Wednesday, June 10, 2009

The coming evolution of wireless local area networks (in healthcare, academe and elsewhere) means better video, voice, and data

Wireless local area networks are about to become more pervasive because greater numbers of end users are going to be more favorably impressed than ever with their performance and greater numbers of administrators are going to be more favorably impressed than ever with their cost/benefit ratio. The emerging Wi-Fi standard, 802.11n, is behind these changes.

The examples of 802.11n networks outlined in this post are taken from the healthcare industry and education, but they apply equally well to any networked environment -- and, today, that means just about every environment. Healthcare, especially, with its stringent security requirements, large files like X-rays and changing physical environment caused by portable equipment will benefit from this nascent wireless standard as much and sometimes more than any other field.

With the ubiquitous coverage that 802.11n promises, doctors and nurses will have full network access whether at the patient’s bedside, in wards, or in the waiting areas. Office workers and others ancillary staff will be able to move their laptops and other mobile devices from their desks to a conference room or to a cross-campus facility, more often than not seamlessly.

While 802.11n is not expected to be ratified before Q4 of this year at the earliest, draft versions of 802.11n are already making it possible to run bandwidth-hungry applications like VoIP and video streaming. The draft 802.11n products currently on the market demonstrate a significantly higher throughput and improved range. And, the 802.11n standard promises to achieve as much as 5x the throughput and up to double the range over legacy 802.11 a/b/g technology.

At this level of throughput and range performance, 802.11n can support multimedia applications, with the ability to transport multiple high-definition (HD) video streams, while at the same time accommodating Voice over Internet Protocol (VoIP) streams and data transfers for multiple users with high Quality of Service (QoS) and latest generation security protections in place. In enterprise, campus and municipal networks, 802.11n offers the robustness, throughput, security and QoS capabilities that IT managers have come to expect from wired Ethernet networks. But, wireless devices have this one additional attribute: they are not tethered to a wall jack like wired ones and that makes all the difference in the world.

I've linked to a number of videos so that you can see some of this functionality in action:

It is well documented that wireless performance varies based on a variety of factors such as the type of applications delivered over Wi-Fi or the physical challenges presented by building materials or architectural configurations. Cisco’s lab testing engineers have consistently reached connection data rates of 300 Mbps per 802.11n radio. This data rate typically translates to a throughput rate of 185 Mbps for sustained periods of time.


Before the introduction of 802.11n, a healthcare organization that needed to stream high-definition (HD) video for mobile diagnostic services would be limited to only two HD streams at a time over a wireless network. Even then, an 802.11g network would not be a reliable transport medium for HD streaming video. Previous standards, such as 802.11b, did not have the necessary throughput capacity for any HD video streams.

802.11n allows for the distribution of seven times more video streams than 802.11g networks (Table 1). Such an increase in the throughput rate can truly mobilize applications such as bandwidth-intensive, video-streaming applications. With 802.11n, organizations like the healthcare provider mentioned earlier can dramatically increase the number of simultaneous mobile diagnostics that can be performed. The result is a significant improvement in medical staff productivity, resource utilization, and patient satisfaction (due to shorter wait times), all of which leads to greater profitability.

* In real-life network deployments, Cisco 802.11n solutions have maintained a consistent throughput peak of 185 Mbps. Unfortunately, when it comes to video streaming over Wi-Fi, contention reduces the available throughput per 802.11n radio to roughly 140 Mbps.

** A typical DVD-quality video stream requires about 5 Mbps of throughput. A high-definition video stream requires double the throughput—that is, about 10 Mbps.

8x More Users

The transformative nature of wireless networking drives -- and also feeds -- an insatiable appetite for network-connected devices. Most of us today have at least one Wi-Fi-enabled device, but many of us are starting to carry more than one -- for example, a dual-mode phone, a laptop computer, and a digital camera. We are also becoming accustomed to finding an available network that we can connect those devices to while at home, at work, or on the go, which in turn drives the need for ubiquitous network connectivity.

The proliferation of these network-connected devices is creating an undeniable need for high density deployments as more and more users connect to the same network with multiple devices for different reasons. This need is only exacerbated in areas where people tend to congregate in large numbers for business, education, entertainment, or other reasons.

Consider a large lecture hall where many students congregate during class and are connecting to the wireless network with their laptop computers in order to download the instructor’s presentation slides and notes or conduct parallel, online research on the discussion topic of the day.

If we assume that this large lecture hall is equipped with three 802.11g access points today, the students in the classroom and their connected devices would be sharing an available bandwidth of 22 Mbps by load balancing these users and devices across the three available access points. Now suppose that all these students were required by the instructor to use a “blackboard” type of application to download presentation notes transcribed onto slides in real time. The application would require a consistent bandwidth of 5 Mbps in order to provide a good user experience, and the result would be that only 12 students (four students per access point) would be able to use the application effectively in the classroom.

Suppose we were to replace these three 802.11g access points with three next-generation, 802.11n access points. The system-level bandwidth in the classroom would increase substantially and more than 96 students (32 users per access point) would be able to connect to their wireless network and expect to have a consistent application experience.

In fact, a one-to-one replacement of access points is the most prevalent migration scenario to 802.11n for organizations that want to increase their deployment density. User density becomes an even more complex problem to solve when network users are demanding different bandwidths to run their specific applications. It is not hard to imagine how airport terminal or conference room hotspots, where users run a variety of mobility applications, would benefit from next-generation wireless. Not only would it allow more users on the network, but it could also improve their individual user experience.

Cisco testing has shown that on a systemwide basis, adding devices (users) onto the network may at some point create some throughput loss, up to 5 percent, which will result in slightly fewer additional users being able to use the network. That is why the number of users is not entirely aligned with the expected performance improvement we see from migrating to 802.11n.

9x Faster

Even though Internet or Intranet video streaming and higher user density are both compelling reasons to migrate to 802.11n, the vast majority of companies migrating to next-generation wireless will do so because of the raw performance improvement their users will experience daily. Extensive field testing has shown that sustained throughput performance of 802.11n wireless networks is 185 Mbps. However, in many cases during those field trials, a sustained upper limit of 198 Mbps has been observed.

Companies migrating to a next-generation 802.11n wireless network can expect to experience an improvement in performance that is up to nine times faster than 802.11g technology for the mobile applications used today. Furthermore, many applications, such as scheduled data backups and large file transfers that were previously performed over the wired network, will now be mobilized. These performance improvements increase overall employee effectiveness and productivity and in turn shorten the 802.11n investment payback period, while increasing the return on investment.

There is no doubt that the emergence of 802.11n will also bring about an influx of bandwidth hungry mobile applications that could not be enabled wirelessly until now.

802.11n vs. gigabit Ethernet

Of course, 802.11n speeds still fall far short of those of gigabit Ethernet. However, downloading an 8MB file over 802.11n should take about 4 seconds if there are 10 users on a given access point, compared to less than a second for both fast and gigabit Ethernet. Even with 20 users per access point, the file download times ranged from two to eight seconds -- still satisfactory for most users.

Although latency is up to 20 times higher than that of gigabit Ethernet, the difference will not be enough to impact VoIP. The same can be said of jitter, the amount of variation in the arrival times of VoIP packets. Jitter can be as high as 150 times that of gigabit Ethernet, but who cares? Again, the difference will have little impact on jitter-sensitive applications such as VoWLAN [voice over WLAN] because the absolute value is so small compared to the VoWLAN jitter budget.


This video, the first in a 4-part series on VoIP, is not about wireless, but the concepts, which apply to both wired and wireless networks, may be of interest .

More reliable

802.11n is not only faster, it’s a lot more reliable because it uses “MIMO” -- Multiple Input, Multiple Output — technology. It means, in effect, you have multiple antennas working. So, if a signal doesn’t get through going in one direction, you’re able to send it another way with another antenna, and the signal is more likely to get through. This use of multiple antennas also can mean fewer "dead spots" in coverage.

Better security

802.11n also has better security, with stronger encryption, than 802.11g. That makes 802.11n particularly attractive to small- and medium-size organizations, which don’t have the level of IT resources that larger organizations do.

And, fortunately, all of today's wireless network security best practices still apply to 802.11n. It's important to realize, however, that 802.11n may also raise business risk simply by supporting more users and applications across larger areas. In short, the same old attacks may now be far more disruptive to your business.

Ultimately, 802.11n networks can be made just as secure as -- if not more secure than -- yesterday's 11a/b/g networks. But, this takes awareness and follow-through.

Caveat emptor

Like yesterday's 802.11a/b/g standards, the 802.11n high throughput standard employs 802.11i "robust security." In fact, all Draft n products are required to support Wi-Fi Protected Access version 2 (WPA2) -- the Wi-Fi Alliance's test program for 802.11i.

The good news: All 802.11n WLANs built from scratch can forget about WEP crackers and WPA (TKIP MIC) attacks, because every 802.11n device can encrypt data with AES. The catch: WLANs that must support both old 802.11a/b/g clients and new 802.11n clients may be forced to permit TKIP. Doing so makes it possible for older non-AES clients to connect securely. Unfortunately, 802.11n prohibits high-throughput data rates when using TKIP.

It is therefore best to split old 802.11a/b/g clients and new 802.11n clients into separate SSIDs: a high-throughput WLAN requiring AES (WPA2) and a legacy WLAN that allows TKIP or AES (WPA+WPA2). This can be done by defining two SSIDs on a virtual AP or by dedicating different radios on dual-radio APs. This is only a stop-gap measure, however. As soon as you can retire or replace those legacy devices, do away with TKIP to improve both speed and security.

Forward and backward compatibility

The IEEE 802.11n specification is now stable and converging. Many vendors have stated that their Wi-Fi CERTIFIED 802.11n draft 2.0 products are planned to be software-upgradeable to the eventual IEEE 802.11n standard. The industry now needs assurance that these new products interoperate with each other and that they are backwards compatible with and friendly to the legacy 802.11a/b/g systems. The Wi-Fi CERTIFIED program delivers this assurance.

Devices eligible for certification implement most of the mandatory capabilities in the IEEE 802.11n Draft 2.0 specification. In addition, certain optional capabilities are covered under the certification testing, if implemented in the device. The certification defines and verifies out-of-box behavior of draft 802.11n devices. It also tests for backwards compatibility with and protection of legacy 802.11a/b/g networks from potential disruption by 802.11n. Security and QoS testing are mandatory for the Wi-Fi CERTIFIED 802.11n draft 2.0 products.

Comparing Wi-Fi and WiMAX

Some people describe the difference between Wi-Fi and WiMAX as analogous to the difference between a cordless phone and a mobile phone. Wi-Fi, like a cordless phone, is primarily used to provide a connection within a limited area like a home or an office. WiMAX is used (or planned to be used) to provide broadband connectivity from some central location to most locations inside or outside within its service radius as well as to people passing through in cars. But, be forewarned: just like mobile phone service, there are WiMAX dead spots within buildings.

From a techie POV, the analogy is apt at another level: Wi-Fi, like cordless phones, operates in unlicensed spectrum (in fact cordless phones and Wi-Fi can interfere with each other in the pitiful swatch of spectrum that's been allocated to them). There are some implementations of WiMAX for unlicensed spectrum but most WiMAX development has been done on radios which operate on frequencies whose use requires a license.

Wi-Fi CAN operate at distances as great as WiMAX, but there's a reason why it doesn't. Radios operating in the unlicensed frequencies are not allowed to be as powerful as those operated with licenses; less power means less distance.

Though both offer wireless data connectivity, there are more differences than similarities. Check out the following comparisons:

Coverage Range

The coverage range of Wi-Fi 802.11n is about 400 meters in open spaces but will be lesser indoors. For WiMAX 802.16e, coverage distance can be metro-wide and can be more than 50 km.


Wi-Fi 802.11n was developed to provide faster speed (around 300 Mbps) than the a, b and g variants of this standard. WiMAX on the other hand can handle speeds up to 70 Mbps. It should be noted however, that for both standards, available bandwidth is dependent on many factors such as the distance from the base stations or access points, RF environment and the number of users connected.

Quality of Service

802.11n and WiMAX have different Quality of Service (QoS) mechanisms. This feature is standard in WiMAX and utilizes a method based on type of connection between the base station and the user device. Wi-Fi has introduced a QoS mechanism where certain traffic flows can be prioritized over others. For example, VoIP or video streaming applications may be given priority over ordinary web surfing.

Target Market

Wi-Fi, including 802.11n, was primarily developed for wireless local area networks (WLAN) with a limited coverage area. It has found popular usage in last-mile delivery or consumer applications, such as hotspots in public places, offices or at home. WiMAX, on the other hand, was developed primarily for wireless metropolitan area networks (WMAN) with coverage ranges of up to several kilometers. Service is usually subscription-based and provided by telco operators intended for business users. Example applications are as backhaul for wide area networks or internet connection for ISPs.

Today, Dell customers can add an Intel wireless module that supports Wi-Fi and WiMAX to Dell's Studio 17 and Studio XPS 16 for $60, according to Dell's Direct2Dell blog.

But, wireless broadband networks based on WiMAX are only available in three U.S. cities: Atlanta, Baltimore and Portland, Oregon. That means most users won't get any benefit from adding WiMAX cards to their Dell laptops unless they live in one of these three cities. Over time, more U.S. users will get access to WiMAX networks as operator Clearwire expands coverage to more cities.

HP, the world’s largest laptop maker by units, does not offer WiMax as an option on any notebooks.

Of course, you can always use a USB modem. Sprint’s U300 USB modem, which supports both 3G and Mobile WiMax, is $80 with a two-year contract

Detailed reference on 802.11

Early use of 802.11n at M.I.T. and a medical center command=viewArticleBasic&articleId=9111000