摘要:
An apparatus for generating an oscillating signal that includes a circuit to accelerate the time in which an oscillating signal reaches a defined steady-state condition from a cold start. The apparatus includes an oscillating circuit to generate an oscillating signal; a first circuit to supply a first current to the oscillating circuit; and a second circuit to supply a second current to the oscillating circuit, wherein the first and second currents are adapted to reduce the time duration for the oscillating signal to reach a defined steady-state condition. The apparatus may be useful in communication systems that use low duty cycle pulse modulation to establish one or more communications channels, whereby the apparatus begins generating an oscillating signal at approximately the beginning of the pulse and terminates the oscillating signal at approximately the end of the pulse.
摘要:
A method and apparatus for performing inter-system hard handoff between communication systems or inter-frequency hard handoff within a CDMA communication system is disclosed. The purpose is to reduce the probability of dropped calls during inter-system hard handoff. In the event that a hard handoff attempt is unsuccessful, the mobile station will return to the original system with information which the communication system of the present invention uses to assist in the performance of future handoff attempts. Alternatively, with no handoff attempt made, the mobile station monitors the destination system then returns to the original system with information used to assist in subsequent handoff attempts. The information returned from monitoring a CDMA system consists of results of a search for one or more pilots given at offsets in a specific list provided to the mobile station by the base station or a set of offsets based upon a predetermined search algorithm.
摘要:
A power control system for controlling the transmission power in a system wherein the transmission power may be gated or capped. The receiver employs a combination of closed loop and outer loop power control. The outer loop is frozen upon detection by the receiver that the signal has been capped or gated.
摘要:
The dual band code division multiple access radio of the present invention operates on multiple frequencies simultaneously on either transmit or receive. The transmit path operates by splitting the transmit intermediate frequency (IF) path (103) and mixing the IF to two different transmit frequencies using two frequency synthesizers (140 and 145). The receive path (104) has two RF channels (116 and 117) that are mixed with the frequencies generated by the synthesizers (140 and 145) and summed into one IF strip. Thus the radio of the present invention can perform a soft hand-off between frequencies while communicating with both base stations simultaneously. Additional mixing paths and synthesizers can be added if it is desired to communicate with more than two base stations simultaneously.
摘要:
A system for mitigating the effect of fading in a digital communication system. Deep signal nulls occur when signals from multiple paths are precisely aligned in amplitude and phase canceling the signal at the receiving antenna and creating a fade. In an indoor system, moving either transmitter or receiver a short distance can shift a fade away from the frequency of interest. This invention provides an actual or perceived movement of an antenna such that the effects of fading can be averaged over a time interval. The signal processing capability of modern digital transceivers can correct errors due to the time varying fades using the present invention. Thus, a dual-antenna element using the system of this invention can provide diversity receive and transmit paths to maintain capacity. The present invention may also provide improved capacity to due enhanced stability in power control.
摘要:
A link quality improvement system for a cellular communication system in which portable units are used to facilitate communication of information signals between system users, via at least one cell-site, using code division multiple access spread spectrum communication signals. The system enables users to improve the quality of reverse communication links from the portable units to the cell-site by providing to each system user a link quality signal indicative of power received at the cell-site relative to an optimum level of received power. At a cell-site communicating with a portable unit associated with a particular system user, the portable unit transmitted power is measured as received at the cell-site. A command signal is generated at the cell-site and transmitted to the portable unit for adjusting portable unit transmitter power. The command signals are also accumulated in order to enable generation of a link quality signal in response thereto. In a preferred implementation the link quality signal is an audible interference signal inducing the system user to adjust orientation of the portable communication unit so as to improve signal quality on the reverse link.
摘要:
A system for mitigating the effect of fading in a digital communication system. Deep signal nulls occur when signals from multiple paths are precisely aligned in amplitude and phase canceling the signal at the receiving antenna and creating a fade. In an indoor system, moving either transmitter or receiver a short distance can shift a fade away from the frequency of interest. This invention provides an actual or perceived movement of an antenna such that the effects of fading can be averaged over a time interval. The signal processing capability of modern digital transceivers can correct errors due to the time varying fades using the present invention. Thus, a dual-antenna element using the system of this invention can provide diversity receive and transmit paths to maintain capacity. The present invention may also provide improved capacity to due enhanced stability in power control.
摘要:
The power control process of the present invention enables a mobile radiotelephone to continuously update the base station on the power output required. The base station sends a frame to the mobile at a particular rate. If the mobile received and decoded the frame correctly, it sets a power control bit in the next frame to be transmitted to the base station. Based on the error rate of the received power control bits, the base station determines whether to increase or decrease the transmit power.
摘要:
A system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signalling along with QPSK spreading.
摘要:
A power control system for a cellular mobile telephone system in which system users communicate information signals between one another via at least one cell site using code division multiple access spread spectrum communication signals. The power control system controls transmission signal power for each cellular mobile telephone in the cellular mobile telephone system wherein each cellular mobile telephone has an antenna, transmitter and receiver and each cell-site also has an antenna, transmitter and receiver. Cell-site transmitted signal power is measured as received at the mobile unit. Transmitter power is adjusted at the mobile unit in an opposite manner with respect to increases and decreases in received signal power. A power control feedback scheme may also be utilized. At the cell-site communicating with the mobile unit, the mobile unit transmitted power is measured as received at the cell-site. A command signal is generated at the cell-site and transmitted to the mobile unit for further adjusting mobile unit transmitter power corresponding to deviations in the cell site received signal power. The feedback scheme is used to further adjust the mobile unit transmitter power so that mobile unit transmitted signals arrive at the cell-site at a desired power level. In a cell diversity situation, the mobile units transmitter power is adjusted to prevent unnecessary increases in mobile unit transmitter power level.