Abstract—We introduce a novel method of digital modulation with a high spectral efficiency, called the Angle (Exponentially) Modulated M − ary Quadrature Amplitude Modulation (EM- MQAM). The main advantage of EM-MQAM is an ability to transmit a multilevel 2-D MQAM constellation as a constant envelope signal. It makes EM-MQAM a preferred technique for application in multipath fading channel since no amplitude discrimination in the receiver is needed. The transmission bandwidth and BER performance of EM-MQAM have been analyzed. Despite of the fact that EM-MQAM requires as twice as much of the transmit bandwidth compared to the conventional MQAM, it provides reasonable trade-off between transmit bandwidth and BER performance. Furthermore, EM-MQAM requires just 1 dB of extra transmit power if the order of original MQAM increases fourfold. I. I NTRODUCTION M-ary Phase Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) are conventional well- known modulation techniques providinghigh spectral efficiency of data transmission over limited channel bandwidth [1], [2]. By applying them at the given bit transmission rate b R , the transmitted bandwidth can be properly adjusted to available channel bandwidth by choosing appropriate number of transmitted signal levels, which exponentially depend on the number of mapping information bits k, i.e., k M 2 = . Both MPSK and MQAM have the same spectral efficiency, where the latter is defined as a ratio of bit rate to transmitted bandwidth. The penalty of higher data transmission rate over band- limited channel is an increasing of average transmitted power required to maintain the same performance level expressed in a Bit Error Rate (BER). As shown in [1], [2], [3], for the AWGN channel the doubling of the level numbers requires approximately 6 dB additional transmitted power for MPSK and 3 dB for MQAM (M > 4). Hence, in terms of transmitted power the MQAM outperforms MPSK, especially for the large M; however, using MQAM in multipath fading propagation environment, especially in the frequency selective channel, leads to serious difficulties in reconstruction of multiple amplitude levels by receiver due to large fluctuatio in the received signal amplitude [1], [4]. Therefore, on the o hand, detection of MPSK signal in a fading radio channel is easier than MQAM due to constant envelope; on the o hand, MQAM outperforms MPSK in BER performance i AWGN channel. It would be very attractive to develop modulation technique that has constantenvelope of transmitted signal similar to MPSK, and at the same time th BER performance similar to that of MQAM. Recently, such kind of modulation technique, namely Ang (Exponentially) Modulated M-ary Quadrature Amplitude Modulation (EM-MQAM) was proposed [5]. EM-MQAM, that includes either PM-MQAM or FM-MQAM [6], abso the advantages of both MPSK and MQAM. EM-MQAM accommodated to transmit the MQAM symbols with consta envelop amplitude, and at the same time, it has the sp efficiency and BER performance comparable to conventiona MQAM. In this paper we address the transmitted bandwidth of EM MQAM both theoretically and by simulation. The BER performance is obtained and analyzed. The paper organized follows.Section II describes the EM-MQAMmodulation technique. The Sections III and IV investigate the transmitt bandwidth and BER performance. Section V summarizes ou work. II. PM-MQAM SIGNAL DESIGN We refer to a general form of exponentially modulate (EM) bandpass signal expressed as [1], [6] )] ( 2 cos[ ) ( t t f A t c c ξ + π = ϕ (1) where c A and c f are the carrier amplitude and the carrier frequency, respectively, and ) (t ξ is a time varying angle component defined as follows ° ° ¯ ° ° ® - τ τ = ξ ³ ∞ − , , ) ( , , ) ( ) ( FM d m k PM t m k t t f p (2) Performance Analysis of Angle Modulated MQAM Transmission Techniques Viktor V. Zaharov Polytechnic University of Puerto Rico, San Juan, Puerto Rico, Email: vzaharov@pupr.edu Alexander B. Kokhanov Ukraine State Academy of Communications, Odessa, Ukraine Email: skoh@mail.ru 1-4244-0523-8/07/$20.00 ©2007 IEEE 520