doc.: ieee 802.11-12/0935r0 submission july 2012 vinko erceg, broadcom 6-10ghz uwb link budget and...
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doc.: IEEE 802.11-12/0935r0
Submission
July 2012
Vinko Erceg, Broadcom
6-10GHz UWB Link Budget and Discussion
Date: 2012-07-17
Authors:
Name Affiliations Address Phone email
Vinko Erceg Broadcom 16340 West Bernardo Dr., San Diego, CA
92127
858-521-5885
Ron Porat Broadcom 16340 West Bernardo Dr., San Diego, CA
92127
Hongyuan Zhang Marvell
Edward Au Huawei
George Calcev Huawei
Carlos Cordeiro Intel
James Wang Mediatek
Slide 1
doc.: IEEE 802.11-12/0935r0
Submission Vinko Erceg, Broadcom
Outline
• This contribution presents 6-10GHz UWB technology link budget
• We also discuss implications of the link budget on the UWB technology and existing proposals to form a Study Group in 802.11
• We propose other more promising technologies that could be investigated for the next generation of WLAN, as continuation of 802.11ac
Slide 2
July 2012
doc.: IEEE 802.11-12/0935r0
Submission Vinko Erceg, Broadcom
UWB Link Budget (6-10 GHz) (1)
• Current FCC regulation is: – PSD limit is at -41.3 dBm/MHz
• -14.3 dBm Tx power assuming 500 MHz BW– Later regulatory change allowed for higher power in the case
system supports frequency hopping• For example 3 hops result in 4.8 dB higher Tx power
• Free Space Path Loss is assumed at 10 m with center frequency of 8 GHz (6-10GHz band mid frequency)
• Path Loss = 70.5 dB
Slide 3
July 2012
doc.: IEEE 802.11-12/0935r0
Submission Vinko Erceg, Broadcom
UWB Link Budget (6-10 GHz) (2)
• Link Budget assumptions:– Tx Power = – 14.3 dBm – Path Loss = 70.5 dB – Noise Floor @ 500 MHz BW = – 87 dBm– Implementation and Noise Figure loss = 3 dB + 6 dB = 9 dB
• Resulting SNR at 10 m distance without shadow fading and small scale fading margin is:
SNR = – 14.3 dBm – 70.5 dB – 9 dB – (– 87) dBm = – 6.8 dB
Slide 4
July 2012
doc.: IEEE 802.11-12/0935r0
Submission
July 2012
Vinko Erceg, Broadcom
AWGN SNR Requirements• AWGN SNR requirements for different modulation/coding levels at 10% PER:
Slide 5
Modulation Coding Rate (R) SNR (dB)
BPSK 1/2 1
QPSK 1/2 4
QPSK 3/4 6.5
16-QAM 1/2 9.75
16-QAM 3/4 13
64-QAM 2/3 17.25
64-QAM 3/4 18.75
64-QAM 5/6 19.75
256-QAM 3/4 24.75
doc.: IEEE 802.11-12/0935r0
Submission
Link Budget Discussion
• UWB SNRs without fading margin are -6.8 dB, -0.8 dB and 5.2 dB at 10 m, 5 m, and 2.5 m, respectively.
• We estimate based on [1] at least 6 dB small scale fading margin loss bringing the SNR down to -12.8 dB, -7.8 dB and -0.8 dB at 10 m, 5 m, and 2.5 m, respectively.
• AWGN requirement for BPSK R=1/2 is 1 dB SNR, while UWB SNR with fading margin of 6 dB at 10 m is –12.8 dB, i.e. 13.8 dB is missing to close the link. At 2.5 m 1.8 dB is missing to close the link
• Shadow fading margin may also need to be included to account for blockages and NLOS conditions
• 500 MHz signal BW with BPSK R=1/2 results in approximately 200 Mbps PHY data rate, and 16-QAM R=1/2 results in approximately 800 Mbps PHY data rate.
• For better link margin, UWB system would require complex techniques such as multiple antennas and frequency hopping in addition to spectrum inefficient techniques such as lowering the lowest data rate
July 2012
Vinko Erceg, Broadcom
Slide 6
doc.: IEEE 802.11-12/0935r0
Submission
11ac compared to 15.3a
• [1] defines the MB-OFDM UWB data rates from 53Mbps up to 480Mbps• 11ac one antenna 80MHz rates with SGI are 32.5Mbps up to 433Mbps• [2] claims “At 320Mb/s at 8.2GHz, radius of coverage is ~2 meters with SISO OFDM” -
this is the equivalent of MCS7 using the mandatory 80MHz SISO throughput, and MCS7 can be achieved at much larger distances.
• 11ac link budget @5.5GHz, 80MHz has 20log10(8/5.5)+10log10(500/80) = 3.25dB+8dB=11.25dB increased gain. Coupled with 18dBm transmit power that translates to 18-(-14.3)+11.25 = 43.5 dB SNR advantage!
• What is the value of power compared to BW? Due to regulatory power limit, UWB devices may need to operate at very low SNR where the capacity is proportional to the total received power and is insensitive to BW [3]. – Hence, at -14.3dBm UWB is at a disadvantage compared to 11ac as long as 11ac transmits
higher power.
• In addition we note that the efficiency of packet based systems reduces with operation at negative SNR due to increased preamble length (for improved synchronization and channel estimation) further reducing effective throughput of UWB systems.
July 2012
Vinko Erceg, Broadcom
Slide 7
doc.: IEEE 802.11-12/0935r0
Submission
To UWB or Not to UWB ? • Previous standardization and market itself have failed in the past:
– 802.15.3a withdrew PAR– 802.15.4a did not get enough market traction
• Would standardizing the UWB technology within 802.11 with potentially better software make much difference this time for it to be successful?
• The fundamental problem of low transmit power requirement by regulatory bodies has not changed
• But, 8 years after 15.3a standardization efforts, a new technology (11ac) has emerged that provides similar rates with 80MHz BW at longer distances
• We see no need for an additional technology in addition to current 802.11ac and future 802.11ad products– Both 802.11ac and 802.11ad can close Gbps links at fair distances
• 802.11 WG could explore other more promising paths for next WLAN PHY/MAC protocols
• UWB technology could be considered again in the future when 5 GHz or 60 GHz spectrum becomes over utilized or when regulations change and allow higher transmit power.
• Therefore, for the reasons above, at this point in time we propose “Not to UWB”
July 2012
Vinko Erceg, Broadcom
Slide 8
doc.: IEEE 802.11-12/0935r0
Submission
Future Promising WLAN Evolution Topics
• Better frequency and spatial resource utilization have been discussed in the past in 802.11 and improvements for outdoor cellular offload are being proposed in this meeting as well. See references below.
– General
11-12/68r1 Discussions on the better resource utilization for the next generation WLANs – NTT, Orange
11-11/1464r2 The better spectrum utilization for the future WLAN standardization, Yasuhiko Inoue, et. Al.
11-12-0910-00-0wng-carrier-oriented-wifi-cellular-offload.ppt– OFDMA
11-09/138r3 OFDMA Related Issues in VHTL6, James G., et. al.
11-10/317r1 DL-OFDMA for Mixed Clients, Brian H., et. al.
11-10/787r1 MU with Frequency Domain Multiplexing, Chao-chuu W., et. al.
11-10/1054r0 Wide Band OBSS Friendly PSMP, James W., et. al– Uplink MU-MIMO
11-09/849r1 Uplink Intensive Usage Models, Rolf de Vegt
11-09/852r0 UL MU-MIMO for 11ac, Richard Van Nee, et. al
11-09/1036r0 Uplink MU-MIMO Sensitivity to Power Differences and Synchronization Errors, Richard Van Nee– Others
11-09/1044r0 Distributed Transmission Timing Adjustment for Synchronous Frame Arrival, Sunggeun Jin, et. al.
• As for 60 GHz, proposals for evolution of 11ad for higher rates will likely come up as 11ad products start to appear in the marketplace.
July 2012
Vinko Erceg, Broadcom
Slide 9
doc.: IEEE 802.11-12/0935r0
Submission
References
[1] 15-05-0648-00-003a-mb-ofdm-updates.pdf[2] 11-11-0385-01-0wng-ultrwideband-spectrum-for-802-11.ppt[3] Fundamentals of Wireless Communications – Chapter 5.2.2
July 2012
Vinko Erceg, Broadcom
Slide 10