[0001 ] RELATED APPLICATION; PRIORITY CLAIM This patent application is related to and claims priority from India Patent Application No. 8197/DELNP/2007, filed 23 October 2007, entitled HYBRID ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM AND METHOD [0002] FIELD OP INVENTION [0003] The present invention is related to wireless communication systems. More particularly, the present invention is related to a hybrid orthogonal frequency division multiple access (OFDMA) system and method. [0004] BACKGROUND [0005] It is expected that future wireless communication systems will provide broadband services such as wireless Internet access to subscribers. Such broadband services require reliable and high throughput transmissions over a wireless channel which is time dispersive and frequency selective. The wireless channel is subject to limited spectrum and inter-symbol interference (ISI) caused by multipath fading. Orthogonal frequency division multiplexing (OFDM) and OFDMA are some of the most promising solutions for the next generation wireless communication systems. [0006] OFDM has a high spectral efficiency since the subcarriers used in the OFDM system overlap in frequency and an adaptive modulation and coding scheme (MCS) may be employed across subcarriers. In addition, implementation of the OFDM is very simple because the baseband modulation and demodulation are performed by simple inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) operations. Other advantages of the OFDM system include a simplified receiver structure and excellent robustness in a multipath environment. [0007] OFDM and OFDMA have been adopted by several wireless/wired communication standards, such as digital audio broadcast (DAB), digital audio broadcast terrestrial (DAB-T), IEEE 802.11a/g, IEEE 802.16, asymmetric digital subscriber line (ADSL) and is being considered for adoption in third generation partnership project (3GPP) long term evolution (LTE), cdma2000 evolution, a fourth generation (4G) wireless communication system, IEEE 802.11n, or the like. 2 INTL-441-IN-DIV [0008] One key problem with OFDM and OFDMA is that it is difficult to mitigate or control inter-cell interference to achieve a frequency reuse factor of one. Frequency hopping and subcarrier allocation cooperation between cells have been proposed to mitigate inter-cell interference. However, the effectiveness of both methods is limited. [0009] SUMMARY [0010] The present invention is related to a hybrid OFDMA system and method. The system includes a transmitter and a receiver. The transmitter includes a first spread OFDMA subassembly, a first non-spread OFDMA subassembly and a first common subassembly. The first spread OFDMA subassembly spreads input data and maps the spread data to a first group of subcarriers. The first non-spread OFDMA subassembly maps input data to a second group of subcarriers. The first common subassembly transmits the input data mapped to the first group of subcarriers and the second group of subcarriers using OFDMA. The receiver includes a second spread OFDMA subassembly, a second non-spread OFDMA subassembly and a second common subassembly. The second common subassembly of the receiver processes received data to recover data mapped to the subcarriers using OFDMA. The second spread OFDMA subassembly recovers the first input data by separating user data in a code domain and the second non-spread OFDMA subassembly recovers the second input data. [0011] BRIEF DESCRIPTION OF THE DRAWINGS [0012] Figure 1 is a block diagram of an exemplary hybrid OFDMA system configured in accordance with the present invention. [0013] Figure 2 shows an example of frequency domain spreading and subcarrier mapping in accordance with the present invention. [0014] Figure 3 shows another example of spreading and subcarrier mapping in accordance with the present invention. 3 INTL-441-IN-DIV [0015] Figure 4 shows an example of time-frequency hopping of subcarriers in accordance with the present invention. [0016] Figure 5 is a block diagram of an exemplary time-frequency Rake combiner configured in accordance with the present invention. [0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0018] Hereafter, the terminology "transmitter" and "receiver" includes but are not limited to a user equipment (UE), a wireless transmit/receive unit (WTRU), a mobile station, a fixed or mobile subscriber unit, a pager, a Node-B, a base station, a site controller, an access point or any other type of device capable of operating in a wireless environment. [0019] The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components. [0020] The present invention is applicable to any wireless communication system that utilizes OFDMA (or OFDM) and/or code division multiple access (CDMA), such as IEEE 802.11, IEEE 802.16, third generation (3G) cellular systems, 4G systems, satellite communication systems, or the like. [0021] Figure 1 is a block diagram of an exemplary hybrid OFDMA system 10 including a transmitter 100 and a receiver 200 in accordance with the present invention. The transmitter 100 includes a spread OFDMA subassembly 130, a non-spread OFDMA subassembly 140 and a common subassembly 150. In the spread OFDMA subassembly 130, input data 101 (for one or more users) is spread with a spreading code to generate a plurality of chips 103 and the chips 103 are then mapped to subcarriers. In the non-spread OFDMA subassembly 140, input bit 111 (for one or more different users) is mapped to subcarriers without spreading. [0022] The spread OFDMA subassembly 130 includes a spreader 102 and a first subcarrier mapping unit 104. The non-spread OFDMA subassembly 140 includes a serial-to-parallel (S/P) converter 112 and a second subcarrier mapping unit 114. The common subassembly 150 includes an N-point inverse discrete 4 INTL-441-IN-DIV Fourier transform (IDFT) processor 122, a parallel-to-serial (P/S) converter 124 and a cyclic prefix (CP) insertion unit 126. [0023] Assuming that there are N subcarriers in the system and that K different users communicate at the same time in the system, among K users, data to Ks users is transmitted via the spread OFDMA subassembly 130. The number of subcarriers used in the spread OFDMA subassembly 130 and the nonspread OFDMA subassembly 140 are Ns and N0, respectively. The values of Ns and N0 satisfy the conditions that 0