OFDMA Downlink

Signal Studio for LTE/LTE-Advanced FDD currently supports only FDD and frame structure type 1.

Frame Structure Type 1

Figure 1 shows frame structure type 1, which can be used in either full-duplex or half-duplex FDD mode. It consists of a 10 ms radio frame divided into 20 slots, numbered 0 to 19, each with a duration of 0.5 ms. One subframe consists of two consecutive slots.

For FDD, 10 subframes are available for downlink transmission and 10 subframes are available for uplink transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain.

In half-duplex FDD operation, the UE cannot transmit and receive at the same time; this restriction does not apply to full-duplex FDD operation.

      

Ts = 1/(1500 x 2048) sec

Figure 1. Frame Structure Type 1 (full-duplex or half-duplex FDD) 

Frame Structure Type 2

Frame structure type 2, shown in Figure 2, is applicable only to TDD and is provided for compatibility with legacy UTRA TDD systems. Each radio frame consists of two identical 5 ms half-frames. Each half-frame consists of eight 0.5 ms slots and three special fields, Downlink Pilot Timeslot(DwPTS), Guard Period (GP), and Uplink Pilot Timeslot UpPTS. Subframe #0 and #5 and DwPTS are always reserved for downlink transmission.

Ts = 1/(1500 x 2048) sec

Figure 2. Frame Structure Type 2 (TDD only) 

Transmission Parameters (FDD Mode)

Transmission BW

1.4 MHz

3.0 MHz

5 MHz

10 MHz

15 MHz

20 MHz

Slot duration

(frame structure type 1)

0.5 ms

0.5 ms

0.5 ms

0.5 ms

0.5 ms

0.5 ms

Sub-carrier spacing

15 kHz

15 kHz

15 kHz

15 kHz

15 kHz

15 kHz

Sampling frequency*

1.92 MHz

3.84 MHz

7.68 MHz

15.36 MHz

23.04 MHz

30.72 MHz

OFDM symbol length in time units**

(excluding cyclic prefix)

2048

2048

2048

2048

2048

2048

Number of occupied resource blocks

6

15

25

50

75

100

Occupied sub-carriers

73

181

301

601

901

1201

OFDM symbols per slot

(frame structure type 1)

Normal CP

7

7

7

7

7

7

Extended CP

6

6

6

6

6

6

Cyclic Prefix (CP) length

(frame structure type 1)

where l is the symbol position in a slot

Normal CP

160 for l = 0

144 for l = 1 to 6 

160 for l = 0

144 for l = 1 to 6 

160 for l = 0

144 for l = 1 to 6 

160 for l = 0

144 for l = 1 to 6 

160 for l = 0

144 for l = 1 to 6 

160 for l = 0

144 for l = 1 to 6 

Extended CP

512 for l = 0 to 5

512 for l = 0 to 5

512 for l = 0 to 5

512 for l = 0 to 5

512 for l = 0 to 5

512 for l = 0 to 5

* sampling frequency at one oversampling

** 1 time unit = 1/30.72 MHz