IEEE 802.11af
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2013-12-07
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IEEE 802.11af: A Standard for TV White Space
Spectrum Sharing
Adriana B. Flores, Ryan E. Guerra and Edward W. Knightly
Electrical and Computer Engineering
Rice University
Houston, TX
{a.flores, war, knightly}@rice.edu
Peter Ecclesine and Santosh Pandey
Corporate Development Technology Group
Cisco Systems
San Jose, CA
{pecclesi, sanpande}@cisco.com
Abstract—Spectrum today is allocated in frequency blocks that serve
either licensed or unlicensed services. This static spectrum allocation
has limited resources to support the exponential increase in wireless
devices. In this article, we present the IEEE 802.11af standard that
defines international specifications for spectrum sharing among
unlicensed white space devices (WSDs) and licensed services in the
TV White Space (TVWS) band. Spectrum sharing is conducted
through the regulation of unlicensed WSDs by a geolocation
database (GDB), whose implementation differs among regulatory
domains. The main difference between regulatory domains is the time
scale with which WSDs are controlled by the GDB, resulting in
different TVWS availability and WSD operating parameters. The
IEEE 802.11af standard provides a common operating architecture
and mechanisms for WSDs to satisfy multiple regulatory domains.
This standard opens a new approach to treat spectrum as a single
entity shared seamlessly by heterogeneous services.
Keywords— IEEE 802.11af, TV white spaces, TV white space
band, Spectrum Sharing, Geolocation Database.
I. INTRODUCTION
White Spaces are unused spectrum resources at specific
times and locations that can be exploited through spectrum
sharing. TV white spaces (TVWS) exist in the broadcast TV
operating frequencies known as the VHF/UHF band,
specifically ranging from 470 MHz - 790 MHz in Europe [1, 2]
and non-continuous 54 MHz - 698 MHz in the United States
[3]. The existence of TVWSs enables spectrum sharing among
unlicensed white space devices (WSDs) and licensed protected
users of the TVWS band. The TVWS band is currently used by
a large variety of licensed protected services, such as
Terrestrial TV broadcast services and Program Making and
Special Event (PMSE) users. Some of the licensed services
have resided in this band for nearly 100 years [4]. Licensing
protects the incumbent users of the TVWS band from
interference within their service area. Therefore, WSDs
operating in the TVWS band are not permitted to interfere with
any protected incumbent user in their specified operating area.
Propagation characteristics of the TVWS band make it a
desirable and convenient spectrum for many wireless
transmission services [5]. First, because this band resides under
the 1 GHz frequency, material obstruction is less harmful than
at higher frequencies, allowing non-line of sight coverage [6].
The difference in signal attenuation between a variety of
materials and frequencies is shown in Table 1 [7], where
differences of up to 50 dB are found between 570 MHz and 5.7
GHz. Second, the TVWS band presents a path-loss advantage
over unlicensed ISM bands (2.4 GHz and 5.7 GHz) due only to
operating frequency. For example, TV channel 2 (54-60 MHz)
has 20 dB less path-loss than TV channel 30 (566-572 MHz),
which itself holds a 20 dB gain over the unlicensed band at 5.7
GHz.
Table 1. Received Signal Magnitude gain in dB (0.0 dB = No attenuation) [7].
The superior propagation factors of the TVWS band are
demonstrated in Fig. 1. The capacity and distance components
are compared for low transmission-power TVWS mobile
devices, 2.4 GHz devices and 5.5 GHz devices, as well as high
power TVWS-fixed devices. Wider channels in the high
frequency bands, such as the 80 MHz channels used in the 5
GHz ISM band, provide higher capacity over a short range, but
require more infrastructure to achieve wide-area coverage. In
contrast, the 6 MHz-wide, 4 Watt white space signal is more
robust and propagates longer distances with a significant
capacity. The calculations for Fig. 1 assume free-space
propagation using the Friis Transmission Equation [8] in order
to demonstrate relative performance with characteristic system
parameters.
The excellent propagation characteristics of the TVWS
band coupled with underutilization in many locations presents
desirable potential spectrum sharing opportunities. To achieve
sharing among WSDs and licensed TV broadcasters and PMSE
Materials
0.57 GHz
(dB)
1 GHz
(dB)
2 GHz
(dB)
5.7 GHz
(dB)
0.57 to
5.7GHz
(∆dB)
Brick 89 mm
-1.5 -3.5 -5.4 -15 13.5
Brick 267 mm
-4.8 -7 -10.5 -38 33.2
Composite Brick 90mm/
Concrete Wall 102mm
-12 -14 -18 -42 30
Composite Brick 90mm/
Concrete Wall 203mm
-21.5 -25 -33 -71.5 50
Masonry 203mm
-9.5 -11.5 -11 -12.75 3.25
Masonry 610mm
-26.5 -27.5 -30 -46.5 20
Glass 6mm
-0.4 -0.8 -1.4 -1.1 0.7
Glass 19mm
-2.5 -3.1 -3.9 -0.4 -2.1
Plywood (Dry) 6mm
-0.15 -0.49 -0.9 -0.1 -0.05
Plywood (Dry) 32mm
-0.85 -1.4 -2 -0.9 0.05
Reinforced Concrete
203mm/ 1% steel
-23.5 -27.5 -31 -56.5 33
Reinforced Concrete
203mm/ 2% steel
-27.5 -30 -36.5 -60 32.5
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资源评论
YVONNE_NO12019-09-11还没看，正在研究- violent742014-07-03这个资料一般，只有比较简单的对信道特性的描述，建议下载drife5.0的规范文档
haopf2014-06-05标题党，这个一般性介绍，内容太少
