• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.8
• /
• pp.1647-1653
• /
• 2004

In a contention-based wireless LAN protocol, maximization of channel utilization and fair bandwidth allocations are main topics to deal with. But it is very difficult to achieve these two goals simultaneously. Many studies have been done to achieve these goals. In this paper we propose a control mechanism to support fair transmissions among traffic classes in IEEE 802.11e Wireless LAN. The proposed algorithm uses short-term and long-term transmission times of each traffic classes to control their $CW_{min}$ for fairness. The proposed algorithm don't need to know the exact number of nodes in the networks to support fairness as other studies do. Furthermore any modifications in AP and mobile hosts are not required.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.1
• /
• pp.70-75
• /
• 2015

With the development of communication technologies and smartphone, requirements of positioning accuracy for LBS (Location Based Service) are becoming increasingly important. LBS is a service which offers the information or entertainment based on a location to users. Therefore, positioning is very important for LBS. Among many positioning methods, IEEE 802.11 WLAN positioning measures the distance using the RSSI (Received Signal Strength Indicator) attenuation log model. Thus in order to enhance positioning, we modify the IEEE 802.11 RSSI attenuation log model by adaptive weighting method. In this paper, we propose improved IEEE 802.11 RSSI attenuation log model for enhanced indoor positioning.

• The KIPS Transactions:PartC
• /
• v.12C no.3 s.99
• /
• pp.387-394
• /
• 2005

Every MAC (Medium Access Control) sub-layers of IEEE 802.11x, including IEEE 802.11e, defines Connection-based and CF (Contention Free)-based service functions in common. In this paper, a New-CF method is proposed. In the proposed method, conventional Round Robin method, which is used as a polling method by IEEE 802.11x PCF (Point Coordination Function) or IEE 802.11e HCCA, is modified to give weights to channels with heavier traffic load and to provide those weighted channels with more services. Based on NS-2 simulations, it is verified the proposed method shows better throughput in general, particularly under unbalanced traffic load conditions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.8
• /
• pp.1613-1621
• /
• 2015

This paper analyzes the rate adaptation scheme and suggests applicable strategy of the MCS(Modulation and Coding Scheme) for improving DCF throughput in the IEEE 802.11ad and 802.11ad wireless LAN. IEEE 802.11ac and 802.11ad wireless LAN provide MCS technique that dynamically adjusts modulation level and code rate to the time-varying channel conditions in order to obtain considerably high data rates. But these standards did not provide rate adaptation algorithm, so this paper surveyes rate adaptation algorithm and suggests MCS scheme applied to IEEE 802.11ac and 802.11ad wireless LAN. Specially A MAC(Medium Access Control) layer throughput is evaluated over error-prone channel in the IEEE 802.11ac-based wireless LAN. In this evaluation, DCF (Distributed Coordination Function) protocol and A-MPDU (MAC Protocol Data Unit Aggregation) scheme are used. Using theoretical analysis method, the MAC saturation throughput is evaluated with the PER (Packet Error Rate) on the condition that the number of station, transmission probability, the number of parallel beams and the number of frames in each A-MPDU are variables.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
• /
• v.4 no.2
• /
• pp.9-17
• /
• 2005

Coexistence of different wireless systems that share the 2.4 GHz ISM frequency band is becoming one of the most important issue. This paper presents a model of the interference that IEEE 802.11b affected by IEEE 802.15.4. The packet error rate (PER) of IEEE 802.11b under the interference of IEEE 802.15.4 is analyzed. The PER is obtained by using the bit error rate (BER) and the collision time. Further, this paper suggests a packet length to reduce the effect of the IEEE 802.15.4 interference and obtain a maximum throughput of the IEEE 802.11b. The analytical results are validated using simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.4 s.346
• /
• pp.52-57
• /
• 2006

In this paper, the triple-band planar monopole antennas are designed for cellular communication, WiBro and WLAN(IEEE802.11b/g) communication and WLAN(IEEE802.11a) communication of 5GHz band to using filled mobile convergence subscriber unit. Various types of antennas are designed and examined experimentally as bended in the low and middle band radiation elements to decrease antennas size and increased the width of radiation elements to improve bandwidth The proposed antennas are reduced by 11% in antenna size with bended low-band radiation elements down and are extended by $30%{\sim}40%$ in bandwidth by increasing the width of the radiation element at 800MHz band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.80-83
• /
• 2010

This paper describes an analysis of decoding performance of multi-mode LDPC(Low Density Parity Check) decoder which supports three block lengths (648, 1296, 1944) and four code rates (1/2, 2/3,3/4, 5/6) for IEEE 802.11n WLAN system. A fixed-point model of LDPC decoder which adopts min-sum algorithm and layered decoding scheme is implemented using Matlab. From fixed-point simulation results for various bit-width parameters such as internal bit-width, bit-width of integer and fractional parts, an optimal design condition and decoding performance of LDPC decoder are analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.2
• /
• pp.432-438
• /
• 2011

This paper describes an analysis of optimal design conditions of multi-mode LDPC(low density parity check) decoder which supports three block lengths (648, 1296, 1944) and four code rates (1/2, 2/3, 3/4, 5/6) for IEEE 802.11n WLAN system. A fixed-point model of LDPC decoder, which adopts min-sum algorithm and layered decoding scheme, is implemented using Matlab. From fixed-point simulation results for various bit-width parameters such as internal bit-width, integer/fractional part bit-widths, optimal design conditions and decoding performance of LDPC decoder are analyzed.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.46 no.4
• /
• pp.31-41
• /
• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To improve these limit, in this paper, we First, we propose priority polling algorithm which additionally considers the size of MSI and TXOP based on EDD algorithm to increase number of QSTAs. We also propose a dual token bucket TXOP allocation algorithm to reduce congestion caused by stations which enters network with considerable delay variance. TSPEC parameters, Maximum Burst Size (MBS) and Peak Data Rate (PR), are applied to design depth and token generation rate of two buckets. Simulation results show that the proposed algorithm has much higher performance compared with reference and SETT-EDD scheduler in terms of throughput and delay.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.517-520
• /
• 2003

Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology for high speed multimedia communication in a frequency selective multipath channel. In this paper, Software IPs for the synchronizer of IEEE 802.11a Wireless LAN system are designed and optimized for TI's TMS320C6201 fixed point DSP. As a result of the execution cycles of the target DSP for each functions of the system, an efficient HW/SW partitioning method can be considered.