IEEE 802.11ac uses DL MU-MIMO and channelization for very high throughput. We propose a new algorithm for adaptive channelization in DL MU-MIMO WLANs. The proposed scheme can enhance the throughput efficiency for DL MU-MIMO transmission by adaptively applying the channelization scheme according to data size and MCS. Moreover, our proposal can reduce the overhead due to the exchange of control frames for DL MU-MIMO transmission in WLANs. A performance evaluation shows that the proposed scheme is superior to IEEE 802.11ac WLAN.

This study proposes an integrated technology based on Proxy Mobile IPv6, which is a network-based protocol with mobility support, and a mobile content delivery network (CDN) that provides efficient content delivery management. The proposed architecture offers several benefits, such as the conservation of network resources because of reduced total traffic between hops and a reduced hop count.

We propose three operation modes, namely, DCF uplink, Downlink, and CTS uplink modes to solve the unfairness problem between uplink and downlink as well as improve the performance of delay and throughput. The proposed scheme only requires modifying AP's functionalities without any changes of STAs, and is fully backward compatible to the legacy DCF. Its analytical result is validated against simulation and performance evaluation shows the proposed scheme is superior to the traditional IEEE 802.11 WLAN.

In this letter, we present a method for improving the front-to-back ratio (FBR) of a broadcast antenna. The digitalization of terrestrial TV demands more efficient channel usage due to the reduction in TV bands after the switch-over. Thus, we designed an antenna with an FBR improved over -45 dB as compared to the -20 to -25 dB FBR range of existing antennas. We show experimentally that this antenna satisfies the required performance.

This paper proposes a QoS-aware differential processing control (QADPC) scheme for OpenFlow-based mobile networks. QADPC classifies the input packets to the control plane by considering end terminal mobility and service type. Then, different capacities are assigned to each classified packet for prioritized processing. By means of Markov chains, QADPC is evaluated in terms of blocking probability and waiting time in the control plane. Analytical results demonstrate that QADPC offers high priority packets both lower blocking probability and less waiting time.

We propose a mobility enhancement method in which APs periodically change their RF channels in a predetermined order that prevents overlap of neighboring APs' channels. Improvement in the throughput is also achieved by manipulating the DCF uplink mode and the Downlink mode. A performance evaluation shows that the proposed scheme is superior to IEEE 802.11 WLAN in handoff delay and throughput.

HTTP Distributed Denial of Service (DDoS) flooding attack aims to deplete the connection resources of a targeted web server by transmitting a massive amount of HTTP request packets using botnets. This type of attack seriously deteriorates the service quality of the web server by tying up its connection resources and uselessly holds up lots of network resources like link capacity and switching capability. This paper proposes a defense method for mitigating HTTP DDoS flooding attack based on software-defined networking (SDN). It is demonstrated in this paper that the proposed method can effectively defend the web server and preserve network resources against HTTP DDoS flooding attacks.

In this paper, we presented a new interference suppression method based on groupwise decorrelation for the multirate wideband-code division multiple access (W-CDMA) downlink. Code grouping in the proposed method is performed according to the correlation property between the mother code and the child code in the orthogonal variable spreading factor (OVSF) code tree. The decorrelation process based on the grouped codes, so called groupwise decorrelation, is then performed to suppress the interference induced in the downlink propagation. We demonstrate that the proposed method can enhance the performance significantly, with lower computational complexity and higher operational efficiency in which any information about interference users (code, data, amplitude) is not required to know in prior at the detection stage.

Femtocell is considered a promising solution for indoor service enhancement in IEEE 802.16e cellular systems. However, the scanning scheme of IEEE 802.16e is not suitable for direct use in scanning femtocells in terms of efficiency and scan duration. In this paper, we propose an efficient scanning scheme for femtocells in IEEE 802.16e systems. The proposed scheme can achieve a lower scanning overhead by reducing the number of femtocells needed to be scanned. Numerical results show that the proposed scanning scheme can reduce the control message overhead and the scan duration.

We propose an AP-based handoff management scheme in which each AP having multiple interfaces communicates with MSs by turns, prohibiting from using the same channel as neighboring APs at the same time to avoid interference. In the proposed scheme, APs support handoff management to accomplish MS-unaware handoff. Performance evaluation shows that the proposed scheme can not only achieve low handoff delay, but enhance throughput performance.

In this paper, we propose a PON-based access network based on conventional TDM-PON architecture for the smooth, economical and effective transition to the future optical access network. We also propose a dynamic MAC protocol for wavelength channel and bandwidth allocation in the TDM-PON subscriber networks, which can provide enhanced network scalability and flexibility, and greater adaptability to the increasing number of subscribers in TDM-PON. In the proposed dynamic MAC protocol, several key functions are manifested, such as multiple wavelength channel utilization and dynamic allocation of multiple time-slots to a user depending on SLA between OLT and ONUs to meet QoS requirements. A dedicated control channel is used for delivering the request and status information between OLT and ONUs. We evaluate the performances of the proposed MAC protocol thru a statistical queuing analysis and numerical simulations. In addition, through simulations using various traffic models we verify the superior performance of the proposed approach by comparing it with conventional TDM-PONs.

This letter proposes a compensation method that can alleviate the problem of I/Q mismatch generated in the direct-conversion receiver of OFDM systems. In the proposed method, the amount of I/Q mismatch is estimated using null-carriers in transmitted signals, and it is subtracted from received symbols to suppress I/Q mismatch effects. Simulations show experiments that the proposed method can effectively eliminate the I/Q mismatch effects.