Digital Signal Processing On Wireless Communication Oriented Microprocessor Design

The unforeseen development of the mobile communication, Internet applications,and portable computer techniques, not only changes the way of human life, but alsobrings a rapid rise in the number of mobile users worldwide. As far as China isconcerned, the number of mobile users has been more than one billion, and thecontradictions between the growing number of mobile users and the limited spectrumresources become irreconcilable. An irresistible means to solve this contradiction is toeffectively utilize the spectrum resources and to improve the spectrum utilization at thesame time.CR technique can use the licensed spectrum resources when the authorized user(also referred as the primary user) is idle, and therefore it is considered to be a valid anddesirable method to solve the problem of the shortage of spectrum resources. CRtechnique has three working modes: interweave, underlay and overlay modes. Thesethree modes correspond to the three key techniques: spectrum sensing, spectrum sharingand spectrum management respectively. We focus on interweave mode and underlaymode in this thesis and further study the energy detection in interweave mode andpower allocation method based on water-filling algorithm in underlay mode. Theinnovative contributions have been proposed in this thesis as follows:1. An energy detection algorithm with adaptive threshold is proposed in this paper.The traditional energy detection algorithm uses a fixed energy threshold; its mainpurpose is to guarantee the spectrum resources of the primary user undisturbed. Theadaptive energy detection algorithm focuses on the unauthorized users (also calledcognitive radio users, or secondary users).The secondary user adjust the adaptivethreshold by optimizing the secondary user’s transmission capacity under theinterference constraint.2. We combine the adaptive energy detection algorithm with multi-user cooperativedetection and propose a simple data fusion mechanism. In cognitive radio networks, thetraditional data fusion techniques include the "and" rule,"or" rule and majority rule.These techniques are simple and effective, but have some shortcomings more or less. The overall performance of these techniques is not satisfying. In this paper, themulti-users energy detection algorithm which considers the secondary users’ reliabilitieswith majority rules promotes the detection performance.3. We propose a parallel-shift water-filling algorithm and a fast power allocationalgorithm based on parallel-shift water-filling algorithm in CR network in this paper.The traditional water-filling algorithm uses a binary search to search the water line, andthis method allocates power each times while searching the water line. So the existmethod is not only high time-consuming, but also high computational complexity. Inthis paper we find the parallel-shift property of water-filling algorithm and adjust thepower allocation linearly after the first power allocation, so that we avoid repeating thepower allocation by searching the water line, which can reduce the complexity and savethe processing time. The fast power allocation algorithm based on parallel-shiftwater-filling can also reduce the processing time and complexity.