Abstract: A device for wireless, secure transmission of digital information signals utilizing carrier sense multiple access (CSMA) packet communications, or spread spectrum code division multiple access (CDMA) circuits, between a plurality of stations. The device is intended for use within motor vehicles. The digital information signals may be data or compressed voice signals. Each device operates using a visual network access schema under which the operator of each station manually enters, into the device keyboard, the license plate number of the Target vehicle to be contacted. The license plate number of the Target motor vehicle is used by the Sender device to identify the transmission parameters to the Target device. These parameters are the network address, data link address, frequency channel, code division multiple access (CDMA) code, and encryption key. A Target device uses its own license plate number and that of the Sender vehicle to identify the transmission parameters for delivering a response.

Abstract: A phase-locked loop circuit comprises a VCO and a ramp generator. The ramp generator has an output connected to a control terminal of the VCO. A center frequency control loop is connected between a signal output terminal of the VCO and a first ramp control input of the ramp generator and a spread spectrum control loop is connected between the signal output terminal of the VCO and a second ramp control input of the ramp generator. The signals applied to the ramp control inputs of the ramp generator by the two control loops control respective characteristics of a periodic voltage ramp signal that is generated by the ramp generator at its signal output terminal.

Abstract: A method and system, for use in a communication system in which data is transmitted in data frames of a predetermined time duration, for the positioning of the data within the data frames for transmission. A computation circuit computes according to the deterministic code a pseudorandom position for the data within each data frame. A positioning circuit positions the data within each data frame in the computed position.

Abstract: In a code division multiple access (CDMA) spread spectrum cellular communication system in which a mobile station user communicates with another system user via at least one base station, wherein each base station transmits a common pilot signal of a different code phase with respect to other base stations in said system, a method for directing communications between said mobile station user and said base stations. The mobile station monitors the signal strength of pilots and reports the measured signal strength to a system controller via the base station through which it is communicating. Command messages from the system controller to a new base station and the mobiles station establishes communication through the new base station in addition to the communication through the current base station.

Abstract: The technique of redundantly retransmitting digitized voice data on multiple sequential frequencies increases the channel bit rate above the minimum required for normal communication in a frequency-hopping communication system for digitized voice signals. Digitized voice data is redundantly retransmitted on multiple sequential frequencies and the channel bit rate is increased above the minimum required for normal communication. Repeated transmissions of the same block of digitized voice data occurs n times at n times the bit rate of the original digitized voice data. A frequency-hopping transmitter transmits on different channels, or carrier frequencies, which are modulated by the digitized voice data signals from a transmitter data buffer. A receiver data buffer holds n blocks of digitized voice data.

Abstract: The satellite radio communication system of this invention provides communication between one or more service centers and an ensemble of fixed and mobile user terminals. One or more earth orbiting satellites are provided with each satellite having transmitter forming a down-link channel which is slow frequency hopped, and a multi-beam antenna system with a single channel per beam to time division multiple broadcast signals to all user terminals covered by each said beam, respectively. Each user terminal includes a transceiver for receiving a down-link channel broadcast from the one of said beams in whose path it lies, and a return link comprised of a dedicated narrow band broadcast channel with slow frequency hopping of down-link channel. There is a fixed set of frequencies through which the frequency hopping is carried out, with the plurality of fixed and mobile user terminals using the same set of frequency hopping frequencies.

Abstract: A phased array spread spectrum system for maximizing signal strength of a spread-spectrum signal with multipath through the use of receiving means, delaying means, combining means, despreading means, generating means, storing means and comparing means. The receiving means receives a plurality of spread-spectrum signals and a plurality of phased versions of the plurality of spread-spectrum signals. The delaying means delays the received plurality of spread-spectrum signals with respect to the plurality of phased versions of the plurality of spread-spectrum signals by a plurality of delays. The combining means combines the delayed spread-spectrum signals and the plurality of phased versions of the plurality of spread-spectrum signals as a plurality of combined signals. The despreading means despreads the plurality of combined signals as a plurality of despread signals. The generating means generates a plurality of magnitude values from the plurality of despread signals.

Abstract: A method and system, for use in a communication system in which data is transmitted in data frames of predetermined time duration, for the positioning of the data within the data frames for transmission. A computation circuit computes according to the deterministic code a pseudorandom position for the data within each data frame. A positioning circuit positions the data within each data frame in the computed position.

Abstract: A method and corresponding apparatus (10) for generating a pseudo-random number. The method has steps of generating a first bit stream from a number generator (16, 35), combining a predetermined number with the first bit stream to provide a second bit stream and feeding the second bit stream into a feedback port (32) of the number generator (16, 35).

Abstract: A wireless alarm system using spread spectrum transmitters, fast frequency shift keying, spread spectrum receivers and computer with a display. The spread spectrum transmitter includes an oscillator coupled to a microprocessor with chip code generation means, preamble register, address register and data register. The spread spectrum receiver acquires synchronization of the spread spectrum signal using a microprocessor coupled to the quieting, signal strength or baseband output of the receiver, with a two step algorithm. The steps comprise achieving a coarse lock and a fine lock to the spread spectrum signal.

Abstract: A system for encoding and decoding an audio transmission signal comprises: (a) an encoder with a frequency-varying means to vary the carrier frequency of the audio signal according to an encryption algorithm; (b) a transmitter; (c) a receiver; and (d) a decoder with a multi-plexing filter for separating segments of the audio signal with identical carrier frequencies, and a demodulator corresponding to each carrier signal frequency. The separated segments of the audio signal are switched to the corresponding demodulators according to a decryption algorithm.

Abstract: A method and system for providing a reliable means to perform handoff from a code division multiple access (CDMA) system using a pilot signal to an alternative access communication technique system. Simple pilot box circuitry is added to a set of border base stations. The border base stations are base stations which operate only in the alternative access communication technique and which have coverage areas which are contiguous with coverage areas of CDMA operation base stations. The mobile unit monitors for the pilot signal from the border base stations in the same manner as it monitors for pilot signals from the CDMA operation base stations. When the mobile unit detects the pilot signal corresponding to a border base station, it notifies a system controller in accordance with standard operation. The system controller is aware that the pilot signal corresponds to a border base station and thus triggers a hard handoff process to the alternative access communication technique system in response thereto.

Abstract: A method of communicating between two or more radios each capable of transmitting and receiving signals between one another on two or more radio channels wherein the radios hop from channel to channel in a pseudo-random sequence. The method comprises establishing hop synchronization between the radios utilizing a first cycle and operating the radios in a communication mode utilizing a second cycle. The first cycle is shorter than the second cycle so as to facilitate rapid synchronization while preserving the benefits and security obtained through the use of longer cycle length during communication mode.

Abstract: An OCDMA communication system in which channel signals are bandwidth spread according to a PN code and each channel is identified by a selected one of a set of RW code accesses. The set of RW codes is reduced by predetermined one (preferably RW.sub.0). Each transceiver has acquisition and tracking circuitry which search for a null (e.g., the unsent RW access code) falling lower than a predetermined threshold value and synchronizing tracking on detection of the null.

Abstract: A system and method for adaptive power control of a spread spectrum transmitter of a mobile unit operating in a cellular-communications network having a plurality of mobile units in communication with a base station. In response to a received signal from the mobile unit, the received signal having a first spread-spectrum signal and an interfering signal, an automatic gain control (AGC) circuit within the base station generates an AGC-output signal which is despread by base despreader and then processed as a received-power level. The received power level is then compared to a threshold level to generate a power command signal. The power command signal is transmitted to the mobile station as a second spread-spectrum signal. The mobile station despreader despreads the second spread-spectrum signal as a power adjust signal and, responsive to the power adjust signal, increases or decreases the power level of the first spread spectrum signal.

Abstract: The disclosed spread spectrum system has the reference transmitted on one phase (basis vector) of a .pi./2-offset QPSK signal, and the spread data signal transmitted on another phase (basis vector). The two received phases are combined to recover the baseband signal. Such a transmission system is tolerant to multipath dispersion since all delay paths carry an appropriately delayed reference and signal path induced dispersion on the spread data signal is also present on the reference. If one of the two signals is delayed by a predetermined time interval and a corresponding delay is present in each of two cross-coupled signal processing paths following a conventional I-Q demodulator, the resulting two phase quadrature baseband signals may be combined to form a replica of the original baseband signal. The resultant asynchronous demodulation eliminates the usual requirement for carrier lock at the receiver and is therefore tolerant to Doppler shifts and other frequency errors.

Abstract: In this patent, we present MultiCode Direct Sequence Spread Spectrum (MC-DSSS) which is a modulation scheme that assigns up to N DSSS codes to an individual user where N is the number of chips per DSSS code. When viewed as DSSS, MC-DSSS requires up to N correlators (or equivalently up to N Matched Filters) at the receiver with a complexity of the order of N.sup.2 operations. In addition, a non ideal communication channel can cause InterCode Interference (ICI), i.e., interference between the N DSSS codes. In this patent, we introduce new DSSS codes, which we refer to as the "MC" codes. Such codes allow the information in a MC-DSSS signal to be decoded in a sequence of low complexity parallel operations which reduce the ICI. In addition to low complexity decoding and reduced ICI. MC-DSSS using the MC codes has the following advantages: (1) it does not require the stringent synchronization DSSS requires, (2) it does not require the stringent carrier recovery DSSS requires and (3) it is spectrally efficient.

Abstract: A spread-spectrum code division multiple access interference canceler system and method for reducing interference in a spread-spectrum CDMA receiver having N chip-code channels, with each of the N channels identified by a distinct chip-code signal. The interference canceler system comprises a plurality of interference cancelers, each having chip-code generators, delay devices, correlators, spread-spectrum-processing circuits, and subtracting means. Using a plurality of chip-code signals, the correlators despread the spread-spectrum CDMA signal as a plurality of despread signals, respectively. The spread-spectrum-processing circuits use a timed version of the plurality of chip-code signals, generated by the delay devices, for spread-spectrum processing the plurality of despread signals, respectively, with a timed chip-code-signal corresponding to a respective despread signal.

Abstract: A wide area communications network communicating data from a plurality of network service modules through a plurality of remote cell nodes and intermediate data terminals to a central data terminal. The wide area communications network collects network data generated by a plurality of physical devices such as gas, water or electricity meters, located within a geographical area. The wide area communications network is a layered network having a hierarchical communications topology. The central data terminal controls network operation. Intelligence exists at all layers of the network, thereby easing the workload of the central data terminal. The intelligence attributed to each module is a function of the application of that module.

Abstract: A spreading process is performed with a spreading code assigned to each user and a spreading code assigned according to an attribute, and the resultant signal is modulated on the transmitter side. On the receiver side, a transmitted signal, modulated in the above manner, is subjected to a despreading process with the attribute-oriented spreading code from a reception spreading code generator, the resultant signal is subjected to despreading process with the user-specific spreading code from the reception spreading code generator, and those signals which have undergone the despreading processes are demodulated by data demodulators to extract desired information together with a desired signal corresponding to a wide band service. It is therefore possible to simplify the management of the individual users and individual services and facilitate the system design.

Abstract: In a ciphered digital cellular communications system a method and apparatus are presented for selective resynchronization of the cipher upon initial channel acquisition or handoff. Where synchronization between the old channel and the new channel exists, the base station indicates along with an ITCD or handover message that no resynchronization is required. Where synchronization between the old channel and the new channel does not exist, the base station provides an indication along with an ITCD or handover message that resynchronization is required and from the content of this message the manner in which resynchronization is to be achieved is further indicated. By providing options for resynchronization security may be optimized or compromised for handover speed depending upon the specific requirements of the base station or the mobile station.

Abstract: Collisions between messages simultaneously transmitted by multiple spread-spectrum transmitters are reduced by distributing the transmissions over the available resources of the receiver. The transmitters may be mobile stations and the receiver may be a base station in a CDMA cellular telephone system. Each mobile station uses one or more randomization methods to distribute its transmissions. In the first randomization, the mobile station time--delays its transmissions by a number of chips of the PN code with which it spreads the transmitted signal. A hash function produces the number from an identification number uniquely associated with that mobile station. In a second randomization, the mobile station randomly selects the PN code. In a third randomization, the mobile station inserts a random delay between successive message transmissions or probes if it does not receive an acknowledgement after a predetermined timeout period. A predetermined number of such transmissions is called a probe sequence.

Abstract: A system and method for fuzzy spread spectrum communication. The system includes a fuzzy spreader for spreading an input signal over a range of frequencies and fuzzy despreader for extracting the spread input signal from the range of frequencies. In the illustrative implementation, the inventive system a fuzzy pseudo-random generator for use in the fuzzy spreader and the fuzzy despreader. The fuzzy pseudo-random generator uses a novel method for generating pseudo-random numbers. It does not use encryption or decryption techniques. The invention further provides a method for adaptive rule generation and a novel method for identifying the centroid of the set of output numbers. This allows the fuzzy system to learn spreading rules that favor data compression, compact multiplexing, bandwidth conservation, and other communication tasks as well as rules that favor security.

Abstract: There is disclosed a multi channel GPS digital signal processor on a single IC. Each channel contains circuitry to process L1 or L2 P(Y) and C/A-code signals. In addition a search processor is included to achieve fast signal acquisition. Low power adder/accumulators have been designed to provide for a high precision digital oscillator whose output is synchronous to a high speed clock. The IC contains a full low power null detector and eight correlators to aid in signal acquisition.

Abstract: A method and system, for use in a communication system in which data is transmitted in data frames of a predetermined time duration, for the positioning of the data within the data frames for transmission. A computation circuit computes according to the deterministic code a pseudorandom position for the data within each data frame. A positioning circuit positions the data within each data frame in the computed position.

Abstract: In a one embodiment of a spread spectrum communication system, an unmodulated synchronization wavetrain and one or more modulated intelligence wavetrains are generated in timed relation and are concurrently propagated but separately detected in a receiver. In another embodiment, wavetrains are modulated by opposite phases of an intelligence signal and so detected in a receiver as to produce a synchronization control signal and an intelligence signal by summing and comparing two received signals. Under microprocessor control, the phase of operation of the sequence generators of the receiver is adjusted to obtain phase and frequency information for effecting phase control for synchronization and also to controllably swallow cycles and accurately adjust the effective frequency of the clock signal.

Abstract: A communication system (100) operates on a system acquistion channel, and a set of communication channels organized into a sequence (200) which includes a set of reservation channels (202, 204) selected from the sequence (200). The system (100) includes a communication unit (113) which initiates communications by selecting one of the reservation channels (610), and by executing a collision detection protocol on that reservation channel (620). When no collision is detected, the initiating communication unit transmits, on the system acquisition channel, call information, including information for another reservation channel selected from the reservation channels (530).

Abstract: A spread spectrum open loop data recovery processor receives a single information channel bi-phase modulated RF signal and combines it with a locally generated fixed frequency signal having an accuracy of at least 5 ppm. A balanced demodulator combines the received and local signals to derive an `I` and a `Q` analog information signal. The remote transmitter modulates both channels with the same information. The `I` and `Q` analog signals `slip` with respect to one another. The accuracy of the fixed frequency signal insures that the rate of slip does not exceed the ability of the data recovery processor to attain an error rate of better than 1 ppm. The `slip` results in both analog signals periodically going through null. The quadrature phase relationship between the `I` and `Q` analog signals insures that both are not simultaneously null. An amplitude comparator determines which analog signal has the greater instantaneous amplitude.

Abstract: An efficient apparatus for performing frequency conversion from a final IF frequency to a baseband frequency is described. A counter (401) generates two logical signals G1 (402) and G2 (403) which are passed to an exclusive-OR gate (404) and a multiplexer (406). When a control signal (411) is deasserted, multiplexer (406) passes signal G1 to I1 and signal G2 to I2; when control signal (411) is asserted, multiplexer (406) passes binary signal G1 to I2 (410) and signal G2 to I1 (407). Similarly, multiplexer (405) swaps its input real and imaginary samples when the output of exclusive-OR gate (404) is asserted; otherwise, it performs no operation on its input samples. Signals I1 (407) and I2 (410) are used to control arithmetic inverters (408) and (409) respectively. When the controlling signal for either inverter is asserted, the inverter performs arithmetic inversion, otherwise it performs no operation.

Abstract: A multicarrier direct sequence spread spectrum system and method. A maximal combiner is employed at the receiver for maximizing signal-to-noise ratio out of the receiver. The multicarrier system provides robustness against multipath fading, and narrowband interference suppression. The multicarrier system is suitable for a CDMA overlay scheme for PCN.

Abstract: Signaling is inserted (102) into a communication channel of a communication system by inserting the signaling into the communication channel if the communication channel has sufficient available bandwidth (104). If the communication channel does not have sufficient available bandwidth, reducing the bandwidth of information being communicated on the communication channel (106) and inserting the signaling into the communication channel (108) with reduced information bandwidth.

Abstract: The present invention is for fast, reliable recognition of coded signals where the signal includes a predetermined code sequence in a lead portion thereof. This has particular application in spread spectrum transmission and receptions. The code sequence is a long sequence of bits known to the receiver which breaks the long sequence into a series of bit segments which are more easily analysed. Each series of bits is analysed for a direct match and a decision whether a code segment has been received is based on the number of direct matches. For example, if there are 8 bit segments, each 16 bits in length, high reliability has been achieved if two direct matches are received within a time period corresponding t the transmission time of the code sequence. This system can also be used for assessing signal strength where many matches indicate good signal strength, approximately 50% indicates moderate signal strength, and less indicating poor signal strength.

Abstract: A communication system utilizes multiple spreading codes to transmit high data rate information. The system codes high data rate user information (201) and partitions the coded information (202) into blocks comprised of two bits, B1 and B2. Based on the representation of bits B1 and B2, the system chooses one of a possible four spreading codes (W.sub.1 and W.sub.2 and their phase reversals W.sub.1 ' and W.sub.2 ') to be utilized for transmission. Once received, the transmitted signal is input into correlators (306, 309) specific to each spreading code W1 and W2, and the maximum absolute value output from the correlators (306, 309) is determined. From this determination, the transmitted spreading code W.sub.1, W.sub.2, W.sub.1 ' or W.sub.2 ' is determined. The use of multiple spreading codes allows the for the transmission of high data rate information without altering the wireless air interface of the communication system.

Abstract: In quantizing a digital signal in respective frequency bands by quantization units and transmitting (transmitting or recording) such quantized digital signal, second quantization accuracy information indicating a difference between first quantization accuracy information serving as a reference and actual quantization accuracy information from a quantization accuracy determination unit is coded at a quantization accuracy information coding unit to transmit the coded quantization accuracy information to thereby realize efficient coding while maintaining a degree of freedom in the manner of giving quantization accuracy. Accordingly, more efficient coding can be attained while leaving the degree of freedom in the manner of giving quantization accuracy by a lesser number of bits.

Abstract: A method for prioritizing data transmissions in a frequency hopping communication system (10) includes defining a predetermined number of time slots at the beginning of a dwell or end of a transmission, each time slot having a duration and a data type, the communication device attempting to transmit data if the data type of the data corresponds to the data type of the slot, the attempt being based on at least one of the first and second assigned probability of transmission values, assigning the second probability of transmission value to the communication device if the attempt succeeds, reassigning the first probability of transmission value to the communication device if the transmission of data is complete.

Abstract: A cordless, battery-operated telephone of relatively low power consumption suitable to operate in license-exempt spectrum and which may employ an established communication protocol, such as the CT-2 communication protocol, is realized by providing a direct sequence spread spectrum (DSSS) modulator/spreader and demodulator/despreader in a battery-operated handset in connection with an intelligent CT-2 controller to which is added additional circuitry and functionality in the handset for acquiring, pulling-in and tracking, in both operational and low-power-consumption standby modes, a received DSSS signal from a base station unit.

Abstract: A communication unit for use in a communication system is provided which includes a hopping mechanism which hops communication frames over a plurality of carrier frequencies according to a predetermined hopping pattern. At least one of the communication frames preferably includes a synchronization channel time slot having data bits from which the predetermined hopping pattern may be derived. In addition, a communication unit is provided which includes a signal acquisition mechanism for initially acquiring a predetermined hopping pattern that specifies the sequence over which hop frames are hopped over a plurality of carrier frequencies. Also, this communication unit includes a hopping mechanism for hopping receiving frequency according to the predetermined hopping pattern such that a control channel may be detected. In an alternative embodiment, either communication unit may derive the predetermined hopping pattern from detected global position satellite information.

Abstract: Methods and systems for jointly demodulating CDMA signals are presented. The disclosed methods and systems provide, among other advantages, for accurate demodulation of such signals in multipath, time-dispersion environments. Single signal or multiple signal demodulation, with or without taking intersymbol interference into account can be accomplished according to the present invention.

Abstract: In a digital communication system in which digital data is transmitted in data frames of a preselected time duration, a method and apparatus for formatting digital data in each data frame. A set of data bits of a first data type having a bit count corresponding to one of a plurality of predetermined bit counts are provided. A set of parity check bits for the set of data bits of said first data type are generated when the bit count is a highest bit count or a next to highest bit count. A set of tail bits is generated in accordance with a predetermined frame termination format. In respective order the set of data bits of the first data type, the parity check bits, and the tail bits are porovided in a data frame if the bit count is of the highest bit count or of the next to highest bit count. Otherwise, the set of data bits of the first data type and the tail bits are provided in respective order in the data frame.

Abstract: An apparatus including an antenna and amplifier for receiving and amplifying a spread spectrum signal, at least two correlators for determining the correlation levels of the received signal with respect to the correlators corresponding code sequences, and a comparator for comparing the output levels of the two correlators. A signal detector is operably connect to the correlators for determining when a code sequence has been detected on one of the correlators. A phase-locked loop is controlled by the output of the signal detected unit and triggers a sample and hold device which samples the output of the comparator. A device is also provide to output the decoded data which is held on the sample and hold device.

Abstract: An apparatus for decoding a received spread spectrum signal having a data signal modulated with a pseudo-noise code and transmitted as an RF spread spectrum signal. A first reference register holds a first pseudo-noise signal, a second reference register holds a second pseudo-noise signal, and a receive-register holds a received spread spectrum signal. A first modulo adder adds each chip of the received spread spectrum signal with each respective chip of the first pseudo-noise signal, thereby generating a first plurality of chip-comparison signals. A first summer adds the first plurality of chip-comparison signals, generating a first correlation signal. The comparator compares the correlation signal to an upper-threshold level and a lower-threshold level, and respectively generates a first data-symbol signal or a second data-symbol signal.

Abstract: A spread spectrum communication system includes a receiving section which receives a signal produced by modulating a carrier of a predetermined frequency with a spread spectrum signal which has been modulated with a spread code of a clock frequency fC and mixes the received signal with a local oscillation signal to provide a spread spectrum signal component wherein a local oscillation frequency fL of said local oscillation signal is set at fL.apprxeq.fC+fo or fL>fC+fo or fL.apprxeq.fo-fC or fL<fo-fC where fo represents frequency of said received signal. The received signal may be a signal which has been converted to an intermediate frequency signal after being received by the receiving section. The spread spectrum communication system can prevent a spread spectrum signal from being impaired due to variation in a transmission frequency or oscillation frequency in a receiving section and can thereby accurately demodulate the received signal.

Abstract: A system for accessing a telephone system, in which a set of user stations are matched with a set of base stations for connection to a telephone network. Each base station may be coupled directly or indirectly to the telephone network and may be capable of initiating or receiving calls on the telephone network. Each user station may comprise a spread-spectrum transmitter or receiver and may be capable of dynamic connection to selected base stations. A plurality of base stations may be coupled to a private exchange telephone system for coupling user stations in calls outside the telephone network. User stations may use CDMA, FDMA, TDMA or other multiple-access techniques to obtain one or more clear communication paths to base stations. Base stations may be placed at convenient locations or may themselves be mobile. User stations may make and break connections with base stations as the user station moves between service regions, or is otherwise more advantageously serviced by, base stations.

Abstract: An improved system and method for transmitting information within a digital communication system is disclosed herein. A modulation system for use in a digital cellular communication system is described in which information is exchanged among a plurality of mobile users, via at least one cell-site, using a set of orthogonal binary codes. The modulation system allows the information carrying capacity of signal transmission on the mobile-to-cell communication link, i.e., the "reverse" link, of the communication system to be significantly improved. The modulation system receives an input information signal an generates an orthogonal sequence signal in response thereto. The orthogonal sequence signal corresponds to a selected one of a plurality of orthogonal binary chip sequences derived from a set of orthogonal binary codes. The orthogonal binary sequences are constructed such that a selected chip at a predefined sequence position within each of the orthogonal binary sequences is of the same binary value.

Abstract: The secure communication keying system has a noise generator whose output a predetermined finite band of noise within, for example, the zero to eleven hundred cycle per second range. The noise generator may be a pseudorandom noise generator that is synchronized with a given clock frequency. The output of the system may have noise-like characteristics, but it is encoded with any type of intelligence desired to be transmitted. The output signals simulate the ambient noise occurring within the communication medium and has the same frequency spectrum regardless of the frequency of the modulating signals supplied thereto.

Abstract: Transmission is controlled using the present method after a handoff procedure has been entered between a subscriber unit and target transceivers. During this process, a communication link between the subscriber and at least one other transceiver is maintained. A quality factor of a signal from the subscriber is received by the target transceiver. If the quality factor meets a quality threshold, then a transmission from the target transceiver is activated. If the target transceiver is active and the quality factor drops below the quality threshold, then the transmission from the target transceiver is terminated.

Abstract: A transmitter (12) broadcasts a PN encoded message (16). A receiver (14) includes a SAW correlator (38) configured to autocorrelate with the PN sequence used in the broadcast signal. A preamble of the message (16) conveys two successive bits (18) that are each encoded with the PN sequence. After the correlator (38) has been preloaded with the PN sequence from the first bit (18), its non-correlation output exhibits reduced amplitude time sidelobes. A timing comparison circuit (60) compares a correlation signal (46) with a timing threshold (72). The timing threshold (72) is established at a very low level to minimize the influence of multipath. False triggering on noise is prevented by disabling the timing comparison circuit (60) until after the first bit (18). At this point in time the correlator (38) has been preloaded with its PN sequence, is again being loaded with its PN sequence, and outputs reduced amplitude time sidelobes.

Abstract: A spread spectrum communication system for direct sequence transmission of digital information having a modulation format which is particularly suitable for indoor communication within residential, office and industrial structures. The modulation format combines BPSK or MSK spreading with FM carrier modulation by data bits and a carrier frequency shift whose magnitude is related to both a chip rate and a spreading sequence length. The carrier, chip clock and data clock are all synchronous and the sequence length is an integral submultiple of the bit length. The system reduces the frequency error between the transmitter chip clock and the receiver chip clock to permit the elimination of a code phase tracking loop in the receiver to reduce the receiver complexity. The receiver has an extended dynamic range which makes possible the reception of very strong signal without an automatic gain control loop (AGC) as well as reducing the time needed for code phase acquisition.

Abstract: A code-division multiplexed system comprising an optical source, a code generator for developing and applying a pseudo-random bit sequence code to the optical source to cause the optical source to develop a unipolar coded optical signal, a means for dividing the unipolar coded optical signal into N optical paths separated from each other by associated successive integer multiples of a bit period T of delay, N information signal sources responsive to the unipolar coded optical signals for selectively producing N differently-delayed optical information signals, a means for combining the N differently-delayed optical information signals into an output optical signal comprised of an intensity sum of the overlapping N differently-delayed optical unipolar information signals, a photodetector responsive to the output optical signal for developing an input electrical signal corresponding to the sum of N overlapping unipolar optical signals, an adjustable delay circuit responsive to the pseudo-random bit sequence code

Abstract: A spread spectrum communication system for direct sequence transmission of digital information having a modulation format which is particularly suitable for indoor communication within residential, office and industrial structures. The modulation format combines BPSK or MSK spreading with FM carrier modulation by data bits and a carrier frequency shift whose magnitude is related to both a chip rate and a spreading sequence length. The carrier, chip clock and data clock are all synchronous and the sequence length is an integral submultiple of the bit length. The system reduces the frequency error between the transmitter chip clock and the receiver chip clock to permit the elimination of a code phase tracking loop in the receiver to reduce the receiver complexity. The receiver has an extended dynamic range which makes possible the reception of very strong signal without an automatic gain control loop (AGC) as well as reducing the time needed for code phase acquisition.