A Study on Radio Resource Management for LTE-WLAN Aggregation

• Main Authors: Shih, Ying-Ju, 施盈如
• Other Authors: Lin, Yi-Bing
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/c5st98

博士 === 國立交通大學 === 資訊科學與工程研究所 === 107 === Mobile data traffic has been dramatically increased and unlicensed spectrum is utilized to open up additional capacity to support LTE service. LTE-WLAN aggregation (LWA) combines the radio resources of LTE and WLAN, which is a perfect solution that satisfies this need. The radio resource management (RRM) administrates LTE and WLAN radio resources in the LWA system and allocates resources to a User Equipment (UE) for data transfer. To fully explore LWA capacity, the RRM also dynamically adapts the transmission rate based on the channel quality during data transfer. In this dissertation, we investigate the radio resource management for LTE-WLAN aggregation. Two types of policies can be exercised at the eNB (LTE base station) to transfer packets: the switched LWA policy and the split LWA policy. In the switched LWA policy, the packets are delivered through either LTE or Wi-Fi. In this mechanism, it is essential that the network should intelligently switch a Data Radio Bearer (DRB) to utilize either LTE or Wi-Fi. In this dissertation, we first implement the RRM layer for LWA and then propose two types of the switched LWA policies: the guaranteed bandwidth and the equal sharing policies. We measure the delay times of the LWA procedures and evaluates the performance of the switched LWA policies. Our study indicates that switched LWA can be implemented at the RRM with negligible overhead and effectively reduce the blocking probability of the LWA’s DRBs. The beauty of the LWA policies is that the DRBs’ blocking probability is not affected by the DRB holding time distribution. Contrary to the switched LWA policy, packets can be delivered through both radio resources in the split LWA policy. In this mechanism, it is important to determine the ratio of packets delivered by LTE over WLAN for transmission rate adaption. To provide appropriate WLAN transmission bandwidth, the UE periodically measures the WLAN quality and reports the results to the eNB. The eNB then decides if the transmission rate should be adapted. We investigate the performance of periodical reporting and then propose the enhanced event-triggered reporting to improve the performance of WLAN transmission rate adaption. We suggest how to select appropriate frequency to minimize the network traffic of periodical reporting. We also show that enhanced event-triggered reporting outperforms periodical reporting. Our solution utilizes the standard 3GPP protocols and does not modify the mobile phone’s software.