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This paper presents the analysis of the throughput enhancements using threshold-based PUSC in WiMAX OFDMA system. We consider a point-to-multipoint (PMP) WiMAX network where base station (BS) schedules downlink packets for simultaneous transmissions to multiple users. Using the OFDMA option in the WiMAX standard, users are assigned different subchannels for reception of their data using the same OFDM...
In current wireless standards like 3GPP LTE or IEEE 802.16 / WiMAX multiple access is based on orthogonal signalling using single-carrier frequency-division multiple access (SC-FDMA) or orthogonal frequency-division multiple access (OFDMA). Links between a base station and different terminals use mutually orthogonal radio resources. This paper studies potential gains in average cell throughput by...
We evaluate a dual-hop OFDM relay system with non-regenerative relay without FFT/IFFT processes at the relay node to reduce the processing delay and the complexity of the relay process in terms of the achievable rate and throughput. To maximize the achievable rate, we propose a power allocation scheme to each subcarrier of the source node and the whole subcarrier of the relay node. Due to the flexible...
Fractional frequency reuse (FFR) has been actively studied in order to reduce inter-cell interference, especially for cell edge users in current orthogonal frequency division multiple access systems. However, the best resource block (RB) allocation to the edge users is limited by conventional FFR, which has subbands consisting of contiguous RBs. In this paper, we propose a band-distributed FFR scheme...
The bit loading algorithms are proposed for orthogonal frequency division multiplexing (OFDM) and linear pre- coded OFDM under power spectral density and mean bit error rate (BER) constraints. These algorithms maximize the bit rate of the system while respecting a mean BER. The advantages of both linear procoded OFDM and classical OFDM are analyzed under different scenarios. It is shown that the proposed...
The problem of cross-layer medium access control (MAC) in a SIMO-OFDM system is addressed and a space sensing based random access (SSRA) scheme is proposed. In SSRA scheme, the transmit slot is divided into three parts: space sensing period, channel estimation period and packets transmission period. Without orthogonal training sequences, users can sense the possible spatial collisions in the following...
In OFDMA cellular system, the inter-cell interference is the main interference of the system, which greatly degrades the system performance. In order to enhance cell average throughput and the cell-edge user's peak bit rate, a hybrid inter-cell interference mitigation scheme is proposed. The hybrid scheme combines the fractional frequency reuse scheme and the frequency hopping scheme, in which cell-edge...
While intercell interference coordination (ICIC) for the downlink of multi-cell systems in general and orthogonal frequency division multiple access (OFDMA) networks in particular has been extensively studied, the uplink has received less attention. For the uplink, the impact of ICIC on the overall system throughput ("the ICIC gain") must be analyzed in a system model that captures specific...
In this paper, we investigate the benefits of two-hop opportunistic relay in time division duplex (TDD) OFDMA cellular network configurations. The paper starts with a short analytical model for the two-hop opportunistic relay. The model expresses the probability of finding a suitable relay node in the presence of lognormal fading and it allows the computation of the expected number of out-of-coverage...
We consider a realistic albeit simplified scenario for wireless cellular systems of the next generation (4G and beyond), where MIMO-OFDM, opportunistic scheduling, channel state information at the transmitter and limited base-station cooperation are envisaged. We propose two strategies with limited base-station cooperation that can be easily implemented with today's technology and achieve an approximate...
We propose an efficient proportional fair (PF) scheduling algorithm for multi-user OFDMA systems employing fixed relays. An PF metric maximization problem is first formulated for relay enhanced OFDMA cellular systems. A two-step algorithm is then proposed to solve the problem; the user routing step and the resource allocation step. The simulation results confirm the near-optimal performance of the...
OFDM is an attractive solution for the design of future wireless communications due to its robustness to dispersion in multipath environments. Additional diversity gains can be realised by OFDMA by exploiting not only the temporal fading, but also spectral fading, that can result in higher rates due to increased diversity. A scheduler exploiting multiuser diversity imposes strict feedback requirements...
Resource allocation (RA) for OFDMA has been extensively researched with the objective of maximizing capacity while serving users in a fair manner. However, most of the previous works have focused on achieving these requirements per symbol (instantaneously). On the other hand proportional fair (PF) scheduling which is widely deployed in 3G data networks achieves the system objectives over a certain...
In this paper we report the first real-time measurements of a 3GPP-LTE multiple antenna system in typical indoor and outdoor scenarios. In a single cell, single user scenario we demonstrate throughput exceeding 100 Mbit/s with a 2times2 MIMO configuration. This throughput gain is significant as compared to existing single antenna systems. We describe the basic LTE system design and prototype ingredients...
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