802.11a Physical Rates

What are physical data rates supported by 802.11a?

IEEE 802.11a supports physical data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps.

How are different data rates achieved in 802.11a?

Different rates are achieved by varying modulation schemes and coding rates using OFDM.

Which modulation schemes correspond to specific data rates in 802.11a?

BPSK for 6 and 9 Mbps, QPSK for 12 and 18 Mbps, 16-QAM for 24 and 36 Mbps, and 64-QAM for 48 and 54 Mbps.

What is OFDM and how does it relate to 802.11a data rates?

Orthogonal Frequency Division Multiplexing (OFDM) splits the signal into multiple subcarriers allowing higher data rates and robustness.

Does 802.11a support adaptive data rates?

Yes, 802.11a can adapt data rates based on signal quality and interference to optimize performance.

What is the typical range for the highest data rate (54 Mbps) in 802.11a?

Around 20-25 meters indoors, depending on obstacles and interference.

Why are lower data rates like 6 Mbps still used in 802.11a?

Lower data rates improve range and reliability under poor signal conditions.

How does coding rate affect data rate in 802.11a?

Coding rate determines the amount of error correction; higher coding rates mean more data throughput but less error tolerance.

What coding rates are used in 802.11a?

Common coding rates are 1/2, 2/3, and 3/4 depending on the modulation and data rate.

How many OFDM subcarriers are used in 802.11a?

52 subcarriers are used: 48 for data and 4 for pilot signals.

What is the channel bandwidth in 802.11a?

20 MHz channel bandwidth is used in 802.11a.

How does channel bandwidth affect data rates?

Wider bandwidth allows higher data throughput; 802.11a fixed at 20 MHz limits max data rate accordingly.

What is the role of pilot subcarriers in 802.11a?

Pilot subcarriers help with synchronization and channel estimation during reception.

How does 802.11a handle multipath interference with respect to data rates?

OFDM divides the signal into narrowband channels that are less affected by multipath, maintaining higher data rates.

Is there a trade-off between data rate and reliability in 802.11a?

Yes, higher data rates require better signal quality and are less reliable over long distances.

How does 802.11a indicate the data rate of a packet?

The SIGNAL field in the PLCP header specifies the data rate for the payload.

Can 802.11a devices switch between data rates during communication?

Yes, devices implement rate adaptation to switch dynamically based on channel conditions.

What impact does interference have on 802.11a physical rates?

Interference can cause a device to lower its data rate to maintain connection stability.

How does 802.11a compare with 802.11b in terms of physical data rates?

802.11a supports higher maximum rates (up to 54 Mbps) than 802.11b (up to 11 Mbps) due to OFDM and higher modulation schemes.

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