The Science Of TransferJet

TransferJet is a close-proximity wireless transfer technology developed by Sony. A consortium of companies is currently creating standards for the new technology, which allows data to be transferred at speeds of up to 560 Mbps simply by touching the transmitting device directly to the receiving device. TransferJet eliminates complex and troublesome configuration and settings typically associated with conventional wireless technology. For example, simply touching a TV with a digital camera will enable still images to be displayed on the TV screen. Alternatively, downloaded music content can be enjoyed simply by touching a mobile phone to a portable audio player. TransferJet can be thought of as a universal interface that will replace current connectors, cables and memory cards used in many consumer electronics devices.

Your TV responds when you push the button on your remote, and your mobile phone will always connect to a base station when you turn on the power. Everyone from the young to senior citizens can easily use these wireless technologies without thinking. Yet before any wireless system can be used, it is necessary to select the receiving device, and this action requires complex settings.

The aim of TransferJet is to create a simple wireless technology that anyone can use. By reducing the range to less than 3cm, Sony was able to create an intuitive interface that simply requires two devices be brought into contact. This eliminates the need for complex initial setup and configuration with the other devices, such as access points.

As shown in the video, TransferJet enables users to sample music for a specified period and, if they like it, purchase an entire song right there, simply by touching their mobile terminal to the target point on the signage. Because TransferJet has a range of only a few centimeters, there can be different music content offered from multiple target points arranged side-by-side.

The TransferJet Coupler — A New Communications Technology Based on Induction Fields

Instead of a traditional wireless antenna, which employs electromagnetic radiation, Sony has developed a new antenna element designed to work with longitudinal electric induction fields. Known as the “TransferJet Coupler,” it consists of a coupling electrode, a resonant stub, and ground. When a signal is applied to the stub, charge accumulates in the coupling electrode, and a inverse image charge of opposite polarity is generated beneath the ground plane. The ultra-low-power vertical dipole structure formed by these charges is the basis of the TransferJet Coupler system.

Figure 1: Structure and Operating Principle of the TransferJet Coupler Longitudinal Wave Emitted in Forward Direction (Z Axis)
Compared to a conventional antenna, the gain of the TransferJet Coupler is high at short distances but decreases rapidly as distance increases. Because communication takes place only when devices are placed in close proximity (and breaks when they are moved apart), the system is extremely easy for users to understand and operate, and there is no uncertainty about whether or not the wireless connection is working.

Figure 2: Comparison of TransferJet Coupler versus Conventional Antenna
As shown in the graph, gain is high at short distances but decreases rapidly as distance increases.

Reliable High-Speed Communications

With a physical layer transmission rate of 560 Mbps, the TransferJet Coupler can achieve an effective maximum data throughput of 375 Mbps, even allowing for error correction and other protocol overhead. The system is also capable of selecting the optimal transfer rate according to the wireless conditions. When conditions deteriorate, the system can maintain the quality and robustness of the connection by automatically reducing the transmission speed.

Solving Problems Inherent to Close-Proximity Wireless Communication

The TransferJet Coupler can recognize its unique MAC addresses* and other device-specific information. This means that users can control which devices they wish to connect with. By limiting access only to the devices in their homes, users can prevent strangers, such as people in crowded trains, from accessing their data without permission. This feature can also be switched off to allow communications with any device, such as when connecting with other people′s devices while on vacation or at parties.

Ultra-Low-Power Wireless Communications Technology

Sony succeeded in achieving high transmission rates while minimizing transmission power. In fact, the TransferJet system uses only 1/700 as much power as ultra-wide-band (UWB) technology (which has a reputation for low power consumption). It complies with the Japanese standard for low-intensity wireless stations and can be used indoors, outdoors and in vehicles throughout Japan. Also, because TransferJet is an ultra-low-power wireless transfer system designed to operate at close proximities, there is almost no interference with other wireless systems. This means the TransferJet system will not cause problems with wireless LAN or Bluetooth since these operate on different frequencies.

Table 1: Summary of TransferJet Specifications

Future of the Technology

TransferJet wireless technology can be incorporated in a wide range of devices. Sony is promoting the cross-industry adoption of the technology and plans to develop specifications to meet the needs of content providers by creating products and services based on TransferJet, primarily using mobile and handheld devices.

Figure 3: Potential product applications