Rajendra Prasad Sirigina

Performance analysis of Z-channel with relay under Rayleigh fading and discrete constellations

Interference forwarding in an interference channel makes the interference stronger which in turn enables the usage of simple detectors like the successive interference canceler (SIC) at the destinations. In this paper, detect and forward (DF), amplify and forward (AF) based interference forwarding protocols (also called as AF-SIC and DF-SIC protocols) are analyzed. Symbol error rate (SER) performance of the SIC, AF-SIC and DF-SIC protocols using M-PAM modulation is studied. Also the relay channel gains required to restore full diversity for the AF-SIC and the DF-SIC protocols are obtained. Impact of the relay power and relay location on the SER performance is also studied. The proposed protocols are proved to provide the same SER performance as the orthogonal transmission scheme while improving the spectral efficiency.

Cognitive Radio for Aeronautical Communications: A Survey

Novel air traffic management (ATM) strategies are proposed through the Next Generation Air Transportation and Single European Sky for ATM Research projects to improve the capacity of the airspace and to meet the demands of the future air traffic. The implementation of the proposed solutions leads to increasing use of wireless data for aeronautical communications. Another emerging trend is the unmanned aerial vehicles. The unmanned aerial systems (UASs) need reliable wireless data link and dedicated spectrum allocation for its operation. On-board broadband connectivity also needs dedicated spectrum to satisfy the quality of service requirements of the users. With the growing demand, the aeronautical spectrum is expected to be congested. However, the studies revealed that the aeronautical spectrum is underutilized due to the static spectrum allocation strategy. The aeronautical communication systems, such as air-air and air-ground communication systems, inflight infotainment systems, wireless avionics intra-communications, and UAS, can benefit significantly from the introduction of cognitive radio-based transmission schemes. This paper summarizes the current trends in aeronautical spectrum management followed by the major applications and contributions of cognitive radio in solving the spectrum scarcity crisis in the aeronautical domain. Also, to cope with the evolving technological advancement, researchers have prioritized the issues in the case of cognitive radio that needs to be addressed depending on the domain of operation. The proposed cognitive aeronautical communication systems should also be compliant with the Aeronautical Radio Incorporated and Aerospace Recommended Practice standards. An overview of these standards and the challenges that need immediate attention to make the solution feasible for a large-scale operation, along with the future avenues of research is also furnished.

On the Diversity Gain Region for the Relay Assisted Interference Management

The present paper focuses on the interference management in a two-user Z-channel where one user is interference-limited while the other user is interference-free. The achievable diversity gain region (DGR) with interference forwarding by a full-duplex decode-and-forward (FD-DF) relay and successive interference cancellation (SIC) at the interference-limited destination is studied. The achievable DGR of the FD-DF relay is compared with that of the direct transmission scheme. The impact of the phase-noise in the self-interference cancellation circuit of the full-duplex relay and the impact of the number of blocks in the superposition block Markov (SPBM) encoding on the achievable DGR are studied. The direct transmission scheme with joint decoding at the interference-limited receiver is shown to perform well at the lower multiplexing gain region (MGR). If the multiplexing gain of the interference is high, then the interference forwarding by the DF relay does not help, and the direct transmission scheme with interference ignorant detection at the interference-limited receiver achieves better DGR. The FD-DF relay is shown to provide better DGR at only the moderate MGR.

On the Symbol Error Rate and Diversity Gain Region of the Relay-Assisted Z-channel

Interference forwarding in a Z-channel makes interference stronger, which in turn enables usage of simple detectors like successive interference canceler (SIC) at interference-limited destination. In this work, the following protocols with SIC at the interference-limited destination are investigated: direct transmission (SICDirect), half-duplex decode-and-forward (SICDF), and half-duplex amplify-and-forward (SICAF) protocols. The achievable diversity orders of these protocols using M-PAM and M-QAM modulation are obtained. Moreover, minimum required exponential orders of the average received signal powers at the relay and interference-limited destination to restore full diversity are presented. The SICAF and SICDF protocols are shown to achieve the same diversity order as that of the orthogonal transmission scheme while achieving better spectral efficiency than the orthogonal transmission. Closed-form expressions for the achievable diversity gain regions (DGRs) with the SICDirect, SICDF, and SICAF protocols are derived. Selective decode-and-forward with SIC (SICSDF) is also considered. The multiplexing gain regions and the interference levels where the SICAF and SICSDF protocols achieve better DGR than the SICDirect protocol are obtained.

Full-Duplex Decode-and-Forward Relay-Assisted Interference Management: A Diversity Gain Region Perspective

A two-user Z-channel with a full-duplex (FD) decode-and-forward (DF) relay, where one user is interference-limited while the other user is interference-free, is considered in this paper. The FD-DF relay can decode either a part of the interference or the entire interference. The former is called partial DF (PDF) protocol, and the latter is called complete DF (CDF) protocol. In the case of PDF protocol, the interference-limited user does partial interference cancellation. A closed-form expression for achievable diversity gain region (DGR) with the PDF protocol is presented. Furthermore, achievable DGR of the PDF protocol is optimized under the constraint that the interference-free receiver achieves optimal diversity gain. At low interference levels, the PDF protocol provides better DGR compared to both CDF protocol and direct transmission scheme. As the interference level increases, either the CDF protocol or the direct transmission scheme is shown to achieve better DGR compared to PDF protocol. The multiplexing gain regions where the PDF, CDF, and direct transmission schemes perform well are identified.

DMT for the Relay Assisted Interference Cancellation over Nakagami-m Fading Channel

In the present work, the diversity multiplexing tradeoff (DMT) for a decode-and-forward relay assisted two-user Z-channel with Nakagami-m fading is studied. In a two-user Z-channel, only one user is interference-limited while the other user is interference-free. Two transmission schemes, namely, common message only (CMO) and rate splitting (RS) schemes, are studied. In the CMO scheme, the interfering source uses single-user (SU) codes, and the interference-limited destination cancels the total interference. In the RS scheme, the interfering source uses multi-user (MU) codes, and the interference-limited user does partial interference cancellation. Closed-form expressions for the achievable DMTs with both the schemes are presented. The RS and the CMO schemes are shown to provide better DMT at the moderate and higher levels of interference, respectively.

Interference mitigation in Z-channel and relay-assisted Z-channel: a diversity gain region perspective

Abstract This work considers the interference management in Z-channel and full-duplex decode-and-forward (FD DF) relay-assisted Z-channel. In the case of Z-channel, closed-form expressions for the achievable diversity gain regions (DGRs) with both single-user (SU) codes and multi-user (MU) codes are presented. The closed-form expression for the achievable DGR of the clustered FD DF relay-assisted Z-channel with SU codes is also presented. In the Z-channel, if the interference-free receiver is constrained to operate at optimal diversity multiplexing tradeoff (DMT), the SU codes are shown to achieve better DGR than MU codes. Furthermore, in the Z-channel, the SU codes achieve DGR outer bound at low multiplexing gain region, and MU codes can never achieve DGR outer bound. Also, we have shown that Z-channel with two co-located antennas at the interfering transmitter achieves better DGR compared to that of the clustered FD DF relay-assisted Z-channel with single antenna at the interfering transmitter.

Relay-assisted interference cancellation for cognitive aeronautical communication systems

Traditional air-ground communication systems are based on the principle of orthogonal transmission. For example, two adjacent Ground Stations communicate with their respective Air Stations on different subchannels. The orthogonal transmission leads to interference-free reception. However, the orthogonal transmission schemes also lead to poor spectrum utilization. Due to the limited spectrum availability, orthogonal transmission schemes may not cater the needs of future aeronautical communication demands. In this context, the present work proposes a cognitive overlay mode of transmission that is based on the non-orthogonal transmission to improve the spectrum efficiency. But the receivers in the non-orthogonal transmission based systems are interference-limited. This paper proposes decode-and-forward and amplify-and-forward relay-assisted interference cancellation schemes to mitigate the interference. The proposed relaying methods improve the reliability of the signal detection at the interference-free receiver. The ground-air wireless channels are modeled as Nakagami-m faded channel. The achievable diversity gain that characterizes the reliability of the signal detection at the receivers is also presented. The achievable diversity-multiplexing tradeoffs for the orthogonal and non-orthogonal transmission schemes are investigated in detail.

Dynamic decode-and-forward relay-assisted interference management for spectrum efficient ground-to-air communication systems

In this work, full frequency reuse based transmission scheme is proposed for the ground-air communication systems. In full frequency reuse based systems, the receivers are interference-limited, and in this work, interference forwarding with a half-duplex (HD) dynamic decode-and-forward (DDF) relay is proposed to mitigate the interference. The HD DDF relay forwards the interference towards the interference-limited air station. The interference forwarding enhances the interference level such that the interference-limited air station can mitigate the strong interference. The diversity-multiplexing tradeoff (DMT) for the proposed HD DDF relay-aided interference mitigation scheme is evaluated. The impact of the multiplexing gain of the interfering signal on the reliability of the signal detection at the interference-limited air station is evaluated. The DMT of the proposed protocol is compared with that of the direct transmission scheme and the half-duplex decode-and-forward relay-aided interference mitigation scheme.

SLAR: A smart regenerative cooperative protocol with improved power and spectral efficiency

Selective decode and forward (SDF) based cooperative relaying protocol can provide full diversity. But SDF protocol requires bandwidth consuming cyclic redundancy check (CRC) bits to prevent error propagation from the relay. Link adaptive regenerative relaying (LAR) scheme avoids the need for CRC bits to reduce the error propagation from relay and can provide full diversity. But in the conventional LAR based schemes, relay will always participate in the cooperation irrespective of the quality of the source to destination link. This results in a spectral efficiency of 0.5 symbols per channel use (SPCU) only. To improve the transmission rate, the present paper proposes selective link adaptive regenerative relaying (SLAR) scheme, where the relay will make use of the source to destination channel information to decide whether to cooperate or not. It is proved that the proposed scheme can achieve the full diversity order. The spectral efficiency and power efficiency of the protocol are considerably improved compared to the conventional LAR scheme.