May 2003

G. Kleindl / SiemensSlide 1

doc.: IEEE 802.11-03/283r0

Submission

Signaling for Adaptive Modulation

byDr. Günter Kleindl

Siemens AG

May 2003

G. Kleindl / SiemensSlide 2

doc.: IEEE 802.11-03/283r0

Submission

Motivation and Requirements

• Adaptive modulation is one method to improve the throughput and/or range • Adaptive modulation requires signaling

• Easy implementation and compatibility to IEEE 802.11a/g

May 2003

G. Kleindl / SiemensSlide 3

doc.: IEEE 802.11-03/283r0

Submission

Conventional Modulation for OFDM-Subcarriers

SNR(f)

f

QPSK 3/4QPSK 1/2BPSK 3/4

16 QAM 1/216 QAM 3/4

64 QAM 3/4

SNRAverage

shift

ing

of g

rid

• All subcarriers get the same modulation alphabet

64 QAM 2/3

BPSK 1/2

May 2003

G. Kleindl / SiemensSlide 4

doc.: IEEE 802.11-03/283r0

Submission

Adaptive Modulation for OFDM-Subcarriers

• Bundles of adjacent subcarriers get individual modulation alphabets

SNR(f)

f

8-PSK4-PSK2-PSKunused

16-QAM32-QAM64-QAM

128-QAM256-QAM

SNRmeanm=3

shifting

of gri

d

SNRAverage

May 2003

G. Kleindl / SiemensSlide 5

doc.: IEEE 802.11-03/283r0

Submission

How to implement ?

Source

Destination CTS ACK

RTS Data

• A small extension in the RTS / CTS frames is a solution

May 2003

G. Kleindl / SiemensSlide 6

doc.: IEEE 802.11-03/283r0

Submission

RTS Frame Format

FrameControl

Duration RA TA FCS

ProtocolVersion

Type Subtype Other Bits

• Take an unused bit combination in the Subtype field to signal in the RTS that a terminal is able to transmit according to the bit loading feature, e.g. Subtype = 0011

May 2003

G. Kleindl / SiemensSlide 7

doc.: IEEE 802.11-03/283r0

Submission

CTS Frame Format

FrameControl

Duration RABit Loading

TableFCS

• The destination terminal measures the RTS subcarriers and answers with a bit loading table for adaptive modulation in the CTS frame.

• The source modulates the data frame according to the bit loading table.

May 2003

G. Kleindl / SiemensSlide 8

doc.: IEEE 802.11-03/283r0

Submission

Example of a Bit Loading Table

• Number 8 possible PHY-modes and select one for each of the 16 bundles, i.e. 3 bit x 16 = 48 bits = 6 bytes. Transport these bytes in the CTS frame.

000 Nil

001 BPSK

010 QPSK

011 8 PSK

100 16 QAM

101 32 QAM

110 64 QAM

111 128 QAM

May 2003

G. Kleindl / SiemensSlide 9

doc.: IEEE 802.11-03/283r0

Submission

Range Enhancement

0

20

40

60

80

Ran

ge e

nh

ance

men

t /

%

6 9 12 18 27 36 54

Data Rate / Mbps

• Adaptive modulation can significantly improve the range

May 2003

G. Kleindl / SiemensSlide 10

doc.: IEEE 802.11-03/283r0

Submission

Other Company’s ResultsDoc.#: 11-02-232r0-WNG from Aware

• Adaptive modulation can significantly improve the throughput

May 2003

G. Kleindl / SiemensSlide 11

doc.: IEEE 802.11-03/283r0

Submission

Conclusions

• Adaptive modulation is one method to improve the throughput and/or range

• The available RTS/CTS signaling can easily be extended for adaptive modulation and further techniques like multiple transmit antennas

May 2003

G. Kleindl / SiemensSlide 12

doc.: IEEE 802.11-03/283r0

Submission

Thank you foryour attention !