Which of the following is a method of multiplexing data where a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. This method allocates bandwidth dynamically to physical channels having information to transmit?

Statistical multiplexing, also known as statistical time-division multiplexing (STDM), is a communication channel sharing method that allocates bandwidth dynamically. Unlike traditional time-division multiplexing (TDM) which uses fixed time slots, statistical multiplexing allocates time slots on an as-needed basis to users who have data to transmit. This approach is highly efficient for bursty data traffic from variable bit-rate sources, as it leverages the statistical probability that not all users will transmit simultaneously, thereby accommodating more users on a shared channel. This directly matches the question's description of dynamic allocation for an arbitrary number of variable bit-rate streams.

A. Time-division multiplexing: This method allocates a fixed, pre-determined time slot to each channel in a round-robin fashion, regardless of whether the channel has data to send. It is a static, not dynamic, allocation method.

B. Asynchronous time-division multiplexing: While often used synonymously with statistical multiplexing, "statistical multiplexing" is the more precise and fundamental term describing the method based on traffic statistics. ATDM is a specific implementation of this principle.

D. Frequency division multiplexing: This method divides the channel's bandwidth into distinct, non-overlapping frequency bands, with each channel assigned a dedicated band. This allocation is static and based on frequency, not time.

1. Kurose

J. F.

& Ross

K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson.

Page 33

Section 1.3.2: "Packet switching also makes use of statistical multiplexing... In a TDM link

each host gets a dedicated rate of R/N bps during every time frame... With statistical multiplexing... there is no a priori reservation of a link’s capacity." This source distinguishes statistical multiplexing's dynamic

on-demand nature from TDM's fixed allocation.

2. Tanenbaum

A. S.

& Wetherall

D. J. (2011). Computer Networks (5th ed.). Prentice Hall.

Page 135

Section 2.5.2: "A variation of TDM is statistical TDM

in which slots are allocated to lines dynamically... The statistical TDM scans the input lines and collects data until a frame is full

and then it sends the frame." This directly describes the dynamic allocation method for channels with data.

3. Stallings

W. (2014). Data and Computer Communications (10th ed.). Pearson.

Page 243

Section 8.2: "In statistical time-division multiplexing

time slots are allocated dynamically on the basis of need... The statistical multiplexer can absorb peak rates of a number of the attached devices

providing a better response time than a synchronous TDM system." This confirms the dynamic

on-demand allocation for variable traffic.