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Inbound handover (HO) or hand-in is accomplished when the user equipment (UE) performs HO from macrocell (MC) to a small cell (SC) [1] [2]. When the UE connects to a SC with a time of stay (ToS) less than a predefined time threshold, this will result in frequent unnecessary HOs and also increase service interruption which in turn will degrade the end user quality of service (QoS). In this paper, we...
Ultra dense network (UDN) is identified as one of the key enablers for 5G since it can provide ultra high spectral reuse factor exploiting proximal transmissions. By densifying the network infrastructure equipments, it's highly possible that each user will have one or more dedicated serving base station antennas, introducing the user-centric virtual cell paradigm. However, due to irregular deployment...
Heterogeneous cellular networks (HetNets) is key technology in 5G used to tackle the ever increasing demand of data rate. The most critical problem of HetNet is interference. In this paper, we utilize the coordinated beamforming technique to mitigate the interference problem. We also suggest that reference signal receive power (RSRP) based cell association scheme has limitation when applied to multi-tier...
We formulate the resource allocation in the downlink of heterogeneous orthogonal frequency division multiple access (OFDMA) networks. Our primary objective is to maximize the system sum throughput subject to service and system constraints, including maximum transmit power, quality of service and per-user subchannel allocation. Due to the intercell interference, the corresponding optimization problem...
This paper analyzes a spectrum reuse scheme based on region division for secondary users in cognitive radio networks with outage constraint of the primary user. The secondary users can reuse the spectrum by sharing the primary user's uplink (UL) frequency resources in the system. With the help of the stochastic geometry, the secondary user reusing the frequency spectrum can be modeled as the probability...
In this paper, we consider a worst-case based robust beam forming approach for two-way relay networks that consist of two transceivers and multiple relays. Both the transceiver-to relay channels are assumed to have norm-bounded channel estimation errors. The worst case of the problem in a norm defined error set is optimized to guarantee the performance of the actual case. The resultant beam forming...
In this paper, we propose a spectrum splitting-based cognitive interference management method for LTE downlink two-tier networks (that provide closed-access mode). In the proposed method, the resource-blocks in the macrocell (in frequency and time domain) are allocated to the users with the received signal-to-interference-plus-noise-ratio greater than a threshold. The rest of resource-blocks are then...
This paper explores the symbol synchronization in the presence of co-channel interference (CCI) of Orthogonal Frequency Division Multiplexing (OFDM) based heterogeneous network (HetNet). The CCI is generated by a HetNet model with macrocell and small cells. Schmidl and Cox (S&C) Algorithm is applied for symbol synchronization. We find that the presence of CCI severely degrades the performance...
The impact of downlink co-channel interference (CCI) is increasingly highlighted in heterogeneous networks (Het-Nets) where the macrocell base stations (MBSs) and low-power nodes share the same spectrum resource. In this paper, we focus on mitigation of downlink CCI from MBS to picocells, which are severely affected, through the application of coordinated beam forming (CBF) technique. The closed-form...
Cognitive radio is considered as a promising technology that enables dynamic spectrum access and improves spectrum utilization. To bootstrap the communication, rendezvous process is crucial for cognitive radio users to establish communication links among each other. Blind rendezvous is a representative technology for rendezvous purpose without relying on a common control channel. Existing works mainly...
According to the characteristic that the surface electromyogram signal (sEMG) is very weak and influenced by noise vulnerability, this paper proposes a new method that uses the unsupervised Kohonen neural network weights optimized to determine the order of the reconstruction matrix during the process of the noise reduction in singular value decomposition (SVD) effectively. First, let the sEMG collected...
We demonstrate self-referenced wavefunction retrieval of a valence electron wavepacket during its creation by strong-field ionization with a sub-10-attosecond precision, based on a distinct separation of interferences arising at different time-scales.
Recent works have shown that the white-space spectrum opened to cognitive radio devices is far less than what the lobbyists claimed. With fast growing number of secondary users, carefully scheduling the spectrum allocation in cognitive radio networks operating on white space becomes vital. However, the frequent ON/OFF activity of primary users (PU) and the mobility of the cognitive users make the...
The promising spectrum sharing technology used to improve the spectrum usage may cause severe narrowband interference, which seriously degrades the timing synchronization. As noticed that only the auto-correlation based methods have been investigated in the literature, this paper examines the impairment of narrowband interference to the cross-correlation based timing synchronization, to obtain a comprehensive...
Spectrum sharing is promising to improve the efficiency of spectrum usage. However, this technology may incur severe narrow band interference (NBI), which seriously complicates the synchronization problem. This paper investigates the timing synchronization problem in the presence of NBI for the OFDM-based spectrum sharing systems. We consider the cross-correlation based timing synchronization and...
Currently there is a growing demand towards interactive multi-media services using high capacity Hybrid Fiber Coaxial (HFC) networks. With regards to the realization of upstream traffic, many problems occur with the accumulation of noise due to the tree and branch architecture of the coaxial access network. We have figured out the typical network topology for the two-way HFC network, and pointed out...
For the uplink transmission of an orthogonal frequency division multiple access (OFDMA) system, frequency synchronization is particularly challenging due to the presence of multiple Carrier Frequency Offsets (CFOs), which destroy the orthogonality among subcarriers and introduce massive multiuser interference (MUI) and inter-carrier interference (ICI). To prevent the consequent performance degradation,...
Multimedia Broadcast/Multicast Service (MBMS) based on point-to-multipoint (p-t-m) radio transmission was introduced by 3GPP to deliver broadcast service to a group of user equipments (UEs) in a cellular system. As a broadcast system with uplink feedback, its performance is limited by UEs in poor connections. To utilize the limited radio resource more efficiently, a simple but effective mechanism...
In spite of the significant performance gain that multiple-input multiple-output (MIMO) transmission can provide in wireless communication, the use of MIMO in realistic systems will lead to large control signaling overhead. Performance comparison of different transmission schemes should consider the control channel (CC) constraints. In this paper, we first build the model of CC for downlink MIMO transmission,...
Cognitive radios allow unlicensed wireless users to access channels that are in the licensed spectrum bands. However, in a wireless network with cognitive radios, when a licensed user becomes active on a channel in a certain area, nodes and links that were using that channel must release it, which will cause traffic failures. Simple and effective recovery schemes are needed to re-allocate available...
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