![Medium Access Control (MAC) Protocols
The role of the MAC protocol [1] is to determine when
a node is allowed to transmit its packets. It typically
controls all access to the medium.
Wireless MAC protocols have been studied extensively
since the 1970s. The initial protocols were developed for
data and satellite communications.
The two major objectives of a multiple access protocol
are maximization of the channel capacity utilization and
minimization of latency between a station deciding to
transmit and able to transmit.](https://image.slidesharecdn.com/demandassignedmultipleaccess-191219151911/85/Demand-assigned-and-packet-reservation-multiple-access-6-320.jpg)
Demand assigned and packet reservation multiple access
- 1. BY G.GOWRILATHA,M.Sc(Info Tech) Department Of CS & IT Nadar Saraswathi College Of Arts and Science, Theni.
- 2. Demand Assigned Multiple Access • Demand Assigned Multiple Access (DAMA) is a name for a central allocation of network resources. it is an operation process that lies above multiple access processes, because it is an administrative, not a technical function. •Demand Assigned Multiple Access (DAMA) is a name for a central allocation of network resources. DAMA is one of the two main techniques for allocating channels to users. • The most multiple-access systems use DAMA in which the available channels are allocated on an as required basis to users. • DAMA is a technique used to assign satellite channels to on an as request basis.
- 3. Demand Assigned Multiple Access (DAMA) is a technology used to assign a channel 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 party line 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.
- 4. A. Packet Reservation Multiple Access (PRMA) refers to a multiple access strategy with frames of a fixed number of slots. B. In case a terminal contains a set of data packets or speech segments to deliver, it competes to gain access in any free slot. C. In PRMA, adjacent cells make use of distinct carrier frequencies in line with a cellular reuse plan. The fundamental process of PRMA includes occupying a time slot only at the time of speech talkspurts and releasing the channel at the time of silence periods.
- 5. PRMA facts: TDMA with slotted ALOHA reservation system Source rates are 32 kbit/sec Frame Duration is 16 msec ( 62.5 frames/sec) 20 slots per frame Channel bit rate is 720 kbit/sec and bandwidth is 720 khz 576 bits per slot (contains 64 bit overhead) Packet dropping rate is 1% Supports data and voice
- 6. Medium Access Control (MAC) Protocols The role of the MAC protocol [1] is to determine when a node is allowed to transmit its packets. It typically controls all access to the medium. Wireless MAC protocols have been studied extensively since the 1970s. The initial protocols were developed for data and satellite communications. The two major objectives of a multiple access protocol are maximization of the channel capacity utilization and minimization of latency between a station deciding to transmit and able to transmit.
- 7. High throughput- A high network throughput, or high efficiency, is achieved when the protocol has low overhead and low collision probability. It is also equivalent to low frame delay. Scalability- The network throughput should be unaffected by increases in number of nodes. Naturally, the per-node throughput decreases as the number of active nodes increases but ideally, this should follow a linear decrease. Topology independence- The network throughput should be transparent to network topology changes. In high mobility scenarios, where the rate of nodes joining and leaving the network is high, as well as node velocity, the protocol should be able to maintain a high network throughput. Fairness- The protocol should not give priority to particular nodes over the others. Quality of Service (QoS) - When multiple traffic classes are defined, the protocol should be able to manage the bandwidth resources in order to assign different priorities to real-time and besteffort nodes.
- 8. PRMA Model
- 9. CDMA/PRMA Joint Code Division Multiple Access Packet Reservation Multiple Access (CDMA/PRMA) protocol was introduced as a candidate for an uplink protocol for third generation mobile communication. Packet CDMA the time axis is unslotted and packets are granted random access to the channel, in Joint CDMA/PRMA the time axis is slotted, with the slots grouped into frames (as in PRMA) and the access of packets to the channel
- 10. Thank You