March 2002

A. Batra et al., Texas Instruments

Slide 1

doc.: IEEE 802.11-02/220r0

Submission

Proposal for a 4 Channel Option to Increase Capacity in the 2.4 GHz ISM

Band

Anuj BatraKofi Anim-Appiah

Matthew B. Shoemake

Texas Instruments

March 12, 2002

March 2002

A. Batra et al., Texas Instruments

Slide 2

doc.: IEEE 802.11-02/220r0

Submission

Motivation (1)

To use the spectrum in the 2.4 GHz ISM band more efficiently.

To increase the number of simultaneous users that can be supported in a given network.

To make network planning in enterprise environments easier.

Even though the primary focus for IEEE 802.11g has been on data rate extensions, capacity extensions are just as important. Should consider methods for increasing capacity that will prolong the utility of the IEEE 802.11g standard.

March 2002

A. Batra et al., Texas Instruments

Slide 3

doc.: IEEE 802.11-02/220r0

Submission

Motivation (2) IEEE 802.11b standard currently allows for only three

non-overlapping channels: – Channels 1, 6, and 11 (channel spacing = 25 MHz).

IEEE 802.11a standard uses a channel spacing of 20 MHz.

Total available spectrum = 83.5 MHz.

Could we use a channel spacing of 20 MHz for the IEEE 802.11g standard?

If we could reduce the channel spacing, then it would be possible to place four non-overlapping channels in the ISM band.

March 2002

A. Batra et al., Texas Instruments

Slide 4

doc.: IEEE 802.11-02/220r0

Submission

Implications / Constraints Reducing the channel spacing to 20 MHz:

– Primarily affects single-carrier signals: Barker, CCK, and PBCC, in the IEEE 802.11g draft.

– Need to verify that we can restrict the bandwidth of the single-carrier signals to 20 MHz.

– Should not have an impact on the multi-carrier signals in the IEEE 802.11g draft, because those signals were designed to work with a channel spacing of 20 MHz.

Need to verify that it is still possible to transmit at least 20 dBm on each channel when the channel spacing is reduced.

The exact transmit power levels will depend on factors such as:– Spectral regrowth introduced by the PA. – Noise from DAC.– EVM of the transmitted signal.

March 2002

A. Batra et al., Texas Instruments

Slide 5

doc.: IEEE 802.11-02/220r0

Submission

By using spectral shaping, it is possible to restrict the bandwidth of a single-carrier signal to 20 MHz.– Ex: SR-RC filter ( = 0.6) that extends over 4 symbols (before PA).

– 99.994% of the energy is contained within 20 MHz of fc (42-db BW = 20 MHz).

Spectral Shaping for Single-Carrier Signals

March 2002

A. Batra et al., Texas Instruments

Slide 6

doc.: IEEE 802.11-02/220r0

Submission

FCC Regulations Need to ensure that new channelization scheme meets

FCC out-of-band requirements (15.205 and 15.209).

Restricted bands of operation (15.205):– 2310 MHz – 2390 MHz (band below the ISM band).– 2483.5 MHz – 2500 MHz (band above the ISM band).

For frequencies in the restricted bands above 960 MHz, the emissions from an intentional radiator shall not exceed a field strength of 500 V/m when measured at a distance of 3m (15.209).– Equivalent to an average radiated power of –41.25 dBmi in

any 1 MHz band.– The transmission duty cycle within a 100msec period must

also be considered when measuring the average radiated power.

March 2002

A. Batra et al., Texas Instruments

Slide 7

doc.: IEEE 802.11-02/220r0

Submission

Proposed 4 Channel Option

Define CHNL_ID = 0 to correspond to a center frequency of 2407 MHz.

Propose the following optional 4 channel scheme for the IEEE 802.11g draft.– Channel spacing = 20 MHz.– Channels 0 and 12 are approximately the same

distance from the forbidden bands.

2467 MHz2447 MHz2427 MHz2407 MHz

2483.5 MHz2390 MHz

CHANNEL 0 CHANNEL 4 CHANNEL 8 CHANNEL 12

March 2002

A. Batra et al., Texas Instruments

Slide 8

doc.: IEEE 802.11-02/220r0

Submission

Total transmit power for each channel is 20 dBm (Resolution BW = 1 MHz).

SR-RC transmit filter ( = 0.6) that spans 4 symbols. Rapp Model with p = 3.

Spectrum for Single-Carrier Modulation

March 2002

A. Batra et al., Texas Instruments

Slide 9

doc.: IEEE 802.11-02/220r0

Submission

Spectrum for Multi-Carrier Modulation

Total transmit power for each channel is 20 dBm (Resolution BW = 1 MHz).

Tapering transition duration of TTR = 150 ns. Rapp Model with p = 3.

March 2002

A. Batra et al., Texas Instruments

Slide 10

doc.: IEEE 802.11-02/220r0

Submission

Conclusion

Proposed a new optional channelization scheme for the IEEE 802.11g standard that accommodates 4 non-overlapping channels.

Showed that it may be possible to transmit at least 20 dBm on each of the 4 channels and still meet FCC requirements.– Further study is needed.