Resource Unit Allocation for Downlink OFDMA

Previously, we examined the method used by 802.11ax access points to communicate OFDMA resource unit (RU) assignments to client devices for uplink transmission of data. This post will explore RU assignments for downlink communication—that is, from the AP to the to the clients.

Because multiple STAs are intended as recipients in downlink OFDMA, the AP must coordinate which RUs are assigned to which STAs, and how those RU assignments are organized in the frequency domain. The SIG-B field in the HE_MU_PPDU contains two subfields used for this purpose:

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• Common Field: Used to communicate how RUs are organized within the channel, using an 8-bit binary code. A table for decoding this assignment for a 20 MHz channel is shown below. The Common Field also contains subfields for communicating the use of the center 26-tone RU in 80 and 160 MHz channels, as well as subfields for the CRC and tail.

• User-Specific Field: As you might guess, this is where per-STA info is held (STA-ID, MCS, etc.)

Example:

An OFDMA AP using a 20 MHz channel has data for four OFDMA STAs. In the RU Allocation subfield of the Common Field within the SIG-B field of the HE_MU_PPDU, it sends 00111000, meaning that the channel will be sub-divided into four RUs: Two 52 tone RUs, a 26 tone RU, and one 106 tone RU. The User Specific Field of the HE_MU_PPDU would further specify which STA is assigned to each RU, along with the STA-ID, number of spatial streams used, whether transmit beamforming applies, the MCS, etc.

A matter of time

This is fairly straightforward and easy to understand, but there’s another interesting aspect of OFDMA worth considering. In 802.11ax, we have to maintain backward compatibility with non-OFDMA capable STAs. This means communication must not only be aligned in the frequency domain, but also in the time domain—meaning that STAs share the same time allocation. Consider that that legacy (OFDM) STAs will still contend for the channel using CSMA. Supposing that a STA participating in a downlink OFDMA transmission was set to receive more data than the others, if the RF energy dropped to near the noise floor in the other RUs as data transmission ended, it’s reasonable to imagine that a legacy STA might not detect enough energy on the channel near the end of the time allocation and begin to transmit, causing a collision. OFDMA STAs are allowed to aggregate frames to fill the time slot, as well as employ fragmentation, but this still doesn’t prevent mismatched ending of data transmission among STAs. To avoid a potential collision in this scenario, padding bits must be transmitted at the same transmit power as the data bits though the end of the time allocation. I’ve created an animation depicting the addition of padding bits to a data transmission below.

Beacons Beckon in the Next Generation of Customer Experience

Aruba Atmosphere is one of the coolest geek experiences to be had. Conference organizers go out of their way to ensure attendees are engaged, entertained, and educated from the moment they leave their hotel rooms for breakfast until they drag themselves back late at night (or the next morning). Not many convention facilities can accommodate the world’s largest mobility conference—especially when extra plans are made for a VR gaming arcade, extra space is reserved for tables of delicious hors d’oeuvres in the technology exhibit areas, and live, professional musicians open keynotes and perform in common areas during breaks. 

Atmosphere 2017 was held at the Gaylord Opryland Resort in Nashville, which was the perfect venue in terms of size and amenities. But the Opryland Resort is huge. Bigly. Seriously, if you haven’t been there, it’s difficult to describe its enormity. Multiple, giant, atriums are connected by a maze of corridors to accommodate nearly 3000 guest rooms, 15 restaurants, 85 event rooms, and ballrooms as large as 150,000 square feet. Pleasing your Fitbit is the least of your concerns. 

For HPE Aruba, who seems to relish opportunities to prove the mettle of its solutions in high risk/reward situations, the Opryland Resort was the perfect facility to showcase how much progress has been made with Meridian Apps in wayfinding and customer engagement.

The Meridian mobile app platform, which Aruba acquired in May, 2013, is the industry leader in indoor, location-based services using Wi-Fi and BLE beacons. It aligns tightly with the company’s vision for enhancing user experience at the mobility edge by providing accessible and easy-to-use tools to create and improve mobile apps that engage users and the mobile devices they’re already carrying.

At Atmosphere 2017, not only were Meridian-driven solutions freely available to attendees, they were arguably indispensable. In my case, it took over twenty minutes to briskly walk from my guest room to the ballroom where the keynote presentations were held, and that’s only if I took the most direct route. With a mind-numbing maze of hallways, atriums, bridges, escalators, and staircases, it was quite easy to find one’s self lost or late.

Prior to the conference, Aruba’s planning teams created a custom conference app for iOS and Android that contained not only highly detailed (yet easy to read) maps of the entire property, they included blue dot wayfinding. This created an equivalent to “indoor GPS” via the placement of dozens—of not hundreds--of Aruba Beacons throughout the resort. Within an hour of my arrival, I gave in to temptation and installed the app. From any non-guestroom area (presumably as an attendee safety measure beacons were off-limits near rooms) my location was nearly pinpointed, and by typing in a search term or selecting a point of interest from a list, turn-by-turn directions were at my fingertips to ensure I didn’t miss a minute of the action. By integrating conference registration databases on the back end, I could even locate my friends and colleagues if they chose to share their location! Need the hours or menu for a restaurant? Meridian Apps make it easy to incorporate contextual data based on location. Not sure where to catch an Uber or Lyft? Just ask the app.

Not every retail or hospitality organization shares Opryland’s complexity driver for location-based services, but Aruba has made Meridian’s tools easy enough to use that much of the work can be handled by non-IT staff. 

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Meridian Editor has a new look if you haven't seen it in awhile.

Meridian Editor is a cloud-based hub of sorts that organizes and updates content for Meridian-powered solutions.  Within Editor, AppMaker lets users customize templates to create cross-platform mobile apps in hours instead of the weeks it takes using traditional “from scratch” development methods. In addition to wayfinding, frameworks are built-in to provide quick roll-out of directories, list pages, calendars, web pages, etc. As such, the apps can transcend turn-by-turn directions and become discovery portals that surface rich, contextual content when and where users find it useful. 

This combination of ease of use and flexible functionality presents practical use cases for a broadening set of entities. Retail stores could take advantage of Meridian’s analytics to measure the success of display racks, better understand traffic patterns, or use push notifications to promote targeted campaigns. Hospitals could build easy-to-use apps for guests to locate patients and loved ones to track vital, up-to-date information. Schools could provide easily updatable directories of facilities and navigation assistance to new students. For those who have already invested in mobile apps, the Merdian SDKs allow developers to incorporate these powerful features without starting over. 

One caveat: Wayfinding drained my iPhone 7+ battery at an alarming rate, and several other attendees I spoke to noticed the same thing across multiple mobile platforms. Radio use represents a significant power consumption challenge for mobile devices (one of the main reasons we don't see more advanced Wi-Fi chipsets in our phones and tablets), so this wasn't entirely surprising. Still, the average user will be taken aback by a 20% battery drain in 30 or so minutes, so efforts to make this technology more power-efficient will be required for it to become truly mainstream. 

Overall I was won over by the usefulness of Meridian Apps at Atmosphere and convinced of its potential in the market. I look forward to Meridian Apps solutions appearing in app store updates at an increasing rate over the next few months, and can’t wait to see how some of the more creative minds out there keep us engaged.

Cloud Management Central to Aruba’s Future

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A recurring theme at Atmosphere 2017 was that innovation at the Mobile First edge is occurring at a breathtaking pace, and the keynotes, sessions, and demo opportunities showcased that mindset everywhere I looked. This year I was part of a team privileged to attend several deep-dive sessions presented by HPE Aruba business units, and the developments around Aruba Central are too compelling not to mention.

For those unfamiliar with Central, it’s Aruba’s cloud-based platform for management and monitoring of its access-layer network solutions—specifically Aruba Instant access points and certain switch models. It’s a rather straightforward solution: Simply have the equipment shipped to a location where Internet access is available, and provide basic guidance to someone on-site (no engineer required!) on connecting the devices with patch cables, and within a few minutes the devices check-in with the Central cloud. Configuration can occur remotely via any modern web browser. The only other real ingredients required are DHCP and some reasonable firewall allowances.

Once configured, switches and access points are monitored with much of the same visibility as AirWave. In fact, Clarity has been incorporated into Central as a tab, providing rich insights into performance of devices and behavior of users on both the wired and wireless networks. If guests are having trouble connecting via a captive portal, or if DNS is having problems (because it’s always DNS, right?), Clarity surfaces those issues in a way the clearly identifies the issue and organizes the data so it’s actionable. Clarity also brings synthetic testing of the wireless network by allowing an access point to pose as a client device in order to gauge performance and test connectivity remotely before the real client devices even attempt to attach. These features are tremendous additions for many targeted users of Central: Network administrators who need to deploy and manage networks at scattered, remote locations such as retail stores, field offices, clinics, etc.

A Reporting tab allows a flexible array of reporting on network trends. These reports include network performance, PCI compliance, and security. They can be generated on-demand, or setup to run periodically and sent to a one or multiple email addresses.

Notifications can be configured to alert network admins to configured events of interest. These might include an access point going offline, rogue access point detection, or an attack on the network infrastructure.

One of my favorite features is integrated console access. Web management consoles are cool, and make life much easier when trying to summarize and visualize data or configure multiple devices via policy or template. But nothing replaces the good, old command line interface when it comes to sinking your teeth into a problem. And, no… menu-selectable commands don’t measure up (I’m looking at you, AirWave). Console cables don’t extend well over the Internet, however, so Aruba’s inclusion of an embedded, virtual console scores high marks in my gradebook of essential features. Without leaving Central, the command line is presented in most of its glory, without wading into flow control, stop bits, or parity.

As a big fan of web-based administration of infrastructure, the best part of Central from my perspective is that it represents the future of Aruba’s management, monitoring, and business insight solutions interfaces. Expect the things you love most about AirWave to continue finding their way into Central, and with Aruba’s massive investment in third party integrations via APIs, eventual connectivity with other great solutions that extend and improve functionality around guest access, security, and analytics. 

You can read more about Aruba Central here, as well as sign up for a demo account where you can add your own devices and experience it yourself. Let me know what you think!

Niara Represents a Strategic Shift in Network Security for Aruba

For years, network and security teams have faced an ever-vexing problem: Fighting threats using policy-based detection always in a permanently reactive posture. There is always a delta between the time a new threat is discovered and the time a policy can be deployed to guard against it. Heuristics have been used with varying degrees of success to help identify malicious files as they emerge in the wild, but this is an inconsistent approach in today’s context of ultra-mobile and IOT devices, BYOD strategies, and cloud computing. In fact, policy (think “definitions”) based approaches to security have become arguably less effective in recent years because of the contextual evolution of computing. Security Information and Event Management (SIEM) methodologies are increasingly adopted among larger and more sophisticated security teams as a result. A subset of SIEM solutions is one that focuses on gathering data about behavior of users and devices on the network and analyze them using machine learning and data analytics rather than attempting to match snippets of data streams against stored databases of fingerprinted threats. This is referred to as User Behavior Analytics (UBA).

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The Niara dashboard

Until now, the mostly Hadoop-driven deployments of UBA solutions have been accessible only to organizations with deep enough wallets to deploy large, complex systems and employ large, erudite teams of security analysts. HPE aims to democratize information security with Niara, a which it acquired for an undisclosed sum within the last few months.

Niara differentiates itself from other UBA solutions with its ability to process network flows in real-time, rather than relying on log-file analysis after the fact. It’s analogous to detecting smoke from the ignition of a match versus scanning the call log from the fire department. In today’s security milieu, seconds can mean the difference between critical data being safeguarded or smuggled out the back door of the network. At Atmosphere 2017, I was part of a team privileged to attend several deep-dive sessions presented by HPE and Aruba business units, and Niara was one of the more impressive. It was apparent that their efforts to streamline, contextualize, and dynamically score network flows in a way that can be easily interpreted by employees who aren’t experienced security analysts will usher in a level of threat containment and data loss prevention to a much broader range of organizations. Niara’s dashboard presentation of individual user behavioral scores, along with the ability to quickly take action on them via ClearPass, was demonstrated during an entertaining keynote session as well.

HPE is already a consensus leader in network access control with ClearPass; additionally, the ability for Niara to natively integrate with the Aruba mobility components lays a peerless foundation for a consistent and actionable security posture--desperately needed as our devices become more diverse and less centrally manageable and the borders of our networks become more nebulous. As the integration of Niara with Aruba’s MobileFirst platform matures, we’ll soon see smaller organizations with leaner security teams deploying world-class SIEM solutions that would have recently been out of reach. Learn more about Niara here, and post back with comments if you’d like to discuss this topic further.

Machine Learning and the Future of Wi-Fi Management

While attending Aruba Atmosphere 2017, I was privileged to be a part of a team of Atmosphere Insiders who attended several deep dive sessions on emerging technologies within the Aruba Mobile First platform. Machine learning and analytics were on full display at Atmosphere, and it’s clear Aruba considers them to be central to the future of their formula for success.

One of the sessions that stood out most to me (as well as several of the other engineers in our group) featured RASA, a recent acquisition that started out as a company that deployed sensors to aggregate critical data points about the RF environment form disparate locations within a building or campus in order to make recommendations about controller and AP settings to improve performance. After being acquired by Aruba last year, the RASA team gained access to analytics gleaned from direct integration with the access point hardware itself, and the results should give pause to every enterprise Wi-Fi competitor in the market.

Why? For years, Wi-Fi manufacturers have developed and refined algorithms to gather and process data points about physical layer performance seen from the perspective of the access point (and to some degree, from associated client devices) in order to make decisions about radio transmit power and channel selection. In the Aruba world, this is known as Adaptive Radio Management (ARM). While ARM works really well in many scenarios, its decisions are based solely on the viewpoints of individual access points. As we know, that’s really only part of the equation when it comes to tuning RF parameters. Client devices often see things very differently down among the bodies and furniture where they operate, and those characteristics can change dramatically as the clients move around through the coverage cell. Good wireless engineers are adept at looking at the network from the perspective of client devices as well, and making further adjustments to compensate. Engineers also can begin to aggregate info from multiple APs and cells, but that data and resulting decisions are only valid until the environmental or situational variables change. It doesn’t take long for a new source of interference or a new usage pattern by a group of end users to invalidate many hours of predictive modeling by an engineer.

RASA offers to not only automate the data gathering and decision process that takes an engineer hours of manual work, but to aggregate it constantly and simultaneously across broad swaths of real estate and wireless spectrum. With millions of data points to examine, much better decisions can be made at both a local cell level and more macro levels as well. Of course, this kind of analysis and feedback is only possible with advanced levels of machine learning, and Aruba has positioned itself to do some pretty incredible things in the near future as a result of its forward-thinking investment in RASA.

As the 802.11x standard emerges in the coming months, the hardware and software will be asked to make increasingly granular decisions in order to benefit from the performance potential that will be no doubt be heavily marketed. Only manufacturers who embrace the promise of machine learning and analytics will be able to truly deliver on them. Aruba is demonstrating its leadership in this realm, and I can’t wait to see what’s next.

Aruba Is Killing the Maintenance Window

On March 1, 2017, over two thousand engineers, technicians, executives, and sales professionals attending Atmosphere 2017 witnessed the first public salvo in Aruba’s campaign to destroy the enterprise Wi-Fi maintenance window. In the boldest display of live demo confidence many of us in attendance had ever witnessed, Aruba CTO Partha Narasimhan and Director of Product Management Peter Lane announced--about 24 minutes into the keynote presentation--that a live upgrade to ArubaOS was occurring on the conference center’s wireless infrastructure as they spoke (and were literally streaming live video over wireless).

Nearly 2,000 client devices connected to three mobility controllers and 192 access points were unaffected as clients were dynamically moved between groups of APs across different controllers while firmware was delivered and applied, and devices rebooted. While the initial reactions of everyone I spoke to that day generally centered around the audacity of challenging the live demo gods so brashly, along with quiet murmurs about the obviously stellar level of confidence Aruba has in ArubaOS 8, the larger message was loud and clear: The infamous “network maintenance window” has been put on notice and its days are numbered. The innovations of the past few years have combined to deliver an unprecedented level of service and reliability that leap beyond mere enhanced user experience. We can more confidently than ever deploy wireless into scenarios with the strictest demands for uptime and reliability.

Aruba calls it Live Update, which conjures memories for me of long days and nights spent monitoring Symantec anti-virus definition rollouts in my younger days, but the moniker is perfect for what’s taking place on Aruba’s wireless infrastructure. It’s now possible in enterprise Aruba wireless environments to upgrade access points, controllers, and supporting software components without somewhere between zero and negligible impact on end users.

There are many obvious scenarios for which this is a game changer, but my thoughts immediately go to the healthcare customers I support—particularly hospitals and other 24x7 patient care facilities. Even in smaller hospitals, emergency rooms operate all day and night. The frailty of human life has no regard whatsoever for an IT department’s need to periodically flash firmware on an access point or ten, which has historically led to both a reluctance to use Wi-Fi for life-critical systems, and notoriously difficult maintenance windows that call in IT staff for 3 AM planned outages whenever they’re granted. While Live Update won’t eliminate maintenance windows for other systems such as network switches or specialty patient care systems, it removes one more significant obstacle in the network management lifecycle and potentially brings wireless into a service level class on par with virtualized, redundant data center systems.

Live Update is made possible by a few recent ArubaOS innovations you may already be familiar with. Just like in the data center, clustering provides a coordinated set of control plane appliances. AirMatch gives Aruba a superior level of radio resource management to provide a healthy environment in which to selectively upgrade and reboot access points. Backup “copies” of client sessions are kept on multiple controllers for allow for a seamless end user experience. ClientMatch further ensures the seamless experience by facilitating unprecedented visibility into how client devices “see” and use the network so controllers know the best way to selectively move clients from one AP to another.

As other mobility innovations settle into place over the coming months, including 802.11ax, as well as security and network intelligence analytics from Aruba’s recent acquisitions of Niara and Rasa, enterprise wireless will further evolve from the access medium of choice into the access method of trust. Over the next few weeks, I’ll explore some of these exciting developments, and what they mean for enterprise Wi-Fi.