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.

LTE Architecture & Features

The high level network architecture of LTE comprises of 3 levels

• User Equipment(UE)

• UMTS Terrestrial Radio Access Network(UTRAN)

• Core

The Figure below shows the model of LTE













User Equipment(UE)-Its a device directly used by end user for communication.It handles functions like Call control,Session management,Mobility Management.It consists of the mobile device and data to be sent.

UMTS Terrestrial Radio Access Network(UTRAN)- We will be discussing about this in coming blogs.

Core-
It consists of SGSN,MME,HSS,PWG,SWG.

• SGSN-It is a Serving GPRS Supporting Node.It is responsile for delivery of data packets from and to the mobile station within its area.

• MME-It is Mobile Management Entity.IT is involved  in activation and deactivation.MME provide control plane function for mobility between LTE and 2G/3G access.

• HSS-Its Human Subscriber Server.It contains user related and subscription related information.

• SGW-Its Serving Gateway.SGW routes server data packets.

• PGW-Its PDN gateway.PGW provides charging support,policy enforcement,packet screening.

Features

• It can offer speed upto 1Gbps over wireless signal for fixed mobile broadband.

• MIMO Multiple IN Multiple Out is an antenna by which by which LTE will boost its capacity.

• It operates both in FDD and TDD modes.

• Increased spectral efficiency.

• Bandwidth upto 20 MHz.

• Reduced cost for operators.

Long Term Evolution

Long Term Evolution(LTE) is also referred  as 3GPP Long Term Evoluion. 3rd Generation Partnership Project(3GPP) operates under European Telecommunication Standard Institue(ETSI). LTE is smooth and efficient transition towards more advanced technology to increase speed of wireless network data.3GPP engineers named the technology "Long Term Evolution" because it represents the next step(4G) in progression from GSM,a 2G standard, to UMTS,to 3G based  upon GSM. LTE provides significantly increased peak data rates with potential for 100Mbps downstream and 30 Mbps upstream,reduced latency, scalable bandwidth capacity with existing GSM and UMTS technology. Future developments could yield upto 300 Mbps. Research is being carried on.

The figure below shows the development over time

The world's first first publicly available LTE service was launched by Telia Sonera in Oslo and Stockholm on 14th December,2009. LTE was first proposed by NTT Docomo of Japan in 2004.The LTE standards covers range of many different frequencies and bands. 

• In North America,700,800,1900 and 2100 MHz are used (4,12,13,17,25 bands)

• 2500 in South America

• 800,9001800,2600 MHz in Europe(3,7,20 bands)

• 1800 and 2600 MHz in Asia (1,3,5,7,8,11,13,40 bands)

• 1800 MHz in Australia and New Zealand  (3,40)

As a result ,phones from one country may not work in another.Users will need a multiple band capable phone for international roaming.

The upper layers of LTE are based upon TCP/IP,which will likely result in all IP network similar to current state of wired communications. LTE will support mixed data,voice,video and messaging traffic. LTE uses OFDM (Orthogonal Frequency Division Multiplexing) and in later releases,MIMO(Multiple In Multiple Output) antenna technology similar used in WLAN. The higher signal to noise ratio(SNR) at the receiver enabled by MIMO along with OFDM,provides improved coverage especially in dense urban areas.

Operators gain advantage of higher data  rates per cell from 4G LTE,larger customer capacity per cell and more efficient use infrastructure for services that are increasingly data dominated.Operators can upgrade existing infrastructure to mobile operators as the amount of data traffic on their networks grows.

Thus,this blog provides general overview of what is Long Term Evolution and when was it started.In the next blog,we will in more depth what exactly is Long Term Evolution.