Demand Assigned Multiple Access

DAMA - Mobile and Wireless Communication

1. INTERNATIONAL INSTITUTE OF PROFESSIONAL STUDIES DAVV INDORE Mobile and Wireless Computing Internal Test III Name - Anushka Shastri Roll No - I T-2K17-09 Batch - MTech 2k17 Semester - VIII Guided By - Ms. Manju Sachdeo Ma'am Date - 24/05/2021

2. Demand Assigned Multiple Access 24/05/2021

3. Multiple Access: We do multiple access to enable satellite to take or give signals from different stations at time without any interference between them.

4. Multiple Access Sometimes a satellite’s service is present at a particular location on the earth station and sometimes it is not present. That means, a satellite may have different service stations of its own located at different places on the earth. They send carrier signal for the satellite. In this situation, we do multiple access to enable satellite to take or give signals from different stations at time without any interference between them. FDMA (Frequency Division Multiple Access) TDMA (Time Division Multiple Access) CDMA (Code Division Multiple Access)

5. What is DAMA ? Full form - Demand Assigned Multiple Access Channel Allocation Technique There are two channel allocation techniques - PAMA - Permanent Assigned Multiple Access DAMA - Demand Assigned Multiple Access

6. DAMA DAMA is a technique used to assign satellite channels to on an as request basis. The most multiple-access systems use DAMA in which the available channels are allocated on an as required basis to users.

7. DAMA Demand Assigned Multiple Access (DAMA) is a technology used to assign a to clients that don't need to use it constantly. DAMA systems assign communication channels based on news issued from user terminals to a network security system. Channels are typically a pair of carrier frequencies (one for transmit and one for receive), but can be other fixed bandwidth resources such as timeslots in a TDMA burst plan or even physical channels. Once a channel is allocated to a given pair of nodes, it is not available to other users in the network until their session is finished.

8. How DAMA works ? Demand access systems require two types of a channel: a common signaling channel (CSC) and a communication channel. A user wishing to enter the communication network first calls the controlling earth station using the CSC, and the controller then allocates a pair of channels to that user. The CSC are located at the ends of the transponder bandwidth. When earth station wants to access the satellite, it transmits a control packet to satellite on the CSC Frequency & waits for a reply.

9. How DAMA works ? The control packet is received by the hub earth station and decoded. The control packet contains source address & destination address also it includes cyclic redundancy check (CRC). The control station measures duration of the connection.

10. Advantages of DAMA Prior Reservation A sender reserves a future time-slot Increased Efficiency Less Collision Reservation can increase efficiency to 80% Sending within this reserved time-slot is possible without collision

11. Reservation Algorithms Explicit Reservation Implicit Reservation (PRMA) Reservation-TDMA

12. Access method DAMA: Explicit Reservation Two modes: ALOHA mode for reservation: competition for small reservation slots, collisions possible r eserved mode for data transmission within successful reserved slots (no collisions possible) It is important for all stations to keep the reservation list consistent at any point in time and, therefore, all stations have to synchronize from time to time.

13. Access method DAMA: Explicit Reservation

14. PRMA Packet Reservation Multiple Access a certain number of slots form a frame frames are repeated stations compete for empty slots according to the slotted aloha principle once a station reserves a slot successfully, this slot is automatically assigned to this station in all following frames as long as the station has data to send competition for this slots starts again as soon as the slot was empty in the last frame

15. PRMA

16. Reservation-TDMA every frame consists of N mini-slots and x data-slots every station has its own mini-slot and can reserve up to k data-slots using this mini-slot (i.e. x = N * k). other stations can send data in unused data-slots according to a round-robin sending scheme (best-effort traffic)

17. Uses of DAMA Military for satellite communications (SATCOM) Remote location Internet access and mobile maritime communications. VSAT systems for point of sale (POS) transactions such as credit card, polling or radio frequency identification

18. How DAMA differs from Multiplexing? Multiplexing Divides a single communication channel into multiple channels DAMA Assigns a pair of frequencies to a user terminal Multiplexing Technical process DAMA Administrative process

19. Conclusion DAMA assigns a pair of frequencies to a user terminal. Then, the frequencies are returned to a list, or central pool, of frequencies available to other terminal users. The number of transient clients that use DAMA network terminals increases according to efficient user sequencing at specific frequencies and different timeslots. Thus, DAMA is used for infrequently-used networks. DAMA does not require continuous connection from user terminals to a network control system.