Downlink Frame Ratio (802.16 OFDMA)

Menu Path: MeasSetup > IEEE 802.16 OFDMA Demod Properties > Format tab

 Default: 50% (See OFDMA Standard Presets Table.)

 Range: 0% to 100%

(applies to Downlink only)

The Downlink Frame Ratio parameter specifies the downlink subframe length (including the TTG BS transmit/receive transition gap: A gap between the last sample of the downlink burst and the first sample of the subsequent uplink burst at the antenna port of the base station (BS) in a time division duplex (TDD) transceiver. This gap allows time for the base station (BS) to switch from transmit to receive mode. During this gap, the BS is not transmitting modulated data but simply allowing the BS transmitter carrier to ramp down, the transmit/receive (Tx/Rx) antenna switch to actuate, and the BS receiver section to activate. Not applicable for frequency division duplex (FDD) systems.) and the start of the Uplink subframe. Downlink Frame Ratio (in percent) is the ratio of the Downlink subframe length to the Frame Length. The Downlink Frame Ratio defines where the Uplink subframe starts relative to the start of the frame. A 30% Downlink Frame Ratio means that 30% of the frame length is Downlink subframe and 70% is Uplink subframe.

The IEEE Institute of Electrical and Electronics Engineers. A US-based membership organisation that includes engineers, scientists, and students in electronics and related fields. The IEEE developed the 802 series wired and wireless LAN standards. Visit the IEEE at http://www.ieee.org 802.16 OFDMA standard allows the UL Up Link (reverse link: from cell phone to base station) subframe to be located at non-symbol interval offsets from the frame start. Also, starting with IEEE 802.16e-2005, knowledge of the uplink zone symbol offset relative to the subframe start location is required to compute the PRBS Pseudo-Random Binary Sequence. A "Downlink Ratio" parameter with limits between 0% to 100% defines where the uplink subframe starts.

Example

A configuration with a Zone Symbol Offset = 0 symbols, a Downlink Frame Ratio of 70% and a Frame Length of 5ms will imply the analysis zone begins concurrent with the start of the uplink subframe which begins at 3.5ms after the start of the frame.

See Also

Frame Length (802.16 OFDMA)

Offset (Zone Definition) (802.16 OFDMA)

Length (Zone Definition) (802.16 OFDMA)

Format Tab (802.16 OFDMA)