Synchronous Time Division Multiplexing Research Articles

One-channel networked data fusion with communication constraint

Multi-sensor data fusion over one channel is studied in this paper. The communication constraint considered here is medium access constraint. When the synchronous time division multiplexing (STDM) mechanism is used to address this problem, collective delay emerges. Collective delay time depends upon the channel capacity and traffic flow assigned to the communication channel, causing contradiction between traffic flow and delay time (the number of transmitted sensors and delay steps). A new model is developed that can truly reflect this contradiction by introducing a stochastic process θ. Based on the obtained system model, the optimal data fusion filter is designed. It also gives the upper bounds of the expected estimation error covariance and estimation error covariance with one-step delay. Two illustrative examples are given in the last section to show the influence of θ on estimation performance.

Channel statistical multiplexing in SDH∕SONET networks

The new technologies of virtual concatenation, the link capacity adjustment scheme and the generic framing protocol make SDH/SONET survivable in the next-generation transport networks. However, based on synchronous time-division multiplexing, SDH/SONET only creates a private point-to-point path for a particular user that cannot be shared by other users when the path is in the idle state. Therefore it results in bandwidth inefficiency for accommodating bursty services. A new scheme called ‘channel statistical multiplexing’ is proposed. It is simple and practical for use when there are several data streams from the same source node to the same destination node in SDH/SONET networks.

Performance models of statistical multiplexing in packet video communications

Models and results are presented that assess the performance of statistical multiplexing of independent video sources. Presented results indicate that the probability of buffering (or delaying) video data beyond an acceptable limit drops dramatically as the number of multiplexed sources increases beyond one. This demonstrates that statistical or asynchronous time-division multiplexing (TDM) can efficiently absorb temporal variations of the bit rate of individual sources without the significant variations in reception quality exhibited by multimode videocoders for synchronous TDM or circuit-switched transmission. Two source models are presented. The first model is an autoregressive continuous-state, discrete-time Markov process, which was used to generate source data in simulation experiments. The second model is a discrete-state, continuous-time Markov process that was used in deriving a fluid-flow queuing analysis. The presented study shows that both models generated consistent numerical results in terms of queuing performance. >

Simulation Studies for Data Multiplexing in Speech with Stdm or Tasi

A simulation model of a finite buffer queueing system with Erlang arrivals and multiple random servers is presented. The number of active servers in a service interval vary through a birth and death process derived from the speech samples in synchronous time division multiplexing (STDM) or time assignment speech interpolation (TASI) system. The results of this study show that the TASI system requires a larger buffer than the STDM system for a specified overflow probability.

Buffer Behavior for Mixed Arrivals and Single Server with Random Interruptions

A queueing model with finite buffer size, mixed input traffic (Poisson and burst Poisson arrivals), synchronous transmission and server interruptions through a Bernoulli sequence of independent random variables is studied. Using average burst length, traffic intensity and input traffic mixture ratio as parameters, the relationships among buffer size, overflow probability and expected message queueing delay are obtained. An integrated digital voice-data system with synchronous time division multiplexing (STDM) for a large number of voice sources and mixed arrival process for data messages is considered as an application for this model. The results of this study are portrayed on graphs and may be used as guidelines in buffer design problems in digital voice-data systems. The queueing model developed is quite general in a sense that it covers pure Poisson and burst Poisson arrival processes and the mixture of the two as well.

Finite Buffer Behavior with Poisson Arrivals and Random Server Interruptions

A queueing model with finite buffer size, Poisson arrival process, synchronous transmission and server interruptions is studied through a Bernoulli sequence of independent random variables. An integrated digital voice-data system with Synchronous Time-Division Multiplexing (STDM) for voice sources and Poisson arrival process for data messages is considered as an application for this model. The relationships among overflow probabilities, buffer size and expected queueing delay due to buffering for various traffic intensities are obtained. The results of this study are portrayed on graphs and may be used as guide lines for the buffer design in digital voice-data systems. Although this study arose in the design of a buffer for digital voice-data systems, the queueing model developed is quite general and may be useful for other industrial applications.

A finite waiting room queueing model with multiple servers having Markovian interruptions and its application to computer communications

A queueing model with finite waiting room, Poisson arrivals, multiple synchronous outputs and the number of active servers varying through the birth and death process is studied. Variation of active servers is obtained by providing a switch in each server. The switches are controlled through the birth and death process having finite population. The relationships between overflow probabilities, buffer size and expected queueing delay due to buffering are obtained. An efficient algorithm for computation of steady state probabilities is developed. Two digital voice-data systems; Data multiplexing in speech with synchronous Time Division Multiplexing (STDM) and Time Assignment Speech Interpolation (TASI) systems are considered for the application of the queueing model studied. The results of this study are portrayed on graphs and may be used as guidelines for designing a buffer in digital systems. The two voice-data systems using the developed model are simulated on the EC-1030 computer to check the validity of the analytical results. Although this problem arose in the study of data interpolation in STDM and TASI systems, the queueing model developed is quite general and may be useful for other industrial applications.

Three-state Markov model of speech on telephone lines and optimal utilization of communication systems by TASI technique

A three-state Markov model of speech on the telephone lines is developed. The model considers the alternate occurrence of the telephone calls and the intercall gaps on the telephone lines. During a phone call there are several talkspurts (speech without break) and pauses (silence without break) in the user's speech. The three types of events, intercall gaps (large gaps) talkspurts and pauses occurring on the telephone lines are assumed to have negative exponential density functions with different transition rate parameters. The steady state probability distribution, average and variance of the number of busy channels and the system utilization are evaluated as a function of call loss fraction ( P 0 f ). The Synchronous Time Division Multiplexing (STDM) system with number of channels in the group equal to 6 and 24 is considered. The model is also applied to Time Assignment Speech Interpolation (TASI) system and the relationships among the number of user terminals, speech Freeze Out Fraction (FOF) and system utilization are obtained for various values of P 0 f . The STDM and TASI systems applied to the group of 6 channels are simulated on the EC-1030 computer to check the validity of the analytical results. The results of this study are portrayed on graphs and may be used as guide lines in the design of TASI systems.

Performance Models of an Experimental Computer Communication Network

This paper reports the results of a performance study of an experimental computer communication network. The network is currently being designed and built in order to test concepts and techniques that may find future application. The network consists of synchronous digital transmission lines connected in loops to a Central Switch. User traffic enters the system through multiplexers connected to the synchronous lines. The Central Switch has the two-fold function of routing and controlling traffic. Two multiplexing techniques were examined, Demand Multiplexing (DM) and Synchronous Time Division Multiplexing (STDM). In both techniques, user messages are blocked into fixed size packets, prior to multiplexing on the line. The synchronous line can carry these packets at a maximum rate of 4000 packet slots per second. In STDM each terminal is assigned a packet slot which recurs periodically. In contrast, for DM, packets are multiplexed on the line asynchronously into unoccupied packet slots. Alternative implementations of the DM technique were studied, one where each terminal transmits and receives at a maximum rate of 4000 packets per second and another where the maximum rate is 2000 packets per second. As part of its message-handling function, the Central Switch buffers messages in transit. This allows User Terminals to transmit and receive messages with a degree of independence from one another. However, the terminals' strategy affects the amount of storage required in the Central Switch. In order to prevent the loss of information when there is insufficient buffering, there is a mechanism to inhibit traffic from User Terminals when the Central Switch buffer is near overflow. Due to this control of traffic, there is a relationship between the amount of data that flows through the switch and the amount of buffering in the switch.

Multiplexing and concentration

Obtaining a cost-effective teleprocessing network is postulated on efficient utilization of the communication links and processing equipment. A variety of line-sharing devices and procedures are commonly used for this purpose. The functional, economic, and application aspects of frequency-division multiplexing (FDM), synchronous time-division multiplexing (STDM), asynchronous time-division multiplexing (ATDM), message switching concentration (MSC), and line (or circuit) switching techniques are discussed. The motivations for line sharing stem from economies of scale in the cost of bandwidth and from the traffic smoothing effect which such devices produce when serving a large terminal population characterized by unscheduled requests for service. The discussion of these techniques includes a detailed contrast between multiplexing and concentration, two terms which are often (and unfortunately) used synonymously. It is shown that FDM and STDM are examples of conventional multiplexing, whereas message switching and line switching usually illustrate concentration. ATDM is shown to be a hybrid line-sharing scheme embodying certain features of both concepts. Thus it is often referred to as statistical multiplexing. The first part of the paper is devoted to a functional explanation of the various concepts referenced above. The balance of the paper is concerned with applications and systems-design considerations involving multiplexing and concentration techniques. The application section focuses on important economic factors pertaining to the selection and use of the various methods. The role of line-sharing devices in contemporary common-carrier and end-user networks is also considered. The economic and technical aspects of these contrasting application environments are emphasized and illustrate the multiplicity of uses for line-sharing devices. The concluding portion of the paper includes a discussion of system-design considerations. This section illustrates precisely how the decision to use multiplexers or concentrators in a typical computer-communication network is implemented. Various techniques for geographically positioning multiplexers and concentrators to minimize total costs are presented. The use of one of these procedures is demonstrated using a typical design problem as a case study.