Matthew B. Shoemake, Ph.D. Anuj Batra, Ph.D. May 2001 Range vs. Rate Comparison of Remaining IEEE 802.11g Proposals: PBCC and CCK-OFDM Bill Carney Matthew B. Shoemake, Ph.D. Anuj Batra, Ph.D. Texas Instruments, Inc. Carney, Shoemake, and Batra, TI

PBCC-22 (+.11a): Backwards AND Forward Compatibility May 2001 PBCC-22 (+.11a): Backwards AND Forward Compatibility ga Optional 802.11a OFDM 2.4GHz 54 Data Rate Mbps gb Mandatory PBCC-22 802.11g Mandatory 22 11 802.11b CCK/PBCC Note: PBCC will be in the 2.4GHz band 1999 2001 2003 Carney, Shoemake, and Batra, TI

PBCC-22 (+.11a) No barriers for all market participants May 2001 PBCC-22 (+.11a) No barriers for all market participants Royalty Free IP licenses Texas Instruments offers PBCC cores True 802.11a OFDM system in 2.4GHz PBCC-22 mandatory implementation the technically superior solution for high rate, full backwards compatibility Carney, Shoemake, and Batra, TI

Range vs. Rate Performance May 2001 Range vs. Rate Performance Carney, Shoemake, and Batra, TI

May 2001 Approach Use PER vs. SNR curves for PBCC and CCK-OFDM in conjunction with standard IEEE 802.15.2 path loss models as well as power amplifier back off and maximum sustainable throughput values from authors of PBCC and CCK-OFDM Carney, Shoemake, and Batra, TI

Calculation of Receiver Power May 2001 Calculation of Receiver Power The received power is taken as a simple function of the actual Effective Isotropic Radiated Power (EIRP), the path loss using the IEEE 802.15.2 indoor model, and the PA backoff: PRX = PMAX,TX – PPathloss – PPA Backoff Assume PMAX = 100mW Carney, Shoemake, and Batra, TI

IEEE 802.15.2 Path Loss Model Assumes line of sight for less than 8m: May 2001 IEEE 802.15.2 Path Loss Model Assumes line of sight for less than 8m: Lpath = 10 log (4 p r2 / l) dB, r < 8m After 8m, assumes indoor path loss exponent of 3.3: Lpath = –37.7 + 10 log(4 p r3.3 / l) dB, r > 8m Where: l = wavelength @ 2.45 GHz (0.1224 m) r = range (m) Reference: 802.15 doc. 00/134 Carney, Shoemake, and Batra, TI

Power Amplifier Back-off May 2001 Power Amplifier Back-off The PA Backoff for the remaining proposals are: PA BackOffCCK-OFDM = 6 dB PA BackOffBARKER/CCK/PBCC = 4 dB Using the same radio, CCK-OFDM requires 2 dB more back off than Barker/CCK/PBCC systems. Note that CCK-OFDM has lower average power than Barker/CCK/PBCC. Carney, Shoemake, and Batra, TI

Calculation of Noise at Receiver May 2001 Calculation of Noise at Receiver The noise is taken as a function of the thermal noise received through an ideal matched filter for each modulation and a noise figure: N = Nthermal + NNoiseFigure Assume NNoiseFigure = 6 dB Carney, Shoemake, and Batra, TI

Thermal Noise Floor and Spectral Masks doc.:IEEE 802.11-01/286r1 May 2001 May 2001 Thermal Noise Floor and Spectral Masks The thermal noise floor is: –114dBm/MHz An ideal matched filter will capture a noise power of: OFDM: –95.9 dBm PBCC: –103.6 dBm A CCK-OFDM matched filter will capture 7.7 dB more noise than a Barker/CCK/PBCC matched filter! 10*log10(sum(sinc(linspace(0,20, 1000))).^2*10^(-114/10)*(10e3/1e6)*2 +52*10^(-114/10)) 10*log10(sum(abs(H).^2*10^(-114/10)*(22e3/1e6))*2) Carney, Shoemake, and Batra, TI Carney, Shoemake, and Batra, TI

Calculation of Received SNR May 2001 Calculation of Received SNR The received SNR is then simply calculated as the ratio of the received power to the noise with the addition of a multipath loss factor SNR = PRX / N – Loss where Loss = Implementation Loss + Multipath Margin Assume Loss = 10 dB Carney, Shoemake, and Batra, TI

Calculation of Throughput May 2001 Calculation of Throughput Maximum Sustainable Throughputs (MST) from doc. 01/059 by Halford, Webster and Zyren are used. Assumed data length = 1000B IEEE 802.11b short preamble With ACK packets No backoff (only DIFS included; similar to 802.11e HCF) The throughput TPER is calculated as the MST divided by the average number of attempts to successfully send a packet. (Note that this is a function of the PER.) Carney, Shoemake, and Batra, TI

PER vs. SNR for IEEE 802.11b + PBCC 22 May 2001 PER vs. SNR for IEEE 802.11b + PBCC 22 Plot relates the Packet Error Rate (PER) for for each modulation to the ratio of the signal strength at the receiver to the noise strength at the receiver. Carney, Shoemake, and Batra, TI

May 2001 PER vs. SNR for CCK-OFDM Carney, Shoemake, and Batra, TI

Range vs. Rate Performance May 2001 Range vs. Rate Performance Carney, Shoemake, and Batra, TI

May 2001 Conclusion PBCC-22 has larger range and coverage area than either CCK or CCK-OFDM. 802.11a has higher Maximum Sustainable Throughputs than CCK-OFDM with the same range. Carney, Shoemake, and Batra, TI