Engineering Windows 8 for mobile networks
In this post, we dig into the details of how we have re-engineered the wireless networking stack to optimize it for both mobile broadband and Wi-Fi networks. We’ve done a ton of work to enable mobile broadband providers to make it easy for you to use 3G and 4G connectivity along with Wi-Fi in Windows 8. In addition to this architectural work, we’ve worked on keeping Windows connected to a network even when in a low-power state (when the screen is off, for example) when running on supporting architectures/PCs. You can learn more about this in the //build/ sessions on connected standby. Billy Anders, a group program manager on our devices and networking team, authored this post.
People want similar mobility on their PCs as they get on their smartphones.
It is unlikely that your end goal is just to get connected to the Internet. Instead, connecting to the Internet is a step (or a hurdle) towards what you really want to do, like surf, socialize, or explore, and you would prefer that your PC is connected and ready for you to use whenever you want and wherever you are.
We looked at the fundamentals of wireless connectivity and re-engineered Windows 8 for a mobile and wireless future, going beyond incremental improvements. This is a good example of work that requires new hardware to work in concert with new software in order to realize its full potential.
Simplifying your mobile broadband experience
We knew that if we were to give you true mobility, that Wi-Fi alone would not be enough. Therefore, for Windows 8, we fully developed and integrated mobile broadband (MB) as a first-class connectivity experience within Windows – right alongside Wi-Fi.
We first included mobile broadband in Windows 7, but if you were a mobile broadband user, you likely had a number of hurdles to overcome before connecting with mobile broadband. Yes, you needed the requisite mobile broadband hardware (e.g., mobile broadband dongle or embedded module and SIM) and data plan, but you also needed to locate and install third-party device drivers, and in some cases software, before ever getting your first connection. If the drivers for your device and software from your mobile operator were not available locally, you had to find another connection type (perhaps Wi-Fi) to the Internet to search for software on the websites of the PC maker or mobile operator. This placed a sizable hurdle in front of users trying to connect with mobile broadband, right when they most needed that connection.
We wanted to eliminate the guesswork in locating and installing device drivers for mobile broadband. We did this by working with our mobile operator and mobile broadband hardware partners across the industry, designing a hardware specification that device makers can incorporate into their device hardware. In Windows 8, we developed an in-box mobile broadband class driver that works with all of these devices and eliminates your need for additional device driver software. You just plug in the device and connect. The driver stays up to date via Windows Update, ensuring you have a reliable mobile broadband experience.
The USB Implementers Forum (USB-IF) recently approved the Mobile Broadband Interface Model (MBIM) specification as a standard, and major device makers have already begun adopting this standard into their device designs, including some designed for other operating systems. For more information on the specification, see the USB-IF press release.
Helping you manage your connections and radios
Typically, mobile broadband devices come with radio and connection management software. Device manufacturers, PC manufacturers, and mobile operators all develop, distribute, and support these applications for you to connect to their networks, turn radios on and off, configure connection settings, and get contact information for help and support. Prior to Windows 8, you needed these applications to compensate for functionality not provided natively in Windows. This additional software confused and frustrated users by conflicting with the Windows connection manager, showing different networks, network status, and a separate user interface. Windows 8 eliminates this confusion by providing simple, intuitive, and fully integrated radio and connection management.
The new Windows 8 network settings allow you to turn individual radios on and off (Wi-Fi, mobile broadband, or Bluetooth), as well as disable all radios at once with the new “airplane mode.” Windows 8 provides native radio management to eliminate the conflicts and confusion, and to provide a consistent experience for controlling your radios without the need to install additional software. This is new for PCs even though it has obviously long been available on today’s mobile phones (or Windows Mobile phones, going way back).
You can turn airplane mode on or off in one click
The new wireless network settings in Windows 8 allow you to see and connect to all available MB and Wi-Fi networks from one convenient user interface. We made sure that this interface is consistent and allows you to think less about which network you want to connect. Windows does this by starting with the right default behaviors, and then it gets smarter by learning your network preferences over time.
One of those default behaviors is to prioritize Wi-Fi networks over broadband whenever one of your preferred Wi-Fi networks is available. Wi-Fi networks are typically faster, with lower latency, and have higher data caps (if they are not free). When you connect to a Wi-Fi network, we automatically disconnect you from your mobile broadband network and, when appropriate, power down the mobile broadband device, which also increases battery life. If no preferred Wi-Fi network is available, we automatically reconnect you to your preferred mobile broadband network.
To make sure we connect to the right network when multiple networks are available, Windows maintains an ordered list of your preferred networks based on your explicit connect and disconnect actions, as well as the network type. For example, if you manually disconnect from a network, Windows will no longer automatically connect to that network. If, while connected to one network, you decide to connect to a different network, Windows will move the new network higher in your preferred networks list. Windows automatically learns your preferences in order to manage this list for you.
When you resume from standby, Windows can also reconnect you faster to your preferred Wi-Fi networks by optimizing operations in the networking stack, and providing your network list, connection information, and hints to your Wi-Fi adapter. Now when your PC resumes from standby, your Wi-Fi adapter already has all the information it needs to connect to your preferred Wi-Fi networks. This means you can reconnect your PC to a Wi-Fi network from standby in about a second –oftentimes before your display is even ready. You do not have to do anything special for this – Windows just learns which networks you prefer and manages everything for you. This work was a major part of the architectural work we did in the networking stack and with our hardware partners.
Getting connected to mobile broadband
Even with its broad availability, Wi-Fi by itself does not enable the ubiquitous Internet access that users increasingly want. True mobility requires mobile broadband, which provides connectivity over cellular networks (the same networks as your smartphone). However, just including mobile broadband in Windows 8 was not enough. We also wanted to remove any hurdles to getting you connected to mobile broadband, making it simpler, more intuitive, and more like Wi-Fi.
We made things simpler and more intuitive by fully integrating mobile broadband into Windows 8. When you’re ready to connect to a mobile broadband network, you simply insert your mobile broadband device or SIM card into your Windows 8 PC and we take care of the setup.
If you have a carrier-unlocked mobile broadband device that supports carrier switching (this includes most mobile broadband users outside the US), Windows 8 has native support that allows you to select and connect to any supported carrier from within the Windows UI.
Selecting from available carriers (with supported hardware)
We’ve already talked about how we removed the need to install a driver, or a radio and connection manager. We also automatically identify which mobile operator is associated with your device (or SIM card), brand it in the Windows connection manager with the mobile operator’s logo, configure the PC for connecting to the mobile operator’s network, and download the operator’s mobile broadband app (if they have one) from the Windows Store.
If you purchased and activated a data plan along with your SIM or mobile broadband device, all you need to do is connect to the network and we get out of the way, allowing you to do what you want to do.
Getting connected via mobile broadband using an AT&T SIM card
If you don’t already have a data plan and would like to purchase one, then simply click the “Connect” button for the mobile operator you want, and we automatically direct you to their mobile broadband app or website, where you can select a data plan (for example, a time-based, limit-based, or subscription-based plan).
AT&T’s new mobile broadband app walks you through purchasing a data plan
After you’ve purchased your plan, your mobile operator provisions your PC over the air for their network, including information about your data plan details and Wi-Fi hotspots.
Usage details are shown with the connected account
Behind the scenes, Windows identifies the mobile broadband subscriber information, looks up the mobile operator in the new Access Point Name (APN) database, and pre-provisions the system to connect to the operator’s network. Meanwhile, your core connection experience stays the same.
The operator’s mobile broadband app is available via the “View my account” link, or from the app’s tile on the Start screen. Here, you can see how much data you’ve used, pay your bill, manage your account, and get customer support.
AT&T mobile broadband app, account overview
Avoiding “bill shock”
Many of us have read headlines about people receiving surprisingly expensive bills from their mobile operators. The industry has termed this bill shock, and the problem has received enough attention that some governments have begun taking regulatory steps that ask mobile operators to alert their customers when their data usage reaches a certain threshold. Today, mobile operators all have different ways of responding when subscribers exceed their data usage allotment. An operator may block your Internet access, throttle (slow down) your data speed, or simply begin charging you per kilobyte or megabyte. If you are unaware that you are over your data usage limit, you will likely continue using your data plan and rack up additional charges, resulting in shock when you receive your bill.
Prior to Windows 8, we maintained consistent behavior on all types of networks relative to bandwidth usage. With Windows 8, we now take the cost of the network into consideration: we assume that mobile broadband networks have restrictive data caps with higher overage costs (vs. Wi-Fi), and adjust networking behavior with these metered networks accordingly.
As mentioned earlier, we automatically disconnect from mobile broadband and connect you to your preferred Wi-Fi networks whenever they’re available. This reduces your data usage on mobile broadband when possible.
Because many of us use public Wi-Fi, Windows 8 includes support for popular Wi-Fi hotspot authentication types, including WISPr (Wireless Internet Services Provider roaming), EAP-SIM/AKA/AKA Prime (SIM-based authentication), and EAP-TTLS (popular on university campuses). Windows manages the authentication for you when you come within range of a Wi-Fi network that uses one of these methods, so you won’t have to re-authenticate each time (for instance, by going to a web page). This means you get the same automatic behavior at a public Wi-Fi hotspot as you would at home or the office.
On a PC that has both mobile broadband and Wi-Fi, we’ll move you from MB to the less costly Wi-Fi network automatically whenever Wi-Fi is available, again reducing your mobile broadband usage and your potential for bill shock.
Another way we optimize your bandwidth usage is by changing the Windows Update download behavior. For a majority of users, who have turned on automatic updating, Windows Update will defer the background download of all updates until you connect to a non-metered network, such as your home broadband connection. There is one exception, as noted in our earlier post on Windows Update, and that is in the case of a critical security update to fix a worm-like vulnerability (e.g., a Blaster worm). In that case, Windows Update will download the update regardless of the network type. You can always override the deferred download by launching Windows Update and manually initiating the download of updates at a time more convenient to you. Again, you are in full control of your device.
We recognize that most fixed-line broadband plans also have data caps and overage fees. Those data caps are typically much higher than mobile broadband, and therefore we do not change the behavior for these connections. You are always in control and can always mark any wireless network as metered or unmetered by selecting “reduce data usage” in the right-click (or tap and hold) menu for that network.
Marking the Wi-Fi connection as “metered”
We also want Windows applications to behave well on metered networks, so we’ve provided a new set of developer APIs within the ConnectionCost class of the Windows.Networking.Connectivity namespace. If you are an application developer, we encourage you to leverage these APIs and adapt the behavior of your app, such as allowing a low-definition vs. high-definition video stream, or a header-only vs. full-sync of email, depending on the network type. We believe that this adaptive behavior is critical, as it results in actual cost savings for end users. All Metro style apps in the Windows Store must implement these APIs if they use the network.
Even with Windows and other applications behaving smartly on the network, you still may to want to know how much data you have consumed. Windows 8 provides local data usage counters right within the network settings. These counters provide real time local data usage estimates for Wi-Fi and mobile broadband network connections.
Local data usage estimates
The local counters keep track of the amount of data used on each individual network type so you don’t have to. You can reset the counter whenever you want, which may be useful if you want to monitor your usage month-to-month or even within a session. Although you should think of the local data counters as a quick way to determine your usage, they are not a substitute for what mobile operators report as their usage, which may vary slightly, and should be available in the operator’s app.
Another way we help you manage your mobile broadband data usage is by allowing mobile operators to alert you as you approach your bandwidth cap. Some countries have already begun to mandate that operators send messages to subscribers as they approach their bandwidth cap, or once they begin roaming to a different network. The mobile operator sends you an SMS or USSD alert as you approach your bandwidth cap (e.g., 70% used, 85% used, etc.), and the MB operator’s app notifies you and updates its Start screen tile. The following screen shots show what is already available in the Windows Developer Preview (and on the Samsung Preview PC that had an AT&T SIM and plan).
Data usage notification, bottom right.
Data usage information on the mobile operator’s app tile
The Windows 8 task manager provides more granular information if you want to know how much data a particular app has consumed on the network. Here, you can see the approximate active and historical data consumption of any process over metered and non-metered networks. With this information, you can take control by identifying which apps are consuming the most bandwidth and taking action if needed.
Data consumption information in the Windows Task Manager
Here’s a short video that demonstrates some of the new wireless networking features and enhancements in Windows 8.
We designed Windows 8 with you—and mobility—in mind. We set out to simplify your experience with getting and staying connected across mobile broadband and Wi-Fi networks, removing hurdles and whenever possible, doing the right things automatically for you.
– Billy Anders
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