by Dinesh Thakur Category: Multiple Access

In case of TDM, time slots are allocated to channels, even if they have no information to transmit. This is just wastage of the bandwidth and to overcome this inefficiency of standard TDM, a technique known as STDM has been developed where time is allocated to lines only when it is required. This is achieved with the use of intelligent devices that are capable of identifying when a terminal is idle.



 
by Dinesh Thakur Category: Multiple Access

For digital sources, two alternative technologies have evolved for multiplexing. These are Time Division Multiplexing (TDM) and Code division Multiplexing (CDM). TDM provides a way to merge data from several sources into a single channel for communication over telephone lines, a microwave system or a satellite system. TDM can be implemented in two ways. These are synchronous TDM and asynchronous TDM. Asynchronous TDM is popularly known as Statistical TDM.

 
by Dinesh Thakur Category: Multiple Access

In Frequency Division Multiplexing (FDM), multiple channels are combined onto a single aggregate signal for transmission. The channels are separated in the aggregate by their frequency. It is explained in the Figure where a frequency dimension is subdivided into several non-overlapping frequency bands. Each channel ci is allotted its own frequency band as depicted in Figure.

 
by Dinesh Thakur Category: Multiple Access

CDMA (Code Division Multiple Access) also called spread-spectrum and code division multiplexing, one of the competing transmission technologies for digital MOBILE PHONES. The transmitter mixes the packets constituting a message into the digital signal stream in an order determined by a PSEUDO-RANDOM NUMBER sequence that is also known to the intended receiver, which uses. it to extract those parts of the signal intended for itself. Hence each different random sequence corresponds to a separate communication channel. CDMA is most used in the USA.

 
by Dinesh Thakur Category: Multiple Access

• In TDMA, the bandwidth of channel is dividend amongst various stations on the basis of time.

• Each station is allocated a time slot during which it can sent its data i.e. each station can transmit its data in its allocated time slot only.

 
by Dinesh Thakur Category: Multiple Access

• In FDMA, the available bandwidth is divided into various frequency bands.

• Each station is allocated a band to send its data. This band is reserved for that station for all the time.

 
by Dinesh Thakur Category: Multiple Access

• CSMA/CA protocol is used in wireless networks because they cannot detect the collision so the only solution is collision avoidance.

• CSMA/CA avoids the collisions using three basic techniques.



 
by Dinesh Thakur Category: Multiple Access

To reduce the impact of collisions on the network performance, Ethernet uses an algorithm called CSMA with Collision Detection (CSMA / CD): CSMA/CD is a protocol in which the station senses the carrier or channel before transmitting frame just as in persistent and non-persistent CSMA. If the channel is busy, the station waits. it listens at the same time on communication media to ensure that there is no collision with a packet sent by another station. In a collision, the issuer immediately cancel the sending of the package. This allows to limit the duration of collisions: we do not waste time to send a packet complete if it detects a collision. After a collision, the transmitter waits again silence and again, he continued his hold for a random number; but this time the random number is nearly double the previous one: it is this called back-off (that is to say, the "decline") exponential. In fact, the window collision is simply doubled (unless it has already reached a maximum). From a packet is transmitted successfully, the window will return to its original size.



 
by Dinesh Thakur Category: Multiple Access

NRZ-L (No return to zero level): this kind of encoding uses negative voltage to represent a binary 1 and positive voltage to represent a binary 0. As shown under: non return to zero is related with the voltage i.e. voltage never returns to a value of zero and the value of the voltage during a bit time is known as level. bit time is related with the amount of time one bit of data occupies.

 
by Dinesh Thakur Category: Multiple Access

Multiplexing or (muxing) - To combine multiple signals (analog or digital) for transmission over a single line or media. A common type of multiplexing combines several low-speed signals for transmission over a single high-speed connection. In other words, we can say that Muxing is used for sharing of a medium and its link by two or more devices. It can provide both Efficiency and Privacy.

 
by Dinesh Thakur Category: Multiple Access

Telephone line or telephone circuit (or just line or circuit within the industry) is a single-user circuit on a telephone communication system. Typically this refers to the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user.

 
by Dinesh Thakur Category: Multiple Access

Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite is the engine for the Internet and networks worldwide. Its simplicity and power has led to its becoming the single network protocol of choice in the world today. TCP/IP is a set of protocols developed to allow cooperating computers to share resources across the network. 



 
by Dinesh Thakur Category: Multiple Access

Carrier Sensed Multiple Access (CSMA) : CSMA is a network access method used on shared network topologies such as Ethernet to control access to the network. Devices attached to the network cable listen (carrier sense) before transmitting. If the channel is in use, devices wait before transmitting. MA (Multiple Access) indicates that many devices can connect to and share the same network. All devices have equal access to use the network when it is clear.

 

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.