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In this work, we consider channel quality indicator (CQI) prediction for High Speed Downlink Packet Access (HSDPA). In HSDPA systems, there is a delay of about 3 subframe associated with the application of CQI feedback. Traditional FIR filter based predictors such as Least-Mean-Squares (LMS) and Recursive-Least-Squares (RLS) typically come with high computational complexity. We consider a first order...
Wireless source localization has found a number of applications in wireless sensor networks. In this work, we investigate robust and low complexity solutions to the problem of source localization based on the time-difference of arrivals (TDOA) measurement model. By adopting a min-max approximation to the maximum likelihood source location estimation, we develop two low complexity algorithms that can...
This paper deals with the partial target coverage (PTC) problem in wireless sensor networks with the objective of optimizing network lifetime. We first build a linear programming formulation, which takes total time a sensor spends on covering some targets into consideration, in order to obtain a lifetime upper bound. Then, based on the information of this formulation, we develop a sensor assignment...
An important transmitter adaptation technique used in multiple-input multiple-output (MIMO) communication systems is precoding based on the dominant right-singular vectors of the channel matrix. These vectors are typically estimated at the receiver, quantized, and fed-back to the transmitter via a low-rate feedback channel. We present a method for designing an efficient low-rate quantizer for the...
In this paper an improved iterative algorithm is proposed for distributed transmit beamforming to achieve carrier phase alignment at the receiver. The transmitters adjust their phase offsets based on one-bit feedback from the receiver in each time slot. The proposed algorithm has an improvement in the convergence speed of phase alignment compared to a previously proposed algorithm in the literature...
Based on considering the CODEC frame duration, this paper proposes a superior uplink scheduling algorithm that can efficiently support multiple DTX VoIP CODECs over M-WiMAX, and be able to facilitate the uplink resource wastes during silence period and optimize the system VoIP capacity. The BS uplink resource allocation procedure is planned and adapted according to the reserved bit in the Bandwidth...
This paper considers a joint subcarrier and power allocation in an orthogonal frequency division multiple access (OFDMA) cellular system with base station (BS) cooperation. The problem is formulated as an average utility maximization subject to the per-antenna power constraint. Existing algorithms to solve similar problem in a single-sell system are shown not so efficient in the cooperative multi-cell...
In recent years, wireless mesh networks (WMNs) have been widely deployed to provide wireless access to the Internet. However, due to inter-link interference, the aggregated capacity of WMNs is limited, even with multiple channels. As a result, many links in WMNs are suppressed since interfering links cannot be active (i.e., transmitting packets) simultaneously. In this paper, we propose a joint design...
Interactive wireless applications, like VoIP over wireless networks, desire high-quality links and smooth connectivity during user movement. In order to support seamless roaming in wireless networks, handoff optimization has attracted a lot of attention recently. Most existing approaches aim at reducing handoff latency in communication protocols. While these methods provide significant savings in...
Wireless infrastructures have seen a drastic increase in energy requirements as technology shifted towards higher frequencies in an attempt to increase bandwidth. This is further accentuated by increasingly demanding real-time services such as video streaming. To cater for these new services and still guarantee an adequate quality of service, wireless network operators in large cities have to install...
In this paper, we consider a two hop cognitive radio network where there are multiple primary and secondary users. We propose the design of antenna weights at the source and relay based on zero forcing principles. These antenna weights are designed to cancel the interference among the secondary users while maintaining fairness, and to ensure interference free signals at each primary user. To analyze...
The problem of resource allocation in multiuser OFDM system is a combinatorial optimization problem, difficult to solve in polynomial time. For the sake of reducing complexity, it can be solved either by relaxing constraints and making use of linear algorithms or by metaheuristic methods. In this paper, ant colony optimization, a typical algorithm of metaheuristic methods, is applied to solve the...
In ad hoc networks, reducing energy consumption and improving throughput are both important for high network performance. This paper presents a joint power and rate control adaptive algorithm to optimize the trade-off between power consumption and throughput in ad hoc networks. Each node chooses its own transmission power and rate based on limited environment information in order to achieve optimal...
In TCP, a spurious packet retransmission can be caused by either spurious timeout (STO) or spurious fast retransmit (SFR). The "lost" packets are unnecessarily retransmitted and the evoked congestion control process causes network underutilization. In this paper, we focus on spurious retransmission detection. We first present a survey on some important and interesting spurious retransmission...
Clustering algorithms have been extensively applied for energy conservation in wireless sensor networks (WSNs). In a clustered WSNs, cluster-heads (CHs) play an important role and drain energy more rapidly than other member nodes. Numerous mechanisms to optimize CH selection and cluster formation during the set-up phase have been proposed for extending the stable operation period of the network until...
Wireless Mesh Networks (WMNs) have emerged to provide cost-effective broadband Internet accesses. Today's IEEE 802.11 PHY and MAC specifications support multi-channel and multi-rate capabilities. Designing an efficient channel assignment protocol utilizing available channels and data rates is a hot issue to leverage the network capacity. In multi-rate networks, low-rate links severely decrease the...
This paper introduces a modified complex to real amplitude least-squares (CRALS) algorithm for the estimation of dense multipath in an UWB-IR channel. The traditional CRALS is ineffective for UWB-IR signal due to its wide bandwidth and large off period. This algorithm is modified to resolve three closely spaced paths in a correlation window. One novelty of the modified algorithm is that region-based...
This paper aims to investigate an efficient power allocation algorithm for multiuser orthogonal frequency division multiplexing (MU-OFDM) cognitive radio (CR) systems that uses the peak power constraint to protect the primary users. Under this constraint, the high-complexity optimal power allocation algorithm for OFDM-based CR systems is not suited to determine the power distribution because the algorithm...
This paper considers the design of secondary wireless mesh networks which use leased frequency channels. In a given geographic region, the available channels are individually priced and leased exclusively through a primary spectrum owner. The usage of each channel is also subject to published interference constraints so that the primary user is not adversely affected. When the network is designed...
Proportional fairness (PF) scheduling achieves a balanced tradeoff between throughput and fairness and has attracted great attention recently. However, most previous works on PF only consider the single cell scenario. This paper focuses on the problem of achieving global PF in a generalized multiple base station multiple user network. The problem is formulated as a maximization model and solved using...
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