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IEEE802dot11a >
Modulator, 802.11a (MOD11A)

Modulator, 802.11a (MOD11A)

Property	Description	Units	Default	Range/Type
MODULATION	Modulation Type	None	0	[0, 3]/Integer
RIN	Input impedance	Ohm	Inf	(0, Inf]/Real
ROUT	Output impedance	Ohm	0	[0, Inf)/Real
Ports
Input	Bits before modulation (integer)
Output	Modulated signal (complex)

Limits

Notes

1. This model can be used for modulation according to Gray-coded constellation mappings^[1].

2. The OFDM subcarriers can be modulated by using BPSK, QPSK, 16-QAM, or 64-QAM modulation, depending on the RATE requested. The encoded and interleaved binary serial input data shall be divided into groups of N_BPSC (1, 2, 4, or 6) bits and converted into complex numbers representing BPSK, QPSK, 16-QAM, or 64-QAM constellation points. The conversion shall be performed according to Gray-coded constellation mappings^[1]. The output values, d, are formed by multiplying the resulting I + jQ value by a normalization factor K_MOD, as described in Eqn.(1).

(1)
The normalization factor,K_MOD, depends on the base modulation mode, as prescribed in Table I. Note that the modulation type can be different from the start to the end of the transmission, as the signal changes from SIGNAL to DATA, as shown in Fig.1. The purpose of the normalization factor is to achieve the same average power for all mappings. In practical implementations, an approximate value of the normalization factor can be used, as long as the device conforms with the modulation accuracy requirements described in [1].

For BPSK, b₀ determines the I value, as illustrated in Table II. For QPSK, b₀ determines the I value and b1 determines the Q value, as illustrated in Table III. For 16-QAM, b₀b₁ determines the I value and b₂b₃ determines the Q value, as illustrated in Table IV. For 64-QAM, b₀b₁b₂ determines the I value and b₂b₃b₄ determines the Q value, as illustrated in Table V. The input bit, b₀, is the earliest in the stream.

Fig.1 PPDU frame format

Table I IEEE 802.11a Modulation-dependent normalization factor K_MOD

Modulation

(K_MOD)

BPSK

QPSK

16-QAM

64-QAM

Table II IEEE 802.11a BPSK encoding table

Input bit (b₀)	I-out	Q-out
0	-1	0
1	1	0

Table III IEEE 802.11a QPSK encoding table

Input bit (b₀)	I-out	Input bit (b₁)	Q-out
0	-1	0	-1
1	1	1	1

Table IV IEEE 802.11a 16-QAM encoding table

Input bits (b₀b₁)	I-out	Input bits (b₂b₃)	Q-out
00	-3	00	-3
01	-1	01	-1
11	1	11	1
10	3	10	3

Table V IEEE 802.11a 64-QAM encoding table

Input bits (b₀b₁b₂)	I-out	Input bits (b₃b₄b₅)	Q-out
000	-7	000	-7
001	-5	001	-5
011	-3	011	-3
010	-1	010	-1
110	1	110	1
111	3	111	3
101	5	101	5
100	7	100	7

Netlist Form

MOD11A:NAME n1 n2 [MODULATION =val] [RIN=val] [ROUT=val]

Netlist Example

MOD11A:1 1 2 MODULATION = 2

References

1. IEEE Std 802.11a, Part 11: “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band,” ISO/IEC 8802-11:1999/Amd 1:2000(E).

2. J. Terry and J. Heiskala, Proakis, OFDM Wireless LANs: A Theoretical and Practical Guide, Sams Publishing, 2002.

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