Telecommunications Management

Homework 4 Solutions

Answers to questions 8, 9, 10 & 11

  1. Multiplexing combines smaller, lower-capacity data or voice information streams into one large stream to increase capacity utilization.

  2. Frequency Division Multiplexing (FDM) divides the bandwidth of the transmission medium into partitions or slots, each consisting of sufficient bandwidth to carry the required information and have a little left over for buffer against interference. FDM is used for voice signals. Time Division multiplexing (TDM) is used to consolidate and combine multiple digital information streams by interleaving bits from each separate stream into prearranged time slots. TDM is more appropriate for digital signals.

  3. The transmit and receive multiplexers in a synchronous TDM system must be synchronized. This type of TDM is appropriate for constant communication between constant number of devices. Asynchronous (statistical) TDM on the other hand eliminates predetermined time slots. Input from source terminals are buffered in a queue until the multiplexer device scans the input buffer and assigns data to available time slots until the frame is full and then the multiplexed signal is sent on the network. Statistical TDM allows more devices than there are time slots and is appropriate for intermittent and variable communication requirements from multiple sources.

  4. The basic principle behind signal compression techniques is that all forms of information have natural, built-in redundancies which can be temporarily removed when the data is being transmitted. For example in a News Broadcast the background is static and therefore redundant after it has been transmitted once there need not be constantly transmitted


Answer to questions only - You were supposed to do the complete analysis:

  1. The key business drivers that led to the development of Analog Devices' European network were a desire to improve internal coordination and efficiency, upgrade its software, and reduce unnecessary processing and administrative costs. The transmission links selected had to be accessible by all the other business units, which used different systems. This meant that Analog Devices wanted to standardize on X.25.

  2. Dial-up links provided by the international VANs charge by transaction. Dedicated private lines have a fixed charge. The cost is lower. The implication for moving to higher-speed, meant that Analog Devices had to deal with multiple PTTs of several countries.

  3. Analog Devices took eight months to migrate from the dial-up links to the dedicated, private-line backbone network because it wanted to phase the network in very carefully. The time also reflects the difference in speed and quality of service for many international PTTs

  4. A suggestion for Analog Devices on how to deal with unreliable transmission link facilities in some countries in Europe would be to investigate the cost of installing Satellite based systems. These would bypass the unreliable links.

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Ramayya Krishnan