-10 -5 0 5 10 15 20 jamming power (dBm)
-40 -30 -20 -10 0 10 20
SINR at blue team's receiver SINR at red team's receiver
tactical TX power:
{-5, 0, 5, 10, 15} dBm
(a) tune jammer
-10 -5 0 5 10 15 20
jamming power (dBm) -40
-30 -20 -10 0 10 20
SINR at blue team's receiver SINR at red team's receiver
tactical TX power:
{-5, 0, 5, 10, 15} dBm
(b) barrage jammer
Figure 5.1. An illustration of the radio shields’ advantage with (a) 5 MHz and (b) 80 MHz jamming bandwidths when protecting four-carrier GMSK transmission.
By increasing jamming power of the MFR, protective capabilities of such a radio can be improved which provides the desired SINR advantage. For example, by using the lowest tactical transmission power of -5 dBm and the highest jamming power of 20 dBm, the SINR advantage over the opponent is roughly 40 dB. The high jamming power usage results that the own team’s tactical communication signal can be fully covered.
If we consider these observations from the MFR point of view, it would be beneficial of the radio to be capable of automatically tune its transmission and jamming power so that an eligible SINR advantage over the opponent is obtained. This, of course, requires cognitive properties’ implementation for such a radio. However, from a soldier’s perspective, it would be useful if these transmission and jamming powers could be even adjusted manually in the EP mode.
In a full protection mode, where the MFR uses its maximum jamming power, tactical radio’s battery also drains faster. This phenomenon can be solved by the fact that in large tactical operations, involving tens or hundreds of soldiers in a small area; the full protection mode usage is controlled and, hence one soldier uses it at a time. The full protection mode’s usage by single MFR is sufficient to protect the tactical communication also of nearby soldiers in an operational environment when one radio at a time is in the full protection mode. To be capable of transmitting and receiving tactical information inside the radio shield that the full protection mode creates, allied MFRs should support the IBFD technology.
Finally, we look at the situation where an IBFD transceiver and its adaptive jamming is used against an improvised RC system while maintaining the tactical communication link.
The results are illustrated in Fig. 5.2 and for a reference, the corresponding SINRs of tune and barrage jammers can be observed. It should be noted, that in this case the SINRs are plotted against the tactical transmission signal when using different jamming strategies.
-5 0 5 10 15 tactical TX power (dBm)
2 4 6 8 10 12 14 16
barrage jammer (80 MHz jamming signal) adaptive jammer (RC specific jamming signal) tune jammer (5 MHz jamming signal)
max value min value
Figure 5.2. Measured SINRs at the MFR’s IBFD transceiver when different jammers:
tune, barrage, and adaptive jammers are utilized.
Also, minimum, average, and maximum SINRs can be observed. It can be seen that the barrage jammer offers better SINR values compared to a tailored RC specific adaptive jammer. The SINR difference is because it presents more challenging case for the SI cancellation architecture. However, while roughly 2 dB is lost in the tactical link when using the adaptive jammer, the overall jamming power is reduced around 12 dB. Thus, when comparing the adaptive jammer to the tune jammer, the adaptive jammer offers 2 dB larger SINR at the blue team’s IBFD transceiver.
While looking at the situation from the MFR point of view, the use of different jamming modes would be a particular advantage over an opponent. These jamming modes would be beneficial as different types of jamming strategies seek different benefits. For example, the barrage jammer consumes more jamming power, when comparing to the other jamming strategies, but it is powerful if opponent’s frequency band is not known. However, the adaptive jammer consumes less jamming power but does not offer such large SINR at the MFR. Next, we will focus on the result of the MFR utilization for offensive purposes.
Case O
RC: The IBFD Transceiver Utilization Against RC System
Following results are based on the EA functionalities usage in the MFR against an RC system.
These RC systems can be used to activate, for example, explosives from the opponent side.
Figure 5.3 illustrates average power spectral densities of the signals measured in the MFR prototype. Here, transmitted jamming power is set to 18 dBm.
2400 2410 2420 2430 2440 2450 2460 2470 2480 frequency (MHz)
-110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10
power spectral density (dBm / 200 kHz)
no cancellation, RC transmitter in the same laboratory room after cancellation, RC transmitter in the same lab. room after cancellation, RC transmitter in the adjacent corridor
Figure 5.3. The RC transmitter’s power spectral densities after cancellation and without it in the MFR.
A blue curve, where no cancellation is done, shows only jamming signal as it covers the actual RC signal. Also, two different measurement scenarios were done where, at first, the RC transmitter was in the same laboratory room. Hereafter, it was placed farther away to an adjacent corridor. The red curve indicates the first scenario after cancellation. The RC signal is a GFSK modulated and it uses a unique FH pattern where it hops between 16 subbands. Then, in the second experiment scenario, the RC transmitter was placed to the adjacent corridor, and the yellow curve indicates the captured signal after the cancellation.
As it can be seen in this later scenario, the FH pattern can still be effectively detected with the use of cancellation techniques at the MFR. The very same phenomenon can be seen in spectrogram illustrated in Fig 5.4.
Scattered narrowband signals in the spectrogram are RC transmitter’s GFSK frames, whereas wideband signals come from nearby devices connected to a Wi-Fi access point.
Conclusion here is that, by utilizing EA functionalities in the MFR with IBFD capability, the radio is capable of detecting attempts of activating explosive devices in military envi- ronment. The data gathered from the opponent’s transmission can be further used in ES operations for, for example, locating and identifying the transmissions.
2400 2410 2420 2430 2440 2450 2460 2470 2480 frequency (MHz)
0
5
10
15
20
25
time (ms)
-110 -100 -90 -80 -70 -60 -50 -40
power spectral density (dBm / 200 kHz)
Figure 5.4. The spectrogram of the MFR capabilities of detecting frames sent by the RC transmitter.
At finally, Fig. 5.5 shows the measured SINRs for detecting an RC transmitter in the laboratory room and the adjacent corridor. As it can be in the figure, larger jamming powers were measured with a denser grid at 1 dB intervals. It should be mentioned that here each an estimated SINR value is a single representative signal vector. Because of this, a significant random variance between the successive points occurs, particularly above the jamming power of 20 dBm.
It can be clearly seen that below the jamming power of 15 dBm, the detection performance was obviously limited by the background RF interference of the ISM band. The residual SI becomes the primary factor above the jamming power of 20 dBm. In conclusion, the detection of RC transmissions greatly deteriorates when the jamming power is increased.
From the MFR’s perspective, the radio is weak of detecting sent frames when the radio jams with its maximum jamming power. Therefore, one must decide if the MFR is used at a time for ES operations or for EA operations. Anyone will not be surprised that the own team’s and the opponent’s jamming makes it more difficult to identify RC signals.
0 5 10 15 20 25 jamming power (dBm)
-15 -10 -5 0 5 10
SINR (dB)
after digital cancellation, RC transmitter in the same lab. room after analog cancellation, RC transmitter in the same lab. room after digital cancellation, RC transmitter in the adjacent corridor
Figure 5.5. The measured SINR at the input of the experimental MFR where the IBFD transceiver is used for detecting the RC transmissions.
Case O
HD: The IBFD Transceiver Utilization Against HD System
In the second case, the MFR and its EA functionalities are successfully utilized against an opponent’s HD transmission. Figure 5.6 are drawn based on the estimated SINRs at the intercepting blue team’s IBFD transceiver and the red team’s receiver where two different jamming strategies are used.
-10 -5 0 5 10 15 20
jamming power (dBm) -30
-25 -20 -15 -10 -5 0 5 10 15 20 25
SINR at blue team's receiver SINR at red team's receiver
tactical TX power:
{0, 5, 10, 15, 20} dBm
(a) tune jammer
-10 -5 0 5 10 15 20
jamming power (dBm) -30
-25 -20 -15 -10 -5 0 5 10 15 20 25
SINR at blue team's receiver SINR at red team's receiver
tactical TX power {0, 5, 10, 15, 20} dBm
(b) barrage jammer
Figure 5.6. An illustration of the blue team’s intercepting IBFD transceiver’s advantage over the red team when the different jamming strategies are examined. The red team used
a single-carrier GMSK modulated signal for transmitting tactical information.
At first, we look at the potential use of tune jammer with a bandwidth of 3 MHz and its effect on the SINRs at both sides, red and blue. By using measured signal vectors at the red team’s receiver and the intercepting IBFD transceiver, the average SINRs can be plotted as Fig. 5.6(a) illustrates. It can be clearly seen that by increasing jamming power, signal quality of the red team can be effectively degraded, thus making signal decoding more difficult. However, the intercepting IBFD transceiver’s quality can be maintained unchanged regardless of the jamming power. The intercepting IBFD transceiver may force the opponent to use higher transmit power to retain sufficient SINR with the use of a high power jamming signal as it does not seem to have an affect on an interception. Here, the jamming power does not affect an SI cancellation efficiency in the IBFD transceiver.
A practical example of jamming scenario in an MFR might be the situation where the 20 dBm jamming signal is transmitted against an opponent’s receiver from the IBFD transceiver.
The opponent is thus forced to increase its transmission power to decode tactical signal successfully. If the opponent is transmitting with the transmission power of 0 dBm, the SINR advantage,𝑆𝐼𝑁𝑅𝐼𝐵𝐹𝐷− 𝑆𝐼𝑁𝑅𝑇 𝑋, is roughly 44 dB. Afterward, the opponent will likely increase its transmission power, for example, to 20 dBm trying to reduce blue team’s SINR advantage and decode the tactical signal correctly. The power increase reduces the blue team’s SINR lead around 28 dB with the result that power consumption is increased.
0 2 4 6 8 10 12 14 16 18 20
tactical TX power (dBm) 13
14 15 16 17 18 19 20 21
SINR at blue team's receiver (dB)
barrage jammer (80 MHz jamming signal) tune jammer (3 MHz jamming signal)
Figure 5.7. Measured SINRs at the MFR’s IBFD transceiver where tune and the barrage jammers are examined.
Then, we look at the situation where 80 MHz barrage jammer is employed as Fig. 5.6(b) illustrates. Here, the same can be observed as in the case of the tune jammer. When we increase the jamming power, the opponent receiver’s SINR can be significantly reduced while the IBFD transceiver’s SINR remains at the same level regardless of the jamming
power. However, a benefit of the jamming is fully achieved when the power is raised above the 0 dBm. Hence, this is because the barrage jammer is not nearly as efficient as the tune jammer because the power of jamming is decentralized to a broader band. By using, for example, directional antennas to the direction of the opponent receiver, jamming efficiency can be increased.
At finally, we look at the measured SINRs at the MFR’s IBFD transceiver. Figure 5.7 illustrates such a scenario where both jammers, the tune and the barrage jammer, are used.
Similarly, as in Fig. 5.2, minimum, average and maximum values can be observed. As it can be clearly seen, roughly 6 dB difference occurs between these two jammers. The barrage jammer offers better SINRs at the own team’s IBFD transceiver, however, it is not as effective against the red team’s tactical transmission as the tune jammer. Also, when comparing different tactical signals used by the red team, single-carrier and a four carrier GMSK signals, the single-carrier GMSK signal offers all in all higher SINRs at the blue team’s IBFD transceiver. This means that the jamming is more effective against the four-carrier GMSK signal. Also, by using the barrage jammer, it is more likely that the blue team’s tactical information can be successfully decoded. From the MFR’s perspective, it would be essential to have separate jamming functionalities when taking into account previous issues.