Kyongkuk Cho

On the general BER expression of one- and two-dimensional amplitude modulations

Quadrature amplitude modulation (QAM) is an attractive technique to achieve high rate transmission without increasing the bandwidth. A great deal of attention has been devoted to the study of bit error rate (BER) performance of QAM, and approximate expressions for the bit error probability of QAM have been developed in many places in the literature. However, the exact and general BER expression of QAM with an arbitrary constellation size has not been derived yet. We provide an exact and general closed-form expression of the BER for one-dimensional and two-dimensional amplitude modulations, i.e., PAM and QAM, under an additive white Gaussian noise (AWGN) channel when Gray code bit mapping is employed. The provided BER expressions offer a convenient way to evaluate the performance of PAM and QAM systems for various cases of practical interest. Moreover, simple approximations can be found from our expressions, which are the same as the well-known approximations, if only the dominant terms are considered.

Bit error probability of M-ary quadrature amplitude modulation

So far the general expression of bit error rate (BER) has not been derived for M-ary square quadrature amplitude modulation (QAM). In this paper, a generalized closed-form BER expression of M-ary square QAM with Gray code bit mapping is derived and analyzed in the presence of additive white Gaussian noise (AWGN) channel.

Resource alloation for orthogonal and co-channel femtocells in a hierarchical cell structure

This paper focuses on the frequency allocation (FA) schemes between a macro-cell base station (MBS) and femtocells in a hiearachical cell structure. We present two simple methods among the many cases of FA schemes. One is a co-channel FA scheme in which frequency band is shared between MBS and femtocells. The other is an orthogonal FA scheme in which the frequency is separately allocated between MBS and femtocells. Through a computer simulation, we demonstrate the orthogonal FA scheme has a coverage extension compared with co-channel FA scheme as well as MBS without femtocells.

BER analysis of arbitrary rectangular QAM

M-ary quadrature amplitude modulation (M-ary QAM) is an attractive technique to achieve high rate transmission without increasing the bandwidth in wireless communication systems. A great deal of attention has been devoted to the study of bit error rate (BER) performance of M-ary square QAM constellations. Approximate expressions for bit error probabilities of M-ary square QAM have recently been developed by J.J. Lu et al. (1999) and L. Yang and L. Hanzo (2000) based on signal-space concepts and recursive algorithms, respectively. However, it is only recently that an exact generalized closed form expression for the BER of M-ary square QAM constellation has been developed (see Yoon, D. et al., IEEE VTC Fall 2000, vol.5, p.2422-7, 2000). We extend that previous work of ours to an arbitrary I/spl times/J rectangular QAM (R-QAM) scheme. A general closed form expression for the exact BER performance of an arbitrary I/spl times/J R-QAM with Gray code mapping is derived and analyzed under an additive white Gaussian noise (AWGN) channel. The BER performance is also analyzed under fading channels. It is shown that there is a noticeable deviation in the BER performance between the approximation and exact expression over low SNR values.

Performance Analysis of Downlink Inter Cell Interference Coordination in the LTE-Advanced System

In the LTE-Advanced system, cell edge User Equipments (UEs) are affected by interference signals transmitted from other cells. For this reason, an Inter Cell Interference Coordination (ICIC) technique is required. The goal of ICIC is to improve cell coverage and increase cell edge throughput. In this paper, through a system level simulation, we show the user throughput of each Multiple-Input Multiple-Output (MIMO) transmission mode according to ICIC algorithms, and analyze the practical effects of ICIC on the throughput performance of various MIMO modes.

An Approximated Soft Decoding Algorithm of 16-APSK Signal for DVB-S2

In this paper, we propose a pragmatic soft decoding algorithm for 16-APSK (amplitude phase shift keying) signal of DVB-S2 (digital video broadcasting-satellite, second generation). Because the 16-APSK is one of non-constant envelope modulation schemes with two rings (inner and outer) in the constellation mapped with imperfect Gray code, we use a pragmatic and statistical approach to obtain bitwise metrics of a symbol codeword. The proposed algorithm can be used for binary iterative decoder with LDPC (low density parity check) or turbo code. We also show the proposed algorithm has better performance comparing to the well-known max-log-MAP algorithm through computer simulation with iterative turbo decoder.

Error Performance Analysis of

In this paper, we derive new exact and general expressions for the symbol error rate (SER) and bit error rate (BER) of M-ary θ-quadrature amplitude modulation (QAM) for M = 2l , I ≥ 4, based on not only square-QAM (SQAM) for M = 22l, I ≥ 2 but cross-QAM (CQAM) as well, for M = 22l+1, I ≥ 2 in additive white Gaussian noise (AWGN) and various fading channels; we also present the optimum angle and constellation of M-ary θ-QAM. Through computer simulations, we confirm the results of the theoretical analysis. Because the SER and BER expressions are provided in terms of 2-D Gaussian Q-function in AWGN and various fading channels, they will be very useful for numerical evaluations in various cases of practical interest in QAM systems.

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The introduction of fixed relays is expected to be inevitable as 4G wireless communications coverage is expanded and data processing ratios enhanced, and for reducing costs of base station extension and backhaul communication network holding. Additional interference is an unwanted concomitant of adding many fixed relays to the existing cellular system without an efficient frequency allocation scheme. We propose an efficient frequency allocation scheme for avoiding co-channel interference between cells/sectors when installing fixed relays on cellular systems. The proposed frequency allocation scheme can minimize the co-channel interference between cells/sectors by not sharing a frequency band among neighboring fixed relays, or between the base station and fixed relays, and instead using different frequency bands in sectors.

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This paper designs a data link between a Lunar Orbiter (LO) and an Earth Station (ES), and analyzes the downlink performance of a space communications system for lunar exploration, conforming to the recommendations by the Consultative Committee for Space Data Systems (CCSDS). The results provided in the paper can be useful references for the design of reliable communication link for the Korean lunar exploration in the near future.

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IMT-Advanced system proposed by ITU-R for next generation mobile communications has the technical requirements of the performances of an improved broadcast, a multicast and a VoIP by supporting the transmission rates up to 100 Mbps for high mobility and 1 Gbps for low mobility. LTE-Advanced system is one of the leading candidates of IMT-Advanced systems and many telecommunications industries will introduce LTE-Advanced system widely. Therefore it is important to examine the performance of the technologies applied in LTE-Advanced system. In this paper, we analyze the performances of the transmission modes in the downlink spatial channel model of LTE-Advanced system.