Channelization Protocols

In this tutorial, we will be covering the Channelization protocols of Multiple access in detail.

Channelization is basically a method that provides the multiple-access and in this, the available bandwidth of the link is shared in time, frequency, or through the code in between the different stations.

Channelization Protocols are broadly classified as follows:

• FDMA(Frequency-Division Multiple Access)

• TDMA(Time-Division Multiple Access)

• CDMA(Code-Division Multiple Access)

Let us discuss the above-given techniques one by one:

1. Frequency-Division Multiple Access

With the help of this technique, the available bandwidth is divided into frequency bands. Each station is allocated a band in order to send its data. Or in other words, we can say that each band is reserved for a specific station and it belongs to the station all the time.

• Each station makes use of the bandpass filter in order to confine the frequencies of the transmitter.

• In order to prevent station interferences, the allocated bands are separated from one another with the help of small guard bands.

• The Frequency-division multiple access mainly specifies a predetermined frequency for the entire period of communication.

• Stream of data can be easily used with the help of FDMA.

Advantages of FDMA

Given below are some of the benefits of using the FDMA technique:

• This technique is efficient when the traffic is uniformly constant.

• In case if the channel is not in use then it sits idle.

• FDMA is simple algorithmically and the complexity is less.

• For FDMA there is no restriction regarding the type of baseband or the type of modulation.

Disadvantages of FDMA

• By using FDMA, the maximum flow rate per channel is fixed and small.

2. Time-Division Multiple Access

Time-Division Multiple access is another method to access the channel for shared medium networks.

• With the help of this technique, the stations share the bandwidth of the channel in time.

• A time slot is allocated to each station during which it can send the data.

• Data is transmitted by each station in the assigned time slot.

• There is a problem in using TDMA and it is due to TDMA the synchronization cannot be achieved between the different stations.

• When using the TDMA technique then each station needs to know the beginning of its slot and the location of its slot.

• If the stations are spread over a large area, then there occur propagation delays; in order to compensate this guard, times are used.

• The data link layer in each station mainly tells its physical layer to use the allocated time slot.

Figure: Time-Division media access.

Some examples of TDMA are as follows;

• personal digital Cellular(PDC)

• Integrated digital enhanced network.

• Universal terrestrial radio access(UTRA)

3. Code-Division Multiple Access

CDMA(code-division multiple access) is another technique used for channelization.

• CDMA technique differs from the FDMA because only one channel occupies the entire bandwidth of the link.

• The CDMA technique differs from the TDMA because all the stations can send data simultaneously as there is no timesharing.

• The CDMA technique simply means communication with different codes.

• In the CDMA technique, there is only one channel that carries all the transmission simultaneously.

• CDMA is mainly based upon the coding theory; where each station is assigned a code, Code is a sequence of numbers called chips.

• The data from the different stations can be transmitted simultaneously but using different code languages.

Advantages of CDMA

Given below are some of the advantages of using the CDMA technique:

• Provide high voice quality.

• CDMA operates at low power levels.

• The capacity of the system is higher than the TDMA and FDMA.

• CDMA is better cost-effective.