| 1. |
- Ahsin, Tafzeel Ur Rehman, et al.
(author)
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Energy Efficiency using Cooperative Relaying
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 1698-1702
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Conference paper (peer-reviewed)abstract
- The rising demand for the high data rates in the future cellular systems, is directly linked with the power consumption at the transmitting nodes. Due to the various economical and environmental factors, it is becoming difficult to maintain the current rate of power consumption per unit of data, for the upcoming generations of the cellular systems. This has shifted the focus of many researchers towards the energy efficiency aspect of the cellular systems and power consumption has become an important design parameter in the recent works. In this article, we propose the use of cooperative communications using low cost fixed relays, in order to reduce the energy consumption at the transmitting nodes for a given quality of service requirement. It has been investigated that, how different factors, such as cell radius, relay position, number of relays and target data rate effects the area energy consumption for the different relaying schemes. It has been shown that, the cooperative relaying schemes along with adaptive resource allocation provides minimum energy consumption along with the better coverage as compared to the non adaptive cooperative relaying schemes.
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| 2. |
- Brandt, Rasmus, 1985-, et al.
(author)
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Wideband MIMO Channel Diagonalization in the Time Domain
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 1958-1962
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Conference paper (peer-reviewed)abstract
- Methods for spatially diagonalizing wideband multiple-input multiple-output channels using linear finite impulse response (FIR) filters are investigated. The PSVD approach by applying the PQRD-BC algorithm for approximate singular value decomposition (SVD) of polynomial matrices is compared to the approach of performing a set of conventional SVDs in the Discrete Fourier Transform (DFT) domain, in terms of complexity and approximation error. Reduced order filters, based on the DFT-SVDs, are then obtained by optimizing the phases of the filters. Applying the phase optimized filters as linear filters then forms a benchmark on the accuracy attainable for any PSVD factorization, for the given filter length. Simulations show that the DFT-SVD method has significantly lower complexity than the PSVD by PQRD-BC, but results in higher order filters. On the other hand, the PSVD by PQRD-BC yields filters which are close to being perfectly unitary for all frequencies. To achieve good performance, the reduced order filters are around one order of magnitude longer than the channel impulse response length. Therefore there is no gain in performing time domain diagonalization using a polynomial SVD, compared to using a multicarrier solution.
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| 3. |
- Cai, Tao, et al.
(author)
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Design of layered radio environment maps for RAN optimization in heterogeneous LTE systems
- 2011
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In: 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2011). - Piscataway, NJ : IEEE Communications Society. - 9781457713484 ; , s. 172-176
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Conference paper (peer-reviewed)abstract
- In this contribution a layered radio environment map (REM) architecture is designed and applied in the framework of radio-access network optimization for heterogeneous LTE systems that comprise both macrocells and femtocells. We define layer as the hierarchical representation of a geographical area. In each layer, different instances of the same architectural block will have different spatial/temporal granularities, associated with network functionalities. The effectiveness of the proposed architecture to support LTE functions like automatic neighbor relation (ANR) and minimization of drive tests (MDT) is discussed. In addition, we present the benefits of using such architecture in the implementation of these functions along with its potential to bring performance gains
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| 4. |
- Dwivedi, Satyam, et al.
(author)
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A Wideband Interference Power Estimator using a 1-bit Quantizer
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 515-519
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Conference paper (peer-reviewed)abstract
- This paper proposes a power estimation methodology which presents low complexity when implemented in hardware. Power estimation is done in digital and the radio signals are digitized using a 1-bit quantizer. An algorithm to estimate power is proposed. Power estimation of the signal is done while varying the threshold of the 1-bit quantizer. It is also shown that the proposed architecture can be used to estimate power of wideband radio channels.
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| 5. |
- Girnyk, Maksym, 1984-, et al.
(author)
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Myopic Multi-Hop Transmission Strategies in Layered Wireless Networks
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 1763-1767
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Conference paper (peer-reviewed)abstract
- A layered wireless network is considered, where information is transmitted in a multi-hop MIMO-like fashion from the source node layer through several intermediate layers of nodes before reaching the sink node layer. Analog network coding is investigated as the network transmission strategy, exploiting the inherent superposition features of the wireless channel. A general myopic transmission protocol is proposed, allowing overhearing across several layers. Special cases are investigated in terms of diversity and bit error rate when using different types of linear detectors. Conditions for successful decoding of all source node messages at each sink node are derived.
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| 6. |
- Girnyk, Maksym, 1984-, et al.
(author)
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Optimal Power Allocation in Multi-Hop Cognitive Radio Networks
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE conference proceedings. - 9781457713484 ; , s. 472-476
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Conference paper (peer-reviewed)abstract
- Optimal power allocation in a multi-hop cognitive radio network is investigated. Information transmitted from the source passes through several wireless relay nodes before reaching the destination. At each hop, the received signal is decoded, re-encoded and retransmitted to the following node. Transmissions at every hop are overheard by nearby nodes and therefore cause interference. We study optimal power allocation strategies that maximize the end-to-end throughput of the network under the constraint of strictly limited interference to external users. We show that for networks that can be modeled as a line topology the optimal solution is achieved when the capacities of every intermediate link are equal and the interference power constraint is satisfied with equality. High-and low-SNR approximations that simplify the problem of finding the optimal power allocation are presented as well. The numerical results show good performance compared to schemes with equal power allocation.
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| 7. |
- Kang, Du Ho, et al.
(author)
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Cooperation and Competition between Wireless Networks in Shared Spectrum
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 284-288
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Conference paper (peer-reviewed)abstract
- As the regulation in wireless communications is moving toward a more flexible and efficient way of managing radio spectrum, it is envisaged that multiple small-sized cellular networks owned by different operators will operate in close vicinity on shared spectrum. This brings a new interference environment where a cell is interfered by not only base stations in own network but also those in other networks. These networks may compete for their own utilities in a selfish manner or cooperate in order to minimize the mutual interference. Since a cooperation between the networks requires a business-wise agreement or extra infrastructure cost, the operators have to identify how much they will benefit from the cooperation. In this paper, we compare the effects of competition and cooperation between the cellular networks. The competition and cooperation are modeled as a transmit power control in downlink. It is observed that the cooperation in an average sense gives better network utility. However, as the network size increases, the cooperation gain diminishes significantly. Furthermore, the marginal separation of network deployments, e.g., indoor deployments in adjacent buildings, can notably shrink the cooperation incentive.
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| 8. |
- Liu, Liang, et al.
(author)
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Low Complexity Soft-Output Signal Detector for Spatial-Multiplexing MIMO System
- 2011
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In: 2011 IEEE 22ND INTERNATIONAL SYMPOSIUM ON PERSONAL INDOOR AND MOBILE RADIO COMMUNICATIONS (PIMRC). - 9781457713484 ; , s. 1718-1722
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Conference paper (peer-reviewed)abstract
- This paper presents a cost-efficient soft-output signal detector design solution targeting on the spatial-multiplexing MIMO system. The detector achieves low hardware cost and near-optimal detection performance based on the modification to the fixed-complexity sphere decoder (FSD) using several implementation-oriented algorithm-level improvements, which are early-pruning with polygon-shaped constraint, symbol-level bit-flipping, and l1-norm approximation. To evaluate the proposed method, we implement the MIMO detector in a 65-nm standard VT CMOS technology. The core area is 0.14 mm2 with 69 K equivalent gates, representing a 60% hardware-resource saving to the state of art in the open literature. The detecting throughput is up to 1.5Gb/s at 250-MHz clock frequency and 1.2-V supply. The normalized energy consumption of 36.4 pJ/b is shown to be the most energy-efficient design compared with other soft-output detectors.
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| 9. |
- Lu, Lu, et al.
(author)
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Efficient Scheduling for Relay-Aided Broadcasting with Random Network Codes
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 1815-1819
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Conference paper (peer-reviewed)abstract
- We investigate efficient scheduling algorithms for a relay-aided broadcasting system using random network codes, where our objective is to maximize the transmission efficiency. The broadcast from a base-station (BS) is divided into an information phase and a redundancy phase, where the half-duplex relay assists in the redundancy phase. Time-division transmission is used over packet-erasure channels, where the erasure probabilities of the BS-to-relay and relay-to-user links are lower than the BS-to-user links. Following the information phase, each user provides feedback on the status of received packets to the BS and the relay, which in turn both generate redundancy packets for the redundancy phase. To improve efficiency, we formulate a scheduling problem for the transmissions of redundancy packets from the BS and the relay. We consider two scenarios; namely instantaneous feedback after each redundancy packet, and feedback after multiple redundancy packets. In the first case the schedule is determined using a greedy algorithm, while in the second case the schedule is determined using dynamic programming. To determine the performance with instantaneous feedback, we develop an analytic approach based on a Markov chain. Numerical results show that the transmission efficiency of the dynamic programming algorithm is close to the performance of the greedy algorithm, but requires significantly less feedback.
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| 10. |
- Lungaro, Pietro, et al.
(author)
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Application-centric Content Delivery Schemes for Future Wireless Networks
- 2011
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In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 2128-2132
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Conference paper (peer-reviewed)abstract
- The apps paradigm is rapidly changing the way in which content is transferred and consumed in mobile networks. Currently, the traffic loads generated by apps are mostly provided as Over-The-Top (OTT) services, essentially transparent to the cellular network operators, while some of the content is delivered and updated in user terminals through "background transmissions", without user intervention. With increasing traffic volumes, associated to richer content and more advanced devices, the apps paradigm might create severe system inefficiencies. In this paper we explore a number of apps based content delivery methods and investigate their performances on multiple relevant dimensions,such as: terminal energy consumption, time for accessing in-apps content and their impact on the user experience associated with other mobile data services. The proposed methods include opportunistic content pre-fetching and are characterized by different degrees of context-awareness. One approach considers only context information at the individual user terminals, while another one includes network context information and assumes that content distribution coordination is performed by the network operators. The results show that when one is increasing the numbers of apps, whose content needs to be simultaneously maintained updated, only the operator-driven approach can be feasible, mainly from an energetic perspective. However, for a small number of maintained apps, pre-fetching schemes are superior to standard "on-demand" content delivery solutions, suggesting that pre-fetching should be limited only to the subset of terminal apps with higher user access probabilities.
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