We design efficient polynomial time algorithms to solve the NP-hard problem with provably the best approximation factor, and verify their effectiveness using realistic simulations. In addition, we formulate a unifying optimization framework that jointly considers relay assignment, relay strategy selection, channel assignment and power allocation to reap different forms of gains. It can greatly improve the relay efficiency by over 100% mostly, thus uplifting the throughput performance by over 30% compared to conventional cooperative diversity scheme.
In this paper, we propose XOR-CD, a novel XOR-assisted cooperative diversity scheme in OFDMA wireless networks. This work represents the first attempt to unravel these two questions.
IPACK BLOCK CPT CODE HOW TO
Moreover, the question of how to practically realize the promising gains available, including multi-user diversity, cooperative diversity and network coding in multi-channel networks, also remains unexplored. However, it is not clear how network coding based cooperative diversity can be exploited effectively in multi-channel networks where overhearing is not readily available. Network coding has been leveraged with cooperative diversity to improve performance in single channel wireless networks. Specifically, RDNC is as good as COPE in the worst case, but can achieve up to 2.5 times the coding gain if the network topology permits. Through extensive simulation, we find that RDNC significantly boosts the coding gain and the throughput, more when the given topology provides richer opportunities for coding. With RDNC, the relay node can deal with receivers under disparate channel conditions with a single coded data stream, eliminating the single-rate broadcast bottleneck. In this paper, we solve this "broadcast bottleneck" by using a novel symbol-level network coding scheme called Rate Diverse Network Coding (RDNC). Worse yet, the bottleneck capacity diminishes as the diversity of links increases, which generally happens when the nodes participating in network coding operation grow in number. Since the selected rate should be supported on the worst quality links to the intended receivers, the throughput gain by network coding is essentially bound to the capacity of the worst link. We also validate our results by implementing iPack on a small-scale testbed based on GNU Radio.Īn inherent limitation of the existing digital wireless network coding is that the relay node has to settle for a single broadcast rate for the coded packet transmission.
In a typical wireless mesh network when more traffic is between the clients and access points, the average throughput improvement of iPack, our joint optimization scheduler, can be 324%, while there can be little gain (less than 10%) if network coding alone is used. Using extensive simulations, we find that the throughput gain of the joint coding iPack algorithm is 30% more than the better performer of network coding and superposition coding in a wide range of scenarios, and automatically takes advantage of the best available coding opportunities.
In this paper, we propose iPack, an algorithm for in-network generation of composite packets that integrates coding at two different layers of the protocol stack: XOR-based network coding and physical layer superposition coding. However, the optimal mixing algorithm that maximizes throughput is still unknown. Many in-network packet mixing techniques at the network layer, , as well as the physical layer, , have been shown to substantially improve throughput. A major barrier for the adoption of wireless mesh networks is severe limits on throughput.
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