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In this paper we address the challenge of multiuser scheduling in the downlink of Long Term Evolution (LTE) by bringing innovation in the concept of proportional fairness. We plug geometric average into the selection criterion of User Equipments (UEs) as opposed to widely used arithmetic average. We prove that the geometric average throughput converges to the solution of an ordinary differential equation,...
System latency is one key metric that guides LTE design. Shortening TTI by reducing subframe length along with backward compatibility design can bring significant latency gains for legacy LTE systems. In general, it is believed that the shorter TTI is, the more gain can be achieved. However, due to the hardware limitation as well as the implementation complexity, it is not easy for ultra-short TTI...
Internet of Things (IoT) can improve the lives of millions of people. In IoT the smart objects are converted from physical to virtual world to connect with Internet. The IoT enables smart objects to observe, identify, and understand the world without intervention of human-being (Machine-to-Machine communication: M2M). Due to the increasing interest of IoT, M2M, and wireless sensor applications the...
In LTE networks, even if two communicating UEs are closed enough, the traffic must go around core network. If Device-to-Device (D2D) communications used, two nearby UEs can directly exchange data, rather than passing core network to reduce loading of core network. However, D2D communications are not always gaining benefit. This paper proposes two mechanisms, namely Capacity-based scheme and Delay-based...
Long Term Evolution (LTE) holds the promise to enhance the capacity and speed of mobile communication by supporting Multimedia Broadcast/Multicast Services (MBMS) over a single frequency network (MBSFN), where numerous cells transmit an identical waveform that is synchronized in time for a specific time interval. For improving the performance of SFN, ultra-extended cyclic prefix duration has been...
One of the key building blocks of the newly emerging 5th generation (5G) wireless communication system are ultra dense small cells. In this paper, the system performance of such a deployment is studied for scenarios where there are individual deadlines to serve data packets. A proactive delay-minimizing scheduling method (PDMS) is proposed to minimize the number of dropped packets due to missed deadlines...
In anticipation of the increasing demand of wireless traffic, WiFi standardization efforts have recently focused on two key technologies for capacity improvement: multi-user MIMO and wider bandwidth. However, users experience heterogeneous channel orthogonality characteristics across sub-carriers in the same channel bandwidth, which prevents ideal multi-user gain. Moreover, frequency selectivity increases...
While implementing the idea of multiuser diversity for a scheduling scheme in a real time Orthogonal Frequency Division Multiplexing (OFDM) system, one is immediately confronted with two issues: fairness and delay. In the ideal situation when users' fading statistics are the same, the total capacity of the system as well as the throughput of individual users are maximized. In reality, the statistics...
In orthogonal frequency division multiplexing (OFDM) systems, such as long term evolution (LTE) and WiMAX, a codeword is transmitted over a group of subcarriers. Since the subcarriers see different channel gains in a frequency-selective channel, the modulation and coding scheme (MCS) of the codeword must be selected based on the vector of signal-to-noise-ratios (SNRs) of these subcarriers. Exponential...
This paper presents a multi-path delay commutator (MDC) FFT processor for high-speed. The proposed FFT processor can achieve a high throughput by using a parallel datapath scheme and a multi-path delay commutator structure. The proposed processor can provide a low hardware complexity and an efficient scheduling scheme of complex multiplications. The proposed efficient scheduling scheme can reduce...
This paper presents a performance evaluation on path diversity introduced in a wireless network established by unmanned aerial vehicles or unmanned aircrafts (UAs). One of usage scenarios of the wireless network established by UAs is establishment of a temporal communications instead of disrupted terrestrial networks due to a massive disaster. In order to evaluate system performance based on this...
In this paper, we consider the distributed scheduling problem for the OFDM based device-to-device (D2D) communications. In order to fully exploit the spatial diversity of the channel variation as well as provide access fairness for all D2D links, we propose a synchronous Distributed Opportunistic scheduling protocol under Fairness constraints (DO-Fast). DO-Fast incorporates the opportunistic scheduling...
Several wireless sensor network (WSN) applications will in the future be deployed for process control purposes which typically require timely data delivery. The main drawback with current WSNs is that they cannot guarantee predictable delay which is required in many applications. In this paper, we propose WirArb which is a new medium access control (MAC) protocol suitable for time-critical applications...
Adaptive pilot patterns offer high throughput gains. However, their application requires additional feedback. In this paper, we investigate the feedback requirements for adaptive pilot patterns applied in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing systems. The main goal is to support a wide range of Doppler spreads and Root Mean Square (RMS) delay spreads while keeping...
The interoperable capabilities between the mixed WLAN standards in the environment of hybrid network are subject to be discussed. In this case, the extended fiber link may achieve 21.7 km. Among the modulations and the access methods applied, it shows that the delay bound of 802.11g DSSS-OFDM 54 Mbps is reasonable, however, it offer the highest data rate.
In this paper, we propose an adaptive cross-layer radio resource allocation (CL_ARRA) scheme, which is compatible with the IEEE 802.16e-2005 Orthogonal Frequency Division Multiple Access (OFDMA) air interface. The scheme comprises two steps: dynamic subcarrier allocation (DSA) and dynamic power allocation (DPA). Using DSA and DPA, we obtain a cross-layer function to maximize the system throughput...
This paper investigates the tradeoff between throughput and feedback delay of limited feedback beamforming in indoor wireless channels with a practical MIMO-OFDM prototype. Past descriptions of this tradeoff are largely based on simplified models of the wireless channel. Unfortunately, wireless channel models may not accurately represent the complexities of a real wireless channel. Furthermore, system...
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