Thủ Thuật về Which of the following technique is suitable for digital transmission options CDMA FDMA TDMA all of the above? Mới Nhất
Họ tên bố(mẹ) đang tìm kiếm từ khóa Which of the following technique is suitable for digital transmission options CDMA FDMA TDMA all of the above? được Cập Nhật vào lúc : 2022-10-21 19:04:07 . Với phương châm chia sẻ Thủ Thuật về trong nội dung bài viết một cách Chi Tiết 2022. Nếu sau khi tham khảo Post vẫn ko hiểu thì hoàn toàn có thể lại phản hồi ở cuối bài để Mình lý giải và hướng dẫn lại nha.The different access methods which permit many satellite users to operate in parallel through a single transponder without interfering with each other are1. Frequency Division Multiple Access (FDMA)2. Time Division Multiple Access (TDMA)3. Code Division Multiple Access (CDMA)Which of the above are correct?
1 and 2 only 1 and 3 only 2 and 3 only 1, 2 and 3 Nội dung chính- The different access methods which permit many satellite users to operate in parallel through a single transponder without interfering with each other are1. Frequency Division Multiple Access (FDMA)2. Time Division Multiple Access (TDMA)3. Code Division Multiple Access (CDMA)Which of the above are correct?Answer (Detailed Solution Below)Multiple Access TechniquesNarrowband SystemsWideband SystemsFrequency Division Multiple Access (FDMA)Time Division Multiple Access (TDMA)Code Division Multiple Access (CDMA)Space Division Multiple Access (SDMA)Spread Spectrum Multiple AccessFrequency Hopped Spread Spectrum (FHSS)Direct Sequence Spread Spectrum (DSSS)Which technique is suitable for digital transmission?Which is better CDMA or TDMA or FDMA?What is TDMA in digital communication?What is FDMA in digital communication?
Answer (Detailed Solution Below)
Option 2 : 1 and 3 only
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CT 1: Engineering Mathematics
10 Questions 5 Marks 15 Mins
In TDMA, different users access the transponder in different time slots, not in parallel.
Hence, Option 2 is correct.
Time-division multiple access (TDMA):
- This 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.The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity.
Frequency division multiple access (FDMA):
- FDMA is a channel access method used in some multiple-access protocols.FDMA allows multiple users to send data
through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user.Users can send data through a sub-channel by modulating it on a carrier wave the sub-channels frequency.
Code division multiple access (CDMA):
- CDMA stands for Code Division Multiple Access.CDMA (Code Division
Multiple Access) uses a digital modulation technique called Direct Sequence spread spectrum which spreads voice data over a very wide spectrum using a user or cell-specific pseudo-random codes.It is a wireless technology used in the transmission of signals from places with high security and Noise reduction.The principle of the spread spectrum is used to work with CDMA.CDMA is not frequency specific to each user, instead, every channel uses
the full available spectrum.Each user in a CDMA system uses a different code to modulate their signal.
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Multiple access schemes are used to allow many mobile users to share simultaneously a finite amount of radio spectrum.
Multiple Access Techniques
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.e., to handle as many calls as possible in a given bandwidth with a sufficient level of quality of service.
There are several different ways to allow access to the channel. These includes mainly the following −
- Frequency division multiple-access (FDMA)Time division multiple-access (TDMA)Code division
multiple-access (CDMA)Space division multiple access (SDMA)
Depending on how the available bandwidth is allocated to the users, these techniques can be classified as narrowband and wideband systems.
Narrowband Systems
Systems operating with channels substantially narrower than the coherence bandwidth are called as Narrow band systems. Narrow band TDMA allows users to use the same channel but allocates a unique time slot to each user on the channel, thus separating a small number of users in time on a single channel.
Wideband Systems
In wideband systems, the transmission bandwidth of a single channel is much larger than the coherence bandwidth of the channel. Thus, multipath fading doesn’t greatly affect the received signal within a wideband channel, and frequency selective fades occur only in a small fraction of the signal bandwidth.
Frequency Division Multiple Access (FDMA)
FDMA is the basic technology for advanced mobile phone services. The features of FDMA are as follows.
- FDMA allots a different sub-band of frequency to each different user to access the network.If FDMA is not in use, the channel is left idle instead of allotting to the other users.FDMA is implemented in Narrowband systems and it is less complex than TDMA.Tight filtering is done here to reduce adjacent channel interference.The base station BS and mobile station MS, transmit and
receive simultaneously and continuously in FDMA.
Time Division Multiple Access (TDMA)
In the cases where continuous transmission is not required, there TDMA is used instead of FDMA. The features of TDMA include the following.
- TDMA shares a single carrier frequency with several users where each users makes use of non-overlapping time slots.Data transmission in TDMA is not continuous, but occurs in bursts. Hence handsoff process is simpler.TDMA uses
different time slots for transmission and reception thus duplexers are not required.TDMA has an advantage that is possible to allocate different numbers of time slots per frame to different users.Bandwidth can be supplied on demand to different users by concatenating or reassigning time slot based on priority.
Code Division Multiple Access (CDMA)
Code division multiple access technique is an example of multiple access where several transmitters use a single channel to send information simultaneously. Its features are as follows.
- In CDMA every user uses the full available spectrum instead of getting allotted by separate frequency.CDMA is much recommended for voice and data communications.While multiple codes occupy the same channel in CDMA, the users having same code can communicate with each other.CDMA offers more air-space capacity than TDMA.The hands-off between base stations is very well handled by
CDMA.
Space Division Multiple Access (SDMA)
Space division multiple access or spatial division multiple access is a technique which is MIMO (multiple-input multiple-output) architecture and used mostly in wireless and satellite communication. It has the following features.
- All users can communicate the same time using the same channel.SDMA is completely không lấy phí from interference.A single satellite can communicate with more satellites receivers of
the same frequency.The directional spot-beam antennas are used and hence the base station in SDMA, can track a moving user.Controls the radiated energy for each user in space.
Spread Spectrum Multiple Access
Spread spectrum multiple access (SSMA) uses signals which have a transmission bandwidth whose magnitude is greater than the minimum required RF bandwidth.
There are two main types of spread spectrum multiple access techniques −
- Frequency
hopped spread spectrum (FHSS)Direct sequence spread spectrum (DSSS)
Frequency Hopped Spread Spectrum (FHSS)
This is a digital multiple access system in which the carrier frequencies of the individual users are varied in a pseudo random fashion within a wideband channel. The digital data is broken into uniform sized bursts which is then transmitted on different carrier frequencies.
Direct Sequence Spread Spectrum (DSSS)
This is the most commonly used technology for CDMA. In DS-SS, the message signal is multiplied by a Pseudo Random Noise Code. Each user is given his own code word which is orthogonal to the codes of other users and in order to detect the user, the receiver must know the code word used by the transmitter.
The combinational sequences called as hybrid are also used as another type of spread spectrum. Time hopping is also another type which is rarely mentioned.
Since many users can share the same spread spectrum bandwidth without interfering with one another, spread spectrum systems become bandwidth efficient in a multiple user environment.
Which technique is suitable for digital transmission?
To convert analog wave into digital data, we use Pulse Code Modulation (PCM). PCM is one of the most commonly used method to convert analog data into digital form.Which is better CDMA or TDMA or FDMA?
FDMA supports a low rate of data. TDMA supports a medium rate of data. CDMA supports a high rate of data.What is TDMA in digital communication?
Time Division Multiple Access (TDMA) is a digital modulation technique used in digital cellular telephone and mobile radio communication. TDMA is one of two ways to divide the limited spectrum available over a radio frequency (RF) cellular channel.What is FDMA in digital communication?
FDMA (frequency division multiple access) is the division of the frequency band allocated for wireless cellular telephone communication into 30 channels, each of which can carry a voice conversation or, with digital service, carry digital data. Tải thêm tài liệu liên quan đến nội dung bài viết Which of the following technique is suitable for digital transmission options CDMA FDMA TDMA all of the above?