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In this paper we consider retransmission strategies for centralized cyclic polling-based systems over wireless channels subject to external interference. The considered strategies differ in the time when retransmissions for one particular node are carried out, and in the number of retransmissions that can be carried out for one node. We show experimentally and by simulation that two related strategies...
There is a great surge of interest recently in the fixed-mobile convergence from the telecom industry. This is supported by strong 3G operator interest in using the broadband penetration as a spring board to achieve cost effective delivery of the multimedia data for indoor coverage. Statistics indicated that more than 70% of the calls are made from end-users in indoor environments. Based on this trend,...
By using frequency-domain oversampling, we propose a frequency-domain fractionally-spaced linear minimum mean-square error (FDFS-LMMSE) receiver for orthogonal frequency-division multiplexing (OFDM) systems. The proposed FDFS-LMMSE receiver is shown to significantly outperform the conventional LMMSE receiver (without oversampling) in multipath fading channels. This is because the FDFS-LMMSE receiver...
Ad hoc networks are one operational mode of IEEE802.11 wireless local area networks (WLANs) in which users form themselves the network and act as routers to one another. When the density of such a network is high, capacity becomes limited by the interference resulting from the collisions between simultaneously transmitted packets. Interference gets even worse in the case of reliable transport based...
Over the last few years there has been an emerging interest in ultrawideband (UWB) communications in wireless sensor networks, mainly due to their low-complexity and low-power consumption. In particular, auto-correlation receiver (AcR) is a potential candidate for such applications. However, the presence of network interference, especially interference between uncoordinated UWB networks, will severely...
This paper presents driver and bicyclist crossing behavior, including the crossing speeds, crossing gap/lag acceptance behavior parameters at intersection. Traffic behaviors data recordings from a signalized intersection were measured with the video collected with right-turn vehicle speeds, gap/lag distribution and bicyclist group-riding crossing behavior whether under traffic guide or not. The results...
To settle the contradiction between scarce radio spectrum resource and the exigent requirement, effective methods of dynamic spectrum allocation are proposed in cognitive radio system. In this paper, game theory model and graph-coloring model are analyzed, which can improve spectrum efficiency and solve the deficiency of spectrum resource.
To improve the detection performance and increase detection efficiency of user recognition and frequency spectrum utilization ratio, the conventional detection method was improved by using detection period that can be adjusted with actual requirement instead of the fixed detection period. In our simulation, the new method increases spectrum access chance of user recognition, reduces lost time of detection...
We study the transmission capacity of wireless ad hoc networks in this paper. Transmission capacity can not be got the close-form for general cases except for some special cases. In this paper we provide a new solution to this problem. By using Taylor series, the asymptotic expression for transmission capacity is derived. Comparing the asymptotic with the exact expressions shows that, the asymptotic...
Non-coherent receivers have become promising candidates for low-complexity and low-power Ultra Wide Band (UWB) systems. However, a Non-Coherent Combining Loss (NCCL) is evident in the traditional non-coherent receivers that mainly rely on analog implementations, especially when multiple access techniques are employed. This paper proposes a new Digital Code Matched Filter (DCMF)-based non-coherent...
The goal of this paper is to present novel metrics for system usability assessment and quality assessment (SQA). Proposed metrics should provide means of capturing overall system interference with regular daily routines and habits of system users, referred to as "attentive interference". We argue that assuring the system is attentive proves essential when trying to mitigate risks related...
A chop for a source statement s and a target statement t reveals the program parts involved in conveying effects from s to t. While precise chopping algorithms for sequential programs are known, no chopping algorithm for concurrent programs has been reported at all. This work introduces five chopping algorithms for concurrent programs, which offer different degrees of precision, ranging from imprecise...
A typical electronic systems with long signal transmission line illuminated by an ultra-wide band (UWB) pulse generator has been presented The test shows that: interference will be induced into the ground equipment, and working signals will be distorted under such condition. An `antenna model' of the transmission line is presented The main reason of the interference induced into the system is that...
Coordinated multi-point transmission/reception (CoMP) is one of the candidate techniques for LTE-advanced systems to increase the cell average and cell edge user throughput in both uplink and downlink. This paper presents uplink CoMP-MU-MIMO scheme and the corresponding system level performance evaluation which shows that the uplink CoMP-MU-MIMO joint processing can bring significant gains to both...
Shared cache allocation policies play an important role in determining CMP performance. The simplest policy, LRU, allocates cache implicitly as a consequence of its replacement decisions. But under high cache interference, LRU performs poorly because some memory-intensive threads, or aggressor threads, allocate cache that could be more gainfully used by other (less memory-intensive) threads. Techniques...
Performance degradation of memory-intensive programs caused by the LRU policy's inability to handle weak-locality data accesses in the last level cache is increasingly serious for two reasons. First, the last-level cache remains in the CPU's critical path, where only simple management mechanisms, such as LRU, can be used, precluding some sophisticated hardware mechanisms to address the problem. Second,...
In this paper, we study the reverse link (RL) capacity of a co-channel macrocell-femtocell network, where the macrocell and femtocell networks share the same carrier. The analysis is done based on an outage probability criterion, and we use this analysis further to compare the capacities of different practical multi-carrier macrocell-femtocell deployment strategies.
Passive RFID tags share a common channel and they use back-scattering modulation because of no self battery. It causes reader collision problems when signal from a reader interferes with signal from other readers. The evolving standards use CSMA based protocol called 'Listen Before Talk (LBT)' and FDMA based protocol called 'Frequency Hopping Spread Spectrum (FHSS)' to reduce reader collision problems...
In 3GPP long term evolution (LTE) uplink, single transmit antenna is adopted due to its simplicity and acceptable performance. However, in order to satisfy the higher requirement of LTE-Advanced (LTE-A) on uplink spectrum efficiency, multiple transmit antennas must be supported in LTE-A uplink. At the same time, the backwards compatibility to LTE should be taken into considerations. Therefore, the...
Spectrum splitting is the simplest approach to allocate the spectrum to femtocells overlaid with the existing cellular networks. In orthogonal frequency division multiple access (OFDMA) systems, this can be done by assigning a subset of orthogonal subcarriers to femtocells. To ensure subcarrier orthogonality and thus not interfere with existing macro Mobile Stations (MSs), the signals from the strongest...
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