A Game Theoretic Interference Management Scheme in Full Duplex Cellular Systems under Infeasible QoS Requirements

Round 1

Reviewer 1 Report

This paper uses game theory to improve QoS in a full-duplex channel. 

The usability of this channel for portable wireless devices is questionable as mor power is needed as the network scales. How is this justified? 

What is the complexity of the algorithm? How realistic is its implementation in real-life scenarios?

Author Response

The author would like to thank the reviewer for spending time to read the paper. Below, the reviewer's valuable comments are carefully addressed:

1) The usability of this channel for portable wireless devices is questionable as mor power is needed as the network scales. How is this justified?

Thank you very much for pointing this out. We agree with the reviewer. In fact, comparing Figure 5 and Figure 6, it is observable that as the network size increases, the average transmit power increases as well specially when the required QoS is fairly high. The reason is that as the network scales intercell interference amount increases , which in turn shifts the equilibrium point (the best vector of the transmit powers) into a higher profile. However, in general, each cell are going to be affected mostly by inter-cell interference coming form the cells in the first and second tiers. The proposed scheme was tested up to 36 cells, and the results was fairly good since the proposed scheme tightly controls the transmitted power in every cell.

    As the network grows, the new cells in the farther tiers will have mild effect on the existing cells since their interfering signals will attenuate faster due to pathless. If the network grows further, the gain of full duplex system may diminish and its efficiency will become just like the half duplex one.

    Regarding the effect of self-interference, It has been shown in many references (below are some selected examples [1-4]) that with the advancements in the self-interference cancellation techniques in the three domains; digital, analogue and space, the self-interference could be brought to very low levels, approaching the noise floor.

The above clarification was stated briefly in Section 5  (Simulation results and discussions).

2) What is the complexity of the algorithm? How realistic is its implementation in real-life scenarios?

Thank you so much for the valuable comment. The complexity of the proposed algorithm is proportional to the number of cells  (N). Since base stations are usually equipped with advanced and sophisticated GPUs, the algorithm will be executed at the base stations (BSs) while each user equipment (UE) will act upon commands from its home BS. 

References:

[1] E. Everett, A. Sahai, and A. Sabharwal, \Passive self-interference suppression for full-duplex infrastructure nodes," IEEE Trans. Wireless Commun., vol. 13, pp. 680 {694, Feb. 2014.

[2] T. Riibonen, S. Werner, and R. Wichman, \Mitigation of loopback self-interference in full-duplex memo relays," IEEE Transactions on Signal Processing, vol. 59, pp. 5983 {5993, Dec. 2011.

[3] T. Snow, C. Fulton, and W. J. Chappell, \Transmit-receive duplexing using digital beamforming system to cancel self interference," IEEE Transactions on Microwave Theory and Techniques, vol. 59, pp. 3494 {3503, Dec. 2011.

[4] M. Duarte, A. Sabharwal, V. Aggarwal, R. Jana, K. Ramakrishnan, C. Rice, and N. Shankaranarayanan, \Design and characterization of a full-duplex multi-antenna system for wi networks," IEEE Transactions on Vehicular Technology, vol. 63, pp. 1160 { 1177, March 2014.

Reviewer 2 Report

Overall the paper is well written and the results presented are of interest. My main concern is related to the limited novelty compared to the authors' previously published paper in

International Journal of Computer Networks & Communications (IJCNC) Vol.10, No.5, September 2018, Modelling and QoS-Achieving Solution in full-duplex Cellular Systems

Specifically, both papers are almost identical while the additional content is marginal.

If there are not copyright issues between the two publishers, publication is recommended as the paper is really interesting.

Author Response

The author would like to appreciate the reviewer for his effort in reading and commenting on this paper. The below paragraph addresses his concern regarding the novelty of this paper compared to an earlier published paper: International Journal of Computer Networks & Communications (IJCNC) Vol.10, No.5, September 2018, Modelling and QoS-Achieving Solution in full-duplex Cellular Systems.

    Although both papers' system models look similar, they tackle completely different problems. The earlier paper deals with the case when the set of QoSs is in fact feasible and achievable. First, the SINR was modelled. Then, we proposed a QoS-achieving power control method that is based on the Fixed Point Theorem. On the other hand, this current paper deals with the case of infeasible QoS, that is when the set of QoSs cannot be achieved. Therefore, we proposed the best effort solution for controlling the inter-cell interference based on Game Theory. Therefore, the problems are different and the approaches of the solutions are different as well.

Reviewer 3 Report

The paper present a game theoretic interference cancellations procedure. The paper is well written and presents a timely topic. 

Here is my comments: 

Authors should discuss about overhead of the proposed system. 

How does the performance varies with different QoS requirements? 

Author Response

The author sincerely thanks the reviewer for reading and commenting on the paper. Regarding his comments, they are addressed as follows:

1) Authors should discuss about overhead of the proposed system. 

Thank you for pointing this out. The author agree with the reviewer, and hence the following paragraph has been added to the manuscript, just after describing the algorithm. To make it easier to find the added paragraph is in blue and italic font.

"It is worth mentioning that the proposed algorithm is completely distributed. Thus, each player will act upon local information collected at the BS and its associated UE. Each UE has to send the gain of the desired channel as well as the measured interference to its home BS since all computation should be performed at the BS for powerful computing capability and large memory capacity."

2) How does the performance varies with different QoS requirements? 

Thank you for asking such important question.

 The required QoS (i.e, the minimum required throughput and the maximum allowable BER in both downlink and uplink) was mapped into a pair of target SINR: \Gama^{d}_{n} and \Gama^{u}_{n}. Accordingly, Figure 3 and Figure 4 in pages 9 and 10 illustrate the system energy efficiency under different target SINRs: 8, 27.5, 50, 100. These target SINRs represent different QoS requirements. 

It has been shown in page 10 that as the target SINR (i.e., required QoS) increases, the gain of full duplex schemes  gradually diminishes.