摘要:
A communication system that allows a soft handoff to be completed, even when the communications link between the active base station and the mobile station deteriorates before the mobile station has received the handoff direction message. The mobile station maintains a list of base stations that the mobile station is in communication with, referred to as an “Active Set”. In addition, the mobile station maintains another list of base stations that are proximate to the base stations in the active set. This list is referred to as the “Neighbor Set”. In accordance with the disclosed method and apparatus, the mobile station places a base station in the active set upon including the base station in a pilot strength measurement message (PSMM). The mobile station monitors transmissions from all of the base stations on the active set to receive a handoff direction message (HDM).
摘要:
Operating a communication device in a half-duplex mode using only overhead channels; and substantially free running a timing reference obtained during reception to allow a timing reference value to drift during transmission.
摘要:
A method and apparatus for providing soft handoff in a mobile communication system. In current systems is that the members of active set are determined in accordance with comparisons of measured pilot energy with fixed thresholds. However, the value of providing a redundant communication link to a mobile station depends strongly on the energy of other signals being provided to the mobile station. In the present invention, the signal strengths of other base stations in communication with a mobile station are considered when determining whether adding a base to that set of base stations in communication with the remote station is of sufficient value to justify the impact on system capacity.
摘要:
A system and method is taught for controlling a power level of transmissions in a communication system. A first station of the communication system transmits signals on a communication channel and a pilot channel. A second station of the communication system measures a signal to noise ratio of the received signal, determines an expected signal to noise ratio of the received signal, determines an indicator in accordance with said measured signal to noise ratio and the expected signal to noise ratio, and transmits the indicator. The indicator is received at the first station the indicator and determines the power level of the next transmission according to said received indicator. Additionally, methods and systems for the measurement of the signal to noise ratio of the received signal, the determination of the expected signal to noise ratio of the received signal, and the determination of the indicator are disclosed.
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 exemplary embodiment, transmit power of mobile unit signals is controlled based on signal power received by the mobile unit and power adjustment commands sent to the mobile unit.
摘要:
Collisions between messages simultaneously transmitted by multiple spread-spectrum transmitters are reduced by distributing the transmissions over the available resources of the receiver. Each mobile station in a CDMA system 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. 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. In a fourth randomization, the mobile station inserts a relatively long random delay between successive probe sequences if it does not receive an acknowledgement of any probe in the sequence.
摘要:
A wireless packet data communications system that includes a number of modem pool transceivers (MPTs), one or more modem pool controllers (MPCs), and one or more servers. Each MPT receives and processes data packets to generate a modulated signal (e.g., a CDMA spread spectrum signal) suitable for transmission over a terrestrial communications link. Each MPC provides call related processing for one or more MPTs. The servers couple to the MPTs and MPCs via an Internet Protocol (IP) back-bone and provide management of the communications system. The IP back-bone further interconnects the MPTs with one or more data networks and includes a number of routers that route data packets between the data networks and the MPTs. Each MPT can couple to two or more routers for redundancy. Each MPT is operated as an element in an IP network and is associated with an IP address that identifies the MPT. One to three MPTs can be deployed at each cell site to provide wireless data service coverage for up to three sectors at the cell site. The MPCs can either be centralized and coupled to the MPTs via the IP back-bone or distributed about the communications system.
摘要:
The character of the noise in a series of incoming symbols received over a wireless link is determined. A series of corresponding bits are recovered based upon the series of incoming symbols. The series of corresponding bits are encoded to determine a series of recovered symbols. A vector product of the series of incoming symbols and the series of recovered symbols is determined. A difference between two symbols within the vector product is determined, wherein the two symbols were transmitted over the wireless link in close temporal proximity to one another. The expected value of a non-orthogonal noise portion of the series of incoming symbols is determined based upon an expected value of the difference between the two symbols.
摘要:
Techniques to improve the acquisition process in a spread spectrum environment. The signals from different CDMA systems are spread with different sets of PN sequences, with the PN sequences in each set being uncorrelated to the PN sequences in the other sets. By using uncorrelated PN sequences, the likelihood of detecting a pilot signal from an undesired system is reduced or minimized, and the mean time to acquisition of the pilot signal from the desired system is improved. The mobile station can attempt to acquire the pilot signal by processing the received signal with a first set of PN sequences corresponding to a first hypothesis of the particular signal being acquired. If acquisition of the pilot signal fails, a second set of PN sequences corresponding to a second hypothesis is selected and used to process the received signal. The PN sequences in the second set are uncorrelated to the PN sequences in the first set. The PN sequences for the first set can be generated based on the characteristic polynomials defined by IS-95-A, and the PN sequences for the second set can be the reverse of the PN sequences for the first set.
摘要:
In one embodiment of method and appartus for determining loading in a communication system, the communication system accumulates a power control commands series and corresponding transmit gain adjustments series between a base station and a designated remote station, under regular operating conditions. After transmissions form the remaining remote stations are interrupted, the communication system repeats the accumulation, and determines the loading according to the accumulated series. Alternatively, the communication system measures power of a test signal injected into base station receiver, under regular operating conditions. After transmissions form the remote stations are interrupted, the communication system repeats the measurement, and determines the loading according to the two measurements. Alternatively, the communication system measures gain of an AGC at the base station's receiver, under regular operating conditions. After transmissions form the remote stations are interrupted, the communication system repeats the measurement, and determines the loading according to the two measurements.