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When fast and accurate channel state information (CSI) at the transmitter is available, opportunistic power control (OPC) is an attractive alternative to signal-to-interference-and-noise ratio (SINR) target following approaches, because it maximizes throughput by taking advantage of fast channel variations. On the other hand, in multiple-input multiple-output (MIMO) systems, open loop schemes such...
In recent years, Orthogonal Frequency Division Multiplexing (OFDM) technology has been widely used in many wireless communication systems, including LTE and WiMAX. Bandwidth is always precious over wireless channel, so it is important to have an effective bandwidth arrangement. On a multi-user system, each user needs to share entire bandwidth with others. In order to enhance the transmission rate,...
Performance of multi-user SC-FDMA (single carrier-frequency division multiple access) system varies according to the user allocation and adaptive bit assignment to the subcarriers because each user experiences different channel characteristics. If any specific user suffers from poor channel characteristics in the conventional method of the distributed and localized user mapping, the total communication...
In this paper we present a new adaptive fractional frequency reuse scheme (AFFR) for multi-cell OFDMA based IEEE 802.16e network. The adaptive fractional frequency reuse (AFFR) scheme is managed by the access service network gateway (ASN-GW) which coordinate a set of BSs (one cluster). To make better usage of radio resources; we assume that the cell area is virtually divided into two different zones:...
An efficient and flexible air interface is the necessary condition for enabling high data rates next generation wireless systems. A practical answer to this need consists in exploiting channel state information at the transmitter for an adaptive and efficient use of the available radio link resources. This paper contributes with a novel strategy for the allocation of the sub-carrier transmit power...
Multiple-input multiple-output (MIMO) systems can achieve high capacity with applying space division multiple access benefits. By using channel state information at BS/MS we can remove inter user interference by applying beam forming. An important challenge at multi user (MU) systems is how design transmitting vector with respect to inter user interference. Capacity problem optimization, maximizing...
In MIMO systems, spatial multiplexing is a powerful technique for increasing channel capacity by transmitting multiple data streams in the same channel simultaneously. Moreover, additional performance can be extracted in the presence of channel state information (CSI) at the transmitter. However, channel estimation error usually exists in practical systems and leads to imperfect CSI. As a result,...
Adaptive modulation of subcarriers for orthogonal frequency division multiplexing (OFDM) has been shown to improve system performance significantly. As a prerequisite, accurate channel state information (CSI) must be available at the transmitter. For time varying, noisy channels, however, this is difficult to achieve in practical systems. In this paper, we consider optimal subcarrier assignment under...
Consider the problem of resource allocation on the downlink of a cellular OFDMA system. A fairness constraint is defined by a minimum data rate, a maximum bit-error rate and a maximum outage probability. This paper proposes a low-complexity resource allocation algorithm that requires a reduced feedback-overhead. Under a partial channel-state information, we derive the optimal subcarrier and power...
In future time division duplex (TDD)-based broadband wireless systems, it will be possible to exploit the channel reciprocity to implement channel state information (CSI)-based multi user multiple input multiple output (MU-MIMO) techniques, which will ensure highly efficient spectrum usage. To increase the cell coverage while ensuring the quality of service (QoS) for all UEs across the cell area,...
In this paper we derive optimal power allocation (PA) in space and time that minimizes BER for transmitter selection in multi-input-single-output (MISO) Rayliegh fading channels assuming perfect channel state information (CSI) is available at receiver and transmitter. This power allocation scheme achieves exponential diversity order with a single RF front end and requires feedback of the best channel...
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