88 research outputs found
Beam-searching and Transmission Scheduling in Millimeter Wave Communications
Millimeter wave (mmW) wireless networks are capable to support multi-gigabit
data rates, by using directional communications with narrow beams. However,
existing mmW communications standards are hindered by two problems: deafness
and single link scheduling. The deafness problem, that is, a misalignment
between transmitter and receiver beams, demands a time consuming beam-searching
operation, which leads to an alignment-throughput tradeoff. Moreover, the
existing mmW standards schedule a single link in each time slot and hence do
not fully exploit the potential of mmW communications, where directional
communications allow multiple concurrent transmissions. These two problems are
addressed in this paper, where a joint beamwidth selection and power allocation
problem is formulated by an optimization problem for short range mmW networks
with the objective of maximizing effective network throughput. This
optimization problem allows establishing the fundamental alignment-throughput
tradeoff, however it is computationally complex and requires exact knowledge of
network topology, which may not be available in practice. Therefore, two
standard-compliant approximation solution algorithms are developed, which rely
on underestimation and overestimation of interference. The first one exploits
directionality to maximize the reuse of available spectrum and thereby
increases the network throughput, while imposing almost no computational
complexity. The second one is a more conservative approach that protects all
active links from harmful interference, yet enhances the network throughput by
100% compared to the existing standards. Extensive performance analysis
provides useful insights on the directionality level and the number of
concurrent transmissions that should be pursued. Interestingly, extremely
narrow beams are in general not optimal.Comment: 5 figures, 7 pages, accepted in ICC 201
Resource Allocation for Device-to-Device Communications in Multi-Cell Multi-Band Heterogeneous Cellular Networks
Heterogeneous cellular networks (HCNs) with millimeter wave (mm-wave)
communications are considered as a promising technology for the fifth
generation mobile networks. Mm-wave has the potential to provide multiple
gigabit data rate due to the broad spectrum. Unfortunately, additional free
space path loss is also caused by the high carrier frequency. On the other
hand, mm-wave signals are sensitive to obstacles and more vulnerable to
blocking effects. To address this issue, highly directional narrow beams are
utilized in mm-wave networks. Additionally, device-to-device (D2D) users make
full use of their proximity and share uplink spectrum resources in HCNs to
increase the spectrum efficiency and network capacity. Towards the caused
complex interferences, the combination of D2D-enabled HCNs with small cells
densely deployed and mm-wave communications poses a big challenge to the
resource allocation problems. In this paper, we formulate the optimization
problem of D2D communication spectrum resource allocation among multiple
micro-wave bands and multiple mm-wave bands in HCNs. Then, considering the
totally different propagation conditions on the two bands, a heuristic
algorithm is proposed to maximize the system transmission rate and approximate
the solutions with sufficient accuracies. Compared with other practical
schemes, we carry out extensive simulations with different system parameters,
and demonstrate the superior performance of the proposed scheme. In addition,
the optimality and complexity are simulated to further verify effectiveness and
efficiency.Comment: 13 pages, 11 figures, IEEE Transactions on Vehicular Technolog
A Genetic Algorithm-based Beamforming Approach for Delay-constrained Networks
In this paper, we study the performance of initial access beamforming schemes
in the cases with large but finite number of transmit antennas and users.
Particularly, we develop an efficient beamforming scheme using genetic
algorithms. Moreover, taking the millimeter wave communication characteristics
and different metrics into account, we investigate the effect of various
parameters such as number of antennas/receivers, beamforming resolution as well
as hardware impairments on the system performance. As shown, our proposed
algorithm is generic in the sense that it can be effectively applied with
different channel models, metrics and beamforming methods. Also, our results
indicate that the proposed scheme can reach (almost) the same end-to-end
throughput as the exhaustive search-based optimal approach with considerably
less implementation complexity
Toward a Gigabit Wireless Communications System
This paper presents the design and the realization of a hybrid wireless
Gigabit Ethernet indoor communications system operating at 60 GHz. As the 60
GHz radio link operates only in a single-room configuration, an additional
Radio over Fiber (RoF) link is used to ensure the communications within all the
rooms of a residential environment. The system uses low complexity baseband
processing modules. A byte synchronization technique is designed to provide a
high value of the preamble detection probability and a very small value of the
false detection probability. Conventional RS (255, 239) encoder and decoder are
used for channel forward error correction (FEC). The FEC parameters are
determined by the tradeoff between higher coding gain and hardware complexity.
The results of bit error rate measurements at 875 Mbps are presented for
various antennas configurations
Wireless wire - ultra-low-power and high-data-rate wireless communication systems
With the rapid development of communication technologies, wireless personal-area communication systems gain momentum and become increasingly important. When the market gets gradually saturated and the technology becomes much more mature, new demands on higher throughput push the wireless communication further into the high-frequency and high-data-rate direction. For example, in the IEEE 802.15.3c standard, a 60-GHz physical layer is specified, which occupies the unlicensed 57 to 64 GHz band and supports gigabit links for applications such as wireless downloading and data streaming. Along with the progress, however, both wireless protocols and physical systems and devices start to become very complex. Due to the limited cut-off frequency of the technology and high parasitic and noise levels at high frequency bands, the power consumption of these systems, especially of the RF front-ends, increases significantly. The reason behind this is that RF performance does not scale with technology at the same rate as digital baseband circuits. Based on the challenges encountered, the wireless-wire system is proposed for the millimeter wave high-data-rate communication. In this system, beamsteering directional communication front-ends are used, which confine the RF power within a narrow beam and increase the level of the equivalent isotropic radiation power by a factor equal to the number of antenna elements. Since extra gain is obtained from the antenna beamsteering, less front-end gain is required, which will reduce the power consumption accordingly. Besides, the narrow beam also reduces the interference level to other nodes. In order to minimize the system average power consumption, an ultra-low power asynchronous duty-cycled wake-up receiver is added to listen to the channel and control the communication modes. The main receiver is switched on by the wake-up receiver only when the communication is identified while in other cases it will always be in sleep mode with virtually no power consumed. Before transmitting the payload, the event-triggered transmitter will send a wake-up beacon to the wake-up receiver. As long as the wake-up beacon is longer than one cycle of the wake-up receiver, it can be captured and identified. Furthermore, by adopting a frequency-sweeping injection locking oscillator, the wake-up receiver is able to achieve good sensitivity, low latency and wide bandwidth simultaneously. In this way, high-data-rate communication can be achieved with ultra-low average power consumption. System power optimization is achieved by optimizing the antenna number, data rate, modulation scheme, transceiver architecture, and transceiver circuitries with regards to particular application scenarios. Cross-layer power optimization is performed as well. In order to verify the most critical elements of this new approach, a W-band injection-locked oscillator and the wake-up receiver have been designed and implemented in standard TSMC 65-nm CMOS technology. It can be seen from the measurement results that the wake-up receiver is able to achieve about -60 dBm sensitivity, 10 mW peak power consumption and 8.5 µs worst-case latency simultaneously. When applying a duty-cycling scheme, the average power of the wake-up receiver becomes lower than 10 µW if the event frequency is 1000 times/day, which matches battery-based or energy harvesting-based wireless applications. A 4-path phased-array main receiver is simulated working with 1 Gbps data rate and on-off-keying modulation. The average power consumption is 10 µW with 10 Gb communication data per day
Demonstration of M-QAM OFDM bidirectional 60/25 GHz transmission over 10 km Fiber, 100 m FSO and 2 m radio seamless heterogeneous fronthaul link
[EN] In this paper, we demonstrate the experimental transmission of 16-and 64-quadrature amplitude modulation (QAM) Long Term Evolution -Orthogonal Frequency Division Multiplexing (LTE-OFDM) signals by using mil-limetre wave frequencies at 60 GHz and 25 GHz for downlink and uplink, respectively, over a heterogeneous optical fronthaul infrastructure. A directly modulated laser was employed for both links, which enables the cost-effective full-duplex system proposal. The bidirectional link consists of a 10 km of single mode fiber, a 100 m long free space optics channel and 2 m long wireless radio link, which brings flexibility for future wireless networks. The error vector magnitude (EVM) parameter is measured for a range of the received optical and electrical power as well as the signal-to-noise ratio. A comprehensive estimation of penalty factors in the different network segments is presented. The successful transmission over the whole proposed network with the EVM below the required limit of 9 % for 64-QAM with 20 MHz bandwidth is experimentally demonstrated for the received optical power of-2.7 dBm and-1 dBm for the downlink and uplink, respectively.The research has been supported by the CTU in Prague SGS20/166/OHK3/3T/13, project from Ministry of Industry and Trade in Czech Republic (FV40089) and within COST action CA19111 (NEWFOCUS) . It has also been funded by the regional project from Generalitat Valenciana PROMETEO 2021/015 and Grant RTI2018-101658-B-I00 FOCAL by MCIN/AEI/10.13039/501100011033 and ERDF "A way of making Europe".Vallejo, L.; Ortega Tamarit, B.; Mora Almerich, J.; Nguyen, D.; Guerra, C.; Bohata, J.; Spacil, J.... (2023). Demonstration of M-QAM OFDM bidirectional 60/25 GHz transmission over 10 km Fiber, 100 m FSO and 2 m radio seamless heterogeneous fronthaul link. Optical Fiber Technology. 77. https://doi.org/10.1016/j.yofte.2022.1031617
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