###### Abstract  
In this paper, a novel interference free dual-hop device-to-device (D2D) aided cooperative relaying strategy (CRS) based on spatial modulation (SM) (termed D2D-CRS-SM) is proposed. In D2D-CRS-SM, two cellular users (e.g., a near user (NU) and a relay-aided far user (FU)) and a pair of D2D transmitter (D\({}_{1}\))-receivers (D\({}_{2}\)) are served in two time-slots. Two different scenarios are investigated considering information reception criteria at the NU. Irrespective of the scenarios, the base station (BS) exploits SM to map information bits into two sets: modulation bits and antenna index, in phase-1. In the first scenario, the BS maps FU information as the modulation bits and NU information as antenna index, whereas modulation bits correspond to NU information and the antenna index carries FU's information in scenario-2. The iterative-maximum ratio combining (\(i\)-MRC) technique is then used by NU and D\({}_{1}\) to de-map their desired information bits. During phase-2, D\({}_{1}\) also exploits SM to forward FU's information received from BS and its own information bits to the D2D receiver D\({}_{2}\). Then, FU and D\({}_{2}\) retrieve their desired information by using \(i\)-MRC. Due to exploiting SM in both phases, interference free information reception is possible at each receiving node without allocating any fixed transmit power. The performance of D2D-CRS-SM is studied in terms of bit-error rate and spectral efficiency considering \(M\)-ary phase shift keying and quadrature amplitude modulation. Finally, the efficiency of D2D-CRS-SM is demonstrated via the Monte Carlo simulation. bit error rate; device-to-device communication; interference free communications; spatial modulation; spectral efficiency +
Footnote †: journal:  
0000-000-0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-000000-000000-000000-000000-000000-0000000-0000000000  
started to be deployed in the different parts of the world. However, a single technology alone cannot fulfill the performance requirements of 5G and beyond networks; multiple technologies should be integrated [5; 6]. This motivates us to exploit the spatial modulation (SM) in a cooperative relaying scenario with the aid of D2D communication to achieve interference free communication, the key work of this paper. In a situation where the communication link between the source and destination becomes hostile for data transmission due to poor channel condition or fading in the channel (e.g., user located at cell edge), the use of cooperative communication techniques is a viable solution. In cooperative relaying strategy (CRS), the source transmits information data to the destination which is also heard by a relay node being somewhere in between the source and the destination. Because of its location, both source-to-relay and relay-to-destination channel conditions become favorable for reliable communications. Then the relay eventually processes and forwards the overheard data signal to the destination following some cooperation protocols. With the received signal from the relay, the destination decodes the information transmitted from the source [7; 8; 9]. Cooperative communication potentially improves network coverage and link reliability while reducing cost [10; 11]. In recent years, wireless researchers around the globe have investigated various advanced communication paradigms, including SM multiple-input and multiple-output (MIMO) (termed SM-MIMO) to enhance the capacity and reliability performance of the system or network with reduced complexity [12; 13; 14; 15; 16; 17; 18]. In MIMO, multiple antennas transmit and receive at the same time using conventional modulation techniques that results in a capacity gain [19]. However, the performance of MIMO communications largely depend on antenna spacing of transmission and reception [20; 21].