Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of sub-frames and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A method of determining a boundary of a subframe in a time division duplexing (TDD) system is provided. The method detects a power level of a signal on at least one radio frequency, the signal comprising at least one subframe. A time-domain correlation is done on the detected signal with a first reference signal, wherein the first reference signal represents at least one subframe. The location in time of a boundary of the at least one subframe of the detected signal is determined based on the correlation of the detected signal and the first reference signal.

Abstract: Techniques for re-synchronizing Cell Radio Network Temporary Identifiers (C-RNTIs) in a wireless communication system are described. In one design, a user equipment (UE) sends a random access preamble for random access. A base station receives the random access preamble, assigns a Temporary C-RNTI to the UE, and sends a random access response including the Temporary C-RNTI. The UE uses the Temporary C-RNTI as a C-RNTI for itself if a valid C-RNTI is not already available. The UE discards the Temporary C-RNTI and uses the valid C-RNTI if available. The UE sends a transmission after receiving the random access response, and the transmission may include the valid C-RNTI if available. For handover, the base station (a target base station) receives a handover request from a source base station, assigns the valid C-RNTI to the UE, and sends the valid C-RNTI to the source base station for forwarding to the UE.

Abstract: A method for the generation of a signal including a minimum of disturbances and noise is provided. A method for the detection of a signal including a minimum of disturbances and noise is also provided. An element of the signal is functionally dependent on at least one further element of the signal.

Abstract: A receiver includes a receiving unit that receives a signal from a satellite, a frequency conversion-discretization unit that converts the signal received in the receiving unit into an intermediate frequency signal of a frequency bandwidth including 0 Hz, and discretizes the frequency-converted intermediate frequency signal with a predetermined sampling frequency, a filter unit that filters the discretized signal, which is output from the frequency conversion-discretization unit, through a predetermined filter, a synchronization acquisition unit that acquires synchronization of a spreading code in the discretized signal filtered by the filter unit, and a synchronization holding unit that holds the synchronization of the spreading code, which is acquired by the synchronization acquisition unit.

Abstract: A source synchronous signal synchronization system includes a differential signal receiver; a tunable input delay element coupled to the receiver; an input serializer/deserializer (ISerDes) coupled to the tunable input delay; an alignment unit coupled to the ISerDes; and a delay control unit coupled to the tunable input delay, the ISerDes, and the alignment unit.

Abstract: A method and system for measuring latency is provided. A monitor node is used to measure latency in a computer network or in a computing device by time stamping signal messages sent from nodes in the computer network and/or tasks in a particular node or device. The time stamps are generated using a system clock of the monitor node to reduce any discrepancies in timing. In addition, the monitor node may compensate for latencies between the monitor node and each of the one or more nodes or devices across which latency is to be measured. Signal messages may include a data message ID and/or a node ID identifying the message that is being tracked and for which latency is being measured. Latency may further be measured across multiple tasks being performed in the same or different nodes or devices by transmitting signal messages for each of the multiple tasks.

Abstract: Methods and systems for mobile phone location within a digital distributed antenna system (DAS) are provided. In one embodiment, a method comprises: receiving a request for location services from a subscriber unit located within a digital DAS, the digital DAS including a first partition of bandwidth for transporting digitized RF signals of one or more modulated signals and a second partition of bandwidth for an Ethernet pipe transporting IP formatted data; routing the request for location services to a subscriber locator center; instructing locator receivers within a geographical area of the digital DAS to listen for a signal from the subscriber unit; listening for the signal at a first locator receiver; when the signal is observed, recording a time the signal was received and generating subscriber unit ranging data; and transmitting subscriber unit ranging data back to the subscriber locator center in an IP formatted message via the Ethernet pipe.

Abstract: A method and apparatus are provided for use in a cellular radio communication system for adjusting a handover parameter. Information is collected regarding actual handovers that have occurred between one or more pairs of cells as well as handover failures. The collected handover information is processed to determine a handover oscillation rate or a handover cost associated with the cell pair. If the handover performance is determined to be acceptable, the determined handover oscillation rate or the determined handover cost is compared with a predetermined target handover oscillation rate or a predetermined target handover cost, respectively. One or more handover parameters associated with at least one of the cells in the cell pair is adjusted based on the comparison.

Abstract: Relay devices and sink devices that provide synchronized audio and/or video outputs are described. A relay device receives a first communication packet from a source device. The first communication packet includes a data frame. A timestamp is generated. The timestamp is an estimate of a time at which content defined by the data frame will be “played.” A second communication packet is generated that includes the data frame and the generated timestamp. The second communication packet is transmitted from the relay device. In one implementation, the generated timestamp is received by a plurality of sink devices, and is used to synchronize output signals (e.g., sound and/or video images) of the sink devices. In another implementation, the generated timestamp is received by a sink device, and is used to synchronize an output signal of the sink device with an output signal of the relay device.

Abstract: A system including an estimation module, a processing module, and a control module. The estimation module is configured to generate a first set of channel estimates for a plurality of subcarriers of a received signal. The processing module is configured to generate a second set of channel estimates for the plurality of subcarriers, in which the second set of channel estimates are generated based on the first set of channel estimates. The control module is configured to estimate a preamble sequence in the received signal based on each of (i) the first set of channel estimates and (ii) the second set of channel estimates.

Abstract: The present invention provides a ranging method and apparatus, a frame structure includes one or more downlink service time slots, a guard interval between downlink sub-frame and uplink sub-frame and one or more uplink service time slots, and the method includes calculating start time of the first uplink service time slot, configuring the start time as reference time; generating a ranging signal; subtract a sum of time period needed for sending the ranging signal and reference time delay from the reference time and configure obtained time result as time of starting to send the ranging signal; subtract the length of a special ranging time slot from the reference time and configure obtained time result as time of starting to receive the ranging signal by a BS; receiving and processing the ranging signal. By the method and apparatus, all kinds of interference are minimized and an optimum ranging function is implemented.

Abstract: The present invention relates to a method and an arrangement for optimizing radio resource utilizations when scheduling data transmissions between a radio base station (15) and one or more user equipments (18) on a radio channel over a radio interface in a communication network comprising a plurality of said radio base stations (15) serving cells between which said user equipments (18) are moving. Firstly information on channel quality of said radio channel is obtained. Also, information on the traffic per user within the cell is obtained. Then, the information on channel quality and said traffic information are combined and the data transmission is scheduled based on the combination.

Abstract: A method of and an apparatus therefor searching a cell in a mobile station of a communication system in which a plurality of cells are grouped into a plurality of cell groups, and each cell group includes at least two cells. The method includes detecting a primary synchronization signal and a secondary synchronization signal from a received signal, and identifying a cell based on a combination of the primary synchronization signal and the secondary synchronization signal. The secondary synchronization signal is related to the cell group to which the mobile station belongs and the primary synchronization signal is related to the cell to which the mobile station belongs within the cell group.

Abstract: One embodiment of the disclosure sets for a method for synchronizing multiple mobile devices in a wireless network, which includes the steps of calculating a time interval for a first mobile device to respond to a request, receiving timing information of the first mobile device, determining a first offset associated with the first mobile device based on the time interval and the timing information, receiving a first data stream including the timing information of the first mobile device, and inserting a first dataset into the first data stream based on the first offset before transmitting the first data stream.

Abstract: A system and method of synchronizing transmissions in a simulcast system by continuously adjusting the signal transmission delay. Timing information that includes a GPS timestamp is continuously generated at a source site, encoded into a timing packet which along with a content signal can be transported over a network link such as T1/E1 or a packet switched network to multiple transmitter sites. Once received at a transmitter site, the timing packet along with the content signal is delayed by an adjustable delay. The GPS timestamp in the received timing packet is compared to a GPS timestamp that is generated at the transmitter site upon arrival of the timing packet. Based on a variance between that comparison and the value of a user-specified target delay, the delay of the received signal is adjusted to synchronize signal transmissions in the simulcast system.

Abstract: Some embodiments disclosed herein relate to a method. In the method, a duration of a first synchronization pulse is measured. A fixed, predetermined number of ticks are equally spaced at a first time interval over the first sync pulse, regardless of the duration of the first synchronization pulse. A duration of a first data pulse is then measured by periodically incrementing a tick count value at the first time interval during the entire duration of the first data pulse. The tick count value at an end of the first data pulse is then correlated to a first digital value encoded on the first data pulse.

Abstract: A clock and data recovery device receives a serial data stream and produces recovered clock and data signals. The clock and data recovery device operates over a range of frequencies and without use an external reference clock. A first loop supplies a first clock signal to a second loop. The second loop modifies the first clock signal to produce the recovered clock signal and uses the recover clock signal to produce the recovered data signal. The first loop changes the frequency of the first clock signal based on frequency comparison and data transition density metrics.

Abstract: A burst mode receiver including a CDR circuit that does not perform bit synchronization determination at a wrong position even when a burst signal waveform containing a distortion is input is provided. The burst mode receiver includes a CDR circuit for reproducing clock and data from a received signal, a bit synchronization determination circuit for determining whether the CDR circuit is in an optimum phase, a waveform distortion determination circuit for determining from the received signal whether there is waveform distortion, and a CDR output enable determination circuit for determining whether an output of the CDR circuit is valid or invalid. The CDR output enable determination circuit performs CDR output enable determination based on a bit synchronization determination result and a waveform distortion determination result.

Abstract: Provided is a distance and position measuring method. A distance measuring method based on packets transmitted and received between a first node and a second node obtains first timing for transmitting a first packet from the first node, second timing for receiving the first packet in the second node, third timing for transmitting a second packet corresponding to the first packet from the second node, fourth timing for receiving the second packet in the first node, fifth timing for transmitting a third packet from the second node, and sixth timing for receiving the third packet in the first node to estimate a clock frequency offset based on the obtained timings, measures a first distance and a second distance based on the clock frequency offset and some of the timings, and measures a distance between the first node and the second node based on the first distance and the second distance.

Abstract: Provided are: plural circuit components including a circuit component which constitutes a receiving unit receiving a signal sequence which is arranged so that a desired signal and a signal different from the desired signal are lined up in time series, the desired signal indicating desired data which includes at least one of text data, sound data, image data, and a computer program product; and an operating parameter changing unit which changes an operating parameter of at least one of the plural circuit components, during a period in which the receiving unit receives the signal different from the desired signal.

Abstract: Methods and apparatus are provided for pseudo asynchronous testing of receive paths in serializer/deserializer (SerDes) devices. A SerDes device is tested by applying a source of serial data to a receive path of the SerDes device during a test mode. The receive path substantially aligns to incoming data using a bit clock. A phase is adjusted during the test mode of the bit clock relative to the source of serial data to evaluate the SerDes device. The source of serial data may be, for example, a reference clock used by a phase locked loop to generate the bit clock. The phase of the bit clock can be directly controlled during the test mode, for example, by a test phase control signal, such as a plurality of interpolation codes that are applied to an interpolator that alters a phase of the bit clock.

Abstract: A wireless communication system includes a base station and a terminal station. The base station extracts paths that have a power level that exceeds a predetermined threshold value from delay profiles of the terminal station as available paths, selects a path having a maximum power or a first path from the available paths as a reference path, calculates a time difference between an arrival time of the reference path and a predetermined maximum arrival time, and transmits a result to the terminal station as a transmission timing control signal. The terminal station adjusts the transmission timing to the base station according to the time difference. The base station transmits the transmission timing control signal only when the base station detects the reference path.

Abstract: Certain embodiments of the present disclosure relate to a method for tracking of a carrier frequency offset. A soft combined frequency tracking discriminator is proposed as a part of the closed loop structure that can provide fast tracking of the frequency offset in an initial pull-in mode, and can also track small residual frequency variance in a fine-tracking mode.

Abstract: The embodiments provide mechanisms for synchronizing a receiver with OFDM pilots that are robust in the presence of channel fading conditions. In addition to using instantaneous channel estimate values to locate the first arriving path and last arriving path, the methods calculate time-domain averaged channel estimate values and use those averaged values to determine an average first arriving path and last arriving path. A combination of the instantaneous first arriving path and last arriving path and the average first arriving path and last arriving path may then be used to determine the delay spread and calculate a timing offset to be applied in timing synchronization. The various embodiments introduce improvements under channel fading conditions. Time-domain averaging may be embodied in a flexible DSP processor, or implemented in hardware and/or software. Using both instantaneous and time-averaged channel estimates greatly improves the robustness of time synchronization under channel fading conditions.

Abstract: A novel and improved method and apparatus, in a WCDMA communication system (100), for informing a mobile station (101) of a downlink data frame time offset by determining the downlink data frame time offset, and transmitting the downlink data frame time offset via an Active Set Update message transmitted from a cell (102 or 103) to mobile station (101). Once an Active Set Update message is received, the data frame time offset information is provided to a timing block (201) which may determine data frame boundary of each downlink signal. Timing block (201) may then adjust the PN sequence timing corresponding to the downlink signal associated with the data frame time offset such that corresponding data symbols in each data frame are correctly soft combined in a combiner(210).

Abstract: There is disclosed a scheduler for a traffic generator and a method of scheduling traffic. A working memory may stores N respective timer values for N count-down timers, where N is an integer greater than one. An arithmetic and logic unit (ALU) may update each timer value in rotation every N cycles of a clock. A temporal interpolator may delay output data from the ALU by a selectable delay period of 1 to N cycles of the clock.

Abstract: An apparatus and methods for handling emergency message frames (e.g., “911” call frames, etc.) sent by a station in a wireless local-area network are disclosed. The illustrative embodiment increases the probability with which an emergency message frame is accorded the singularly highest quality-of-service by modifying one or more IEEE 802.11e parameters (e.g., back-off contention window length, Arbitration Inter-Frame Space [AIFS], etc.) for a station or access point that transmits an emergency message frame.

Abstract: A method for determining a Doppler shift of a first signal is provided. First, a plurality of Doppler frequency hypotheses is combined to obtain a joint Doppler signal. The first signal is the correlated according to the joint Doppler signal and a plurality of code signals with phases corresponding to a series of code phase hypotheses to obtain a series of correlation results which are then examined to determine whether the Doppler shift does lie in the Doppler hypotheses. A fine Doppler search is then performed to determine the Doppler shift when the Doppler shift lies in the Doppler hypotheses.

Abstract: A wireless communications device may include a portable housing and a temperature-compensated clock circuit carried by the portable housing. The device may further include a wireless receiver carried by the portable housing for receiving timing signals, when available, from a wireless network, and a satellite positioning clock circuit carried by the portable housing. A clock correction circuit may be carried by the portable housing for correcting the temperature-compensated clock circuit based upon timing signals from the wireless network when available, and storing historical correction values for corresponding temperatures. The clock correction circuit may also correct the temperature-compensated clock circuit based upon the stored historical correction values when timing signals are unavailable from the wireless network, and correct the satellite positioning clock based upon the temperature-compensated clock circuit.

Abstract: An apparatus for reproduction of an image frame in an image receiving system is disclosed. The apparatus includes a demultiplexer for restoring a received signal to a decodable bitstream and generating start information of each image frame of the bitstream, and an image decoder for decoding the bitstream restored by the demultiplexer, thereby generating a reproducible I frame or P frame, which is an image frame; an image reproduction time uniformity processing module for buffering each image frame output from the image decoder, and then outputting the buffered I frame or P frame while delaying the I frame or P frame based on the start information of each image frame provided by the demultiplexer according to a preset delay time. The present delay time has been preset to be greater than a processing time period required for decoding of an I frame and to be less than a time interval between image frames in the image bitstream.

Abstract: An apparatus and method for transmitting/receiving an S-SCH in an Institute of Electrical and Electronics Engineers (IEEE) 802.16m wireless communication system are provided. A method for transmitting, by a transmitter, a Secondary Synchronization CHannel (S-SCH) in a communication system includes generating a sequence depending on a cell IDentification (ID), determining a subcarrier set comprising subcarriers to map the generated sequence, based on a Fast Fourier Transform (FFT) size and a segment ID, and mapping the generated sequence to the subcarriers of the determined subcarrier set.

Abstract: A wireless communication system includes first and second transmitting stations cooperating with each other to transmit data signals in parallel to the same receiving station. The first transmitting station transmits data at a slot reference timing of each TDMA slot within a data transmission period. The second transmitting station calculates the adjustment amount of data transmission timing for the receiving station within a propagation delay time measurement period, and transmits data at a transmission timing determined by a slot reference timing and the adjustment amount in each TDMA slot within the data transmission period.

Abstract: A method of routing in a network includes dividing a time corresponding to a predetermined maximum registration age of a first node registered with a second node into a number of first time intervals and second time intervals. The first time intervals each have a predetermined duration and the second time intervals each have a duration greater than the predetermined duration of the first time intervals. Each of the first and second time intervals are assigned a metric designating a cost associated with a path between the first node and the second node. The metric increases in value for each of the first and second time intervals as registration age increases. The second node sends a message including the metric associated with the time interval during which it is transmitted.

Abstract: A method for scheduling packets from a plurality of radio bearers by a scheduler of a first layer includes calculating a virtual scheduling time for the radio bearers by using a packet delay variation of the radio bearers, and transmitting the packet of the radio bearer having the greatest virtual scheduling time from among the plurality of radio bearers to a second layer.

Abstract: It is often required to send a plurality of streams of data in parallel between two network nodes in a synchronous transmission network and also to maintain a particular alignment between those streams of data. This is particularly required when the streams of data are to be transmitted over a wide area network, for example, for data mirroring applications. Virtual concatenation is used for each of the individual data streams as known in the art and in addition, the individual virtual concatenation processes are synchronized or co-ordinated. At a destination node it is then possible to realign the individual data streams with respect to one another.

Abstract: An input bit stream including a clock signal and data bits is oversampled to obtain one or more sets of data samples. One or more sets of non-transitioning phases corresponding to data samples that do not switch between zero and one are then identified. Center phases corresponding to the one or more sets of non-transitioning phases are identified and then a final center phase that accurately represents the bits belonging to the input bit stream is selected. The data samples corresponding to the final center phase are extracted, thereby recovering the clock signal and data bits from the input bit stream.

Abstract: Apparatus, systems, and methods are provided for transmitting messages over a serial interface. A method comprises receiving a first signal at a first time and receiving a second signal at a second time, the second time being after the first time. If a difference between the second time and the first time is less than a threshold time period, the method comprises generating a first message that is representative of the first signal and the second signal and transmitting the first message over the serial interface. In accordance with one embodiment, the threshold time period is equal to one half of an interface acquisition delay time period associated with the serial interface.

Abstract: The present invention relates to an apparatus and method for estimating and compensating for a time offset and a carrier frequency offset in a Multiple Input Multiple Output (MIMO) communication system that supports Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiplexing Access (OFDMA). According to the present invention, a phase difference of pilot signals of the same transmitting antenna, which are received through receiving antennas, is calculated. An arc tangent operation is then carried out on the phase difference of the pilot signals to calculate a time offset linear phase and/or a carrier frequency offset linear phase. Further, a time offset compensation value and/or a carrier frequency offset compensation value are found by employing the time offset linear phase and/or the carrier frequency offset linear phase.

Abstract: The present invention is directed to a method of delivering a video stream. The method operates by determining a group of video streams to be provided to a particular destination over a particular communication link. Next, the band width of the link is allocated to the video streams based upon the particular properties of the various video streams to be transmitted. The video streams are processed so that they fit into the band width allocations. Next, the video streams are transmitted in separate channels, synchronized with respect to each other, to reach the subject destination.

Abstract: A base station establishes a data channel in an uplink between the base station and a user equipment, establishes a control channel in the uplink between the base station and the user equipment, and determines a gating configuration associated with the control channel. The base station also transmits the gating configuration to the user equipment, receives a gated control signal, via the control channel, based on the gating configuration, and synchronizes time slots for signal bursts associated with the gated control signal and time slots for data packets associated with the data channel. The base station further schedules transmissions of the data packets based on the synchronized time slots, generates an absolute grant based on the scheduled transmissions of the data packets, and transmits the absolute grant to the user equipment.

Abstract: A method for performing wireless communication in a network by at least one of a plurality of network nodes, the network including a network coordinator, the plurality of network nodes, and a plurality of subscriber stations. The method includes sending, by at least one of the plurality of network nodes, delay data to at least one of the network coordinator or one or more upstream network nodes. The delay data includes a network node delay data associated with the at least one of the plurality of network nodes, and the one or more upstream network nodes include any of the plurality of network nodes located along an upstream transmission path between the at least one network node and the network coordinator. In addition, the method includes receiving, from at least one of the network coordinator or the one or more upstream network nodes, target delay data, and receiving, from at least one of the network coordinator or the one or more upstream network nodes, a message.

Abstract: A method of determining a residual frequency offset between a transmitter and a receiver in a transmission of data via a communication channel, is described, wherein the message is transmitted from the transmitter to the receiver via the communication channel and the message comprises at least one short preamble (201), at least one long preamble (202) and user data (203). The at least one long preamble (202) comprises residual frequency offset determination information based on which the residual frequency offset is determined.

Abstract: A disclosed base station apparatus includes: a TTI-length determining unit which determines, based on downlink receive quality information transmitted from a mobile station, whether data is to be transmitted in a first TTI with, as a unit, a predetermined period no shorter than a subframe length, or in a second TTI with, as a unit, a period shorter than the first TTI; a number-of-subframes determining unit which determines a number of subframes making up the determined TTI; a reporting unit which reports the determined TTI and the number of subframes making up the determined TTI to the mobile station; and a scheduler which performs scheduling based on the determined TTI and the number of subframes making up the determined TTI.

Abstract: Disclosed are methods for broadcast transmission of data in frames having multiple time slots, from one transmitting node to multiple receiving nodes in a network, having the following steps: The sending out of at least one broadcast request message from the transmitter node to the receiver nodes, wherein the time slots available to the transmitter node for data transmission are indicated; the transmitting back of time-slot granting messages from the receiving nodes, wherein at least one of the time-slots available to the respective receiver node for data transmission is in each case indicated jointly with one at the transmitter node; the sending out of a confirmation message from the transmitter node to the neighboring receiving nodes, wherein all of the receiving nodes are indicated in the time-slot granting messages jointly with the time-slots available at the transmitter node; the performing of a broadcast transmission of the data from the transmitter node to the receiver nodes in the jointly available ti

Abstract: The invention concerns a method for receiving a multi-carrier signal of reduced complexity when the number of carriers is not high. The method includes: demodulating the multi-carrier signal; converting a received signal received in binary representation into a modal representation in a base of at least two mutually prime numbers on a finite space of size equal to the product of the mutually prime numbers; demodulating including conversion.

Abstract: Effects of variation in computational latency can be controlled by using a processor to perform computations associated with a signal processing process, each computation related to processing an input sample to generate an output, and allocating a processing cost per computation that is less than a maximum processing cost of the processor for performing any one of the computations and greater than an average processing cost of the processor for performing the computations. The allocated processing cost for a computation is an allocated time period between receipt of the input sample and generation of the output for the computation. A task requiring a processing time greater than the allocated processing cost is handled as a source of jitter in the signal processing process.

Abstract: A method for determining a transmission timing is provided. The method includes steps of, at a first point in time, determining a first transmission timing for transmissions from a user entity to a first radio transceiver, and determining a representation of a first position of the user entity in relation to the first radio transceiver and at least a second and a third radio transceiver. The method further includes, at a second point in time, subsequent to the first point in time, determining a representation of a second position of the user entity in relation to the first, second and third radio transceivers, and adjusting the transmission timing based on a difference of the first position and the second position.

Abstract: A method and a circuit for obtaining asynchronous demapping clock. The method includes: obtaining a smoothed clock with even gaps in accordance with data to be demapped and a corresponding clock signal; performing phase locking in accordance with a signal reflecting writing and reading conditions of data of a First In First Out (FIFO), to obtain a clock signal required for demapping. The method can effectively filter off jittering created during asynchronous mapping/demapping processes and may ensure a high-performance clock output. Furthermore, the method is applicable to not only mapping from OTN to SDH but also other asynchronous demapping processes, e.g., mapping from SDH to OTN, and thereby effectively improving the performance of data demapping.

Abstract: A method and corresponding system for operating in a network in which stations communicate over a shared medium are presented. The shared medium has at least one varying channel characteristic that varies approximately periodically. The method includes providing repeated beacon transmissions from a coordinator station for coordinating transmissions among a plurality of the stations, wherein at least some beacon transmissions are synchronized to the varying channel characteristic; and transmitting from a first station to at least one receiving station during a time slot determined based on at least one of the beacon transmissions received by the first station from the coordinator station.