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This paper studies energy-efficient transmission strategies for a closed-loop downlink multiple-input–single-output (MISO) system, where a communication period consists of three phases for uplink training, downlink data sending, and base station (BS) idling. For both delay-tolerant and delay-sensitive services, the durations of the three phases are optimized, aimed at maximizing the energy efficiency...
In this paper, the traditional power minimization problem under some QoS constraints in a SISO cellular network is considered. However, the research is distinguished by two points. (1) The association relationship between base stations (BS) and users is no longer known and fixed. (2) When the QoS constraints are not satisfied, instead of simply claiming the problem is infeasible, the network tries...
Multicast transmission is known as an efficient mechanism for offering the same services for different terminals. However, the power consumption is surprisingly arisen due to terminals with the worst channel quality while maintaining the Quality of Service (QoS) and data decoding requirements. In order to address this problem, we examine the energy saving performance of an efficient algorithm called...
In this paper, the energy efficiency (EE) of a 2-tier cellular network subject to downlink transmission outage probability constraints is analyzed under a shared spectrum scenario. The heterogeneous network considered consists of randomly distributed microcell BSs overlaid with picocell BSs. Based on the analysis of the structure of the EE function, the sufficient condition that enables the EE of...
Cognitive radio (CR) and Multiple Input Multiple Output (MIMO) technologies represent emerging and promising technologies for providing high spectrum utilization, and maximizing the capacity to face the huge demand for wireless applications. In this context, a transmission scheme that exploits both CR and MIMO is presented, together with its optimization to increase the system goodput as well as to...
In heterogeneous wireless environments which change dynamically, the optimal network selection problem is one of the key issues. This paper proposes a network selection scheme based on the required bandwidth, which estimates the bandwidth required to satisfy the quality of service (QoS) requirements of the target service. Required bandwidth can be estimated from the signal strength of each access...
Cross-layer resource allocation represents an emerging technology to enable efficient resource management and quality of service (QoS) support for wireless networks. In particular, the rapidly rising energy prices and the increasing power consumption levels in current wireless network constitute a major concern for network operators. In this context, we introduce here a cross-layer approach that allows...
Multiple Input Multiple Output (MIMO) adds a new dimension to be exploited in Cognitive Radio (CR) by simultaneously serving several users. The spatial domain that is added through MIMO is another system resource that has to be optimized, and shared when possible. In the current paper, we present a spatial sharing that is carried out through Zero Forcing beamforming (ZFB). The power consumption in...
This paper investigates the power allocation algorithms based on convex theory for multiuser multi-relay amplify-and-forward (AAF) wireless cooperative network. In this system, there are multiple single-antenna users to communicate with one destination with the help of multiple relay nodes at the same time. In order to guarantee the quality-of-service (QoS) for all the users and reduce the power consumption,...
In this paper, we consider a joint power control and resource allocation scheme for co-channel deployed femtocells in macrocell networks. The strong interference in the downlink from the femtocells should be well controlled to satisfy the quality of service (QoS) requirement of both macrocell users and femtocell users. We provide both centralized and distributed schemes to solve the formulated optimization...
We study the power allocation algorithms in the case of multi-source multi-relay (MSMR) amplify-and-forward wireless cooperative network in this paper. In this MRMS system, we consider that multiple users would communicate with one destination node with the help of multiple relay nodes in the same time. To guarantee the quality-of-service (QoS) for all the users and reduce the power consumption, we...
We investigate fundamental characteristics of cooperative transmission in terms of power efficiency. By introducing the concept of “cooperative region”, we evaluate the average power efficiency which is defined as the ratio of total consumed transmit power with cooperation to that of direct transmission and show how the average performance depends upon the QoS requirement, distance between source...
Cognitive users (CUs) are allowed to access licensed bands without causing harmful interference to primary users (PUs). However, the quality of service (QoS) of CUs can not be guaranteed when CUs experience bad channel conditions in direct transmission between the cognitive source and its destination. In this paper, we consider the problem of cooperative transmission in cognitive radio networks. The...
In this paper, we consider a heterogeneous network, where objects of different kinds can ensure some amplify and forward function. In this case, objects can have different characteristics. We propose a thorough study of the energy consumption, taking into account efficiencies of the transmitter and relays. Given a quality of service, we minimize the global consumption and evaluate the impact of the...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
This paper investigates effects of pilot assisted channel estimation on dynamic resource allocation in a multiuser orthogonal frequency division multiplexing (OFDM) system. The channel estimation is done in each OFDM symbol through least-squared error (LSE) or minimum mean-squared error (MMSE) algorithm. The performance of each of these algorithms is evaluated through computer simulations. The maximal...
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