Ultra wide band radio technology in medical devices (1)

Medical device manufacturers can be used in a variety of wireless applications using UWB technology.

Ultra-Wideband (UWB) is a high-bandwidth (480-1320Mb/sec) and short distance (10-50 m) wireless transmission technology that is gradually in the medical applications of more use.

UWB initially only as a military technology development until 1994 United States military is decrypted only started developing its commercial use. Early UWB chipset is designed to replace mainstream PC USB cable. However, the requirements of the medical application is different, because the transfer real-time video and ultrasonic images require low latency and determine data throughput. Impede the UWB technology using another factor is that the commercial UWB chipset vendors require annual order volume reaches hundreds of thousands more. However, there are already some companies provide for the medical market demand and output of UWB chipset. Medical device manufacturer had begun the UWB technology used for electronic Endoscope, laryngoscopy and Ultrasonic sensors. This article describes how to set the UWB technology applied to electronic endoscope.

The UWB technology for endoscopy of the factors to be considered a flexible endoscopic optics root long thin tubes, they can be imported into the patient.

New endoscopy at the top contains a light source and a small image sensor. Through the use of the new led light source and micro-CMOS camera, this structure is feasible. Endoscopy at the top of the led light source power consumption is much lower than traditional high power light. Therefore, a set of small batteries is sufficient to support the endoscopic work a few hours. In addition, the available copper wires replace expensive optical tube. Another advantage is that the image can be displayed on the LCD, and at the same time is logged. Monitor wireless connectivity eliminates physical limitations, endoscopes makes patient and doctor in the inspection process more comfortable.

Digital transmission is an ideal means of transmission, because it can provide high-definition picture quality and to avoid distortion.

Because the doctor is the video monitor to watch him on the patient's operation, the screen should appear on the screen in real time---in other words, the delay to be as short as possible. Therefore, the video signal cannot be compressed circuit or mass of the protocol stack. UWB, high-bandwidth, low latency, low-radiation and stability makes it the ideal for endoscopy wireless transmission technology.

Ultra wide band radio technology

To NTSC quality transfer uncompressed video need certainty of data transfer rate of at least 166 MB/sec, while the traditional technology didn't approach towards such a data transfer rate.

Traditional wireless technology uses depending on the channel availability of wireless access mechanism. This means that within the reception range of the other device may temporarily reduce the data bandwidth. If using UWB technology, during the session, a channel permanently retained. UWB technology protocol overhead is very low, it is important to reduce transmission delay. By spread your data over 128 sub-carrier can establish a very strong wireless channel. Next will be on UWB technology advantages and details of the other.

UWB wireless communications layer

Early development of UWB based on different physical (PHY) and media access control (MAC) layer specifications.

In the past three years, the WiMedia Alliance of Mac and PHY layer specifications have been most UWB implementers. And has enacted the wireless transmission technology (e.g. WLAN), UWB each transport channel uses 528MHz's band. In contrast, wireless LAN (WLAN) channel maximum bandwidth is 20 MHz. Three of the band to form a 528MHz band group. The entire frequency range of UWB 3.1 ~ 10.6 GHz, is divided into five bands group. Is now working in the band Group 1 and 3 of the advanced dual-band transceiver.

WiMedia-UWB is used by the orthogonal frequency division multiplexing (OFDM) modulation.

Each 528MH band is divided into 128 sub-carrier, each child carrier wave is in adjacent subcarriers of zero position (hence the name ' quadrature ', shown in Figure 1, p. 27). Transmission of information is assigned to the 128 sub-carrier, each 528MHz channel highest rate of 480 Mb/sec.

Since the subcarrier in the larger bandwidth 528MHz, support very low transmit power---37 micro-Watt (in contrast, the emission power WLAN allows more than 300 mW).

For information transfer of broadband and ultra low emission power allows UWB in radio frequency (RF) fields can coexist with other RF. Although transmitting power only 37 micro-Watt, but its transmission distance up to 10 meters, and can pass through a 25 cm thick brick wall without affecting the signal transmission.

Figure 1.

Each WiMedia-UWB 528 MHz band is divided into 128 sub-carrier. Please note that each child carrier wave in its adjacent subcarriers of zero.

Media access control layer

UWB wireless communications layer is responsible for radio frequency (RF) and media access control layer is responsible for the management of UWB wireless communication network and control state.

When the number of UWB devices are very close, they constitute the so-called peer-to-peer networks (ad hoc network). An ad hoc network is not a good network of advance planning, but by the proximity of the participating devices built in equipment may, as appropriate, entry and exit.

As shown in Figure 2 UWB devices on the grounds that the three build a ad-hoc network.

Where equipment is A C on the device is not visible. Located on the left side of the device in the figure A, if not the "listen" to the device C, it is also possible to know the device CThe existence and the amount of time, because A device available through the so-called "beacon" (beacon) to understand device C. Beacon contains adjacent equipment related information and, therefore, the device can understand each other. In each receive information between all the devices, you can carry out any direction of a direct transfer of data.

UWB using TDMA (Time Division Multiple Access, TDMA), in accordance with the time slot and frames to organize the transfer.

UWB transmission time slot combination of Super frame (see Figure 4). Super frame is divided into letter sign section (BP) and data transmission (DTP). Beacons and valid data occupies Super frame 256 media access time slot, a sustained media access time slot, a 256-μ s-frame continuous 65.5ms. All mutual "listens" to the members of the network by listening to the beacon frame synchronization with super. Beacon information can be considered as members of the network of communication channels.

Figure 2.

On an ad hoc network in three UWB device description.