179 results about "Time diversity" patented technology

An adaptable orthogonal frequency-division multiplexing system (OFDM) that uses a multiple input multiple output (MIMO) to having OFDM signals transmitted either in accordance with time diversity to reducing signal fading or in accordance with spatial diversity to increase the data rate. Sub-carriers are classified for spatial diversity transmission or for time diversity transmission based on the result of a comparison between threshold values and at least one of three criteria. The criteria includes a calculation of a smallest eigen value of a frequency channel response matrix and a smallest element of a diagonal of the matrix and a ratio of the largest and smallest eigen values of the matrix.

Systems, methods, apparatus are provided for providing to a receiver a time diverse digital signal corresponding to a service including receiving a digital signal containing a service content and receiving a digital signal containing a non-deterministic content. The service content is inserted into a first predetermined number of data packets in a first predetermined number of data frames deterministically. In addition, a first portion of the non-deterministic content is inserted into a second predetermined number of data packets in the first predetermined number of data frames. A copy of the first predetermined number of data packets is generated. The first predetermined number of data frames is broadcast over a distribution network. The copy of the first predetermined number of data packets is inserted into a second predetermined number of data frames and a second portion of the non-deterministic content is inserted into the second predetermined number of data frames. The second predetermined number of data frames is broadcast after a predetermined time.

The present system comprises a transmitting apparatus for digital broadcast which includes an original signal generating section, delaying section, information amount reducing section, and transmitting section. A receiving and reproducing apparatus for digital broadcast includes a signal reception front stage unit for receiving a high quality signal and a low quality signal, mode determining section and reproducing section composed of a delaying section and selecting section for selectively reproducing the high quality signal and the low quality signal. By employing time diversity, the transmitting apparatus sends the low quality signal having a smaller bandwidth and the high quality signal so that the low quality signal has a preceding time lag relative to the high quality signal, and the receiving apparatus reproduces broadcasting programs. Utilizing the frequency band for broadcast effectively, many broadcasting programs can be increased, and the investment for providing a gap filler can be minimized.

A satellite system employing time diversity and a single frequency network of terrestrial re-radiation stations is provided wherein each terrestrial re-radiation station inserts a delay into a terrestrial signal. The delay allows the time of arrival of the early time diversity signal at the center of terrestrial coverage to coincide with the arrival of the corresponding late time diversity signal, thereby improving hand-off between terrestrial and satellite signals at a receiver. The delay also adjusts for distance differences between each terrestrial re-radiation station and the satellite and between each station and the center of the terrestrial coverage region. This adjustment optimizes the TDM-MCM reception by synchronizing at the center of the SFN the phase of the MCM signals re-radiated from the re-radiating stations of the SFN. The delay also compensates for the processing delay encountered when converting a satellite LOS TDM stream into a multicarrier modulated stream for transporting the satellite LOS TDM stream to user receivers and for the diversity delay between the early and late signals.

A method of transmission in a wireless communication system having a transmitter and a receiver. In the transmitter: signals are encoded using a space-domain precoder for spatial multiplexing, time-domain variable delay is introduced at each signal communication path for time diversity, and the signal are transmitted to the receiver. In the receiver the signal transmissions from the transmitter are decoded using a space-domain decoder, wherein time diversity and spatial multiplexing are combined, to increase communication robustness and spectral efficiency.

A process (111,101) of sending packets of real-time information at a sender (311) includes steps of initially generating at the sender the packets of real-time information with a source rate (s11) greater than zero kilobits per second, and a time or path or combined time / path diversity rate (d11), the amount of diversity (d11) initially being at least zero kilobits per second. The process sends the packets, thereby resulting in a quality of service QoS, and optionally obtains at the sender (311) a measure of the QoS. Rate / diversity adaptation decision may be performed at receiver (361′) instead. Another step compares the QoS with a threshold of acceptability (Th1), and when the QoS is on an unacceptable side of said threshold (Th1) increases the diversity rate (d11 to d22) and sends not only additional ones of the packets of real-time information but also sends diversity packets at the diversity rate as increased (d22). Increasing the diversity rate (d11 to d22) while either reducing or keeping unchanged the overall transmission rate (sij+dij) is an important new improvement in even solely-time-diversity embodiments. In another form of the invention a single-chip integrated circuit includes a processor circuit (1511), and a rate-and-diversity control (1561). Here again, the diversity is contemplated to be time diversity, path diversity, and combined time / path diversity in various embodiments. Other embodiments disclosed encompass other processes, improved packets and packet ensembles, integrated circuits, chipsets, computer add-in cards, information storage articles, systems, computers, gateways, routers, cellular telephone handsets, wireless base stations, appliances, and packet networks, and other forms as claimed.

A method and system are provided for the transmission and reception of an In-band On-channel (IBOC) FM-band digital audio broadcast (DAB) signal. The IBOC DAB signal is generated in the transmitter to substantially occupy the upper and lower sideband frequency regions in the RF emission mask for the conventional broadcast analog FM-band. Redundant source bit information is transmitted in both the upper and lower sidebands so that the loss of information in either one but not both sidebands due to large amounts of interference or distortion, caused by, for example, first-adjacent interference, does not deleteriously affect the IBOC DAB receiver performance. The system exhibits both frequency-diversity and time-diversity. The receiver determines which codeword bit estimate, corresponding to either upper or lower sideband signals, is less likely to be erroneous. The receiver system selects between decoded estimates for each pair of demodulated ECC codewords or combines both ECC codeword estimates prior to decoding in certain embodiments.

In a relay scheme, a wireless source apparatus, a wireless destination apparatus and a wireless relay apparatus cooperate for handling transmission failures by space / time diverse channels. In the case of the successful direct transmission, reduced or no additional overhead for the relay selection is incurred. Thus, for a good SNR between source and destination, the inventive protocol has similar performance as a standard approach. In the case of a transmission failure e.g., due to small scale fading, a transmission via a different communication path implementing spatial diversity via a selected relay is supported. The device is to only activate the overhearing of signals in case of weak signal quality between sender and receiver. This selection of relay devices is done by demand only. A specific protocol for the reservation of the wireless medium for the entire cooperative communication has been specified.

A method and apparatus for radio communications which uses frequency and time diversity oriented spread spectrum modulation includes adding an additional link depending on interference characteristics. A plurality of data packets may be communicated from a transmitter to a receiver where a first radio link is established by reserving a series of time slots. The radio link, for example, may be one out of every n time slots, where n>1. A second radio link may further be established on a different one out of every n time slots such that each of the plurality of data packets is transmitted over both the first and second radio links resulting in diversity such that the receiver receives each of the data packets twice. Each radio link uses a frequency hopping channel and for each data packet, transmission over the first link occurs on a different frequency than is used for transmission over the second link. The second link may be established in response to detection by the receiver of reception quality problems associated with the first link. Accordingly, the second link may be terminated in response to detection by the receiver of an absence of reception quality problems associated with the first link.

A system of radio telephony in which time diversity is utilised to improve the quality of voice communication. Variable time diversity is introduced into the transmitted signal such that relatively longer time delays are present under poorer communication conditions. This variable time diversity can be produced by variable depth interleaving, or by use of at least two TDMA slots operating with sufficient time offset to de-correlate errors generated in the two channels.

A method of assigning Multimedia Broadcast Multicast Service (E-MBMS) bearers in a Multimedia Broadcast Single Frequency Network (MBSFN) area in a 3GPP compliant wireless communication system is provided. An infrastructure device is operably coupled to a radio access network comprising one or more MBSFN areas, wherein each MBSFN area supports a plurality of E-MBMS bearers for transporting media streams to user equipments (UE). The infrastructure device receives, from a UE, an identifier of a preferred MBSFN area and a request for a boost to the quality of the transmissions. The infrastructure device assigns first and second E-MBMS bearers in an MBSFN area to support a call to the UE, the first and second E-MBMS bearers providing the same information to the UE in their media content streams. The UE may employ application layer time-diversity reception of the media content.

In a communication system using the time diversity transmission scheme, the communication system provided with the stable automatic frequency control circuit with the wide frequency pull-in range and under low CN ratio transmission is achieved by removing the modulation phase from the received data through the application of the data correlation of the time diversity. The frequency offset in the received signal is compensated as the phase rotator rotates the phase of the received signal, the phase converter converts the phase rotator output into a phase, the serial-to-parallel converter converts the phase converter outputs into serial-to-parallel sequence, the delay units gives a delay to the serial-to-parallel converter output, the phase adder adds the serial-to-parallel converter output to the delay unit output, the multiplier multiplies the phase adder output by a certain value, the integrator integrates the multiplier output, another integrator integrates the integrator output, and the phase rotator controls the phase of the received signal based on the other integrator output.

The invention relates to a method for the modulation diversity of joint codes of an OFDM system. The method leads signal modulation diversity by modulating the rotation of a constellation picture and interlacing components, dispersedly distributes data prepared to be transmitted to different components by rotation modulation and component interlacement so that the data of the different componentsare respectively decayed on a channel to increase superiorities of signal space diversity, then selects an optical rotation angle to maximally enhance transmission property and also leads OFDM frequency diversity and time-frequency interlacement diversity, thereby more effectively enhancing the property of the system. The invention is improved from a previous invention patent application, i.e. a method for the signal diversity of the OFDM system (application number: 2008102264831) and expands an original diversity technique enhancing and improving the transmission property by two-dimensional rotation modulation to a multi-dimensional rotation modulation technique, thereby well utilizing the modulation diversity to be combined with time diversity and frequency domain diversity to enhance the property of the system.

Optimum usage of time diversity and significantly higher data rates are achieved by utilizing an adaptive Ultra-wideband impulse radio (UWB IR) transmission scheme based upon information about the channel state at a particular time instant. Through the use of channel state information, the transmission scheme is adjusted for the particular channel state. In particular, the system is adapted dynamically for each user by varying the number of pulses transmitted per bit in response to the channel state. The channel state is a dynamic parameter of the transmission system that is typically measured or estimated by the receiver. An adaptation element responds to the channel state information to determine a desired number of pulses per bit to be utilized in a transmission channel for subsequent UWB IR communication. This desired number of pulses per bit is then supplied to and used by an adaptive transmitter for subsequent transmission by a particular mobile station.

This invention provides a channel interlacing method and a system in a handheld TV system, in which, the method includes: A, carrying out LDPC coding to input signal source bit streams to output LDPC coding blocks, B, carrying out bit interlacing among the blocks of LDPC, C, carrying out constellation mapping to the interlaced bits to generate constellation points, D, interlacing and mapping the points onto a time frequency plane of a multi-frame including multiple data frames to get an even better time diversity result , at the same time, bit information in a LDPC coding block can be scattered to irrelated data subcarriers by interlacing among LDPC coding blocks and interlaced mapping of constellation and different modulation steps can be processed together.

A simple block coding arrangement is created with symbols transmitted over a plurality of transmit channels, in connection with coding that comprises only of simple arithmetic operations, such as negation and conjugation. The diversity created by the transmitter utilizes space diversity and either time or frequency diversity. Space diversity is effected by redundantly transmitting over a plurality of antennas, time diversity is effected by redundantly transmitting at different times, and frequency diversity is effected by redundantly transmitting at different frequencies. Illustratively, using two transmit antennas and a single receive antenna, one of the disclosed embodiments provides the same diversity gain as the maximal-ratio receiver combining (MRRC) scheme with one transmit antenna and two receive antennas. The principles of this invention are applicable to arrangements with more than two antennas, and an illustrative embodiment is disclosed using the same space block code with two transmit and two receive antennas.

Techniques for enabling broadband data rates at mobile terminals in a beyond-line-of-sight communication system are disclosed. Forward link time-diversity transmission methods and a time-diversity transmitter based upon blockage characteristics are provided. The transmitter optionally supports selective time-diversity and can operate at Ku-band or higher frequencies. A forward link time-diversity receiver and methods for receiving a forward link time-diversity signal are also disclosed. The forward link time-diversity receiver optionally provides low-jitter or low-delay characteristics. A return link transmitter and return link transmit methods which avoid blockages are also disclosed. The return link transmitter can include a signal presence detector and blockage prediction filter.

Space-Time-State Block Coded MIMO communication system using reconfigurable antennas. One or more antennas are operates in accordance with a Space-Time-State Block Code (STS-BC) to effectuate channel coding of a signal being transmitted wirelessly between communication devices. In accordance with such an STS-BC, one or more antennas (being reconfigurable in nature) of a communication device are reconfigured in different radiation states. From some perspectives, this may be viewed as performing three-dimensional channel coding, in that, in addition to achieving at least time diversity of signals being transmitted (and also potentially including spatial diversity), state diversity may be achieved by adapting one or more characteristics of one or more antennas within the communication device. Such an STS-BC may operate in an open loop configuration without requiring any feedback from another communication device to which signals are transmitted. If desired, feedback may be employed for adaptively modifying an STS-BC (or selecting another STS-BC).

A receiver with a time diversity combining component recovers a digital data signal transmitted over a voice channel of a digital wireless telecommunications network. A feature extraction module receives an audio frequency waveform encoding the digital data signal and generates a feature vector representing the digital data signal. A bit sequence estimation module analyzes the feature vector and generates an estimated bit sequence corresponding to the digital data signal. A memory stores the feature vector if the estimated bit sequence contains errors. A time diversity combining component generates a second estimated bit sequence by analyzing the first feature vector in combination with one or more feature vectors stored in the memory.

The invention provides a precoding codebook selection and rotation modulation joint design method based on an MIMO-OFDM system, which comprises the steps of diffusing and distributing transmitted data onto different components through rotation modulation, leading the data of the different components to realize independent fading on respective signal channels so as to increase the advantages of signal space diversity, and further selecting the optimal rotation angle to obtain the maximum lift of the performances; and simultaneously introducing MIMO space diversity, time diversity and OFDM frequency diversity, as well as time-frequency interleaving diversity, thereby realizing gain caused by joint coding modulation diversity and effectively improving the performances of the system.

The invention discloses a packet scheduling method of a multi-user multiple-input multiple-output (MU-MIMO) system. The method comprises the following steps: using a sending terminal to carry out priority assignment on a user; according to priority of the user, and according to an MU-MIMO user pairing principle, carrying out user pairing; according to a result of the user pairing, selecting a multiple-input multiple-output (MIMO) transmission mode. Simultaneously, the invention discloses a packet scheduling apparatus of the MU-MIMO system. According to a scheme of the present invention, a high time diversity gain can be obtained, validity of retransmission is increased, in addition, a problem that a new user is obstructed because of a retransmission user can be avoided, and through carrying out user selection and pairing and selection of the MIMO transmission mode, strong frequency spectrum efficiency can be obtained according to an instantaneous status of a channel.

An OFDM communication channel using both frequency and time diversity (FIG. 1). The OFDM communication channel is used for wireless networks. It further includes a system for performing an ordinary OFDM such as DVB-H / T, and using lower coding rate techniques and interleaving for achieving extra time diversity, frequency diversity, hybrid frequency time diversity or further frequency, time and space diversity.

Methods, searchers, base stations are provided which search for known codes contained in signals received over wireless channels, from mobile units for example. A coherent correlation is performed between an expected known code, and portions of the received signal during periods which are separated in time. Advantageously, by making the correlation periods separated in time, time diversity is realized such that if one or more of the correlation periods exist while the signal is of poorer quality, for example due to a fade, the remaining correlation periods may still yield a meaningful search statistic. Searching is done during time slots defined with reference to system time, not mobile unit time. Advantageously, this makes the searcher design simpler and more efficient. By performing time diversity searching in this manner, search tasks for one mobile unit(s) can be performed between the search task periods for another mobile unit resulting in a more efficient utilization of searcher resources.