The widespread use of personal multimedia-rich devices and multi-party video conferencing have made face-to-face communication among multiple users a promising feature. This thesis presents a multi-party conferencing solution with network coding naturally embedded. Our fundamental goal is to study if network coding brings benefits to multi-party conferencing. In this thesis, we first review an existing network coded solution for multi-party conferencing. Then, this solution is evaluated in our framework of evaluating a new transmission protocol for multi-party conferencing. Also, an investigation is set up to dive into the bottlenecks of this network coded solution. Next, an improved solution targeting conferencing services is proposed by tackling the bottlenecks of the existing solution. Based on our experiment results, it is found that network coding does bring benefits in the context of multi-party conferencing.

Network coding (NC) is an optimal data dissemination technique where intermediate nodes linearly combine incoming packets. To recover a network-coded message, a sink must use a Gaussian elimination decoder, but this high-complexity decoder may not be acceptable in resource-constrained applications like sensor networks. A good alternative to Gaussian elimination is for the sink to apply the well-known belief propagation (BP) algorithm; however, the performance and complexity of BP decoding is dependent on the statistics of the linearly-combined packets. In this work, we propose two protocols that address this issue by applying fountain coding paradigms to network codes. For a two-source, single-relay, and single-sink network, named the Y-network, if the relay can network-code incoming packets while maintaining the key properties of the fountain code, then BP decoding can be applied efficiently to recover the original message. Particularly, the sink should see a Soliton-like degree distribution for efficient BP decoding. The first protocol, named Soliton-like rateless coding (SLRC), recognizes that certain encoded packets are essential for BP decoding to perform well. Therefore, the relay protects these important packets by immediately forwarding them to the sink. It can be shown analytically that the proposed scheme is resilient to nodes leaving the transmission session. Through simulations, the SLRC scheme is shown to perform better than buffer-and-forwarding, and the Distributed LT code. Although SLRC achieves good performance, the degree distribution seen by the sink is non-optimal and assumes that a large number of packets can be buffered, which may not always be possible. Extending SLRC, we propose the Improved Soliton-like Rateless Coding (ISLRC) protocol. Assuming a resource-constrained relay, the available resources at the relay are effciently utilized by performing distribution shaping; packets are intelligently linearly combined. The aggregate degree distribution for the worst case is derived and used in performing an asymptotic error analysis using an AND-OR tree analysis. Simulation results show that even under the worst case scenario of ISLRC, better performance can be achieved compared to SLRC and other existing schemes. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-10-07 21:13:03.862

The widespread use of personal multimedia-rich devices and multi-party video conferencing have made face-to-face communication among multiple users a promising feature. This thesis presents a multi-party conferencing solution with network coding naturally embedded. Our fundamental goal is to study if network coding brings benefits to multi-party conferencing. In this thesis, we first review an existing network coded solution for multi-party conferencing. Then, this solution is evaluated in our framework of evaluating a new transmission protocol for multi-party conferencing. Also, an investigation is set up to dive into the bottlenecks of this network coded solution. Next, an improved solution targeting conferencing services is proposed by tackling the bottlenecks of the existing solution. Based on our experiment results, it is found that network coding does bring benefits in the context of multi-party conferencing.

We propose a new architecture for wireless mesh networks. In addition to forwarding packets, routers mix (i.e., code) packets from different sources to increase the information content of each transmission. We show that intelligently mixing packets increases network throughput. Our design is rooted in the theory of network coding. In contrast to prior work on network coding, which is mainly theoretical and focuses on multicast traffic, ours is practical and solves the common case of unicast traffic. We present the first implementation of network coding in a wireless network. Our system introduces a coding layer between the IP and MAC layers. It works with UDP and TCP traffic, and hence seamlessly integrates with existing applications. We evaluate our design on a 34-node wireless testbed and show that it delivers a 3-4x increase in the throughput ofwireless mesh networks.

The rapid development of Machine-Type-Communication (MTC) has brought big challenges to cellular networks such as super-dense devices and high-shadowing channels which may substantially decrease the spectrum efficiency and increase devices' power consumption. It is pressing to improve the transmission efficiency for MTC due to the limited wireless spectrum. Lower efficiency may also lead to longer transmission time and more energy consumption which conflict with MTC's requirement of lower power consumption. In order to address the above issues, we propose to apply Network Coding (NC) and Device-to-Device (D2D) communications to MTC devices. Our approach introduces an additional delay for local packet exchange, which is acceptable given that MTC traffic typically has the feature of delay tolerance to certain degree. The benefit of the proposed approach is that the cellular transmissions are no longer user-specific, and thus an additional multi-user diversity gain is achieved. The cellular transmission efficiency will also be increased. How to apply the proposed approach for both downlink and uplink has been studied. For the downlink, in addition to the reduction of cellular resource consumption, the MTC devices' feedback load can also be significantly reduced because the cellular transmissions are not sensitive to user-specific errors. In the uplink, besides the enhanced transmission efficiency for full-buffer traffic, an additional small-data aggregation gain is achieved for MTC small-data traffic. Theoretical performance analyses for both downlink and uplink and the corresponding numerical evaluations are given. Though the proposed NC and D2D approach can improve the transmission efficiency by exploring multi-user diversity gain, poor-quality MTC channels still exist which affect system performance. When the whole group MTC devices in an area experience high shadowing and penetration loss, we have to increase either the resource consumption or the transmitting power to overcome the poor-quality channels. The existing small-cell solution can improve the MTC channel quality, but MTC's unique traffic characteristics and quality of service requirements, as well as other practical issues, make the small-cell deployment unprofi table. Therefore, we propose a solution using Floating Relay (FR) given the mature technologies of Unmanned Aerial Vehicle (UAV). We rst target on the high-shadowing channels of the MTC devices and introduce the FR into the cellular system to improve the transmission efficiency and maximize the system capacity. An optimization problem, given the capacity limit of the FR's back-haul link and the maximum transmission power of each user, is formulated and then theoretically solved. An effective on-line fight path planning algorithm is also proposed. Then, we extend the FR concept to a bigger picture and propose the UAV-assisted heterogeneous cellular solution. Detailed system design and comprehensive analyses on FR-cells deployment including frequency reuse, interference, backhaul resource allocation, and coverage are given. For UAV assisted networking systems, mobility and topology play important roles. How to dispatch a UAV to the optimal location in a mesh network to enhance the coverage and service of the existing network is a critical issue. Given the topology of existing service nodes, a new supplementary UAV can be sent to improve the quality of service especially for the users with poor-quality channels. The location of a newly added UAV is optimized to improve the service quality to the worst point. In summary, we propose two means to improve the transmission efficiency for MTC in this thesis work. The NC and D2D approach can be used when some of the MTC devices have chances to experience better channels because of the fast fading and uneven shadowing. Otherwise, the FR can be applied to proactively improve the channel quality for MTC. The NC and D2D approach sticks to the latest standard in the cellular system and thus provides a down-to-earth and backward-compatible MTC solution for 5G cellular system. The UAV-assisted heterogeneous cellular solution and UAV mesh networks can enable mobile Internet and ultra-reliable low latency communications, respectively. These solutions together effectively and efficiently support MTC, which is key to future proliferation of Internet of Things / Graduate

Wireless networks have received considerable attention recently due to the high user demand for wireless services and the emergence of new applications. This thesis focuses on the problem of information dissemination in a class of wireless networks known as the multi-way relay channel. Physical layer network coding is considered to increase the throughput in these networks. First, an algorithm is proposed that increases the full data exchange throughput by 33% compared to traditional routing. This gain arises from providing common knowledge to users and exploiting this knowledge to restrain some users from transmitting. Second, for complex field network coding, a transmission scheme is designed that ensures the receipt of a QAM constellation at the relay. This requires precoding the user symbols to make all possible combinations distinguishable at the relay. Using this approach, the throughput of data exchange is 1/2 symbol per user per channel use. The error performance of both schemes is derived analytically for AWGN channels. / Graduate

Network coding is a new research area with potential to reduce network resources. With network coding, intermediate nodes forward packets that are linear combinations of previously received packets. The type of networks we consider are vehicle mounted mobile tactical radio networks. Tactical communication may be required in areas where pre-deployed base stations are unavailable. Mobile ad hoc networks satisfy this requirement. Due to low antenna heights, network resources are scarce inmobile networks without base stations. Broadcast traffic, which disseminates information network-wide, is very important in tactical mobile networks. Multipoint relay flooding is a well-known technique for efficient distribution of broadcast traffic. It is therefore interesting to evaluate how much network coding can reduce the number of transmissions in a mobile ad hoc network. In this thesis we show that it is possible to further reduce the number of transmissions for Multipoints Relay flooding by using network coding. However, this improvement is largely theoretical - there has been no effort to evaluate this approach in practice.

The aim of this thesis is to conduct performance investigation of a combined system of Network Coding (NC) technique with Ant-Colony (ACO) routing protocol. This research analyses the impact of several workload characteristics, on system performance. Network coding is a significant key development of information transmission and processing. Network coding enhances the performance of multicast by employing encoding operations at intermediate nodes. Two steps should realize while using network coding in multicast communication: determining appropriate transmission paths from source to multi-receivers and using the suitable coding scheme. Intermediate nodes would combine several packets and relay them as a single packet. Although network coding can make a network achieve the maximum multicast rate, it always brings additional overheads. It is necessary to minimize unneeded overhead by using an optimization technique. On other hand, Ant Colony Optimization can be transformed into useful technique that seeks imitate the ant’s behaviour in finding the shortest path to its destination using quantities of pheromone that is left by former ants as guidance, so by using the same concept of the communication network environment, shorter paths can be formulated. The simulation results show that the resultant system considerably improves the performance of the network, by combining Ant Colony Optimization with network coding. 25% improvement in the bandwidth consumption can be achieved in comparison with conventional routing protocols. Additionally simulation results indicate that the proposed algorithm can decrease the computation time of system by a factor of 20%.

Random linear network coding is widely proposed as the solution for practical network coding applications due to the robustness to random packet loss, packet delays as well as network topology and capacity changes. In order to implement random linear network coding in practical scenarios where the encoding and decoding methods perform efficiently, the computational complex coding algorithms associated with random linear network coding must be overcome. This research contributes to the field of practical random linear network coding by presenting new, low complexity coding algorithms with low decoding delay. In this thesis we contribute to this research field by building on the current solutions available in the literature through the utilisation of familiar coding schemes combined with methods from other research areas, as well as developing innovative coding methods. We show that by transmitting source symbols in predetermined and constrained patterns from the source node, the causality of the random linear network coding network can be used to create structure at the receiver nodes. This structure enables us to introduce an innovative decoding scheme of low decoding delay. This decoding method also proves to be resilient to the effects of packet loss on the structure of the received packets. This decoding method shows a low decoding delay and resilience to packet erasures, that makes it an attractive option for use in multimedia multicasting. We show that fountain codes can be implemented in RLNC networks without changing the complete coding structure of RLNC networks. By implementing an adapted encoding algorithm at strategic intermediate nodes in the network, the receiver nodes can obtain encoded packets that approximate the degree distribution of encoded packets required for successful belief propagation decoding. Previous work done showed that the redundant packets generated by RLNC networks can be used for error detection at the receiver nodes. This error detection method can be implemented without implementing an outer code; thus, it does not require any additional network resources. We analyse this method and show that this method is only effective for single error detection, not correction. In this thesis the current body of knowledge and technology in practical random linear network coding is extended through the contribution of effective decoding techniques in practical network coding networks. We present both analytical and simulation results to show that the developed techniques can render low complexity coding algorithms with low decoding delay in RLNC networks. / Thesis (PhD (Computer Engineering))--North-West University, Potchefstroom Campus, 2013

Random linear network coding is widely proposed as the solution for practical network coding applications due to the robustness to random packet loss, packet delays as well as network topology and capacity changes. In order to implement random linear network coding in practical scenarios where the encoding and decoding methods perform efficiently, the computational complex coding algorithms associated with random linear network coding must be overcome. This research contributes to the field of practical random linear network coding by presenting new, low complexity coding algorithms with low decoding delay. In this thesis we contribute to this research field by building on the current solutions available in the literature through the utilisation of familiar coding schemes combined with methods from other research areas, as well as developing innovative coding methods. We show that by transmitting source symbols in predetermined and constrained patterns from the source node, the causality of the random linear network coding network can be used to create structure at the receiver nodes. This structure enables us to introduce an innovative decoding scheme of low decoding delay. This decoding method also proves to be resilient to the effects of packet loss on the structure of the received packets. This decoding method shows a low decoding delay and resilience to packet erasures, that makes it an attractive option for use in multimedia multicasting. We show that fountain codes can be implemented in RLNC networks without changing the complete coding structure of RLNC networks. By implementing an adapted encoding algorithm at strategic intermediate nodes in the network, the receiver nodes can obtain encoded packets that approximate the degree distribution of encoded packets required for successful belief propagation decoding. Previous work done showed that the redundant packets generated by RLNC networks can be used for error detection at the receiver nodes. This error detection method can be implemented without implementing an outer code; thus, it does not require any additional network resources. We analyse this method and show that this method is only effective for single error detection, not correction. In this thesis the current body of knowledge and technology in practical random linear network coding is extended through the contribution of effective decoding techniques in practical network coding networks. We present both analytical and simulation results to show that the developed techniques can render low complexity coding algorithms with low decoding delay in RLNC networks. / Thesis (PhD (Computer Engineering))--North-West University, Potchefstroom Campus, 2013