IEEE802.11a

指導教授 : 高永安學生 : 陳穎俊

PLCP preamble

PLCP data modulation and modulation rate change

PLCP preamble 作傳輸時是 採用 OFDM modulated fixed waveform

The IEEE802.11SIGNAL field ,BPSK-OFDM modulated at 6 Mbit/s,shall indicate the modulation and coding rate that shall be used to transmit the MPDU

The transmitter(receiver)shall initiate the modulation (demodulation) constellation and the coding rate according to the RATE indicated in the SIGNAL field.

The MPDU transmission rate shall be set by the DATARATE parameter in the TXVECTOR

PMD operating specifications (general)

• Outline description• Operating frequency range• Channelization• TX RF delay• Slot time• Transmit and receive antenna port impedance• Transmit and receive operating temperature

range

Block diagram of the transmitter and receiver for the OFDM PHY

Operating frequency range

The OFDM PHY shall operate in the 5GHz band ,as allocated by a regulatory body in its operational region.

Spectrum allocation in the 5 GHz band is subject to authorities responsible for geographic-specific regulatory domains(e.g.,global,regional,and national).

Channelization

The set of valid operating channel numbers by regulatory domain

channelization

Channelization

TX RF delay

Slot time

The TX RF delay time shall be defined as the time between the issuance of a PMD.DATA.request to the PMD and the start of the corresponding symbol at the air interface

The slot time for the OFDM PHY shall be 9us, which is the sum of the RX-to-TX turnaround time, MAC processing delay,and CCAdetect time(<4us)

The propagation delay shall be regarded as being included in the CCA detect time

Transmit and receive antenna port impedance

Transmit and receive operating temperature range

The transmit and receiver antenna port(s) impedance shall be 50 maga if the port is exposed.

Type 1 defined as 0 度 C 到 40 度 C

Type 1 defined as -20 度 C 到 50 度 C

Type 1 defined as -30 度 C 到 70 度 C

PMD transmit specificatons

• Transmit power levels• Transmit spectrum mask• Transmit spurious• Transmit center frequency tolerance• Modulation accuracy• Transmit modulation accuracy test

Transmit power levels

The maximun allowable output power according to FCC regulation

Transmit specturm mask

Transmission spurious

Transmit center and Symbol clock frequency tolerance

Spurious transmissions from compliant devices shall conform to national regulations

The transmission center (symbol clock) frequency tolerance shall be 20% ppm maximun .

The transmission center and the symbol clock frequency shall be derived from the same reference.

Modulation accuracy

• Transmitter spectral flatness The average energy of the constellations in each of the spectral lines –16..-1 and +1..+16 will deviate no more than +-2dB from their average energy.

• Transmitter constellation error The relative constellation RMS error,average over subcarriers, OFDM frames, and pacjets, shall not exeed a data-rate depend-ent value

Transmitter constellation error

PMD receiver specificatons

• Receiver minimum input level sensitivity • Adjacent channel rejection• Non-adjacent channel rejection• Receiver maximun input level• CCA sensitivity

Receviver minimum input level sensitivity

The packet error rate shall be less than 10% at a PSDU length of 1000 bytes for rate-dependent input levels shall be the numbers listed in Table 91 or less

The minimum input levels are measured at the antenna connector(NF of 10 dB and 5 dB implementation margi-ns are assumed)

Adjacent (Non-adjacent)channel rejection

The adjacent (non- adjacent) channel rejection shall be measured by setting the desires signal’s strength 3 dB above the rate-dependent sensitivity specified in Table 91 and raising the power of the interfering signal until 10% PER is caused for a PSDU length of 1000 bytes.

The power difference between the interfering and the desired channel is the corresponding adjacent (non-adjacent) channel rejection.

Receiver maximun input level

The receiver shall provide a maximum PER(packet error rate) of 10% at a PSDU length of 1000 bytes, for a maximum input level of –30dB measured at the antenna for any baseband modulation