LTE Direct
As mobile becomes the new paradigm, there are a variety of wireless devices in our proximity. Today, proximity based applications in different devices face major challenges in finding each other. These include scalability, autonomous discovery, power efficiency and privacy. Qualcomm Research is currently working on addressing these challenges as part of the LTE Direct project
One of the key goals of LTE Direct is to enable the discovery of relevant, proximate applications and peers in an autonomous and battery efficient manner.
LTE Direct is currently being standardized in 3GPP as a Release 12 feature of LTE. It relies on the LTE physical layer to provide a scalable and universal framework for discovery and connecting proximate peers. Qualcomm Research, along with other 3GPP participants is leading the standardization of this feature.
Details
The popularity of mobile apps has really exploded in the last couple of years. Autonomous proximity based applications represent the latest trend in the mobile app space. However these applications have seen limited mainstream adoption.
Today’s proximity based applications are prominently cloud based over the top applications. A server in the cloud matches GPS co-ordinates to determine proximity. Continuous proximity sensing is just not possible with this cloud based paradigm since it implies continuous location tracking and frequent data session setup and tear down. Additionally privacy concerns with continuous user location tracking in the cloud have further limited user adoption of these applications.
LTE Direct is a device to device platform that enables true “continuous” proximity based discovery. LTE Direct devices monitor for service layer announcements (henceforth referred to as expressions) from proximate devices. LTE Direct is a synchronous system operating in licensed spectrum under the control of the operator. The synchronous nature of the system allows devices to stay on for an extremely short duration to announce and monitor these announcements. This results in minimal battery drains enabling truly autonomous proximate discovery.
LTE Direct leverages the LTE licensed framework of LTE to support discovery of 1000s of devices while maintaining the desired application QOS requirements. This scalability is achieved as a result of the broadcast based discovery scheme and the highly efficient over the air expression transmission.
The LTE Direct spectrum resources are assigned by the network and devices use a distributed interference management scheme to determine when to transmit expressions. These resources can be part of either an FDD or a TDD deployment. In the case of an FDD deployment the LTE Direct resources will be assigned via the FDD uplink i.e. LTE Direct devices will transmit and receive expressions on the uplink. The amount of WAN resources for LTE Direct discovery is minimal (<1% of WAN resources) due to the low overhead LTE Direct expressions design. This low overhead design also enables the high scalability and long range discovery (up-to 100s of meters).
Proximity detection in LTE Direct is based purely on the detection of the expression transmission. The ability of LTE Direct to provide proximity discovery without the need to disclose location co-ordinates to the cloud mitigates the privacy concern of todays over the top paradigm.
Finally, in addition to the discovery capability, there is a significant amount of interest in LTE Direct’s device to device communication and discovery capability by the Public Safety community. A key requirement of the first responders is the ability to communicate with each other in a disaster scenario even if the macro network is unavailable.
The distributed traffic scheduling and discovery design of LTE Direct provides the ability for the devices to discover each other and communicate with each other in these Public Safety scenarios where there is no macro network coverage.
