# Presentation: 150920

## 
Spectrum Policy Task Force

Technology Advisory Council (TAC) Briefing

December 2002

**Spectrum Policy Task Force**
**Technology Advisory Council (TAC) Briefing**
- December 2002

- www.fcc.gov/sptf

## Outline

-  Interference Temperature
-  Spectrum Access

- www.fcc.gov/sptf

##  Interference AvoidanceRecommended Methods of Interference Control

- Adopt a more _quantitative approach_ to interference management based on the concept of “interference temperature.”
- _Interference temperature_ metric would establish maximum permissible levels of interference, characterizing the “worst case” environment in which a receiver would be expected to operate.
- Different threshold levels could be set for each band, geographic region or service -- set only after _review of the condition of the RF environment_ in each band.
**systematic study of the RF noise floor necessary**
- _Receiver performance requirements_ for some bands and services, through incentives, mandates, or some combination of incentives and mandates.

- www.fcc.gov/sptf

##  Interference Avoidance

-  **Interference Avoidance**

***It doesn’t matter what the signal level is here!***

***It matters what the signal level is here!***

**Interference**
**Temperature**

**Define “interference temperature” – total RF energy from both ambient noise and other sources**

- www.fcc.gov/sptf

**Notes:**
One recurring and often thorny issue is how to protect users against harmful interference.  Despite the fact that the Commission has had extensive, and generally successful, experience in managing interference issues, these issues have been increasing in technical difficulty and prevalence due to the changing RF environment generated by new devices and new technology. The rules should specify a more accurate measure of interference that takes into account the cumulative summation of all the undesired RF energy available to be captured by a particular receiving antenna for delivery to the receiver.  To achieve this objective, as well as to transition interference management to more accurate real-time measurements, the Task Force recommends that the Commission adopt a new metric, “interference temperature,” to quantify and manage interference.  The interference temperature measures the RF power available at the receiving antenna per unit bandwidth.  
Conceptually, as illustrated this figure, interference temperature measurements would be taken at various receiver locations to estimate the real-time condition of the RF environment.  The degree of certainty of the estimate of the environment would depend on such factors as transmitter signal ranges, uniformity of signal levels over an area, the density of temperature measuring devices and the sharing of the data taken by nearby devices; e.g., through “ad hoc cooperative wireless networks.” The Commission could use the interference temperature metric to establish maximum permissible levels of interference, thus characterizing the “worst case” environment in which a receiver would be expected to operate.  Different threshold levels could be set for each band, geographic region or service, and these thresholds should be set after the Commission has reviewed the condition of the RF environment in each band.

## License Holders Design System to Operate down to the Noise Floor
Any additional interfering signals (including aggregation of unlicensed devices) can cause degradation

**Distance from licensed transmitting antenna**

**Power at Receiver**

**Licensed signal**

**Current Part 15 Limits**

**License Holders Design System to Operate down to the Noise Floor**
**Any additional interfering signals (including aggregation of unlicensed devices) can cause degradation**

**Design to Original Noise Floor**

**Noise Floor**

**Aggregated Signals Reducing Coverage**

- www.fcc.gov/sptf

**Notes:**
The Commission’s review of the RF environment should include actual spectrum measurements of the RF noise/interference floor.  In addition to obtaining better data regarding the noise floor, the Commission should adopt a standard methodology for measuring the noise floor.  Further, the Task Force recommends that the Commission create a public/private partnership for a long-term noise (interference temperature) monitoring network and for the archiving of data, for use by the FCC and the public.
This figure depicts a possible scenario resulting from the current open ended nature of the RF noise floor.  A communications system has been designed to operate to a distance from the transmitting antenna at which the signal strength approaches the level of the noise floor that existed when the system was established.  Over time, the noise floor can rise unpredictably – this due to additional interfering signals, perhaps including out-of-band emissions from new users and further aggregation of unlicensed devices.  As a result, signal coverage can be degraded without warning.  Additional interfering signals will progressively worsen coverage.

## Quantify acceptable levels of interference
More Certainty for Licensees
More Opportunity for Consumer Devices

**Distance from licensed transmitting antenna**

**Power at Receiver**

**Licensed signal**

**Current Part 15 Limits**

**Quantify acceptable levels of interference**
**More Certainty for Licensees**
**More Opportunity for Consumer Devices**

**New Opportunities for Spectrum Access**

**Noise Floor**

**Prevent Aggregation Above Interference Temperature Limit**

- www.fcc.gov/sptf

**Notes:**
This figure modifies the scenario by placing an interference temperature cap over the service area. Two key benefits will result from the application of the interference temperature metric:  First, licensed spectrum users will obtain certainty with regard to the maximum permissible level of aggregated noise, or interference, in their band.  The interference temperature would quantify the level of acceptable interference in a particular band.  For example, any transmissions from other sources that increase the noise level above the interference temperature would be considered “harmful interference” in accordance with Commission rules.  Second, to the extent that the interference temperature in a particular band is not reached, other users (e.g., unlicensed devices) could operate in the same band – with the interference temperature serving as the maximum cap on the potential RF energy they could introduce in the band.  This would thus increase access to the band for other users or devices.
Interference temperature sensory and control mechanisms could be used to maintain both in-band and out-of-band emissions within permissible limits.  For example, a low power unlicensed RF device could be designed to scan its particular frequency band before transmitting.  Its built-in “thermometer” would record interference temperature data and compute the appropriate statistical aggregate value.  The device would then project the increase in interference temperature due to its operation over its nominal range.  This value would be compared with the permissible limit.  If its operation would exceed the limit, the device’s controller could execute an appropriate response such as reducing power, switching to a different transmit frequency (if available) or, perhaps, continuing the scanning/sensing process to locate an opportune time to transmit.  The technology now exists to build such sensory control systems.  Automated transmitter power control, for instance, is used in certain types of wireless and satellite communications systems.  Cordless telephones also adapt to the environment by selecting an unused frequency.

## Interference TemperatureTypical Technology Questions

- Measurement Methodology
- Standardization of techniques used to report noise floor
- Resolution – Space, Time, Frequency, Amplitude
- Reporting Format
- Utilization of Private and Government Measurements
- Monitoring Stations versus In-Situ Devices
- Measurements available to the network, or individual devices share measurements, or both
- Measurements versus Modeling versus In-Situ Modeling

- www.fcc.gov/sptf

## Outline

-   Interference Temperature
-  Spectrum Access

- www.fcc.gov/sptf

## Spectrum EfficiencySpectrum Utilization

**Spectrum Efficiency**Spectrum Utilization

**Heavy Use**

**Sparse Use**

**Heavy Use**

**Medium Use**

- www.fcc.gov/sptf

## State of the Spectrum?

- Access versus Scarcity

**Time**

**Frequency**

- www.fcc.gov/sptf

## Spectrum Policy Reform: The Time is Now

- Increased _access_ can mitigate scarcity of spectrum resource
- Most “prime spectrum” has already been assigned to one or more parties, and it is becoming increasingly difficult to find spectrum that can be made available either for new services or to expand existing ones.
- Improving access to the spectrum can be achieved through permitting licensees greater flexibility and other means.

- www.fcc.gov/sptf

## Promoting Access to Spectrum

- Designate additional bands for unlicensed spectrum use
- better optimize spectrum access and provide room for expansion in the fast-growing market for unlicensed devices and networks
- In licensed spectrum bands, pursue secondary markets policies that encourage licensees to provide access for “opportunistic” uses above the interference temperature threshold through leasing of spectrum usage rights.
- Explore the possible granting of “easements” for some opportunistic uses in new spectrum bands, but be sensitive to the potential impact on planning and investment by licensed users.

- www.fcc.gov/sptf

## Promoting Access to SpectrumPart of Maximizing Spectrum Efficiency

**Group**
**like systems**

**Permit other****users or uses --**
_**flexibility**_

**Improve access****through time, ****frequency,****bandwidth****and space**

**Throughput Limited**

**Access Limited**

**Adjust regulations****as technology ****develops**

**Currently spectrum is access limited **
**Eventually spectrum may be throughput limited -- not there yet**

**Promoting Access to Spectrum****Part of Maximizing Spectrum Efficiency**

**Discourage****inefficient use**

- www.fcc.gov/sptf

## Promoting Access to Spectrum The New Model

**Below the Acceptable **
**“****Interference Temperature”**

- www.fcc.gov/sptf

## Promoting Access to SpectrumIn the Space Dimension

- Rural
- Environs

**Promoting Access to Spectrum****In the Space Dimension**

- www.fcc.gov/sptf

## Promoting Access to Spectrum In the Time and Space Dimensions

**Promoting Access to Spectrum ****In the Time **_**and**_** Space Dimensions**

- www.fcc.gov/sptf

## Promoting Access to SpectrumThrough Increased FlexibilityIllustration: Public Safety & Dynamic Spectrum Use

**CMRS**

**Public Safety**

**Data Services**

**Data Services**

**Public Safety**

**CMRS**

**1%**

**10%**

**100%**

**10%**

**1%**

**Use of public safety spectrum is highly variable**

- www.fcc.gov/sptf

##  Promoting Access to Spectrum 

- In rural areas
- flexible regulation of power levels
- secondary markets mechanisms to encourage leasing of spectrum usage rights
- in defining geographic licensing areas
- Experimental spectrum uses encouraged (promote innovation)
- improve experimental licensing frequency coordination process
- dissemination of more information identifying bands suitable for experimental applications

- www.fcc.gov/sptf

## Promoting Access to SpectrumDiscouraging Inefficient Use

- Situations where the Commission finds it necessary to promote spectrum or technical efficiency
- Consider _user fees_ or other steps to stimulate improvements in efficiency when marketplace is inadequate.
- To the extent that wireline or hybrid technologies may be more efficient alternatives to existing use of radio spectrum in some instances, promote the use of such alternatives whenever appropriate.

- www.fcc.gov/sptf

## Spectrum AccessTypical Technology Questions

- Viability of Dynamic Sharing
- Frequency agile devices
- Cost effective spectrum Sharing
- QoS constraints
- Microcharging technology
- Distributed versus Centralized Control
- Flexibility versus Robustness
- MAC Protocols
- Overhead, stability, robustness

- www.fcc.gov/sptf

**Thanks!**

- www.fcc.gov/sptf