Modem Recognition Algorithm for Software Defined Radio Base Station

Mobile communications industry continuously evolves the wireless standards from 2G to 2.5G, 3G and then further onto 4G. Each generation differs significantly in link layer and physical layer protocol standards causing problems to subscribers, network operators and equipment vendors. The root cause of the problem is that the current hardware is not flexible enough to support future communication systems. To address this issue, Software Defined Radio (SDR) plays an important role to bridge the hardware limitation. SDR is the integration of software and hardware technology that promises cost effective seamless networkability and value added services between end users and network operators. Modem is the heart of a SDR system; it functions as an incoming modulation recogniser, multi-format demodulator, outgoing modulation recogniser, and multi-format modulator. These functions generally require high overhead like extensive memory, high-level database, and efficient and uninterrupted power management system. Because of this, the Base Station (BS) is preferred to handle the modem function since it has the capacity to allocate the required overhead and maintenance. The implementation of SDR modem function in the BS provides the flexibility for the subscriber or Mobile Station (MS) to communicate with any mobile communication systems available in the market. However to support all available communication systems, it is necessary to make some modifications to the MS, which is configured through software download from wireless terminals. In addition, the proposed modem algorithm will also assist in accelerating the SDR deployment since the main attention of the SDR deployment focuses on the BS. The proposed algorithm was developed based on 8th order statistical moment and the technique was chosen based on the research work done by Keith et al [15]. However, in this thesis the former technique is modified to accommodate non-equally likely received signal recognitions, wider range of modulation scheme, and modulation recognition efficiency for lower channel SNR. The performance of the algorithm was verified in the presence of white Gaussian noise and Rayleigh Fading. The statistical order was classified based on the latency and the effectiveness of recognition among the identified modulation schemes. The average latency for each QPSK, MSK, QASK, and BPSK modulation scheme is approximately 20ms. As a whole, the proposed modem recognition algorithm demonstrated successful recognition of QPSK, MSK, QASK, and BPSK for a lower-bound channel SNR greater than 5dB with average processing time of approximately 75ms.

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