Showing posts with label Channel access method. Show all posts
Showing posts with label Channel access method. Show all posts

CDMA 2000 forward channel

CDMA 2000 user is assigned a forward channel that consists of the following combination :
  1. Forward fundamental channel  (F-FCH)
  2. 0-7: Forward supplemental code channel (F-SCHs) for both RC1 and RC2
  3. 0-2: Forward supplemental code channel (F-SCHs) for both RC3 and RC
The different forward/downlink physical channel are : 
  1. Forward pilot channel (F-PICH)
  2. Forward auxiliary pilot channel (F-APICH)
  3. Forward transmit diversity pilot channel (F-TDPICH)
  4. Forward sync channel (F-SYNC)
  5. The forward paging channel (F-PCH)
  6. Forward broadcast channel (F-BCH)
  7. The forward quick paging channel (F-QPCH)
  8. The forward common power control channel (F-CPCCH)
  9. Forward supplemental channel (F-SCH)
  10. Forward common assignment channel (F-CACH)
  11. The forward dedicated control channel (F-DCCH)
  12. The forward data traffic channel 
1. Forward pilot channel (F-PICH)
This channel is used to get multipath fading and channel conditions. This channel is shared by mobile nodes to obtain the above mentions information.

2. Forward auxiliary pilot channel (F-APICH)
Every channel is allocated a unique Walsh code under the code-multiplexed method in a downlink.

3. Forward transmit diversity pilot channel (F-TDPICH)
When increased RF capacity this channel is used. In these channels are intended for synchronization by the mobile with a specific cell.

4. Forward sync channel (F-SYNC)
For providing initial synchronization related data to the mobile station this channel is used. 

These are two types of forwarding sync channel that are used :
  • Shared sync channel
  • Wide-band sync channel
5. The forward paging channel (F-PCH)
The base station uses this channel in order to transmit the mobile station specific message and the overhead message. 

These are two types of forwarding paging channel are used :
  • Shared paging channel
  • Wide-band paging channel
6.  Forward broadcast channel (F-BCH)
It is intended to transmit control information to the respective mobile stations effectively that have not been allocated a traffic channel.

7. The forward quick paging channel (F-QPCH)
This quick paging channel is used by the paging channel for providing control information to the mobile stations.

8. The forward common power control channel (F-CPCCH)
The necessary power control information of uplink common control channel is conveyed by base stations using this channel.

9. Forward supplemental channel (F-SCH)
Up to two F-SCHs can be assigned to a single mobile unit for high-speed data ranging from 9.6 to 153.6 kbps in release 0.

10. Forward common assignment channel (F-CACH)
The quick assignment of a reverse common control channel is done by the base station using this channel.

11. Forward common assignment channel (F-CACH)
 It is used to send high layer message to the mobile units. This channel is used by the base station.

12. The forward dedicated control channel (F-DCCH)
  • It replaces the dim and burst and blank and burst
  • It is used for messaging and control for data calls
  • In addition to these channel forward data, a traffic channel is also used in forwarding channels in the CDMA 2000 standard

The minimum configuration consists of a reverse pilot channel to enable the base station (BS) to perform synchronous detection and reverse fundamental channel for voice.

Application of SDMA

SDMA stands for space division multiple access. It depends on the user position information and provides users access to the communication channel based on their spatial locations. 

 SDMA separated into the geographical space, where users are located, into smaller space. It is used for a mobile communication system which reuses the same set of cell phone frequencies in a given service area.

 So compare to the other multiple access techniques like TDMA full form, CDMA full form,  FDMA full form, SDMA full form is compatible So it can be more used in a wireless communication system. This article gives the application about SDMA to know more details about SDMA.
  • Satellite communication
  • Optical communication
  • Wireless communication
  • Mobile communication
  • SDMA can be also used in conjunction with the WDM system  and TDM
  • SDMA uses a spot beam antenna

What is SDMA

For to know about SDMA you should first of all check it out the full form of SDMA.


SDMA stands for space division multiple access. It depends on the user position information and provides users access to the communication channel based on their spatial locations. 

SDMA separated into the geographical space, where users are located, into smaller space. It is used for a mobile communication system which reuses the same set of cell phone frequencies in a given service area.

 Space division multiple access is techniques which are MIMO architecture and it can be used in wireless and satellite communication. This article also gives some feature of SDMA given below. 
  • SDMA is completely free from interference.
  • Controlling the medium access for a wireless network.
  • Careful choice of a zone for each transmitter.
  • In this system control the radiated energy for each user in space.
  • All user can communicate at the same time using the same channel.
  • The directional spot beam antennas are used and hence the (BS) base station in SDMA can track a moving user.
  • A single satellite can communicate with more satellites receivers of the same frequency. frequency.
  • SDMA never used isolation.
  • Satellite communication
  • Optical communication
  • Wireless communication
  • Mobile communication
  • SDMA can be also used in conjunction with the WDM  system  and TDM
  • SDMA uses a spot beam antenna

Explore more information:

Advantages and disadvantages of SDMA

The term SDMA full form is Spatial Division Multiple Access OR Space Division Multiple Access methods. It is one type of channel access method. It is used for mobile communication system which reuses the same set of cell phone frequencies in a given service area. This article gives information about some advantages and disadvantages of SDMA to know more details about SDMA.

Advantages of SDMA :
  • SDMA is a purely optical path
  • SDMA is frequency reuse
  • Mobile station battery consumption is low
  • Increased spectral efficiency
  • SDMA is transparent to the system if it is purely optical
  • Use any bandwidth or data rate achievable in fiber
  • SDMA is usually combined with other multiplexing techniques to better utilize the individual physical channel
Disadvantages of SDMA :
  • Some of  the disadvantages of  SDMA is the fact that the number of switches
  • SDMA is very expensive and complected to construct and design
  • There are also high insertion losses since each input must have the capability to be split to any output.
  • The reverse link may be a problem like an interference problem
Explore more information:
  1. Advantages and disadvantages of FDMA
  2. Advantages and disadvantages of CDMA
  3. Advantages and disadvantages of TDMA

Feature of SDMA

Before we learn about a feature of SDMA first let we check it out what is full form of SDMA. Space division multiple access is techniques which are MIMO architecture and it can be used in wireless and satellite communication. This article gives some feature of SDMA given below. 
  • SDMA is completely free from interference.
  • Controlling the medium access for the wireless network.
  • Careful choice of a zone for each transmitter.
  • In this system, it controls the radiated energy for each user in space.
  • All user can communicate at the same time using the same channel.
  • The directional spot beam antennas are used and hence the base station (BS) in SDMA can track a moving user.
  • A single satellite can communicate with more satellites receivers of the same frequency. frequency.
  • SDMA never used isolation.

SDMA definition

SDMA full form stands for spatial division multiple access or space division multiple access methods. It is one types of multiple access methods. It is used for a mobile communication system which reuses the same set of cell phone frequencies in a given service area. A base station, SDMA continually adapts to the radio environment. Some feature of the SDMA method given below :
  • SDMA become less practical.
  • SDMA is suited for short distance transmission.
  • In SDMA single fiber replaced with multiple fibers used in parallel.

OFDM block diagram

In OFDM full form is basically two parts as transmitter and receiver.

In this system at the transmitter side error correction coding, interleaving process is done over the data stream. The data stream that is sent is in the form of a symbol that has undergone quadrature amplitude modulation. Then the symbol stream is assigned to one of the subcarriers with an assigned symbol. Every subscriber will operate at a particular frequency. 

In the frequency domain, the symbol frame is formed with a group of symbols from all subcarriers.

OFDM is a multi-carrier transmission technology. OFDM is used to obtain a higher data rate in the multipath fading environment of mobile communication.

The every symbol frame is transformed into a time frame with the help of N point "inverse Fourier transformation.

OFDM block diagram

 The digital data stream is generated by this time of frames.
Finally, the signal is amplified and transmitted to the antenna side. Convolution coding method with CRC error detection is used to provide high data security for the system.
OFDM is sensitive to phase and frequency noise. To minimize its correct pulse shape needs to be selected.

 OFDM is possible to use maximum likelihood decoding with reasonable complexity, so it is one types of OFDM advantages.
In OFDM receiver side the symbol frame received is detected. so it has to adjust automatic gain control to the desired level. A robust algorithm is to be used to withstand phase noise and also a frequency offset of the receiving unit that will interface with the synchronization process.

OFDM definition

Before we learn about OFDM, first let we check it out what is full form of OFDM. OFDM is a modulation format used for the latest wireless communications technology. 

OFDM is a multi-carrier transmission technology. OFDM is used to obtain a higher data rate in the multipath fading environment of mobile communication.

In mobile communication, the selection of digital modulation is dependent on three parameters. They are listed below :
  • Narrower bandwidth 
  • Efficient power utilization
  • Elimination of intermodulation products

CDMA definition

Code division multiple access (CDMA) is one type of channel access method, In this method user, may transmit at the same time using same frequency band but with different codes so that we can easily decode to identify a particular user. 


CDMA definition
CDMA

TDMA definition

Time division multiple access (TDMA) is one type of multiple access method. In each user allowed to transmit only in a specified time slot with a common frequency band. It allows several users can transmit to share the same frequency band at a different time, so each using its own time slot.

TDMA

FDMA definition

Frequency division multiple access (full meaning of FDMA) is a frequency band, it is one types of channel access method and it can be divided small frequency channel and also have different channel are allocated to different users. Multiple users can transmit at the same time but on different frequency channel as shown in the figure below :

FDMA



How FDMA work

FDMA is a channel access method can be implemented at the MAC full form is a media access control layer of the data link layer in the OSI full form open systems interconnection reference model for networking protocol stacks. 

 First, let we check it out the full meaning of FDMA. It is a frequency band, it is one types of channel access method and it can be divided small frequency channel and also have different channel are allocated to different users. The user can be assigned a specific frequency band in the electromagnetic spectrum and at that time a call that user is the only who has the right to access the specific band. 

 In the AMPS cellular phone system, the frequency band is allocated from the electromagnetic spectrum as follows :

Two different frequency bands are used to allow full duplex communication between the base and mobile stations. 

Transmission by mobile station used AMPS cellular phone: 824 MHz to 849 MHz
Transmission by base station used AMPS cellular phone: 869 MHz to 894 MHz

 Both of these band are then divided into discrete channels that are 30 KHz wide in bandwidth.

FDMA applications

Frequency division multiple access is a frequency band, it is one types of channel access method and it can be divided small frequency channel and also have different channel are allocated to different users. Now here check it out the application of FDMA  to know more details about FDMA. 

 Applications :
  • Telephone system
  • Radio system 
  • Cable TV
  • Walkie talkies
  • Mobile network for a closed user group. e.g. Wi-Fi
  • Total access communication systems (TACS)
  • 2G mobile communication
  • GSM uses FDMA in combination with TDMA
  • UMTS in combination with other multiplexing techniques 


CDMA 2000 reverse channel

The reverse link for CDMA 2000 has properties similar to the forward link of a signal. 
And also have CDMA 2000 user is assigned a forward channel that consists of the following combination :

  1. Forward fundamental channel  (F-FCH)
  2. 0-7: Forward supplemental code channel (F-SCHs) for both RC1 and RC2
  3. 0-2: Forward supplemental code channel (F-SCHs) for both RC3 and RC
The minimum configuration consists of a reverse pilot channel to enable the base station (BS) to perform synchronous detection and reverse fundamental channel for voice.
The different reverse channel is:
  1. Reverse supplemental channel (R-SCH)
  2. Reverse pilot channel (R-PICH)
  3. The reverse dedicated control channel (R-DCCH)
  4. Reverse enhanced access channel (R-EACH)
  5. The reverse common control channel (R-CCCH)
  6. Reverse fundamental channel (R-FCH)
  7. Reverse supplemental code channel (R-SCCH)
1. Reverse supplemental channel (R-SCH)
When the data rate is greater than 9.6 kbps, an R-SCH is needed. R-SCH channel is assigned for power control. A total of one or two R-SCH can be assigned per mobile unit.

2. Reverse pilot channel (R-PICH)
It provides pilot and power control information. It enables the mobile unit to transmit a lower power level and allow to inform the base station of the forward power levels being received, enabling the base station to reduce power.

3. Reverse enhanced access channel (R-EACH)
R-EACH is used to initiate communication with the base station. It is used by a mobile station, This channel also reduces the access channel power.

4. The reverse common control channel (R-CCCH)
This channel is used by the mobile unit to send their data information after they have granted access.

5. The reverse dedicated control channel (R-DCCH)
This channel replaces the dim and burst and the blank and burst. It is used for messaging and control for data calls.

6. Reverse fundamental channel (R-FCH)
This channel is used for voice and data payload. R-FCH is allowed shorter frame, this shorter frame can be used lower latency.

7. Reverse supplemental code channel (R-SCCH)
This channel is the same as F-SCCH and same it can be used with radio configuration. 

Application of CDMA 2000

  • Wireless internet
  • Location-based services
  • Wireless email 
  • Steaming video games
  • Telemetry
  • Wireless telecommunication
  • Longer standby battery life
  • Enterprise solutions
  • Wireless commerce
  • Web browsing
  • Multimedia services
  • Future demand for data service

Advantages of CDMA 2000

CDMA 2000 has unique features, benefits, and performance so it provides better advantages like high-voice capacity and high-speed packet data. Now we can check some more advantages one by one below.
  • Industry-leading performance.
  • Device selection.
  • Flexible migration path.
  • Flexible network architecture.
  • New common channel structure and operation.
  • Ubiquitous idle time operation.
  • Global roaming and multi-mode, multiband devices.
  • Flexible spectral allocation and efficient use of spectrum.
  • New MAC states for efficient.
  • Support for advanced mobile service.
  • Seamless Evolution path.
  • Quick paging channel operation.
  • Reverse link gated transmission.
  • Superior voice quality.
  • High-speed broadband data connectivity. 
  • Improve securities and privacy.
  • Multi-mode, multiband global roaming features. 

CDMA 2000

What is CDMA 2000? 

Before we learn about CDMA 2000 first let us learn about what is full form of CDMA. CDMA 2000 is code division multiple access version of the IMT-2000 standard developed by the International Telecommunication Union. 

 CDMA 2000 also known as the IMT-CDMA multi-carrier or the 1xRTT.

 Overview :
  • CDMA 2000 is a high data rate upgrade path for current users of 2G and 2.5G CDMA standard. It is a unique radio and network access system that is part of the international telecommunication called 2000. It is called a 3G standard.
  • CDMA 2000 allows the basically same spectrum, bandwidth, RF equipment, and air interface framework to be used at each station.
  • The first CDMA air interface CDMA 2000  with 1 × RTT (Radio transmission technology language) indicates that a single 1.25 MHz radio channel used.
  • CDMA 1x support data rate up to 307 kbps for a single user in packet mode. It can provide a throughput rate of up to 144 kbps depending on the propagation conditions.
  • CDMA 1xEV as an also part of IMT 2000. Its provide CDMA carrier with the option of installing radio channel with data only or data and voice only.
  • CDMA 2000 3xRTT standard is used for three adjacent 1.25 MHz radio channel. It can be used together to provide instantaneous packet data.
  • This article gives information about Feature, advantages, application of CDMA 2000 to gives more information about CDMA 2000.
A feature of CDMA 2000 :  
  • Support high-speed data service.
  • It is a global standard.
  • It has the flexibility for evolution.
  • It has improved spectrum efficiency.
  • Support advance mobile service.
  • Leading performance.
  • Industry-leading performance
  • Device selection
  • Flexible migration path
  • Flexible network architecture
  • New common channel structure and operation
  • Ubiquitous idle time operation
  • Global roaming and multi-mode, multiband devices
  • Flexible spectral allocation and efficient use of spectrum
Let us check is out the application of CDMA 2000 given below :

 Application of CDMA 2000 :
  • It is developed for both mobile radio and cordless application
  • Wireless internet
  • Location-based services
  • Wireless email
  • Telemetry
  • Wireless telecommunication
  • Longer standby battery life
  • Wireless commerce

TDMA applications

TDMA is one type of multiple access method. First, let we check it out the full form of TDMA full form. In each user allowed to transmit only in a specified time slot with a common frequency band. It allows several users can transmit to share the same frequency band at a different time, so each using its own time slot. 
  • TDMA used in digital cellular telecommunication.
  • Satellite system.
  • It is used GSM, IS-136, iDEN.
  • Dynamic TDMA used for packet mode communication.
  • Also, GSM uses TDMA in combination with FDMA. its a one types of advantages of TDMA
  • PON network also uses for upstream traffic from premises to the operator.
  • TDMA also used as telephone communication.

CDMA applications

Because to inherent advantages of CDMA over TDMA full form and FDMA full forms such as user capacity, soft handoffs and securities applications of that increase and it used in a variety of applications. Let we check the applications one by one below.

Applications :
  • CDMA is used for a cellular system.
  • One of the most important for CDMA is on GPS.
  • It can be used for subscriber access control.
  • CDMA is used for personal communication service.
  • It can be used for over the air activation.
  • It can be used for short message service.
  • The UMTS 3G mobile phone standard, which uses CDMA.
  • It is used radar and navigation system.
  • Wireless laptop modem.
  • Soft handoff and security.
  • It is used military and some commercial application.
  • CDMA used for anti-collision and increased read efficiency of multiple RFID.
  • Bluetooth uses fast FH-CDMA.
  • Improvement of speech coders in the wireless communication system.
  • Another standard CDMA 2000, is used by several mobile, phone companies, as well as the global-star satellite phone network.

Features of OFDM



  • A symbol is modulated on to orthogonal sub-carrier.
  • Modulation is done by using IFFT.
  • High spectral efficiency.
  • Demodulation is done by using FFT. ( Demodulation of received signal ) 
  • Low efficiency to time synchronization techniques.
  • Better resultant quality of fading.
  • Very sensitive to time-frequency synchronization.
  • Simplified channel equalization.
  • Immunity to intersymbol interference. 
  • No inter-carrier guard band.
  • Orthogonal carrier and control overlapping band.
  • Improved quality of narrowband interference.
  • Robust against intersymbol interference.
  • Fading caused by multi-path propagation.
  • Decoding and de-interleaving. 
  • Orthogonality is maintained during channel transmission.

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