There has been a fair amount of recent news coverage of a faster version of Wi-Fi coming, called WiGig and capable of greater than 1Gbps.

WiGig is an IEEE 802.11 amendment, specifically 802.11ad, for 60GHz operation at greater than a gigabit speed. The high-frequency spectrum used prevents the network from reaching through walls or around corners, and thus is really targeted for home entertainment (such as a wireless HDMI replacement). Nevertheless, through our position in the Wi-Fi Alliance, with whom the WiGig Alliance just agreed to work closely with, and IEEE, we are monitoring the development of this new technology. At the moment, it does not seem that this technology will have significant enterprise applicability.

IEEE has a companion project, 802.11ac, for gigabit operation within the standard Wi-Fi spectrum. This amendment builds upon 802.11n, to provide higher throughput by, in part, using even wider channels and more than four spatial streams. This technology is just in the exploratory stages, and it will be a few years before it reaches commercial products. We are closely monitoring the developments there as well.

Related articles

• Wi-Fi Alliance and WiGig Join Up For 60GHz Wi-Fi Products [Wireless] (gizmodo.com)
• Alliance of Wi-Fi and WiGig Standards in 60 GHz (Glenn Fleishman/Wi-Fi Networking News) (techmeme.com)
• WiGig Alliance Publishes Multi-Gigabit Wireless Specification and Launches Adopter Program (eon.businesswire.com)
• WiGig group opens way to gigabit wireless devices (news.cnet.com)
• Wireless Gigabit set to become next-gen Wi-Fi? (go.theregister.com)
• Next-Gen Wi-Fi specs promise 10x transfer speed, Apple seen as driving adoption (edibleapple.com)
• WiGig Alliance teams with Wi-Fi group for superfast wireless (infoworld.com)
• Next-gen gigabit wireless spec formalized with 7Gbps speeds (arstechnica.com)
• New Frequency Set to Turbocharge Wi-Fi (wired.com)

For wireless networking to succeed in taking over from Ethernet, it has to become dependable—as dependable as wires. People will look back at the development of WLANs to now—even with the launch of 802.11n—and think of the time as the “early days”. This may sound surprising, with WLANs so prevalent in our daily lives, at work, on the road, and in home. But without dependability, WLANs mostly have been just for convenience, and although wireless can now go faster than many wired ports, they have not been as dependable.

So, how do we get to this goal of dependability—the one thing wireless doesn’t have that wires do? We all have to do one additional thing for wireless. We have to perform service level assurance. Service level assurance is the category of networking where service levels are actively measured by injecting traffic into live networks: constant testing of real, live networks, with traffic that represents the applications that mean the most for that network. Put another way, wireless networks can and do change in ways wireline networks don’t, and so they need to always be put through their paces, to make sure they can deliver as expected.

Many organizations do try to do dry runs of applications on wireless—usually, right before the network is deployed. They may gather a few laptops into a room, run some download scripts, and try to estimate how much work their network can do. But once the network is live, the laptops are gone, and there is no more testing taking place. Instead, administrators only monitor the network, looking for changes in graphs and numbers and item counts, hoping to tease out some information on how the network might do. These techniques are all very reactive, and don’t tell a thing on the night before a big meeting, for example, when the network will be used to its fullest.

What wireless needs is for this testing to be proactive, for throughput, loss, and delay tests to be ran on a regular, if not continual, basis. That’s the way to determine whether the network is still functioning at peak capacity, before users find out when it isn’t. Commercial web sites do this all of the time. Utilities do this too. If your network services are critical, you too should be proactively testing your network. But how? It has to be built in to the network. You don’t have the time to drag around laptops. And you probably don’t have the extra budget to install another complete network of sensors. Instead, you really just want the network to test itself, with no additional wireless radios. Until now, there has been no practical solution.

We are changing that with the newly-introduced Meru E(z)RF Service Assurance Manager™ (SAM). SAM overlays onto an existing deployed network, sitting on already-installed hardware as a software blade, proactively injecting end-to-end traffic onto the wireless network. In order for the traffic to get on the air, each access point creates a virtual client. While the access point is running, serving its users, it also is able to act as a client and connect to the access points surrounding it, without disruption. These virtual clients connect from every access point in the network, sending real traffic through the air.

The traffic starts from the Meru services appliance (SA), which already hosts the E(z)RF Network Manager™. From there, it goes to an access point’s virtual client, which connects to another access point and sends that traffic. That traffic then crosses the entire wireless and wireline networks—exactly as real client traffic does, passing through controllers, switches, and routers—before arriving back at the services appliance. In other words, SAM injects live traffic on each access point, sending it back to itself over the complete network, so that it can now measure service levels. Because these are real connections, SAM tests the real network services, including DHCP, security, routing, and quality of service, and reports back on any changes or violations of expected service levels. Every day, SAM sends out a health check email, reporting on the service levels for every access point in the network.

This technology is unique to Meru. There is a solid architectural reason for this. Meru deployments use channel layering. This allows a Meru access point to communicate with its neighbors without disruption—both it and its neighbors are always on the same channel. This way, a Meru access point can perform a “neighborhood watch”, checking on its neighbors by connecting and sending traffic with no penalty to the existing network. Microcell networks cannot do this, and so an access point would have to disconnect all of its clients and change channels just to communicate with its neighbors.

Service level assurance is the key to making wireless networks as dependable as wired networks. Proactive assurance, versus the reactive “detect-then-diagnose” method familiar to legions of wireless network administrators today, prevents IT from being caught off-guard by wireless problems. Users can depend on the network providing the level of service they need for their applications—they know the network has already been verified that day. And IT staff can rely on the network being up to the task, without having to put in any additional effort on their part.

You must have heard or read about new wireless LAN systems being referred to as 3×3 capable or 2×2 capable, or some combination of the two. What does all this mean? Let’s decode the true meaning of these terms.

Products based on the latest and greatest wireless standard, 802.11n, use a technology known as MIMO. MIMO (Multiple In, Multiple Out) utilizes multiple radio chains (and hence multiple antennas) at both the transmitter and the receiver to help increase the throughput and transmit larger amounts of data over the wireless link. At least two chains are required for MIMO functionality; but most systems have more 2 chains. Additionally MIMO utilizes a technique called SDM (Spatial Division Multiplexing) that takes advantage of the multiple transmit and receive radio chains making it possible to send multiple streams of data simultaneously on the same channel, thereby increasing the data rate and overall throughput. All products certified by the WiFi Alliance for 802.11n  must support at least two spatial streams. The IEEE 802.11n specification offers options for up to four spatial streams, though as of now there are no systems available with this feature.

In the industry, 802.11n products are typically described in terms of their MIMO attributes, denoted by TxR where “T” is the number of transmit radio chains and “R” is the number of receive radio chains. (I think that this description is not adequate and generally leads to confusion, but more on that later in this blog). Most of the 802.11n enterprise APs are either 2×3 or 3×3 systems while most of the early 802.11n clients are 2×2 systems. Other combinations are also possible. In addition to the radio chains (and respective antennas), every 802.11n device must have multiple spatial streams, which is rarely talked about or referred to. Rather than the number of radio chains or antennas, the number of spatial streams is the key factor in determining the capability of the wireless device. The number of streams is a property of the radio chipset. All commercially available chipsets on the market today support a maximum of 2 streams for the access point and clients with the exception of Intel 5300 that support 3 streams for the clients. (Intel does not provide chipsets for the Access Points).

Assuming a clear signal, a two spatial stream link will achieve twice the throughput of a single spatial stream in the same channel. Each spatial stream provides data rate up to 150 Mbps while a Draft 2.0 802.11n system with two spatial streams will support up to 300 Mbps. Key point here is that as long as the system supports 2 spatial streams, you can achieve 300 Mbps data rates, regardless of the number of radios chains.

All the systems depicted next have 2 spatial streams and support 300Mpbs data rates with various combinations of transmit and receive chains.

The picture below shows a 3×3 MIMO system with 3 transmitters and 3 receivers on both the AP and the client and 2 spatial streams (denoted by dotted yellow lines). However since the system supports only 2 spatial streams, one pair of antenna is not used for transmission / reception and maybe used for diversity.

This picture shows a 3×2 MIMO system with 3 transmitters and 2 receivers, still supporting 2 spatial streams.

This picture shows a 2×3 MIMO system with 2 transmitters and 3 receivers with 2 spatial streams.

This picture shows a 2×2 MIMO system with 2 transmitters and 2 receivers, again with 2 spatial streams.

As you can see, to describe true capabilities of the system, both the number of radio chains and the number of spatial steams are important to know. While its not the norm, I think that 802.11n products should be described in terms of their MIMO attributes, denoted by TxR:S where T is the number of transmit radio chains, R is the number of receive radio chains and S is the number of spatial streams. Using the S attribute in addition to the T and R attributes, will create more clarity for the end user and help choosing the right product