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...  Such technology is moti

Vietnam Spectrum Occupancy Measurements and Analysis for Cognitive

Radio Applications

Vo Nguyen Quoc Bao Posts and Telecommunication Institute of Technology

Outline

 The current spectrum allocation

 Spectrum allocation is static

 Allocation is almost reaching its limit saturation

 The spectrum utilization-ratio is very low

Fixed wireless access

& Satellite service

 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

 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 settings

 Sensing methods

 Energy Detector

 Feature Detector

 Matched filtering and coherent

 We choose energy detector

 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

 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