| In this thesis we examine the optimization of bandwidth efficiency and energy efficiency for a wireless communication system. Typically, increased energy efficiency can be achieved at the expense of decreased bandwidth efficiency. Therefore, we look into a wide variety of topics regarding physical layer designs and detection techniques for communication systems to better understand the system tradeoffs.; To gain insight into the physical layer design of a communication system, we examine the basic building blocks of a transmitter and receiver. At the transmitter side, we investigate the tradeoffs between modulation waveforms when used in conjunction with transmitter nonlinearities, and amplifier energy efficiency when operated at different operating points. A single system performance measure is incorporated. Both the energy efficiency and bandwidth efficiency of a communication system is defined. The performance measure is maximized over a set of modulation techniques and amplifier operating points.; At the receiver side, a nonlinear adaptive processing (NAP) technique for direct-sequence spread-spectrum (DS-SS) system is investigated for impulsive interference suppression. We show the performance of the NAP technique in concatenation with a turbo decoder, which uses the Gaussian metric to decode, can reduce the system complexity without significant performance loss compared to the optimal receiver.; Finally, we investigate detection algorithms and focus on applying the “turbo principle.” The turbo principle achieves great performance gain compared to suboptimum noniterative receiver structures by iteratively exchanging soft information among connected components of a communications system. If we compare the suboptimum iterative receiver with the optimum receiver, the iterative receiver structure is less complex and the performance loss is small. In this thesis, we first apply the iterative module to the joint decoding of turbo codes and M-ary orthogonal modulation. Without much increase in system complexity, significant performance gain is observed for the system with joint decoding when compared to system without joint decoding. Furthermore, we use this iterative structure to estimate the adjacent channel interference (ACI) of a frequency-hop multiple access (FHMA) system. Single-carrier FHMA systems as well as multi-carrier FHMA systems which use orthogonal frequency-division multiplexing (OFDM) for modulation are examined. The proposed system effectively estimates, regenerates, and mitigates the ACI in FHMA networks. As a result, the tone spacing between adjacent users can be reduced to allocate more users in the shared channel, thereby, improving the frequency utilization and bandwidth efficiency of a communication system. |
