Showing papers by "Qualcomm published in 1995"

Cdma: Principles of Spread Spectrum Communication

Abstract: 1. Introduction. Definition and Purpose. Basic Limitations of the Conventional Approach. Spread Spectrum Principles. Organization of the Book. 2. Random and Pseudorandom Signal Generation. Purpose. Pseudorandom Sequences. Maximal Length Linear Shift Register Sequences. Randomness Properties of MLSR Sequences. Conclusion. Generating Pseudorandom Signals (Pseudonoise) from Pseudorandom Sequences. First- and Second-Order Statistics of Demodulator Output in Multiple Access Interference. Statistics for QPSK Modulation by Pseudorandom Sequences. Examples. Bound for Bandlimited Spectrum. Error Probability for BPSK or QPSK with Constant Signals in Additive Gaussian Noise and Interference. Appendix 2A: Optimum Receiver Filter for Bandlimited Spectrum. 3. Synchronization of Pseudorandom Signals. Purpose. Acquisition of Pseudorandom Signal Timing. Hypothesis Testing for BPSK Spreading. Hypothesis Testing for QPSK Spreading. Effect of Frequency Error. Additional Degradation When N is Much Less Than One Period. Detection and False Alarm Probabilities. Fixed Signals in Gaussian Noise (L=1). Fixed Signals in Gaussian Noise with Postdetection Integration (L>1). Rayleigh Fading Signals (L>/=1). The Search Procedure and Acquisition Time. Single-Pass Serial Search (Simplified). Single-Pass Serial Search (Complete). Multiple Dwell Serial Search. Time Tracking of Pseudorandom Signals. Early-Late Gate Measurement Statistics. Time Tracking Loop. Carrier Synchronization. Appendix 3A: Likelihood Functions and Probability Expressions. Bayes and Neyman-Pearson Hypothesis Testing. Coherent Reception in Additive White Gaussian Noise. Noncoherent Reception in AWGN for Unfaded Signals. Noncoherent Reception of Multiple Independent Observations of Unfaded Signals in AWGN. Noncoherent Reception of Rayleigh-Faded Signals in AWGN. 4. Modulation and Demodulation of Spread Spectrum Signals in Multipath and Multiple Access Interference. Purpose. Chernoff and Battacharyya Bounds. Bounds for Gaussian Noise Channel. Chernoff Bound for Time-Synchronous Multiple Access Interference with BPSK Spreading. Chernoff Bound for Time-Synchronous Multiple Access Interference with QPSK Spreading. Improving the Chernoff Bound by a Factor of 2. Multipath Propagation: Signal Structure and Exploitation. Pilot-Aided Coherent Multipath Demodulation. Chernoff Bounds on Error Probability for Coherent Demodulation with Known Path Parameters. Rayleigh and Rician Fading Multipath Components. Noncoherent Reception. Quasi-optimum Noncoherent Multipath Reception for M-ary Orthogonal Modulation. Performance Bounds. Search Performance for Noncoherent Orthogonal M-ary Demodulators. Power Measurement and Control for Noncoherent Orthogonal M-ary Demodulators. Power Control Loop Performance. Power Control Implications. Appendix 4A: Chernoff Bound with Imperfect Parameter Estimates. 5. Coding and Interleaving. Purpose. Interleaving to Achieve Diversity. Forward Error Control Coding - Another Means to Exploit Redundancy. Convolutional Code Structure. Maximum Likelihood Decoder - Viterbi Algorithm. Generalization of the Preceding Example. Convolutional Code Performance Evaluation. Error Probability for Tailed-off Block. Bit Error Probability. Generalizations of Error Probability Computation. Catastrophic Codes. Generalization to Arbitrary Memoryless Channels - Coherent and Noncoherent. Error Bounds for Binary-Input, Output-Symmetric Channels with Integer Metrics. A Near-Optimal Class of Codes for Coherent Spread Spectrum Multiple Access. Implementation. Decoder Implementation. Generating Function and Performance. Performance Comparison and Applicability. Orthogonal Convolutional Codes for Noncoherent Demodulation of Rayleigh Fading Signals. Implementation. Performance for L-Path Rayleigh Fading. Conclusions and Caveats. Appendix 5A: Improved Bounds for Symmetric Memoryless Channels and the AWGN Channel. Appendix 5B: Upper Bound on Free Distance of Rate 1/n Convolutional Codes. 6. Capacity, Coverage, and Control of Spread Spectrum Multiple Access Networks. General. Reverse Link Power Control. Multiple Cell Pilot Tracking and Soft Handoff. Other-Cell Interference. Propagation Model. Single-Cell Reception - Hard Handoff. Soft Handoff Reception by the Better of the Two Nearest Cells. Soft Handoff Reception by the Best of Multiple Cells. Cell Coverage Issues with Hard and Soft Handoff. Hard Handoff. Soft Handoff. Erlang Capacity of Reverse Links. Erlang Capacity for Conventional Assigned-Slot Multiple Access. Spread Spectrum Multiple Access Outage - Single Cell and Perfect Power Control. Outage with Multiple-Cell Interference. Outage with Imperfect Power Control. An Approximate Explicit Formula for Capacity with Imperfect Power Control. Designing for Minimum Transmitted Power. Capacity Requirements for Initial Accesses. Erlang Capacity of Forward Links. Forward Link Power Allocation. Soft Handoff Impact on Forward Link. Orthogonal Signals for Same-Cell Users. Interference Reduction with Multisectored and Distributed Antennas. Interference Cancellation. Epilogue. References and Bibliography. Index.

Mobile users: to update or not to update?

Abstract: Tracking strategies for mobile users in wireless networks are studied. In order to save the cost of using the wireless links mobile users should not update their location whenever they cross boundaries of adjacent cells. This paper focuses on three natural strategies in which the mobile users make the decisions when and where to update: the time-based strategy, the number of movements-based strategy, and the distance-based strategy. We consider both memoryless movement patterns and movements with Markovian memory along a topology of cells arranged as a ring. We analyze the performance of each one of the three strategies under such movements, and show the performance differences between the strategies.

Reverse link, closed loop power control in a code division multiple access system

Abstract: The process of the present invention enables a mobile radiotelephone to operate at a 100% duty cycle while providing closed loop power control. The base station measures the signal to noise ratio of the signal from the mobile and compares that SNR with the SNR threshold values the base station has for each data rate the mobile is capable of transmitting. The base station then generates power control commands to instruct the mobile to change its power depending on the outcome of the comparisons.

Cell site demodulation architecture for a spread spectrum multiple access communication systems

Abstract: An integrated demodulation processor used in a modem for a spread spectrum communications system despreads multipath receive signals then uses a time sliced transform processor to process the multiple signals in to a single series of soft decision results. The demodulation processor uses a single transform engine which operates on a time slice basis. The output of the processor engine cascade through a pipeline processor which, on a time slice basis, operates on signals corresponding to each multipath receive signal. The processed results are dual maxima decoded to provide soft decision data.

Method and apparatus for controlling power in a variable rate communication system

Abstract: A method and an apparatus for controlling transmission power in a variable rate communication system. A base station (30) monitors the reverse link signal transmitted from a mobile station (50). Base station (30) determines whether mobile station (50) should increase or decrease its power based either upon frame error rates detected by a decoder (44) or by the level of received signal power detected at a receiver (42). In response to this analysis, a control processor (46) generates a power control signal and transmits this signal to mobile station (30).

Wireless network planning tool

Abstract: A novel and improved method and apparatus for planning a wireless telecommunications network. An electronic representation of wireless telecommunications system can be configured within a given market area and the operation of that wireless telecommunications system simulated. The simulation is performed using a set of databases that contain terrain and population information associated with the market area over which the wireless network in configured. To perform the simulation a composite propagation loss matrix and a demand and service vector are generated using the terrain and population information, as well as the configuration of the wireless telecommunications network. Once the composite propagation loss matrix and the demand and service vector are generated an analysis of the reverse link is performed. Subsequently, an analysis of the forward link is performed. During both the reverse and forward link analysis the multiple iterations of analysis are performed until a stable result is achieved. Upon completion of the reverse and forward link analysis, the results of the simulation are displayed in a graphical manner for examination.

Method and apparatus for automatic gain control and DC offset cancellation in quadrature receiver

Abstract: An automatic gain control (AGC) and D.C. offset correction method and apparatus for controlling signal power of a received RF signal within a dual mode quadrature receiver is disclosed herein. The AGC apparatus includes an adjustable gain amplifier (18). A quadrature downconverter (20) coupled to the amplifier (18) serves to translate the frequency of the output signal to a baseband frequency which is offset by a predetermined margin from D.C. Two high gain active lowpass filters (76 and 78) provide out-of-band signal rejection for the baseband signals. A D.C. feedthrough suppression loop supresses D.C. offsets produced by a downconverter (20) and the lowpass filters (76 and 78). The AGC apparatus also generates a received power signal based on the power of the output signal. A saturating integrator compares the received power signal to a reference signal and produces the gain control signal by integrating or by refraining from integration based on values of the reference, received power signal, and gain control signals.

Method and apparatus for performing search acquisition in a CDMA communications system

Abstract: A novel an improved method of acquisition in a spread spectrum communication system is presented. In the present invention, a large window of PN chip offset hypotheses are searched and if an energy signal is found that might indicate the presence of the pilot signal having one of the chip offsets of the large search window, then a search of a subset of offset hypotheses, or small window, is searched.

Method and apparatus for increasing receiver immunity to interference

Abstract: The method and apparatus of the present invention improve the immunity to interference of a radio receiver. The power level of a received signal is detected. If the power level meets or exceeds a predetermined power threshold, the low noise amplifier (703) is by-passed (730), thus increasing the intercept point of the receiver components. Alternative embodiments include the use of an RF power detector (105) to control the front-end gain (110) as a function of jammer power. In lieu of a switchable RF gain block (730), several methods of continuous gain control are proposed. Continuous gain control allows the interference suppression and sensitivity of the receiver to be adjusted at lower signal levels than the switchable gain block. A method of the present invention adjusts the input gain by a predetermined amount (1601). The receiver processing measures the gain change in the IF signal power (1605). If the change is less than the predetermined amount (1610), the CDMA signal and jammers are below the noise floor and, therefore, the gain is increased (1615). If the IF signal power change is greater than the predetermined amount, the interference is evident and the gain is reduced to reduce the intermodulation products (1620). This process is used until the receiver is operating at the best compromise between interference and noise figure.

Method for providing service and rate negotiation in a mobile communication system

Abstract: A method and apparatus for negotiating service configuration in a digital communication system is disclosed. In an exemplary embodiment the service negotiation system is implemented in a wireless spread spectrum communication system. The service configuration comprises data rates, frame formats and types of services. Types of service may include speech encoding, facsimile or digital data services. Further described herein is a digital transmitter and receiver using the service negotiation system to provide service configuration mutually acceptable at both ends of a communication link.

Comprehensive mobile communications device registration method

Abstract: A comprehensive method for mobile station registration in a cellular communication system wherein registrations are made due to multiple stimulus. Registration can occur as a function of distance traveled since the previous registration. Registration can occur due to entering the coverage area of a base station assigned to a zone in which the mobile station has not recently registered. A registration timer can be used to ensure a minimum time between registrations. Registrations can occur at power up and at power down. The mobile station can be ordered to register by a transmission from a base station. Registration can occur due to parameter changes with in the mobile station. Registration may also occur through necessary communication with a base station which is not expressly directed to registration.

Theoretical analysis of the high-rate vector quantization of LPC parameters

Abstract: The paper presents a theoretical analysis of high-rate vector quantization (VQ) systems that use suboptimal, mismatched distortion measures, and describes the application of the analysis to the problem of quantizing the linear predictive coding (LPC) parameters in speech coding systems. First, it is shown that in many high-rate VQ systems the quantization distortion approaches a simple quadratically weighted error measure, where the weighting matrix is a "sensitivity matrix" that is an extension of the concept of the scalar sensitivity. The approximate performance of VQ systems that train and quantize using mismatched distortion measures is derived, and is used to construct better distortion measures. Second, these results are used to determine the performance of LPC vector quantizers, as measured by the log spectral distortion (LSD) measure, which have been trained using other error measures, such as mean-squared (MSE) or weighted mean-squared error (WMSE) measures of LEPC parameters, reflection coefficients and transforms thereof, and line spectral pair (LSP) frequencies. Computationally efficient algorithms for computing the sensitivity matrices of these parameters are described. In particular, it is shown that the sensitivity matrix for the LSP frequencies is diagonal, implying that a WMSE measured LSP frequencies converges to the LSD measure in high-rate VQ systems. Experimental results to support the theoretical performance estimates are provided. >

Remote transmitter power control in a contention based multiple access system

Abstract: The power control process of the present invention enables a base station communicating over a forward packet channel to a mobile radio to control the power of the mobile radio transmitting over a reverse packet channel to the base station. The base station maintains a maximum energy per bit to total interference spectral density ratio threshold for the reverse channel as well as a desired threshold that results in a low frame error rate. By comparing each radiotelephone's estimated energy per bit to total interference spectral density ratio to the desired and maximum thresholds, power control commands to increase or decrease the radiotelephone's transmit power are generated depending on the outcome of the comparison.

Pilot signal searching technique for a cellular communications system

Abstract: An improved method and system for performing a pilot signal searching operation in anticipation of handoff in mobile station (18) communication between base stations (12, 14). The mobile station (18) maintains a list of Active Set pilot signals transmitted from base stations with which the mobile station is to communicate through, and a list of Neighbor Set pilot signals (N) from base stations within a predetermined proximity of the mobile station (18). The searching operation contemplates comparing pilot signal strength measurements corresponding to each base station entry within the Neighbor Set (N) to a first predetermined level. One or more entries from the Neighbor Set (N) having a base station signal strength measurement greater than the first predetermined level may be placed in the Pre-Candidate Set (PC). Tine strength of the pilot signals associated with entries in the Pre-Candidate Set (PC) are then further evaluated to determine eligibility within the Candidate Set (C), from which are selected the entries comprising the Active Set.

Airborne radiotelephone communications system

Abstract: The airborne radio communications system of the present invention enables an airborne radio to communicate with the ground based cellular radiotelephone system. The present invention also enables the ground based system to keep track of the location of the airborne radiotelephone and page it when a call from the ground based telephone system is received. The ground base station is connected to upward radiating antennas that form airborne cells. As the aircraft with the radio flies through the airborne cells, the airborne relay receives the signals from the base station and relays them to the radio. If the radio is transmitting signals, the relay transmits those signals, through the airborne cells, to the base station. As the aircraft moves from cell to cell, the radio is handed off to the next cell to maintain communications with the ground.

Method and apparatus for freight transportation using a satellite navigation system

Abstract: A system and method for assigning hauling vehicles to freight loads within a freight transportation system is disclosed herein. The system includes a satellite navigation subsystem for providing vehicle and load position data useable to determine the locations of each hauling vehicle and freight load. The position data may also be utilized to determine a set of deadhead distances required to be traversed by ones of the hauling vehicles unencumbered with freight loads while en route to load pick-up locations. Each unencumbered tractor vehicle is then efficiently matched with an available freight load in accordance with the compiled sets of deadhead distances and a set of potential pick-up times. Objectives such as punctual load pick-up and delivery, full utilization of available tractor vehicles, and maintaining scheduled driver home-base times of arrival may be achieved through "relay" operations. The term "relay" refers to the process by which an in-transit load is disengaged from a first tractor vehicle and made available at a designated relay location. The disengaged load is then engaged by a second tractor vehicle which becomes available in the vicinity of the relay location within a predefined relay window. In a preferred implementation the loads matched to selected pairs of tractor vehicles may also be exchanged, or "swapped", at a set of swap locations so as to minimize a cost function.

Apparatus and method for controlling transmission power in a cellular communications system

Abstract: An apparatus and method for controlling a final transmit power, y, of a base station in a cellular communications system that has several channels. The base station has a transmit power tracking gain, y', and a radio frequency transmit power, w. The apparatus comprises channel elements for calculating expected powers, P k ,a -P k ,i, each of which corresponds to a channel. The apparatus also comprises a transceiver system controller (BTSC) for generating a desired output power, y d , of the base station, including an adder for summing the expected powers. The apparatus also includes a transmit power detector for measuring y to obtain a measured transmit power. The apparatus further comprises a radio frequency interface card (RFIC) for generating y'. Finally, the apparatus includes a gain unit for processing y' and w to obtain the final transmit power, y.

Adaptive sectorization in a spread spectrum communication system

Abstract: A system and method for adaptively sectorizing channel resources within a digital cellular communication system is disclosed herein. The system includes an antenna arrangement for providing at least first and second electromagnetic beams for receiving a first information signal transmitted by a specific one of a plurality of users, thereby generating first and second received signals. A first set of beam-forming signals are then generated from the first and second received signals. A demodulating receiver is provided for demodulating at least first and second beam-forming signals included within the first set of beam-forming signals, thereby producing first and second demodulated signals. The system further includes a tracking network for tracking multipath information signals, received from various positions and angles of incidence, based on comparison of the first and second demodulated signals.

Reverse link, transmit power correction and limitation in a radiotelephone system

Abstract: The process and apparatus of the present invention limits the output power of a radiotelephone, operating in a cellular system in the preferred embodiment. This ensures the transmitted sidebands and synthesizer phase noise remains within a certain specification. This is accomplished by power detection and a correction accumulator that together generate a gain control signal by limiting the gain adjustment to a maximum value, even when the cell site communicating with the radiotelephone is sending power turn-up commands to the radiotelephone. This process includes dynamically correcting the output level of the transmitter due to gain variations in the transmitter stages or gain control elements.

Method of searching for a bursty signal

Abstract: An integrated search processor used in a modem for a spread spectrum communications system buffers receive samples and utilizes a time sliced transform processor operating on successive offsets from the buffer The search processor autonomously steps through a search as configured by a microprocessor specified search parameter set, which can include the group of antennas to search over, the starting offset and width of the search window to search over, and the number of Walsh symbols to accumulate results at each offset The search processor calculates the correlation energy at each offset, and presents a summary report of the best paths found in the search to use for demodulation element reassignment The search is done in a linear fashion independent of the probability that a signal being searched for was transmitted at any given time

Method and apparatus for diversity enhancement using pseudo-multipath signals

Abstract: Method and apparatus for enhancing diversity in spread spectrum type communication systems by creating pseudo-multipath conditions or links for certain communication signals The invention provides alternative or additional signal paths, for signals being transferred between gateways and communication system users through one or more a satellite repeaters These additional paths are used to establish and maintain adequate signal diversity as well as certain signal links by remote subscribers in heavy urban areas In further aspects of the invention, diversity enhancers can employ high gain parabolic antennas and tracking mechanisms, or passive reflective surfaces Signals can be relayed to subscriber units in canyon type blocked areas or within structures

Method and apparatus for providing mobile unit assisted hard handoff from a CDMA communication system to an alternative access communication system

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.

Generating random bits from an arbitrary source: fundamental limits

Abstract: Suppose we are given a random source and want to use it as a random number generator; at what rate can we generate fair bits from it? We address this question in an information-theoretic setting by allowing for some arbitrarily small but nonzero deviation from "ideal" random bits. We prove our results with three different measures of approximation between the ideal and the obtained probability distributions: the variational distance, the d-bar distance, and the normalized divergence. Two different contexts are studied: fixed-length and variable-length random number generation. The fixed-length results of this paper provide an operational characterization of the inf-entropy rate of a source, defined in Han and Verdu (see ibid., vol.39, no.3, p.752-772, 1993) and the variable-length results characterize the liminf of the entropy rate, thereby establishing a pleasing duality with the fundamental limits of source coding. A feature of our results is that we do not restrict ourselves to ergodic or to stationary sources. >

Layered channel element in a base station modem for a cdma cellular communication system

Abstract: The invention provides a layered channel software element (200) which supervises the operation of channel element modem resources (59) in a CDMA cellular telephone system (8) that includes forward channels (20a, 22a) for conveying message and signalling data from a CDMA system base station (12) to mobile units (16, 18) and reverse channels (20b, 22b) for conveying message and signalling data from mobile units (16, 18) to base stations (12, 14). Each channel is implemented in a channel element (59) including a general purpose processor (60) and a modem application-specific integrated circuit ASIC (62). The layered channel software element (200) executes on the general processor (60). The layered channel software element (200) provides a structure and function for transferring message and signalling data between the telecommunication system (10) and the modem ASIC (62) via channel element controller (44), and also for establishing channel operations by providing channel configuration information to the modem ASIC (62).

Signal acquisition in a multi-user communication system using multiple walsh channels

Abstract: A technique for using energy received by subscriber units over multiple orthogonal channels within a spread spectrum communication system to acquire signal timing by controlling signal amplitude integration intervals used in detecting such timing. Received signals are despread and respective amplitudes integrated over periods that are divisible by factors of 2 into the length of Walsh functions used to generate orthogonal signal channels. Non-coherent combinations of the results of this integration are subsequently formed over periods that commence and terminate on Walsh function boundaries, and used to determine when a correct time offset has been selected for despreading signals. Additional advantages are realized by assigning signals that consistently provide a higher energy content such as paging, synchronization, and most frequently assigned traffic channels to specific orthogonal channels within the communication system. In exemplary embodiments, Walsh functions of length 128 are used as channelizing codes and a pilot signal is assigned to channel 0. This results in traffic channels or paging and synchronization functions being assigned to channel 64 when the integration periods are 64 chips long, and to channels 32, 64, and 96 when the periods are 32 chips long. In this manner, additional energy is available during the integration process for use in determining when correct signal acquisition timing offsets have been selected, without the use of additional hardware.

Method and apparatus for balancing the forward link handoff boundary to the reverse link handoff boundary in a cellular communication system

Abstract: A method and apparatus for matching the location of the forward link handoff boundary to the reverse link handoff boundary. A system constant is chosen which defines the product of the received power and the transmitted pilot power at every base station. The reverse link power level is measured at the base station and the forward link power level is compensated for the reverse link loading to maintain the constant product. Thereby the forward link handoff boundary to the reverse link handoff boundary are aligned to the same location.

Apparatus and method for adding and removing a base station from a cellular communications system

Abstract: An apparatus and method for adding and removing a target base station from a network of base stations, which includes base stations adjacent the target base station. The apparatus is comprised of two attenuators: a first (210) for setting an artificial receive noise power level and a second (218) for setting a transmit level. The transmit level determines the forward link coverage area of the base station. The artificial noise level sets the reverse link coverage area of the base station. When a base station is added, initially the transmit power is low and the artificial receive noise power is high such that the forward and reverse link coverage areas are collocated in close proximity to the base station. As the base station blossoms into full operation, the artificial receive noise power is decreased and the transmit level is increased such that the two coverage areas of the base station remain balanced as the coverage areas expand. When a base station is to be removed from a system, the same attenuators are used to wilt the two coverage areas in unison as the power level transmitted from the base station decreases.

Dynamic sectorization in a spread spectrum communication system

Abstract: A system and method for dynamically varying traffic channel sectorization within a spread spectrum communication system is disclosed herein. In a preferred implementation the system is operative to convey information to at least one specified user in a spread spectrum communication system and includes a pseudorandom code generator (50) for generating, at a predetermined chip rate, a pseudorandom noise (PN) signal of a predetermined PN code. The PN signal is then combined with a first information signal in a spread spectrum transmitter (42) to provide a PN spread information signal. The system further includes at least one additional spread spectrum transmitter (44, 46) each for receiving through a respective delay element (52, 54) delayed versions of the PN signal for providing at least one additional modulation signal. A switching transmission network (74) is disposed to selectively transmit via antennas (85, 86) the first and additional modulation signals respectively to a first and at least one additional coverage area. Selective transmission of the first and the at least one additional modulation signal results in variation in size of a first user sector. The first user sector is associated with a first set of traffic channels, one of which is allocated to the specified user. The system may also be configured to selectively receive, and coherently combine, first and second modulation signals from first and second coverage areas.

Method and apparatus for system determination in a multi-mode subscriber station

Abstract: A method and apparatus for selecting a communication system in a multi-mode subscriber station (1). In the exemplary embodiment, the subscriber station (1) capable of operating in CDMA mode and analog mode comprises an analog modulation and demodulation and processing element (4) and a CDMA modulation and demodulation and processing element (6) and a system determination element (8). System determination element (8) examines exit parameters provided by the communication element excited and determines the next system upon which to attempt acquisition in accordance with a system preferences table (12), a CDMA channel table (10) and a non-volatile memory element (14).

Method for multi-mode handoff using preliminary time alignment of a mobile station operating in analog mode

Abstract: A method for handoff of an analog connection within a cellular communication system which relies upon mobile station synchronization to a system time is disclosed herein. In order to reduce the acquisition time for a mobile station commencing operation in a digital mode, an estimate of master system time is transferred to the mobile station in analog mode before entering digital mode. The alignment operates within the protocols of existing analog systems, and hence requires only minimal changes in the mobile station. Time alignment may be initiated upon the base station sending to the mobile station a command to continually transmit a periodic signaling tone. The base station compares the phase of the signaling tone from the mobile station to a master system clock and determines an error signal. The base station notifies the mobile station to delay or advance in time the transmitted signaling tones based on the error signal. This procedure may continue until the calculated error falls below a predetermined level. Having attained time alignment, the base station is able to transfer to the mobile station absolute time of day information with increased accuracy. The mobile station is then commanded into digital mode where transition time is reduced to a level tolerable by the end user due to the performed alignment.