Presentation at IEEE WCNC 2014, on a paper about TV White Spaces measurements, plus and analytical model to estimate the probability of having free channels indoors.

1. ScenarioScenario
Spectrum Measurements
-100
-95
-90
-85
-80
-75
-70
-65
21 26 31 36 41 46 51 56 61
dBm
Channel
Roof Intermediate Basement
-100
-95
-90
-85
-80
-75
-70
-65
21 26 31 36 41 46 51 56 61
dBm
Channel
Roof Intermediate Basement
-100
-95
-90
-85
-80
-75
-70
-65
21 26 31 36 41 46 51 56 61
dBm
Channel
Roof Intermediate Basement
Analytical model to study the interference that indoor devicesAnalytical model to study the interference that indoor devices
generate on the DTV receiver. The evaluation of the model is donegenerate on the DTV receiver. The evaluation of the model is done
with extensive Omnet++ simulations.with extensive Omnet++ simulations.
ηJ
i = max∀k∈J (Pik
tx −PL[dJ
ik
]+µ)
ηi = Pi
tx − PL[di
I
]−(nf +1)×α
I K
tot =max∀i∈K (ηi
)+
J∈N
∑ ηI
k
k∈J
∑
Building heightBuilding height
Street size
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 6 11 16 21 26 31 36
Freechannelsratio
λ (meters)
4 buildings
9 buildings
16 buildings
ConclusionConclusion
-Availability of TVWS both indoor and outdoorAvailability of TVWS both indoor and outdoor
-Great availability of indoor TVGSGreat availability of indoor TVGS
- Heavy shadowing leads to low interferenceHeavy shadowing leads to low interference
This work has been made with the support of Telecom Italia and the Italian PRIN project STEM-NET.This work has been made with the support of Telecom Italia and the Italian PRIN project STEM-NET.
Map of Turin with theMap of Turin with the
measurement sitesmeasurement sites
The scarcity of available frequencies is a well known problem for a multitude of services. Several bands have been licensed for a variety of services, and nowadays it is
difficult to find unused spectrum to accomodate new requests.
Cognitive radio networks have been proposed as a possible solution to contrast the experienced spectrum scarcity. One case of particular interest come from the scarce
utilization of TV frequencies, which form the so-called TV White Spaces. After the analog TV switch to digital TV, several channels are often free, and could be utilized by
opportunistic devices. However, in dense populated areas it is not always easy to find unused spectrum.
In this paper, we investigate the utilization of occupied frequencies by secondary devices for short range communication. We conduct spectrum measurements to
quantify the availability of spectrum, and study how short range communications could impact the DTV receiver. We show that these portions of spectrum, called gray
spaces, can be utilized under certain circumstances, for example in highly populated areas, which is the scenario in which it is more difficult to find TV White Spaces.
Simulation studies show the impact grey spaces can have on the available spectrum for opportunistic use.
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 2 3 4 5 6 7 8 9 10
Freechannelsratio
Street size (meters)
4 buildings
9 buildings
16 buildings
PL[dI
i ]=10β log10 (dI
i )+10β log10 ( f )+ Χg
The DTV signal is received as interference (red line) by the indoor device, which produce interference to the DTV receiver while
transmitting (yellow line). It is important that the signal received by the DTV receiver (green line) guarantees a decent SINR.