Energy saving in multi-standard mobile terminals through short-range cooperation

Multi-standard mobile terminals (MTs) are the trend of current and future mobile devices for taking advantage of heterogeneous integration of wireless access networks and providing ubiquitous connectivity and better quality of service. Holding multiple active interfaces, however, incurs significant power consumption burdens to MTs. This not only increases the carbon footprint of MTs but also makes the batteries of MTs deplete rapidly. Consequently, mobile users may have to relentlessly look for power outlets to charge their devices, which may threaten their true mobility freedom. To this end, in this article, we propose a promising approach based on coalition formation game and inter-terminal cooperation. Our innovative approach motivates MTs to cooperate, while addressing the issue of isolating selfish players. MTs assess radio channels and disseminate the acquired information as well as their available resources to sketch a global view of the radio environment. Based on this view, coalitions are formed whenever energy saving is foreseeable. Within a coalition, MTs pool their resources and perform their tasks cooperatively to maximize their energy efficiency. Simulation results validate that the proposed approach can effectively double the battery lifetimes of MTs, while successfully eliminating selfish players from cooperative groups.

This work addresses the problem of optimized content distribution over wireless networks with cooperation among mobile terminals. The mobile terminals are optimally divided into groups where each group internally cooperates by downloading and exchanging a common content from the base station in order to minimize the total energy consumed by the mobile terminals. We assume unicasting transmissions from the base station and multicasting transmissions among the mobile terminals. It is well known that the optimal content multicasting problem that minimizes the mobile terminal's energy consumption is an NP-hard problem. Consequently, several heuristic algorithms have been proposed in the literature that take into account only few network parameters to simplify the energy minimization problem. The main contributions of this work are the following. First, we derive the optimal energy consumption expression in a grid network as a function of the optimal cooperative group size. Second, we study the effect of several important network parameters on energy consumption; these include the transmission rates and the energy consumed per unit time during data transmission and reception. Results show that cooperation leads to notable reduction in energy consumption compared to the non-cooperative case. Besides, we demonstrate that several network parameters have nearly equivalent importance; consequently, energy-aware content distribution protocols should take into account multiple network parameters to obtain more efficient solutions.

On resource scheduling and interference mitigation in distributed massive-MIMO wireless orientations via NOMA transmission

This paper addresses the problem of energy-aware multihop cooperation among the mobile terminals (MTs) that cooperatively download a common content from a wireless network. The base station (BS) unicasts or multicasts the content to selected MTs that, in turn, either unicast or multicast it to other MTs, forming a multihop ad hoc network with a predefined maximum allowed number of hops. This paper presents the optimization formulations whose solution gives the exact optimal set of receiving MTs from the BS, the optimal multihop ad hoc network, and the optimal unicasting and multicasting transmission bit rates that minimize the total energy consumption of the MTs. Second, a simplified multicasting formulation is proposed that has a close-to-optimal performance with notably lower computational complexity. Third, interference avoidance among the transmitting MTs is considered. For each presented formulation, the complexity is identified, and results show that some formulations can be efficiently solved for medium network sizes, while others are more computationally complex. Thus, polynomial-time heuristic solutions are presented that have close-to-optimal performance. Results demonstrate remarkable energy consumption reduction gains and wireless resources savings under various network scenarios.

It is envisaged that next generation wireless networks (NGWN) will be heterogeneous, consisting of multiple radio access technologies (RATs) coexisting in the same geographical area. In these heterogeneous wireless networks, mobile terminals of different capabilities (heterogeneous terminals) will be used by subscribers to access network services. We investigate the effect of using heterogeneous mobile terminals (e.g. single-mode, dual-mode, triple-mode, etc.) on call blocking and call dropping probabilities in cooperative heterogeneous wireless networks. We develop analytical models for heterogeneous mobile terminals and joint radio resource management in heterogeneous wireless networks. Using a two-class three-RAT heterogeneous wireless network as an example, the effect of using heterogeneous terminals in the network is evaluated. Results show the overall call blocking/dropping probability experienced by subscribers in heterogeneous wireless networks depends on the capabilities of mobile terminals used by the subscribers. In the worst case scenario, when all subscribers use single-mode mobile terminals, each subscriber is confined to a single RAT and consequently, joint radio resource management in heterogeneous wireless network has no improvement on new call blocking and handoff call dropping probabilities. However, in the best case scenario, when all subscribers use three-mode terminals, new class-1 call blocking probability decreases from 0.37 (for 100% single-mode terminals) to 0.05, at the arrival rate of 6 calls per minute. New class-2 call blocking probability also decreases from 0.8 to 0.52. Similarly, handoff class-1 call dropping probability decreases from 0.14 to 0.003, and handoff class-2 call dropping probability decreases from 0.44 to 0.09.

In Mobile Cloud Computing (MCC), the data processing and storage for Mobile Terminals (MTs) will be provided on the remote cloud. This technology can extend battery lifetime and increase processing power, but there are several significant issues such as the problem of dead spots or coverage holes. However, this problem is ignored in existing energy saving algorithms and mobile cloud platform design schemes. As a result, the service delay or disconnection would be caused. To this end, we address the problem of dead spots or coverage holes, and propose a energy saving algorithm based on a user-provided resources platform in this paper, called Task Offloading using Self-organized Criticality (TOSOC). This user-provided resources platform could provide the processing capacity based on a cluster of MTs when they are out of service of MCC. Considering the energy limitation of MTs, we propose a energy saving algorithm in user-provided resources platform with a service delay constraint. Numerical results validate the rightness and effectiveness of our proposed TOSOC, and the energy saving with requirement of service delay are proven.

In this paper, we formulate and solve a weighted-sum transmitter and receiver energy minimization (WSTREMin) problem in the downlink of an orthogonal frequency division multiplexing (OFDM) based multiuser wireless system. The proposed approach offers the flexibility of assigning different levels of importance to base station (BS) and mobile terminal (MT) power consumption, with the BS being connected to the grid and the MT relying on batteries. To obtain insights into the problem, we first consider two extreme cases separately, i.e., weighted-sum receiver-side energy minimization (WSREMin) for MTs and transmitter-side energy minimization (TEMin) for the BS. It is shown that Dynamic TDMA (D-TDMA), where MTs are scheduled for single-user OFDM transmissions over orthogonal time slots, is the optimal transmission strategy for WSREMin at MTs, while OFDMA is optimal for TEMin at the BS. As a hybrid of the two extreme cases, we further propose a new multiple access scheme, i.e., Time-Slotted OFDMA (TS-OFDMA) scheme, in which MTs are grouped into orthogonal time slots with OFDMA applied to users assigned within the same slot. TS-OFDMA can be shown to include both D-TDMA and OFDMA as special cases. Numerical results confirm that the proposed schemes enable a flexible range of energy consumption tradeoffs between the BS and MTs.

Performance analysis of dual connectivity in control/user-plane split heterogeneous networks

Energy saving and the development of renewable energies already form part of the daily discourse in our society. Climate change and the environmental problems arising from it affect all of us on the planet. In view of the recent energy supply crisis in Europe and in line with the EU's Sustainable Development Goals, it is necessary to accelerate the ecological transition. This means, among many other things, encouraging energy efficiency and energy savings. This research is based on the EURONET 50/50 max project, which applied a methodology with no upfront capital outlay, but based on changing user habits to save energy in educational buildings. It was carried out in twelve educational centres of the Spínola Foundation throughout Spain. Significant reductions in energy and water consumption were achieved. The maximum reduction obtained in water consumption was 29%, 24% in electricity consumption and 33% in heating consumption. The average reduction in consumption obtained was 13% compared to 11% achieved in the 50/50 max project. It was concluded that, on the journey to optimising our energy consumption, working on patterns of usage is fundamental, raising awareness and involving users in order to give rise to permanent processes over time, gradually reversing climate change.

We propose an energy-efficient L2 transmission scheme using the protocol property of Non-Real-Time (NRT) traffic in IEEE 802.11 WLANs. Typically, the collision probability at the Access Point (AP) and the retransmission probability at the Mobile Terminals (MTs) may increase significantly when the number of served MTs constantly increases. As these probabilities are increasead, energy efficiency in WLANs is decreased. In order to reduce the retransmission attempts, the proposed scheme allocates the maximum backoff count to an MT which is using NRT traffic. Thus, we propose a new energy consumption metric for retransmission while comparing it to the Distributed Coordination Function (DCF) by numerical analysis in a saturated network situation.

Energy bills are on the rise and with the recent attention to saving the global environment. Saving energy (minimizing energy consumption) is becoming a standard issue for all industrial and commercial applications. Moreover, provisioning of quality of service (QoS) for multimedia traffic in wireless networks is complicated due to user mobility and limited wireless resources. Bandwidth (throughput) and hop count and are the important parameters in QoS requirements. In this article, a novel QoS constrained minimum power cellular ad hoc augmented network (QCMP CAHAN) architecture is proposed for next generation wireless networks. The QCMP CAHAN architecture is proposed to find the optimal minimum power route under bandwidth and hop-count constraints (QoS constraints). The QCMP CAHAN has a hybrid architecture, in which each mobile terminal (MT) of CDMA cellular networks has ad hoc communication capability. The QCMP CAHAN is an evolutionary approach to traditional cellular networks. We show that the total energy consumed by the MTs is lower in the case of QCMP CAHAN than in the case of traditional cellular networks. As the ad hoc communication range of each MT increases, the total transmitted energy in QCMP CAHAN decreases. However, due to the increased number of hops involved in information delivery between source and destination, the end-to-end delay increases. The maximum end-to-end hop count will be limited to a specified tolerable value, and QCMP CAHAN has ability to adapt to various hop-count constraints for different services. A MT in QCMP CAHAN will not relay any message when its ad hoc communication range is zero, and if this is the case for all MTs, then QCMP CAHAN reduces to the traditional cellular networks. Moreover, the bandwidth constrained problem in QCMP CAHAN is described as a nonlinear programming problem to minimize the total power consumption. We solved the bandwidth constrained problem in QCMP CAHAN by allocating optimum traffic rates on different routes between source and destination.

Network operators have a keen interest on knowledge about the coverage of their network in indoor environments. Mobile users use the mobile network indoors about 80% of their time compared to outdoor. To identify coverage gaps it requires precise knowledge about the environment itself and the whereabout of the mobile terminal. This knowledge is lacking for two reasons. First the network driven time-based location solutions of the user is rather inaccurate for reasons like multi-path propagation or inaccurate synchronization. Furthermore, the indoor environment itself remains normally unknown for the network operators. However, the high density of users in indoor environments invites to explicitly use the potential peer-to-peer links between mobile terminals themselves. This would allow to position the mobile terminals relatively to each other. Positioning by using the peer-to-peer link is called cooperative positioning. This paper investigates the behavior of a distributed particle filter using nomadic movement behavior of the tracking objects.

The objective of the MEMO project is to design, integrate and operate applications which utilise interactive DAB services, i.e. combining the existing GSM mobile telecommunications network and the Digital Audio Broadcasting system. A first trial with this platform for mobile multimedia services was performed to demonstrate the results achieved after one year of work and cooperation of the European partners involved. The MEMO architecture comprises DAB transmitter equipment and PC-based terminals. During the specification of the first generation prototype and the software/hardware development the following results were achieved: Infrastructure and transmitter equipment (Specification and implementation of a protocol for information interchange between contents providers and the DAB network; design and implementation of the multi-network server (MNS) with an interface to the DAB-network-server (DNS) to feed the DAB transmitter; set-up of a DAB test transmitter at CCETT, Rennes; specification of a protocol for broadcasting Multimedia data on DAB) and Terminal (development of prototype DAB receivers with a data interface and PC plug-in card, notebook PCs and interface equipment to connect the PCs to the DAB receiver for data transfer at data rates up to 256 kbit/s; implementation of the GSM interaction channel between the mobile terminal and the MNS; definition and partial implementation of Application Programming Interfaces (APIs); development of terminal software for the network/system/application service layer and adaptation of publishing and construction industry applications to demonstrate mobile, interactive services). For the trial, the transmission chain from GSM request to DAB download was successfully completed and operated, including the connection between information provider and network operator. Three interactive applications were implemented and tested — a specialised software for the building construction industry, a system to download issues of a newspaper and a general software to transmit data objects — representing the contrary edges of services MEMO is targeting. Thus, the approach of interactive mobile services at high data rates was presented for the first time to potential customers and users providing valuable results.

Mobile Termination, Network Externalities, and Consumer Expectations

Delay tolerant networks (DTNs) are mobile wireless networks that are characterized by frequent partitions and potentially long message delivery delays. Such networks have the potential for use in important application environments where en- ergy sources are limited. Therefore, efficient power management mechanisms are necessary to allow these networks to operate over a long period of time. In this paper, we leverage the observation that many DTNs are characterized by sparse connectivity, pro- viding the opportunity to save energy by aggressively disabling node radios (sleeping). The major challenge is to balance sleeping periods with wake-up periods so that valuable and infrequent communication opportunities between nodes are not missed. We develop a power management framework that allows a node to save energy while missing few communication opportunities. The framework is tailored to the available knowledge about network connectivity over time. Further, the framework supports an explicit tradeoff between energy savings and connectivity, so that network operators can choose, for example, to conserve energy at the cost of reduced message delivery performance. We evaluate our mechanisms using ns-2 simulations. Our results show that our power management mechanisms consume from 10% to 50% of the energy expended when the network operates without power management. These energy savings come at the cost of some performance degradation when available knowledge is incomplete, though our tuning parameter allows a rich set of tradeoffs between energy consumption and performance.