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4G LTE includes:
What is LTELTE OFDMA / SCFDMAMIMOLTE DuplexLTE frame & subframeLTE data channelsLTE frequency bandsLTE EARFCNUE categories / classesLTE-M (Machine to Machine)LTE-LAA / LTE-UVoLTESRVCC
LTE Advanced topics:LTE Advanced introductionCarrier aggregationCoordinated multipointLTE relayDevice to device, D2D

Like previous cellular systems, and virtually all data communications systems, LTE data is carried in frames and subframes.

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Using frames and subframes enables the data to be synchronised enabling the radio network to be able to handle the data correctly.

How to know if someone is gambling illegal. The frames and subframes used different between the FDD and TDD versions of LTE because there are different requirements for segregating data on the two schemes.

The two types of LTE frame structure are:

• Type 1: used for the LTE FDD mode systems.
• Type 2: used for the LTE TDD systems.

Type 1 LTE Frame Structure

The basic type 1 LTE frame has an overall length of 10 ms. This is then divided into a total of 20 individual slots. LTE Subframes then consist of two slots - in other words there are ten LTE subframes within a frame.

Type 2 LTE Frame Structure

The frame structure for the type 2 frames used on LTE TDD is somewhat different. The 10 ms frame comprises two half frames, each 5 ms long. The LTE half-frames are further split into five subframes, each 1ms long.

The subframes may be divided into standard subframes of special subframes. The special subframes consist of three fields;

• DwPTS - Downlink Pilot Time Slot
• GP - Guard Period
• UpPTS - Uplink Pilot Time Stot.

These three fields are also used within TD-SCDMA and they have been carried over into LTE TDD (TD-LTE) and thereby help the upgrade path. The fields are individually configurable in terms of length, although the total length of all three together must be 1ms.

LTE TDD / TD-LTE subframe allocations

One of the advantages of using LTE TDD is that it is possible to dynamically change the up and downlink balance and characteristics to meet the load conditions. In order that this can be achieved in an ordered fashion, a number of standard configurations have been set within the LTE standards.

A total of seven up / downlink configurations have been set, and these use either 5 ms or 10 ms switch periodicities. In the case of the 5ms switch point periodicity, a special subframe exists in both half frames. In the case of the 10 ms periodicity, the special subframe exists in the first half frame only. It can be seen from the table below that the subframes 0 and 5 as well as DwPTS are always reserved for the downlink. It can also be seen that UpPTS and the subframe immediately following the special subframe are always reserved for the uplink transmission.

Where:
D is a subframe for downlink transmission
S is a 'special' subframe used for a guard time
U is a subframe for uplink transmission

The frame and subframe structure used within LTE provides the data synchronisation and organisation required to enable it to be transferred in a logical and ordered fashion.

Wireless & Wired Connectivity Topics:
Mobile Communications basics2G GSM3G UMTS4G LTE5GWiFiIEEE 802.15.4DECT cordless phonesNFC- Near Field CommunicationNetworking fundamentalsWhat is the CloudEthernetSerial dataUSBSigFoxLoRaVoIPSDNNFVSD-WAN
Return to Wireless & Wired Connectivity

LTE Physical Layer 2 radio frames are supported:

1. Type 1: FDD : Frequency Division Duplex
2. Type 2: TDD : Time Division Duplex

For multiple access, LTE uses:

For down link: OFDMA: Orthogonal Frequency Division Multiple Access
For up link: SC-FDMA: Single Carrier Frequency Division Multiple Access

1. Type 1: FDD : Frequency Division Duplex

1. It is valid for both half duplex, and full duplex FDD modes
2. Type 1 radio frame has a duration 10 ms and consists of equally sized 20 slots each of 0.5 ms.
3. A subframe comprises two slots, thus one radio frame has 10 sub‐frames.

There are six time units: frame, half-frame, subframe, slot, symbol, and the basic time unit (Ts):

Time Unit Value
Frame 10 ms
Half-frame 5 ms
Subframe 1 ms
Slot 0.5 ms
Symbol (0.5 ms) / 7 for normal CP, (0.5 ms) / 6 for extended CP

Ts 1/(15000 * 2048) sec » 32.6 ns

A resource block (RB) is the smallest unit of resources that can be allocated to a user. It is 180Khz. That is 12 carriers in the frequency domain and 0.5 ms (or 7 CP) in time domain.

So minimum resource allocation to a user in LTE is 180Khz or 1 slot(0.5ms).

TTI is 1ms.

Below is the pictorial representation of FDD

Here the down link and uplink will be done in 2 different frequencies.

In full-duplex FDD, uplink and downlink frames are separated by frequency and are transmitted continuously and synchronously.

In half-duplex FDD, UE cannot receive while transmitting.

LTE Bandwidths

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LTE standard bandwidths are 1.4, 3, 5, 10, 15, and 20 MHz.

Type 1 Frame Structure

2. Type 2: TDD : Time Division Duplex

1. Half of the subframes are available for downlink, and the other half are available for uplink transmission.
2. In each 10 ms interval, where downlink and uplink transmission are separated in the frequency domain.
3. The uplink and downlink subframes are transmitted on the same frequency and are multiplexed in the time domain.
4. There are seven possible configurations given in the standard.
5. Depending upon the traffic, carrier/operator can choose any of the configurations

Special subframes

Special subframes are used for switching from downlink to uplink and contain three sections: DwPTS, GP, and UpPTS.

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DwPTS is Downlink Pilot Time Slot.
UpPTS is Uplink Pilot Time Slot.
GP is guard period between DwPTS and UpPTS.

Note:

1. Subframes 0 and 5 and DwPTS in TDD frames are always allocated to downlink transmissions.
2. Subframe 1 is always configured to be a special subframe.
3. Subframe 6 can also be configured to be a special subframe.

Below is the pictorial representation of TDD

Here the down link and uplink will be done in 2 different time slots.

UPLINK / DOWNLINK SUBFRAME CONFIGURATIONS FOR LTE TDD (TD-LTE)

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OFDMA:

Number of OFDM symbols in each slot depends on type of Cyclic Prefix(CP) used.

– For Normal CP – 7 OFDM symbols per slot

One of the advantages of using LTE TDD is that it is possible to dynamically change the up and downlink balance and characteristics to meet the load conditions. In order that this can be achieved in an ordered fashion, a number of standard configurations have been set within the LTE standards.

A total of seven up / downlink configurations have been set, and these use either 5 ms or 10 ms switch periodicities. In the case of the 5ms switch point periodicity, a special subframe exists in both half frames. In the case of the 10 ms periodicity, the special subframe exists in the first half frame only. It can be seen from the table below that the subframes 0 and 5 as well as DwPTS are always reserved for the downlink. It can also be seen that UpPTS and the subframe immediately following the special subframe are always reserved for the uplink transmission.

Where:
D is a subframe for downlink transmission
S is a 'special' subframe used for a guard time
U is a subframe for uplink transmission

The frame and subframe structure used within LTE provides the data synchronisation and organisation required to enable it to be transferred in a logical and ordered fashion.

Wireless & Wired Connectivity Topics:
Mobile Communications basics2G GSM3G UMTS4G LTE5GWiFiIEEE 802.15.4DECT cordless phonesNFC- Near Field CommunicationNetworking fundamentalsWhat is the CloudEthernetSerial dataUSBSigFoxLoRaVoIPSDNNFVSD-WAN
Return to Wireless & Wired Connectivity

LTE Physical Layer 2 radio frames are supported:

1. Type 1: FDD : Frequency Division Duplex
2. Type 2: TDD : Time Division Duplex

For multiple access, LTE uses:

For down link: OFDMA: Orthogonal Frequency Division Multiple Access
For up link: SC-FDMA: Single Carrier Frequency Division Multiple Access

1. Type 1: FDD : Frequency Division Duplex

1. It is valid for both half duplex, and full duplex FDD modes
2. Type 1 radio frame has a duration 10 ms and consists of equally sized 20 slots each of 0.5 ms.
3. A subframe comprises two slots, thus one radio frame has 10 sub‐frames.

There are six time units: frame, half-frame, subframe, slot, symbol, and the basic time unit (Ts):

Time Unit Value
Frame 10 ms
Half-frame 5 ms
Subframe 1 ms
Slot 0.5 ms
Symbol (0.5 ms) / 7 for normal CP, (0.5 ms) / 6 for extended CP

Ts 1/(15000 * 2048) sec » 32.6 ns

A resource block (RB) is the smallest unit of resources that can be allocated to a user. It is 180Khz. That is 12 carriers in the frequency domain and 0.5 ms (or 7 CP) in time domain.

So minimum resource allocation to a user in LTE is 180Khz or 1 slot(0.5ms).

TTI is 1ms.

Below is the pictorial representation of FDD

Here the down link and uplink will be done in 2 different frequencies.

In full-duplex FDD, uplink and downlink frames are separated by frequency and are transmitted continuously and synchronously.

In half-duplex FDD, UE cannot receive while transmitting.

LTE Bandwidths

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LTE standard bandwidths are 1.4, 3, 5, 10, 15, and 20 MHz.

Type 1 Frame Structure

2. Type 2: TDD : Time Division Duplex

1. Half of the subframes are available for downlink, and the other half are available for uplink transmission.
2. In each 10 ms interval, where downlink and uplink transmission are separated in the frequency domain.
3. The uplink and downlink subframes are transmitted on the same frequency and are multiplexed in the time domain.
4. There are seven possible configurations given in the standard.
5. Depending upon the traffic, carrier/operator can choose any of the configurations

Special subframes

Special subframes are used for switching from downlink to uplink and contain three sections: DwPTS, GP, and UpPTS.

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DwPTS is Downlink Pilot Time Slot.
UpPTS is Uplink Pilot Time Slot.
GP is guard period between DwPTS and UpPTS.

Note:

1. Subframes 0 and 5 and DwPTS in TDD frames are always allocated to downlink transmissions.
2. Subframe 1 is always configured to be a special subframe.
3. Subframe 6 can also be configured to be a special subframe.

Below is the pictorial representation of TDD

Here the down link and uplink will be done in 2 different time slots.

UPLINK / DOWNLINK SUBFRAME CONFIGURATIONS FOR LTE TDD (TD-LTE)

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OFDMA:

Number of OFDM symbols in each slot depends on type of Cyclic Prefix(CP) used.

– For Normal CP – 7 OFDM symbols per slot

– For Extended CP – 6 OFDM symbols per slot

what is Cyclic Prefix? (CP)

The cyclic prefix is a guard interval to protect the OFDM signals from intersymbol interference.

It is the copy of last part of OFDM that is perpended to transmitted symbol and removed at the receiver before demodulation.

To make OFDM insensitive to time dispersion, CP is inserted.

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