Reliable multicast and broadcast services in relay-based emergency communications

Despite the inherent support, the QoS performance of real-time Multicast and Broadcast Service (MCBCS) such as Mobile TV over TDD-OFDMA remains unclear. From the network operator's perspective, it is of paramount concern to understand the quality of the broadcast/multicast video and how many (mobile TV) can be supported with the required quality, together with respective design options of the network. In this paper, we attempt to understand various operating constraints and interdependencies between layers such as video traffic types, MAC scheduling schemes, link budget and channel characteristics, modulation coding schemes, OFDMA resource allocation methods and so on. Due to limited space, this paper only presents a high-level analysis concerning some of the key design issues stated above. This provides a good pre deployment reference for future network operators who wish to consider TDD-OFDMA scheme, particularly in the format proposed in IEEE802.16e-2005 as solution for delivering MCBCS.

Broadcast and multicast services (BCMCS) in CDMA2000 wireless telecommunications networks restrict high- quality multimedia services to their intended recipients by encrypting content. The air specification of BCMCS includes the advance encryption standard (AES) block cipher in the security layer of the broadcast protocol suite. We surveyed the AES block cipher algorithm and characterized the time it requires. We also profiled the execution time of each transformation that comprises the AES cipher. Drawing on these results, we proposed a analytic model that can predict the time required to decrypt encrypted contents at a mobile by considering cross-layer information, such as the characteristics of error control using Reed-Solomon coding in the MAC layer and varying conditions of the fading channel in the physical layer. This model will enable us to estimate the buffer size required to ensure seamless multimedia services.

The broadcast and multicast service will play a major role in the future wireless communication. The enhanced broadcast and multicast system (EBCMCS) is the evolution of cdma2000 EV/DO in the broadcast system, and can provide the point-to-multipoint broadcast service. In this paper, the quadrature PN spreading and de-spreading methods in the EBCMCS of cdma2000 EV-DO are investigated, and a quadrature PN de-spreading method with lower complexity is proposed. Also, its complexity is compared with the traditional method. Finally, it is proved that the proposed method has much lower complexity than the conventional one without degrading the effectiveness.

With the increasing capabilities of mobile terminals, the reception of mul-timedia content is becoming more and more attractive for customers. Im-proving high bandwidth provision enables 3G cellular systems to deliver such data to the end user. The 3G mobile experience is following a trend towards personalized services and applications which are used not only for voice communication but also for entertainment. Customers favour short video/audio clips rather than watching complete movies on their small screen. The deployment of new broadcasting networks like Digital Video Broadcasting - Handheld (DVB-H) results in large costs both in terms of capital as well as operating expenditure. Hence it is an enormous commer-cial risk for providers to install such systems. Multimedia Broadcast Multicast Service (MBMS) is considered a prom-ising technology to distribute multicast and broadcast services efficiently and at reasonable costs within existing 3GPP cellular networks. Enriched interactive multimedia services can be offered providing, for example, the latest news or publishing the current top ten music video clips. The trend towards user generated content distribution which is observed in the Inter-net will no doubt increase the number of available services and content. Set against this background of predicted increase both in terms of num-ber of services/content and users, the competition for limited resources will only intensify. MBMS is regarded as a bearer technology and not a com-plete service provisioning system therefore efficient scheduling for optimal utilization of radio and network resources is essential. Scheduling in MBMS comprises several levels of abstraction which require different strategies. This chapter presents several scheduling techniques and ap-proaches for MBMS content distribution. It explains the concepts of (1) a Dynamic MBMS Resource Scheduler located in the Radio Access Network (RAN), (2) a Carousel Service Scheduling approach and (3) means for an optimal scheduling of Multicast Streaming Services. The latter two sched-ule services and content while the first deals with IP packets.

In this article, we design and demonstrate a signaling architecture for multicast and broadcast services over a laboratory-emulated worldwide interoperability for microwave access (WiMAX) network. WiMAX is a broadband wireless access technology which includes different quality of service levels. Currently, a significant research effort focuses on data transmission optimization and mobility support for multicast and broadcast services. Our proposal is fully IP-based, and the relevant signaling architecture is modular in all its entities and extensible to other, non-WiMAX, IP access networks. We specifically address the non-trivial support of multicast services, which has been demonstrated through a prototype implementation of our proposal for an Internet protocol television (IPTV) service. This prototype has been implemented by using open source technologies and its signaling is orchestrated by a JAIN SLEE server. The results obtained show that the implemented system is scalable, can achieve both high signaling throughput and low service latency, and has a signaling overhead lower than similar IMS-based solutions.

Delivering geographically segmented local content remains one of the key challenges in Single Frequency Networks (SFNs). By leveraging Layered Division Multiplexing (LDM), Local Content Insertion (LCI) can be achieved through Geographically Segmented Localcasting (GSL) for both multimedia and datacasting applications. This paper introduces a solution where region-wide broadcast services are carried by the Core Layer (CL) of the LDM, while local content is transmitted through the Enhancement Layer (EL). This approach also benefits network design and transmitter deployment, as new transmitters can be positioned freely within the intended broadcast service area. Each additional site enhances the reception quality of the regional component (LDM CL) while simultaneously delivering geographically specific multimedia and datacasting services to its local coverage zone. Since the localcasting signal on the EL operates at a lower transmission power, co-channel interference among local transmitters is minimized. A co-channel interference mitigation technique, Iterative Joint Detection and Decoding (IJDD), is also introduced. The paper outlines a roadmap for deploying LCI/GSL systems. Leveraging LDM enables any terrestrial television platform to adopt this approach in SFN or High-Power High-Tower (HPHT) configurations while remaining compatible with existing receivers. Furthermore, any cell-based wireless systems (5G/6G) can exploit this method, efficiently integrating broadcast, multicast, and unicast service delivery.

The unique advantages of UAV with good maneuverability, ease of deployment and control can effectively meet the needs of emergency communications network construction. In order to solve the problem of effective communication security in large-area rescue areas, the idea of using multiple UAVs to construct an emergency relay network was proposed. Under the given mission area, the deployment of this network was studied. First of all, in order to fit the practical application, consider the channel fading to model the UAV coverage area, and propose a UAV relay network model based on connectivity probability. Then, according to the needs of emergency communication scenarios, from the perspective of simplifying the algorithm time complexity and guaranteeing the accuracy of the solution, an algorithm based on simulated annealing for deployment of UAV relay network is proposed. The simulation results show that the proposed algorithm has strong effectiveness and stability and can be applied to the deployment of UAV relay network in the context of emergency communications.

A cause and effect relationship model for location of temporary shelters in disaster operations management

Mobile multihop relay (MMR) networks based on the IEEE 802.16j standard are able to extend the service area as well as improve the performance of mobile WiMAX networks. We present an optimization framework for jointly optimizing the placement and bandwidth reservation for a relay station in an MMR network. The objective of this framework is to maximize utility of the MMR network service provider. The decision on the placement of the relay corresponds to finding the best location for the relay station under uncertainty about the number of active users in the extended service area of the MMR network. This uncertainty could be due to random connection initiation and termination by the users or due to the random arrivals and departures of the mobile subscriber stations in the extended service area. However, this decision on relay placement may not achieve the highest utility when the users dynamically adapt their decisions on whether to transmit directly to the base station or transmit through the relay station. In this scenario, optimal decision on bandwidth reservation by the relay station needs to be made (over a relatively shorter period of time) which takes the dynamics of users' decision into account. The placement of the relay station (over a relatively longer period of time) can then be optimized based on the optimal bandwidth reservation. A stochastic programming formulation and a Markov decision process formulation are used to obtain the long-term and short-term optimization solutions, respectively.

Mobile ad-hoc networks are making a new class of mobile applications feasible. They benefit from the fast deployment and reconfiguration of the networks, are mainly characterized by the need to support many-to-many interaction schema within groups of cooperating mobile hosts and are likely to use replication of data objects to achieve performances and high data availability. This strong group orientation requires specialized solutions that combine adaptation to the fully mobile environment and provide the adequate level of fault tolerance. In this paper, we present the reliable broadcast protocol that has been purposely designed for mobile ad-hoc networks. The reliable broadcast service ensures that all the hosts in the network deliver the same set of messages to the upper layer. It represents the building block to obtain higher broadcast and multicast services with stronger guarantees and is an efficient and reliable alternative to flooding. The protocol is constructed on top of the wireless MAC protocol, which in turn sits over the clustering protocol. It provides an exactly once message delivery semantics and tolerates communication failures and host mobility. Temporary disconnections and network partitions are also tolerated under the assumption that they are eventually repaired, as specified by a Liveness property. The termination of the protocol is proved and complexity and performance analyses are also provided.

Cellular phone networks are often paralyzed after a disaster, as damage to fixed infrastructure, loss of power, and increased demand degrade coverage and quality of service. To ensure disaster victims and first responders have access to reliable local and global communication, we propose EmergeNet, a portable, rapidly deployable, small-scale cellular network. In this article, we describe EmergeNet, which addresses the challenges of emergency and disaster areas. EmergeNet provides free voice calling and text messaging within a disaster area, and enables users of unmodified GSM handsets to communicate with the outside world using the Skype VoIP network. We evaluate EmergeNet's ability to provide robust service despite high load, limited bandwidth, and software or hardware failures. EmergeNet is uniquely well suited to providing reliable, fairly allocated voice and text communication in emergency and disaster scenarios.

This article investigates the issue of cooperative real-time trajectory design for multiple unmanned aerial vehicles (UAVs) to support emergency communication in disaster areas. To restore communication links rapidly between mobile users (MUs) and the ground base stations, UAVs equipped with both radio frequency (RF) modules and free space optics (FSO) modules are utilized as relay nodes. Given the challenges of setting up a central controller for the UAVs and the urgency of emergency communication, the trajectory design problem for these UAVs is formulated as a distributed cooperative optimization problem. Based on the enhanced <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -mean algorithm and multiagent PPO (MAPPO) algorithm, a cooperative trajectory design method, abbreviated as KMAPPO, is proposed for the UAVs to minimize interaction overhead and optimize deployment efficiency. Compared to the state-of-the-art deep reinforcement learning (DRL) methods, simulations reveal KMAPPO’s superior performance. It converges 32% faster, boosts RF allocation efficiency, and augments FSO communication backhaul capacity.

Relay stations can be deployed in a wireless network to extend its coverage and improve its capacity. In this paper, we study a scheduling problem in OFDMA-based wireless relay networks with consideration for multi-user diversity, channel diversity and spatial reuse. First, we present a Mixed Integer Linear Programming (MILP) formulation to provide optimum solutions. It has been shown by previous research that performance of a wireless scheduling algorithm is usually related to the interference degree delta, which is the maximum number of links that interfere with a common link but do not interfere with each other. Therefore, we then show that the interference degree delta is at most 4 for any 2-hop relay network and 14 for any general h-hop (h >; 1) relay network. Furthermore, we present a simple greedy algorithm for the scheduling problem and show it has an approximation ratio of 1/(1+δ), which leads to an approximation ratio of 1/5 for the 2-hop case and 1/15} for the general case. In addition, we present three heuristic algorithms, namely, the weighted degree greedy algorithm, the Maximum Weighted Independent Set (MWIS) algorithm and the Linear Programming (LP) rounding algorithm, to solve the scheduling problem. Extensive simulation results have showed that the LP rounding algorithm performs best and always provides close-to-optimum solutions. The performance of the simple greedy algorithm is comparable to that of the other algorithms.

In IEEE 802.16j-based relay networks, frequency reuse by RS(Relay Station)s and BS(Base Station) is considered as a way to improve the frequency utilization. However, since the same frequency band is used by RSs and BS, MS located in the middle between neighboring transmitting stations suffer severe interference or even outage. This co-channel interference within a cell is a major bottleneck in providing uniform QoS(Quality of Service) to all the MSs regardless of their locations. We propose a simple and effective solution to this problem. When two or three transmitting stations interfere with each other at the receiving MSs considerable (beyond given thresholds), we require the transmitting stations to transmit the signals again (shifted by 180 for the two stations or shifted by 120 and 240 degrees for the three stations). The receiving MSs combine these retransmitted signals with original signals to cancel the co-channel interference. Transmitting the same signals two of three times incurs overhead in terms of resources. However, we derive thresholds which determine whether our scheme is beneficial or not to individual MSs. Since our scheme is used only for the chosen MSs, it improves known schemes with frequency reuse in terms of throughput and fairness. Our scheme excels the known schemes (orthogonal allocation and the overlapped allocation) by 113% and 34.1, respectively, in terms of throughput. Fairness is also improved by 60.5% against the overlapped allocation scheme.

In this paper, we propose a joint resource allocation, routing, and connection admission control (CAC) scheme for uplink transmission in orthogonal frequency division multiple access (OFDMA) relay networks with cooperative relaying. For cooperative relaying, relay station can relay uplink data from mobile station (MS) to base station with cooperation of the MS using transmit diversity. Transmit diversity can be achieved by virtual MISO via distributed space---time coding. The proposed scheme jointly allocates OFDMA resources and selects path for each user with CAC to maximize the upink throughput of cooperative OFDMA relay networks. The basic OFDMA resource unit is considered as a resource element which is one subcarrier over one OFDMA symbol. An efficient multi-choice multi-dimensional knapsack (MMKP) algorithm is presented for the proposed scheme. The proposed MMKP algorithm provides a unified framework which is applicable to OFDMA networks with and without cooperative relaying. We evaluate the performance of the proposed scheme with and without cooperative relaying in a hilly terrain with heavy tree density by using OPNET-based simulation. We show that the cooperative relaying improve the uplink system throughput compared with non-cooperative relaying, and the proposed scheme outperforms the conventional link quality-based scheme in both cooperative and non-cooperative relay networks.