5,712 research outputs found
Coverage Analysis of Relay Assisted Millimeter Wave Cellular Networks with Spatial Correlation
We propose a novel analytical framework for evaluating the coverage
performance of a millimeter wave (mmWave) cellular network where idle user
equipments (UEs) act as relays. In this network, the base station (BS) adopts
either the direct mode to transmit to the destination UE, or the relay mode if
the direct mode fails, where the BS transmits to the relay UE and then the
relay UE transmits to the destination UE. To address the drastic rotational
movements of destination UEs in practice, we propose to adopt selection
combining at destination UEs. New expression is derived for the
signal-to-interference-plus-noise ratio (SINR) coverage probability of the
network. Using numerical results, we first demonstrate the accuracy of our new
expression. Then we show that ignoring spatial correlation, which has been
commonly adopted in the literature, leads to severe overestimation of the SINR
coverage probability. Furthermore, we show that introducing relays into a
mmWave cellular network vastly improves the coverage performance. In addition,
we show that the optimal BS density maximizing the SINR coverage probability
can be determined by using our analysis
Uplink packet scheduling in cellular networks with relayingâcomparative study
Deployment of intermediate relay nodes in cellular networks, e.g. UMTS/ HSPA, has been proposed for service enhancement, which is of particular importance for uplink users at the cell edge suffering from low power capacity and relatively poor channel conditions. In this paper, we propose and investigate a number of uplink packet scheduling schemes deploying the relay functionality in different ways. Using a combined packet and flow level analysis capturing the specifics of the scheduling schemes and the random behavior of the users (initiation and completion of flow transfers), the performance of the various schemes is evaluated and compared to a reference scenario where relaying is not used. The main performance measures considered in our study are realized data rates and mean flow transfer times. Interestingly, considering flow transfer times, it is found that the use of relay nodes is not only particularly beneficial for users at the cell edge but also has a strong, positive effect on the performance of users at other locations not transmitting via a relay node
Linear Precoders for Non-Regenerative Asymmetric Two-way Relaying in Cellular Systems
Two-way relaying (TWR) reduces the spectral-efficiency loss caused in
conventional half-duplex relaying. TWR is possible when two nodes exchange data
simultaneously through a relay. In cellular systems, data exchange between base
station (BS) and users is usually not simultaneous e.g., a user (TUE) has
uplink data to transmit during multiple access (MAC) phase, but does not have
downlink data to receive during broadcast (BC) phase. This non-simultaneous
data exchange will reduce TWR to spectrally-inefficient conventional
half-duplex relaying. With infrastructure relays, where multiple users
communicate through a relay, a new transmission protocol is proposed to recover
the spectral loss. The BC phase following the MAC phase of TUE is now used by
the relay to transmit downlink data to another user (RUE). RUE will not be able
to cancel the back-propagating interference. A structured precoder is designed
at the multi-antenna relay to cancel this interference. With multiple-input
multiple-output (MIMO) nodes, the proposed precoder also triangulates the
compound MAC and BC phase MIMO channels. The channel triangulation reduces the
weighted sum-rate optimization to power allocation problem, which is then cast
as a geometric program. Simulation results illustrate the effectiveness of the
proposed protocol over conventional solutions.Comment: 30 pages, 7 figures, submitted to IEEE Transactions on Wireless
Communication
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