摘要:
Ghosts are canceled in received analog TV (for IDTV, EDTV, and HDTV) signals by utilizing the fact that there are short periods of time without the analog signals (the horizontal flyback interval between the lines) to process the received signal on a line-to-line basis using a finite impulse response (FIR) or an infinite impulse response (IIR) equalizer. This line-by-line processing (which can be implemented by periodic cleansing of the equalizer) overcomes the limitations of standard equalizers to allow for 40-50 dB of suppression of ghosts, even with nulls in the spectrum, as long as the ghost delay is less than the period of time without the analog signal. Furthermore, by using time inversion in combination with line-by-line processing, the stability problem of the conventional IIR equalizer is eliminated. The IIR equalizer may be implemented on a single digital integrated circuit. Alternatively, an FIR equalizer can be used which, although it may require multiple chips (i.e., more taps), can acquire and adapt to the ghosted channel more rapidly than an IIR equalizer. With line-by-line processing, FIR and IIR equalizers can eliminate any ghost with delays up to 11 .mu.sec in IDTV or EDTV. For larger delays, a standard IIR or FIR equalizer can be used as a preprocessor to eliminate small ghosts and an adaptive antenna can be used to eliminate large ghosts. Thus, with these techniques, the ghosting problem can be eliminated in all TV receivers.
摘要:
Signal distortion in fiber optic systems is compensated for by forming decisions as to the transmitted information as a joint function of the received signal and of a feedback signal. The latter, in turn, is a function of decisions made for at least one signal transmitted over the fiber. The feedback signal determines the value of a threshold to which the received signal is compared in order to generate the decisions.
摘要:
A method for establishing wireless communication between a transmitter and a receiver in a wireless communication system is disclosed. The receiver includes an adaptive array that has at least two antennas. Each antenna receives a signal and produces a received signal. The transmitter includes at least two transmission channels for communicating the signal from the transmitter to the receiver. The wireless communication system suppresses interference at the receiver by applying an interference suppression technique when combining the received signals. The selection of a channel at the transmitter is based on the channel performance at the receiver for each transmission channel. The channel performance is based on a combining technique different from the interference suppression technique.
摘要:
A method for establishing wireless communication between a transmitter and a receiver in a wireless communication system. The receiver includes an adaptive array that has at least two antennas. Each antenna receives a signal and produces a received signal. The transmitter includes at least two transmission channels for communicating the signal from the transmitter to the receiver. The wireless communication system suppresses interference at the receiver by applying an interference suppression technique when combining the received signals. The selection of a channel at the transmitter is based on the channel performance at the receiver for each transmission channel. The channel performance is based on a combining technique different from the interference suppression technique.
摘要:
A multiplicity of baseband input signals are supplied to a signal processor which functions to modify the input signals such that when the modified signals modulate corresponding multiple carrier wave signals which are combined to produce a composite signal which is applied to the input of an amplifier, the "peaking" at the input to the amplifier and the resultant intermodulation at the output of the amplifier are reduced. In response to the application of the baseband input signals, the signal processor determines the extent of peaking and modifies at least one of the phase and amplitude of the input signals. In one embodiment of the invention, a block of data representing the input signals over a time slot is supplied to the signal processor which then generates a fixed phase shift over the time slot. In another embodiment of the invention, a block of data representing input signals is applied to a signal processor which then determines the worst case peaking and the time of their occurrence. The signal processor then generates phase shifts which change very gradually, thereby reducing sharp peaking at the input to the amplifier at selected times without significantly distorting the signal.
摘要:
Described technologies are generally related to predicting future mobile device locations and using the predictive information to optimize mobile communications service parameters. Mobile device locations may be predicted using real-time device location information, destination information, and location history. Predicted location information for a given device, and possibly other devices as well, may be used to adjust mobile communications service parameters such as handoffs, channel assignment, multipath fading response parameters, data rates, transmission modes, opportunistic scheduling parameters, location-based services, and location update rates.
摘要:
The present invention relates to a wideband communication network using wireless radio transmissions either on a stand-alone basis or to supplement a hard-wired network. The exemplary network comprises (a) a plurality of transceivers associated with separate users of the network; (b) optionally at least one concentrator associated with certain separate subgroups of wireless and possibly hard-wired transceivers for providing duplex operation; and (c) a central node (i) capable of providing both duplex communications directly via a radio channel using radio links with certain subgroups of the transceivers and via a hard-wired connection with each optional concentrator, and (ii) for polling the needs of all transceivers and directing all packets of information from active transceivers through the central node and to the destined transceivers during each frame period. The network also preferably includes diversity and resource sharing techniques to provide added protection against channel impairments on an as-needed basis.
摘要:
A wireless PBX or LAN system is disclosed that allows multiple, simultaneous users per channel for communication between a base station and a plurality of remote terminals by a combination of adaptive signal processing arrays using optimum combining at the base station for interference suppression and separation of desired signals, adaptive power control at the remote terminals to keep interference at acceptable levels, and adaptive retransmission with time division in the direction from the base station to the remote terminals for communication therebetween including sending power control information to the remote terminals. The adaptive signal processing arrays have a plurality of antennas at the base station, permitting a plurality of users in any one channel. If after adaptation a user's signal cannot be received adequately, the user is dynamically reassigned to a different channel. Interference is minimized by keeping the signals transmitted from and received at the base station at the same power level. The received signals are kept at the same power level by extracting information about the power level of the signals received at the base station and by sending power control bits back to the corresponding remote terminal so that the signal level from the remote terminal may be adjusted either up or down until the power level of each of the signals received at the base station is at the same level. The transmitted signals are kept at the same power level by adaptive retransmission with time division.
摘要:
A method for establishing wireless communication between a transmitter and a receiver in a wireless communication system is disclosed. The receiver includes an adaptive array that has at least two antennas. Each antenna receives a signal and produces a received signal. The transmitter includes at least two transmission channels for communicating the signal from the transmitter to the receiver. The wireless communication system suppresses interference at the receiver by applying an interference suppression technique when combining the received signals. The selection of a channel at the transmitter is based on the channel performance at the receiver for each transmission channel. The channel performance is based on a combining technique different from the interference suppression technique.
摘要:
A method for establishing wireless communication between a transmitter and a receiver in a wireless communication system is disclosed. The receiver includes an adaptive array that has at least two antennas. Each antenna receives a signal and produces a received signal. The transmitter includes at least two transmission channels for communicating the signal from the transmitter to the receiver. The wireless communication system suppresses interference at the receiver by applying an interference suppression technique when combining the received signals. The selection of a channel at the transmitter is based on the channel performance at the receiver for each transmission channel. The channel performance is based on a combining technique different from the interference suppression technique.