Vietnam spectrum occupancy measurements and analysis for cognitive radio applications
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Transcript of Vietnam spectrum occupancy measurements and analysis for cognitive radio applications
Vietnam Spectrum Occupancy
Measurements and Analysis for Cognitive
Radio Applications
Vo Nguyen Quoc Bao
Posts and Telecommunication Institute of Technology
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
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
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
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
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.