RF Terminology » Satellite Communication » PAMA vs. DAMA vs. RMA: Satellite Resource Sharing Techniques
PAMA vs. DAMA vs. RMA: Satellite Resource Sharing Techniques
satellite communication
multiple access
resource allocation
pama
dama
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This page provides a comparison of PAMA (Pre-Assigned Multiple Access), DAMA (Demand-Assigned Multiple Access), and RMA (Random Multiple Access) techniques used in satellite communication for resource sharing and assignment. These multiple access techniques enable multiple VSATs (Very Small Aperture Terminals) or Earth Stations to utilize shared satellite resources efficiently.
| Feature | PAMA (Pre-Assigned Multiple Access) | DAMA (Demand Assigned Multiple Access) | RMA (Random Multiple Access) |
|---|---|---|---|
| Definition | Resource assignment is planned in advance. | Resource assignment happens upon request from users via a NOC (Network Operation Center). | No pre-assignment needed. |
| Assignment Duration | Long duration assignments, typically months or years. | Assignments last for the duration of a call or data burst. | Connectivity exists only during the burst or packet transmission. |
| Resource Usage | Long-term, exclusive assignment of resources (time/frequency/code). | Temporary, exclusive assignment of resources (time/frequency/code). | Resources are assigned on a shared, contention-based basis. |
| Analogy | Similar to a leased line in a terrestrial telephone network. | Similar to a dial-up line in a terrestrial telephone network. | Similar to a private communication exchange network for telephone applications. |
| Example | INSAT FDMA for TV/Radio Network. | INMARSAT space system. | ALOHA-based data collection terminal systems. |
| Application | AM/FM/TV broadcasting. | Mobile telephone applications in GSM/CDMA networks. | Private communication, amateur radio. |
| Merits | • Low earth station costs and controlled backoff. • Usable for constant bit rate applications | • Efficient use of resources as they are allocated only when needed. • Economical as you pay based on usage. | • Very small earth station equipment. |
| Demerits | • Wastage of resources if not fully utilized. • Not economical if service is not continually used. • Not flexible to actual traffic conditions and resource inefficient. | • More complex system required at the earth station, as the entire network operation is controlled by the control station. | • No control over users leading to potential Interference/collision/blocking. |
Advantages and Disadvantages in Detail
PAMA (Pre-Assigned Multiple Access)
- Merit: PAMA networks offer lower earth station costs due to the simpler equipment requirements. Additionally, backoff (reducing power to prevent interference) can be carefully controlled.
- Demerit: A significant drawback of PAMA is the potential for resource wastage if assigned resources are not consistently used. This makes it less economical if the service isn’t utilized frequently. PAMA’s inflexibility to fluctuating traffic conditions also contributes to its inefficiency.
DAMA (Demand Assigned Multiple Access)
- Merit: DAMA excels in efficient resource utilization. Resources are allocated only for the duration of the call or data transmission, optimizing their use. This leads to economic advantages, as users are charged based on actual usage.
- Demerit: DAMA systems are more complex, particularly at the earth station. A control station manages the entire network operation, increasing the complexity and cost of the earth station equipment.
RMA (Random Multiple Access)
- Merit: The primary advantage of RMA lies in the simplicity of the earth station equipment, making it very compact and cost-effective.
- Demerit: The major disadvantage is the lack of user control. This can result in interference, collisions, and blocking, especially when multiple users attempt to transmit simultaneously.
