Success or not?

Will Wi-Fi crush Bluetooth?

The tremendous success of Wi-Fi made available by the Wi-Fi Alliance gave them a huge boost in new members since their start. Almost every (electronic) major or minor company which has something to do with wireless connection is affiliated with the alliance. Wi-Fi has penetrated the market for wireless communication so well that there is no way around it anymore, becoming the de facto standard in this field. However, there is a dependence on the area of application for which it is suited and it is this dependency that gave way to different wireless standards. With the introduction of Wi-Fi Direct it entered the domain of Bluetooth becoming a direct competitor.

"We designed Wi-Fi Direct to unleash a wide variety of applications which require device connections, but do not need the internet or even a traditional network. Wi-Fi Direct empowers users to connect devices - when, where and how they want to, and our certification program delivers products that work well together, regardless of the brand."  - Edgar Figueroa, CEO Wi-Fi Alliance, 2010

As Bluetooth has already been widely implemented in short range data communication for years, Wi-Fi Direct is considered to be the newcomer to this area. With the new Wi-Fi standard a fair comparison can be made between their main features. Wi-Fi Direct clearly has the upper hand compared to Bluetooth when considering data speed, something which should not be taken lightly because of the ever growing demand for higher throughput. The range of Wi-Fi Direct is somewhat longer but this is not of great concern because most of the data transfer is well within Bluetooth's maximum range. Security however, is an bigger issue because of this longer range. For this Wi-Fi Direct has the same proven security algorithms (AES 256-bit encryption) already employed by the Wi-Fi standard.

One of Bluetooth's key feature is his low power consumption which has been improved in the latest version 4.0. However, this low power mode has its caveats as it has limited throughput, is not available when streaming data and is not fully backward compatible with older versions. This is were Wi-Fi Direct fits in the picture. If one device has the updated Wi-Fi Direct chip you are still able to set up a device-device connection with other Wi-Fi compatible products. As the standard evolved from a different point of view, there is still room for improving their energy consumption when working on battery powered devices. For now their main focus lies on easily rechargeable devices like laptops, tablets and smartphones.

Our third competitor ZigBee is evolving more quietly but is on the other end of the 'power consumption vs data rate' spectrum. The idea behind the ZigBee technology is to be very cheap, small and extremely energy efficient. From this point ZigBee is 'pushing' Bluetooth to its limits which it might not be able to live up to. In the area of small sensor (mesh)networks where Wi-Fi Direct might not excel, ZigBee is able to fill these gaps.Furthermore, ZigBee and the Wi-Fi Alliance are partners in developing new specifications for an IP-based protocol where the two would be able to coexist.

Wi-Fi, gateway to the Internet of Things

It is my opinion that in the future Internet of Things where every wireless device is connected to the internet and to each other, Wi-Fi will be indispensable. Wi-Fi Direct will play a key role in connecting the small distance datacommunication with the longer distances through the ability to easily interconnect and easy access to the internet.

Wi-Fi Direct Protocol

Setup of a Wi-Fi Direct connection

As Wi-Fi Direct protocol is based on IEEE 802.11 infrastructure mode it inherits its features like quality-of-service and WPA2 security. The big difference is the ability to dynamically decide the role which the device takes on oneself. After detection of other devices and the need to setup a connection, one device is designated as Group Owner (GO). Every other device in the group to be established is a peer-to-peer (P2P) client. A device can connect to multiple groups by using different frequencies or time-sharing the channel. In this case, it is very well possible to take on a dual role within multiple groups but the Wi-Fi Direct protocol does not allow the role of GO to be transferred within the group. When the GO leaves its group, it has to be torn down to establish a new one.

Initialization of Wi-Fi Direct connection

To establish a standard group formation, to protocol is defined in several phases (see Figure). First of all the discovery phase is initiated which itself consist of three stages. When a device is turn on it scans through all available channels in the current frequency to see if there is already an existing group. When this is not the case it continues and will alternate between search and listen stages. In the search stage the device will send probe request in the three 'Social channels' of the 2.4GHz band while in the listen stage it is able to accept incoming probe request from other sources in one of its predefined channels. The time a device spent in either phase is typically random distributed between 100ms and 300ms but can be set to any value which is a trade-off between energy consumption and discovery time.

When two devices detected each other it is time to establish the GO of the group. This is simply done by comparing their GO intention value. As a GO it is his task to support power saving services, run a Dynamic Host Configuration Protocol (DHCP) to provide clients with IP addresses and have the ability to connect to a external network. It sends out periodic beacon messaged to maintain the group connection with its clients. These tasks are done in the Wi-Fi Protected Setup (WPS provisioning) and the Address configuration phases. Alternatively there are two other, more simple, ways to setup a group formation. This could be an autonomous connection where a device immediately becomes the group GO and starts to beacon messages. The other possibility is a persistent connection in which the groups devices store their network credentials so they could quickly form their old group connection again.

Power consumption or energy management becomes of major importance in devices who depend on batteries. The Wi-Fi protocol already supported energy saving modes for P2P clients which is also implemented here. Wi-Fi Direct has two new power saving modes which the P2P GO controls. In the Opportunistic Power Save mode it is the P2P GO which beacons a minimum time frame in which it will stay awake and so can receive data. Only if all the clients finished their uploads the GO can also go to sleep mode. On the other hand, the Notice of Absence power saving mode allows the GO to preserve more energy but the clients are only able to send information in a certain period of time. The GO defines a schedule for its client including the information of the duration of its sleep mode, the time interval between them, when sleep mode will start and how many times this will be.

This schedule and the time frame in which the client can send information are not defined by the Wi-Fi Alliance specifications. It is left to the different companies who utilize Wi-Fi Direct in their products to differentiate from each other in respect to power savings, features and product quality.

Standarisation regime (2)

Overview:

• Wi-Fi Direct is a de facto standard although it is not as big as Wi-Fi itself. There are several competitors in the short distance datatelecommunication area so its not the only standard available.
• The standard is developed by the Wi-Fi Alliance which is basically open to everyone though they have to become a member for an annual fee. Every member has equal rights and can help and influence the development.
• The finished product has enough detail and is available to all who are affiliated while there is still room for each company to change some specifications.
• Free riders problem is not apparent because one has to be a member to get the full details. Within the organization the contribution could be minimal and still get all the documents but an annual fee must be payed anyways. Wi-Fi counterfeiting outside the alliance have no right to get the Wi-Fi certified logo; something which signifies the quality and backwards compatibility.
• Wi-Fi Direct reuses parts of the already successful Wi-Fi standard. Hardware development has matured and scalability has increased to reduce production cost.
• The Internet of Things 'forces' Wi-Fi Direct to be interoperable, something it already has as one of its key features. This will also be key to its success as it is able to bridge the connection between different technologies with an easy setup. This network externality can be seen in its cooperation with ZigBee.
• As Wi-Fi Direct is mainly a software implementation its adoptation level is very easy. Already it is being implemented on thousands of devices although the use of the standard as yet to grow. The standard has started maturing starting in 2014.
• Again, due to a growing need for higher throughputs and the possibility for device-to-device communication gave way as a very good timing for the development of the standard. It still needs to cover some ground as it competes with Bluetooth but has Wi-Fi standards to back up for the interoperability.

Standarisation regime

“If you think of standardization as the best that you know today, but which is to be improved tomorrow; you get somewhere.” - Henry Ford

Since the Wi-Fi Alliance started certifying their product almost 15 years ago, it has become a huge success creating de facto standards in wireless connectivity. Their products already penetrated 25% of homes around the world and since then they have certified more than 18.000 products and sold many millions of devices with their certification. To continue their success it needs to evolve and seek out the next step into their 'seamless connectivity'. With Wi-Fi Direct they hope to gain a share into peer-to-peer networks and expand their domain to short distance setups requiring high bandwidths.

As a company, to be allowed to incorporate Wi-Fi into your manufactured products, one needs to be a Wi-Fi Alliance member. The alliance differentiates two types of memberships: Regular and Adopter. As an regular member you have to pay $15.000 annually, but will gain the full spectrum of benefits. The most important are the ability to certify Wi-Fi products, access working documents, visit annual member meetings, participate in task groups, allowed to vote and access pre-certified technical insight. It means you get to influence the whole process and are the first to be able to implement the knowledge.

The other option is to be an Adopter which cost only $5.000 per year. Your options are limited though as you are not allowed to have any influence in the process of standardisation. Visits to the annual meetings are allowed as are the access to all finished documentation. Also, us of the Wi-Fi Alliance Member logo is allowed but you may not certify product. This way you will get all the benefits finished Wi-Fi standards can provide, but are not able to influence in this process.