There are various types of switching that are used in communication (networking devices) so that the data is transferred only to the host. Switching techniques are expensive if compared to network bridges but at the same time using switches helps in increasing the bandwidth of the network as well as the overall performance of the network.
Space Division Switching vs Time Division Switching
The main difference between space division switching and time division switching is that space division switching is a technique that can be implemented for both analog and digital networks. On the other hand, the time-division switching mechanism is only available for digital networks.
In space division switching, the paths are separated from each other spatially in a circuit. Crosspoint is a very important concept in space division switching as it is the switch that moves the bitstream from one circuit/bus to another. There are several Crosspoints present in the Crosspoint matrix that connects the incoming and outgoing PCM highways.
To establish a call through time-division switching, its principle is to connect the input of any PCM highway to the output of any PCM highway. Time-division switching is not instantaneous meaning that the input signals are retransmitted at a different time slot (data is transferred in fixed time intervals).
Comparison Table Between Space Division Switching and Time Division Switching
What is Space Division Switching?
Space division switch is used to establish a continuous connection between the incoming and outgoing channels for the transfer of information. In this type of switching, the Crosspoint (it can be turned on and off) is referred to as the space division switch and the number of Crosspoints increases with an increased number of established networks. This creates an inconvenience because the total number of Crosspoints that are required to develop space-division switching is acceptable in terms of blocking.
Moreover, if one Crosspoint is lost, the connectivity is compromised. There is one way to reduce the number of Crosspoints for a large outlet by limiting the number of outlets that can be accessed by each inlet. This process is known as limited availability. In space division switching, a crossbar is the simplest form of space-division switch that can be used and the output from a crossbar switch can again be fed into the crossbar switches.
Space division switching was originally built for analog networks but after certain modifications, it has been implemented in digital communication as well. When space division switching is used in digital communication, a separate physical path for each signal is required and it used metallic or semiconductor gates.
What is Time Division Switching?
In time-division switching, there are no Crosspoints but at the same time, it introduces a delay between the transfer of input and output signals. These are two factors that mainly distinguish space division and time division switching techniques. In time-division switching, a great saving is done in terms of Crosspoints a single switching element can be assigned to multiple inlet-outlet pairs but only for a few microseconds. Another unique factor in time-division switching is that the information that is to be transferred is sliced up into a sequence of time intervals and then they are sent in fixed intervals of time frame.
The concept of Crosspoints is a variable for time-division switching. In some cases, they are not present and in networks where they are present, they can be shared unlike space division switching such that the Crosspoints can be reassigned for other connections. This increases the overall efficiency of the mechanism.
Time-division multiplexing is an important concept in time-division switching. Time-division multiplexing is a method by which multiple data streams can be put into a single signal and then this signal is separated into multiple segments and they appear for a very short duration.
Main Differences Between Space Division Switching and Time Division Switching
- In space division switching, the path established between two devices is continuous during the exchange whereas in time-division switching signals are sent at fixed intervals.
- Space division switching is instantaneous whereas time-division switching has a processing delay.
- Space division switching uses Crosspoints that are not shared whereas in time-division switching there is no use of Crosspoints.
- Space division switching is applicable for both analog and digital networks whereas time-division switching is only for digital networks.
- In space division switching, there is no time difference between the transfer of the coded values from input to output whereas, in time-division switching, the coded values are stored and then transferred.
Conclusion
Space division switching is more versatile in terms of fields where it can be used, i.e., both analog and digital. But at the same time, time division switching doesn’t have the complication of Crosspoints. But, instead of using space and time division switching, a combination switch can be also be built. A combination switch is comprised of a certain number of time and space switches. This combination switch is known as a two-stage combination switch where either of the switches (space or time) can be used as the first stage. Some of the combinations are time-space-time (TST) and space-time-time-space (STTS).
References
- https://ieeexplore.ieee.org/abstract/document/5390353/
- https://ieeexplore.ieee.org/abstract/document/365223/