Multiple Access Schemes are methods that let multiple devices share a communication channel without collisions.
They ensure fair and efficient use of the channel.
- FDMA (Frequency Division Multiple Access): Users get separate frequencies. Like radio stations on different channels.
- TDMA (Time Division Multiple Access): Users take turns in time slots. Like people talking on a conference call.
- CDMA (Code Division Multiple Access): Users send data with unique codes. Like people talking in different languages.
These schemes manage how users share a channel to transmit and receive data without interfering with each other.
Comparison between FDMA and TDMA
| Aspect | FDMA | TDMA |
| Basic Concept | Divides frequency spectrum into non-overlapping frequency bands for users. | Divides time into discrete slots for users. |
| Interference | Interference occurs if signals overlap in frequency. | Interference occurs if signals overlap in time. |
| Resource Allocation | Each user gets a fixed frequency band. | Users share the same frequency band but take turns using it. |
| Efficiency | Bandwidth can be unused if traffic is low for some users. | Efficient for bursty traffic, as users transmit only in their allocated time slots. |
| Complexity | Requires precise frequency control to avoid overlap. | Requires synchronization to allocate time slots correctly. |
| Examples | Cellular networks (different channels for users). | GSM (Global System for Mobile Communications) – users share channels with time slots. |
| Analogous Scenario | Different radio stations on separate frequencies. | People taking turns speaking in a conference call. |
| Advantages | Simple frequency allocation, suitable for voice communication. | Efficient use of bandwidth, adaptable to changing traffic. |
| Disadvantages | Inefficient for bursty data, limited users per frequency band. | Requires synchronization, complex in high-mobility scenarios. |