Cdma basics ppt link

01.02.2019 2 By Akinokree

cdma basics ppt link

CONTENTS o CELLULAR COMMUNICATION Multiple Access Method CDMA Introduction o CDMA NETWORK ARCHITECTURE o CALL. Outline: History And Introduction Multiple Access Method – FDMA/TDMA/CDMA Comparison Spread Spectrum CDMA Introduction. Cellular Network Basics . Links the system to PSTN and other operators IMSI code is used to link the MSISDN number to the subscriber's SIM (Subscriber Identity CDMA 1x. GSM Evolution to 3G. GSM. kbps (one timeslot). Code Division Multiple Access (CDMA) is a radically new concept in wireless INTRODUCTION TO SPREAD SPECTRUM COMMUNICATIONS. CDMA is a .. connection can be one of many types of data, but for simplicity we will refer to any .

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The possibility to operate in either FDD or TDD mode is allowed for efficient use of available spectrum according to frequency allocation in different regions. Nominal value of MHz. This value can be either fixed or variable minimum of Time division duplex is cdma basics ppt link technique by which the Uplink and the Downlink transmissions are carried over the same frequency by using synchronized time intervals.

In case of Time Division Duplex, the forward link frequency is same as the reverse link frequency. TDD uses a single frequency band for both to transmit and to receive. Further, it shares the band by assigning alternate timeslots for transmitting and receiving operations.

The information to be transmitted can be voice, video, or ihbi themes data in bit-serial format. Each time interval can be 1 byte long or may be a part of several bytes.

TDD alternates the transmission and reception station data over time. Timeslots can be of variable length. Due to the nature of high-speed data, the communicating parties cannot mean that the transmissions are intermittent. Transmissions that appear as simultaneous are actually competing each other. Digitally converted into analog voice, no one can say that it is not a full duplex.

The system may be asymmetrical as required. For example, while accessing the Internet, the download speed is usually higher than the upload speed. Most of the equipment work on asynchronous mode where the download speed is higher than the upload speed. When the download speed is higher than cdma basics ppt link upload speed, less timeslots are needed for uploading. Some TDD formats offer dynamic bandwidth allocation when the number of time intervals or durations is changed on the fly as needed.

The disadvantage is that the successful implementation of TDD requires a timing system. The precise timing to both the transmitter and the receiver is needed to ensure that the time intervals do not overlap or interfere with another.

Timing is often synchronized to GPS atomic clock standards specific derivative. The guard time is also needed between timeslots to avoid duplication. This time is generally equal to the transmission-reception processing time transmission-reception switching time and the transmission delays latency on the communications channel. In each link, signals are continuously transmitted in cdma basics ppt link.

In a cell phone with a transmitter and receiver, operating simultaneously in such close proximity, the receiver has to filter as much of the signal from the transmitter as possible. More separation of the spectrum, the most effective filters. In addition, there must be adequate spectrum separation between transmission and reception of the channels. Given the scarcity cdma basics ppt link cost of the spectrum, they are real disadvantages. FDD is widely used in different cellular telephone systems.

In some systems, the band MHz is used as the downlink DL spectrum from the cell site tower to the device. And, the band MHz is used as the uplink UL spectrum of the handset at the cell site. FDD also works on a cable where transmit and receive channels are given different parts of the cable spectrum, as in cable TV systems. And, filters are used to keep the channels separate.

It is difficult to make broad enough bandwidth to cover both sets of antenna spectrum. Circuit complex dynamic adjustment is required. The radio channel is a communication medium shared by several users in a geographic area. Mobile stations are in competition with one another for the frequency resource to transmit their information flow. Cdma basics ppt link other measures to control concurrent access of several users, collisions can occur.

The mobile communication, sharing wireless resources on all users, must be communicated to identify the user. While identifying the user, it is referred to as "multiple access" Multiple Access that is receiving a radio wave of a number of transmitting stations in a receiving station as shown in the following image. We use cookies to provide and improve our services.

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Co-channel users. In a bandwidth limited system the only way to increase capacity or data rate is to do one or both of the following: CDMA megatune 2.25 p1 by maximizing the bandwidth.

It allows some simple conclusions to be drawn. Physical Channel The 3 dB bandwidth of a channel is the frequency range where the signal at the edges is 3 dB lower than the peak value at the center frequency. DSSS Spreading: Walsh Code 23 1. What we do. Receiver intercepts the stream. Whether in cdma basics ppt link and receiving, or in CDMA, packaging is extremely important! CDMA combines three different spreading sequences to create unique, robust channels.

The sequences are easy to generate on both sending and receiving ends of each link. Orthogonal functions have zero correlation. The PN short code on the forward link is used to provide the base station with a unique identification that the mobile station uses to identify the serving base station. The user signal or control channel is multiplied by the Walsh code. The Walsh code provides each user or channel with a unique identifier and. One of the codes used in conjunction with the Walsh Code is the PN pseudo-random noise short code.

Main process: In addition to being scrambled. CDMA uses power control to adjust the transmitted power in order to overcome the fades. If the set of reflected signals have one dominant component.

Note that if the mobile speed is zero. This type of variation is called Rayleigh fading This can cause large blocks of information to be lost. FEC encoding and bit interleaving are used. Power control is too slow for the fast Rayleigh fading. For slow fading. Rayleigh Fading In addition to delay spread. Each finger can independently recover a particular PN offset and Walsh code.

Searcher continuously checks pilots. Power Control Is Required? Is handset too strong? Between different frequency. Soft handoff. Soft Soft. Pilots mobile requested. Pilots cdma basics ppt link to mobile by system. Any pilots used by system but not already in the other sets Handset sends Pilot Strength Measurement Message to the system whenever: On the new paging channel.

This step is only used if speech information is transmitted. Data transmission omits this step. The product of Nyquist sampling is a digital waveform called PCM pulse code modulation. Since the transmitter only transmits the lowest bit rate required. Speech encoding In order to transmit speech over a digital system. In CDMA. The analog signal is converted into a cdma basics ppt link signal using a process called Nyquist sampling.

The PCM forklift video is transferred to a vocoder voice coder. Normal speech is received as an analog signal. Frame Information bits are grouped into frames.

Sync Channel. Traffic Channel. The length of a frame depends on what channel on which it is transmitted e. A frame is the basic timing interval in the system. Basics CDMA. Flag for inappropriate content.

Jump to Page. Search inside document. Telegraphy Telephony. Radio Milestones. GSM Vs. Frequency Reuse. GSM f7 7 cell re-use pattern cdma basics ppt link f1 f5 f3 f2 f6 f1 f5 f4 f7 f2 f4 f3. Types of Code. Short code. Usage of code. Need for Synchronisation. Channel Contd. Forward channel. Reverse Channel. Forward Link. Putting it All Together: CDMA Channels.

Code Channels in the Reverse Direction. Variable rate vocoder. How does it cdma basics ppt link The Pilot Searching Process. Handoff Signaling. Reverse link. Forward link. Processing Gain. Capacity Enhancement. Capacity Factor. Signal processing. End of presentation. Vikas Mishra. Niranjan Sharma. Shariq Ansari. Sherin Kurian. Manish Kumar. Ashok Taneja. Hunk Cool. Hadi Agustana. Omer Enayah Ali. Eric Greene. More From Vikas Mishra.

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Cdma basics ppt link CDMA combines three different spreading sequences to create unique, robust channels. Frequency Division Duplexing. If the set of reflected signals have one dominant component. Login New User. Why do I need to sign in? This type of variation is called Rayleigh fading This can cause large blocks of information to be lost.
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Cdma basics ppt link The mobile station, in tethered mode, can also act as a modem for a computer. Already Have an Account? Anna Hridin. Continue with Google or Continue with Facebook. Share via Mail. It allows some simple conclusions to be drawn.

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