Multiple Access Techniques in Satellite Communication

In the world of modern communications, the need to manage multiple messages, data, streams, and processes simultaneously provides critical capability in meeting the needs of widespread business and consumer demand. One of the ways these benefits occur involves satellites and their internal programming that acts as a super-size highway router of information traffic worldwide. To make this happen, satellites are built with the capability to function in different formats.

Multiple Access Defined

Multiple access in satellite terms involves running communication streams between multiple satellite conduits or terminals at the same time. Normally, in simple traffic a terminal only handles one stream at a time. This approach doesn’t work when a satellite’s owner needs it to function managing thousands of points simultaneously. As a result, satellite technology today works with three different systems that offer multiple access ability.

The Benefits

For cell phone service providers, broadband providers, the military, government agencies, research agencies, businesses using satellite communications, and even media providers the benefits of multiple access provide significant ability to meet various goals. Being able to connect with multiple terminals simultaneously allows faster and more widespread access, data sharing, and communication. For cell phones, for example, multiple processing is the bread and butter capability of the cell phone business. Those who can’t maintain their service to multiple customers reliably soon fade away under a competitive technology market.

Prioritizing Traffic

Even with satellites that are capable of automatically managing simultaneous traffic points, companies don’t necessarily allow everyone’s traffic to pass at the same time. If they did, the satellite resources would run slower and could get bogged or shut down with a basic surge in traffic beyond normal patterns.

Protocols

Satellite programming control occurs with using what is called protocols. These controls, also known as media access control (MAC), function like a stop light in a street square; they manage direction, assign traffic flow, slowdown lower priority data temporarily for higher priority, and the keep the traffic moving without clogging up and overloading the systems. Remember, even satellites are only as good as the throughput their traffic must go through, these routing points become bottlenecks when too much traffic flows uncontrolled at the same time.

Methods of Control

As mentioned earlier, common techniques used for multiple access stream control include frequency-division multiple access (FDMA), time-division multiple access (TDMA), code-division multiple access (CDMA), and packet (or random) access. Each method has plusses and minuses with regards to how it works. Depending on what a satellite owner wants from the system, their technical managers will use a particular control approach to provide the results. However, it’s not one approach fits all; satellite systems can run different control methods at the same time on different layers. So higher priority traffic can be running at one level with one control, and lower priority traffic could run on another. A typical example would be military or government sensitive channels taking priority over consumer cell phone traffic or satellite cable TV programming.

 

References

1.http://www.yorku.ca/bartel/3250/f11/introsat7.pdf

2.http://www.cs.utexas.edu/users/lam/Vita/Jpapers/Lam79.pdf

 

 

 

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