A Novel Energy Model for Renewable Energy-Enabled Cellular Networks Providing Ancillary Services to the Smart Grid

In this paper, we consider cellular networks powered by the smart grid (SG) and by local renewable energy (RE) sources. While this configuration promises energy savings, usage of cleaner energy, and cost reduction, it has some intrinsic complexity due to the interaction between the network operators and the SG. Motivated by the significant advancement in the SG, we consider the case where cellular networks provide the SG with ancillary services by replying to the grid's explicit requests to increase or decrease their grid consumption. We propose a new approach for configuring and operating base stations (BSs) to provide ancillary services. Based on real data, we model the energy state of a BS as a Markov chain taking into account the proposed energy management policy, randomness of SG requests, and RE generation. We use the model to evaluate the performance of the system, and to decide proper settings of its parameters in order to minimize the energy operational cost. The performance of our proposal is then compared against those of other approaches. Results show that important cost savings, with negligible degradation in quality of service, are possible when RE generation, SG patterns, and storage sizes are properly taken into account

A novel unequal error protection scheme for 3-D video transmission over cooperative MIMO-OFDM systems

Currently, there has been intensive research to drive three-dimensional (3-D) video technology over mobile devices. Most recently, multiple input multiple output (MIMO) with orthogonal frequency division multiplexing (OFDM) and cooperative diversity have been major candidates for the fourth-generation mobile TV systems. This article presents a novel unequal error protection (UEP) scheme for 3-D video transmission over cooperative MIMO-OFDM systems. Several 3-D video coding techniques are investigated to find the best method for 3-D video transmission over the error-prone wireless channels. View plus depth (VpD) has been found the best technique over other techniques such as simulcast coding (SC) and mixed-resolution stereo coding (MRSC) in terms of the performance. Various UEP schemes are proposed to protect the VpD signals with different importance levels. Seven video transmission schemes for VpD are proposed depending on partitioning the video packets or sending them directly with different levels of protection. An adaptive technique based on a classified group of pictures (GoP) packets according to their protection priority is adopted in the proposed UEP schemes. The adaptive method depends on dividing GoP to many packet groups (PG's). Each PG is classified to high-priority (HP) and low-priority (LP) packets. This classification depends on the current signal-to-noise ratio (SNR) in the wireless channels. A concatenating form of the rate-variable low-density parity-check (LDPC) codes and the MIMO system based on diversity of space-time block codes (STBC) is employed for protecting the prioritized video packets unequally with different channel code rates. For channel adaptation, the switching operations between the proposed schemes are employed to achieve a tradeoff between complexity and performance of the proposed system. Finally, three protocols for 3-D video transmission are proposed to achieve high video quality at different SNRs with the lowest possible bandwidth

On Adaptive Contention Resolution Schemes for IEEE 802.16 BWA Systems

According to the latest version of the IEEE 802.16 standard, the mandatory contention resolution method is the truncated binary exponential backoff, with the initial window size and the maximum window size controlled by the base station. However, the problem of choosing the right set of backoff parameters for the current network level remains unsolved and left as an open issue since this strategy might incur a high collision probability and the channel utilization could be degraded in congested scenario. In this paper, we propose two pragmatic adaptive algorithms, namely semi-dynamic and quasi-dynamic contention resolution schemes, that allow the base station to adjust its backoff window size based on current channel status. By controlling the size of backoff window according to varying network conditions, both schemes are able to achieve higher performance in comparison with the legacy IEEE 802.16 standard

Environmental friendly mobile radio networks: Approaches of the European OPERA-Net 2 project

International audienceReducing the overall environmental impact of mobile radio networks is a central factor in achieving improved mobile services whilst at the same time enabling a growing telecommunications industry in emerging markets. The OPERA-Net-2 (Optimising Power Efficiency in Mobile Radio Networks 2) project concentrates on this challenge, addressing both energy and material efficiencies of 3G, 4G and heterogeneous networks, while also considering the use of renewable energy sources. This paper presents an insight into the project after its first year and discusses research trends in `green communications networks' for the future