MAC Centered Cooperation - Synergistic Design of Network Coding, Multi-Packet Reception, and Improved Fairness to Increase Network Throughput

We design a cross-layer approach to aid in develop- ing a cooperative solution using multi-packet reception (MPR), network coding (NC), and medium access (MAC). We construct a model for the behavior of the IEEE 802.11 MAC protocol and apply it to key small canonical topology components and their larger counterparts. The results obtained from this model match the available experimental results with fidelity. Using this model, we show that fairness allocation by the IEEE 802.11 MAC can significantly impede performance; hence, we devise a new MAC that not only substantially improves throughput, but provides fairness to flows of information rather than to nodes. We show that cooperation between NC, MPR, and our new MAC achieves super-additive gains of up to 6.3 times that of routing with the standard IEEE 802.11 MAC. Furthermore, we extend the model to analyze our MAC's asymptotic and throughput behaviors as the number of nodes increases or the MPR capability is limited to only a single node. Finally, we show that although network performance is reduced under substantial asymmetry or limited implementation of MPR to a central node, there are some important practical cases, even under these conditions, where MPR, NC, and their combination provide significant gains

An Extended Network Coding Opportunity Discovery Scheme in Wireless Networks

Network coding is known as a promising approach to improve wireless network performance. How to discover the coding opportunity in relay nodes is really important for it. There are more coding chances, there are more times it can improve network throughput by network coding operation. In this paper, an extended network coding opportunity discovery scheme (ExCODE) is proposed, which is realized by appending the current node ID and all its 1-hop neighbors' IDs to the packet. ExCODE enables the next hop relay node to know which nodes else have already overheard the packet, so it can discover the potential coding opportunities as much as possible. ExCODE expands the region of discovering coding chance to n-hops, and have more opportunities to execute network coding operation in each relay node. At last, we implement ExCODE over the AODV protocol, and efficiency of the proposed mechanism is demonstrated with NS2 simulations, compared to the existing coding opportunity discovery scheme.Comment: 15 pages and 7 figure

Performance Analysis of Network Coding with IEEE 802.11 DCF in Multi-Hop Wireless Networks

Network coding is an effective idea to boost the capacity of wireless networks, and a variety of studies have explored its advantages in different scenarios. However, there is not much analytical study on throughput and end-to-end delay of network coding in multi-hop wireless networks considering the specifications of IEEE 802.11 Distributed Coordination Function. In this paper, we utilize queuing theory to propose an analytical framework for bidirectional unicast flows in multi-hop wireless mesh networks. We study the throughput and end-to-end delay of inter-flow network coding under the IEEE 802.11 standard with CSMA/CA random access and exponential back-off time considering clock freezing and virtual carrier sensing, and formulate several parameters such as the probability of successful transmission in terms of bit error rate and collision probability, waiting time of packets at nodes, and retransmission mechanism. Our model uses a multi-class queuing network with stable queues, where coded packets have a non-preemptive higher priority over native packets, and forwarding of native packets is not delayed if no coding opportunities are available. Finally, we use computer simulations to verify the accuracy of our analytical model.Comment: 14 pages, 11 figures, IEEE Transactions on Mobile Computing, 201

Co-Designing Multi-Packet Reception, Network Coding, and MAC Using a Simple Predictive Model

We design a cross-layer approach to optimize the joint use of multi-packet reception and network coding, in order to relieve congestion. We construct a model for the behavior of the 802.11 MAC and apply it to several key canonical topology components and their extensions to any number of nodes. The results obtained from this model match the available experimental results, which are for routing and opportunistic network coding, with fidelity. Using this model, we show that fairness allocation by the MAC can seriously impact performance; hence, we devise a new MAC that not only substantially improves throughput relative to the current 802.11 MAC, but also provides fairness to flows of information rather than to nodes. We show that the proper combination of network coding, multi-packet reception, and our new MAC protocol achieves super-additive throughput gains of up to 6.3 times that of routing alone with the use of the standard 802.11 MAC. Finally, we extend the model to analyze the asymptotic behavior of our new MAC as the number of nodes increases.Comment: 8 Pages, 10 Figures, Submitted to WiOpt 201

Effects of MAC Approaches on Non-Monotonic Saturation with COPE - A Simple Case Study

We construct a simple network model to provide insight into network design strategies. We show that the model can be used to address various approaches to network coding, MAC, and multi-packet reception so that their effects on network throughput can be evaluated. We consider several topology components which exhibit the same non-monotonic saturation behavior found within the Katti et. al. COPE experiments. We further show that fairness allocation by the MAC can seriously impact performance and cause this non-monotonic saturation. Using our model, we develop a MAC that provides monotonic saturation, higher saturation throughput gains and fairness among flows rather than nodes. The proposed model provides an estimate of the achievable gains for the cross-layer design of network coding, multi-packet reception, and MAC showing that super-additive throughput gains on the order of six times that of routing are possible.United States. Dept. of Defense (Air Force Contract FA8721-05-C-0002)Irwin Mark Jacobs and Joan Klein Jacobs Presidential FellowshipInformation Systems of ASD(R&E

To Send or Not to Send: An Optimal Stopping Approach to Network Coding in Multi-hop Wireless Networks

Network coding is all about combining a variety of packets and forwarding as much packets as possible in each transmission operation. The network coding technique improves the throughput efficiency of multi-hop wireless networks by taking advantage of the broadcast nature of wireless channels. However, there are some scenarios where the coding cannot be exploited due to the stochastic nature of the packet arrival process in the network. In these cases, the coding node faces two critical choices: forwarding the packet towards the destination without coding, thereby sacrificing the advantage of network coding, or, waiting for a while until a coding opportunity arises for the packets. Current research works have addressed this challenge for the case of a simple and restricted scheme called reverse carpooling where it is assumed that two flows with opposite directions arrive at the coding node. In this paper the issue is explored in a general sense based on the COPE architecture requiring no assumption about flows in multi-hop wireless networks. In particular, we address this sequential decision making problem by using the solid framework of optimal stopping theory, and derive the optimal stopping rule for the coding node to choose the optimal action to take, i.e. to wait for more coding opportunity or to stop immediately (and send packet). Our simulation results validate the effectiveness of the derived optimal stopping rule and show that the proposed scheme outperforms existing methods in terms of network throughput and energy consumption

A Survey of Delay Tolerant Networks Routing Protocols

Advances in Micro-Electro-Mechanical Systems (MEMS) have revolutionized the digital age to a point where animate and inanimate objects can be used as a communication channel. In addition, the ubiquity of mobile phones with increasing capabilities and ample resources means people are now effectively mobile sensors that can be used to sense the environment as well as data carriers. These objects, along with their devices, form a new kind of networks that are characterized by frequent disconnections, resource constraints and unpredictable or stochastic mobility patterns. A key underpinning in these networks is routing or data dissemination protocols that are designed specifically to handle the aforementioned characteristics. Therefore, there is a need to review state-of-the-art routing protocols, categorize them, and compare and contrast their approaches in terms of delivery rate, resource consumption and end-to-end delay. To this end, this paper reviews 63 unicast, multicast and coding-based routing protocols that are designed specifically to run in delay tolerant or challenged networks. We provide an extensive qualitative comparison of all protocols, highlight their experimental setup and outline their deficiencies in terms of design and research methodology. Apart from that, we review research that aims to exploit studies on social networks and epidemiology in order to improve routing protocol performance. Lastly, we provide a list of future research directions.Comment: 56 page

A Joint Network Coding and Scheduling Algorithm in Wireless Network

Network coding (NC) is an emerging technique of packet forwarding thatencodes packets at relay node in order to increase network throughput. It is understoodthat the performance of NC is strongly dependent on the physical layer as well as theMAC layer, and greedy coding method may in fact reduce the network throughputowing to the reduction in the spatial reuse. In this paper, we propose a NC-awarescheduling method combining link aggregation to improve the network throughput byconsidering the interplay between NC and spatial reuse. Simulation resultsdemonstrate the effectiveness of our proposed link aggregation method compared withthe unicast transmission model

Handling Mobility in Dense Networks

Network densification is one of key technologies in future networks to significantly increase network capacity. The gain obtained by network densification for fixed terminals have been studied and proved. However for mobility users, there are a number of issues, such as more frequent handover, packet loss due to high mobility, interference management and so on. The conventional solutions are to handover high speed mobiles to macro base stations or multicast traffic to multiple base stations. These solutions fail to exploit the capacity of dense networks and overuse the backhaul capacity. In this paper we propose a set of solutions to systematically solve the technical challenges of mobile dense networks. We introduce network architecture together with data transmission protocols to support mobile users. A software-defined protocol (SDP) concept is presented so that combinations of transport protocols and physical layer functions can be optimized and triggered on demand. Our solutions can significantly boost performance of dense networks and simplify the packet handling process. Importantly, the gain brought by network densification to fixed users can also be achieved for mobile users