for uplink bursts and to
`distinguish broadcasts of different base stations. In one
`embodiment, there are up to 128 different possible color
`30 codes. The color codes can be used to indicate a base station
`in a different location or a different modulator/demodulator
`set in the same location.
`BSload is the load on the base station, used by the user
`terminal to determine how frequently to send random access
`messages. BS load is an indication of the amount of unused
`capacity the base station has. It can be different from the
`number of active registered subscribers because subscribers
`can require different amounts of traffic capacity. BSload
`40 represents the transmit and receive bit rates of each modem
`of the base station over a period of a few minutes measured
`against maximum possible loading.
`In one embodiment, the BCH channel is shared by all base
`45 stations in the wireless communication system. Using the 7
`bit BSCC, up to 128 base stations can be accommodated.
`The BCH is a time division duplex channel with a repeating
`frame. The channel is a single RF carrier frequency used for
`uplink and downlink. For high noise environments or for
`50 increased robustness, the BCH can hop frequencies accord(cid:173)
`ing to a predetermined scheme or be repeated on several
`different frequencies. The repeating frame includes the
`downlink BCH for each base station, labeled BS! etc. as
`The frequency and timing correction training symbols can
`55 shown in Table 3 below. The next frame includes the uplink
`be set according to any one of many approaches well-known
`Configuration Request CR, labeled CR! etc. and downlink
`in the art. They can also be combined, exchanged with a
`Configuration Message CM, labeled CMI etc. Each frame
`synchronization sequence or eliminated.
`also includes a number of reserved slots, shown as empty
`The broadcast information symbols are constructed from
`boxes below. These slots can be used for data traffic, if the
`a 15-bit broadcast message whic