ICs & Semiconductors I Product Focus TransferJet
A touch and transfer revolution
Heiner Tendyck looks at how TransferJet is set to become key to helping users store, view and share digital content across different digital devices
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toring, viewing and sharing content across different electronic devices – computers, tablets, cameras, phones – has become essential for today’s consumers, not to mention a growing number of commercial and industrial users. At the same time, the volume of data that users want to share is increasing. Handling these data volumes, while making the sharing process as easy as possible, is now a fundamental requirement when developing new technology. Modern cameras, camcorders, cell phones, digital video recorders (DVRs), navigation systems, tablets and laptops give users an unprecedented ability to generate and capture content. Computers equipped with the modern equivalent of a recording studio, make us record producers, while the concept of the ‘citizen journalist’ reporting user defined content via smartphone has transformed modern news coverage. As well as producing we remain dedicated consumers of such content. And it has never been easier to watch television, listen to music, or view holiday photos and videos on so many different platforms. But between the action of content generation and content consumption there is a ‘bottleneck’: content transfer, which is the main gating factor on sharing potential. Transferring photos to a widescreen TV, for example, often involves a mess of cables and a maze of menu choices. Devices like smartphones can both generate and play back content: but there is a lack of easy options for direct sharing of files between such products.
TransferJet The TransferJet wireless communications standard aims to fill this gap. It facilitates high-speed peer-to-peer communication between two devices in very close proximity, with extreme ease-of-use and economy of design. The motivation behind the standard is to equip products with a content sharing system that has the simplicity of NFC (near- field communications) and the speed of UWB (ultra wide band). TransferJet is a point-to-point wireless system that works at a centre frequency of 4.48GHz. Transmission distance is restricted to just a few centimetres, so that very little
38 March 2012
transmit power is required: less than - 70dBm/MHz. This in turn enables unlicensed operation in most major global markets, including Japan, Europe, and the US. Its low power also means that it causes virtually no interference to other wireless systems; similarly, there is no interference- related impact to performance when several users simultaneously use TransferJet near each other. The TransferJet standard is administered and developed by a consortium of 53 of the leading players in consumer and industrial electronics markets – Toshiba amongst them. It includes specifications up to and including OSI Layer 5 (the Session Layer) with robust error detection and correction, packet acknowledgement, and packet resend systems. The physical layer transmission rate is 560Mbps, with a maximum payload throughput (when protocol overhead is taken into account) of 375Mbps. This allows the sharing of a one- hour MPEG-coded TV programme in just a few seconds.
Touch is the key The key to the TransferJet user experience is its ‘touch’ model of operation. Because it works over such a short range, the system can safely ‘assume’ that when two TransferJet-equipped products are physically close enough to perform device discovery, it is the user’s intention they should link. No further intervention is required: the action is analogous to inserting a device into a USB socket.
Once the initial TransferJet connection is made, the next steps in communication take place at the application level. These might include automatically transferring a file, prompting the user, or displaying a file menu. TransferJet effectively collapses all of the necessary stages of communication – search, discovery, selection, authentication, connection, and transfer – into a single motion: the ‘touch’.
What’s the alternative? It is tempting to think that, with the proliferation of existing wireless protocols and standards, there must already be a solution for the kind of application that TransferJet addresses. But a closer look
Components in Electronics Figure 1: TransferJet coupling
reveals that none of the available standards actually quite fit the bill. NFC is finely honed for peer-to-peer communication, but is designed to transfer only small data volumes. Similarly, ZigBee delivers relatively low data rates (250kbps), and although simple, is still very much a networking standard, with facilities for quite complex mesh interconnections. Bluetooth shares TransferJet’s peer-to- peer qualities, but was not originally intended for high-speed transfer of large data files; and for security includes a discovery/pairing system that requires user intervention. UWB, though high-speed, is not designed for ease of use, and has failed to deliver on its early promise. IEEE 802.11 is better suited for longer-range communication, and, like ZigBee, is inherently a networking system, with relatively sophisticated integrated security. TransferJet is not going to replace any of these systems – instead it will take its place in an increasingly rich ecosystem of wireless communication possibilities.
The TransferJet standard TransferJet uses the near-field portion of the radio signal. The coupling between the two devices is effectively inductive (see Figure 1), with a number of important consequences. First, the field strength falls off rapidly with distance. Second, energy is ‘stored’ in the electromagnetic field, rather than being radiated – this contributes to TransferJet’s high energy efficiency. Third, the field is not polarised, making the system insensitive to orientation. So the two devices communicating do not need to be ‘lined
up’ or placed in a particular physical configuration, adding to the simplicity of the ‘touch’ interface. The TransferJet protocol itself operates under three basic principles: first, connections are always point-to-point; second, any device can initiate or receive a connection (although data transfer may take place in either direction between initiator and receiver); and the technology should be as compatible as possible with existing architectures. To implement these principles, the
TransferJet protocol defines three layers: The Protocol Conversion Layer (PCL), the Connection Layer (CNL), and the Physical layer (PHY): as we have already observed, these cover the lowest five layers in the standard OSI model.
The PHY implements the actual radio, converting digital information into an RF signal suitable for transmission via the TransferJet couplers. It employs simple π/2 BPSK (binary phase shift keying) modulation, with a concatenated coding method using convolutional codes and Reed-Solomon codes for forward error correction (FEC).
The CNL manages connections and data
delivery. During connection management it is responsible for establishing and releasing the connection to a peer device. For data delivery, it provides packets to carry the data payload and confirm successful delivery of those packets to the peer device. The PCL converts from the device application’s interface standard to the TransferJet native protocol. The TransferJet Consortium decided to support OBEX
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