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IEEE802dot11a >
   Pilot Addition, 802.11a (PLTADD11A)       

Pilot Addition, 802.11a (PLTADD11A)

 

 


Property

Description

Units

Default

Range/Type

PURPOSE

Signal field {0}

Data field {1}

None

1

[0, 1]/Integer

MODULATION

Modulation Type

None

0

[0, 3]/Integer

CODING

Coding rate type

None

0

[0, 2]/Integer

LENGTH

Length of PSDU (number of octets)

None

100

[1, 4095]/Integer

RIN

Input impedance

Ohm

Inf

(0, Inf]/Real

ROUT

Output impedance

Ohm

0

[0, Inf)/Real

Ports

Input

Signal before pilot addition (complex)

Output

Signal after pilot addition) (complex)

 

Limits

Notes

1. This model can be used for pilot addition according to IEEE 802.11a standard.

2. In each OFDM symbol, four of the subcarriers are dedicated to pilot signals in order to make the coherent detection robust against frequency offsets and phase noise. These pilot signals shall be put in subcarriers –21, –7, 7 and 21. The pilots shall be BPSK modulated by a pseudo binary sequence to prevent the generation of spectral lines. The contribution of the pilot sub­carriers to each OFDM symbol is described in the following sections.

3. The stream of complex numbers at the output of modulation is divided into groups of NSD = 48 complex numbers. We shall denote this by writing the complex number dk,n which corre­sponds to subcarrier k of OFDM symbol n, as follows:

(1)
The number of OFDM symbols, NSYM, depends on the three parameters, Modulation, Coding, and Length. For details, please refer to the pad11a model.

4. The contribution of the pilot subcarriers for the nth OFDM symbol is produced by Fourier transform of sequence P, given by



(2)
The polarity of the pilot subcarriers is controlled by the sequence, Pn, which is a cyclic exten­sion of the 127 elements sequence and is given by the following equation






(3)
Each sequence element is used for one OFDM symbol. The first element, P0, multiplies the pilot subcarriers of the SIGNAL symbol, while the elements from P1 on are used for the DATA symbols.

The subcarrier frequency allocation is shown in Fig.1. To avoid difficulties in D/A and A/D converter offsets and carrier feedthrough in the RF system, the subcarrier falling at DC (0th subcarrier) is not used. Fig.1 Subcarrier frequency allocation

5. To meet 64-point requirement, 11 “zero” shall be put in subcarriers –32~-27 and 27~31.

Fig.1 Subcarrier frequency allocation

Netlist Form

PLTADD11A:NAME n1 n2 [PURPOSE =val] [MODULATION =val]
+ [CODING =val] [LENGTH =val] [RIN=val] [ROUT=val]

Netlist Example

PLTADD11A:1 1 2 MODULATION = 2 CODING= 2 LENGTH = 100

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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