Question

What advantage does a circuit-switched network have over a packet-switched network? What advantages does TDM have over FDM in a circuit-switched network?

Short answer

Circuit-switched networks offer guaranteed bandwidth and low latency; TDM efficiently uses bandwidth in such networks.

Step-by-step solution

Understanding Circuit-Switched Networks

Circuit-switched networks establish a dedicated communication path between nodes. This means once the circuit is established, it remains open and is used for the entire duration of the communication session, ensuring a constant data rate and minimal delay.

Advantages of Circuit-Switched Networks

In circuit-switched networks, there is guaranteed bandwidth throughout the duration of the session. This means that data can be sent in a consistent and predictable manner, with minimal latency. These networks are ideal for real-time voice conversations, where continuous and uninterrupted transmission is critical.

Understanding Packet-Switched Networks

Packet-switched networks divide data into packets and send each packet independently through the network. The packets may travel different paths to reach the destination, and they are reassembled in the correct order upon arrival.

Comparing Circuit-Switched and Packet-Switched Networks

Compared to packet-switched networks, circuit-switched networks provide lower latency and guaranteed delivery rates since the path is established for the entire session. Packet-switched networks may experience varying delays and possible packet loss due to network congestion.

Time-Division Multiplexing (TDM)

TDM allocates specific time slots to each communication channel on the same frequency. Each channel transmits in rapid succession, appearing simultaneous to end users. It is suitable for systems with consistent and predictable data flow, like voice communications.

Frequency-Division Multiplexing (FDM)

FDM assigns individual frequency bands to different communication channels. Each channel transmits at a different frequency, allowing multiple signals to be sent simultaneously but requiring more bandwidth.

Advantages of TDM in Circuit-Switched Networks

In circuit-switched networks, TDM efficiently uses the available bandwidth by allocating time slots instead of separate frequency bands needed in FDM. This reduces the need for extensive filtering, simplifies hardware, and efficiently manages the network's capacity for predictable data flows.

Key concepts

Packet-Switched Networks

Imagine sending a letter through the mail, where each sentence of your letter goes in a different envelope. This is similar to how packet-switched networks function. Data is divided into packets, which are small chunks of the total message. Each packet travels independently across the network and can take different paths to reach its destination. This method allows the network to be highly flexible and efficient because it makes use of available paths and avoids congested areas.

Packet-switched networks excel in handling large amounts of data and varied types of communication, such as voice calls, video streaming, and web browsing. They optimize the use of network resources even during peak times, bringing efficiency in data transmission.

• Packets can travel via different routes, leading to possible faster rates.
• Users don't need a dedicated line, saving network capacity for others.

However, unlike circuit-switched networks, packet-switching may involve delays. This is because packets might arrive in a different order at the destination and need reassembling. Sometimes, packets get lost due to network congestion, resulting in possible data loss or requires retransmission.

Time-Division Multiplexing (TDM)

In a busy restaurant, imagine that each table gets a few minutes of the server's time on a rotating basis to place orders and get what they need. This is similar to Time-Division Multiplexing (TDM), where time slots are allocated in a fixed sequence for different communication channels on the same frequency. Each channel is given a short time to transmit data before the next channel takes a turn.

TDM is particularly beneficial in environments where data is consistent and predictable, such as voice calls. Its structured nature ensures that every channel gets regular and equal opportunities to transmit data without interference.

• Efficient bandwidth usage by scheduling transmissions at different times.
• Simplified network infrastructure, reducing the need for complex filtering systems.

By using time slots, TDM in a circuit-switched network guarantees a steady and reliable communication channel even when there are multiple users.

Frequency-Division Multiplexing (FDM)

Think of an orchestra, where each musician plays different notes at the same time but on different instruments. Frequency-Division Multiplexing (FDM) works in a similar manner by dividing the available bandwidth into distinct frequency bands. Each communication channel transmits signals in its own unique frequency band, allowing multiple signals to coexist on the same channel.

FDM is useful in scenarios where the demand for bandwidth is high but predictable and consistent. It allows multiple transmissions concurrently without interference, making it well-suited for broadcasting scenarios.

• Simultaneous transmission of multiple signals by assigning unique frequency bands to each.
• Minimized interference due to separate frequency channels for each signal.

However, FDM requires more bandwidth and complex hardware to separate and recombine the signals accurately, and can be less efficient than TDM in scenarios with lower bandwidth availability.