Channel access methods

What is channel access?
The ability of the system to carry many signals at the same time is called channel access. Read more
There are three main types of channel access FDMA TDMA and CDMA. Read more

FDMA :
FDMA is the wireless system, where individual users are allocated individual channels. Read more 

Definition of FDMA :
Frequency division multiple access(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. Read more 

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

The number of channels that can be simultaneously supported in an FDMA system is given by N =  Bt - 2 Bguard   Bc  Read more

Features of FDMA :
1. The complexity of FDMA systems is less. 2. The FDMA channel uses one phone circuit at any instant of time. Read more 

Basically, there are two types of  FDMA multiple access methods. 1. FAMA 2. DAMA Read more

Application of FDMA :
FDMA uses a variety of application such as 1.Telephone system, 2. Radio system Read more

Advantages and disadvantages of FDMA :
Advantages: 1. Synchronization is not necessary. 2. If the channel is not used, it sits idle.
Disadvantages: 1. Cell site cost is high. 2. The bandwidth of the FDMA channel is narrow. 
Read more 

TDMA :

TDMA is a technology used in cellular or telecommunication. It divides each cellular channel into three-time slots in order to increase the amount of data that can be carried. Read more 

Definition of TDMA :
Time division multiple access (TDMA) is one type of multiple access method. In each user allowed to transmit only in the specified time slot with a common frequency band. Read more

A number of channels in the TDMA system :
The number of channel slot that can be provided in a TDMA system is found by multiplying the number of TDMA slots per channel by a number of channels available. Read more

Features of TDMA :
1. Data transmission is done in bursts so low battery consumption as the transmitter of the subscriber can be turn off when it is not in use. 2. Guard time needs to be minimized.
Read more

The efficiency of the TDMA system :
The efficiency of a TDMA system is a measure of the percentage of the data that is transmitted. Read more 

Application of TDMA :
TDMA uses a variety of application such as 1. TDMA used in digital cellular telecommunication, 2. Satellite system Read more

Advantages and disadvantages of TDMA :
Advantages: 1. TDMA can easily adapt to the transmission of data as well as voice communication. 2. Data it rates up to carry 64kbps to 120 Mbps.
Disadvantages: 1. High synchronization overhead. 2. Using TDMA system frequency/slot allocation is to be complex. Read more

CDMA :

CDMA is a channel access method used in various radio communication technology. It refers to any protocols used in 2G and 3G communications. Read more 

Definition of CDMA :
Code division multiple access (CDMA) is one type of channel access method, In this method user, may transmit at the same time using the same frequency band. Read more

1. The CDMA system users share the same frequency. 2. TDD or FDD can be used. Read more 

Application of CDMA :
1. CDMA is used for a cellular system.
2. One of the most important for CDMA is on GPS.

Advantages and disadvantages of CDMA :
Advantages: 1. Greatest spectrum efficiency 2. Low power requirement
Disadvantages: 1. Time synchronization is needed 2. CDMA is relatively low. The network is not as mature as the GSM. Read more

SDMA :

What is SDMA?
SDMA is depended on the user position information and provide users access to the communication channel based on their spatial locations. Read more

Definition of SDMA :

SDMA stands for spatial division multiple access or space division multiple access methods. It is one types of multiple access methods. Read more

A feature of SDMA :
1. SDMA is completely free from interference. 2. Controlling the medium access for the wireless network. Read more 

Application of SDMA :
1. Satellite communication, 2. Optical communication Read more

Advantages and disadvantages of SDMA :
Advantages: 1. SDMA is a purely optical path 2. SDMA is frequency reuse.
Disadvantages: 1. Some of the disadvantages of  SDMA is the fact that the number of switch 2. SDMA is very expensive and complected to construct and design. Read more

OFDM : 

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

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

OFDM Block diagram :
In OFDM is basically two parts: Transmitter and Receiver.
In the frequency domain, the symbol frame is formed with a group of symbols from all subcarriers. Read more

Features of OFDM :
1. High spectral efficiency. 2. Better resultant quality of fading. Read more 

Applications of OFDM
1. HDTV 2. Digital audio broadcasting 3. Wireless LAN networks Read more 

Advantages and disadvantages of  OFDM :
Advantages: 1. High spectral efficiency. 2. Resistance against multi-path interference.
Disadvantages: 1. Require highly linear amplifier.  2. Sensitive to doppler effect. Read more

CDMA 2000 :

What is CDMA 2000?

CDMA 2000 is code division multiple access version of the IMT-2000 standard developed by the International Telecommunication Union. Read more 

CDMA 2000 forward channel :

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. Read more 

CDMA 2000 reverse channel :

Following combination: 1. Reverse supplemental channel (R-SCH), 2. Reverse pilot channel (R-PICH), 3. The reverse dedicated control channel (R-DCCH) Read more 

Application of CDMA 2000

1. Wireless internet, 2. Location-based services Read more 

Advantages: 1. Device selection, 2. Flexible migration path. Read more