[Paper Review] Secrecy in the 2-User Symmetric Deterministic Interference Channel with Transmitter Cooperation

Parthajit Mohapatra, Chandra R. Murthy|NOT FOUND REPOSITORY (Indian Institute of Science Bangalore)|Jan 28, 2013

Wireless Communication Security Techniques12 references4 citations

TL;DR

This paper proposes a novel transmission scheme for the 2-user symmetric deterministic interference channel with limited-rate transmitter cooperation and secrecy constraints, combining interference cancellation, relaying of the other user's data, random bit transmission, and time sharing. The key result is that in certain interference regimes—particularly weak interference and when cooperation is strong—secrecy can be achieved at the same rate as the non-secret capacity, enabling 'secure communication for free.'

ABSTRACT

This work presents novel achievable schemes for the 2-user symmetric linear deterministic interference channel with limited-rate transmitter cooperation and perfect secrecy constraints at the receivers. The proposed achievable scheme consists of a combination of interference cancelation, relaying of the other user's data bits, time sharing, and transmission of random bits, depending on the rate of the cooperative link and the relative strengths of the signal and the interference. The results show, for example, that the proposed scheme achieves the same rate as the capacity without the secrecy constraints, in the initial part of the weak interference regime. Also, sharing random bits through the cooperative link can achieve a higher secrecy rate compared to sharing data bits, in the very high interference regime. The results highlight the importance of limited transmitter cooperation in facilitating secure communications over 2-user interference channels.

Motivation & Objective

• To address the challenge of achieving secure communication in a 2-user symmetric deterministic interference channel where receivers must remain ignorant of the other user's message.
• To investigate how limited-rate transmitter cooperation can enhance both spectral efficiency and physical layer security in interference-limited wireless networks.
• To design transmission schemes that adapt to varying interference levels (characterized by α = log(INR)/log(SNR)) and cooperative link rates (C).
• To determine whether cooperation enables secrecy rates matching the non-secret capacity, particularly in high-interference regimes.
• To explore the relative performance of sharing data bits versus random bits over the cooperative link in securing communication.

Proposed method

• The scheme uses a deterministic interference channel model where signal and interference levels are represented by integers m and n, with α = n/m.
• In the weak interference regime (0 < α ≤ 2/3), the scheme employs precoding of own data with cooperative bits to cancel interference and ensure secrecy.
• In the moderate interference regime (2/3 < α < 1), the scheme combines interference cancellation with transmission of random bits to enhance secrecy, especially when C is small.
• In the high interference regime (1 < α < 2), the scheme relays the other user’s data bits via the cooperative link, along with interference cancellation and random bit transmission.
• In the very high interference regime (α ≥ 2), time sharing is used in conjunction with relaying and random bit transmission, with random bit sharing outperforming data-only sharing for low C.
• The achievable secrecy rate is derived based on the cooperative link capacity C and the interference-to-signal ratio α, with performance evaluated across multiple m and n values.

Experimental results

Research questions

• RQ1 Can limited transmitter cooperation enable secure communication in a 2-user symmetric deterministic interference channel without sacrificing spectral efficiency?
• RQ2 How does the relative strength of interference (α) affect the design and performance of secrecy-achieving transmission schemes?
• RQ3 Under what conditions does sharing random bits over the cooperative link outperform sharing only data bits in enhancing secrecy?
• RQ4 Is it possible to achieve the same secrecy rate as the non-secret capacity of the channel, and if so, under what conditions?
• RQ5 What is the role of time sharing and relaying in maintaining nonzero secrecy rates in the very high interference regime (α ≥ 2) with limited cooperation?

Key findings

• In the weak interference regime (0 < α ≤ 2/3), the proposed scheme achieves the same secrecy rate as the non-secret capacity for all cooperative link rates C.
• For m = 4 and n = 2 (α = 0.5), the scheme achieves the non-secret capacity for all C, demonstrating that secrecy can be achieved at no rate cost.
• In the moderate interference regime (2/3 < α < 1), random bit transmission enables nonzero secrecy rates even when C is small, outperforming schemes relying only on data relaying.
• In the very high interference regime (α ≥ 2), sharing random bits through the cooperative link yields a higher secrecy rate than sharing only data bits, particularly when C is small.
• When C = n (cooperative link as strong as the interference link), the scheme achieves the maximum possible rate of max{m, n} for all α ≠ 1, indicating optimal performance under strong cooperation.
• The scheme achieves nonzero secrecy rate in all interference regimes except when α = 1, and cooperation is essential for secrecy in high-interference scenarios.