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In this paper, we address the problem of user scheduling in downlink coordinated multi-point transmission (CoMP) systems, where multiple users are selected and then served with zero forcing beamformer simultaneously by several cooperative base stations (BSs). To reduce the enormous overhead led by obtaining full channel state information at the transmitter, a low-feedback user scheduling method called...
In this paper we propose a game-theoretic approach for characterizing WiFi network performance in presence of intelligent nodes employing cognitive functionalities. We assume that a cognitive WiFi node is aware of its application requirements and is able to dynamically estimate the network status, in order to dynamically change its access strategy by tuning the contention window settings. We prove...
The purpose of this paper is to reduce the complexity of scheduling scheme for OFDMA/SDMA system with multimedia traffic. To achieve this purpose, we propose a low-complexity beamforming-based scheduling (LCBS) scheme to solve the multi-dimensional (space, time, and frequency) radio resource allocation problem in OFDMA/SDMA systems. By utilizing a semi-orthogonal user selection (SUS) algorithm, the...
This paper presents a low complexity receiver for downlink orthogonal frequency division multiple access (OFDMA) systems. We consider the comb-type subcarriers assignment for a resource block. Based on this arrangement, a resource block could be demultiplexed at the user equipment without performing fast Fourier transform(FFT) on one OFDMA symbol. The inter-symbol interference(ISI) resulted from multipath...
The problem of resource allocation (RA) in a downlink OFDMA system with minimum user rate requests is examined under the realistic scenario of partial (imperfect) channel state information (CSI) at the base station. The challenge in this setting is the non-zero probability of outage events which may lead to significant performance degradation if algorithms assuming perfect CSI are utilized. In this...
With the advent of new applications, one of the primary applications supported in downlink cellular systems is streaming video. QoS for streaming video entails data transmission to the mobile stations with limited latency and limited jitter. This requirement on latency and jitter can be mapped to the number of yet-to-be-played packets in a mobile station's buffer, to always be above a certain minimum...
Femtocell is a small base station with low power which can be installed by users to get better data rate in the indoor environment. The power control scheme of the femtocell BS is the most important issue in the femtocell implementation but there still exist deadzones if macrocell users are located very close to the femtocell. In this paper, we have proposed a new frame structure for the IEEE 802...
In this work we consider the optimization of the power assigned to the user streams, in a coordinated base station downlink environment, when zero-forcing is employed to remove interference among users. Two schemes based on the waterfilling technique are proposed and compared to the optimal solution, which can be obtained numerically, by using convex optimization. We show that the proposed schemes...
In this paper, a new opportunistic feedback and user selection protocol is proposed for the multiple antenna downlink. The proposed scheme uses the structure of zero-forcing dirty paper coding (DPC) at the transmitter and selects users using a contention-based feedback channel. The user selection procedure is divided into stages and within each stage, a user is selected for one spatial channel (defined...
This paper investigates the issue of resource allocation in heterogenous wireless networks, where users have a choice between multiple service providers. We investigate the feasibility of modeling the allocation problem as a probabilistic voting game. In other words, competing transmitters are modeled as candidates in an election, while the receivers form the electorate. Two specific examples are...
A detailed characterization of interference power statistics in CDMA systems is of considerable practical and theoretical interest. Such a characterization for uplink inter-cell interference has been difficult because of transmit power control, randomness in the number of interfering mobile stations, and randomness in their locations. We develop a new method to model the uplink inter-cell interference...
Voice, in the form of VoIP, has emerged as a dominating traffic category in the Internet. VoIP traffic suffers from severe voice quality degradation if the end-to-end delay and loss becomes high. PCF medium access mechanism offers delay bound delivery which is a crucial attribute for delay sensitive applications like VoIP. But due to its unavailability in most commercial products, little analysis...
In this paper, we investigate the issue of vertical handoffs in heterogeneous wireless networks. A QoS-based vertical handoff scheme for WLAN and WiMAX interworking networks is proposed with aim to provide always best service to users. We also present a simple, yet efficient method to estimate the available bandwidth in WLAN and WiMAX networks to evaluate the real-time status of the overlay networks...
Applications using multicast service discovery protocols, such as iTunes, have become increasingly popular. However, multicast service discovery protocols generate significant network traffic overhead, especially in a wireless network. We measure and analyze the traffic of one of the most widely deployed multicast service discovery protocols, DNS-SD/mDNS, in a campus wireless network where a single...
Multicarrier code division multiple access (MCCDMA) is one of the most promising techniques considered for future broadband mobile services. However, the high peak to average power ratio (PAPR) problem associated with multicarrier systems significantly degrades the power efficiency and makes it less preferred by the industry. In this paper, we exploit the order of the CDMA spreading codes as an extra...
In this paper we quantify 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8 downlink system performance for a macro cell hexagonal grid scenario. The system performance is analyzed for a closed loop Single User Multi-Input Multi Output (SU-MIMO) mode and compared with Single Input Multiple Output (SIMO) and Multi-User (MU) MIMO modes, for a full buffer scenario and static...
Inter-cell interference is a serious problem in multicell OFDMA systems. In this paper, an iterative interference price based power allocation algorithm with inter-cell interference coordination is proposed for downlink multi-cell OFDMA systems. In the algorithm, each base station announces a price for interference and performs power allocation based on the price information received from other base...
The majority of vehicle-to-vehicle (V2V) protocols presented in the literature utilize a combination of controlled access techniques (e.g., TDMA, FDMA, CDMA) to provide prioritized access to the communication medium. While these protocols split the capacity of the communication link to support a maximum number of users with different priority levels, our work utilizes a combination of CDMA and TDMA...
This paper investigates flexible spectrum usages for LTE network that consists of overlaying macrocell and femtocell. In such a networking environment, shared spectrum usage and partitioned spectrum usage are two options to be employed between two radio tiers. After recognizing the pros and cons of these two usages, we propose hybrid spectrum usage to take advantage of their merits. In our proposal,...
This paper introduces the system concept and specifications for an enhanced version of the Wireless IP Access System (WIPAS), the Advanced WIPAS, which is a fixed wireless access (FWA) system that provides higher speed and real-time communication for triple play services: broadband IP service, 4class Quality of Service (QoS) especially VoIP services, and multicast HDTV video transmission services...
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