War of Connectivity: Wi-Fi Direct Vs Bluetooth

November 03, 2011

In the recent years there has been a clear shift in the trends of networking from a wired environment to wireless. There have been several technologies evolving the wireless space to provide a rich user experience and higher bandwidths for peer-to-peer data transmission. Two such promising technologies in the space of peer-to-peer communication are Bluetooth 3.0+ High Speed and Wi-Fi Direct.

Wi-Fi Direct is a new technology and certification from the Wi-Fi Alliance and aims at providing a true peer-to-peer connection between Wi-Fi devices. It is designed to be as simple to set up as a Bluetooth connection. Wi-Fi Direct provides an easy and convenient manner to share, show, print and synchronize content wherever users go – home, public places, travel, work and provides an ecosystem interoperable Wi-Fi devices.

Wi-Fi Direct essentially allows the creation of the software access points by extending the existing Access Point (AP) and Station (STA) client-server architecture with the introduction of a Group Owner (GO), and a Group Client (GC) which can connect in an ad-hoc, peer-to-peer manner. A Group Owner is an “AP like” entity that can set up multiple peer-to-peer links with Group Clients. The same device can optionally be configured to operate simultaneously as an AP and as a legacy device in a Wi-Fi network in case of concurrent connections. A Group Client is a Wi-Fi P2P-compliant device that may connect to a P2P Group Owner.

In addition to the Group Owner/Client functions, Wi-Fi Direct also specifies a Power Saving feature in order to make it suitable for battery-powered devices and Wi-Fi Protected Access 2 (WPA2) has been implemented for providing security protections.

Wi-Fi Peer-to-Peer technology is built on traditional Wi-Fi strengths like performance, security, ease of use and ubiquity, and adds features that optimize it for consumer uses that don’t require access to an infrastructure network.

Bluetooth was designed from the beginning to provide a cheap, low power, peer-to-peer, ad-hoc wireless link between devices. But the traditional Bluetooth radio is incapable of high speed operation, so in Bluetooth 3.0+HS and additional radio has been introduced to act as a “turbo channel” to handle the bursts of data for high speed transmission.

Wi-Fi Direct is being looked upon as a direct competitor to the Bluetooth 3.0+HS. The throughputs of both the technologies are comparable at the PHY layer but there might be slight differences at the application level based on the efficiency of the MAC. Bluetooth has a normal operating range of around 10m whereas the Wi-Fi Direct can operate around the range of 100m. When it comes to power consumption, Bluetooth 3.0+HS might have an upper hand because of its range limitations.

Only a software upgrade is enough to convert a Wi-Fi device to a Wi-Fi Direct one and only one device in a pair of devices needs to have Wi-Fi Direct software installed whereas Bluetooth 3.0+HS would require and alternate PHY/MAC implementation and implementation of Protocol Adaption Layer. Wi-Fi Direct can work on a single radio which can be shared with the existing Wi-Fi but Bluetooth 3.0+HS would require two radios for the complete functionality, which clearly is a handicap.

Wi-Fi Direct certified devices have started making their entry in the commercial space. LG Optimus and Samsung Galaxy S2 smartphones are some of the first mobile devices to be certified with Wi-Fi Direct. Initially Bluetooth HS and Wi-Fi Direct both will exists may be in the same product but in the longer run Wi-Fi Direct might become the best choice for applications that requires high bandwidth and higher transmission rates. Another factor is Bluetooth’s dual-radio approach versus Wi-Fi’s firmware upgrade of existing single-radio hardware which will have a larger pull for the Wi-Fi Direct in the commercial market space.

What do you think Wi-Fi Direct or Bluetooth HS?

- R. Kumaralingam is a Technical Manager - Aerospace & Defense Practice, HCL Technologies Ltd., Chennai.

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