Comparison different technologies
Wi-Fi traditionally has two modes of operations: infrastructure mode for wireless communication for multiple devices connecting to an access point and ad hoc mode for peer-to-peer communication. Ad hoc mode was meant to quickly setup a local network in which each node acted as a router to forward data. This is done dynamically based on the network connectivity. Wi-Fi ad hoc mode has been proven successful in several handheld gameconsoles but had some serious limitation for other applications.
The main drawbacks of the ad hoc mode was firstly a security issue. It was shown that it provided minimal security against attackers within range. Secondly the signal strength monitoring was unavailable in this mode which makes it difficult to keep up a stable network especially when devices are not stationary. Finally the speed is limited to only 11 Mbps. Because of these limitations the Wi-Fi Alliance formed a task group to research Wi-Fi Direct, an optimized Wi-Fi version for peer-to-peer connections.
Bluetooth was originally invented by researchers from Ericsson in 1994. At that time the technology was meant to replace the RS-232 cable with a wireless standard for data communication. Today it has grown to a huge association called the Bluetooth Special Interest Group (SIG) with over 20,000 members. Since its standardization it has been an enormous success being implemented in billions of products ranging from medical equipment and cars to mobile phones and computer peripherals. It operates in the 2.4GHz band, the same as Wi-Fi, and is meant for low power operations with a maximum range of about 100 meter. Their latest implementation is Bluetooth v4.1 which includes all of the previous versions: classic Bluetooth, low power Bluetooth and Bluetooth high speed. Depending on the protocol and class it has a maximum datarate of 24Mbps.
The third major standard for short-range datacommunication is ZigBee which is standardized in 2002 by the ZigBee Alliance, an open non-profit association of members. ZigBee is based on the IEEE 802.15 standard for personal area networks (PANs) working on low energy consumption. According to their website, "ZigBee is the only standards-based wireless technology designed to address the unique needs of low-cost, low-power wireless sensor and control networks in just about any market". Their product focuses on very low power consumption and very low cost. This comes at a price considering the datarates which are limited to only 250kb/s but can have a range up to 100 meters with line-of-sight. ZigBee can be implemented as sensors which share data through each node effectively creating a mesh network without the need for centralized control.
