FULL DUPLEX RADIO WITH ADAPTIVE RECEPTION POWER REDUCTION

Abstract

A full duplex radio unit comprising a transmission unit, an antenna, a reception unit, a circulator and a power reduction unit is provided. The transmission unit is adapted to generate a first signal. The circulator is adapted to provide the first signal from the transmission unit to the antenna. The antenna is adapted to transmit the first signal and simultaneously receive a second signal using an identical frequency or frequency band. The circulator is adapted to provide a third signal to the power reduction unit, wherein the third signal comprises the second signal and interference generated from the first signal by the antenna and the circulator. The power reduction unit is adapted to reduce the power of the third signal by multiplying the third signal by factor of √ρ, wherein ρ is between zero and one, thereby generating a fourth signal.

Claims

1. A full duplex radio unit (2), comprising a transmission unit (3), an antenna (6), a reception unit (4), a circulator (5), and a power reduction unit (14), wherein the transmission unit (3) is adapted to generate a first signal (20), wherein the circulator is adapted to provide the first signal (20) from the transmission unit (3) to the antenna (6), wherein the antenna (6) is adapted to transmit the first signal (20) and simultaneously receive a second signal (21) using an identical frequency or frequency band, wherein the circulator (5) is adapted to provide a third signal (22) to the power reduction unit (14), wherein the third signal (22) comprises the second signal (21) and interference generated from the first signal (20) by the antenna (6) and the circulator (5), wherein the power reduction unit (14) is adapted to reduce the power of the third signal (22) by multiplying the third signal with a factor of √ρ, wherein ρ is between 0 and 1, thereby generating a fourth signal (23), and wherein the reception unit (4) is adapted to receive the fourth signal (23).

2. The full duplex radio unit (2) according to claim 1, wherein the full duplex radio unit (2) comprises an interference cancellation unit (9) adapted to generate at least one interference cancellation signal and to provide the at least one interference cancellation signal to the reception unit (4), and wherein the reception unit (4) is adapted to cancel at least part of the interference by adding the interference cancellation signal to the fourth signal (23) or an intermediate signal derived from the fourth signal (23) by the reception unit (4).

3. The full duplex radio unit (2) according to claim 1, wherein the power reduction unit (14) is adapted to determine and set the factor √ρ depending upon the transmission power of the first signal (20).

4. The full duplex radio unit (2) according to claim 2, wherein the power reduction unit (14) is adapted to determine and set the factor √ρ depending upon a transmission power of the first signal (20) and/or a noise level and/or an interference level within the third signal, so that a pre-set target signal-to-interference-plus-noise-ratio SINR of the fourth signal (23) is reached.

5. The full duplex radio unit (2) according to claim 2, wherein the power reduction unit (14) is adapted to determine and set the factor √ρ such that a signal-to-interference-plus-noise-ratio SINR of the fourth signal (23) is higher than a signal-to-interference-plus-noise-ratio SINR of the third signal (22).

6. The full duplex radio unit (2) according to claim 1, wherein the power reduction unit (14) comprises a signal splitter (31) adapted to split the third signal (22) into the fourth signal (23) and a fifth signal (24), wherein the signal splitter (31) is adapted to split the third signal (22) so that the fourth signal (23) is the third signal (22) multiplied by √ρ and the fifth signal (24) is the third signal (22) multiplied by √(1−ρ).

7. The full duplex radio unit (2) according to claim 6, wherein the power reduction unit (14) comprises an energy harvesting unit (10) adapted to harvest at least part of the energy of the fifth signal (24).

8. The full duplex radio unit (2) according to claim 7, wherein the energy harvesting unit (10) is adapted to at least partially power the full duplex radio unit using the harvested energy of the fifth signal (24).

9. The full duplex radio unit (2) according to claim 7, wherein the full duplex ratio unit (2) comprises a battery (12), wherein the energy harvesting unit (10)is adapted to charge the battery (12) using the harvested energy of the fifth signal (24).

10. A full duplex radio transmission and reception method, comprising: generating a first signal (20) by a transmission unit (3), providing the first signal (20) to an antenna (6) by a circulator (5), transmitting (100; 200) the first signal (20) by the antenna (6), simultaneously receiving (100; 200) a second signal (21) using an identical frequency or frequency band as the first signal (20) by the antenna (6), providing a third signal (22) by the circulator (5), wherein the third signal (22) comprises the second signal (21) and interference generated from the first signal (20) by the antenna (6) and the circulator (5), reducing (101; 201) the power of the third signal (22) by multiplying the third signal (22) with a factor of √ρ, wherein ρ is between 0 and 1, by a power reduction unit (14), thereby generating a fourth signal (23), and receiving the fourth signal (23) by a reception unit (14).

11. The full duplex radio transmission and reception method according to claim 10, comprising: generating at least one interference cancellation signal, and cancelling at least part of the interference by adding the interference cancellation signal to the fourth signal (23) or an intermediate signal derived from the fourth signal (23).

12. The full duplex radio transmission and reception method according to claim 10, wherein ρ is determined and set depending upon a transmission power of the first signal (20).

13. The full duplex radio transmission and reception method according to claim 11, wherein the factor √ρ is determined and set depending upon the transmission power of the first signal (20) and/or a noise level and/or an interference level within the third signal, so that a pre-set target signal-to-noise-and-interference-ratio of the fourth signal (23) is reached.

14. The full duplex radio transmission and reception method according to claim 10, wherein the third signal (22) is split into the fourth signal (23) and a fifth signal (24), wherein the third signal (22) is split so that the fourth signal (23) is the third signal (22) multiplied by √ρ and the fifth signal (24) is the third signal (22) multiplied by √(1−ρ).

15. The full duplex radio transmission and reception method according to claim 14, wherein at least part of the energy of the fifth signal (24) is harvested.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0036] The present invention is in the following explained in detail in relation to embodiments of the invention in reference to the enclosed drawings, in which

[0037] FIG. 1 shows an exemplary full duplex radio unit in a block diagram;

[0038] FIG. 2 shows an embodiment of the inventive full duplex radio unit in a block diagram;

[0039] FIG. 3 shows a detail of the embodiment of the inventive full duplex radio unit in a block diagram;

[0040] FIG. 4 shows a further detail of the embodiment of the first embodiment of the full duplex radio unit in a block diagram;

[0041] FIG. 5 shows different settings for the factor p used in different embodiments of the inventive full duplex radio unit and full duplex radio transmission and reception method;

[0042] FIG. 6 shows a first embodiment of the inventive full duplex radio transmission and reception method, in a flow diagram, and

[0043] FIG. 7 shows a second embodiment of the full duplex radio transmission and reception method in a flow diagram.

DESCRIPTION OF EMBODIMENTS

[0044] In this invention, we propose a solution that can increase both the energy efficiency of the full duplex radio unit 2 and the spectral efficiency of the incoming transmission, which is also referred to as the uplink. In practice, we propose a solution that can tackle both above-mentioned problems at the same time, making profitable use of the presence of an abundance of SI in the RX chain. Considering the case where the transmit power is higher than the value which allows to achieve a complete SI cancellation, with the solution depicted in FIG. 1 it would not be possible to completely remove the SI, thus the overall resulting SINR will be lower, in turn reducing the throughput of the uplink transmission. Accordingly, the full duplex radio unit 2 would operate in a regime in which an increase in the transmit power would increase the achievable downlink rate but significantly decrease the uplink rate. This invention specifically targets this scenario and complements the current technology to improve the energy efficiency of the full duplex transmission, while guaranteeing a good performance in terms of uplink rate.

[0045] First we demonstrate the construction and function of an embodiment of the inventive full duplex radio unit along FIG. 2-FIG. 4. With regard to FIG. 5, the performance gain of embodiments of the present invention is shown. Along FIG. 6 and FIG. 7 different embodiments of the inventive full duplex radio transmission and reception method are described. Similar entities and reference numbers in different figures have been partially omitted.

[0046] In FIG. 2, a full duplex radio unit 2 is depicted. Large parts of the full duplex radio unit 2 of FIG. 2 are identical to the full duplex radio unit 1 of FIG. 1. Especially, the transmission unit 3, the reception unit 4, the circulator 5, the antenna 6 and the interference cancellation unit 9, including the analog interference cancellation unit 7 and the digital interference cancellation unit 8 are identical.

[0047] In addition, the full duplex radio unit 2 of FIG. 2 comprises a power reduction unit 14, which is coupled between the circulator 5 and the reception unit 4. Especially, the power reduction unit 14 comprises an energy harvesting unit 10, and a DC/DC converter 11. The energy harvesting unit 10 is coupled between the circulator 5 and the reception unit 4. An output of the energy harvesting unit 10 is coupled to the DC/DC converter 11.

[0048] Moreover, the full duplex radio unit 2 comprises a battery 12, which is used to power the full duplex radio unit. Energy lines for powering the full duplex radio unit by the battery are omitted here. The battery 12 is connected to the DC/DC converter 11.

[0049] Moreover, the full duplex radio unit 2 comprises a baseband module 13, which is connected to the energy harvesting unit 10 of the power reduction unit 14.

[0050] Further connections of the base band module 13 are omitted here, for reasons of clarity. In practice, the baseband module 13 is connected to the energy harvesting unit 10, since it provides the information about the suitable splitting factor P to achieve the target signal to interference-plus-noise-ratio SINR.

[0051] While in operation, the transmission unit 3 generates a baseband signal and subsequently modulates it as a first RF signal 20 from the baseband signal. The first signal 20 is handed by the circulator 5 to the antenna 6 and transmitted. At the same time, a second signal 21 is received by the antenna 6 and handed to the circulator 5. Within the circulator 5, a third signal 22 is generated from the second signal 21 and interference from the first signal 20. The third signal 22 is handed on to the power reduction unit 14, especially to the energy harvesting unit 10. The energy harvesting unit 10 splits the third signal 22 into a fourth signal 23 and a fifth signal 24. The fourth signal 23 is handed to the reception unit 4, as described earlier. The fifth signal 24 is handed on to the DC/DC converter 11 and converted to usable energy. The battery 12 is than charged using the usable energy provided by the DC/DC converter 11. It is also possible, to directly power the full duplex radio unit 2 using this power.

[0052] The energy harvesting unit 10 splits the third signal 22 into the fourth signal 23 and the fifth signal 24 based upon a splitting factor P. This splitting factor is determined by the baseband module 13 and communicated to the energy harvesting unit 10 based upon a transmission power of the first signal 20 and/or a noise level and/or an interference level within the third signal 23, so that a preset target signal to interference-plus-noise-ratio of the fourth signal 23 is reached. Especially, the factor P is set so that the signal-to-interference-plus-noise ratio of the fourth signal is higher than the signal to interference-plus-noise ratio of the third signal. Thereby, it is possible to cancel out all interference within the fourth signal 23 using the interference cancellation unit 9.

[0053] In order to be able to satisfy the target performance requirements for the system, the energy harvesting unit 10 is advantageously implemented with an adaptive behavior. Accordingly, the baseband module 13 is adapted, to provide an adaptive behavior to the signal splitter and optimize the performance of the energy harvesting unit 10. In order to understand the impact of this feature, let us consider simple non-adaptive choices of ρ such as:

[0054] ρ=0: The entirety of the signal 22 coming from the circulator 5 is harvested, the information rate is completely compromised and the full-duplex radio operates in energy-saving mode.

[0055] ρ=1: The entirety of the signal 22 coming from the circulator 5 is used to decode information. The information rate of the useful transmission depends on the transmit power of the full-duplex radio, which operates in legacy state-of-the-art mode.

[0056] In practice, the aforementioned examples are simple bounds that show what are two extremes in terms of spectral/energy efficiency that the novel architecture can achieve. Naturally, they do not represent the most interesting scenarios. In fact, the baseband module 13 can alter the power splitting factor depending on the transmit power of the full duplex radio and the target performance for the transmission. In this sense, the manufacturer of the device can set different operating policies to achieve dynamic levels of spectral efficiency of the uplink and energy efficiency of the full-duplex radio. Remarkably, the impact of the transmit power on the effectiveness of the SI cancellation is always lower as compared to state-of-the-art solutions, regardless of the choice of the adopted value for ρ, as long as ρ<1.

[0057] As a matter of fact, the adoption of the baseband module 13 renders this approach extremely flexible. In practice, it does not rely upon specific applications to be effective. This solution can be adopted in both pure and hybrid full-duplex scenario, i.e., regardless of how other devices in the network can operate. This implies that this approach is suitable for several possible applications, e.g., smart wireless backhauling solutions, D 2 D communications, M2M communications and so on.

[0058] In FIG. 3, a detail of the embodiment shown in FIG. 2 is shown. Here, the internal workings of the sub-unit 10 of the full duplex radio unit 2, referred to as energy harvesting unit 10, are shown. The sub-unit 10 comprises a signal splitter 31 and a radio frequency-to-DC-converter 32. The power splitter 31 splits the incoming third signal 22 into the fourth signal 23 and the fifth signal 24. The fifth signal 24 is converted to usable energy by the RF-to-DC converter 32. The power splitter 31 is manufactured in an adjustable manner, so that the factor √ρ can be adjusted.

[0059] Moreover, the RF-to-DC converter 32 can also advantageously be adapted to provide an adaptive output voltage, so as to optimally charge the connected battery, for example by making use of an unregulated buck-boost converter operating in discontinuous conduction mode to achieve a constant input resistance. In general, the efficiency of the overall RF-to-DC conversion can be modeled by a factor which is obtained as the ratio of the DC-output power over the RF-input power.

[0060] In FIG. 4, an abstract version of the energy harvesting unit 10 is shown. This figure focuses on the input and output signals of the energy harvesting unit 10. The signal to harvest, which corresponds to the fifth signal 24 is a signal whose power is proportional to 1−ρ. The signal is rectified and subsequently handed to the DC/DC converter 11, 32. The signal to decode, which corresponds to the fourth signal 23 has a power proportional to ρ. This signal 23 is then handed to the reception unit 4 and is also used for interference cancellation by the interference cancellation unit 9.

[0061] Therefore, when the full-duplex radio transmits and receives signals at the same time, and the transmit power is not above the maximum level that guarantees effectiveness of the SI cancellation, the full-duplex system can effectively remove the SI and achieves the expected spectral and energy efficiency. In case though, the transmit power is above the maximum level that guarantees effectiveness of the SI cancellation, the signal coming from the circulator is split into two portions, such that the power of the SI is reduced to meet the condition for the cancellation with state-of-the-art canceller. A signal whose power is proportional to P is fed to the decoder. The spectral-efficiency maximizing ρ can be found and adopted. A signal whose power is proportional to 1−ρ is fed to the energy harvester. The resulting energy-saving full-duplex radio unit 2 does not suffer from the same transmit power limitation as the state-of-the-art devices. Both spectral and energy efficiency enhancements are achieved.

[0062] The advantages of the proposed energy-saving full duplex radio 2 are as follows: [0063] An energy-saving full-duplex radio is able to cope with any transmit power without incurring into excess of SI during the decoding. [0064] Thanks to the energy harvesting unit 10, some of the wasted energy can be collected and re-used, realizing an energy saving. Remarkably, the extent of the saving increases with the transmit power. [0065] No additional power consumption is needed to operate the energy harvesting unit 10 which can be a passive component. [0066] An adaptive choice of P allows to achieve a given target performance in terms of energy/spectral efficiency. [0067] No requirement of a specific scenario to be effective and can be operated in both full-duplex and hybrid half/full-duplex scenarios. [0068] In the context of future networks, e.g., 5G networks, the energy-saving full duplex radio offers an effective solutions to implement full-duplex D2D communications and full-duplex-based in-band wireless backhauling solutions.

[0069] In FIG. 5, an exemplary performance gain for a specific scenario is shown. [0070] Let the transmit power of the full duplex radio unit 2 be 25 dBm and the noise floor being −90 dBm. An exemplary full duplex radio unit 1 as shown in FIG. 1 cannot provide an effective SI cancellation and some residual SI affects the spectral efficiency of the uplink if unmanaged. [0071] Assume an efficiency of the RF-to-DC conversion equal to η=0.5. [0072] The resulting spectral efficiency for a legacy full duplex radio without the proposed invention, i.e., of ρ=1 deterministically, is R=1.4 bps/Hz.

[0073] The achievable spectral efficiency of the uplink for different values of ρ is depicted in FIG. 5.

[0074] It can be clearly seen that: [0075] 1. The choice of ρ significantly affects the performance as expected. [0076] 2. An optimal value for ρ can be found, to maximize the uplink rate. In particular, if we define P.sub.th as the maximum amount of power that allows a perfect SI cancellation with respect to the state-of-the-art full duplex implementation, and P.sub.TOT the overall transmit power of the full duplex radio, then the optimal value of the splitting factor can be found as

[00001]$\stackrel{\_}{\rho }=\frac{P_{\mathrm{th}}}{P_{\mathrm{TOT}}}.$ [0077] 3. The gain with respect to the full duplex radio unit 1 of FIG. 1 can be remarkable, i.e., up to 40% in the considered example. [0078] 4. A non-negligible amount of energy, i.e., more than 20% of the received energy in the considered example, can be processed for harvesting, realizing the energy saving.

[0079] In FIG. 6 a first embodiment of the inventive method is shown. In a first step 100, a first signal is transmitted, while a second signal is received. In a second step 101, the power of a third signal, which comprises the second signal and interference from the first signal is reduced by multiplying it with a factor of √ρ. Thereby a fourth signal is generated. In a third step 102, the power reduced fourth signal is received.

[0080] FIG. 7 shows a second embodiment of the inventive method. In a first step 200, a first signal is transmitted, while a second signal is received. At the same time, a third signal is generated from the received second signal and interference. In a second step 201, a power reduction factor √ρ is determined based upon an RF transmission signal and/or a noise level and/or a interference level of the third signal. In a third step 202, the third signal is split into a fourth signal by multiplying it with √ρ and into a fifth signal by multiplying it with √(1−ρ). In a fourth step 203, an energy harvesting is performed on the fifth signal. In a fifth step 204, the power reduced fourth signal is received.

[0081] Regarding the implementation details of the method it is also referred to the earlier elaborations regarding the device.

[0082] The invention is not limited to the examples. The characteristics of the exemplary embodiments can be used in any combination.

[0083] The invention has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising ” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in usually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless communication systems.