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

Proposal for a 4 Channel Option to Increase Capacity in the 2.4 GHz ISM Band. Anuj Batra Kofi Anim-Appiah Matthew B. Shoemake Texas Instruments March 12, 2002. Motivation (1). To use the spectrum in the 2.4 GHz ISM band more efficiently.

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

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  1. Proposal for a 4 Channel Option to Increase Capacity in the 2.4 GHz ISM Band Anuj Batra Kofi Anim-Appiah Matthew B. Shoemake Texas Instruments March 12, 2002 A. Batra et al., Texas Instruments

  2. 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. A. Batra et al., Texas Instruments

  3. 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. A. Batra et al., Texas Instruments

  4. 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. A. Batra et al., Texas Instruments

  5. Spectral Shaping for Single-Carrier Signals • By using spectral shaping, it is possible to restrict the bandwidth of a single-carrier signal to 20 MHz. • Ex: SR-RC filter (a = 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). A. Batra et al., Texas Instruments

  6. 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 mV/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. A. Batra et al., Texas Instruments

  7. 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. A. Batra et al., Texas Instruments

  8. Spectrum for Single-Carrier Modulation • Total transmit power for each channel is 20 dBm (Resolution BW = 1 MHz). • SR-RC transmit filter (a = 0.6) that spans 4 symbols. • Rapp Model with p = 3. A. Batra et al., Texas Instruments

  9. 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. A. Batra et al., Texas Instruments

  10. 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. A. Batra et al., Texas Instruments

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