## 1 Introduction  
There are several contenders for 5G communication. Some of them are filter bank multicarrier (FBMC), universal filtered multicarrier (UFMC) [1; 2; 3], non-orthogonal multiple access (NOMA) [4; 5], filtered orthogonal frequency division multiplexing (f-OFDM) [6] and generalized frequency division multiplexing (GFDM) [7]. Out of these, GFDM, which is a non-orthogonal modulation technique, adequately addresses the shortcomings of OFDM for the next generation of 5G networks [7]. Its benefits include flexibility, minimal out-of-band (OOB) emissions, and a higher spectrum efficiency [8]. A heterogeneous network with a variety of competing technologies, such as D2D communication, millimeter waves, multiple input multiple output (MIMO), massive MIMO, femtocells, and Pico cells is anticipated for 5G [9]. To lessen OOB emissions, each GFDM data-block is broken up into subcarriers and sub-symbols, with the subcarriers being filtered by a pulse shaping filter. With its capacity to work with single carrier, FBMC and frequency domain systems that are based on equalization, GFDM is a very flexible time-frequency distribution technique [10]. As GFDM is block-based, it can use several OFDM techniques, including cyclic prefix (CP), to prevent inter-symbol interference. Thus, to mitigate the impacts of multipath at the receiver side, low complexity equalizers can be used in the frequency domain [11]. The loss of orthogonality that results from GFDM subcarriers being filtered via a range of pulse shapes [12] makes them vulnerable to self-interference at the receiver. The resulting complexity in implementation is another drawback of using the flexible waveform. However, since reducing the complexity of systems is an active area of research and computer power is increasing quickly, GFDM turns out to be a promising technique for upcoming high-speed, high performance communications.  
While several authors have focused on reducing the complexity of the GFDM receiver (see, for example, [13; 14]), or minimizing the interference [11; 15; 16; 17], some others have focused on presenting an analysis of BER when using some novel technique in GFDM [18; 19; 20; 21].  
Channel codes have also been used to improve the BER of GFDM [22]. MIMO-GFDM is an active research area which has been employed to improve the BER of a conventional GFDM system. For example, improvement in spectral efficiency and BER via MIMO-GFDM has been proposed in [23]. Low-complexity receivers for MIMO-GFDM have been proposed in [24; 25]. There are several other papers that try to improve the performance of GFDM and/or MIMO-GFDM by using novel techniques, for example, [10; 26; 27; 28]. However, only a handful of work exists that focuses on improving the performance by modifying mapping schemes (one such example is [29]).  
CPM and its subclass, continuous phase frequency shift keying (CPFSK), have been well established in communication systems for more than 40 years [30]. These systems' key benefits are the signal's power and spectrum efficiency, consistent envelope, low levels of out-of-band radiation, flexibility, and phase continuity [31; 32; 33]. One of the factors driving the development of the 5G architecture, which includes enhanced mobile broadband, machine type communication (MTC), and ultra-reliable MTC, is flexibility [34; 35]. In the mapper of traditional GFDM, memoryless modulation techniques such as PSK and QAM are used. A thorough literature search suggests there has been no work that integrates CPM in the mapper of a GFDM. Our main goal in this work is to improve the BER performance of a GFDM by using CPM as a mapper.  
The remaining paper is organized in the following manner. Section 2 presents the details of proposed CPM-GFDM Tx-Rx that comprises CPM modulator and demodulator. Simulation setup and results are presented in Section 3, followed by a discussion in Section 4. The paper is concluded in Section 5.