174 research outputs found
Network MIMO with Partial Cooperation between Radar and Cellular Systems
To meet the growing spectrum demands, future cellular systems are expected to
share the spectrum of other services such as radar. In this paper, we consider
a network multiple-input multiple-output (MIMO) with partial cooperation model
where radar stations cooperate with cellular base stations (BS)s to deliver
messages to intended mobile users. So the radar stations act as BSs in the
cellular system. However, due to the high power transmitted by radar stations
for detection of far targets, the cellular receivers could burnout when
receiving these high radar powers. Therefore, we propose a new projection
method called small singular values space projection (SSVSP) to mitigate these
harmful high power and enable radar stations to collaborate with cellular base
stations. In addition, we formulate the problem into a MIMO interference
channel with general constraints (MIMO-IFC-GC). Finally, we provide a solution
to minimize the weighted sum mean square error minimization problem (WSMMSE)
with enforcing power constraints on both radar and cellular stations.Comment: (c) 2015 IEEE. Personal use of this material is permitted. Permission
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this work in other work
Overlapped-MIMO Radar Waveform Design for Coexistence With Communication Systems
This paper explores an overlapped-multiple-input multiple-output (MIMO)
antenna architecture and a spectrum sharing algorithm via null space projection
(NSP) for radar-communications coexistence. In the overlapped-MIMO
architecture, the transmit array of a collocated MIMO radar is partitioned into
a number of subarrays that are allowed to overlap. Each of the antenna elements
in these subarrays have signals orthogonal to each other and to the elements of
the other subarrays. The proposed architecture not only improves sidelobe
suppression to reduce interference to communications system, but also enjoys
the advantages of MIMO radar without sacrificing the main desirable
characteristics. The radar-centric spectrum sharing algorithm then projects the
radar signal onto the null space of the communications system's interference
channel, which helps to avoid interference from the radar. Numerical results
are presented which show the performance of the proposed waveform design
algorithm in terms of overall beampattern and sidelobe levels of the radar
waveform and finally shows a comparison of the proposed system with existing
collocated MIMO radar architectures.Comment: accepted at IEEE WCN
An Optimal Application-Aware Resource Block Scheduling in LTE
In this paper, we introduce an approach for application-aware resource block
scheduling of elastic and inelastic adaptive real-time traffic in fourth
generation Long Term Evolution (LTE) systems. The users are assigned to
resource blocks. A transmission may use multiple resource blocks scheduled over
frequency and time. In our model, we use logarithmic and sigmoidal-like utility
functions to represent the users applications running on different user
equipments (UE)s. We present an optimal problem with utility proportional
fairness policy, where the fairness among users is in utility percentage (i.e
user satisfaction with the service) of the corresponding applications. Our
objective is to allocate the resources to the users with priority given to the
adaptive real-time application users. In addition, a minimum resource
allocation for users with elastic and inelastic traffic should be guaranteed.
Every user subscribing for the mobile service should have a minimum
quality-of-service (QoS) with a priority criterion. We prove that our
scheduling policy exists and achieves the maximum. Therefore the optimal
solution is tractable. We present a centralized scheduling algorithm to
allocate evolved NodeB (eNodeB) resources optimally with a priority criterion.
Finally, we present simulation results for the performance of our scheduling
algorithm and compare our results with conventional proportional fairness
approaches. The results show that the user satisfaction is higher with our
proposed method.Comment: 5 page
Fundamental Limits of Caching with Secure Delivery
Caching is emerging as a vital tool for alleviating the severe capacity
crunch in modern content-centric wireless networks. The main idea behind
caching is to store parts of popular content in end-users' memory and leverage
the locally stored content to reduce peak data rates. By jointly designing
content placement and delivery mechanisms, recent works have shown order-wise
reduction in transmission rates in contrast to traditional methods. In this
work, we consider the secure caching problem with the additional goal of
minimizing information leakage to an external wiretapper. The fundamental cache
memory vs. transmission rate trade-off for the secure caching problem is
characterized. Rather surprisingly, these results show that security can be
introduced at a negligible cost, particularly for large number of files and
users. It is also shown that the rate achieved by the proposed caching scheme
with secure delivery is within a constant multiplicative factor from the
information-theoretic optimal rate for almost all parameter values of practical
interest
Coexistence Analysis between Radar and Cellular System in LoS Channel
Sharing spectrum with incumbents such as radar systems is an attractive
solution for cellular operators in order to meet the ever growing bandwidth
requirements and ease the spectrum crunch problem. In order to realize
efficient spectrum sharing, interference mitigation techniques are required. In
this letter we address techniques to mitigate MIMO radar interference at MIMO
cellular base stations (BSs). We specifically look at the amount of power
received at BSs when radar uses null space projection (NSP)-based interference
mitigation method. NSP reduces the amount of projected power at targets that
are in-close vicinity to BSs. We study this issue and show that this can be
avoided if radar employs a larger transmit array. In addition, we compute the
coherence time of channel between radar and BSs and show that the coherence
time of channel is much larger than the pulse repetition interval of radars.
Therefore, NSP-based interference mitigation techniques which depends on
accurate channel state information (CSI) can be effective as the problem of CSI
being outdated does not occur for most practical scenarios.Comment: Corrected some typos and reference
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