Department of Electronics & Communication Engineering
Technical Seminar on
VIDYA JYOTI INSTITUTE OF TECHNOLOGY
1. IntroductionTransfer Jet a new Close Proximity Wireless Transfer Technology enabling the high speed transfer of large data files (photos, HD images, etc.) between electronic devices such as mobile phones, digital cameras, digital video cameras, computers and TVs. Using this technology, data can be sent at speeds 10% faster than the international standard version of Ultra Wide Band (UWB) called WiMedia (the basis of Certified Wireless USB). It is a very low power version of UWB operating at 1000 times less power than standard UWB signals, which are already 100 times less than Wi-Fi or Bluetooth. The frequency spectrum they used is at 4.5 GHz, plus or minus about 260 MHz The range of the link is very short, about 1 inch. Essentially Transfer Jet is meant for an almost direct contact between a portable device, such as a digital camera, and a PC or an HDTV, or perhaps between two portable devices. For example, think about a case where you’d touch your cell phone to a photo kiosk. You’d electronically pay for prints through your cell phone and transfer the pictures at the same time. This would occur at high speed so as not to waste your time or test your patience. Transfer Jet is a technology featuring simple operation, safe connection and efficient transfer of data.
2. Features of Transfer Jet
1. "Touch & Get" interface
Just touch two electronic products together and files are transferred automatically. Transfer Jet eliminates the complex setup procedures required by existing wireless systems, and no access point is necessary. Furthermore, users are also able to register their electronic products to enable Transfer Jet to recognize specific products. Operation is also very intuitive, and as there is no host/target relationship, data transfer can take place between mobile phones and PCs for example, as well as between mobile devices.
2. Safe and Flexible
Transfer Jet has the capability of identifying the unique MAC addresses of individual devices, enabling users to choose which devices can establish a connection. By allowing only devices inside the household, for example, one can prevent data theft from strangers while riding a crowded train. If, on the other hand, one wishes to connect the device with any other device at a party, this can be done by simply disabling the filtering function. Transfer Jet uses the same frequency spectrum as UWB, but occupies only a section of this band available as a common worldwide channel. Since the RF power is kept under -70 dBm /MHz, it can operate in the same manner as that of UWB devices equipped with DAA functionality. In addition, this low power level also ensures that there will be no interference to other wireless systems, including other Transfer Jet systems, operating nearby
3. Transfer Jet Coupler
"Transfer Jet Coupler" is based on electric induction field coupling to deliver superior propagation performance compared to conventional radiation field based antennas. It maintains high transmission gain and efficient coupling in near-field proximity, while providing sharp attenuation over longer distances to avoid interference with other wireless systems.
Furthermore, as there is no antenna polarization it is possible to transmit data without any performance loss, regardless of the contact angle of the electronic devices.
4. Stable High Speed Data Transmission
Transfer Jet’s physical layer transmission rate is 560Mbps, and even allowing for error correction and other protocol overhead, the effective maximum throughput is 375Mbps. Transfer Jet will adjust the data rate downward according to the wireless environment, thereby maintaining a robust link even when the surrounding wireless condition fluctuates. As Transfer Jet is a close proximity wireless system which radiates very low-intensity radio waves, it causes almost no interference to other wireless systems, and there is no impact to performance even if multiple users simultaneously multiple Transfer Jet system. Moreover, users of electronic products incorporating Transfer Jet technology are able to transfer data among each other's products regardless of whether they are indoors or outdoors and irrespective of their geographic location.
3. Transfer Jet vs. Bluetooth
In many ways the new Transfer Jet technology is similar to the current Bluetooth standard; however the Transfer Jet system has the advantage of operating at a much higher throughput rate while not having the security concerns that can be found in a Bluetooth connection. For example, with Bluetooth, transfer of data takes place over a range of several feet. Since the signal is not encrypted, it can be intercepted by other Bluetooth devices. A short 3cm transmission distance minimizes any risks of data theft. Unlike Bluetooth and other wireless data transfer protocols, there is no risk of unauthorized access because Transfer Jet can recognize and connect to specific devices only. In addition, the short transmission distance minimizes data leakage without the need for complex security measures or setup procedures. Users can specify and determine restricted access to Transfer Jet capable devices. With no restrictions set, users can exchange data with any Transfer Jet capable device in the office, while traveling, at parties, etc.
Any two consumer devices will be able to exchange data (wireless) with one another simply by holding them close together. The two devices must have the appropriate chip embedded inside. The system is designed for maximum ease of use, which means limited options for controlling the transfers. Devices will transfer their contents automatically to another device within range. Users can "register" devices within the home to keep them from transmitting to "unregistered" devices.
TransferJet uses 4.5GHz electric induction field, instead of radio, as a transmission medium. It's as if an electric field is vertically vibrating between couplers of a transmitter and a receiver. This electric inductive field sharply loses power when it is several centimeters away, which is almost equivalent to 4.5GHz band's wavelength. Accordingly, electromagnetic fields generated by TransferJet transceivers never interfere with other wireless devices. In exactly the same way, unless the field is placed within a distance of several centimeters, TransferJet never gets interference from other UWB wireless devices.
This powerful combination of touch and speed enables high speed transfer of large data files (photos, video, images, etc) between two electronic products such as mobile phones, digital cameras, camcorders, computers, TVs, game products, and printers. Using this technology in its simplest form, data can be sent at high speed with just a single touch. Other cases involving more complex usage scenarios may require additional user interaction to select the specific data to send as well as the location to store (or method to process) the received data. From a user standpoint, Transfer Jet can be thought of as a universal touch-activated interface which instantly connects a wide variety of consumer (and non-consumer) electronic products. For example, a family can display digital photos on their TV just by touching the camera to the TV or Transfer Jet pad connected to a STB. A tourist can archive digital video simply by placing the camcorder close to the PC. And students can share music with friends merely by touching the cell phone to the music player.
Figure 2: Displaying digital photos on the TV by simply touching the camera
The ease of use enhances these traditional use cases but also creates new possibilities. For example, it is possible to create digital signage and digital kiosks. A person might get files such as coupons, movie trailers, and sound clips by touching Transfer Jet pads placed in public locations. A theme park visitor could download electronic maps and event schedules by touching Transfer Jet pads at the park entrance. Additional use cases might exploit the contactless nature of Transfer Jet and thus eliminate the risks associated with traditional connector pins that might corrode, bend, or break. Such properties make Transfer Jet ideal in harsh or demanding environments like manufacturing, shipping, clean rooms, or medical.
Figure 3: Transferring digital files on the go
Figure 4: Downloading digital contents to a mobile device by touching a digital signage spot
Figure 5: Sampling/downloading music files to a mobile device by touching a music kiosk panel
Clearly, the unique qualities of Transfer Jet make it useful for many applications. So let’s delve a little deeper into the technical details of those qualities. Transfer Jet can transfer data at a peak speed of 560 Mbps, with an effective throughput up to 375 Mbps. The maximum range of operation is on the order of a few centimeters. And the network topology is always point-to-point. These last two features greatly enhance the simplicity of the system. The short range makes it possible to operate in the near field of the radio signal using very little transmit power – less than -70 dBm/MHz The point-to-point topology greatly simplifies the network setup and management procedures. And since the near field is a non-polarized field, the two devices do not have to be precisely oriented to achieve a good connection. The spectrum is centered at 4.48 GHz, and occupies a bandwidth of 560 MHz This choice of spectrum, coupled with the extremely low transmit power, enables unlicensed operation in Japan, Europe, the US and other regulatory domains. In addition, Transfer Jet contains a robust protocol which includes error detection and correction, packet acknowledgement, and packet resend. All of these details work together to minimize complexity and interference. The low transmit power and point-to-point topology help to minimize power consumption. Finally, each Transfer Jet device can detect the presence of another device as it comes within range. Therefore, it is possible to save power by transmitting only when another device is detected. This is another advantage of the touch model.
Figure 6: Transfer Jet Specifications
At first glance, the short range of a few centimeters might be considered a disadvantage. But when combined with the touch usage model, it actually offers tremendous advantages. We’ve already mentioned the low power consumption. In addition, the short range virtually eliminates any multipath fading or shadowing present in longer range solutions such as 802.11 or Bluetooth. Thus the connection is very reliable without the need for complex equalizers or advanced signals such as OFDM. This also helps to minimize cost and power consumption. But the biggest advantage is the ability for each Transfer Jet device to discover another Transfer Jet device that comes within range. Since the range is so short, the protocol can reach a key conclusion upon making this discovery: the user has just authorized a connection with the discovered device. Therefore, the protocol can connect the two devices with no further action required from the user. Once this connection is made, the application can take further steps such as transfer a file, query the user, display a file menu, etc. In this sense, the touch motion in the Transfer Jet world is similar to the cable plug-in action in the USB world. One might say that Transfer Jet provides the ease of a USB cable – without the cable. As with every other wireless protocol, devices must proceed through the necessary stages – search, discovery, selection, authentication, connection, and transfer – in order to complete a desired activity. But Transfer Jet is unique because all these steps are collapsed into a single motion: the touch.
Although Transfer Jet is a near field, point-to-point technology, it is still a wireless network. So is it secure? This is a very key question. Wireless networks such as 802.11 and Bluetooth have extensive and complex encryption technology built in to the link layer to make sure that an unauthorized receiver cannot access private information. Such link layer encryption is necessary for long range networks because it is impossible to physically restrict access to the network as would be possible with a cabled solution such as Ethernet or USB. For security purposes, Transfer Jet is more like a physical cable. Therefore, it intentionally has no encryption built into the link layer. It would be very difficult for an attacker to gain access to a Transfer Jet connection from some distant location. The attacker would have to be physically a few centimeters away in order to access the connection. If the attacker has to be that close, couldn’t they just as easily plug in a USB cable? And remember, everything about Transfer Jet is designed to restrict both the signal level and range of the radiated signal. By eliminating link layer security, Transfer Jet saves power and cost, and further reduces complexity for the user. But it is possible to add encryption at the application layer. Some applications must protect a file’s integrity during file transfer regardless of the connection type. Transfer Jet is perfectly compatible with these application-level security measures. Since each device has a unique ID, it is possible to uniquely identify any device that attempts to establish a connection. So Transfer Jet achieves the best of both worlds, the simplicity of touch, with the security of a cable.
9. Protocol StackThe Transfer Jet protocol operates under three basic principles:
1) Point-to-point: Connections are always point-to-point. Multi-point topologies are not supported.
2) Symmetry: All devices are capable of initiating or receiving a connection request.
3) Backwards compatibility: The protocol should be as backwards compatible as possible with existing legacy architectures.
To implement these principles, the Transfer Jet protocol defines three layers: The Protocol Conversion Layer (PCL), the Connection Layer (CNL), and the Physical layer (PHY) as shown in the figure.
Figure 7: Transfer Jet Stack Architecture
The Physical layer, or PHY, implements the actual radio. This layer converts the digital information into an RF signal suitable for transmission across the Transfer Jet couplers. The Connection Layer, or CNL, manages connections and data delivery. For connection management the CNL is responsible for establishing and releasing the connection to a peer Transfer Jet device. For data delivery, the CNL provides packets to carry the data payload and confirm successful delivery of those packets to the peer device. The Protocol Conversion Layer, or PCL, is responsible for converting from an Application’s existing interface standards (such as SCSI or OBEX), and the Transfer Jet native protocol. In this way, for example, a stationary device can access data on a mobile device without modification to the application layer software. There is also a separate Application Management Layer being developed that coordinates and manages the applications, as well as guidelines that define how devices should provide feedback to inform the user of the progress of a transfer operation.
Surprisingly, it is not so easy to restrict operation to such a short range. Remember, if two TransferJet devices are not in contact (or near-contact) with each other, they should do nothing - not even detect each other's presence. That is a very difficult task for a conventional antenna. A typical antenna is designed to radiate a signal as far as possible. To better understand this behavior, consider the field equations shown below for an ideal dipole excited by a sinusoidal current.
Figure 8: TransferJet™ Coupler design and field equations for an ideal dipole.
The variables in the above equations are as follows:
R = range or distance from the dipole in meters
k = angular wave number of a plane wave
p = QL (where Q is the peak charge and L is the length of the dipole)
ω = angular frequency of the sinusoid in radians/sec
ε = permittivity of the propagating medium (air)
μ = permeability of the propagating medium (air) μεω ε μ
Notice the field strength of the far-field parts of the signal vary inversely with range. The near field parts, on the other hand, vary inversely with the square of range. Therefore, the near field intensity drops off much faster with range than the far field. The far field also radiates real power. The far field transverse E and H components form the conventional TEM or Transverse Electro-Magnetic wave so common in wireless communications. By contrast, the near field is inductive because it does not radiate real power but instead stores power in the near field. The inductive power is only dissipated if another TransferJet™ coupler appears in the near field. Finally, the near field contains a longitudinal component. This component is important because it is not polarized, making it much easier for the user to align two devices as previously mentioned. μεω ω ε μ
All these factors are combined to produce the unique TransferJet™ coupler. The design of one such coupler is shown in Figure 7 along with the coordinate system from the ideal dipole analysis. This coupler is not a conventional antenna but instead is designed to suppress the far field component and emphasize the near field signal. The approach creates a virtual bubble of signal energy that drops off very quickly at any range beyond a few centimeters. The result is a usable sensitivity within this distance range. Two typical TransferJet™ devices establish a connection when brought together. But once established, the link will not break unless the devices are separated beyond the bubble distance. This “soft” engage feature further enhances the convenience and ease to the end user.
Since TransferJet™ communicates using a radio signal, it must comply with government regulations in any geographic region in which it operates. In the regions that have clearly established regulations, including Japan, Korea, the EU, and the US, TransferJet™ is compliant for operation indoors or outdoors. The regulatory situation at this writing is shown below.
Figure 9: UWB Regulatory Landscape
Clearly, the technology offers significant benefits to the end user. But any data transfer requires two TransferJet™ devices in order to define a use case and complete a transaction. Therefore, multiple products must adopt TransferJet™ in order for it to be successful in the market. That is the purpose of the TransferJet Consortium (www.transferjet.org/en). As of spring 2009, the consortium consists of the following Promoter companies.
♦ Sony Corporation ("TransferJet Consortium" Administration)
♦ Canon Inc.
♦ CASIO COMPUTER CO.,LTD.
♦ Eastman Kodak Company
♦ Hitachi Ltd.,
♦ JVC KENWOOD Holdings, Inc
♦ KDDI Corporation
♦ NEC Corporation
♦ NIKON CORPORATION
♦ NTT DOCOMO, INC.
♦ Olympus Imaging Corporation
♦ Panasonic Corporation
TransferJet™ is a new wireless technology that combines the speed of UWB (Ultra-Wide Band) with the ease of NFC (Near Field Communications). By doing so, TransferJet™ delivers a transfer speed of 560 Mbps available to the end user through a simple “touch”.
This paper presents a solution – TransferJet™ – which solves the content sharing problem in a way that also achieves high performance, low cost, high security, and most importantly, extreme ease of use.
 Melissa J. Perenson, “New Wireless Standard, Transfer Jet, Gets Big Name Backing at CES”, PC World, January 11, 2009.
 Junko Yoshida, “UWB-based Transfer Jet: the latest go-it-alone technology”, EE Times, January 07, 2008.
 Nate Anderson, “Sony Transfer Jet to take on Bluetooth 3.0”, January 07, 2008.
 Chad Criswell, “Sony's Wireless Transfer Jet Faster than USB Wireless Data Transfer”, January 11, 2008.
 Anuradha Menon, “Touch Me to Transfer Data”, August 21, 2008.