Showing papers on "Communication channel published in 1992"

8-PSK trellis codes for a Rayleigh channel

Abstract: A suboptimal trellis coding approach based on the concept of combining a good convolutional code and bit interleavers is presented. The aim is to improve the reliability of digital radio communication over a fading channel. It is shown that over a Rayleigh channel and for a fixed code complexity the proposed system is superior to the baseline system. Its performance is analyzed using the generalized R/sub o/ and the upper bound on the bit error rate. The results suggest that on a Rayleigh channel, the standard trellis codes may not be the correct approach for improving the reliability of the communication channel. The discussion is restricted to a rate 2/3 coded system with 8-PSK modulation. >

Virtual-channel flow control

Abstract: Network throughput can be increased by dividing the buffer storage associated with each network channel into several virtual channels. Each physical channel is associated with several small queues, virtual channels, rather than a single deep queue. The virtual channels associated with one physical channel are allocated independently but compete with each other for physical bandwidth. Virtual channels decouple buffer resources from transmission resources. This decoupling allows active messages to pass blocked messages using network bandwidth that would otherwise be left idle. The paper studies the performance of networks using virtual channels using both analysis and simulation. These studies show that virtual channels increase network throughput, by a factor of four for 10-stage networks, and reduce the dependence of throughput on the depth of the network. >

A statistical discrete-time model for the WSSUS multipath channel

Abstract: The computation of the tap gains of the discrete-time representation of a slowly time-varying multipath channel is investigated. Assuming the channel is wide-sense stationary with uncorrelated scattering (WSSUS), a known Monte Carlo based method approximating the given scattering function (which fully determines the WSSUS channel) is extended by including filtering and sampling. The result is a closed-form solution for the tap gains. This allows the efficient simulation of the continuous-time channel with, e.g., only one sample per symbol, and without explicit digital filtering. >

Method for equalizing a multicarrier signal in a multicarrier communication system

Abstract: A method for optimizing a set of equalizer parameters of an equalizer to be used to equalize a multicarrier data signal that has been transmitted through a distorting channel, comprised of the steps of initializing the parameters, repeatedly sending a training sequence through the channel to the receiver, using the equalizer parameters, the received sequence, and a local replica of the training sequence to update a set of channel target response parameters, windowing the channel target response parameters, using the channel target response parameters, the received sequence and the local replica to update the equalizer parameters, and windowing the equalizer parameters. This training process is repeated until a predetermined convergence condition is detected.

Equalizers for multiple input/multiple output channels and PAM systems with cyclostationary input sequences

Abstract: The author studies minimum mean square error (MMSE) linear and decision feedback (DF) equalisers for multiple input/multiple output (MIMO) communication systems with intersymbol interference (ISI) and wide-sense stationary (WSS) inputs. To derive these equalizers, one works in the D-transform domain and uses prediction theory results. Partial-response MMSE equalizers are also found. As an application, the author considers a pulse amplitude modulation (PAM) communication system with ISI and cyclostationary inputs. The MMSE linear and DF equalizers are determined by studying an equivalent MIMO system. The resulting filters are expressed in compact matrix notation and are time-invariant, whereas the corresponding single input/single output filters are periodically time-invariant. The author also considers MMSE equalizers for a wide-sense stationary process by introducing a 'random phase'. To aid in the performance evaluation of various equalizers, the author derives their mean square errors. >

Integrated communications terminal

Abstract: An integrated communications terminal including a selectable channel demodulator and decoder, a time-division-multiplexed (TDM) channel demodulator and decoder, a data processor and controller, an audio decompressor, a D/A converter, and a data coder and modulator. The terminal is used with a mobile station having a message display, an input device, RF electronics, and an optional transmitter. The selectable channel demodulator outputs a selectable intermediate-frequency signal as in-phase and quadrature-phase signals for decoding by the selectable channel decoder. The TDM channel demodulator generates a frequency offset signal and outputs in-phase and quadrature-phase TDM signals for decoding by the TDM channel decoder as a TDM-data signal. The data processor and controller time-demultiplexes the TDM-data signal as a control signal, a TDM channel and selectable channel look-up table, and paging and message signals, and generates a transmitter frequency command signal, a selectable data rate and frequency command signal, and a TDM data rate and frequency command signal. The audio decompressor outputs a digital audio data signal. The D/A converter outputs analog audio signals. The carrier signal frequency of the transmitter is set by the transmitter frequency command signal generated by the data processor and controller. The data coder and modulator encodes a data signal and then modulates a carrier signal with the coded data signal to create a data-modulated signal. The transmitter amplifies and transmits the data-modulated signal.

Converting from Independent to Employee Salesforces: The Role of Perceived Switching Costs:

Abstract: A study was conducted to understand when and why manufacturers might convert from an independent salesforce to a direct salesforce. On the basis of hypotheses developed from channel distribution th...

Constraints on variable bit-rate video for ATM networks

Abstract: Constraints on the encoded bit rate of a video signal that are imposed by a channel and encoder and decoder buffers are considered Conditions that ensure that the video encoder and decoder buffers do not overflow or underflow when the channel can transmit a variable bit rate are presented Using these conditions and a commonly proposed network-user contract, the effect of a (BISDN) network policing function on the allowable variability in the encoded video bit rate is examined It is shown how these ideas might be implemented in a system that controls both the encoded and transmitted bit rates The performance of video that has been encoded using the derived constraints for the leaky bucket channel is presented >

Apparatus and method using compressed codes for scheduling broadcast information recording

Abstract: Digital compressed codes, associated with advertisements enable a user to selectively record additional information, which would be broadcast on a television channel at a later time. The advertisement could be print advertisement or broadcast advertisement on television or radio. The user enters the digital code (I code) associated with an advertisement into a unit with a decoding means which automatically converts the code into CTL (channel, time and length). The unit within a twenty four hour period activates a VCR to record information on the television channel at the right time for the proper length of time. The decoded channel, time and length information can be communicated directly to a VCR and used by the VCR directly to automatically activate the VCR to record a given television information broadcast corresponding to the communicated channel, time and length. Alternately, the channel, time and length information can be decoded directly in a remote control unit and only start record, stop record and channel selection commands sent to the VCR at the appropriate times. Algorithms for decoding the I codes can be a function of time to ensure security of the decoding method. A method is included for use of the I codes with cable channels.

Method for transmitting broadcast information in a digital control channel

Abstract: The present invention provides a method for transmitting information on a communications channel, e.g. , a digital control channel between a base station and a mobile station in a cellular system. The method includes the steps of grouping the information into a plurality of information elements, providing at least one change flag to indicate whether the value of at least one of the information elements has changed and transmitting the change flag and the information element over the communications channel.

Subband image coding using entropy-coded quantization over noisy channels

Abstract: Under the assumption of noiseless transmission the authors develop two entropy-coded subband image coding schemes. The difference between these schemes is the procedure used for encoding the lowest frequency subband: predictive coding is used in one system and transform coding in the other. After demonstrating the unacceptable sensitivity of these schemes to transmission noise, the authors also develop a combined source/channel coding scheme in which rate-compatible convolutional codes are used to provide protection against channel noise. A packetization scheme to prevent infinite error propagation is used and an algorithm for optimal assignment of bits between the source and channel encoders of different subbands is developed. It is shown that, in the presence of channel noise, these channel-optimized schemes offer dramatic performance improvements. >

Channel Selection for New Industrial Products: A Framework, Method, and Application:

Abstract: The authors present a framework and method for addressing the new product channel choice decision and demonstrate its use with an application for a new industrial product. First, on the basis of ex...

Prioritized channel assignment in a cellular radio network

Abstract: Dimensioning procedures for prioritized channel assignment in a cellular radio network are considered. Under the cutoff priority discipline, the prioritized channel assignment procedures for a single cell and multicell system are formulated as nonlinear discrete capacity allocation problems. Exact incremental algorithms which efficiently solve the proposed problems are devised. They are based on the properties of the blocking probabilities of new calls and handoff calls. Given the number of available frequency channels together with the arrival rates and the grade of service (GOS) for both types of calls in each cell, algorithm SP1 generates an optimal channel assignment which ensures priority for handoff calls. Given the arrival rates and distinct GOSs for new and handoff calls, algorithm SP2 finds the minimum number of channels required in each cell. Algorithm MP extends algorithm SP1 to a multicell system and provides the prioritized channel assignment for all calls in the system. The algorithms are very fast and are appropriate for the fair allocation of frequency channels among cells. >

Buffer control for variable bit-rate channel

Abstract: The problems of buffer overflow and underflow encountered when employing actually variable or effectively variable bit-rate channels for communicating encoded video images are overcome by jointly controlling the number of bits employed to encode each video frame and the transmission bit-rate of the variable bit-rate channel as experience by the encoder. The selection of the number of bits employed to encode each video frame, and hence the encoder bit-rate, as well as the associated channel bit-rate are determined from the encoder buffer fullness, a determination of the decoder buffer fullness and any constraint imposed on the channel. The encoder is responsive to the selected encoder bit-rate and accordingly adjusts its encoding parameters so as to achieve the selected encoder bit-rate.

Method and apparatus for dynamic channel allocation.

Abstract: A base station (21, 22, 23) in a radio communication system (20) comprises a channel allocator (62) for allocating communication channels by accessing a Preferred Channel List (PCL) (64). The PCL ranks channels (116) in accordance with the occurrence of prior events on the channels (112), such as interrupted calls (122), blocked call setup requests (118), and calls successfully completed (106) and in regards to the mean quality margin (110) and the current channel quality (114). The channel allocator (62) allocates (140) the first available channel (128) in the PCL having a free timeslot (132) and with good current channel quality (136).

Method and arrangement for estimating data sequences transmsitted using Viterbi algorithm

Abstract: To reduce the number of operations required for estimating a transmitted data sequence using a Viterbi algorithm, a method and apparatus are provided for (a) storing a plurality of sampled values of an incoming signal in a shift register in a predetermined interval; (b) receiving a plurality of the sampled values from the shift register, and estimating channel responses, at a current time point, of a plurality of first signal sequences which are derived from the plurality of sampled values and each of the length of which is reduced by deleting at least one sampled data at the oldest time point; (c) receiving the channel responses estimated at (b) and checking to see if each of the estimated channel responses is determinate, producing a first signal sequence if an estimated channel response of a first signal sequence is found determinate, and producing an estimated channel response as a first signal sequence at a time point preceding the current time point in the event that the estimated channel response of the first signal sequence is found indeterminate; (d) storing the first signal sequences produced at (c), and producing an estimated channel response which has been stored at a time point preceding the current time point; and (e) determining a plurality of branch metrics using the estimated channel response obtained at (c) and an original first signal sequence before the original first signal sequence is reduced in length.

Channel modeling and simulation in satellite mobile communication systems

Abstract: An analog model describing signal amplitude and phase variations on shadowed satellite mobile channels is proposed. A linear combination of log-normal, Rayleigh, and Rice models is used to describe signal variations over an area with constant environment attributes while an M-state Markov chain is applied to represent environment parameter variations. Channel parameters are evaluated from the experimental data and utilized to verify a simulation model. Results, presented in the form of signal waveforms, probability density functions, fade durations, and average bit and block error rates, show close agreement with measurements. >

Strip lighting system using light emitting diodes

Abstract: A flexible lighting strip for producing a chasing light effect comprising: an insulated three conductor wire Light Emitting Diodes mounted by the memory of the wire insulation and oriented in such a manner that a four channel chase effect may be achieved with the use of only three conductors. The system is of indefinite length and may be field cut or manufactured in finite length modules. The strip may be surface mounted or installed in a suitable enclosure.

Communication on noisy channels: a coding theorem for computation

Abstract: Communication is critical to distributed computing, parallel computing, or any situation in which automata interact-hence its significance as a resource in computation. In view of the likelihood of errors occurring in a lengthy interaction, it is desirable to incorporate this possibility in the model of communication. The author relates the noisy channel and the standard (noise less channel) complexities of a communication problem by establishing a 'two-way' or interactive analogue of Shanon's coding theorem: every noiseless channel protocol can be simulated by a private-coin noisy channel protocol whose time bound is proportional to the original (noiseless) time bound and inversely proportional to the capacity of the channel, while the protocol errs with vanishing probability. The method involves simulating the original protocol while implementing a hierarchical system of progress checks which ensure that errors of any magnitude in the simulation are, with high probability, rapidly eliminated. >

Favorite channel selection using extended keypress

Abstract: A television receiver provides a "favorite channel" selection function for up to ten favorite channels without the addition of a dedicated array of keys. According to the present invention, a user holds-down a digit key for an extended period of time (preferably 3 seconds), and circuitry in the television receiver interprets this "extended keypress" as an instruction to tune favorite channel "N" where "N" corresponds to the digit key pressed. Two digit channel entry can be accomplished as usual by releasing the digit keys in less than the extended period of time (i.e., less than three seconds). An extended keypress of a CHANNEL UP or CHANNEL DOWN key is interpreted as a command to store the currently tuned channel in the favorite channel memory in the location specified by the number of the next digit key pressed. CHANNEL UP and CHANNEL DOWN functions can be accomplished as usual by releasing the CHANNEL UP or CHANNEL DOWN key in less than the extended period of time (i.e., less than three seconds). Alternatively, a separate MEMORY key may be employed for storing favorite channel information. Pressing the MEMORY key serves as a command to store the current channel in the favorite channel memory location identified by the next digit key pressed.

Autoregressive modeling of wide-band indoor radio propagation

Abstract: Based on frequency domain measurements in the 0.9-1.1-GHz band, an autoregressive model for the frequency response of the indoor radio channel is introduced. It is shown that a second-order process is sufficient to represent the important statistical characteristics of the channel both in the frequency domain and the time domain where each pole identifies the arrival of a cluster of paths. A comparison is made between the statistical characteristics of the empirical data and of the channel responses regenerated from the second-order AR processes. Four methods to regenerate the indoor radio channel responses from a second-order AR model are proposed. The accuracy of the methods is examined by comparing the cumulative distribution functions of the RMS delay spread and the 3-dB width of the frequency correlation function with that of the measurements performed in global, local, and mixed indoor radio propagation experiments. >

Channel selecting method for programs of the same category

Abstract: A channel selecting method for programs of the same category is disclosed, wherein arbitrary channels are assigned according to the same types of programs as those contained in signals the broadcast sent from the broadcasting station using a VPS function. This method determines whether the received broadcast signal uses video program system broadcasting, encoding and recognizes codes according to the programs to arbitrarily assign channels for the programs according to the codes. Then, if a desired channel to be viewed is selected, the same types of programs corresponding to that channel can be automatically recognized, so that the broadcasting channel selection for viewing the same type of programs can be easily performed.

Virtual channels for a multiplexed analog component (mac) television system

Abstract: A decoder for use in a television system. The decoder includes a receiver for receiving a television signal having at least one channel. Each channel of the television signal includes video and audio components. A channel maps the channel received by the receiver to a plurality of virtual channels. A first virtual channel utilizes a first combination of video and audio components of the received channel and a second virtual channel utilizes a second combination of video and audio components of the same received channel different than the first combination. A selector allows a subscriber to select one of the virtual channels. Linked text pages may also be mapped to one or more of the virtual channels.

A multiple user spread-spectrum communication system

Abstract: A communication system having a site (42) employing a plurality of communication channels. Each channel is assigned a desired received signal strength threshold. A channel is assigned to a subscriber unit (43a 43b) based upon the strength of the sig-nal received at the site (42) and the power control range of the suscriber unit (43a, 43b). The selection of a channel may be per-formed either by the site (42) or the subscriber unit (43a 43b). In an FDMA environment (50), each separate frequency division channel may be assigned different received signal strength thresholds. In a non-overlapping time interval (TDMA) environment (70), each separate time division channel may be assigned different received signal strength thresholds. In another embodiment (80), a combination of FDMA and TDMA environments can be used.

Satellite communications system

Abstract: A multiple channel demand assignment multiple access (DAMA) system is configured as a spoke-and-hub star network in which a satellite relays information between each of many small-aperture terminals (SATs), which may be portable terminals (PTs), and a hub network control terminal (NCT) which receives requests from the PTs, allocates channel resources, and broadcasts housekeeping messages. The system has a reservation protocol using at least three separate data channels to take advantage of the inherent lack of adequate radiated power at the PTs: a NCT outbound channel is tightly packed with data, without guard spaces, and it uses typically 98% of the allocated power; separate return channels for data and reservations use little satellite power, with no need for extremely tight data packing. Guard spaces are included in the reservation channel to overcome the total range of propagation delay uncertainty without requiring knowledge of the location of a particular PT.

Dynamic channel assignment cordless telecommunication network

Abstract: In a microcellular cordless telephone network, radio speech channels are divided into several channel groups such that no intermodulation products occur among the channels of each group. In each microcell is located a base unit to which one of the channel groups is dynamically assigned. To achieve the channel assignment, each base unit generates priority values of the channel groups as representations of usage of the channel groups, consistently updates them through a statistical process and assigns one of the channel groups having a maximum priority value to the base unit.

Demonstration of error-free soliton transmission over more than 15000 km at 5 Gbit/s, single-channel, and over more than 11000 km at 10 Gbit/s in two-channel WDM

Abstract: By transmitting trains of 213 bit pseudorandom words in a recirculating loop, we demonstrate ‘error-free’ (measured BER ≥10−10) soliton transmission at 5 Gbit/s, single channel, and at 10 Gbit/s in a two channel WDM, over paths as great as 15 400 km and 11 250 km, respectively.