Appendix10.C.UWB Regulations

Appendix 10.C. UWB Regulations

Nathaniel J. August

10.C.1. FCC

In the United States, the FCC released its first report and order for power emissions from UWB devices on February 14, 2002 [80]. This appendix covers the latest revisions as of December 8, 2003 to the United States Code of Federal Regulations, Title 47, Section 15, which allows intentional, low-power radiation from UWB devices [81]. UWB devices provide efficient use of scarce spectrum because they may occupy and coexist with existing narrowband spectra.

The FCC limits the operating bands for a UWB device according to its application. The revision allows for both unlicensed communications applications and licensed applications, such as health monitoring, ground penetrating radar (GPR), and through-walls sensing. The FCC limits on UWB consider the effect of a UWB intruding into the sensitive communications bands located below 2 GHz. Such existing bands include TV, radio, PCS, public safety, and GPS bands. The FCC prohibits UWB communications in toys, aircraft, ships, or satellites.

10.C.1.1 Bandwidth Limits

The FCC defines the bandwidth limitations of a UWB device but does not specify a signal type, such as I-UWB or MC-UWB. The FCC identifies two types of UWB bandwidths: absolute bandwidth or fractional bandwidth, which are defined by the 10 dB cutoff bandwidths in Figure 10.C.1. The absolute bandwidth is the difference between the 10 dB high cutoff frequency and the 10 dB low cutoff frequency (f_hf_l). The fractional bandwidth is defined as 2*(f_hf_l)/(f_h+f_l), and the center frequency is defined as f_c = (f_hf_l)/2. In Figure 10.C.2, the frequency of maximum radiation f_m is the same as f_c, but it need not be. Given these definitions, the FCC classifies a device as UWB if it either has a fractional bandwidth greater than 0.20 * f_c or it has an absolute bandwidth greater than 500 MHz [81].

Figure 10.C.1. FCC UWB Definition.

Figure 10.C.2. Average EIRP Limits for GPR Imaging Devices.

10.C.1.2 EIRP Limits

There are three classes of devices covered by the FCC regulations: imaging systems, vehicular radar systems, and communications and measurement systems. This section briefly reviews the characteristics of each and the EIRP (equivalent isotropically radiated power) limits. The EIRP is equivalent to the signal power level given to the antenna multiplied by the antenna gain. Note that the EIRP can be converted to the field strength at 3 m in dBm V/m by adding 95.2 to the EIRP in dBm. The radiation limits for the three classes of devices are based on interference studies of devices likely to be victims of UWB interference.

Imaging Systems

Some imaging systems are allowed to emit higher power than others because the object they view absorbs most of the radiated power. Note that the band that contains the center frequency and the frequency of maximum EIRP defines the operating band. Regulations for imaging systems are as follows:

GPRA GPR operates mostly in the low frequency band below 960 MHz for sufficient penetration depth, but it can also operate in the 3,10010,600 MHz band. Operation is restricted to construction, law enforcement, fire and rescue, commercial mining, and scientific research. The device is positioned close to the ground and radiation is directed toward the ground. Figure 10.C.2 and Table 10.C.1 show the average EIRP limits for GPR devices. In addition to the average power limits in Figure 10.C.2, a GPR system must also limit average EIRP to 75.3 dBm/kHz in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz. GPR systems require government coordination and individual licensing to ensure acceptable use.
Table 10.C.1. Average EIRP Limits for GPR Imaging Devices.
Frequency (MHz)
Maximum EIRP (dBm)
0-960
41.3
960-1610
65.3
1610-1990
53.3
1990-3100
51.3
3100-10600
41.3
Above 10600
51.3

Through-Walls ImagingA through-walls imaging device may operate in either the low band below 960 MHz or in the mid-frequency band from 1990 MHz to 10600 MHz. Operation is limited to law enforcement and fire and rescue because of the considerable potential for interference. Figure 10.C.3 and Table 10.C.2 show the average EIRP limits for through-walls devices. In addition to the average power limits in Figure 10.C.3, a through-walls imaging system must also limit average EIRP to -75.3 dBm/kHz under low band operation and -56.6 dBm/kHz under mid band operation in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz. Through-walls systems require government coordination and individual licensing to ensure acceptable use.

Figure 10.C.3. Average EIRP Limits for Through-Walls Imaging Devices.

Table 10.C.2. Average EIRP Limits for Through-Walls Imaging Devices.
Frequency (MHz)	Maximum EIRP (dBm) Under 960 MHz Band	Maximum EIRP (dBm) 1990-10600 MHz Band
0960	41.3	41.3
9601610	65.3	46.3
16101990	53.3	41.3
199010600	51.3	41.3
Above 10600	51.3	51.3

Surveillance SystemsA surveillance system provides a security fence around a secure area by detecting and tracking intruders. It operates in the mid frequency band from 1,990 MHz to 10,600 MHz and is for use by law enforcement, fire and rescue, public utilities, and industrial entities. Figure 10.C.4 and Table 10.C.3 show the average EIRP limits for surveillance systems. In addition to the average power limits in Figure 10.C.4, a surveillance system must also limit average EIRP to -63.3 dBm/kHz in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz. Surveillance systems require government coordination and individual licensing to ensure acceptable use.

Figure 10.C.4. Average EIRP Limits for Surveillance System Imaging Devices.

Table 10.C.3. Average EIRP Limits for Surveillance System Imaging Devices.
Frequency (MHz)
Maximum EIRP (dBm)
0960
41.3
9601610
53.3
16101990
51.3
199010600
41.3
Above 10600
51.3
Medical SystemsMedical imaging devices operate in the frequency band from 3,100 MHz to 10,600 MHz. Use is restricted to licensed health care practitioners for the purpose of seeing inside the body of a person or animal. Figure 10.C.5 and Table 10.C.4 show the average EIRP limits for medical imaging systems. In addition to the average power limits in Figure 10.C.5, a medical imaging system must also limit average EIRP to -75.3 dBm/kHz in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz. Medical imaging systems require government coordination, but not individual licensing, to ensure acceptable use.

Figure 10.C.5. Average EIRP Limits for Medical Imaging Devices.

Table 10.C.4. Average EIRP Limits for Medical Imaging Devices.
Frequency (MHz)
Maximum EIRP (dBm)
0960
41.3
9601610
65.3
16101990
53.3
19903100
51.3
310010600
41.3
Above 10600
51.3

Vehicular Radar Systems

Vehicular radar systems are limited to field disturbance sensors in ground vehicles. They occupy the 22 GHz to 29 GHz band with the caveat that the center frequency and the highest radiation level must be above 24.075 GHz. Figure 10.C.6 and Table 10.C.5 show the average EIRP limits for vehicular radar systems. In addition to the average power limits in Figure 10.C.6, a vehicular radar system must also limit average EIRP to -85.3 dBm/kHz in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz. Additionally, vehicular radar systems must attenuate energy above 38 degrees to the horizontal plane by 25 dB with respect to the requirements in Figure 10.C.6. In 2005, the angle reduces to 30 degrees, and in 2014, the attenuation increases to 35 dB.

Figure 10.C.6. Average EIRP Limits for Vehicular Radar.

Table 10.C.5. Average EIRP Limits for Vehicular Radar.
Frequency (MHz)	Maximum EIRP (dBm)
0960	41.3
9601610	75.3
161022000	61.3
2200029000	41.3
2900031000	51.3
Above 31000	61.3

Communications and Measurement Systems

Communications and measurement systems may ship in considerable volume due to their license-free spectrum allocation. Applications include wireless personal area networks (WPANs), sensor networks, precision asset location systems, among the many others listed in Chapter 10. The FCC classifies these devices as either indoor or outdoor devices. Indoor devices should be inoperable when not indoors, e.g. a device could operate on AC power only. Outdoor devices must be handheld devices and must not be supported by an outdoor UWB infrastructure. Further, outdoor devices must stop transmitting when no response is received from a receiver in a 10 second period. These systems operate in the band from 3,100 MHz to 10,600 MHz. Figure 10.C.7 and Table 10.C.6 show the average EIRP limits for both indoor and outdoor communications and measurement systems. In addition to the average power limits in Figure 10.C.7, a communications and measurement system must also limit its average EIRP to 85.3 dBm/kHz in the frequency bands 1,1641,240 MHz and 1,5591,610 MHz.

Figure 10.C.7. Average EIRP Limits for Communications and Measurement Systems.

Table 10.C.6. Average EIRP Limits for Communications and Measurement Systems.
Frequency (MHz)	Maximum EIRP (dBm) Indoor Devices	Maximum EIRP (dBm) Hand-Held Devices
0960	41.3	41.3
9601610	75.3	75.3
16101990	53.3	63.3
19903100	51.3	61.3
310010600	41.3	41.3
Above 10600	51.3	61.3

For emissions under 960 MHz, the average EIRP is measured using the quasi peak detector of the International Special Committee on Radio Interference (CISPR) of the International Electrotechnical Commission, which is explained in CISPR Publication 16. For radiation above 960 MHz, the RMS power is the average EIRP.

10.C.1.3 Peak Power Limits

Note that the previous limits are average power limits and not peak limits. For UWB devices, the peak output does not affect interference levels as much as the average output. However, the FCC does impose a peak limit, as extremely high power pulses can overload the front end of a victim receiver, and spectral lines may appear in sensitive bands. The peak limit restricts emissions at low PRFs (MHz or lower), whereas the average limit restricts emissions at high PRFs (MHz or higher).

For peak power measurements, the FCC considers the peak power across a 50 MHz resolution bandwidth (RBW) to simulate a victim receiver with large bandwidth. The maximum allowable peak in that 50 MHz bandwidth is a 0 dBm EIRP. Because it is difficult to measure EIRP with a 50 MHz RBW, the peak may also be defined by 20 * log (RBW/50 MHz) dBm for any bandwidth from 1 MHz to 50 MHz. The preferred RBW is 3 MHz centered on the frequency of highest emission. The peak power limits apply to all the previously mentioned devices.

10.C.1.4 Unintentional Radiation

Finally, note that digital circuitry in UWB devices also emits unintentional radiation, but this radiation is governed in accordance with Part 15 and not by the previously defined limits.

10.C.2. World

Other parts of the world are currently in the process of defining their own regulatory requirements for UWB systems.

In Europe, the European Telecommunications Standardization Institute (ETSI) has commissioned Task Group 31a to develop standards and conformance-testing requirements. ETSI will provide a spectral mask much like the FCC mask to restrict out-of-band emissions. The European Conference of Postal and Telecommunications Administrations (CEPT) SE24 is dealing with regulatory issues of sharing spectrum under 6 GHz. Also, the International Telecommunication Union Radiocommunication Sector (ITU-R) is preparing recommendations in the ITU-R Task Group 1/8 for Spectrum Management [82]. The ITU recommendations will cover characteristics of UWB, compatibility between UWB and radiocommunication services, spectrum management, and UWB measurement techniques [83].

In Japan, the Ministry of Public Management, Home Affairs, Post, and Telecommunications, (MPHPT) organized a UWB regulatory committee in September 2002, and is in the process of approving a trial license and commercial regulations. The MHPHT is cooperating with the industrial sector represented by the Association of Radio Industries and Businesses (ARIB) [84].

Many other countries, such as Australia, South Korea, China, and Singapore, are beginning standardization efforts of their own [85].