By Nader Baghdadi, Regional Director MENA, Ruckus Wireless
The cellular connectivity experience is well understood in virtually every culture, while, except to those involved with its development and testing, Hotspot 2.0 remains a big unknown
“Making Wi-Fi as easy as cellular” is a popular maxim when engineers, marketers, and journalists talk about Hotspot 2.0. And it’s not hard to understand why. The cellular connectivity experience is well understood in virtually every culture, while, except to those involved with its development and testing, Hotspot 2.0 remains a big unknown. Therefore to say Hotspot 2.0 makes Wi-Fi connectivity like cellular puts it in terms that most people can understand.
However, as we approach the launch of production Hotspot 2.0 networks and begin using this technology in our daily lives, it is important to have a more precise understanding of what it is and how it works.
It is at this point that the comparison with cellular connectivity and roaming falls short of conveying what people need to know. For context, it’s best to start examining some of the similarities and differences between cellular and Wi-Fi with Hotspot 2.0, relative to connecting automatically, authentication, and roaming. Airlink encryption aside, users can be assured that robust security is given for both cellular and Wi-Fi (with Hotspot 2.0) connections.
Connect Me.
To connect to any type of network, a client device must support the same physical interface and medium access mechanisms (Layers 1 and 2) as the access network.
Sometimes the compatibility cues are obvious. But in the wireless world, there are no visible cables or connectors and the end users need to have a fuller understanding in order to ensure that their device will connect to an available network.
The first consideration is the frequency band. Does the device “talk” on the same frequency that the network is operating on. Wi-Fi currently operates in swaths of unlicensed 2.4 GHz and 5 GHz spectra that are largely harmonized globally. The first 11 channels (3 non-overlapping) in the 2.4GHz band are de facto “world bands” as they are approved in virtually all regulatory domains. The picture in 5 GHz is currently less uniform, but there are sections (5.15-5.25 and 5.725-5.85 especially) that have been, or soon will be, adopted for unlicensed use in most parts of the world. 5 GHz is the current focus of regulatory bodies since 802.11ac requires it, and commissioners are endeavouring to open more common frequencies there.
So for Wi-Fi at least, a dual-band (2.4 GHz and 5 GHz) device bought in the US today will definitely connect to a 2.4 GHz Wi-Fi network in Europe, Africa, or Asia, and can connect to 5 GHz Wi-Fi networks in most areas of the world.
In the cellular world, the situation with device support is not nearly as straightforward.
This is because licensed spectrum is exclusively allocated in much ‘thinner’ slices to individual mobile operators at the national or regional level. And because the 2G, 3G, and LTE bands vary from country to country, it is impractical to implement a single radio access front end that can support all of the possible RF bands.
One aspect of this is the so-called LTE “band fragmentation” issue. This means that even the most sophisticated handsets have to be produced in a large range of models, which are often specific to a region, country, and/or operator. Even the “international” models can’t hope to support all of the possible operating bands for each generation of technology. At last glance there were 19 different models of the Samsung Galaxy S4s in production to support this collection of different cellular bands.
In contrast to the technology factions that exist within the cellular industry, Wi-Fi modulation and coding implementations have effectively remained uniform as standardized by the IEEE and certified by the Wi-Fi Alliance.
The reality is that Wi-Fi devices are able to connect to just about any Wi-Fi network in the world (and Hotspot 2.0 makes it even easier), while cellular band and technology fragmentation has led to a complex mix of often incompatible devices and networks, especially when traveling outside of the home operator’s coverage area.
Authenticate Me.
Where the cellular user experience truly excels is in the automatic authentication of the device with the network. Each device is provisioned with a unique identifier that is known, and can be verified, by its home operator’s subscriber database (Home Location Register or Home Subscriber Server – HLR / HSS). The identifier is known as an International Mobile Subscriber Identity or IMSI, and can be embedded in a SIM, USIM, or sometimes in the device itself.
The IMSI contains the Mobile Country Code (MCC) and Mobile Network Code (MNC) for the home mobile operator, which together comprise the Public Land Mobile Network (PLMN) ID. A device capable of communicating with a cellular access network can examine the PLMN ID(s) being advertised by the network, and if they match its IMSI, be assured that authentication is possible.
Wi-Fi authentication has been historically rather fragmented primarily due to the diversity of its use (residential, enterprise, hotspot, etc.) and the resulting need for different security requirements. With 802.11, authentication can be open system, based on a static shared code (WEP, WPA-PSK, and WPA2-PSK), or on more sophisticated mechanisms like 802.1X and the Extensible Authentication Protocol (WPA-Enterprise and WPA2 Enterprise). Also, portal-based authentication is often the method of choice for public access Wi-Fi networks, usually in conjunction with 802.11 open auth. These various authentication options are also related to the type of encryption, if any, that is used over the air.
Hotspot 2.0 fixes this by standardizing Public Wi-Fi authentication and security.
With Hotspot 2.0, 802.1X is mandated with EAP-SIM/AKA, EAP-TLS, or EAP-TTLS and AES 256-bit encryption required. The authentication credential can be a cellular IMSI, an X.509 client certificate, or a username/password pair.
The inclusion of non-cellular credentials opens up Hotspot 2.0 services to Wi-Fi only devices like tablets, iPod Touches, laptop computers, and even client devices within the worldwide Internet of Things. Supporting a wide range of credential types also provides for a much broader pool of authentication providers, including mobile operators, cable operators, social media companies, hotel chains, and corporations.
Through the use of the 802.11u protocol, a Hotspot 2.0 Access Point (AP) advertises the PLMN IDs, network access identifier (NAI) Realms (think domain name), and Roaming Consortiums (a 3 or 5-byte hexadecimal identifier issued by the IEEE) for which it can authenticate credentials.
The client device examines these various markers being advertised by the AP, and if there is a match with one of its provisioned credentials, it knows that automatic authentication is possible, and proceeds to connect and begin the EAP process.
Looking Ahead.
So, while it has been helpful up until now to describe Hotspot 2.0 in terms of making Wi-Fi work like cellular, a fuller understanding of the nuances and differences between the technologies and models shows that Wi-Fi can effectively be made easier to use and more pervasive than today’s cellular technologies.
Hotspot 2.0 enabled Public Wi-Fi will offer a service that will be available to all Wi-Fi devices, allow authentication by a number of types of providers, and support roaming consortiums with diverse business arrangements and models. Hotspot 2.0, wherever you may roam. And roam you will.