== [wiki:OFDM/MIMO MIMO OFDM] | [wiki:OFDM/MIMO#Documentation Documentation] | Shared Memory Spaces ==

[wiki:sysgen2opb sysgen2opb]

= Programmable Modulation Schemes =
The WARP MIMO OFDM core implements a flexible modulation scheme. The core allows any combination of modulation schemes across subcarriers and antennas to be used in a given packet. The schemes are programmed by writing a modulation selection for each subcarrier to a shared memory block in the core. Unique schemes can be programmed for the full-rate symbols at antennas A and B and for the base-rate symbols; see [wiki:OFDM/MIMO/Docs/PHYDetails/FrameFormat OFDM Frame Format] for more details about base- and full-rate symbols.

The transmitter and receiver sections of the core have separate modulation selection memory blocks. The organization of these two memory blocks are identical. The C-code below illustrates the memory organization and how user-code can write to these memory blocks. The macros ''ofdm_TxRx_mimo_SMWO_TxModulation_OFFSET'' and ''ofdm_TxRx_mimo_SMWO_TxModulation_OFFSET'' represent the address offsets (relative to the OFDM core's base address) for the two memory blocks. These macros are defined in the OFDM core's driver ([source:/PlatformSupport/CustomPeripherals/drivers/ofdm_TxRx_mimo_opbw_v1_07_a/src/ofdm_TxRx_mimo.h#L141 ofdm_TxRx_mimo.h]).

{{{
#!c
void setModuation()
{
	//The following modulation schemes match the 802.11a/g standard
	// Each places data on 48 subcarriers
	// Zeros are inserted at the remaining 16 subcarriers:
	//   Subcarrier 0 (DC) must always be zero
	//   Subcarriers 7, 21, -7, -21 are used for pilot tones (i.e. zero data)
	//   Subcarriers [27:31] and [-32:-27] are zero to meet spectral mask requirements

	//The modulation is specified as a vector with 192 4-bit elements
	//The indicies below represent the subcarrier index:
	// x[0:63] specify the full-rate modulation for antenna A
	// x[64:127] specify the full-rate modulation for antenna B
	// x[128:191] specify the base-rate modulation

	//When re-cast as a vector of unsigned ints, the subcarrier indicies are mapped like:
	// [ [7 6 5 4 3 2 1 0] [15 14 13 12 11 10 9 8] [23 22 21 20 19 18 17 16] ...]
	//Thus, 
	//  unsigned int modMasks_qpsk[24] = {0x02222220, 0x22222222, 0x22022222 ...
	//results in zeros at subcarriers 0, 7 and 21...

	//QPSK modulation on 48 subcarriers
	unsigned int modMasks_qpsk[24] = {0x02222220, 0x22222222, 0x22022222, 0x00000222, 0x22000000, 0x22220222, 0x22222222, 0x22222202, 0x02222220, 0x22222222, 0x22022222, 0x00000222, 0x22000000, 0x22220222, 0x22222222, 0x22222202, 0x02222220, 0x22222222, 0x22022222, 0x00000222, 0x22000000, 0x22220222, 0x22222222, 0x22222202};

	//16-QAM on 48 subcarriers
	unsigned int modMasks_16qam[24] = {0x04444440, 0x44444444, 0x44044444, 0x00000444, 0x44000000, 0x44440444, 0x44444444, 0x44444404, 0x04444440, 0x44444444, 0x44044444, 0x00000444, 0x44000000, 0x44440444, 0x44444444, 0x44444404, 0x04444440, 0x44444444, 0x44044444, 0x00000444, 0x44000000, 0x44440444, 0x44444444, 0x44444404};

	//64-QAM on 48 subcarriers
	unsigned int modMasks_64qam[24] = {0x06666660, 0x66666666, 0x66066666, 0x00000666, 0x66000000, 0x66660666, 0x66666666, 0x66666606, 0x06666660, 0x66666666, 0x66066666, 0x00000666, 0x66000000, 0x66660666, 0x66666666, 0x66666606, 0x06666660, 0x66666666, 0x66066666, 0x00000666, 0x66000000, 0x66660666, 0x66666666, 0x66666606};

	unsigned char i;

	for(i=0; i<24; i++)
	{
		//Uncomment one of the following lines to select the modulation scheme at the Transmitter
		*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_TxModulation_OFFSET+i*sizeof(int))) = modMasks_qpsk[i];
		//*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_TxModulation_OFFSET+i*sizeof(int))) = modMasks_16qam[i];
		//*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_TxModulation_OFFSET+i*sizeof(int))) = modMasks_64qam[i];
	}

	for(i=0; i<24; i++)
	{
		//Uncomment one of the following lines to select the modulation scheme at the Receiver
		*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_RxModulation_OFFSET+i*sizeof(int))) = modMasks_qpsk[i];
		//*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_RxModulation_OFFSET+i*sizeof(int))) = modMasks_16qam[i];
		//*((volatile unsigned int*)(XPAR_OFDM_TXRX_MIMO_OPBW_0_BASEADDR+ofdm_TxRx_mimo_SMWO_RxModulation_OFFSET+i*sizeof(int))) = modMasks_64qam[i];
	}
}
}}}

== Receive Packet Buffer ==
=== Address: 0x10000 ===


== Transmit Packet Buffer ==
=== Address: 0x30000 ===