WiFi works in two different modes. Most people are familiar with what is known as Infrastructure Mode that requires an access point or “hot spot”. However, WiFi can also work in WiFi Direct mode, which is a peer-to-peer (device to device) method of communications. WiFi Direct provides a method for close-range device-to-device communication.
Wi-Fi Direct is ostensibly viewed to be a competing technology to LTE Direct. Wi-Fi Direct has the virtue of connecting devices without using a Wi-Fi access point. Other important features of Wi-Fi Direct include WPA2 security and controlled access protocols. Wi-Fi Direct can be used to connect one-to-one or one-to-many devices. Wi-Fi Direct can support data rates of 250mbps in 802.11n or 54mbps in 802.11a/g protocols. But in terms of local-area networking Wi-Fi Direct and LTE Direct are very complementary.
A method that in some ways is similar to WiFi Direct for device-to-device communication has been developed for LTE handsets called “LTE Direct” (LTE-D). Instead of transmitting messages to a macro network and then having messages sent back to devices through the mobile network, LTE-D provides for the ability of device-to-device (D2D) communications. LTE Direct can also mean an LTE broadcast where a one-to-many message can be sent directly to LTE capable devices without the use of the larger macro network.
Quite a few companies believe Direct LTE will offer capabilities and power efficiency for location-based applications not available with today’s Wi-Fi Direct and GPS links. Some of these companies include Qualcomm, Alcatel-Lucent, Deutsche Telekom, LG, NEC and Nokia.
Qualcomm is promoting direct services through a peer-to-peer cellular technology as a new standard called LTE Direct, which in many ways will make presence and location-based services faster and more efficient.
The LTE proposal was developed by Qualcomm in its own labs and allows two cellular devices to communicate over the air without relying on a fixed network infrastructure. LTE Direct eliminates steps in the location process, allowing devices to find services or users more quickly. Direct Services can be used for ongoing communication at high speeds, including streaming video, while conducting Device to Device Peer Discovery (“discovery mode”) Direct Services would only broadcast tiny 128-bit packages of data. Those packages, called “expressions,” would contain basic information about the device or user. Each LTE Direct device would look for expressions nearby, choosing among them using filters customized for the user or for specific applications.
Under LTE Direct, Direct Devices would regularly broadcast expressions advertising what services are being offered. Other direct devices and services in range can receive those expressions and if a device detects a service that it wants to use, that application can then go into action, responding to the requestor. For example, if two friends have devices that are sending out expressions announcing a social-networking app that both of them use, and then each friend will receive a notification that the other friend is nearby.
LTE Direct uses line-of-sight links at ranges up to 500m with less processing overhead than Wi-Fi Direct Internal Qualcomm tests showed that LTE Direct could discover more compatible devices in a much shorter timer than Wi-Fi Direct. Their tests also found latency for Wi-Fi Direct discovery degraded significantly as device density increased, in contrast to LTE Direct.
While LTE Direct clearly provides some competition for Wi-Fi Direct in the peer-to-peer arena, it is likely that both will find a way to coexist. They each have their own advantages, LTE Direct for discovery and Wi-Fi Direct not being limited by line-of-sight constraints. LTE Direct might be used for more quickly discovering neighboring devices and Wi-Fi Direct for the transfer of data.