PERFORMANCE OF COMBINED FREE/DEMAND ASSIGNMENT MULTIPLE-ACCESS SCHEMES IN SATELLITE COMMUNICATIONS
✍ Scribed by LE-NGOC, THO ;KRISHNAMURTHY, S. V.
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 795 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0737-2884
No coin nor oath required. For personal study only.
✦ Synopsis
By combining free assignment with demand assignment, the combined Ereeldemand assignment multipleaccess (CFDAMA) protocol offers a much shorter delay at low and medium traffic loads while maintaining the high channel utility of the demand-assignment multiple-access (DAMA) technique. In these schemes, reservation can be made using pre-assigned (PA) or random-access (RA) request slots, or piggy-backing (PB) the request on a data packet. This paper presents a performance analysis of CFDAMA schemes in packet satellite communications. Illustrative examples are given. They show a good agreement between analytical and simulation results. For low and medium sizes of terminal population, the CFDAMA-PA scheme has an excellent delay-throughput performance. As the terminal population increases, its performance is gradually degraded due to the long waiting time for a request. For a very large number of terminals, the CFDAMA-RA becomes more effective than CFDAMA-PA. This indicates that a CFDAMA scheme using a hybrid PB/RA requesting protocol can provide the best performance for a wide range of terminal population sizes. KEY WORDS: multiple-access techniques; packet satellite communications; performance *CFDAMA protocols can be applied to both bent-pipe (nonregenerative) and on-board processing (OBP) satellites. For new generation satellites with OBP capability a centralized scheduler can be located in the satellite so that it takes the requesting terminal only one round-trip delay plus the scheduler queueinglprocessing time to receive the reply to its reservation. For bent-pipe satellites the scheduler should be on the ground. We could have a centralized (on-ground) scheduler. In this case it takes the requesting terminal two round-trip delays plus the scheduler queueing delay. We could also use a distributed scheduling scheme in which all terminals perform an identical scheduling procedure. This is possible in a global-beam satellite system. Using a distributed scheduling scheme it takes the requesting terminal only one round-trip delay plus queueinglprocessing time to obtain its allocation.