Vietnam Spectrum Occupancy

Measurements and Analysis for Cognitive

Radio Applications

Vo Nguyen Quoc Bao

Posts and Telecommunication Institute of Technology

Outline

Introduction

Measurement and Procedure

Measurement Results and Analysis

Conclusions

Introduction

Radio frequency spectrum is a resource of fundamental

importance in wireless communication systems.

During recent years a multitude of wireless applications

and services has been developed

As a result, the need for new frequency bands increased.

Introduction

Radio Spectrum

Any wireless transmission occupies a portion of the radio

spectrum.

Only the licensed wireless agents are permitted to transmit on

their allocated spectrum band.

The current spectrum allocation

Spectrum allocation is static.

Allocation is almost reaching its limit saturation.

The spectrum utilization-ratio is very low.

Broadcasting (4%) Aeronautical (8%)

Other (2%)

Radar(24%)

Satellite mobile

(5%)

Land mobile (5%)

Fixed wireless access

& Satellite service

(19%)

Fixed access

(13%)

Public mobile radio

(1%)

Military radio

systems (19%)

Introduction

Introduction

Recently, Cognitive Radio (CR) technology has become one of the most rapidly expanding research topics in the field of wireless communication.

dynamically adapt to their environment and combine various information to achieve optimal performance.

currently considered a promising solution for the problem of underutilization of spectrum.

currently considered in some industrial standards:

For example: P1900.4.1 and IEEE 802.21.

Such technology is motivated by measurement campaigns comparing the spectrum regulations defined by governmental agencies and the actual usage by the licensees.

Introduction

Several measurement campaigns concerning spectrum

occupancy have been conducted world wide

In USA (Chicago, New York) [McHenry, 2005]

In Qatar [Qaraqe 2009]

In Singapore [Islam 2008]

In China (Guangdong) [Chen 2009]

In New Zealand [Chiang 2007]

In Spain [López-Benítez 2009]

In Germany [Wellens 2007]

A common finding among

these studies is that

spectrum is indeed heavily

underutilized at the

moment

Introduction

Aim of Measurement

To understand the current spectrum usage due to the fixed

spectrum allocation in Vietnam and its utilization efficiency in

Ho Chi Minh City and Long An province.

To estimate the potential availability of spectral bands for

Cognitive Radio.

To create a first step on studying and designing cognitive radio

wireless networks in Vietnam.

Measurement Locations:

Site: the roof of the building owned by Radio Frequency

Directorate (MIC), An Phu, District 2, Ho Chi Minh City

Coordinate: 10°47'42.3; 106°44'25.9“

Duration: Oct. 2010 - now

North view Aerial map showing the measurement for

measurement location

(Courtesy of Google Inc.)

Measurement Locations

Station: An Phu, District 2, Ho Chi Minh City

Location: 10°47'42.3; 106°44'25.9"

West view East view

Measurement Devices

Antennas:

HE016: active antenna system, omnidirectional reception of vertically and horizontally polarized signals

10 kHz to 80 MHz (vertical)

600 kHz to 40 MHz (horizontal)

HE309: active vertical dipole, high sensitivity, large bandwidth and wide dynamic range from 20MHz to 1300 MHz.

HE314A1: active omnidirectional antenna, reception of horizontally polarized waves from 20 MHz to 500 MHz.

HF214: omnidirectional antenna, designed for the reception of horizontally polarized waves 500 MHz to 1300 MHz

HF902: omnidirectional antenna designed for the reception of vertically and horizontally polarized waves from 1-3 GHz.

Measurement Devices

Receiver: EM550, a fully digitized VHF/ UHF receiver,

covers the frequency range 20 MHz to 3.6 GHz.

Software: R&S®ARGUS Monitoring Software

Measurement settings

Sensing methods

Energy Detector

Feature Detector

Matched filtering and coherent

We choose energy detector Easy to implement

Not require prior knowledge about primary signals.

Energy threshold

ITU recommendation [ITU Handbook Spectrum Monitoring, p. 168]: the threshold should be 10dB above the ambient noise.

The theoretical ambient noise <> the actual ambient noise.

In this work, we set the threshold 3 dB above the minimum received signal power recorded in an observed band during 24h over 4 months.

Measurement results

Remarks

The level of background noise is a little higher than the theoretical ambient noise.

The level of background noise is not constant and slightly increases with frequency resulting in an increase on the decision threshold.

The actual spectrum usage pattern is not uniform, i.e,

the spectrum below 1 GHz seems to be heavily utilized

the spectrum from 2 to 3 GHz is found to be lightly used.

Measurement results

Measurement results

Measurement results

Remarks

This band is the most heavily utilized bands observed in this

study.

The typical maximum signal power of FM bands is from 0 dBm

to -20 dBm.

With TV channels, the maximum power is around -60dBm to -

40 dBm

Measurement results

Measurement results

Measurement results

Remarks The other ones having a considerably higher occupancy rate compared with

other type of frequency allocations. In the land mobile bands, 824-960 MHz and 1710-2300 MHz, it is easy to

identify the spectrum of downlink GSM/E-GSM signals that are located in

950MHz and 1800MHz bands. The spectrum of downlink 3G/IMT2000 signals of four 3G service providers,

i.e. Mobile, Viettel, EVN&HT, and Vinaphone, are observed ranging from

2110Mhz to 2200 MHz. The downlink channels in point-to-multipoint mobile applications are

identified as mostly occupied, e.g. due to the active control channels

constantly broadcasted by base stations to maintain cellular service coverage

of GSM900, GSM1800 and WCDMA networks.

Measurement results

Remarks

Unlike downlink channels always transmitting with relatively high

power, the usages in the uplink channels depend on the actual

number of active mobile users in the measurement area and more

intermittent according to their behaviors. We can see that as expected transmit power of GSM900 mobile

stations is higher than that of GSM1800 mobile stations. We also observe that 3G uplink channels seem to be completely

unused, e.g. due to the nature of WCDMA technology the transmit

power of uplink channels in 3G system is very low, and might not be

detectable by the measurement system.

Measurement results

Measurement results

Remarks

Most part of these bands band is unoccupied suggesting

some opportunities for cognitive radio accesses.

However, recalling that the whole band from 230 to 406

MHz is exclusively reserved for security services and

systems of the Vietnam ministry of public security (MPS).

should be precluded by secondary access

Measurement results

Remarks: The ISM band is considered as the most open band, i.e. many

wireless applications are operated including WiFi transmitters, cordless telephones, microwave ovens, and various consumer products

This band appears to be unoccupied.

It can be explained by the fact that this frequency band is usually occupied in indoor environments and signals at such frequencies are severely attenuated by walls.

Measurement results

The rest of spectrum between 2.4 GHz and 3 GHz

mostly unused, with the exception of some signals with

very low duty cycle in bands allocated to

aeronautical and satellite radiolocation and radionavigation, (960-

1350 and 1610-1710 MHz),

DECT cordless phones (1880-1900 MHz) and

military radars (2700-2900 MHz).

Measurement results

Ho Chi Minh City

Measurement results

Measurement results

Remarks

Some spectrum bands are subjected to exhaustive usage while some others are sparsely used or show temperate utilization, and, in some cases, are not used at all.

In general, the average spectrum occupancy observed in Ho Chi Minh City is 13.74% for the whole frequency range between 20MHz and 3000 MHz and the band assigned for television broadcasting is the highest occupancy band with 58%. Stated another way, 86.25% of this spectrum is unused.

The obtained results demonstrate that Ho Chi Minh City spectrum utilization exceeds Long An by roughly 1.46%, which, in turns, exceeds New Yorks by 1.15%.

Future Work

A part of a larger on-going measurement campaign conducted by PTIT in several cities in the south of Vietnam.

The purpose of this project is to create a usage map for cognitive applications.

Our measurement results suggest that in Vietnam

Most of allocated frequencies are underutilized except for mobile and broadcasting bands

CR applications can be realized by exploiting bands with low measured occupancy rates.

However, care must be taken to account for possible wireless channel effects such as multi-path and hidden terminal problems.