674results about "Link quality based transmission modification" patented technology

A intelligent backhaul radio have an advanced antenna system for use in PTP or PMP topologies. The antenna system provides a significant diversity benefit. Antenna configurations are disclosed that provide for increased transmitter to receiver isolation, adaptive polarization and MIMO transmission equalization. Adaptive optimization of transmission parameters based upon side information provided in the form of metric feedback from a far end receiver utilizing the antenna system is also disclosed.

Systems, devices and methods for updating link adaptations in multi-carrier modulated signals between an access point (AP) and a wireless local area network (WLAN) station (STA) include (are configured for) periodically transmitting a channel sounding signal from the AP. The STA receives each unsolicited channel sounding signal and evaluates the current channel conditions between the AP and STA. The AP adjusts a rate of transmission of the channel sounding signals in accordance with the channel coherence time so that the channel estimates performed by the STA will be valid within the time varying characteristics of the channel. Depending on the length of the coherence time for network environment, the channel sounding signals may be AP beacons, low overhead signal fragments with no payload, or a combination of both.

The invention proposes a method and a unit for controlling the flow of at least one TCP connection between a sender and a receiver. The method is of the type which consists in controlling, at the level of a given multiplexing node through which TCP segments relevant to the connection pass, a window size parameter contained in acknowledgement segments sent back by the receiver. The method comprises the steps of:

• • a) receiving an acknowledgement from the receiver on the up link (receiver to sender) of the connection at the level of said given multiplexing node;
  • b) controlling a window size parameter contained in, said acknowledgement segment on the basis of the difference between, firstly, a first context value associated with the TCP connection, defined as being the sequence number of the last segment that was transmitted from said given multiplexing node on the down link (sender to receiver) of the connection, to which the length of said segment is added, and, secondly, the sequence number indicated in said acknowledgement segment;
  • c) transmitting the acknowledgement segment to the sender the up link of the connection from said multiplexing node with the window size parameter thus controlled.

Multi-user (MU-) MIMO systems with quantized feedback are designed to maximize the sum-rate via scheduling and linear precoding. To maximize throughput over the network, quantized CSIT is sent through a low-rate feedback link feedback from a plurality of users back to a base station. The base station then determines a subset of the plurality of users to transmit one or more signals to based on the received feedback and determines a preceding matrix based on the received feedback from the plurality of users wherein the precoding matrix maximizes a sum-rate throughput for the subset of the plurality of users. Additionally, based on the received feedback, the base station designs a quantization codebook. This codebook may be designed off-line and/or online. The codebook and/or precoding matrix are used to transmit signals to the users.

A method and apparatus are described including mapping a multicast connection to a unicast uniform resource identifier, establishing a state for a multicast-to-unicast conversion, allocating ports, receiving multicast addressed data packets and converting the multicast addressed data packets to unicast addressed data the packets.

A space-time-frequency block coding apparatus and method in a transmitter with three transmit (Tx) antennas are provided. An input symbol sequence is transmitted through three Tx antennas according to a permutation method using a selected transmission matrix in order to improve the performance of an STFBC.

A bidirectional signal processing method uses parallel transmission of digital transmitted data streams in a multiple input-multiple output system. Related art methods generate high bit error rates mostly in singular transmission channels. For this reason, the rank-adaptive signal processing method provides that the number n_d of active subchannels are varied according to the actual channel behavior in order to effect a robust data transmission even in singular radio channels based on a transmit-side and receive-side channel knowledge and a modification of the data vector by a linear matrix vector multiplication while introducing a factor gamma for limiting the maximum transmit power. The maximum transmit power is then only distributed to the currently activated subchannels so that no transmit power remains unused. Another optimization of the number of subchannels n_d occurs when selecting the modulation and encoding methods. During the optimal rank-adaptation according to the water-filling principle, another power is allocated to each subchannel. Another modulation and encoding method is accordingly selected for each data stream. During the suboptimal rank-adaptation according to the channel inversion principle, all subchannels have the same power whereby enabling the data streams to be modulated and encoded in a common source

A test signal generator at a transmitter station and a facsimile generator at a receiver station go through an acquisition and tracking process which aligns the two signals so that a logical processor can compute the frequency transfer function of the entire propagation path for use in an adaptive, concurrently sent communication signal. The frequency transfer function is conveyed back to the transmit end via a control channel permitting an adaptivity function at the transmit end to influence subsequent selection of communication parameters, among which are typically transmitted data rate, selection of modulation, selection of forward error correcting coding, and selection of frequency band for transmission. The same measurement is conveyed to an adaptivity function at the receive end for use in the communications receiver to select demodulator variables such as gain control, and equalization of amplitude and phase, versus frequency. The adaptivity function also permits interspersing of reverse-direction communications over the same frequency bands in a time-share mode between forward-direction and reverse-direction communication with the measurement signals having to be transmitted in only one direction. An alternate embodiment invention of this type is described which is additionally useful for mobile communications channels. Another variation embodiment is described for pure propagation measurements only, absent conveyance of end-user information.

A multiple-input multiple-output (MIMO) wireless communication system. A transmitter that includes a plurality of transmit antennas selects one of a spatial multiplexing scheme and a spatial diversity scheme, processes a signal in the selected transmission scheme, and transmits the signal through the plurality of transmit antennas. A receiver that includes a plurality of receive antennas processes a signal in a reception scheme mapped to a transmission scheme of the transmitter. The transmission schemes include a transmission scheme for maximizing diversity gain and a transmission scheme for maximizing spectral efficiency. The MIMO communication system using an adaptive transmission mode switching technique performs switching between MIMO transmission modes using spatial selectivity of a channel, thereby obtaining maximum gain in a signal to noise ratio (SNR) and spectral efficiency according to channel state.

An automatic retransmission request control system in OFDM-MIMO communication system. In this system, an ACK/NACK output part (320) of a receiver transmits, to a transmitter, a feedback information of positive or negative response based on the result of a cyclic redundancy check. An error data stream decision part (310) of the transmitter determines, based on the feedback information, a data stream that need be retransmitted, and a retransmission mode selection part (312) selects a retransmission mode from among (a) a mode in which to transmit the data, which are to be retransmitted, via the same antenna as in the previous transmission, while transmitting, at the same time, new data by use of an antenna via which no data retransmission is requested; (b) a mode in which to transmit the data, which are to be retransmitted, via an antenna via which no retransmission is requested, while transmitting new data via another antenna at the same time; (c) a mode in which to use STBC to retransmit the data via an antenna via which no retransmission is requested; and (d) a mode in which to use STBC to retransmit the data via all the available antennas.

Vector signaling code communications systems rely on group transmission of code symbols using multiple signaling channels that may have differing propagation characteristics, resulting in differing received signal levels, waveforms, and symbol arrival times, and thus that should be actively monitored and adjusted to minimize differential signal characteristics. Information obtained during symbol decode may be analyzed to identify channel operational characteristics during normal operation and perform non-disruptive channel adjustments, including per-channel adjustment of sample-and-hold timing to realign code symbol groups. Initialization or start-up adjustment may also be performed using intentionally-transmitted training patterns.

A method is provided of a base station for wireless telecommunications changing scrambling code to be applied to pilot signals for transmission. The method comprises automatically:

• • identifying a need to change scrambling code,
  • selecting a new scrambling code for use,
  • reprogramming the base station to use the scrambling code, and
  • using the new scrambling code for subsequent pilot signal transmissions.

A system for efficiently and reliably communicating over a high-speed asymmetric communications link. The system includes a first mechanism for connecting a first device to a second device via a channel. A second mechanism delivers data packets over the channel from the first device to the second device. Each packet is associated with a window of packets. A third mechanism selectively employs the second mechanism to re-send data packets not received by the second device after each window of packets. The window of packets is sized in accordance with the bandwidth of the communications link between the first device and the second device, and the round trip delay time. In a specific embodiment, the first mechanism (includes Transmission Control Protocol/Internet Protocol (TCP/IP) functionality on the first device and the second device for establishing a first TCP/IP link from the second device to the first device. The first mechanism also includes Universal Datagram Protocol (UDP) functionality on the first device and the second device for transferring UDP packets from the first device to the second device. The third mechanism sends acknowledgement messages from the second device to the first device specifying the packets not received by the second device. The system further includes a fourth mechanism for selectively disabling the second mechanism when first device does not receive an acknowledgement message after a predetermined time interval. The predetermined time interval is a function of a window timeout variable. The predetermined function is (M)x(window timeout), where M is approximately 2. The window timeout is greater than N multiplied by a number of packets included in the window of packets divided by the data rate of the communications link between the first device and the second device, here N is an integer greater than 1. N is between 3 and 10.

Several techniques are provided for use by wireless devices to avoid interference with signals that are of a periodic or quasi-periodic nature that may operate in the same frequency band and proximity. In some cases, the periodic signals are detected and their timing is determined so as to predict when a next interfering event will occur. Devices that are affected by the periodic signal (such as an affected device with information to be transmitted or devices that have information to be transmitted to the affected device) are controlled to prevent transmissions during the interfering intervals. In addition, a process is provided to dynamically fragment a transmit frame of information to transmit part of the information before the interfering interval and the remainder of the information after the interfering interval, rather than waiting to transmit the entire frame until after the interfering interval. Moreover, techniques are provided to correct for clock drift between the periodic signal and a device affected by the periodic signal, as well as for clock drift between a device affected by the periodic signal and other devices that communicate with that device. These techniques prevent interference with periodic signals and in so doing, improve the quality of service of the communication link for both the interfering devices and the other devices.

A wireless transmission device capable of communicating with a receiver according to a DFT-spread OFDM protocol. The wireless transmission device comprises a configurable spectral shaping filter block capable of performing spectral shaping of an outgoing signal. The wireless transmission device configures the configurable spectral shaping filter block to perform spectral shaping according to a peak-to-average power (PAPR) value associated with the outgoing signal. The multi-carrier protocol comprises one of orthogonal frequency division multiple access (OFDMA) and orthogonal frequency division multiplexing (OFDM).

A wireless communication apparatus performs wireless communication using a plurality of frequency channels. In order to prevent a radio signal from interfering with another wireless communication system, the apparatus includes a unit which detects an error rate of each of the plurality of frequency channels, a unit which determines whether the detected error rate is higher than a specific threshold value, and a unit which suspends use of a frequency channel whose error rate is determined to be higher than the threshold value.

A method of transmitting pressure pulses from a downhole location through a flowing fluid in a wellbore comprises using a linear actuator to controllably move a reciprocating member axially back and forth between a first position and a second position to at least partially obstruct flow of the flowing fluid to generate the pressure pulses. A reciprocating pulser for generating pressure pulses in a fluid flowing in a wellbore, comprises a fluid passage that allows flow of the fluid through the pulser, and a reciprocating member. A linear actuator is coupled to the reciprocating member, such that the linear actuator moves the reciprocating member in a first axial direction and then in a reverse direction to at least partially obstruct flow of the fluid through the pulser to generate pressure pulses in the flowing fluid.

To alleviate the requirement to back-off all up-link performance, such as by limiting power spectral density, to overcome far-end cross-talk problems otherwise associated with relatively short loop-length wireline links, the present invention partitions the frequency spectrum based on an estimate of the loop length of a subscriber unit (CPE) modem from an exchange (LTE) modem. Up to a threshold frequency (fmax) at which received transmissions from a subscriber having a longest loop length (115) become indistinguishable by the LTE modem from a noise floor (102), up-link performance on all loop lengths is limited to correspond to that of the longest loop. At frequencies above the threshold frequency (fmax), subsets of subscribers (152-154) having relatively short loop lengths (116-119) use high frequency carriers that have signal to noise ratios sufficient to support information transmission in these elevated frequency bands.

To address the need for a resource allocation scheme that results in a better tradeoff between the cell-edge performance and the overall spectral efficiency, a communication system is provided that allocates uplink transmit power to user equipment (UEs) based on a fractional power control scheme. In another embodiment, since the cell-edge users are also likely to be power limited, the communication system may implement a minimized uplink transmission bandwidth resource allocation scheme that may work with the fractional power control scheme to achieve a level of performance desired for uplink transmissions in 3GPP (Third Generation Partnership Project) and 3GPP2 Evolution communication systems.