Features

Broadcom responds with FAQ on 54 mbit wireless, after crits

Slightly stung by the accusation that its early implementation of 802.11g isn't an industry standard (it isn't!) Broadcom has responded with an FAQ which sets out its perception of the facts. We reproduce it below ...

In a nutshell, Broadcom feels it isn't alone in jumping the 802.11g gun. "Here are a few points we feel you might have missed in our announcement and story," was the response to our original report last month.

Probably the key facts are that while 11g-type wireless will never deliver data throughputs above 22 megabits per second, at its slowest, it should hit 10 megabits - when operating with an 802.11b network in the same area - which is twice the useful 5 megabit payload of WiFi. And the other point is that answer to the question " Is 54g certified by the WiFi Alliance?

To that, the answer is both no and yes. "54g is certifiable by the WiFi Alliance as an 802.11b compliant product," says the FAQ, but of course, certifiable isn't quite the same as "certified." Ultimately Broadcom, and others, expect it will be certified as an 802.11g product as well. "The WiFi Alliance will wait for the next annual test approval cycle after the 802.11g standard process is completed before certifying 802.11g interoperability. Unfortunately, our customers cannot wait until 2004 for this technology."

Summarising, a Broadcom spokesman said there were four main points they'd want to make. First, "The 802.11g standard is nearly final. There are no significant changes expected by anyone -which is why Broadcom, Intersil, TI and Atheros have all announced OFDM products."

That implies there will be possible changes, even if not significant. "Yes, and our second point is that if there are any changes, BRCM and its customers will provide a free software upgrade which will quickly bring all our products into compliance with the final 802.11g spec."

The company said that its third point was that even those companies which had originally dissented, were coming into line: "All the 'g' chip vendors are implementing the mandatory OFDM modulation; the Broadcom and Intersil implementations are the same. Check out TI's latest press release, which acknowledges that they will ultimately go with OFDM. TI offers their PBCC only as an option."

Finally, Broadcom acknowledge that there is going to be a problem with 802.11b networks operating in the same area. Or, as they phrase it: "There is overhead associated with interoperability with a signal in the same frequency. See the FAQ!

FAQ About 54g: What is 54g?

54g is a new high-speed, compatible wireless LAN technology for home, office and public networks. The 54g logo ensures that products are completely interoperable with other 54g products and are compatible with the draft IEEE 802.11g specification. 54g will quickly become the next mainstream wireless LAN technology because it works faster and farther, is backwards compatible with 802.11b, and is affordable.

What is 802.11g?

802.11g is the new IEEE draft standard specification for high speed wireless LAN communications that provides for up to 54 Mbps data rate in the 2.4 GHz band. It is essentially the OFDM modulation technique used by 802.11a in the 5GHz frequency band, now used in the same 2.4 GHz frequency band as 802.11b. The draft standard requires backwards compatibility with 802.11b.

The draft specification calls for:

o A new physical layer for the 802.11 MAC in the 2.4 GHz frequency band, known as the extended rate PHY (ERP)

o Modulation schemes found in 802.11b including

o Barker code modulation for 1 and 2 Mbps

o CCK for 5.5 and 11 Mbps

o One mandatory new coding scheme

o OFDM for 6,9,12,24 Mbps (mandatory speeds), and 18,36,48, 54 Mbps (optional speeds)

What is the difference between 54g and 802.11g?

54g implements the latest draft of the IEEE 802.11g specification. The two primary distinctions between 54g and 802.11g are:

1) 54g requires 54 Mbps connectivity while 802.11g specifies 24 Mbps performance as mandatory and 54 Mbps as optional

2) It is possible to test interoperability and gain an interoperable seal of approval for 54g but it is not yet possible to do this for 802.11g.

Why isn't this just called IEEE 802.11g?

The IEEE 802.11g standard is nearly complete, but it is technically a draft amendment not a standard. The IEEE prohibits vendors from declaring compliance to a standard until it has gone through the specification writing, review and sign-off process required for ratification. 802.11g is already in the final stages of its review process prior to adoption as an IEEE Standard.

What is the status of the IEEE 802.11g ratification process? What might change?

The 802.11g committee has settled on all the major technology decisions for the specification. The document is essentially being reviewed to clarify sections that may have more than one interpretation. Any changes are expected to be only minor and may require a software update.

802.11g draft specification schedule:

o November 2002 - Resolution of comments from re-circulation ballot and working group (IEEE 802.11TGg) letter ballot issued

o January 2003 - Resolve comments from letter ballot and issue sponsor ballot #1 (IEEE 802.11)

o February 2003 - Resolve comments from sponsor ballot and re-circulate to sponsor ballot pool (IEEE 802.11)

o March 2003 - Submission to review committee (IEEE 802) and potential final approval

o May 2003 - Estimated final approval of IEEE 802.11g as a standard

Which market segments are most likely adopters of 802.11g?

802.11g will be the new mainstream wireless LAN standard and will be adopted across all market segments.

Market analysts expect rapid adoption driven through retail to the home and small business, primarily because the price/performance is extremely compelling.

In the enterprise, the key issues delaying wireless LAN deployment are infrastructure costs, security, and debate over the high bandwidth industry standard. 802.11g solves the dilemma by providing a 54 Mbps option that is low cost, long range and backward-compatible for existing users. For densely populated environments that require increased capacity or 108Mbps data rate, an 802.11a overlay via dual-band 802.11 a/b/g solutions can be deployed. All 54g products have enhanced security that address the enterprise security concerns.

In public access, the inherent backwards-compatibility with existing 802.11b systems and increased range at minimal cost will drive these deployments to 54g.

Performance: what performance should I expect?

54g products will perform differently depending on whether or not there is 802.11b traffic in the immediate environment. The rule-of-thumbs for throughput are:

o In a 54g-only environment, throughput is between 4-5 times the throughput of an 802.11b network. The maximum throughput can exceed 22 Mbps.

o In an environment that includes 802.11b devices, throughput is about double the throughput of an 802.11b network. The maximum throughput can exceed 10 Mbps.

Also, all 54g radios have better sensitivity then current 802.11b radios, and 54g provides outstanding coverage in its 802.11b compatible mode.

Will users really see 54 Mbps with 54g?

No. As with any wireless protocol, 54g has overhead associated with it that limits performance. While signaling data rates of up to 54 Mbps may be achieved, like most shared media (e.g. Ethernet) throughput will be significantly less.

There are two scenarios for 54g performance. In an environment with only 54g clients, throughput of up to 23 Mbps is expected. This performance is equal to that of 802.11a, although 54g is usually available over a greater range - distance - from the AP. The second scenario is when 802.11b clients are present. RTS/CTS flow control must be used to allow 802.11b clients to recognize and establish communications with 802.11g access points. This leads to delays in transmission and drops peak throughput to about 10 Mbps. 54g performance is still well in excess of the maximum measured speeds of 4-5 Mbps for 802.11b.

The use of RTS/CTS is important because it provides determinism to the wireless network, ensuring a minimum bandwidth for each user. Like Ethernet, 802.11 LANs normally use a "carrier sense media access" mechanism to signal transmission without asking for permission from the network. As the network becomes highly loaded, collisions occur more frequently, and the network can become saturated with packet retransmission attempts that eventually make it impossible for any data to get through. RTS/CTS provides a more formalized flow-control mechanism that avoids this problem.

How do I deploy 54g for maximum performance?

54g products should be deployed using the same topology as 802.11b. For densely populated environments that require increased capacity or 108Mbps data rate, an 802.11a overlay via dual-band 802.11 a/b/g solutions can be deployed.

Is 54g certified by the WiFi Alliance?

54g Interoperability: is 54g proprietary?

No, it is merely Broadcom's implementation of the draft 802.11g specification, including all of the mandated data rates, as well as the optional OFDM data rates 18, 36, 48, and 54 Mbps.

How do I know my 54 Mbps products will be interoperable?

Initially, Broadcom will be providing interoperability testing across its customer base to ensure interoperability. Customers who pass these tests will be allowed to use the 54g logo to help consumers choose products that are compatible. For more information and a complete list of compatible products, see www.54g.org.

Is 54g certified by the WiFi Alliance?

No and yes. 54g is certifiable by the WiFi Alliance as an 802.11b compliant product and ultimately we expect it will be certified as an 802.11g product as well. The WiFi Alliance will wait for the next annual test approval cycle after the 802.11g standard process is completed before certifying 802.11g interoperability. Unfortunately, our customers cannot wait until 2004 for this technology.

How should I compare high-speed WLAN technology options?

Customers have three primary options in evaluating new, higher speed wireless LAN technologies; 802.11g, 802.11a and 802.11a/g.

What are the different benefits of 54g versus 802.11a?

In short, 54g offers better range at different data rates than 802.11a, due to better material penetration and multi-path properties. Other advantages of 54g over 802.11a include: backwards compatibility with the installed base of 802.11b users, simpler homologation of the 2.4 GHz band technology for rapid worldwide deployment, and the need to deploy fewer access points.

In order to provide compatibility to 802.11b users, 802.11a vendors now provide dual-band client and access point wireless LAN solutions. The cost of adding an 802.11a radio to a 2.4 GHz solution increases the cost of both the client and the access point.

There are a few situations where 802.11a outperforms 54g, such as environments with many users in a small area. The wider 5GHz band of 802.11a offers more channels, which allows for more simultaneous users to achieve higher throughput. Broadcom has also introduced a dual-band a/g chipset in order to support environments that call for 802.11a performance.

Are there any reasons to deploy 802.11a/b rather than 802.11a/g/b?

No. Anyone migrating to a dual band solution should choose an 802.11a/g/b solution over an 802.11a/b solution for aggregate bandwidth reasons and to be compatible to the new mainstream WLAN standard. Users will experience higher connectivity speeds and network managers can deploy high-speed networks at lower cost by spacing the access points using 802.11g spacing.

What about 802.11b?

802.11b will remain an important component of the wireless LAN landscape. Because of its low cost, size, and power advantage over the newer standards, it will continue to be used in devices where throughput requirements are secondary, such as PDAs and cell phones.

Products and Features - what is being announced?

Broadcom is introducing 4 chips, multiple reference designs and introducing the new 54g logo to indicate compatibility. The new chips are:

· 4306 – 802.11b/54g MAC/baseband

· 4309 – 802.11a/b/54g MAC/baseband

· 2050 – high-performance 2.4 GHz radio chip that supports 54g speeds and improves performance of 802.11b solutions.

· 2060 - Worldwide 5GHz radio chip (4.9 to 5.8 Ghz performance) for a/g platforms

Broadcom's reference designs support cardbus, MiniPCI, access points and wireless routers for 54g and 802.11a/b/54g

When will we see products on the shelves?

54g compliant product will be on the shelves by end of this calendar year, 2002.

What are some of the features that make Broadcom's solutions unique? Broadcom has many advantages over other WLAN providers in general, and specifically in 54g:

First to ship 54g products

· SmartRadio

· OneDriver Software

· Standard-process all-CMOS design

· Hardware-based Advanced Encryption Standard (AES) and WPA implementation

· Easy integration with other technologies

What is clever about SmartRadio design?

SmartRadio is Broadcom's suite of innovative radio design techniques and signal processing algorithms which improve the performance of AirForce wireless LAN devices. These include:

Continuous calibration, which tunes the wireless LAN radio on the fly, providing optimal performance by adjusting to changing environmental conditions. This feature also benefits OEMs by improving manufacturability.

This is in sharp contrast to competitive products, which are usually calibrated once, by test equipment, on the manufacturing line. The traditional approach slows the manufacturing process and does not re-tune the radio to account for changing temperature and environmental conditions during operation.

Wireless echo reduction, which improves 802.11b range in environments with many complex surfaces, such as partitioned office spaces, airports, warehouses, and homes, by using sophisticated equalization techniques to help detect the wireless LAN signal. Wireless echo reduction gives Broadcom 802.11b radios a delay spread tolerance of greater than 250 dB.

Advanced OFDM, which improves throughput in high-speed 54g and 802.11a systems by dynamically adapting to radio noise conditions during the signal decoding process.

What is the advantage of OneDriver and the Advanced MAC architecture?

End-system manufacturers are wary of constantly changing technologies where each design effort is a "one-off" that cannot be leveraged to future generations of products. To minimize this problem in the wireless LAN space, Broadcom designed its solutions around a common hardware, firmware, and software architecture that minimizes the changes an OEM or ODM has to make in order to move to new sets of features.

For instance, the OneDriver software that ships with AirForce solutions uses the same driver for 802.11a, 802.11b, and 802.11g, so that customers of our 802.11b solution will be able to upgrade to the newer high-speed standards without changing their PC's software image. In addition the amount of qualification required for the new solutions will be minimal as they share a common MAC architecture. As a result, new features that support IEEE specifications for 802.11e, h, and i will be available as software updates to existing hardware.

What is the advantage of having an all-CMOS solution?

An all CMOS solution allows us to integrate our chip technologies more readily, giving Broadcom a time to OneChip advantage.

Is there an advantage to hardware-based AES?

Yes. By executing the encryption/decryption in hardware, performance is improved. The alternative is to implement in software, taxing the host processor, which slows down performance.

What is WPA?

WiFi Protected Access (WPA) is a specification from the WiFi Alliance for standards-based, interoperable security enhancements, which strongly increases the level of data protection (encryption) and access control (authentication) for existing and future WiFi wireless LAN systems. All 54g single band and dual band solutions will be WPA enabled.

WPA includes 802.1x as a foundation for port based network access control, authentication and key management, and Temporal Key Integrity Protocol (TKIP), an increased level of security by implementing random re-keying on WEP. It does not include the Advanced Encryption Standard (AES).

Competition - are other semiconductor vendors shipping product based on the 802.11g draft spec?

Many vendors have announced their intention to ship 802.11g product but Broadcom is the first to have partners introduce shipping product.

More information from the organisation set up to promote the new standard, or from Broadcom itself, also by email