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We consider the problem of distributed estimation in a power constrained collaborative wireless sensor network (WSN), where the network is divided into a set of sensor clusters, with collaboration allowed among sensors within the same cluster but not across clusters. Specifically, each cluster forms one or multiple local messages via sensor collaboration (in particular, linear operation is considered)...
This paper considers the effect of channel estimation error in the multiuser downlink MIMO relay channels. We introduce a modified upper bound and a modified power allocation strategy for the previous asymptotic optimal singular value decomposition zero-forcing beamforming (SVD-ZFBF) [2] at first. And then the effect of channel estimation error to SVDZFBF would be discussed. Similar with the full...
In this paper, for the first time, an Ant Colony Optimization (ACO) based algorithm is used to solve the bit and subcarrier resource allocation problem of single-cell OFDMA systems. It results in a directed multigraph if the vertexes are used to represent the subcarrier and each path corresponds to a possible chosen modulation index of a specific user. Earlier studies which applied evolutionary algorithms...
In the next generation wireless systems, it's quite likely that a large number of user terminals are not able to transmit and/or receive over the entire system bandwidth, as much wider system bandwidth, e.g., 100 MHz, is expected to be employed in the future. As a new and challenging problem, user terminal bandwidth limitation is considered in this paper, and multiuser resource allocation for orthogonal...
In this paper, we study resource allocation in a downlink OFDMA system assuming imperfect channel state information (CSI) at the transmitter. To achieve the individual QoS of the users in OFDMA system, adaptive resource allocation is very important, and has therefore been an active area of research. However, in most of the the previous work perfect CSI at the transmitter is assumed which is rarely...
In this paper, we study the resource allocation problem in relay aided two-hop uplink multi-user transmission with a single relay node and a single destination node. The orthogonal frequency division multiple access (OFDMA) is adopted as the main transmission modulation. We investigate the problems of subcarrier allocation, subcarrier coupling, and power allocation. The optimization is formulated...
We propose a packet scheduling policy called maximum sum backlog (MSB) scheduling in wireless relay networks. It assigns a high priority to a user queues whose packets experienced longer delay until arriving the current queues by choosing a queue whose sum backlog multiplied by the corresponding link capacity is highest. We derive the stability region of the wireless relay system and prove that the...
Femtocell is attracting an increasing interest in the telecommunication sectors. In this paper, we study the efficient resource allocation in femtocell networks with completed closed access method. The interaction between a macrocell and its underlying femtocells is identified, characterized, and qualified. The study answers the fundamental question in the femtocell networks: how to allocate spectrum...
The power allocation problem is addressed for time division duplex (TDD) LTE-A uplink systems in this paper. Due to the IDFT de-spreading in LTE-A uplink, the channel frequency responses in an IDFT de-spreading block will be tangled together. After analyzing the equivalent signal to interference plus noise ratio (SINR) in the time domain, a Truncated Squared norm of channel equalization Coefficients...
In cognitive radio networks (CRN), underlay spectrum sharing allows secondary users (SUs) to utilize the spectrum on which the primary users (PUs) in primary radio networks (PRN) are working at the same time, without introducing intolerant interferences. In this paper, we study the joint transmission power and time allocation in CRN with underlay spectrum sharing technology. To maximize the total...
In this paper, we propose a realistic resource sharing protocol for VANET. The main idea of our protocol comes from typhoons. Typhoons move according to their eyes' mobility, i.e., quorums which are responsible for a given resource holder/requester "moves" according to the resource holder's/ requester's mobility. Our protocol exploits spatial locality between requesters and resource holders...
Interleave-division multiple-access (IDMA) has recently been proposed as a multiuser scheme that uses low complexity turbo-like iterative receivers and can outperform coded CDMA. Power allocation has been shown as an effective means for improving the performance of iterative receivers, and can be readily applied to multiuser systems including IDMA and CDMA. Power allocation allows the decoder to operate...
Cooperative communication is an emerging and effective technology which can overcome the limitation and improve overall system performance of wireless networks. As important design parameters, relay selection, power and bandwidth allocation have been investigated respectively in previous literature. However, most of the existing schemes mainly consider single-relay selection, which may result in imbalance...
In this paper, we will study the joint problem of power allocation, relay selection and subchannel pairing in OFDM based amplify-and-forward multiple relays system. The optimization problem of maximizing system capacity under joint power constraint at source and relays is firstly formulated. Then, based on Lagrangian dual method, an optimal algorithm to the problem is derived with high SNR assumption...
In this paper, cross-layer scheduling for orthogonal frequency division multiple access (OFDMA) two-way half-duplex amplify-and-forward (AF) relay assisted networks is studied. Assuming slow fading channels, cross-layer scheduling design with imperfect channel state information at the transmitter (CSIT) and heterogeneous data rate requirements for the users is modeled as an optimization problem, where...
Efficient routing protocols for equal power and optimal power allocation in a multi-hop decode-and-forward network in fading are proposed. The end-to-end outage probability from source to destination is used as the optimization criterion. The problem of finding the optimal route is investigated when either the mean channel state information (CSI) or the instantaneous CSI for all the links of the network...
A modified two-group resource allocation scheme is tested with three channel ordering schemes, a hard decision parallel interference cancellation (HDPIC) scheme and a successive interference cancellation (SIC) scheme to improve the data rate. Channel ordering ensures channels with the lowest energy requirement are loaded with the higher data rate in the two-group resource allocation scheme but may...
In this paper, we propose a multiuser spectrum allocation scheme for high-rate UWB systems under QoS requirements. This scheme comes as a solution to the coexistence of multiple users sharing the three sub-bands of the same channel as defined in the WiMedia solution adopted for multiband UWB systems. Indeed, WiMedia solution does not allow more than three users to coexist in the same channel. Based...
Recent advances in the physical layer have enabled the simultaneous reception of multiple packets by a node in wireless networks. In this paper, we present a generalized model for the throughput optimization problem in multi-hop wireless networks that support multi-packet reception (MPR) capability. The model incorporates the multi-access channel, which accurately accounts for the achievable capacity...
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