802.11e Physical Rates ========================= .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What are physical rates in IEEE 802.11e?** Physical rates refer to the actual data transmission speeds supported at the PHY layer, inherited from 802.11a/g. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does 802.11e define new PHY data rates?** No, 802.11e focuses on MAC enhancements and relies on existing PHY layers like 802.11a, b, and g. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is the range of physical rates supported in 802.11e?** It supports all PHY rates from 802.11a/b/g, ranging from 1 Mbps (DSSS) to 54 Mbps (OFDM). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does QoS affect physical rate selection in 802.11e?** Indirectly—higher-priority traffic may experience better channel access and maintain higher PHY rates more consistently. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How are physical rates selected in 802.11e networks?** Rate selection is handled by rate adaptation algorithms based on signal quality, not directly by 802.11e. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What modulation schemes are used with 802.11e?** Modulation schemes depend on the PHY—e.g., BPSK, QPSK, 16-QAM, and 64-QAM in OFDM (802.11a/g). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can 802.11e be used with 802.11n or later PHYs?** Yes, 802.11e QoS concepts were extended into later standards like 802.11n, ac, and ax. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is the relationship between QoS and physical rates?** QoS prioritizes access to the channel, allowing latency-sensitive traffic to potentially utilize higher PHY rates with fewer retransmissions. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does 802.11e support dynamic rate shifting?** Yes, stations can dynamically adjust physical rates depending on channel conditions, like in other 802.11 protocols. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can 802.11e operate at fixed physical rates?** Yes, fixed rate operation is possible but typically discouraged in favor of dynamic adaptation. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does 802.11e require special PHY hardware?** No, it runs on existing PHY hardware as long as it supports the associated 802.11 standard (a/b/g). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does EDCA relate to PHY rates?** EDCA affects channel access timing, influencing how effectively higher PHY rates are utilized under congestion. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is the role of PHY rate in QoS performance?** Higher PHY rates reduce transmission time, minimizing delays and improving performance for QoS-sensitive applications. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can PHY rates vary during a session?** Yes, physical rates may vary due to rate adaptation algorithms reacting to changing wireless conditions. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does the Access Category (AC) affect PHY rate selection?** No, AC affects MAC scheduling. PHY rate is still chosen based on link quality and device capabilities. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is PHY rate visible to upper layers?** Not directly. Upper layers may observe performance changes but don’t control PHY rate selection. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is the minimum PHY rate in 802.11e?** It depends on the PHY used—for example, 6 Mbps for OFDM (802.11a/g) and 1 Mbps for DSSS (802.11b). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does 802.11e guarantee minimum PHY throughput?** No, but it enhances delivery prioritization to improve service quality, especially under congestion. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is physical rate negotiation affected by QoS policies?** Not directly, but prioritized traffic may avoid retransmissions and experience better link conditions, maintaining higher rates. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What happens if the PHY rate drops in a QoS session?** The MAC may increase retransmission attempts, but lower latency classes may still be served first due to prioritization. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow Topics in this section, * :ref:`physical_rates in 802.11a ` * :ref:`Reference links ` .. _physical_rates_e_step4: .. tab-set:: .. tab-item:: physical_rates in 802.11e ========== === ==== =========== ============ =========== ================ ========= ============ =========== ========== ====== Modulation BW Tsc FSP=BW/Tsc Tdata=1/FSP GI=Tdata/4 Symbol=Tdata+GI 1/Symbol Bits/Symbol Code rate Usable sc Rate ========== === ==== =========== ============ =========== ================ ========= ============ =========== ========== ====== BPSK 5 64 78.125 12.8 3.2 16 0.0625 1 1/2 48 1.5 BPSK 5 64 78.125 12.8 3.2 16 0.0625 1 3/4 48 2.25 QPSK 5 64 78.125 12.8 3.2 16 0.0625 2 1/2 48 3 QPSK 5 64 78.125 12.8 3.2 16 0.0625 2 3/4 48 4.5 16-QAM 5 64 78.125 12.8 3.2 16 0.0625 4 1/2 48 6 16-QAM 5 64 78.125 12.8 3.2 16 0.0625 4 3/4 48 9 64-QAM 5 64 78.125 12.8 3.2 16 0.0625 6 2/3 48 12 64-QAM 5 64 78.125 12.8 3.2 16 0.0625 6 3/4 48 13.5 BPSK 10 64 156.25 6.4 1.6 8 0.125 1 1/2 48 3 BPSK 10 64 156.25 6.4 1.6 8 0.125 1 3/4 48 4.5 QPSK 10 64 156.25 6.4 1.6 8 0.125 2 1/2 48 6 QPSK 10 64 156.25 6.4 1.6 8 0.125 2 3/4 48 9 16-QAM 10 64 156.25 6.4 1.6 8 0.125 4 1/2 48 12 16-QAM 10 64 156.25 6.4 1.6 8 0.125 4 3/4 48 18 64-QAM 10 64 156.25 6.4 1.6 8 0.125 6 2/3 48 24 64-QAM 10 64 156.25 6.4 1.6 8 0.125 6 3/4 48 27 BPSK 20 64 312.5 3.2 0.8 4 0.25 1 1/2 48 6 BPSK 20 64 312.5 3.2 0.8 4 0.25 1 3/4 48 9 QPSK 20 64 312.5 3.2 0.8 4 0.25 2 1/2 48 12 QPSK 20 64 312.5 3.2 0.8 4 0.25 2 3/4 48 18 16-QAM 20 64 312.5 3.2 0.8 4 0.25 4 1/2 48 24 16-QAM 20 64 312.5 3.2 0.8 4 0.25 4 3/4 48 36 64-QAM 20 64 312.5 3.2 0.8 4 0.25 6 2/3 48 48 64-QAM 20 64 312.5 3.2 0.8 4 0.25 6 3/4 48 54 ========== === ==== =========== ============ =========== ================ ========= ============ =========== ========== ====== .. _physical_rates_e_step17: .. tab-set:: .. tab-item:: Reference links * Reference links