Seungkeun Park

An alternative expression for the symbol-error probability of MPSK in the presence of I/Q unbalance

This letter provides a new expression for the probability of the phase angle between two vectors perturbed by Gaussian noise with in-phase/quadrature-phase (I/Q) unbalance, in order to simplify the analysis of the error probabilities of M-ary phase-shift keying (MPSK). The error probabilities, symbol-error rates, or bit-error rates for MPSK with I/Q balance or unbalance, can be presented straightforwardly from the derived expression. Because the newly derived result is provided in terms of the conventional first-order Gaussian Q-function and the joint Gaussian Q-function with a correlation coefficient dependent on M, it readily allows rapid evaluation for various cases of practical interest.

Experiments on radio interference between wireless LAN and other radio devices on a 2.4 GHz ISM band

Recently, the current technology, WLAN a data communication device receiving worldwide attention, is operated on a 2.4 GHz ISM band. But since the ISM band is an unlicensed band used in a variety of low-power devices, there is a concern about radio interference between systems using the ISM band. With regard to this, IEEE 802.15 TG2 is operated on the basis of frequency coordination considering the radio interference between WLAN and Bluetooth [http:www.ieee802.org/15/pub/TG2.html]. However, there is insufficient research on the radio interference between WLAN and other radio devices. Therefore, in this paper, we explain the results of experiments conducted on the radio interference between the WLAN and other radio devices operated on a 2.4 GHz ISM band. Radio interference experiments were performed on the microwave oven which is easy to come across in our everyday living; the plasma lighting system (PLS), which is installed in hotels and other common places; and the video transmission device used in the wireless remote control robot for detecting explosives, which is operated in the airport, a hot spot area of WLAN. The results of the experiments will be utilized as data for more effective operation of WLAN.

SEP performance of coherent MPSK over fading channels in the presence of phase/quadrature error and I-Q gain mismatch

This letter presents a joint approach to the symbol-error probability (SEP) of coherent M-ary phase-shift keying in a situation where the phase error, quadrature error, and in-phase-quadrature (I-Q) gain mismatch problems take place all concurrently over an additive white Gaussian noise and arbitrary fading channel. A set of equations that characterizes the conditional SEP on an instantaneous fading signal-to-noise ratio is derived in the form of the Craig representation.

Analysis of spectrum channel assignment for IEEE 802.11b wireless LAN

The paper analyzes the channel assignment of IEEE 802.11b wireless LANs operated on the 2.4 GHz ISM band. The tests used to analyze the radio interference between wireless LAN channels are divided into a cable RF test and a radiated RF test. The measurements for the radiated RF test were performed in an office and a hotel conference room. The measurement results show that the performance of a wireless LAN varies greatly with the model. The adjacent channel gain margin between channels 6 and 10 is about 23 dB and that for channels 10 and 11 is about 7 dB. The coupling effect of wireless LANs causes a maximum throughput reduction of 2 Mbps. The interference effect of the conventional 3-channel separated channel and that of the 4-channel separated channel show very different results according to the installation environment. These result are attributed to the fact that the adjacent channel gained a margin of about 7 dB between channels 10 and 11 and cannot cover the impact by the location and observation of wireless LANs and the deviation of the antenna coupling effect. Therefore, the channel separation of either 3 or 4 for APs on a co-site is suitable, but it has been judged to depend on the performance and installation environment of each wireless LAN.

Probability of an arbitrary wedge-shaped region of the MPSK system in the presence of quadrature error

The paper presents a new and simple expression for computing the probability on an arbitrary wedge-shaped region between two different phase angles when the signal vector is perturbed by two-dimensional Gaussian noise in the presence of a quadrature error. The two-dimensional Gaussian Q-function is used to characterize the expression. The expression can be very useful for computing the analytical error probability of the M-ary phase shift keying system operating in various channel environments.

Throughput Performance Optimization of Super Dense Wireless Networks With the Renewal Access Protocol

As a promising solution for handling super dense wireless networks, wireless local area networks (WLANs) have been intensively considered due to their wide availability. However, the contention-based MAC protocol in WLANs should be modified because of its inefficiency. To this end, we consider a recently proposed novel MAC protocol called the renewal access protocol (RAP). With the RAP, we analyze two strategies for resolving collisions efficiently and achieving optimal throughput performance in super dense WLANs: strategies without and with grouping. First, we analyze the asymptotic behavior of the RAP itself (i.e., without grouping) as the number of terminals goes to infinity. We show that the RAP can achieve optimal throughput even in super dense WLANs and the relevant optimal access probability can be derived in a closed form. Second, we propose a grouping strategy in the RAP called the grouped RAP (G-RAP). While a grouping strategy in the IEEE 802.11ah standard is based on time division, our G-RAP is based on transmission attempts. So the G-RAP does not waste channel resources. We show that the G-RAP achieves the optimal network throughput for any group structure if terminals use the optimal access probability that we derive. Our analytical results are validated by simulation.

Performance analysis of symbol error probability for MPSK with an I-Q unbalance over a rician fading channel

Two rotational transformations are used to derive a new expression for the symbol error probability (SEP) of an M-ary phase shift keying (MPSK) with an I-Q unbalance over additive white Gaussian noise (AWGN) and Rician fading channels. We used the new expression to investigate the effect of the I-Q unbalance on the MPSK SEP performance. Our investigation confirms that this approach is a convenient way to evaluate the average SEP of an MPSK for various cases of the Riciaa factor.

Performance analysis of various co-existence methods with Wi-Fi in unlicensed bands

Recently, it is highly issued to extend wireless communication service on licensed band to unlicensed band as a part of effective utilization of the limited spectrum resources. Because Wi-Fi service is widely used in the targeted unlicensed band, the co-existence performances of Wi-Fi with the wireless communication service should be investigated. In this paper, several co-existing methods such as LBE and FBE methods based on listen-before-talk (LBT) and duty cycle (DC) methods are investigated. For the fair sharing spectrum, the number of collisions and latency are derived in situations when various co-existence methods are applying with Wi-Fi. The scenarios are evaluated using Monte-Carlo simulations. According to the simulation results, LBE and FBE have the least effects on collisions and latency of Wi-Fi, respectively. Further more, when Wi-Fi and LBE is co-existed, it shows the best performance for the total devices.

Co-existence analysis of duty cycle method with Wi-Fi in unlicensed bands

For the effective utilization of the limited spectrum resources, it comes into the spotlight to extend the frequency band of wireless communication services such as LTE to unlicensed band. Because Wi-Fi service is widely used in the concerned band, the performance of co-existence should be investigated. Several methods for sharing spectrum are considered and duty cycle (DC) based method is one of the potential candidates. In this paper, co-existence performances of duty cycle method with Wi-Fi are analyzed. The collisions and latency according to the various DC and DC-on times are investigated. Using Monte-Carlo simulations, collisions at first transmission and the cumulated collisions until one transmission per each device is completed are provided. Also, results on latency and the ratio of latency to the total channel occupancy time per device type are presented.

An Extended Pawula F-Function for MPSK Signal Vector Perturbed by Correlated Two-Dimensional Gaussian Noise

This letter presents an extended Pawula F-function for computing the error rate of generalized M-ary phase shift keying (MPSK) system in the presence of phase error, quadrature error, and I-Q gain mismatch over additive white Gaussian noise (AWGN) and fading channels. The extended Pawula F-function conditioned on an instantaneous fading carrier-to-noise ratio (CNR) is derived in the form of the Craig representation.