Abstract
This study investigates the superiority of cooperative broadcast transmission over traditional orthogonal schemes when applied in a downlink relaying broadcast channel (RBC). Two proposed cooperative broadcast transmission protocols, one with an amplify-and-forward (AF) relay, and the other with a repetition-based decode-and-forward (DF) relay, are investigated. By utilizing superposition coding (SupC), the source and the relay transmit the private user messages simultaneously instead of sequentially as in traditional orthogonal schemes, which means the channel resources are reused and an increased channel degree of freedom is available to each user, hence the half-duplex penalty of relaying is alleviated. To facilitate a performance evaluation, theoretical outage probability expressions of the two broadcast transmission schemes are developed, based on which, we investigate the minimum total power consumption of each scheme for a given traffic requirement by numerical simulation. The results provide details on the overall system performance and fruitful insights on the essential characteristics of cooperative broadcast transmission in RBCs. It is observed that better overall outage performances and considerable power gains can be obtained by utilizing cooperative broadcast transmissions compared to traditional orthogonal schemes.
Highlights
In recent years, a wireless sensor network has developed rapidly [1,2,3] and been widely used in many fields, such as meteorology [4,5]
We consider a two-dimensional model as in Figure 3, where θ1 is the angle of the line Nd1 − Ns − Nr, θ2 is the angle of the line Nd2 − Ns − Nr, and dij denotes the Euclidean distance between Ni and Nj
Two cooperative broadcast transmission protocols have been considered for the two-user dedicated relaying broadcast channel (RBC)
Summary
A wireless sensor network has developed rapidly [1,2,3] and been widely used in many fields, such as meteorology [4,5]. Relaying has been shown to achieve anti-fading capability in the future wireless sensor network [6]. The most investigated protocols are the amplify-and-forward (AF) and repetition-coded decode-and-forward (DF) protocols with a half-duplex operation, which fit well into existing systems. In BCs, since the source knows the messages of all users, non-orthogonal schemes that transmit multiple user messages simultaneously may reduce the overall consumed bandwidth and exploit the residual degrees of freedom, potentially provide better performance. It is necessary to extend relays to BCs (namely RBC) and investigate how the inherent benefits of BCs can be utilized for efficient relaying
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