Research Of Key Techniques Of Radio Resource Allocation In Broadband Wireless Networks

Radio resource and management in wireless and mobile networks plays a key role in system design, compared with that in wireline networks. The design of effective and flexible radio resource allocation (RRA) is the most important issue for wireless networks to provide QoS (Quality of Service) guarantees. This dissertation focuses on broadband wireless networks, taking broadband wireless as the key, gives a thorough and comprehensive study on the wireless resource allocation algorithms, and aims to solve the problem of efficient, low-computational complexity resource allocation in broadband wireless networks. This dissertation gives a deep survey and study of classical radio resource allocation algorithms in international literatures, based on these works, this dissertation puts a particular effort on several efficient radio resource allocation models and the corresponding algorithms, which are analyzed and demonstrated deeply. The major work and contributions of this dissertation lie in several fields as follows,1．Capacity analysis of two-dimensional frequency-time scheduling in multiuser broadband OFDM systemBroadband OFDM and the multiple access techniques based on OFDM are widely regarded as one of the mostly interesting key technologies in B3G mobile communication systems. This dissertation proposes an adaptive two-dimensional frequency-time scheduling model in multiuser OFDM systems, based on which system capacity and spectral efficiency are thoroughly investigated and validated by numerous simulations. Through this analysis, it is shown that the two-dimensional scheduling achieves much higher system capacity and spectral efficiency than that of the conventional one-dimensional resource allocation, meanwhile users play an important role in system performance, and this is the so-called multiuser diversity gain which should be efficiently utilized to enhance system performance.2．Research of efficient radio resource allocation algorithms in OFDM systemsBased on the complete analysis of current research methods and the adaptive two-dimensional frequency-time scheduling model in multiuser OFDM systems, this dissertation proposes several efficient multiuser two-dimensional wireless resource allocation algorithms, namely, 2D-Best to Worst (2D-B2W) and 2D-Second Largest Rate Preferential (2D-SLRP), simulation analysis shows that these two algorithms achieve much higher system capacity and good fairness guarantees under a reasonable lower computational complexity.3．Space-time scheduling techniques in MIMO wireless communications systemThis dissertation mainly analyzes the system performance of MIMO transmit antenna selection system in multiuser point-to-multipoint (PMP) scenario, specifically, this dissertation focuses on the system performance from the whole system's perspective. First, a framework is proposed to analyze the three most important performance metrics, that is, outage probability, outage capacity and average symbol error rate; Then based on this framework model, we study the system effect of antenna gain, MIMO multiantenna configurations, multiuser diversity, etc. through theoretical derivations. The main contributions in this area are summarized as follows,? The closed-form formula and its asymptotic form of system outageprobability are derived, through which it is shown that the outage probability decreased by a factor ofγ^-KNtNr (hereγdenotes the average SNR);? The closed-form formula of outage capacity is derived, through which weshow that 1) outage capacity increases with the increases of mean value of sytem SNR, and decreases with the increase of the variance of system average SNR; 2) in order to obtain higher outage capacity, the number of transmit antenna should be no more than that of receive antennas.? A tight closed-form formula of system average symbol error rate and itscorresponding asymptotic form are derived through analysis, whichshowed that a diversity order of (KNtNr-KNt+1) can be obtained; and what'smore, when the number of receive antennas Nr is very large, a diversity orderequals to KNtNr can be extracted.Through the results from both theoretical analysis and simulations, it is shown that in multiuser MIMO antenna selection system, users can be regarded as "virtual" transmit antennas, which is the inherent source of multiuser diversity.4．Radio resource allocation in OFDM-MIMO systemsOFDM receives considerable interests due to its advantages in multipath fading channels; meanwhile MIMO achieves much higher spectral efficiency in strong scattering fading channels when multiple antennas are installed in both transmitter and receivers. In this case, the combining of OFDM and MIMO seems to be a must choice. This dissertation first introduces the characteristics and evolution of OFDM-MIMO-based long term evolution system, and proposes a complete series of simulation methodology suitable for MIMO-OFDM system. Based on OPNET Modeler, a system simulator is built to model such system. We have proposed several combining and MCS selection algorithms and radio resource scheduling algorithms. Based on these works, numerous simulations are performed for the OFDM-MIMO system.The research productions related to this dissertation are accepted as papers in IEEE journals and conferences.