Emiliano Garcia-Palacios

Multimedia resource allocation in mmwave 5G networks

The 5G network infrastructure is driven by the evolution of todays most demanding applications. Already, multimedia applications such as on-demand HD video and IPTV require gigabit- per-second throughput and low delay, while future technologies include ultra HDTV and machine-to-machine communication. Mm-Wave technologies such as IEEE 802.15.3c and IEEE 802.11ad are ideal candidates to deliver high throughput to multiple users demanding differentiated QoS. Optimization is often used as a methodology to meet throughput and delay constraints. However, traditional optimization techniques are not suited to a mixed set of multimedia applications. Particle swarm optimization (PSO) is shown as a promising technique in this context. Channel-time allocation PSO (CTA-PSO) is successfully shown here to allocate resource even in scenarios where blockage of the 60 GHz signal poses significant challenges.

Evaluating the impact of network density, hidden nodes and capture effect for throughput guarantee in multi-hop wireless networks

To optimize the performance of wireless networks, one needs to consider the impact of key factors such as interference from hidden nodes, the capture effect, the network density and network conditions (saturated versus non-saturated). In this research, our goal is to quantify the impact of these factors and to propose effective mechanisms and algorithms for throughput guarantees in multi-hop wireless networks. For this purpose, we have developed a model that takes into account all these key factors, based on which an admission control algorithm and an end-to-end available bandwidth estimation algorithm are proposed. Given the necessary network information and traffic demands as inputs, these algorithms are able to provide predictive control via an iterative approach. Evaluations using analytical comparison with simulations as well as existing research show that the proposed model and algorithms are accurate and effective.

Channel Time Allocation PSO for Gigabit Multimedia Wireless Networks

This article introduces a resource allocation solution capable of handling mixed media applications within the constraints of a 60 GHz wireless network. The challenges of multimedia wireless transmission include high bandwidth requirements, delay intolerance and wireless channel availability. A new Channel Time Allocation Particle Swarm Optimization (CTA-PSO) is proposed to solve the network utility maximization (NUM) resource allocation problem. CTA-PSO optimizes the time allocated to each device in the network in order to maximize the Quality of Service (QoS) experienced by each user. CTA-PSO introduces network-linked swarm size, an increased diversity function and a learning method based on the personal best, Pbest, results of the swarm. These additional developments to the PSO produce improved convergence speed with respect to Adaptive PSO while maintaining the QoS improvement of the NUM. Specifically, CTA-PSO supports applications described by both convex and non-convex utility functions. The multimedia resource allocation solution presented in this article provides a practical solution for real-time wireless networks.

Cross-layer framework for fine-grained channel access in next generation high-density WiFi networks

Densely deployed WiFi networks will play a crucial role in providing the capacity for next generation mobile internet. However, due to increasing interference, overlapped channels in WiFi networks and throughput efficiency degradation, densely deployed WiFi networks is not a guarantee to obtain higher throughput. An emergent challenge is how to efficiently utilize scarce spectrum resources, by matching physical layer resources to traffic demand. In this aspect, access control allocation strategies play a pivotal role but remain too coarse-grained. As a solution, this research proposes a flexible framework for fine-grained channel width adaptation and multi-channel access in WiFi networks. This approach, named SFCA (Sub-carrier Fine-grained Channel Access), adopts DOFDM (Discontinuous Orthogonal Frequency Division Multiplexing) at the PHY layer. It allocates the frequency resource with a sub-carrier granularity, which facilitates the channel width adaptation for multi-channel access and thus brings more flexibility and higher frequency efficiency. The MAC layer uses a frequency-time domain backoff scheme, which combines the popular time-domain BEB scheme with a frequency-domain backoff to decrease access collision, resulting in higher access probability for the contending nodes. SFCA is compared with FICA (an established access scheme) showing significant outperformance. Finally we present results for next generation 802.11ac WiFi networks.

Distributed interference-aware relay selection for IEEE 802.11 based cooperative networks

Cooperative communication has been recently proposed as a way to mitigate fading in wireless networks. Analytical results indicate that network performance improvement by cooperative communication heavily depends on selecting suitable relay nodes. Previous work on relay selection fails to consider the impact of inter-node interference among transmissions, which potentially results in a degradation of network performance. In this study, it is shown how the use of relay nodes may degrade rather than improve network performance (e.g. throughput) in scenarios where inter-node interference is not accounted for. In this approach, inter-node interference is embedded into our relay selection strategy through a newly proposed distributed interference-aware relay selection (DIRS) algorithm for IEEE 802.11-based wireless networks with multiple source–destination pairs. Under DIRS algorithm, each source–destination pair will select an optimal relay based on both the channel quality and the interference information, which can be obtained locally without the knowledge of topology information. The simulation results demonstrate the effectiveness of our proposal and show that inter-node interference can be mitigated by optimising relay selection.

Impact of primary networks on the performance of energy harvesting cognitive radio networks

In this paper, we investigate the effect of of the primary network on the secondary network when harvesting energy in cognitive radio in the presence of multiple power beacons and multiple secondary transmitters. In particular, the influence of the primary transmitters transmit power on the energy harvesting secondary network is examined by studying two scenarios of primary transmitters location, i.e., the primary transmitters location is near to the secondary network and the primary transmitters location is far from the secondary network. In the scenario where the primary transmitter locates near to the secondary network, although secondary transmitter can be benefit from the harvested energy from the primary transmitter, the interference caused by the primary transmitter suppresses the secondary network performance. Meanwhile, in both scenarios, despite the fact that the transmit power of the secondary transmitter can be improved by the support of powerful power beacons, the peak interference constraint at the primary receiver limits this advantage. In addition, the deployment of multiple power beacons and multiple secondary transmitters can improve the performance of the secondary network. The analytical expressions of the outage probability of the secondary network in the two scenarios are also provided and verified by numerical simulations.

Providing security and energy efficiency in wireless ad-hoc sensor networks through Secure Cluster-Head Election (SEC-CH-E)

Data sensed and transferred between sensor nodes should be secure and preserve battery life. Some algorithms, such as LEACH (Low Energy Adaptive Clustering Hierarchy), have been proposed to efficiently organize sensor nodes into clusters, where a cluster-head, is elected to represent that cluster. To save energy, the cluster-head coordinates the cluster and forwards data generated within the cluster. Despite preserving energy, in practice LEACH lacks security features. A Secure Cluster Head Election algorithm (SEC-CH-E) that improves the original LEACH algorithm by adding security features as well as bringing increasing energy savings is proposed. The algorithm takes into account wireless sensor networks constraints such as the limited radio range and power limitations when electing secure cluster-head nodes, which are factors unaccounted for in LEACH. It is shown that these factors have profound energy implications. The superiority of Sec-CH-E performance is assessed by looking at the energy remaining in the network and the fraction of dead nodes.

Calculating End-to-End Throughput Capacity in Wireless Networks with Consideration of Hidden Nodes and Multi-Rate Terminals

To determine the end-to-end throughput capacity of a multi-hop route in wireless networks, existing work either use a simplistic approach to divide the 1-hop throughput capacity by the number of contending links in the bottleneck region, which has limitations in terms of accuracy, or rely on complicated non-linear equations, which is impractical to solve for a large number of hops. In this paper, we present an optimization methodology to analytically calculate the end-to-end throughput capacity of IEEE 802.11-based multi-hop wireless networks. The calculation considers the interference due to neighboring nodes and assess the impact of hidden node collision as well as multi-rate terminals (i.e., nodes can transmit at different rates) on throughput capacity. The proposed methodology provides a very accurate calculation of the end-to-end throughput capacity when compared to existing work, and yet it is more practical to implement.

Utility-based resource allocation for real-time IPTV in wireless networks

Internet Protocol Television (IPTV) is a key growth application for Internet traffic. The combination of real-time services such as video and voice along with best effort Internet access introduces challenging Quality of Service (QoS) issues. In order to meet the QoS requirements, smart resource allocation is required, in particular for IPTV provision across wireless networks. In existing research, IPTV is generally described as a video application. This supports the high bandwidth characteristic of IPTV but not the low latency requirement of realtime transmission. In this work, we present a real-time IPTV utility function describing the application with respect to the stage of transmission. This accurately represents IPTV with high bandwidth, low latency characteristics. The function describes the relationship between allocated channel time and the user perceived quality of the transmission. In an example wireless networking scenario, the resource allocation solution illustrates accurate prioritization in accordance with the individual user requirements.

A PSO approach to resource allocation in wireless networks

Next generation high data rate applications such as High-Definition (HD) video transmission place a heavy load on wireless network resources. To achieve the strict quality of service requirements of HD video in a multi-user network requires efficient resource allocation. Rate-distortion theory provides an appropriate basis for this. The Nash Bargaining Solution (NBS) is proven to generate an optimal solution to a rate-distortion based convex resource allocation problem. Particle Swarm Optimization (PSO) is a meta-heuristic optimizer capable of generating near-optimal solutions. PSO, however, is not constrained to convex optimization problems. The motivation of this work is to demonstrate a PSO implementation capable of achieving an optimal solution to the resource allocation problem. The capability of the PSO approach to reach an optimal solution suggests its potential for resource allocation in a network of heterogeneous applications where convex optimization methods do not apply.