This thesis addresses two problems in digital baseband design of wireless communication systems, namely, those in Internet of Things (IoT) terminals that support long range communications and those in full-duplex systems that are designed for high spectral efficiency.

IoT terminals for long range communications are typically based on Orthogonal Frequency-Division Multiple Access (OFDMA) and spread spectrum technologies. In order to design an efficient baseband architecture for such terminals, the workload profiles of both systems are analyzed. Since frame detection unit has by far the highest computational load, a simple architecture that uses only a scalar datapath is proposed. To optimize for low energy consumption, application-specific instructions that minimize register accesses and address generation units for streamlined memory access are introduced. Two parameters, namely, correlation window size and threshold value, affect the detection probability, the false alarm probability and hence energy consumption. Next, energy-optimal operation settings for correlation window size and threshold value are derived for different channel conditions. For both good and bad channel conditions, if target signal detection probability is greater than 0.9, the baseband processor has the lowest energy when the frame detection algorithm uses the longest correlation window and the highest threshold value.

A full-duplex system has high spectral efficiency but suffers from self-interference. Part of the interference can be cancelled digitally using equalization techniques. The cancellation performance and computation complexity of the competing equalization algorithms, namely, Least Mean Square (LMS), Normalized LMS (NLMS), Recursive Least Square (RLS) and feedback equalizers based on LMS, NLMS and RLS are analyzed, and a trade-off between performance and complexity established. NLMS linear equalizer is found to be suitable for resource-constrained mobile devices and NLMS decision feedback equalizer is more appropriate for base stations that are not energy constrained.

Historically, wireless communication devices have been developed to process one specific waveform. In contrast, a modern cellular phone supports multiple waveforms corresponding to LTE, WCDMA(3G) and 2G standards. The selection of the network is controlled by software running on a general purpose processor, not by the user. Now, instead of selecting from a set of complete radios as in software controlled radio, what if the software could select the building blocks based on the user needs. This is the new software-defined flexible radio which would enable users to construct wireless systems that fit their needs, rather than forcing to use from a small set of pre-existing protocols.

To develop and implement flexible protocols, a flexible hardware very similar to a Software Defined Radio (SDR) is required. In this thesis, the Intel T2200 board is chosen as the SDR platform. It is a heterogeneous platform with ARM, CEVA DSP and several accelerators. A wide range of protocols is mapped onto this platform and their performance evaluated. These include two OFDM based protocols (WiFi-Lite-A, WiFi-Lite-B), one DFT-spread OFDM based protocol (SCFDM-Lite) and one single carrier based protocol (SC-Lite). The transmitter and receiver blocks of the different protocols are first mapped on ARM in the T2200 board. The timing results show that IFFT, FFT, and Viterbi decoder blocks take most of the transmitter and receiver execution time and so in the next step these are mapped onto CEVA DSP. Mapping onto CEVA DSP resulted in significant execution time savings. The savings for WiFi-Lite-A were 60%, for WiFi-Lite-B were 64%, and for SCFDM-Lite were 71.5%. No savings are reported for SC-Lite since it was not mapped onto CEVA DSP.

Significant reduction in execution time is achieved for WiFi-Lite-A and WiFi-Lite-B protocols by implementing the entire transmitter and receiver chains on CEVA DSP. For instance, for WiFi-Lite-A, the savings were as large as 90%. Such huge savings are because the entire transmitter or receiver chain are implemented on CEVA and the timing overhead due to ARM-CEVA communication is completely eliminated. Finally, over-the-air testing was done for WiFi-Lite-A and WiFi-Lite-B protocols. Data was sent over the air using one Intel T2200 WBS board and received using another Intel T2200 WBS board. The received frames were decoded with no errors, thereby validating the over-the-air-communications.