Antennas used in LTE

4 types of antennas are used in this system

• SISO

• SIMO

• MISO

• MIMO

1. Single Input Single Output(SISO):-It is the most basic radio access mode set with one transmitter and one receiver.SISO provides no diversity protection against channel fading.There is no diversity and no additional processing required.Its main advantage is its simplicity.

                            

2. Single In Multiple Output(SIMO):-It provides additional receive antenna redundancy compared to SISO.This also knon as receive diversity.SIMO has advantage tahat it is relatively easy to implement although it does have disadvantages in that the processing is required in the receiver.Its use may be quite acceptable in many applications,but where receiver is located in mobile device such as cellphone handset,the levels of processing may be limited in size,cost and battery drain.

There are two types of SIMO used

• Switched diversity SIMO:This form looks for strongest signal and switches to that antenna.

• Maximum Ratio Combining SIMO:This form of SIMO takes both signals and sums them to give the combination.
  

3.  Multiple Input Single Output(MISO):-MISO is also termed as Transmit Diversity.In this same data is transmitted from two transmitter antennas.The receiver is then able to receive optimum signal which it can then use to receive optimum signal which later can be used to extract the required data.Its advantage is that multiple antennas and redundancy coding is moved from receiver to transmitter.In instances such as UE,this can be a significant advantage in terms of space for antennas and reducing the level of processing required inthe receiver for the redundancy coding.This has a positive impact on size,cost and battery life as lower level of processing requires less battery consumptions.

4. Multiple Input Multiple Output(MIMO) :- When there are more than 1 links at both ends of radio link,this is termed as MIMO.This requires processing but provide additional robustness and data throughput capacity.There are many outputs of MIMO that can be used from SISO,through SIMO and MISO to full MIMO system.Balances of performance against cost,size,processing available and resulting battery life need to be made when choosing the correct option.