• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.383-388
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• 2009

In this paper, we focus on the retransmission following transmission failure in impulse radio ultra wideband (IR-UWB). The reasons of transmission failure are classified and a new 'selfish' retransmission protocol is proposed because time hopping can support multiple transmissions at the same time. Selfish retransmission protocol retransmits packets immediately without any kind of timeout or channel observation. Simulation results show that the proposed protocol improves throughput up to 50% and decreases retransmission delay also up to 70%, compared to a conventional retransmission system in IR-UWB.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.36-44
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• 2016

In this paper, an Impulse Radio-Ultra Wide band RF Transceiver for WBAN applications is implemented in $0.18{\mu}m$ CMOS technology. The designed RF transceiver support 3-5GHz UWB low band and employs OOK(On-Off Keying) modulation. The receiver employs non-coherent energy detection architecture to reduce complexity and power consumption. For the rejection of the undesired interferers and improvement of the receiver sensitivity, RF active notch filter is integrated. The VCO based transmitter employs the switch mechanism. As adapt the switch mechanism, power consumption and VCO leakage can be reduced. Also, the spectrum mask is always same at each center frequency. The measured sensitivity of the receiver is -84.1 dBm at 3.5 GHz with 1.579 Mbps. The power consumption of the transmitter and receiver are 0.3nJ/bit and 41 mW respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1045-1050
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• 2008

In this paper presents a CMOS RF receiver for IR-UWB wireless communications is presented. The impulse radio based UWB receiver adopts the non-coherent demodulation that simplifies the receiver architecture and reduces power consumption. The IR-UWB receiver consists of LNA, envelop detector, VGA, and comparator and the receiver including envelope detector, VGA, and comparator is fabricated on a single chip using $0.18{\mu}m$ CMOS technology. The measured sensitivity of IR-UWB receiver is down to -70 dBm and the BER $10^{-3}$, respectively at data rate 1 Mbps. The current consumption of IR-UWB receiver except external LNA is 5 mA at 1.8 V.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.386-393
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• 2003

Future wireless networks are expected to achieve high bit rates at low cost, enabling multimedia and QoS-based services over the wireless medium. The impulse radio ultra-wide band (IR-UWB) technique is a promising candidate in the deployment of such networks, thanks to its potential robustness and capacity. In the past, most of the UWB research focused on hardware and physical layer aspects in order to solve the technological challenges posed by IR-UWB. UWB peculiar characteristics may, however, also stimulate innovative higher layers’ design. This work addresses MAC issues for UWB communication systems. Key areas such as medium sharing, MAC organization, packet scheduling and power control are reviewed. The impact of UWB on the above functions is discussed, and areas which require UWB specific design are identified. Finally, novel MAC functions enabled by UWB specific features, i.e., precise ranging and positioning, are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1086-1095
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• 2007

This paper proposes a novel non-coherent TOA estimation scheme using multiple correlation process on the existence of multiple simultaneously operating piconets (SOPs). Impulse radio-ultra wideband (IR-UWB) based on direct sequence spread spectrum (DSSS) using Gold sequence is employed in order to discriminate each piconet. In order to enhance the characteristic of correlation, this paper presents the method of multiple mask operation (MMO). The time of arrival (TOA) of direct line of sight (DLOS) path is estimated via two step coarse/fine timing detection. To verify the performance of proposed scheme, two distinct channel models approved by IEEE 802.15.4a Task Group (TG) are considered. According to the simulation results, it could conclude that the proposed scheme have performed better performance than the conventional method well even in densed indoor multi-path environment as well as in the existence of multiple SOPs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.657-663
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• 2009

A fully integrated single ended IR-UWB receiver is implemented using 0.18 ${\mu}m$ CMOS technology. The UWB receiver adopts the non-coherent architecture, which simplifies the RF architecture and reduces power consumption. The receiver consists of single-ended 2-stage LNAs, S2D, envelope detector, VGA, and comparator. The measured results show that sensitivity is -80.8 dBm at 1 Mbps and BER of $10^{-3}$. The receiver uses no external balun and the chip size is only $1.8{\times}0.9$ mm. The consumed current is very low with 13 mA at 1.8 V supply and the energy per bit performance is 23.4 nJ/bit.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.38-44
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• 2008

In this paper, we introduce an low complexity and low power IR-UWB (impulse radio ultra wideband) baseband transceiver for wireless sensor network. The proposed baseband, implemented by TSMC 0.18um CMOS technology, has a simple structure in which a simplified packet structure and a digital synchronizer with 1-bit sampler to detect incoming pulses are used. Besides, clock gating method using gated clock cell as well as customized clock domain division can reduce the total power consumption drastically. As a result, the proposed baseband has about 23K digital gates with an internal memory of 2Kbytes and achieves about 1.8mW@1Mbps power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.909-916
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• 2008

In this paper, we propose and analyze M-ary pulse order time hopping multiple access ultra wideband (PO-THMA UWB) system using modified Hermite polynomial (MHP). The MHP pulses have a mutually orthogonal property between different ordered pulses and that property makes simultaneous transmission at the same time slot regardless of collision in the THMA-UWB system. Therefore, we derive the cross-correlation furlction of MHP pulses and analyze the BER of the proposed system and show that the BER performance and the transmission capacity are improved dramatically when compared with those of conventional THMA-UWB system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1765-1767
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• 2016

Non-coherent UWB receivers are promising due to the low hardware complexity while the coherent receiver such as the rake receiver requires the complex hardware to estimate channel characteristics and get the synchronization. In this letter, the block coded modulation scheme as one of the most promising method is enhanced in terms of the performance. The performance enhancement is carried out by the modification of the block structure with unequal frame length for each pulse. Simulation results show that the proposed method has the performance enhancement by the transmission rate or bit error rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.682-687
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• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.