94 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
Performance evaluation of multicell coordinated beamforming approaches for OFDM systems
In this paper we propose and evaluate multicell coordinated beamforming schemes for the downlink of MISO-OFDM systems. The precoders are designed in two phases: first the precoder vectors are computed in a distributed manner at each BS considering two criteria, namely distributed zero-forcing and virtual signal-to-interference noise ratio. Then the system is optimized through distributed power allocation under per-BS power constraint. The proposed power allocation scheme is designed based on minimization of the average bit error rate over all the available subcarriers. Both the precoder vectors and the power allocation are computed by assuming that the BSs have only knowledge of local channel state information and do not share the data symbols. The performance of the proposed schemes are evaluated, considering typical pedestrian scenarios based on LTE specifications. The results have shown that the proposed distributed power allocation scheme outperform the equal power allocation approach
Robust leakage-based distributed precoder for cooperative multicell systems
Coordinated multipoint (CoMP) from long term evolution (LTE)-advanced is a promising technique to enhance the system spectral efficiency. Among the CoMP techniques, joint transmission has high communication requirements, because of the data sharing phase through the backhaul network, and coordinated scheduling and beamforming reduces the backhaul requirements, since no data sharing is necessary. Most of the available CoMP techniques consider perfect channel knowledge at the transmitters. Nevertheless for practical systems this is unrealistic. Therefore in this study the authors address this limitation by proposing a robust precoder for a multicell-based systems, where each base station (BS) has only access to an imperfect local channel estimate. They consider both the case with and without data sharing. The proposed precoder is designed in a distributed manner at each BS by maximising the signal-to-leakage-and-noise ratio of all jointly processed users. By considering the channel estimation error in the design of the precoder, they are able to reduce considerably the impact of these errors in the system's performance. The results show that the proposed scheme has improved performance especially for the high signal-to-noise ratio regime, where the impact of the channel estimation error may be more pronounced
Partial joint processing for frequency selective channels
In this paper, we consider a static cluster of base stations where joint processing is allowed in the downlink. The partial joint processing scheme is a user-centric approach where subclusters or active sets of base stations are dynamically defined for each user in the cluster. In frequency selective channels, the definition of the subclusters or active set thresholding of base stations can be frequency adaptive (per resource block) or non-adaptive (averaged over all the resource blocks). Frequency adaptive thresholding improves the average sum-rate of the cluster, but at the cost of an increased user data interbase information exchange with respect to the non-adaptive frequency thresholding case. On the other hand, the channel state information available at the transmitter side to design the beamforming matrix is very limited and rank deficiency problems arise for low values of active set thresholding and users located close to the base station. To solve this problem, an algorithm is proposed that defines a cooperation area over the cluster where the partial joint processing scheme can be performed, frequency adaptive or non-adaptive, for a given active set threshold value
Analyzing Interference from Static Cellular Cooperation using the Nearest Neighbour Model
The problem of base station cooperation has recently been set within the
framework of Stochastic Geometry. Existing works consider that a user
dynamically chooses the set of stations that cooperate for his/her service.
However, this assumption often does not hold. Cooperation groups could be
predefined and static, with nodes connected by fixed infrastructure. To analyse
such a potential network, in this work we propose a grouping method based on
proximity. It is a variation of the so called Nearest Neighbour Model. We
restrict ourselves to the simplest case where only singles and pairs of base
stations are allowed to be formed. For this, two new point processes are
defined from the dependent thinning of a Poisson Point Process, one for the
singles and one for the pairs. Structural characteristics for the two are
provided, including their density, Voronoi surface, nearest neighbour, empty
space and J-function. We further make use of these results to analyse their
interference fields and give explicit formulas to their expected value and
their Laplace transform. The results constitute a novel toolbox towards the
performance evaluation of networks with static cooperation.Comment: 10 pages, 6 figures, 12 total subfigures, WIOPT-SPASWIN 201
On precoding for overlapped clustering in a measured urban macrocellular environment
In this paper, we study the performance of precoding schemes for cooperative transmission of multiple coherent base stations (BSs) that allow for overlapped clustering in a measured urban macrocellular environment at 2.66 GHz, in order to verify previous findings obtained by using simulated channel data. The evaluated precoding schemes include zero-forcing (ZF), layered virtual signal-to-interference-plus-noise ratio (SINR) maximization (LVSM) and clustered virtual SINR maximization (CVSM). The results show that the sum rate of the CVSM scheme outperforms the other precoding schemes. In addition, the ZF achieves higher rates than the LVSM, except when the channel condition is poor. When greedy proportional user scheduling is considered, the CVSM scheme and the ZF scheme offer similar performance, whereas the LVSM scheme gives little gain over a non-cooperative transmission scheme used as the baseline
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