Device-to-Device Assisted Downlink Broadcast Channel in Cellular Networks

In this paper, two protocols of device-to-device (D2D) communication are proposed to assist multi-input multi-output downlink broadcast channel in cellular networks. Devices in a D2D group are arranged to extract their own data originated from a base station (BS) in an order according to their decoding performance. At each intermediate hop, a best-decoding node is selected and responsible for the next hop transmission. In the first protocol, the selected user forwards its own data stream after decoding, then a proper interference cancellation is performed at each receiving node to eliminate this interference from the buffered reception of the broadcast channel in the first hop from the BS. A closed form representation of the outage probability of each node is derived. In the second protocol, the selected user re-constructs its own signal and cancels this signal from its received vector and forwards the resultant vector. This forwarded signal contains less interference and preserves the data information for the users who have not yet decoded their data. The receiving nodes decode their data streams by jointly considering the received vectors from all the previous hops. The comparison of the two proposed protocols in terms of computational complexity, achieved diversity order and performance are provided. We show that the proposed protocols provide promising diversity gain and avoid error propagations as compared to traditional schemes.