802.11b Physical Rates

What are the supported physical data rates in IEEE 802.11b?

1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps.

What modulation schemes does 802.11b use for these rates?

DSSS with DBPSK for 1 Mbps, DQPSK for 2 Mbps, and CCK for 5.5 and 11 Mbps.

Why does 802.11b support multiple physical rates?

To adapt to varying channel conditions and maintain reliable communication.

How does 802.11b select which data rate to use?

Rate selection is based on signal quality, interference, and error rates, often managed by rate adaptation algorithms.

What is the maximum physical data rate achievable in 802.11b?

11 Mbps.

What frequency band does 802.11b operate in?

2.4 GHz ISM band.

How does the physical rate affect range in 802.11b?

Lower rates like 1 Mbps offer longer range and better penetration, while higher rates are shorter range but higher throughput.

Does 802.11b support dynamic rate switching?

Yes, devices can switch rates dynamically to optimize performance.

What is Complementary Code Keying (CCK)?

A modulation scheme used in 802.11b for 5.5 and 11 Mbps to improve data rates while maintaining robustness.

How does 802.11b handle backward compatibility with 802.11 DSSS?

802.11b extends the original DSSS with higher data rates while remaining compatible with 1 and 2 Mbps DSSS devices.

What is the impact of interference on physical rates?

High interference can cause devices to fall back to lower data rates for more reliable transmission.

Are physical rates fixed or configurable in 802.11b devices?

They can be configured but are usually managed automatically by the wireless driver.

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

802.11a supports higher rates (up to 54 Mbps) using OFDM, while 802.11b maxes out at 11 Mbps using DSSS.

What is the symbol rate used in 802.11b?

The basic symbol rate is 1 megasymbol per second.

How are data rates indicated in 802.11b frames?

The rate field in the PLCP header specifies the data rate used for the transmitted frame.

What coding techniques are used in 802.11b to achieve different rates?

DBPSK, DQPSK, and CCK coding.

How does the choice of physical rate impact latency?

Higher rates reduce transmission time, lowering latency, but may require better signal conditions.

Are all 802.11b rates equally robust in noisy environments?

No, lower rates like 1 Mbps are more robust in noise than higher rates.

What mechanisms exist to improve throughput beyond physical rate limits in 802.11b?

Techniques like frame aggregation are not part of 802.11b but are introduced in later standards like 802.11n.

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