Showing papers on "Time-division multiplexing published in 1998"

Ultrahigh-speed optical time-division-multiplexed transmission technology based on optical signal processing

Abstract: Recent progress in optical time-division-multiplexed (TDM) transmission technologies is reviewed including optical short pulse generation, time-division multiplexing/demultiplexing, timing extraction, and waveform measurement. The latest 400-Gbit/s transmission experiments based on optical signal processing are presented and the possibility of terabit/second TDM transmission is discussed.

Phase noise and sub-carrier spacing effects on the performance of an OFDM communication system

Abstract: This letter analyzes the phase noise effects on an orthogonal frequency division multiplexing (OFDM) signal and its dependence with the sub-carrier spacing. Pilot-based channel estimation, which has been suggested as a means of combating the channel effects, can also correct the phase noise effects under some circumstances, which are investigated.

Controlled multimedia wireless link sharing via enhanced class-based queuing with channel-state-dependent packet scheduling

Abstract: A key problem in transporting multimedia traffic across wireless networks is a controlled sharing of the wireless link by different packet streams. So far this problem has been treated as that of providing support for quality of service in time division multiplexing based medium access control protocols (MAC). Adopting a different perspective to the problem, this paper describes an approach based on extending the class-based queueing (CBQ) based controlled hierarchical link sharing model proposed for the Internet. Our scheme enhances CBQ, which works well in wired links such as point-to-point wires of fixed bandwidth, to also work well with wireless links based on radio channels that are (i) inherently shared on-demand among multiple radios, and (ii) are subject to highly dynamic bandwidth variations due to spatially and temporally varying fading with accompanying burst errors. The proposed scheme is based on combining a modified version of CBQ with channel-state dependent packet scheduling.

Symbol rate and modulation level-controlled adaptive modulation/TDMA/TDD system for high-bit-rate wireless data transmission

Abstract: This paper proposes a time-division multiple-access/time-division duplex (TDMA/TDD)-based symbol rate and modulation level-controlled adaptive modulation system for high-bit-rate data transmission. The proposed system controls both the symbol rate and modulation level for the next transmission time slot according to the estimated carrier power to noise spectral density ratio (C/N/sub 0/) and delay spread for the time slot to achieve higher bit rate and higher transmission quality as well as higher delay-spread immunity. It is demonstrated by computer simulation and laboratory experiments that the proposed system can achieve a higher average bit rate with higher transmission quality in comparison with the fixed-rate quaternary phase-shift keying (QPSK) system and modulation level-controlled adaptive modulation system in both flat Rayleigh and frequency-selective fading environments. The simulated and experimental results also show that the proposed adaptive modulation techniques can be applied to 1-2-Mb/s indoor and outdoor microcellular systems with its delay spread of up to 250 ns and its terminal mobility of up to pedestrian speed without employing any special antifrequency-selective fading techniques, such as the adaptive equalizer and space diversity.

Key technologies for terabit/second WDM systems with high spectral efficiency of over 1 bit/s/Hz

Abstract: To fully utilize a limited gain bandwidth of about 35 nm (4.4 THz) in an erbium-doped fiber amplifier, an increase in signal spectral efficiency is required. In this paper, we investigate the key technologies to achieve terabit/second wavelength-division multiplexing (WDM) systems with over 1 bit/s/Hz spectral efficiency. Optical duobinary signals, which have narrower optical spectra than conventional intensity modulation signals, were applied to such dense WDM systems. The measured minimum channel spacing for 20-Gbit/s optical duobinary signals was 32 GHz and a spectral efficiency of over 0.6 bit/s/Hz was reached. By using polarization interleave multiplexing, spectral efficiency was expected to reach 1.2 bit/s/Hz in an ideal case with no polarization dependencies along the transmission lines. In such ultradense WDM systems with narrower channel spacing, stabilizing the wavelengths of laser diodes is an important issue for achieving stable operation over long periods. To do this, we developed a simple and flexible wavelength stabilization system which uses a multiwavelength meter. The wavelengths for 116 channels with 35-GHz spacing were stabilized within /spl plusmn/150 MHz. The stabilization system is applicable to ultradense WDM signals with a spectral efficiency of over 1 bit/s/Hz by employing wavelength interleave multiplexing and an optical selector switch. On the basis of these investigations, we demonstrated a 2.6-Tbit/s (20 Gbit/s/spl times/132 channels) WDM transmission by using optical duobinary signals. In addition, 1.28-Tbit/s (20 Gbit/s/spl times/64 channels) WDM transmission with a high spectral efficiency of 1 bit/s/Hz was achieved by using polarization interleave multiplexing.

Massive wavelength-division multiplexing with solitons

Abstract: Solitons have already enabled the demonstration of many-channel wavelength-division multiplexing (WDM), error free over transoceanic distances, at per-channel rates of 10 and 20 Gbit/s. In this paper, we assess the potential for extending the total transmission rate to many hundreds of gigabit/s in such massive WDM with solitons. We examine the new "dispersion-managed" solitons, as well as the conventional ones, and we consider the advantages of combining each with sliding-frequency guiding filters. Finally, we also describe a practical way for making the required accurate dispersion maps.

System for time division multiplexing broadcast channels with R-1/2 or R-3/4 convolutional coding for satellite transmission via on-board baseband processing payload or transparent payload

Abstract: A satellite direct radio broadcast system is provided which assembles bits of broadcast programs into prime rate increments, several of which are assembled into a frame. Frames are divided into symbols which are demultiplexed into alternating ones of a plurality of prime rate channels. The broadcast channel frame is encoded for forward error correction (FEC) using an R-½ Viterbi coder or a R-¾ Viterbi coder, depending on the desired bit rate for a time division multiplexed (TDM) stream comprising the broadcast channel. A broadcast station is configured to format FEC-encoded broadcast channel frames into TDM frames when transmission of the TDM frames by a transparent payload on-board a satellite is used.

Method and apparatus for providing a time-division multiplexing (TDM) interface among a high-speed data stream and multiple processors

Abstract: A Multiservice Access Concentrator (MAC) is provided at which a dynamic association is established and maintained among a number of processors and a number of voice channels of a data stream. The voice channels are multiplexed voice channels received in a Pulse Code Modulation (PCM) data stream. The processors comprise digital signal processors (DSPs) for performing compression and decompression of the plurality of voice channels. A table is generated that tracks the association among the plurality of processors and the plurality of voice channels. At least one signal is generated that synchronizes a transfer of data among each of the processors and the associated voice channels. The generation of at least one signal comprises providing a frame synchronization signal to each of the processors to indicate the start of a first voice channel. Furthermore, a byte synchronization signal is provided to each processor when the associated voice channel is available for transfer. Moreover, a clock gating control signal is provided to each of the processors when the associated voice channel is available for transfer. A number of compressed voice channels are provided to at least one multi-service network using a configurable trunk, wherein the at least one multi-service network comprises Asynchronous Transfer Mode (ATM), Frame Relay, High-level Data Link Control (HDLC), Internet Protocol (IP), and TDM networks.

Toward wide-scale all-optical transparent networking: the ACTS optical pan-European network (OPEN) project

Abstract: The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.

Asynchronous digital optical regeneration and networks

Abstract: This paper outlines the concept of the asynchronous digital optical network, which is aimed to combine the advantages, and overcome the drawbacks, of existing approaches to photonic networking. The network is based on digital optical transmission and processing, which offers the prospect of almost infinite scalability. Optical transmission throughout the network is in burst mode, using a standard digital optical signal format. The main defining feature of the asynchronous network is that the network nodes (in which the optical processing and routing take place) do not share global synchronization at the bit level. Instead, the nodes each operate with independent bit-level clocks. This approach removes the architectural constraints found in synchronous networks. An essential component of the network is the asynchronous digital optical regenerator. Various design and performance aspects of this new type of regenerator are analyzed.

Glitch free delay line multiplexing technique

Abstract: A glitch free delay line multiplexing technique is described that includes an intermediate multiplexing system and an output multiplexer. The intermediate multiplexing system receives signals from a plurality of delay units and outputs a subset of delay signals that includes the signal presently selected, the signal presently selected with an additional delay, and the signal presently selected with one less delay. The intermediate multiplexing system receives a control word from a select mechanism in a non-time critical manner. The output multiplexer receives the least significant bits of the control word and outputs the selected signal.

Drop and insert multiplexing with simultaneous clock recovery using an electroabsorption modulator

Abstract: A three-node optical time-division multiplexing (OTDM) network is demonstrated that utilizes electroabsorption (EA) modulators as the core elements. Each node is self contained and performs its own clock recovery and synchronization. "Drop and insert" functionality is demonstrated for the first time with an EA modulator by completely removing a 10-Gb/s channel from a 40-Gb/s OTDM data stream. A different 10-Gb/s channel was subsequently inserted into the vacant time slot. Clock recovery is achieved by using an EA modulator in a novel bidirectional configuration. Bit-error-rate (BER) measurements are presented for each of the 10-Gb/s OTDM channels.

Matched filter bound optimization for multiuser downlink transmit beamforming

Abstract: This paper is devoted to the optimization of the matched filter bounds (MFB) of different co-channel users, using adaptive antenna arrays at base stations for downlink transmit beamforming in cellular mobile communication systems. We mainly consider time division multiple access (TDMA) frequency division duplexing (FDD) based systems. Note that in the case of time division duplexing (TDD), under terrain assumptions the downlink channel can be assumed to be practically the same as the uplink channel. On the contrary, when using FDD, the downlink channel can not be directly observed and estimated. That makes FDD based systems most difficult to deal with, although the proposed criteria and methods are general and suitable for both FDD and TDD. Problem formulations are provided for both spatial division multiple access (SDMA) and non-SDMA spectrum reuse techniques. Novel analytical solutions and algorithms are derived, implementation issues are discussed and simulations are provided in order to compare different approaches.

Digital video signal mpeg2 and time division multiplexer and multiplexed digital signal demultiplexer

Abstract: In a digital signal multiplexing device of a digital signal multiplexing and demultiplexing system, two multiplexers ( 21 ) respectively multiplex first and second programs of first to N-th MPEG2 compression encoded digital video signals into first and second transport signal sequences in accordance with an MPEG2 transport signal scheme, where N represents an integer which is two or greater. In accordance with a time division multiplexing scheme other than the MPEG2 transport stream scheme, a single multiplexer ( 23 ) further multiplexes the first and the second sequences into a multiplexed digital signal comprising a succession of payloads in which the first to the N-th digital video signals are time division multiplexed. The system is useful in a wholly digital broadcast service for more than a score of satellite broadcast channels.

Simultaneous all-optical add and drop multiplexing of 40-Gbit/s OTDM signals using monolithically integrated Mach-Zehnder interferometer

Abstract: Summary form only given. Simultaneous all-optical add and drop multiplexing of a 40-Gbit/s OTDM signal using a monolithically integrated semiconductor optical amplifier/Mach Zehnder interferometer (SOA-MZI) is demonstrated. While maintaining a penalty of 1.3 dB for the add operation the sensitivity for the demultiplexed signal is -34.4 dBm.

Optical differential phase shift keying transmission system having multiplexing, routing and add/replace capabilities

Abstract: A Differential Phase Shift Keying (DPSK) optical transmission system provides time division multiplexing, channel routing and channel add/replace functions. The DPSK transmitter comprises a laser to generate an optical carrier signal; a delay encoder to provide a different delay for each of a plurality, M, of input signal channels; and a M channel phase modulator which phase modulates the optical carrier signal with each of the differently delayed M input signal channels to form a Time Division Multiplexed (TDM) phase modulated optical signal. A DPSK receiver demodulates a received TDM phase modulated optical signal. The system may also include apparatus to route, add, and replace TDM channels.

Wavelength division multiplexing optical transmission system

Abstract: In a wavelength division multiplexing optical transmission system having an optical fiber transmission line (224) whose zero-dispersion wavelength is around 1550 nm, the wavelengths of at least two signal lights among a plurality of wavelength-multiplexed signal lights lie in a range between 1450 nm and 1530 nm or between 1570 nm and 1650 nm.

Terabit/second transmission experiments

Abstract: This paper discusses the reasons for the recent acceleration in the exponential growth rate of single-fiber transmission capacity. The various transmission experiments with capacities of 1 Tb/s and greater are reviewed.

Burst synchronization for OFDM-based cellular systems with separate signaling channel

Abstract: A novel burst synchronization scheme suitable for a high rate OFDM/TDMA/TDD (pico)cellular system with a centralized dynamic slot allocation MAC protocol is presented. The physical layer may have an optional low-rate separate signaling channel (SSC) used in the standby mode and implemented on a subset of OFDM subcarriers. A one-shot feedforward synchronization concept for the OFDM-based active transmission mode is designed using the functionality of the SSC and a special periodical OFDM preamble. Joint symbol and frequency synchronization as well as channel estimation can be achieved simultaneously. The synchronizer features low complexity and low processing delay. Simulations verify its robust operation for indoor channel power delay profiles at 5 GHz.

Large capacity optical ATM switch

Abstract: An optical asynchronous transfer mode ATM switch for recovering the limitation of processing capacity and performing large capacity of switching is disclosed. The ATM switch includes wavelength division multiplexing/time division multiplexing conversion modules for demultiplexing wavelength multiplexed optical channels through transmission links of respective input terminals of a switch to convert them into a primary wavelength for routing to their respective channels and compressing to time division multiplexing for preventing collision between cells, a first router for routing the respective cells which are converted into a primary wavelength by the wavelength division multiplexing/time division multiplexing conversion modules to assign the first destination, time division multiplexing/wavelength division multiplexing conversion modules for demultiplexing the channel signals routed by the first router, decompressing into original signals to convert them into wavelength to be routed for final destination and compressing them again to prevent collision between cells, and second routers for routing the decompressed signals from the time division multiplexing/wavelength division multiplexing conversion modules to the final destination.

Novel gain-transparent SOA-switch for high bitrate OTDM add/drop multiplexing

Abstract: We demonstrate an all-optical switch with the inherent advantage of leaving the non-switched pulses undisturbed the switching principle is based on index modulations at 1.55 /spl mu/m that originate from gain saturation in a 1.3 /spl mu/m semiconductor optical amplifier.

Multimedia multiplexing method

Abstract: A multiplexing method for multimedia communication is provided, which is compatible with the H.223 protocol by changing a header of a multiplex protocol data unit (MUX-PDU). The multiplexing method includes the steps of encoding media data, and multiplexing the media data encoded in the step (a) in units of a predetermined frame, and inserting a second flag (150) having a predetermined length with an auto-correlation in the frame after a first flag (140) having the opening and closing of the frame. Therefore, the probability of detecting the MUX-PDU by a receiver is increased by adding a flag (150) having a high auto-correlation to the H.223 MUX-PDU frame, thereby increasing error-resiliency.

Time-division multiplexing transmission system

Abstract: In a transmitter, at least some of synchronization patterns in a signal having frame structure are inverted in a bit inverting circuit, and a plurality of channels of signals which include a signal having the inverted synchronization patterns are multiplexed and transmitted in a time-division manner. In a receiver, the time-division multiplexed channels are demultiplexed into individual channels. Then, frame synchronization is performed on the basis of the channel having the inverted synchronization patterns among the demultiplexed channels. With the frame synchronized channel as a reference, the remaining channels are identified. There is no need to provide a synchronization circuit in each channel, and the size of the system is not increased.

An air interface for high bandwidth cellular digital communications on microwave frequencies

Abstract: An air interface for use in high throughput digital cellular networks is presented. The design of the interface is one of the contributions to the multidisciplinary Mobile Multimedia Communications (MMC) project at Delft University of Technology. The targets include 155 Megabit per second sustained throughput for high-level users, support for inexpensive mobile stations and support for the Internet protocol (IP), as well as an option for asynchronous transfer mode (ATM). The design consists of an hierarchical frame structure that employs a combination of frequency division multiplexing (FDM) and time division multiplexing (TDM). A comparison is made with the published results of two other research projects, namely MBS (Mobile Broadband Systems) and Median. A protocol is presented that allows transport of control information and data over this link. This protocol features automatic repeat request (ARQ), support for multiple qualities of service (QoS) and graceful degradation of service quality when the load becomes higher than the capacity. A detailed description of the implementation is given.

Adaptive C-OFDM system at 30 GHz for the last mile wireless broadband access to interactive services

Abstract: In this paper a wireless local multipoint distribution system (LMDS) at 30 GHz for the last mile broadband distribution to users of interactive services is investigated. The system we propose users a coded OFDM transmission scheme with FDM and/or TDM multiplexing techniques and adaptive carrier allocation to counteract the effects of the wireless communication channel. An urban microcell in an actual propagation environment is analyzed by means of a ray-tracing tool. Coverage probability is defined and investigated and the choices of the optimum multiplexing technique and carrier allocation algorithm are discussed. It is found that a pure FDM technique with adaptive carrier allocation and priority to users having the largest path loss leads to the best performance.

Video data multiplexer, video data multiplexing control method, method and apparatus for multiplexing encoded stream, and encoding method and apparatus

Abstract: Data for control by statistical multiplexing is efficiently transferred. Each of encoders transfers data for statistical multiplexing representing the degree of difficulty of encoding to a multiplexer (4) by using a private packet through a transmission line through which encoded video and audio data is also transferred. The multiplexer (4) multiplexes the data from the encoder at a first rate (R1) higher than the transmission rate of the transmission line at the succeeding stage and outputs a transport stream (TSd) including a private packet to a statistical multiplexing computer. The multiplexer (4) also multiplexes data from which the private packet is eliminated at a second rate (R2) equal to the transmission rate of the transmission line at the succeeding stage and outputs a transport stream (TSm) including no private packet to the transmission line at the succeeding stage.

Field trial at 40 Gbit/s over 28.6 and 86 km of standard singlemode fibre using quaternary dispersion supported transmission

Abstract: 40 Gbit/s transmission using a single optical carrier and electrical time division multiplexing is demonstrated for the first time reusing standard singlemode fibres from the existing fibre infrastructure of Portugal Telecom. Bit error measurements as well as video transmission via STM1 interfaces demonstrate the robustness of dispersion supported transmission under real operating conditions.

Investigation of cascadability of add-drop multiplexers in OTDM systems

Abstract: The influence of coherent cross-talk on the cascadability of add-drop multiplexers in optical time division multiplexing (OTDM) systems is analysed theoretically using moment generating functions. Calculations are validated by experiments.

Time division multiplexer-demultiplexer and method of operation thereof

Abstract: Systems and methods for time division multiplexing are described. A time division multiplexer-demultiplexer system includes I) a signal transmitting system for transmittal of a serialized signal including A) latency free continuous data and B) at least one member selected from the group consisting of bursty data and packetized data, the signal transmitting system including a multiplexer and a timing control block; and II) a signal receiving system for reception of the signal without disrupting the laminarity of the latency free continuous data, the signal receiving system including a demultiplexer and a sequence detector. The systems and methods provide advantages in that continuous data can be simultaneously transmitted with bursty data and/or packetized data on the same tie line without disrupting the laminarity of the continuous data.