Opportunistic Network Decoupling with Virtual Full-Duplex Operation in Multi-Source Interfering Relay Networks

Abstract

We introduce a new achievability scheme, termed opportunistic network decoupling (OND), operating in virtual full-duplex mode. In the scheme, a novel relay scheduling strategy is utilized in the K × N × K channel with interfering relays, consisting of K source-destination pairs and N half-duplex relays in-between them. A subset of relays using alternate relaying is opportunistically selected in terms of producing the minimum total interference level, thereby resulting in network decoupling. As our main result, it is shown that under a certain relay scaling condition, the OND protocol achieves K degrees of freedom even in the presence of interfering links among relays. Numerical evaluation is also shown to validate the performance of the proposed OND. Our protocol basically operates in a fully distributed fashion along with local channel state information, thereby resulting in a relatively easy implementation. Index TermsDegrees of freedom (DoF), half-duplex, interference, K ×N ×K channel, opportunistic network decoupling (OND), relay, virtual full-duplex (FD). On the one hand, following up on these successes for single-hop networks, more recent and emerging work has studied multihop networks with multiple source-destination (S-D) pairs. For the 2-user 2-hop network with 2 relays (referred to as the 2×2×2 interference channel), it was shown in [10] that interference neutralization combining with symbol extension achieves the optimal DoF. A more challenging network model is to consider K-user two-hop relayaided interference channels, consisting of K source-destination (S-D) pairs and N helping relay nodes located in the path between S-D pairs, so-called the K × N × K channel. Several achievability schemes have been known for the network, but more detailed understanding is still in progress. By applying the result from [11] to the K × N × K channel, one can show that K/2 DoF is achieved by using orthogonalize-and-forward relaying, which completely neutralizes interference at all destinations if N is greater than or equal to K(K − 1) + 1. Another achievable scheme, called aligned network diagonalization, was introduced in [12] and was shown to achieve the optimal DoF in the K × N × K channel while tightening the required number of relays. The scheme in [12] is based on the real interference alignment framework [7]. In [10], [12], however, the system model under consideration assumes that there is no interfering signal between relays and the relays are full-duplex. Moreover, in [13], the 2 × 2 × 2 interference channel with full-duplex relays interfering with each other was characterized and its DoF achievability was shown using aligned interference neutralization.

Multi-Stream Opportunistic Network Decoupling: Relay Selection and Interference Management

“…Remark 2: We also show an upper bound on DoF total by using the cut-set bound argument similarly as in the singleantenna OND protocol [34,Section 4]. Suppose thatÑ relay nodes are active, whereÑ ∈ {1, 2, · · · , N }.…”

“…By applying opportunism to cooperative communications, various techniques such as opportunistic two-hop relaying [29], [30] and opportunistic routing [31], [32], [33] were investigated. As for the K × N × K channel having interfering relay nodes, opportunistic network decoupling (OND) was recently proposed while showing that K DoF is asymptotically achieved even in the presence of inter-relay interference when N is beyond a certain value [34]. In the OND protocol, two sets of relay nodes are selected among total N relay candidates to alternatively receive signals from source nodes or forward signals to destination nodes in each time slot, thus realizing the virtual full-duplex mode.…”

Disease Control and Prevention in Rare Plants Based on the Dominant Population Selection Method in Opportunistic Social Networks

“…The total number of endangered, threatened, and extinct species in the Hawaiian Islands of the United States has accounted for 49.4% of the total number of plant species in the island. Thus, protecting rare plants has become a common concern among researchers in various industries around the world [ 5 – 9 ].…”

NPLP: An Improved Routing-Forwarding Strategy Utilizing Node Profile and Location Prediction for Opportunistic Networks

“…As the special variants of delay tolerant networks (DTNs) [14] and mobile ad hoc networks (MANETs) [15], opportunistic networks have to undergo the intermittent and unstable communication connectivity in the data dissemination process [16]. As a sequence, the data transmission process in opportunistic networks usually executes the 'store-carry-forward' mechanism [17], indicating that message carriers with data information randomly move to the communication areas of the peers, select the suitable relay nodes from its neighbors and transmit data packets to them via short-range wireless communication technologies such as Bluetooth or Wi-Fi [18]. A concrete example of opportunistic networks is a disaster relief area with destroyed communication infrastructures in which rescuers walk around with smart phones and try to search for victims via wireless or Wi-Fi technologies [19].…”