On the Single-Chip Implementation of

IEEE802.11a

長庚電機通訊組 碩一 張晉銓

指導教授 : 黃文傑博士

Outline

Software simulation of the C-code The system concept and main parameters Analog Front-End introduction A scheme of synchronization blocks SAW filter

IEEE 802.11a structure

Data rate ranging from 6-54 Mb/s Bandwidth 20MHz Modulation: BPSK, QPSK ,QAM. Symbol duration : 4us including 0.8us guard

interval Why we use single-chip?

Computational Requirements of the Baseband Processor

● Software of the model (C-code) on a SUN Sparcstatsion 10 transmitted 1024 bytes 500 times at different bit rates from 6-54 Mb/s

Computational Requirements of the Baseband Processor

●In the receiver, the Viterbi decoder consumes most of the calculation power

●Processing power of the 802.11a system is distributed in an asymmetric fashion between transmit and receive operations.

The OFDM synchronization unit was not modeled

99.9%

The system concept and mainparameters

The complete modem have three main blocks Analog front- end Digital baseband

processor DLC layer

The system concept and mainparameters (conventional)

Super-heterodyne transceiver

Require a narrowband filter (SAW surface acoustic wave).

The I/Q separation be done in the analog domain, which mean that two A/D converters with an analog BW of 10 MHz.

The IF chosen is 810 MHz. Need to be routed off-chip which lead to an increase in p

ower dissipation. Two A/D converter resolution is 10 Bits. Oversampling of 80 MHz. (A/D & D/A)

Super-heterodyne transceiver

Digital IF Receiver Advantage: Gain is distributed ove

r several amplifiers Good selectivity (due t

o the presence of preselect and channel filter

Conversion from a real to complex signal is done at one fixed freq.

● Disadvantage:

●A/D has to be least 20 MHz

●Numerically NCO

●The linearity of receiver hardware need be maintained

Homodyne (Zero IF) receiver LO will translate the desired channel to 0 Hz IF SAW filter are placed with low-pass filter Research Issue:

DC offset Maintenance of I/Q balance Maintenance of low second order distortion

A scheme of synchronization blocks

SPW Model of baseband with synchronization

The estimator is mainly based on autocorrelation and crosscorrelation, and the preamble structure has to be optimized in order to minimize the estimator varience.

Symbol/frame timing offset Carrier frequency offset Sampling clock frequency offset

Approach for synchronization

Sampling clock freq. offset use a fixed clock and an interpolator filter and the filter factor that depend on some error signal.

Use pilot for channel estimation A Gaussian or Lagrange interpolator filter Due to the nearly independent behavior of

correlation functions in time and freq. ,the problem is simplified by using two-dimension Wiener Filters

This SAW filter for the receiving RF circuit of GSM mobile communication equipment operating at 935 MHz ~ 960 MHz.

End

Thank you for your attention