Wi-Fi Alliance: 7 Reasons Wi-Fi Will Succeed in the Smart Grid


My article 5 Reasons Wi-Fi Will Take a Back Seat for the Smart Grid stirred up a lot of debate in wireless circles — while some agreed with it and some pointed out reasons they felt I’d overlooked, others flat-out disagreed with what I wrote. Among them was the Wi-Fi Alliance, the trade group whose white paper I cited in the story. To that end, Greg Ennis, Wi-Fi Alliance’s technical director, presented me with the group’s own list of reasons why, as he put it, “Wi-Fi will succeed for smart grid deployments.” They are:

1. Huge installed base: An estimated 2 billion Wi-Fi chipsets have shipped as of this year. One of every 10 people in the world uses Wi-Fi for work and leisure.

2. Economies of scale: Like many semiconductor-based technologies, the growth in the market for Wi-Fi chipsets has driven increasing volumes and generated lower prices. This year more than 500 million Wi-Fi chipsets will ship and one billion units are expected to ship in 2011.

3. Carriers already deploy it: Worldwide, all major mobile carriers offer WiFi-enabled handsets. Wi-Fi provides the multimedia-rich experience that subscribers want while conserving expensive spectrum. An estimated 80 million WiFi-enabled handsets shipped in 2008; that number is expected to grow to 300 million in 2011.

4. Residential customers love and trust it, and want their smart energy applications to use it: Consumers enjoy the freedom and convenience of Wi-Fi in an impressive array of devices ranging from computers to mobile handsets and a growing range of consumer electronics.

5. Established certification ecosystem and mature industry: The Wi-Fi CERTIFIED designation has been awarded to more than 6,000 devices. The program is recognized as a designator of quality by consumers and across the technology industry. Testing is conducted in 13 authorized test labs around the world.

6. Innovation in low-power silicon: Several new low-power Wi-Fi chipsets are capable of working in very low-power systems. When integrated into a device that optimizes use of the Wi-Fi radio, these chipsets support battery life of up to 10 years in end points such as utility meters.

7. Innovation in distance networking: Existing city-wide Wi-Fi networks include systems that provide access covering up to 500 meters from the AP, interconnected by point-to-point links based on 802.11 technology and using proprietary mesh protocols. Wi-Fi can be used for both neighborhood network access and as part of a wide area network (WAN) backhaul system.




Below is a comparison of Wi-Fi and Zigbee on various metrics that should be useful:

1: Technology Penetration into Home Products – 2009 (USA)
Wi-Fi: >35% Zigbee: <1%

2: “Number of Certified Products (2009 October)
Source: Wi-Fi Forum Website and Zigbee Forum Website”
Wi-Fi: 6356 Zigbee: <30

3: Band (most used)
Wi-Fi: 2.4-2.5GHz Zigbee: 2.4-2.5GHz

4: Effective Bandwidth / Channel Spacing (most used)
Wi-Fi: 20MHz / 25MHz Zigbee: 3MHz / 5MHz

5: Tolerance of Interference:
Wi-Fi: Good. Wider-bandwidth Spreadspectrum Zigbee: Bad. Narrower-bandwidth Spreadspectrum

6: Tolerance of Multipath – RMS Delay spreads (Implementation dependent)
Wi-Fi: “150ns RMS @ 54Mbps, 500ns RMS @ 1Mbps” Zigbee: 500ns RMS @ 250kbps

7: MAC/PHY Security:
Wi-Fi: WPA/WPA2/CCX are Industry Tested Zigbee: MAC layer security Not available. Relies on Higher layer Security

8: Cost Of solutions:
Wi-Fi: Steadily reducing over years. Single-antenna, Zero-Host, Wi-Fi Chipsets are available today for ~$5 & self-contained modules for ~$10 (including TCP/IP)
Wi-Fi modules inside today’s mobile phones come for less than $4.5 (refer to teardowns e.g,. from isuppli for publicly available information.

Zigbee: Not known

9: Number of Vendors
Wi-Fi: Many Zigbee: Few

10: Data-rate (Max/Typ/Min)
Wi-Fi (b/g): 54Mbps / 36Mbps / 1Mbps
Zigbee: 250kbps alone (Ref: 802.15.4-2006 Section 6.5)

11: Receiver Sensitivity (at Max/Typ/Min data-rates) – Implementation dependent
Wi-Fi (54/36 and 1Mbps) -75dBm / -81dBm / -98dBm
Zigbee (250Kbps) -98dBm

12: Max Packet Length supported
Wi-Fi: 4KBytes (b/g), 64KBytes (n) Zigbee: 127 bytes

13: IP Layer can be directly ported over the MAC?
Wi-Fi: Yes Zigbee: Needs additional layer – 6LowPAN

14: Peak Rx Current @ 3.3V (min/max values for typical implementations in the market)
Wi-Fi: 100 – 200mA Zigbee: 60 – 100mA

15: Peak Tx Current @ 3.3V for 20dBm Tx Power (min/max values for typical implementations in the market)
Wi-Fi: 250 – 350mA Zigbee: 250 – 350mA

16: Shutdown current (min/max values for typical low-power implementations available today)
Wi-Fi: 1 – 5uA Zigbee: 1 – 5uA

17: Energy Efficiency of Reception @ highest datarate (using max values for current consumption)
Wi-Fi: 15nJ / bit Zigbee: 1320nJ/bit

18: Energy Efficiency of Reception @ lowest datarate (using max values for current consumption)
Wi-Fi: 825nJ / bit Zigbee: 1320nJ/bit

19: Does the PHY have error correction coding
Wi-Fi: Yes Zigbee: No

20: Certification for Peer to Peer Low-power operation available?
Wi-Fi: “Yes(Wi-Fi Direct)” Zigbee: Yes

Hope this is useful



This is all well and good but what happens when the next best thing comes down the line and the wifi companies move to that technology and ditch the current one? Smart grid users of the system are left holding the bag. Using wifi for a backhaul system would be acceptable but for the main infrastructure would not be acceptable.

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