Multiple access schemes are used to allow many mobile users to share simultaneously a finite amount of radio spectrum. In wireless communication systems, it is often desirable to allow the subscriber to send information simultaneously from the mobile station to the base station while receiving information from the base station to the mobile station. A cellular system divides any given area into cells where a mobile unit in each cell communicates with a base station. The main aim in the cellular system design is to be able to increase the capacity of the channel , i. There are several different ways to allow access to the channel. Depending on how the available bandwidth is allocated to the users, these techniques can be classified as narrowband and wideband systems.
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I can't believe how simple your reconditioning steps are! My old and once dead car batteries, cell phone battery, drill battery, camera battery and tons of other batteries are all reconditioned and working great again! Show More. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. This is done by assigning active users a different frequency channel. Frequency division multiplexing 5.
This space is called a guard band. Channel assignment is carried out on a first-come first- served basis. These guard bands can be used to minimize adjacent channel interference. It allocates a single frequency channel for a short time and then moves to another channel.
From this signals, mobile stations can determine when their turn comes up. This results in low battery consumption since the subscriber transmitter can be turned OFF when not in use. It carry data rates of 64 kbps to Mbps. It provides the user with extended battery life and talk time. It is the most cost effective technology to convert an analogue system to digital. TDMA technology separates users according to time, it ensures that there will be no interference 5.
TDMA allows the operator to do services like fax, voice band data, and SMS as well as bandwidth-intensive application such as multimedia and videoconferencing. Each user has a predefined time slot. When moving from one cell to other, if all the time slots in this cell are full the user might be disconnected.
It is subjected to multipath distortion. A signal coming from a tower to a handset might come from any one of several directions. It might have bounced off several different buildings before arriving. In other words, CDMA will use the resource the radio spectrum more efficiently. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips. Visibility Others can see my Clipboard.
Wireless Communication - Multiple Access
Multiple Access Schemes for Cellular Systems
Time-division multiple access TDMA is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. This allows multiple stations to share the same transmission medium e. TDMA was first used in satellite communication systems by Western Union in its Westar 3 communications satellite in It is now used extensively in satellite communications,     combat-net radio systems, and passive optical network PON networks for upstream traffic from premises to the operator.